AU2011265413A1 - Human Anti-OPGL Neutralizing Antibodies as Selective OPGL, Pathway Inhibitors - Google Patents

Abstract

Abstract Monoclonal antibodies and hybridomas producing them that interact with osteoprotegerin ligand (OPGL) are provided. Methods of treating osteopenic disorders by administering a pharmaceutically effective amount of antibodies to 5 OPGL are also provided. Methods of detecting the amount of OPGL in a sample using antibodies to OPGL are further provided.

Description

I'/UIUIl -I 40ID/VWI Regulation 3.2 AUSTRALIA Patents Act 1990 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Name of Applicants: Amgen Inc. One Amgen Center Drive Thousand Oaks California 91320-1799 United States of America Medarex, Inc. 707 State Road Princeton New Jersey 08540 United States of America Actual Inventors William James Boyle John Kevin Sullivan Eugene Medlock Robin L Elliott Frank Martin Haichun Huang Address for service is: WRAYS Ground Floor, 56 Ord Street West Perth WA 6005 Attorney code: WR Invention Title: Human Anti-OPGL Neutralizing Antibodies as Selective OPGL, Pathway Inhibitors The following statement is a full description of this invention, including the best method of performing it known to me: 1/1 WO 03/086289 PCT/US03/10749 Human Anti-OPGL Neutralizing Antibodies As Selective OPGL Pathway Inhibitors This application is related to U.S. provisional application Serial No. 60/370,407, filed April 5, 2002. 5 FIELD OF THE INVENTION The invention relates to antibodies that bind osteoprotegerin ligand (OPGL). Compositions and methods for the treatment of bone diseases, such as osteoporosis, bone loss from arthritis, Paget's disease, and osteopenia, are also provided. 10 BACKGROUND OF THE INVENTION Living bone tissue exhibits a dynamic equilibrium between formation of bone, known as deposition, and breakdown of bone, known as resorption. These processes can be mediated by at least two cell types: osteoblasts, which secrete molecules that comprise 15 the organic matrix of bone (deposition); and osteoclasts, which promote dissolution of the bone matrix and solubilization of bone salts (resorption). In certain individuals, such as post-menopausal women, the rate of resorption can exceed the rate of deposition, which may result in reduced bone mass and strength, increased risk of fractures, and slow or incomplete repair of broken bones. 20 Osteoprotegerin ligand (OPGL) is a member of the TNF family of cytokines and promotes formation of osteoclasts through binding to the receptor activator of NF-KB (RANK, also called osteoclast differentiation and activation receptor, or ODAR). Osteoprotegerin (OPG), on the other hand, inhibits the formation of osteoclasts by sequestering OPGL and preventing OPGL association with ODAR. Thus, the amount of 25 OPGL associated with ODAR correlates with the equilibrium between bone deposition and resorption. Individuals who suffer from osteopenic diseases, such as osteoporosis, show a greater rate of bone resorption than deposition, which may result from increased levels or activity of OPGL. Thus, it would be useful to have molecules that can regulate the activity of OPGL in osteoclastogenesis. It would also be useful to be able to detect WO 03/086289 PCT/US03/10749 the amount of OPGL in a biological sample, such as a blood sample, to diagnose an osteopenic disorder relating to increased levels of OPGL. SUMMARY OF THE INVENTION 5 The invention provides monoclonal antibodies that bind to osteoprotegerin ligand (OPGL). Preferably, the antibodies inhibit binding of OPGL to an osteoclast differentiation and activation receptor (ODAR). Also provided by this invention are hybridoma cell lines that produce, and most preferably, secrete into cell culture media the monoclonal antibodies of the invention. The antibodies of the invention are useful for 10 treating various disorders associated with low bone density. In certain aspects, the invention provides antibodies, preferably monoclonal antibodies, most preferably human antibodies, comprising a heavy chain and a light chain, wherein the heavy chain comprises an IgG 1 , IgG 2 , or an IgG 4 heavy chain constant region. Preferably, an antibody of the invention comprises an amino acid sequence of the 15 IgG heavy chain constant region as set forth in SEQ ID NO: 2 or an antigen-binding or an immunologically functional immunoglobulin fragment thereof. The invention also provides antibodies, preferably monoclonal antibodies, most preferably human antibodies, comprising a heavy chain and a light chain, wherein the light chain comprises an amino acid sequence as set forth in SEQ ID NO: 4 or an antigen 20 binding or an immunologically functional immunoglobulin fragment thereof. The invention relates specifically to human antibodies, most preferably monoclonal antibodies that specifically bind the D-E loop region of OPGL. The invention also relates to human antibodies, preferably monoclonal antibodies, that bind to a region of osteoprotegerin ligand (OPGL) that is outside the D-E loop region. In 25 addition, the invention relates to human antibodies, preferably monoclonal antibodies, that bind to both a region of OPGL that is outside the D-E loop region and all or a portion of the D-E loop region. In one aspect, antibodies of the invention bind to a first region of OPGL that is outside the D-E loop region and then, while remaining bound to the first region, bind to a second region that is all or a portion of the D-E loop region. Such 30 binding is referred to herein as consecutive. In another aspect, antibodies of the invention can bind to a first region of OPGL that is outside the D-E loop region and a second region 2 WO 03/086289 PCT/US03/10749 that is all or a portion of the D-E loop region at the same time. Such binding is referred to herein as simultaneous. In certain aspects, antibodies of the invention comprise a heavy chain and a light chain, wherein the variable region of the heavy chain comprises an amino acid sequence 5 as set forth in any of SEQ ID NO: 6, SEQ ID NO: 14, SEQ ID NO: 22, or SEQ ID NO: 26, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof. In other aspects, the light chain variable region comprises an amino acid sequence as set forth in any of SEQ ID NO: 8, SEQ ID NO: 16, SEQ ID NO: 24, or SEQ ID NO: 28, or an antigen-binding or an immunologically functional immunoglobulin 10 fragment thereof. In additional aspects, the heavy chain comprises an amino acid sequence as set forth in any of SEQ ID NO: 30, SEQ ID NO: 38, SEQ ID NO: 46, or SEQ ID NO: 50, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof. In still further aspects, the light chain comprises an amino acid sequence as set forth in any of SEQ ID NO: 32, SEQ ID NO: 40, SEQ ID NO: 48, or SEQ 15 ID NO: 52, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof. The invention also provides antibodies that bind specifically to OPGL, wherein the heavy chain comprises a heavy chain variable region as set forth in SEQ ID NO: 6, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof, 20 and the light chain comprises a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 8, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof. In certain aspects, the invention provides antibodies, comprising a heavy chain and a light chain, (a) wherein the heavy chain comprises a first variable region, and 25 wherein the first variable region comprises a sequence that has at least 90% identity to the amino acid sequence set forth in SEQ ID NO: 6, and (b) wherein the light chain comprises a second variable region, and wherein the second variable region comprises a sequence that has at least 90% identity to the amino acid sequence set forth in SEQ ID NO: 8, and (c) wherein the antibody interacts with OPGL. 30 In other aspects, the first variable region comprises a sequence that has at least 95% identity to the amino acid sequence set forth in SEQ ID NO: 6, and the second 3 WO 03/086289 PCT/US03/10749 variable region comprises a sequence that has at least 95% identity to the amino acid sequence set forth in SEQ ID NO: 8. In still other aspects, the first variable region comprises a sequence that has at least 99% identity to the amino acid sequence set forth in SEQ ID NO: 6, and the second 5 variable region comprises a sequence that has at least 99% identity to the amino acid sequence set forth in SEQ ID NO: 8. The invention further provides antibodies that bind specifically to OPGL, wherein the heavy chain comprises a heavy chain variable region as set forth in SEQ ID NO: 14, or an antigen-binding or an immunologically functional immunoglobulin fragment 10 thereof, and the light chain comprises a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 16, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof. In certain aspects, the invention provides antibodies, comprising a heavy chain and a light chain, (a) wherein the heavy chain comprises a first variable region, and 15. wherein the first variable region comprises a sequence that has at least 90% identity to the amino acid sequence set forth in SEQ ID NO: 14, and (b) wherein the light chain comprises a second variable region, and wherein the second variable region comprises a sequence that has at least 90% identity to the amino acid sequence set forth in SEQ ID NO: 16, and (c) wherein the antibody interacts with OPGL. 20 In other aspects, the first variable region comprises a sequence that has at least 95% identity to the amino acid sequence set forth in SEQ ID NO: 14, and the second variable region comprises a sequence that has at least 95% identity to the amino acid sequence set forth in SEQ ID NO: 16. In further aspects, the first variable region comprises a sequence that has at least 25 99% identity to the amino acid sequence set forth in SEQ ID NO: 14, and the second variable region comprises a sequence that has at least 99% identity to the amino acid sequence set forth in SEQ ID NO: 16. The invention provides antibodies that bind specifically to OPGL, wherein the heavy chain comprises a heavy chain variable region as set forth in SEQ ID NO: 22, or an 30 antigen-binding or an immunologically functional immunoglobulin fragment thereof, and the light chain comprises a light chain variable region comprising an amino acid sequence 4 WO 03/086289 PCT/US03/10749 as set forth in SEQ ID NO: 24, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof. In certain aspects, the invention provides antibodies, comprising a heavy chain and a light chain, (a) wherein the heavy chain comprises a first variable region, and 5 wherein the first variable region comprises a sequence that has at least 90% identity to the amino acid sequence set forth in SEQ ID NO: 22, and (b) wherein the light chain comprises a second variable region, and wherein the second variable region comprises a sequence that has at least 90% identity to the amino acid sequence set forth in SEQ ID NO: 24, and (c) wherein the antibody interacts with OPGL. 10 In particular aspects, the first variable region comprises a sequence that has at least 95% identity to the amino acid sequence set forth in SEQ ID NO: 22, and the second variable region comprises a sequence that has at least 95% identity to the amino acid sequence set forth in SEQ ID NO: 24. In further aspects, the first variable region comprises a sequence that has at least 15 99% identity to the amino acid sequence set forth in SEQ ID NO: 22, and the second variable region comprises a sequence that has at least 99% identity to the amino acid sequence set forth in SEQ ID NO: 24. In addition, the invention provides antibodies that bind specifically to the D-E loop region of OPGL, wherein the heavy chain comprises a heavy chain variable region 20 as set forth in SEQ ID NO: 26, or an antigen-binding or an immunologically functional immnunoglobulin fragment thereof, and the light chain comprises a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 28, or an antigen binding or an immunologically functional immunoglobulin fragment thereof. In certain aspects, the invention provides antibodies, comprising a heavy chain 25 and a light chain, (a) wherein the heavy chain comprises a first variable region, and wherein the first variable region comprises a sequence that has at least 90% identity to the amino acid sequence set forth in SEQ ID NO: 26, and (b) wherein the light chain comprises a second variable region, and wherein the second variable region comprises a sequence that has at least 90% identity to the amino acid sequence set forth in SEQ ID 30 NO: 28, and (c) wherein the antibody interacts with OPGL. 5 WO 03/086289 PCT/US03/10749 In other aspects, the first variable region comprises a sequence that has at least 95% identity to the amino acid sequence set forth in SEQ ID NO: 26, and the second variable region comprises a sequence that has at least 95% identity to the amino acid sequence set forth in SEQ ID NO: 28. 5 In additional aspects, the first variable region comprises a sequence that has at least 99% identity to the amino acid sequence set forth in SEQ ID NO: 26, and the second variable region comprises a sequence that has at least 99% identity to the amino acid sequence set forth in SEQ ID NO: 28. The invention also provides antibodies that bind specifically to OPGL, wherein 10 the heavy chain comprises an amino acid sequence as set forth in SEQ ID NO: 30, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof, and the light chain comprises an amino acid sequence as set forth in SEQ ID NO: 32, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof. The invention also provides antibodies that bind specifically to OPGL, wherein 15 the heavy chain comprises an amino acid sequence as set forth in SEQ ID NO: 38, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof, and the light chain comprises a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 40, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof. 20 The invention provides antibodies that bind specifically to OPGL, wherein the heavy chain comprises an amino acid sequence as set forth in SEQ ID NO: 46, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof, and the light chain comprises a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 48, or an antigen-binding or an immunologically functional 25 immunoglobulin fragment thereof. The invention provides antibodies that bind specifically to OPGL, wherein the heavy chain comprises an amino acid sequence as set forth in SEQ ID NO: 50, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof, and the light chain comprises a light chain variable region comprising an amino acid sequence 30 as set forth in SEQ ID NO: 52, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof. 6 WO 03/086289 PCT/US03/10749 In certain aspects, the invention provides antibodies that specifically bind OPGL and comprises a heavy chain and a light chain, wherein the heavy chain variable region comprises an amino acid sequence as set forth in SEQ ID NO: 10 or SEQ I) NO: 18, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof. 5 In other aspects, the light chain variable region comprises an amino acid sequence as set forth in SEQ ID NO: 12 or SEQ ID NO: 20, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof The invention also provides antibodies that specifically bind OPGL, wherein the heavy chain variable region comprises an amino acid sequence as set forth in SEQ ID 10 NO: 34 or SEQ ID NO: 42, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof. In other aspects, the light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 36 or SEQ ID NO: 44, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof. The invention further provides antibodies that specifically bind OPGL, wherein 15 the heavy chain comprises a heavy chain variable region as set forth in SEQ ID NO: 10, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof, and the light chain comprises a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 12, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof. 20 In certain aspects, the invention provides antibodies, comprising a heavy chain and a light chain, (a) wherein the heavy chain comprises a first variable region, and wherein the first variable region comprises a sequence that has at least 90% identity to the amino acid sequence set forth in SEQ ID NO: 10, and (b) wherein the light chain comprises a second variable region, and wherein the second variable region comprises a 25 sequence that has at least 90% identity to the amino acid sequence set forth in SEQ ID NO: 12, and (c) wherein the antibody interacts with OPGL. In further aspects, the first variable region comprises a sequence that has at least 95% identity to the amino acid sequence set forth in SEQ ID NO: 10, and the second variable region comprises a sequence that has at least 95% identity to the amino acid 30 sequence set forth in SEQ ID NO: 12. 7 WO 03/086289 PCT/US03/10749 In other aspects, the first variable region comprises a sequence that has at least 99% identity to the amino acid sequence set forth in SEQ ID NO: 10, and the second variable region comprises a sequence that has at least 99% identity to the amino acid sequence set forth in SEQ ID NO: 12. 5 The invention also provides antibodies that specifically bind, wherein the heavy chain comprises a heavy chain variable region as set forth in SEQ ID NO: 18, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof, and the light chain comprises a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 20, or an antigen-binding or an immunologically functional 10 immunoglobulin fragment thereof. In certain aspects, the invention provides antibodies, comprising a heavy chain and a light chain, (a) wherein the heavy chain comprises a first variable region, and wherein the first variable region comprises a sequence that has at least 90% identity to the amino acid sequence set forth in SEQ ID NO: 18, and (b) wherein the light chain 15 comprises a second variable region, and wherein the second variable region comprises a sequence that has at least 90% identity to the amino acid sequence set forth in SEQ ID NO: 20, and (c) wherein the antibody interacts with OPGL. In other aspects, the first variable region comprises a sequence that has at least 95% identity to the amino acid sequence set forth in SEQ ID NO: 18, and the second 20 variable region comprises a sequence that has at least 95% identity to the amino acid sequence set forth in SEQ ID NO: 20. In still other aspects, the first variable region comprises a sequence that has at least 99% identity to the amino acid sequence set forth in SEQ ID NO: 18, and the second variable region comprises a sequence that has at least 99% identity to the amino acid 25 sequence set forth in SEQ ID NO: 20. The invention also provides antibodies that specifically bind OPGL, wherein the heavy chain comprises an amino acid sequence as set forth in SEQ ID NO: 34, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof, and the light chain comprises a light chain variable region comprising an amino acid sequence 30 as set forth in SEQ ID NO: 36, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof. 8 WO 03/086289 PCT/US03/10749 The invention provides antibodies that specifically bind OPGL, wherein the heavy chain comprises an amino acid sequence as set forth in SEQ ID NO: 42, or an antigen binding or an immunologically functional immunoglobulin fragment thereof, and the light chain comprises a light chain variable region comprising an amino acid sequence as set 5 forth in SEQ IM NO: 44, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof. The invention also provides single chain antibodies, single chain Fv antibodies, Fab antibodies, Fab' antibodies, and (Fab') 2 . In particular aspects, the invention provides a heavy chain comprising a variable 10 region and a constant region, wherein the variable region comprises an amino acid sequence as set forth in any of SEQ ID NO: 6, SEQ ID NO: 10, SEQ ID NO: 14, SEQ ID NO: 18, SEQ ID NO: 22, or SEQ ID NO: 26, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof. In addition, the invention also provides a heavy chain comprising an amino acid 15 sequence as set forth in any of SEQ ID NO: 30, SEQ ID NO: 34, SEQ ID NO: 38, SEQ ID NO: 42, SEQ ID NO: 46, or SEQ ID NO: 50, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof. In certain aspects, the invention provides a light chain comprising a variable region and a constant region, wherein the variable region comprises an amino acid 20 sequence as set forth in any of SEQ ID NO: 8, SEQ ID NO: 12, SEQ ID NO: 16, SEQ ID NO: 20, SEQ ID NO: 24, or SEQ ID NO: 28, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof. In other aspects, the invention provides a light chain comprising an amino acid sequence as set forth in any of SEQ ID NO: 32, SEQ ID NO: 36, SEQ ID NO: 40, SEQ 25 ID NO: 44, SEQ ID NO: 48, or SEQ ID NO: 52, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof. The invention also relates to isolated human antibodies that specifically bind OPGL, wherein the antibody comprises: (a) human heavy chain framework regions, a human heavy chain CDR1 region, a human heavy chain CDR2 region, and a human 30 heavy chain CDR3 region; and (b) human light chain framework regions, a human light chain CDRl region, a human light chain CDR2 region, and a human light chain CDR3 9 WO 03/086289 PCT/US03/10749 region. In certain aspects, the human heavy chain CDR1 region can be the heavy chain CDRI region of 16E1, 2D8, 22B3, or 9H7 as shown in Figure 15 and the human light chain CDR1 region can be the light chain CDRI region of 16E1, 2D8, 22B3, or 9H7 as shown in Figure 16. In other aspects, the human heavy chain CDR2 region can be the 5 heavy chain CDR2 region of 16E1, 2D8, 22B3, or 9H7 as shown in Figurel5 and the human light chain CDR2 region can be the light chain CDR2 region of 16E1, 2D8, 22B3, or 9H7 as shown in Figure 16. In still other aspects, the human heavy chain CDR3 region is the heavy chain CDR3 region of 16E1, 2D8, 22B3, or 9H7 as shown in Figure 15, and the human light chain CDR3 region is the light chain CDR3 region of 16E1, 2D8, 22B3, 10 or 9H7 as shown in Figure 16. The invention also relates to isolated human antibodies that specifically bind OPGL, wherein the antibody comprises: (a) human heavy chain framework regions, a human heavy chain CDR1 region, a human heavy chain CDR2 region, and a human heavy chain CDR3 region; and (b) human light chain framework regions, a human light 15 chain CDRI region, a human light chain CDR2 region, and a human light chain CDR3 region. In certain aspects, the human heavy chain CDR1 region can be the heavy chain CDR1 region of 2E11 or 18B2 as shown in Figure 15 and the human light chain CDR1 region can be the light chain CDR1 region of 2E11 or 18B2 as shown in Figure 16. In other aspects, the human heavy chain CDR2 region can be the heavy chain CDR2 region 20 of 2E 11 or 18B2 as shown in Figurel5 and the human light chain CDR2 region can be the light chain CDR2 region of 2E11 or 18B2 as shown in Figure 16. In still other aspects, the human heavy chain CDR3 region is the heavy chain CDR3 region of 2E1 1 or 18B2 as shown in Figure 15, and the human light chain CDR3 region is the light chain CDR3 region of 2E11 or 18B2 as shown in Figure 16. 25 In addition, the invention provides methods for treating an osteopenic disorder, comprising the step of administering a pharmaceutically effective amount of a monoclonal antibody of the invention or antigen-binding fragment thereof to an individual in need thereof. The invention further relates to fusion proteins and other molecules capable of 30 binding to a region of osteoprotegerin ligand (OPGL) that is outside the D-E loop region, or both a region of OPGL that is outside the D-E loop region and all or a portion of the D E loop region, wherein binding is consecutive or simultaneous (together with the 10 WO 03/086289 PCTIUS03/10749 aformentioned antibodies, collectively referred to herein as "specific binding partners"), such as may be prepared using methods as described, for example, in WO 00/24782, which is incorporated by reference. Such molecules can be expressed, for example, in mammalian cells (e.g. Chinese Hamster Ovary cells) or bacterial cells (e.g. E. coli cells). 5 The invention also provides methods for detecting the level of OPGL in a biological sample, comprising the step of contacting the sample with a monoclonal antibody of the invention or antigen-binding fragment thereof. The anti-OPGL antibodies of the invention may be employed in any known assay method, such as competitive binding assays, direct and indirect sandwich assays, immunoprecipitation assays and 10 enzyme-linked immunosorbent assays (ELISA) (See, Sola, 1987, Monoclonal Antibodies: A Manual of Techniques, pp. 147-158, CRC Press, Inc.) for the detection and quantitation of OPGL. The antibodies can bind OPGL with an affinity that is appropriate for the assay method being employed. Specific preferred embodiments of the present invention will become evident from 15 the following more detailed description of certain preferred embodiments and the claims. BRIEF DESCRIPTION OF THE FIGURES Figures 1A-1B depict a cDNA sequence (Figure 1A) encoding the anti-OPGL antibody heavy chain constant region (SEQ ID NO: 1) and the amino acid sequence 20 (Figure 1B) of the anti-OPGL antibody heavy chain constant region (SEQ ID NO: 2). Figures 2A-2B depict a cDNA sequence (Figure 2A) encoding the anti-OPGL antibody kappa chain constant region (SEQ ID NO: 3) and the amino acid sequence (Figure 2B) of the anti-OPGL antibody kappa chain constant region (SEQ ID NO: 4). Figures 3A-3B depict a cDNA sequence (Figure 3A) encoding the 22B3 anti 25 OPGL antibody heavy chain variable region (SEQ ID NO: 5) and the amino acid sequence (Figure 3B) of the 22B3 anti-OPGL antibody heavy chain variable region (SEQ ID NO: 6). Figures 4A-4B depict a cDNA sequence (Figure 4A) encoding the 22B3 anti OPGL antibody kappa chain variable region (SEQ ID NO: 7) and the amino acid 11 WO 03/086289 PCT/US03/10749 sequence (Figure 4B) of the 22B3 anti-OPGL antibody kappa chain variable region (SEQ ID NO: 8). Figures 5A-5B depict a cDNA sequence (Figure 5A) encoding the 2E11 anti OPGL antibody heavy chain variable region (SEQ ID NO: 9) and the amino acid 5 sequence (Figure 5B) of the 2E1 1 anti-OPGL antibody heavy chain variable region (SEQ ID NO: 10). Figures 6A-6B depict a cDNA sequence (Figure 6A) encoding the 2E1 1 anti OPGL antibody kappa chain variable region (SEQ ID NO: 11) and the amino acid sequence (Figure 6B) of the 2E 11 anti-OPGL antibody kappa chain variable region (SEQ 10 ID NO: 12). Figures 7A-7B depict a cDNA sequence (Figure 7A) encoding the 2D8 anti OPGL antibody heavy chain variable region (SEQ ID NO: 13) and the amino acid sequence (Figure 7B) of the 2D8 anti-OPGL antibody heavy chain variable region (SEQ ID NO: 14). 15 Figures 8A-8B depict a cDNA sequence (Figure 8A) encoding the 2D8 anti OPGL antibody kappa chain variable region (SEQ ID NO: 15) and the amino acid sequence (Figure 8B) of the 2D8 anti-OPGL antibody kappa chain variable region (SEQ ID NO: 16). Figures 9A-9B depict a cDNA sequence (Figure 9A) encoding the 18B2 anti 20 OPGL antibody heavy chain variable region (SEQ ID NO: 17) and the amino acid sequence (Figure 9B) of the 18B2 anti-OPGL antibody heavy chain variable region (SEQ ID NO: 18). Figures 10A-10B depict a cDNA sequence (Figure 10A) encoding the 18B2 anti OPGL antibody kappa chain variable region (SEQ ID NO: 19) and the amino acid 25 sequence (Figure 10B) of the 18B2 anti-OPGL antibody kappa chain variable region (SEQ ID NO: 20). Figures 1 1A-11 B depict a cDNA sequence (Figure 1 1A) encoding the 16E1 anti OPGL antibody heavy chain variable region (SEQ ID NO: 21) and the amino acid sequence (Figure 1 IB) of the 16E1 anti-OPGL antibody heavy chain variable region 30 (SEQ ID NO: 22). 12 WO 03/086289 PCT/US03/10749 Figures 12A-12B depict a cDNA sequence (Figure 12A) encoding the 16E1 anti OPGL antibody kappa chain variable region (SEQ ID NO: 23) and the amino acid sequence (Figure 12B) of the 16E1 anti-OPGL antibody kappa chain variable region (SEQ ID NO: 24). 5 Figures 13A-13B depict a cDNA sequence (Figure 13A) encoding the 9H7 anti OPGL antibody heavy chain variable region (SEQ ID NO: 25) and the amino acid sequence (Figure 13B) of the 9H7 anti-OPGL antibody heavy chain variable region (SEQ ID NO: 26). Figures 14A-14B depict a cDNA sequence (Figure 14A) encoding the 9H7 anti 10 OPGL antibody kappa chain variable region (SEQ ID NO: 27) and the amino acid sequence (Figure 14B) of the 9H7 anti-OPGL antibody kappa chain variable region (SEQ ID NO: 28). Figure 15 depicts the heavy chain alignment for anti-OPGL antibodies designated 16E1, 2E11, 18B2, 2D8, 22B3, and 9H7. CDRs are underlined, non-consensus amino 15 acids are shaded and in bold type. Figure 16 depicts the light chain alignment for anti-OPGL antibodies designated 16E1, 2E11, 18B2, 2D8, 22B3, and 9H7. CDRs are underlined, non-consensus amino acids are shaded and in bold type. Figure 17 depicts a circular plasmid map of the pDSRa19:9H7 kappa chain 20 expression vector. Figure 18 shows a circular plasmid map of the pDSRc19:9H7 heavy chain expression vector. Figure 19 depicts an exemplary cell culture process for producing anti-OPGL antibody. 25 Figure 20 is a graph showing optical density versus anti-OPGL antibody concentration demonstrating OPGL antibody mediated inhibition of osteoclast formation. Figure 21 depicts graphs of serum concentrations of anti-OPGL antibodies following subcutaneous administration at 1.0 mg/kg in Cynomolgus monkeys. 13 WO 03/086289 PCT/US03/10749 Figure 22 depicts graphs representing the percentage change in serum NTx from baseline following subcutaneous administration at 1.0 mg/kg of anti-OPGL antibodies in Cynomolgus monkeys. Figure 23 shows a comparison of murine (SEQ ID NO: 70), human (SEQ ID NO: 5 71), and murine DE variant (SEQ ID NO: 72) amino acid sequences in a region of OPGL between the D and E regions. Figure 24 depicts the results of an enzyme immunoassay showing six anti-OPGL antibodies of the invention binding murine OPGL (143-317). Figure 25 depicts the results of an enzyme immunoassay showing four of the anti 10 OPGL antibodies of the invention bind FLAG-murine OPGL/DE (158-316). DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described. All references cited in this 15 application are expressly incorporated by reference herein for any purpose. Definitions Standard techniques were used for recombinant DNA, oligonucleotide synthesis, and tissue culture and transformation (e.g., electroporation, lipofection). Enzymatic reactions and purification techniques were performed according to manufacturer's 20 specifications or as commonly accomplished in the art or as described herein. The foregoing techniques and procedures were generally performed according to conventional methods well known in the art and as described in various general and more specific references that are cited and discussed throughout the present specification. See e.g., Sambrook et al., 2001, MOLECULAR CLONING: A LABORATORY MANUAL, 3d ed., Cold 25 Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., which is incorporated herein by reference for any purpose. Unless specific definitions are provided, the nomenclature utilized in connection with, and the laboratory procedures and techniques of, analytical chemistry, synthetic organic chemistry, and medicinal and pharmaceutical chemistry described herein are those well known and commonly used in the art. Standard 14 WO 03/086289 PCT/US03/10749 techniques can be used for chemical syntheses, chemical analyses, pharmaceutical preparation, formulation, and delivery, and treatment of patients. As utilized in accordance with the present disclosure, the following terms, unless otherwise indicated, shall be understood to have the following meanings: 5 The term "isolated polynucleotide" as used herein means a polynucleotide of genomic, cDNA, or synthetic origin or some combination thereof, which by virtue of its origin the isolated polynucleotide (1) is not associated with all or a portion of a polynucleotide in which the isolated polynucleotide is found in nature, (2) is linked to a polynucleotide which it is not linked to in nature, or (3) does not occur in nature as part of 10 a larger sequence. The term "isolated protein" referred to herein means that a subject protein (1) is free of at least some other proteins with which it would normally be found, (2) is essentially free of other proteins from the same source, e.g., from the same species, (3) is expressed by a cell from a different species, (4) has been separated from at least about 50 15 percent of polynucleotides, lipids, carbohydrates, or other materials with which it is associated in nature, (5) is not associated (by covalent or noncovalent interaction) with portions of a protein with which the "isolated protein" is associated in nature, (6) is operably associated (by covalent or noncovalent interaction) with a polypeptide with which it is not associated in nature, or (7) does not occur in nature. Such an isolated 20 protein can be encoded by genomic DNA, cDNA, mRNA or other RNA, of synthetic origin, or any combination thereof. Preferably, the isolated protein is substantially free from proteins or polypeptides or other contaminants that are found in its natural environment that would interfere with its use (therapeutic, diagnostic, prophylactic, research or otherwise). 25 The terms "polypeptide" or "protein" means molecules having the sequence of native proteins, that is, proteins produced by naturally-occurring and specifically non recombinant cells, or genetically-engineered or recombinant cells, and comprise molecules having the amino acid sequence of the native protein, or molecules having deletions from, additions to, and/or substitutions of one or more amino acids of the native 30 sequence. The terms "polypeptide" and "protein" specifically encompass anti-OPGL antibodies, or sequences that have deletions from, additions to, and/or substitutions of one or more amino acid of an anti-OPGL antibody. 15 WO 03/086289 PCT/US03/10749 The term "polypeptide fragment" refers to a polypeptide that has an amino terminal deletion, a carboxyl-terminal deletion, and/or an internal deletion. In certain embodiments, fragments are at least 5 to about 500 amino acids long. It will be appreciated that in certain embodiments, fragments are at least 5, 6, 8, 10, 14, 20, 50, 70, 5 100, 110, 150, 200, 250, 300, 350, 400, or 450 amino acids long. Particularly useful polypeptide fragments include functional domains, including binding domains. In the case of an anti-OPGL antibody, useful fragments include but are not limited to a CDR region, a variable domain of a heavy or light chain, a portion of an antibody chain or just its variable region including two CDRs, and the like. 10 The term "immunologically functional immunoglobulin fragment" as used herein refers to a polypeptide fragment that contains at least the CDRs of the immunoglobulin heavy and light chains. An immunologically functional immunoglobulin fragment of the invention is capable of binding to an antigen. In preferred embodiments, the antigen is a ligand that specifically binds to a receptor. In these embodiments, binding of an 15 immunologically functional immunoglobulin fragment of the invention prevents binding of the ligand to its receptor, interrupting the biological response resulting from ligand binding to the receptor. Preferably, an immunologically functional immunoglobulin fragment of the invention binds specifically to OPGL. Most preferably, the fragment binds specifically to human OPGL. 20 The term "naturally-occurring" as used herein and applied to an object refers to the fact that the object can be found in nature. For example, a polypeptide or polynucleotide sequence that is present in an organism (including viruses) that can be isolated from a source in nature and that has not been intentionally modified by man is naturally occurring. 25 The term "operably linked" means that the components to which the term is applied are in a relationship that allows them to carry out their inherent functions under suitable conditions. For example, a control sequence "operably linked" to a coding sequence is ligated thereto so that expression of the protein coding sequence is achieved under conditions compatible with the transcriptional activity of the control sequences. 30 The term "control sequence" as used herein refers to polynucleotide sequences that can effect expression, processing or intracellular localization of coding sequences to which they are ligated. The nature of such control sequences may differ depending upon 16 WO 03/086289 PCT/US03/10749 the host organism. In particular embodiments, control sequences for prokaryotes may include promoter, ribosomal binding site, and transcription termination sequence. In other particular embodiments, control sequences for eukaryotes may include promoters comprising one or a plurality of recognition sites for transcription factors, transcription 5 enhancer sequences, transcription termination sequences and polyadenylation sequences. In certain embodiments, "control sequences" can include leader sequences and/or fusion partner sequences. The term "polynucleotide" as referred to herein means single-stranded or double stranded nucleic acid polymers of at least 10 bases in length. In certain embodiments, the 10 nucleotides comprising the polynucleotide can be ribonucleotides or deoxyribonucleotides or a modified form of either type of nucleotide. Said modifications include base modifications such as bromuridine, ribose modifications such as arabinoside and 2',3'-dideoxyribose and internucleotide linkage modifications such as phosphorothioate, phosphorodithioate, phosphoroselenoate, phosphorodiselenoate, 15 phosphoroanilothioate, phoshoraniladate and phosphoroamidate. The term "polynucleotide" specifically includes single and double stranded forms of DNA. The term "oligonucleotide" as used herein includes naturally occurring, and modified nucleotides linked together by naturally occurring, and/or non-naturally occurring oligonucleotide linkages. Oligonucleotides are a polynucleotide subset 20 comprising members that are generally single-stranded and have a length of 200 bases or fewer. In certain embodiments, oligonucleotides are 10 to 60 nucleotides in length. In certain embodiments, oligonucleotides are 12, 13, 14, 15, 16, 17, 18, 19, or 20 to 40 nucleotides in length. Oligonucleotides may be single stranded or double stranded, e.g. for use in the construction of a gene mutant. Oligonucleotides of the invention may be 25 sense or antisense oligonucleotides with reference to a protein-coding sequence. The term "naturally occurring nucleotides" includes deoxyribonucleotides and ribonucleotides. The term "modified nucleotides" includes nucleotides with modified or substituted sugar groups and the like. The term "oligonucleotide linkages" includes oligonucleotides linkages such as phosphorothioate, phosphorodithioate, 30 phosphoroselenoate, phosphorodiselenoate, phosphoroanilothioate, phoshoraniladate, phosphoroamidate, and the like. See, e.g., LaPlanche et al., 1986, Nucl. Acids Res. 14: 9081; Stec et al., 1984, J Am. Chem. Soc. 106: 6077; Stein et al., 1988, Nucl. Acids Res. 17 WO 03/086289 PCT/US03/10749 16: 3209; Zon et al., 1991, Anti-Cancer Drug Design 6: 539; Zon et al., 1991, OLIGONUCLEOTLDES AND ANALOGUES: A PRACTICAL APPROACH, (F. Eckstein, ed.), Oxford University Press, Oxford England, pp. 87-108; Stec et al., U.S. Pat. No. 5,151,510; Uhlmann and Peyman, 1990, Chemical Reviews 90: 543, the disclosures 5 of each of which are hereby incorporated by reference for any purpose. An oligonucleotide can include a detectable label to enable detection of the oligonucleotide or hybridization thereof. The term "vector" is used to refer to any molecule (e.g., nucleic acid, plasmid, or virus) used to transfer coding information to a host cell. 10 The term "expression vector" refers to a vector that is suitable for transformation of a host cell and contains nucleic acid sequences that direct and/or control the expression of inserted heterologous nucleic acid sequences. Expression includes, but is not limited to, processes such as transcription, translation, and RNA splicing, if introns are present. The term "host cell" is used to refer to a cell which has been transformed, or that 15 is capable of being transformed with a nucleic acid sequence and then of expressing a selected gene of interest. The term includes the progeny of the parent cell, whether or not the progeny is identical in morphology or in genetic make-up to the original parent, so long as the selected gene is present. The term "transduction" is used to refer to the transfer of genes from one 20 bacterium to another, usually by a phage. "Transduction" also refers to the acquisition and transfer of eukaryotic cellular sequences by retroviruses. The term "transfection" is used to refer to the uptake of foreign or exogenous DNA by a cell, and a cell has been "transfected" when the exogenous DNA has been introduced inside the cell membrane. A number of transfection techniques are well 25 known in the art and are disclosed herein. See, e.g., Graham et al., 1973, Virology 52: 456; Sambrook et al., 2001, ibid.; Davis et al., 1986, BASIC METHODS IN MOLECULAR BIOLOGY (Elsevier); and Chu et al., 1981, Gene 13: 197. Such techniques can be used to introduce one or more exogenous DNA moieties into suitable host cells. 30 The term "transformation" as used herein refers to a change in a cell's genetic characteristics, and a cell has been transformed when it has been modified to contain a 18 WO 03/086289 PCT/US03/10749 new DNA. For example, a cell is transformed where it is genetically modified from its native state. Following transfection or transduction, the transforming DNA may recombine with that of the cell by physically integrating into a chromosome of the cell, may be maintained transiently as an episomal element without being replicated, or may 5 replicate independently as a plasmid. A cell is considered to have been stably transformed when the DNA is replicated with the division of the cell. The term "naturally occurring" or "native" when used in connection with biological materials such as nucleic acid molecules, polypeptides, host cells, and the like, refers to materials which are found in nature and are not manipulated by man. Similarly, 10 "non-naturally occurring" or "non-native" as used herein refers to a material that is not found in nature or that has been structurally modified or synthesized by man. The term "antigen" refers to a molecule or a portion of a molecule capable of being bound by a selective binding agent, such as an antibody, and additionally capable of being used in an animal to produce antibodies capable of binding to an epitope of that 15 antigen. An antigen may have one or more epitopes. The term "identity," as known in the art, refers to a relationship between the sequences of two or more polypeptide molecules or two or more nucleic acid molecules, as determined by comparing the sequences thereof. In the art, "identity" also means the degree of sequence relatedness between nucleic acid molecules or polypeptides, as the 20 case may be, as determined by the match between two or more nucleotide or two or more amino acid sequences. "Identity" measures the percent of identical matches between the smaller of two or more sequences with gap alignments (if any) addressed by a particular mathematical model or computer program (i.e., "algorithms"). The term "similarity" is used in the art with regard to a related concept, but in 25 contrast to "identity," "similarity" refers to a measure of relatedness, which includes both identical matches and conservative substitution matches. If two polypeptide sequences have, for example, 10/20 identical amino acids, and the remainder are all non conservative substitutions, then the percent identity and similarity would both be 50%. If in the same example, there are five more positions where there are conservative 30 substitutions, then the percent identity remains 50%, but the percent similarity would be 75% (15/20). Therefore, in cases where there are conservative substitutions, the percent 19 WO 03/086289 PCT/US03/10749 similarity between two polypeptides will be higher than the percent identity between those two polypeptides. Identity and similarity of related and polypeptides can be readily calculated by known methods. Such methods include, but are not limited to, those described in 5 COMPUTATIONAL MOLECULAR BIOLOGY, (Lesk, A.M., ed.), 1988, New York: Oxford University Press; BIOCOMPUTING: INFORMATICS AND GENOME PROJECTS, (Smith, D.W., ed.), 1993, New York: Academic Press; COMPUTER ANALYSIS OF SEQUENCE DATA, PART 1, (Griffin, A.M., and Griffin, H.G., eds.), 1994, New Jersey: Humana Press; von Heinje, G., 1987, SEQUENCE ANALYSIS IN 10 MOLECULAR BIOLOGY, New York: Academic Press; SEQUENCE ANALYSIS PRIMER, (Gribskov, M. and Devereux, J., eds.), 1991, New York: M. Stockton Press; and Carillo et al., 1988, SIAM J Applied Math. 48:1073; and Durbin et al., 1998, BIOLOGICAL SEQUENCE ANALYSIS, Cambridge University Press. Preferred methods to determine identity are designed to give the largest match 15 between the sequences tested. Methods to determine identity are described in publicly available computer programs. Preferred computer program methods to determine identity between two sequences include, but are not limited to, the GCG program package, including GAP (Devereux et al., 1984, Nucl. Acid. Res. 12:387; Genetics Computer Group, University of Wisconsin, Madison, WI, BLASTP, BLASTN, and FASTA, 20 Altschul et al., 1990, J. Mol. Biol. 215: 403-410). The BLASTX program is publicly available from the National Center for Biotechnology Information (NCBI) and other sources (BLAST Manual, Altschul et al. NCB/NLM/NIH Bethesda, MD 20894; Altschul et al., 1990, supra). The well-known Smith Waterman algorithm may also be used to determine identity. 25 Certain alignment schemes for aligning two amino acid sequences may result in the matching of only a short region of the two sequences, and this small aligned region may have very high sequence identity even though there is no significant relationship between the two full-length sequences. Accordingly, in certain embodiments, the selected alignment method (GAP program) will result in an alignment that spans at least 30 50 contiguous amino acids of the target polypeptide. For example, using the computer algorithm GAP (Genetics Computer Group, University of Wisconsin, Madison, WI), two polypeptides for which the percent sequence 20 WO 03/086289 PCT/US03/10749 identity is to be determined are aligned for optimal matching of their respective amino acids (the "matched span", as determined by the algorithm). In certain embodiments, a gap opening penalty (which is calculated as three times the average diagonal, wherein the "average diagonal" is the average of the diagonal of the comparison matrix being used; 5 the "diagonal" is the score or number assigned to each perfect amino acid match by the particular comparison matrix) and a gap extension penalty (which is usually one-tenth of the gap opening penalty), as well as a comparison matrix such as PAM 250 or BLOSUM 62 are used in conjunction with the algorithm. In certain embodiments, a standard comparison matrix (see Dayhoff et al., 1978, Atlas of Protein Sequence and Structure 10 5:345-352 for the PAM 250 comparison matrix; Henikoff et al., 1992, Proc. Natl. Acad. Sci. USA 89: 10915-10919 for the BLOSUM 62 comparison matrix) is also used by the algorithm. In certain embodiments, the parameters for a polypeptide sequence comparison include the following: 15 Algorithm: Needleman et al., 1970, J. Mol. Biol. 48:443-453; Comparison matrix: BLOSUM 62 from Henikoff et al., 1992, supra; Gap Penalty: 12 Gap Length Penalty: 4 Threshold of Similarity: 0 20 The GAP program may be useful with the above parameters. In certain embodiments, the aforementioned parameters are the default parameters for polypeptide comparisons (along with no penalty for end gaps) using the GAP algorithm. As used herein, the twenty conventional amino acids and their abbreviations follow conventional usage. See IMMUNOLOGY--A SYNTHESIS, 2nd Edition, (E. S. 25 Golub and D. R. Gren, Eds.), 1991, Sinauer Associates, Sunderland, Mass., which is incorporated herein by reference for any purpose. Stereoisomers (e.g., D-amino acids) of the twenty conventional amino acids, unnatural amino acids such as a-, a-disubstituted amino acids, N-alkyl amino acids, lactic acid, and other unconventional amino acids may also be suitable components for polypeptides of the present invention. Examples of 30 unconventional amino acids include: 4-hydroxyproline, y-carboxyglutamate, s-NN,N 21 WO 03/086289 PCT/US03/10749 trimethyllysine, e-N-acetyllysine, O-phosphoserine, N-acetylserine, N-formyhnethionine, 3-methylhistidine, 5-hydroxylysine, a-N-methylarginine, and other similar amino acids and imino acids (e.g., 4-hydroxyproline). In the polypeptide notation used herein, the left-hand direction is the amino terminal direction and the right-hand direction is the 5 carboxy-terminal direction, in accordance with standard usage and convention. Similarly, unless specified otherwise, the left-hand end of single-stranded polynucleotide sequences is the 5' end; the left-hand direction of double-stranded polynucleotide sequences is referred to as the 5' direction. The direction of 5' to 3' addition of nascent RNA transcripts is referred to as the transcription direction; sequence 10 regions on the DNA strand having the same sequence as the RNA and which are 5' to the 5' end of the RNA transcript are referred to as "upstream sequences"; sequence regions on the DNA strand having the same sequence as the RNA and which are 3' to the 3' end of the RNA transcript are referred to as "downstream sequences". Naturally occurring residues may be divided into classes based on common side 15 chain properties: 1) hydrophobic: norleucine, Met, Ala, Val, Leu, Ile; 2) neutral hydrophilic: Cys, Ser, Thr, Asn, Gln; 3) acidic: Asp, Glu; 4) basic: His, Lys, Arg; 20 5) residues that influence chain orientation: Gly, Pro; and 6) aromatic: Trp, Tyr, Phe. Conservative amino acid substitutions may encompass non-naturally occurring amino acid residues, which are typically incorporated by chemical peptide synthesis rather than by synthesis in biological systems. These include peptidomimetics and other 25 reversed or inverted forms of amino acid moieties. Non-conservative substitutions may involve the exchange of a member of one of these classes for a member from another class. Such substituted residues may be introduced into regions of the human antibody that are homologous with non-human antibodies, or into the non-homologous regions of the molecule. 22 WO 03/086289 PCT/US03/10749 In making such changes, according to certain embodiments, the hydropathic index of amino acids may be considered. Each amino acid has been assigned a hydropathic index on the basis of its hydrophobicity and charge characteristics. They are: isoleucine (+4.5); valine (+4.2); leucine (+3.8); phenylalanine (+2.8); cysteine/cystine (+2.5); 5 methionine (+1.9); alanine (+1.8); glycine (-0.4); threonine (-0.7); serine (-0.8); tryptophan (-0.9); tyrosine (-1.3); proline (-1.6); histidine (-3.2); glutamate (-3.5); glutamine (-3.5); aspartate (-3.5); asparagine (-3.5); lysine (-3.9); and arginine (-4.5). The importance of the hydropathic amino acid index in conferring interactive biological function on a protein is understood in the art (see, for example, Kyte et al., 10 1982, J MoL. Biol. 157:105-13 1). It is known that certain amino acids may be substituted for other amino acids having a similar hydropathic index or score and still retain a similar biological activity. In making changes based upon the hydropathic index, in certain embodiments, the substitution of amino acids whose hydropathic indices are within ±2 is included. In certain embodiments, those which are within t1 are included, and in certain 15 embodiments, those within 10.5 are included. It is also understood in the art that the substitution of like amino acids can be made effectively on the basis of hydrophilicity, particularly where the biologically functional protein or peptide thereby created is intended for use in immunological embodiments, as in the present case. In certain embodiments, the greatest local average 20 hydrophilicity of a protein, as governed by the hydrophilicity of its adjacent amino acids, correlates with its immunogenicity and antigen-binding or immunogenicity, i.e., with a biological property of the protein. The following hydrophilicity values have been assigned to these amino acid residues: arginine (+3.0); lysine (+3.0); aspartate (+3.0 ± 1); glutamate (+3.0 h 1); serine 25 (+0.3); asparagine (+0.2); glutamine (+0.2); glycine (0); threonine (-0.4); proline (-0.5 ± 1); alanine (-0.5); histidine (-0.5); cysteine (-1.0); methionine (-1.3); valine (-1.5); leucine (-1.8); isoleucine (-1.8); tyrosine (-2.3); phenylalanine (-2.5) and tryptophan (-3.4). In making changes based upon similar hydrophilicity values, in certain embodiments, the substitution of amino acids whose hydrophilicity values are within 12 is included, in 30 certain embodiments, those which are within ±1 are included, and in certain embodiments, those within ±0.5 are included. One may also identify epitopes from 23 WO 03/086289 PCT/US03/10749 primary amino acid sequences on the basis of hydrophilicity. These regions are also referred to as "epitopic core regions." Exemplary amino acid substitutions are set forth in Table 1. 5 Table1 Amino Acid Substitutions Original Exemplary Preferred Residues Substitutions Substitutions Ala Val, Leu, lie Val Arg Lys, Gin, Asn Lys Asn Gin Gln Asp Glu Glu Cys Ser, Ala Ser Gin Asn Asn Glu Asp Asp Gly Pro, Ala Ala His Asn, Gin, Lys, Arg Arg le Leu, Val, Met, Ala, Leu Phe, Norleucine Ieu Norleucine, Ile, Leu _ _Val, Met, Ala, Phe Lys Arg, Gin, Asn, kg 1,4 Diamine-butyric Acid Met Leu, Phe, Ile Leu Phe Leu, Val, Ile, Ala, Leu Tyr Pro Ala Gly Ser Thr, Ala, Cys Thr Thr Ser Ser Trp Tyr, Phe Tyr Tyr Trp, Phe, Thr, Ser Phe Val Ile, Met, Leu, Phe, Leu Ala, Norleucine I A skilled artisan will be able to determine suitable variants of the polypeptide as set forth herein using well-known techniques. In certain embodiments, one skilled in the 10 art can identify suitable areas of the molecule that can be changed without destroying activity by targeting regions not believed to be important for activity. In other embodiments, the skilled artisan can identify residues and portions of the molecules that are conserved among similar polypeptides. In further embodiments, even areas that are important for biological activity or for structure may be subject to conservative amino 24 WO 03/086289 PCT/US03/10749 acid substitutions without destroying the biological activity or without adversely affecting the polypeptide structure. Additionally, one skilled in the art can review structure-function studies identifying residues in similar polypeptides that are important for activity or structure. In 5 view of such a comparison, the skilled artisan can predict the importance of amino acid residues in a protein that correspond to amino acid residues important for activity or structure in similar proteins. One skilled in the art may opt for chemically similar amino acid substitutions for such predicted important amino acid residues. One skilled in the art can also analyze the three-dimensional structure and amino 10 acid sequence in relation to that structure in similar polypeptides. In view of such information, one skilled in the art may predict the alignment of amino acid residues of an antibody with respect to its three dimensional structure. In certain embodiments, one skilled in the art may choose not to make radical changes to amino acid residues predicted to be on the surface of the protein, since such residues may be involved in important 15 interactions with other molecules. Moreover, one skilled in the art may generate test variants containing a single amino acid substitution at each desired amino acid residue. The variants can then be screened using activity assays known to those skilled in the art. Such variants can be used to gather information about suitable variants. For example, if it was discovered that a change to a particular amino acid residue resulted in destroyed, 20 undesirably reduced, or unsuitable activity, variants with such a change can be avoided. In other words, based on information gathered from such routine experiments, one skilled in the art can readily determine the amino acids where further substitutions should be avoided either alone or in combination with other mutations. A number of scientific publications have been devoted to the prediction of 25 secondary structure. See Molt, 1996, Curr. Op. in Biotech. 7: 422-427; Chou et al., 1974, Biochemistry 13: 222-245; Chou et al., 1974, Biochemistry 113: 211-222; Chou et al., 1978, Adv. Enzymol. Relat. Areas Mol. Biol. 47: 45-148; Chou et al., 1978, Ann. Rev. Biochem. 47: 251-276 and Chou et al., 1979, Biophys. J. 26: 367-384. Moreover, computer programs are currently available to assist with predicting secondary structure. 30 One method of predicting secondary structure is based upon homology modeling. For example, two polypeptides or proteins which have a sequence identity of greater than 30%, or similarity greater than 40% often have similar structural topologies. The recent 25 WO 03/086289 PCT/US03/10749 growth of the protein structural database (PDB) has provided enhanced predictability of secondary structure, including the potential number of folds within a polypeptide's or protein's structure. See Holm et al., 1999, Nucl. Acid. Res. 27: 244-247. It has been suggested (Brenner et al., 1997, Curr. Op. Struct. Biol. 7: 369-376) that there are a 5 limited number of folds in a given polypeptide or protein and that once a critical number of structures have been resolved, structural prediction will become dramatically more accurate. Additional methods of predicting secondary structure include "threading" (Jones, 1997, Curr. Opin. Struct. Biol. 7: 377-87; Sippl et al., 1996, Structure 4: 15-19), "profile 10 analysis" (Bowie et al., 1991, Science 253: 164-170; Gribskov et al., 1990, Meth. Enzym. 183: 146-159; Gribskov et al., 1987, Proc. Nat. Acad. Sci. USA 84: 4355-4358), and "evolutionary linkage" (See Hohm, 1999, supra, and Brenner, 1997, supra). In certain embodiments, antibody variants include glycosylation variants wherein the number and/or type of glycosylation site has been altered compared to the amino acid 15 sequences of the parent polypeptide. In certain embodiments, protein variants comprise a greater or a lesser number of N-linked glycosylation sites than the native protein. An N linked glycosylation site is characterized by the sequence: Asn-X-Ser or Asn-X-Thr, wherein the amino acid residue designated as X may be any amino acid residue except proline. The substitution of amino acid residues to create this sequence provides a 20 potential new site for the addition of an N-linked carbohydrate chain. Alternatively, substitutions that eliminate or alter this sequence will prevent addition of an N-linked carbohydrate chain present in the native polypeptide. Also provided are rearrangements of N-linked carbohydrate chains wherein one or more N-linked glycosylation sites (typically those that are naturally occurring) are eliminated and one or more new N-linked 25 sites are created. Additional preferred antibody variants include cysteine variants wherein one or more cysteine residues in the parent or native amino acid sequence are deleted from or substituted for another amino acid (e.g., serine). Cysteine variants are useful, inter alia when antibodies must be refolded into a biologically active conformation, for example, after the isolation of insoluble inclusion bodies. Cysteine variants generally 30 have fewer cysteine residues than the native protein, and typically have an even number to minimize interactions resulting from unpaired cysteines. 26 WO 03/086289 PCT/US03/10749 In additional embodiments, antibody variants can include antibodies comprising a modified Fc fragment or a modified heavy chain constant region. An Fc fragment, which stands for "fragment that crystallizes," or a heavy chain constant region can be modified by mutation to confer on an antibody altered binding characteristics. See, for example, 5 Burton and Woof, 1992, Advances in Immunology 51: 1-84; Ravetch and Bolland, 2001, Annu. Rev. Immunol. 19: 275-90; Shields et al., 2001, Journal of Biol. Chem 276: 6591 6604; Telleman and Junghans, 2000, Immunology 100: 245-251; Medesan et al., 1998, Eur. J. Immnunol. 28: 2092-2100; all of which are incorporated herein by reference). Such mutations can include substitutions, additions, deletions, or any combination 10 thereof, and are typically produced by site-directed mutagenesis using one or more mutagenic oligonucleotide(s) according to methods described herein, as well as according to methods known in the art (see, for example, Maniatis et aL., MOLECULAR CLONING: A LABORATORY MANUAL, 3rd Ed., 2001, Cold Spring Harbor, N.Y. and Berger and Kimmel, METHODS IN ENZYMOLOGY, Volume 152, Guide to Molecular 15 Cloning Techniques, 1987, Academic Press, Inc., San Diego, CA., which are incorporated herein by reference). According to certain embodiments, amino acid substitutions are those that: (1) reduce susceptibility to proteolysis, (2) reduce susceptibility to oxidation, (3) alter binding affinity for forming protein complexes, (4) alter ligand or antigen binding 20 affinities, and/or (5) confer or modify other physicochemical or functional properties on such polypeptides. According to certain embodiments, single or multiple amino acid substitutions (in certain embodiments, conservative amino acid substitutions) may be made in the naturally-occurring sequence (in certain embodiments, in the portion of the polypeptide outside the domain(s) forming intermolecular contacts). In certain 25 embodiments, a conservative amino acid substitution typically does not substantially change the structural characteristics of the parent sequence (e.g., a replacement amino acid should not tend to break a helix that occurs in the parent sequence, or disrupt other types of secondary structure that characterizes the parent sequence). Examples of art recognized polypeptide secondary and tertiary structures are described in PROTEINS, 30 STRUCTURES AND MOLECULAR PRINCIPLES (Creighton, Ed.), 1984, W. H. New York: Freeman and Company; INTRODUCTION TO PROTEIN STRUCTURE (Branden 27 WO 03/086289 PCT/US03/10749 and Tooze, eds.), 1991, New York: Garland Publishing; and Thornton et at., 1991, Nature 354: 105, each of which are incorporated herein by reference. Peptide analogs are commonly used in the pharmaceutical industry as non peptide drugs with properties analogous to those of the template peptide. These types of 5 non-peptide compound are termed "peptide mimetics" or "peptidomimetics". Fauchere, 1986, Adv. Drug Res. 15: 29; Veber and Freidinger, 1985, TINS p.392; and Evans et al., 1987, J. Med. Chem. 30: 1229, which are incorporated herein by reference for any purpose. Such compounds are often developed with the aid of computerized molecular modeling. Peptide mimetics that are structurally similar to therapeutically useful peptides 10 may be used to produce a similar therapeutic or prophylactic effect. Generally, peptidomimetics are structurally similar to a paradigm polypeptide (i.e., a polypeptide that has a biochemical property or pharmacological activity), such as human antibody, but have one or more peptide linkages optionally replaced by a linkage selected from: -

CH

2 NH--, --CH 2 S--, --CH 2

-CH

2 --, --CH=CH-(cis and trans), --COCH 2 --, --CH(OH)CH 2 15 -, and --CH 2 SO--, by methods well known in the art. Systematic substitution of one or more amino acids of a consensus sequence with a D-amino acid of the same type (e.g., D lysine in place of L-lysine) may be used in certain embodiments to generate more stable peptides. In addition, constrained peptides comprising a consensus sequence or a substantially identical consensus sequence variation may be generated by methods known 20 in the art (Rizo and Gierasch, 1992, Ann. Rev. Biochen. 61: 387), incorporated herein by reference for any purpose); for example, by adding internal cysteine residues capable of forming intramolecular disulfide bridges which cyclize the peptide. "Antibody" or "antibody peptide(s)" refer to an intact antibody, or a binding fragment thereof that competes with the intact antibody for specific binding. In certain 25 embodiments, binding fragments are produced by recombinant DNA techniques. In certain embodiments, binding fragments are produced by enzymatic or chemical cleavage of intact antibodies. Binding fragments include, but are not limited to, Fab, Fab', F(ab') 2 , Fv, and single-chain antibodies. The term "heavy chain" includes any immunoglobulin polypeptide having a heavy 30 chain constant region and sufficient variable region sequence to confer specificity for an OPGL. The term "light chain" includes any immunoglobulin polypeptide having a light chain constant region and sufficient variable region sequence to confer specificity for an 28 WO 03/086289 PCT/US03/10749 OPGL. A full-length heavy chain includes a variable region domain, VH, and three constant region domains, CHI, CH2, and CH3. The VH domain is at the amino-terminus of the polypeptide, and the CH3 domain is at the carboxyl-terminus. The term "heavy chain", as used herein, encompasses a full-length heavy chain and fragments thereof A 5 full-length light chain includes a variable region domain, VL, and a constant region domain, CL. Like the heavy chain, the variable region domain of the light chain is at the amino-terminus of the polypeptide. The term "light chain", as used herein, encompasses a full-length light chain and fragments thereof. A F(ab) fragment is comprised of one light chain and the CHI and variable regions of one heavy chain. The heavy chain of a 10 F(ab) molecule cannot form a disulfide bond with another heavy chain molecule. A F(ab') fragment contains one light chain and one heavy chain that contains more of the constant region, between the CHi and CH 2 domains, such that an interchain disulfide bond can be formed between two heavy chains to form a F(ab') 2 molecule. The Fv region comprises the variable regions from both the heavy and light chains, but lacks the 15 constant regions. Single-chain antibodies are Fv molecules in which the heavy and light chain variable regions have been connected by a flexible linker to form a single polypeptide chain that forms an antigen-binding region. Single chain antibodies are discussed in detail in WO 88/01649 and U.S. Patent Nos. 4,946,778 and 5,260,203 incorporate by reference. 20 A bivalent antibody other than a "multispecific" or "multifunctional" antibody, in certain embodiments, is understood to comprise binding sites having identical antigenic specificity. In assessing antibody binding and specificity according to the invention, an antibody substantially inhibits adhesion of a ligand to a receptor when an excess of 25 antibody reduces the quantity of ligand bound to receptor by at least about 20%, 40%, 60%, 80%, 85%, or more (as measured in an in vitro competitive binding assay). The term "epitope" includes any polypeptide determinant, preferably a polypeptide determinant, capable of specific binding to an immunoglobulin or T-cell receptor. In certain embodiments, epitope determinants include chemically active surface 30 groupings of molecules such as amino acids, sugar side chains, phosphoryl, or sulfonyl, and, in certain embodiments, may have specific three dimensional structural characteristics, and/or specific charge characteristics. An epitope is a region of an antigen 29 WO 03/086289 PCT/US03/10749 that is bound by an antibody. In certain embodiments, an antibody is said to specifically bind an antigen when it preferentially recognizes its target antigen in a complex mixture of proteins and/or macromolecules. In certain embodiments, an antibody is said to specifically bind an antigen when the dissociation constant is 10~8 M, in certain 5 embodiments, when the dissociation constant is 10- M, and in certain embodiments, when the dissociation constant is 10!10 M. The term "agent" is used herein to denote a chemical compound, a mixture of chemical compounds, a biological macromolecule, or an extract made from biological materials. 10 As used herein, the terms "label" or "labeled" refers to incorporation of a detectable marker, e.g., by incorporation of a radiolabeled amino acid or attachment to a polypeptide of biotin moieties that can be detected by labeled avidin (e.g., streptavidin preferably comprising a detectable marker such as a fluorescent marker, a chemiluminescent marker or an enzymatic activity that can be detected by optical or 15 colorimetric methods). In certain embodiments, the label can also be therapeutic. Various methods of labeling polypeptides and glycoproteins are known in the art and may be used advantageously in the methods disclosed herein. Examples of labels for polypeptides include, but are not limited to, the following: radioisotopes or radionuclides (e.g., 3 H, 4 C, 'N, 3 S, "Y, 9 "'Tc, ' 1 In, 1251 131I fluorescent labels (e.g., fluorescein 20 isothiocyanate or FITC, rhodamine, or lanthanide phosphors), enzymatic labels (e.g., horseradish peroxidase, -galactosidase, luciferase, alkaline phosphatase), chemiluminescent labels, hapten labels such as biotinyl groups, and predetermined polypeptide epitopes recognized by a secondary reporter (e.g., leucine zipper pair sequences, binding sites for secondary antibodies, metal binding domains, or epitope 25 tags). In certain embodiments, labels are attached by spacer arms (such as (CH 2 )n, where n < about 20) of various lengths to reduce potential steric hindrance. The term "biological sample", as used herein, includes, but is not limited to, any quantity of a substance from a living thing or formerly living thing. Such living things include, but are not limited to, m humans, mice, monkeys, rats, rabbits, and other animals. 30 Such substances include, but are not limited to, blood, serum, urine, cells, organs, tissues, bone, bone marrow, lymph nodes, and skin. 30 WO 03/086289 PCT/US03/10749 The term "osteopenic disorder" includes, but is not limited to, osteoporosis, osteopenia, Paget's disease, lytic bone metastases, periodontitis, rheumatoid arthritis, and bone loss due to immobilization. In addition to these bone disorders, certain cancers are known to increase osteoclast activity and induce bone resorption, such as breast and 5 prostate cancer and multiple myeloma. These cancers are now known to produce factors that result in the over-expression of OPGL in the bone, and lead to increased osteoclast numbers and activity. The term "pharmaceutical agent or drug" as used herein refers to a chemical compound or composition capable of inducing a desired therapeutic effect when properly 10 administered to a patient. As used herein, "substantially pure" or "substantially purified" means a compound or species that is the predominant species present (i.e., on a molar basis it is more abundant than any other individual species in the composition). In certain embodiments, a substantially purified fraction is a composition wherein the object species comprises at 15 least about 50 percent (on a molar basis) of all macromolecular species present. In certain embodiments, a substantially pure composition will comprise more than about 80%, 85%, 90%, 95%, or 99% of all macromolar species present in the composition. In certain embodiments, the species is purified to essential homogeneity (contaminant species cannot be detected in the composition by conventional detection methods) wherein the 20 composition consists essentially of a single macromolecular species. The term "patient" includes human and animal subjects. Unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular. The invention provides antibodies, preferably monoclonal antibodies and most 25 preferably human antibodies, that are immunologically specific for osteoprotegerin ligand (OPGL), a member of the tumor necrosis factor (TNF) family of cytokines that is involved in the formation of osteoclasts. Increased osteoclast activity correlates with a number of osteopenic disorders, including post-menopausal osteoporosis, Paget's disease, lytic bone metastases, and rheumatoid arthritis. Thus, a reduction in OPGL activity may 30 result in a decrease in osteoclast activity and may reduce the severity of osteopenic disorders. According to certain embodiments of the invention, antibodies directed to 31 WO 03/086289 PCT/US03/10749 OPGL may be used detect, diagnose, prevent and treat osteopenic disorders, including by not limited to, those mentioned above. In certain embodiments of the present invention, there is provided a fully human monoclonal antibody against human OPGL. In certain embodiments, nucleotide 5 sequences encoding, and amino acid sequences comprising, heavy and light chain immunoglobulin molecules, particularly sequences corresponding to the variable regions, are provided. In certain embodiments, sequences corresponding to complementarity determining regions (CDR's), specifically from CDR1 through CDR3, are provided. According to certain embodiments, a hybridoma cell line expressing such an 10 immunoglobulin molecule and monoclonal antibody is also provided. In certain embodiments, the invention provides purified human monoclonal antibody against human OPGL. The ability to clone and reconstruct megabase-sized human loci in yeast artificial chromosomes (YACs) and to introduce them into the mouse germline provides an 15 approach to elucidating the functional components of very large or crudely mapped loci as well as generating useful models of human disease. Furthermore, the utilization of such technology for substitution of mouse loci with their human equivalents provides unique insights into the expression and regulation of human gene products during development, their communication with other systems, and their involvement in disease 20 induction and progression. An important practical application of such a strategy is the "humanization" of the mouse humoral immune system. Introduction of human immunoglobulin (Ig) loci into mice in which the endogenous Ig genes have been inactivated offers the opportunity to study mechanisms underlying programmed expression and assembly of antibodies as well 25 as their role in B-cell development. Furthermore, such a strategy provides a source for production of fully human monoclonal antibodies (MAbs). Fully human antibodies are expected to minimize the immunogenic and allergic responses intrinsic to mouse or mouse-derivatized MAbs, and to thereby increase the efficacy and safety of the administered antibodies. Fully human antibodies can be used in the treatment of chronic 30 and recurring human diseases, such as osteoporosis, inflammation, autoimmunity, and cancer, the treatment thereof requiring repeated antibody administration. Thus, one particular advantage of the anti-OPGL antibodies of the invention is that the antibodies 32 WO 03/086289 PCT/US03/10749 are fully human and can be administered to patients in a non-acute manner while minimizing adverse reactions commonly associated with human anti-mouse antibodies or other previously described non-fully human antibodies from non-human species. One skilled in the art can engineer mouse strains deficient in mouse antibody 5 production with large fragments of the human Ig loci so that the mice produce human but not mouse antibodies. Large human Ig fragments in mouse germline preserve variable gene diversity as well as the proper regulation of antibody production and expression. By exploiting the mouse machinery for antibody diversification and selection and the lack of immunological tolerance to human proteins, the reproduced human antibody repertoire in 10 these mouse strains yield high affinity antibodies against any antigen of interest, including human antigens. Using hybridoma technology, antigen-specific human mAbs with the desired specificity can be produced and selected. In certain embodiments, the skilled artisan can use constant regions from species other than human along with the human variable region(s) to produce chimeric 15 antibodies. Naturally Occurring Antibody Structure Naturally occurring antibody structural units typically comprise a tetramer. Each such tetramer typically is composed of two identical pairs of polypeptide chains, each pair 20 having one full-length "light" chain (in certain embodiments, about 25 kDa) and one full length "heavy" chain (in certain embodiments, about 50-70 kDa). The amino-terminal portion of each chain typically includes a variable region of about 100 to 110 or more amino acids that typically is responsible for antigen recognition. The carboxy-terminal portion of each chain typically defines a constant region that may be responsible for 25 effector function. Human light chains are typically classified as kappa and lambda light chains. Heavy chains are typically classified as mu, delta, gamma, alpha, or epsilon, and define the antibody's isotype as IgM, IgD, IgG, IgA, and IgE, respectively. IgG has several subclasses, including, but not limited to, IgG 1 , IgG2, IgG 3 , and IgG 4 . IgM has subclasses including, but not limited to, IgM 1 and IgM 2 . IgA is similarly subdivided into 30 subclasses including, but not limited to, IgA and IgA 2 . Within full-length light and heavy chains, typically, the variable and constant regions are joined by a "J" region of 33 WO 03/086289 PCT/US03/10749 about 12 or more amino acids, with the heavy chain also including a "D" region of about 10 more amino acids. See, e.g., FUNDAMENTAL IMMUNOLOGY, 2nd ed., Ch. 7 (Paul, W., ed.) 1989, New York: Raven Press (incorporated by reference in its entirety for all purposes). The variable regions of each light/heavy chain pair typically form the 5 antigen-binding site. The variable regions typically exhibit the same general structure of relatively conserved framework regions (FR) joined by three hypervariable regions, also called complementarity determining regions or CDRs. The CDRs from the two chains of each pair typically are aligned by the framework regions, which may enable binding to a 10 specific epitope. From N-terminal to C-terminal, both light and heavy chain variable regions typically comprise the domains FR1, CDR1, FR2, CDR2, FR3, CDR3 and FR4. The assignment of amino acids to each domain is typically in accordance with the definitions of Kabat Sequences of Proteins of Immunological Interest (1987 and 1991, National Institutes of Health, Bethesda, Md.), or Chothia & Lesk, 1987, J. Mol. Biol. 196: 15 901-917; Chothia et al., 1989, Nature 342: 878-883. Bispecific or Bifunctional Antibodies A bispecific or bifunctional antibody typically is an artificial hybrid antibody having two different heavy/light chain pairs and two different binding sites. Bispecific 20 antibodies may be produced by a variety of methods including, but not limited to, fusion of hybridomas or linking of Fab' fragments. See, e.g., Songsivilai & Lachmann, 1990, Clin. Exp. Immunol. 79: 315-321; Kostelny et al., 1992, J Ininunol. 148: 1547-1553. Preparation of Antibodies 25 The invention provides antibodies that specifically bind to human OPGL. In certain embodiments, the antibodies can be produced by immunization with full-length OPGL or fragments thereof. The antibodies of the invention can be polyclonal or monoclonal, and/or may be recombinant antibodies. In preferred embodiments, antibodies of the invention are human antibodies prepared, for example, by immunization 30 of transgenic animals capable of producing human antibodies (see, for example, PCT Published Application No. WO 93/12227). 34 WO 03/086289 PCTiUS03/10749 The complementarity determining regions (CDRs) of the light and heavy chain variable regions of anti-OPGL antibody may be grafted to framework regions (FRs) from antibodies from the same, or another, species. In certain embodiments, the CDRs of the light and heavy chain variable regions of anti-OPGL antibody may be grafted to 5 consensus human FRs. To create consensus human FRs, in certain embodiments, FRs from several human heavy chain or light chain amino acid sequences are aligned to identify a consensus amino acid sequence. In certain embodiments, the FRs of the anti OPGL antibody heavy chain or light chain are replaced with the FRs from a different heavy chain or light chain. In certain embodiments, rare amino acids in the FRs of the 10 heavy and light chains of anti-OPGL antibody are not replaced, while the rest of the FR amino acids are replaced. Rare amino acids are specific amino acids that are in positions in which they are not usually found in FRs. In certain embodiments, the grafted variable regions from anti-OPGL antibody may be used with a constant region that is different from the constant region of anti-OPGL antibody. In certain embodiments, the grafted 15 variable regions are part of a single chain Fv antibody. CDR grafting is described, e.g., in U.S. Patent Nos. 6,180,370, 5,693,762, 5,693,761, 5,585,089, and 5,530,101, which are hereby incorporated by reference for any purpose. Antibodies of the invention are prepared using transgenic mice that have a substantial portion of the human antibody producing locus inserted in antibody-producing 20 cells of the mice, and that are further engineered to be deficient in producing endogenous, murine, antibodies. Such mice are capable of producing human immunoglobulin molecules and antibodies and do not produce or produce substantially reduced amounts of murine immunoglobulin molecules and antibodies. Technologies utilized for achieving this result are disclosed in the patents, applications, and references disclosed in the 25 patents, applications, and references disclosed in the specification herein. In certain embodiments, the skilled worker may employ methods as disclosed in International Patent Application Publication No. WO 98/24893, which is hereby incorporated by reference for any purpose. See also Mendez et al., 1997, Nature Genetics 15: 146-156, which is hereby incorporated by reference for any purpose. 30 The monoclonal antibodies (mAbs) of the invention can be produced by a variety of techniques, including conventional monoclonal antibody methodology, e.g., the standard somatic cell hybridization technique of Kohler and Milstein, 1975, Nature 256: 35 WO 03/086289 PCT/US03/10749 495. Although somatic cell hybridization procedures are preferred, in principle, other techniques for producing monoclonal antibodies can be employed, e.g., viral or oncogenic transformation of B-lymphocytes. The preferred animal system for preparing hybridomas is the mouse. Hybridoma 5 production in the mouse is very well established, and immunization protocols and techniques for isolation of immunized splenocytes for fusion are well known in the art. Fusion partners (e.g., murine myeloma cells) and fusion procedures are also known. In a preferred embodiment, human monoclonal antibodies directed against OPGL can be generated using transgenic mice carrying parts of the human immune system 10 rather than the mouse system. These transgenic mice, referred to herein as "HuMab" mice, contain a human immunoglobulin gene minilocus that encodes unrearranged human heavy (p and -y) and K light chain immunoglobulin sequences, together with targeted mutations that inactivate the endogenous p and K chain loci (Lonberg et al., 1994, Nature 368: 856-859). Accordingly, the mice exhibit reduced expression of mouse IgM or K and 15 in response to immunization, the introduced human heavy and light chain transgenes, undergo class switching and somatic mutation to generate high affinity human IgG K monoclonal antibodies (Lonberg et al., supra.; Lonberg and Huszar, 1995, Intern. Rev. Immunol., 13: 65-93; Harding and Lonberg, 1995, Ann. N.Y Acad. Sci 764: 536-546). The preparation of HuMab mice is described in detail in Taylor et al., 1992, Nucleic 20 Acids Research, 20: 6287-6295; Chen et al., 1993, International Immunology 5: 647-656; Tuaillon et al., 1994, J Immunol. 152: 2912-2920; Lonberg et al., 1994, Nature 368: 856 859; Lonberg, 1994, Handbook of Exp. Pharmacology 113: 49-101; Taylor et al., 1994, International Immunology 6: 579-591; Lonberg and Huszar, 1995, Intern. Rev. Immunol. 13: 65-93; Harding and Lonberg, 1995, Ann. N.Y. Acad. Sci. 764: 536-546; Fishwild et 25 al., 1996, Nature Biotechnology 14: 845-851, the contents of all of which are hereby incorporated by reference in their entirety. See further U.S. Patent Nos. 5,545,806; 5,569,825; 5,625,126; 5,633,425; 5,789,650; 5,877,397; 5,661,016; 5,814,318; 5,874,299; and 5,770,429; all to Lonberg and Kay, as well as U.S. Patent No. 5,545,807 to Surani et al.; International Publication Nos. WO 93/1227, published June 24, 1993; WO 92/22646, 30 published December 23, 1992; WO 92/03918, published March 19, 1992, the disclosures of all of which are hereby incorporated by reference in their entirety. Alternatively, the 36 WO 03/086289 PCT/US03/10749 HCo7 and HCol2 transgenic mice strains described in the Examples below can be used to generate human anti-OPGL antibodies. According to certain embodiments, fully human monoclonal antibodies specific for OPGL are produced as follows. Transgenic mice containing human immunoglobulin 5 genes are immunized with the antigen of interest. Lymphatic cells (such as B-cells) from the mice that express antibodies are obtained. Such recovered cells are fused with a myeloid-type cell line to prepare immortal hybridoma cell lines, and such hybridoma cell lines are screened and selected to identify hybridoma cell lines that produce antibodies specific to the antigen of interest. In certain embodiments, the production of a hybridoma 10 cell line that produces antibodies specific to OPGL is provided. In certain embodiments of the invention, the antibodies bind to OPGL with a dissociation constant (Kd) of less than 10~8 M. In certain embodiments, the antibodies of the invention bind to OPGL with a Kd of between approximately 10- M and l010 M. In certain embodiments, the antibodies of the invention are of the IgG isotype. In 15 certain embodiments of the invention, the antibodies comprise a human kappa light chain and a human IgGi heavy chain. In certain embodiments, nucleic acid encoding the heavy and light chains comprising the antibodies of the invention were cloned for expression in mammalian cells. In certain embodiments, the variable regions of the antibodies are ligated to a constant region other than the constant region for the IgG 1 isotype. 20 In certain embodiments, conservative modifications to the heavy and light chains of anti-OPGL antibody (and corresponding modifications to the encoding nucleic acids) will produce anti-OPGL antibodies having functional and biochemical characteristics similar to those of anti-OPGL antibody. In contrast, substantial modifications in the functional and/or biochemical characteristics of anti-OPGL antibody may be achieved by 25 creating substitutions in the amino acid sequence of the heavy and light chains that differ significantly in their effect on maintaining (a) the structure of the molecular backbone in the area of the substitution, for example, as a sheet or helical conformation, (b) the charge or hydrophobicity of the molecule at the target site, or (c) the bulkiness of the side chain. For example, a "conservative amino acid substitution" may involve a substitution 30 of a native amino acid residue with a nonnative residue having little or no effect on the polarity or charge of the amino acid residue at that position. Furthermore, any native 37 WO 03/086289 PCT/US03/10749 residue in the polypeptide may also be substituted with alanine, as has been previously described for "alanine scanning mutagenesis." Desired amino acid substitutions (whether conservative or non-conservative) can be determined by those skilled in the art at the time such substitutions are desired. In 5 certain embodiments, amino acid substitutions can be used to identify important residues of anti-OPGL antibody, or to increase or decrease the affinity of the anti-OPGL antibodies described herein. In alternative embodiments, antibodies of the present invention can be expressed in cell lines other than hybridoma cell lines. In these embodiments, sequences encoding 10 particular antibodies can be used for transformation of a suitable mammalian host cell. According to these embodiments, transformation can be by any known method for introducing polynucleotides into a host cell, including, for example packaging the polynucleotide in a virus (or into a viral vector) and transducing a host cell with the virus (or vector) or by transfection procedures known in the art, as exemplified by U.S. Pat. 15 Nos. 4,399,216, 4,912,040, 4,740,461, and 4,959,455 (which patents are hereby incorporated herein by reference for any purpose). Generally, the transformation procedure used may depend upon the host to be transformed. Methods for introduction of heterologous polynucleotides into mammalian cells are well known in the art and include, but are not limited to, dextran-mediated transfection, calcium phosphate precipitation, 20 polybrene mediated transfection, protoplast fusion, electroporation, encapsulation of the polynucleotide(s) in liposomes, mixing nucleic acid with positively-charged lipids, and direct microinjection of the DNA into nuclei. A nucleic acid molecule encoding the amino acid sequence of a heavy chain constant region, a heavy chain variable region, a light chain constant region, or a light 25 chain variable region of an OPGL antibody of the invention is inserted into an appropriate expression vector using standard ligation techniques. In a preferred embodiment, the anti-OPGL antibody heavy chain or light chain constant region is appended to the C terminus of the appropriate variable region and is ligated into an expression vector. The vector is typically selected. to be functional in the particular host cell employed (i.e., the 30 vector is compatible with the host cell machinery such that amplification of the gene and/or expression of the gene can occur). For a review of expression vectors, see METH. ENZ. 185 (Goeddel, ed.), 1990, Academic Press.Typically, expression vectors used in 38 WO 03/086289 PCT/US03/10749 any of the host cells contain sequences for plasmid maintenance and for cloning and expression of exogenous nucleotide sequences. Such sequences, collectively referred to as "flanking sequences" in certain embodiments will typically include one or more of the following nucleotide sequences: a promoter, one or more enhancer sequences, an origin 5 of replication, a transcriptional termination sequence, a complete intron sequence containing a donor and acceptor splice site, a sequence encoding a leader sequence for polypeptide secretion, a ribosome binding site, a polyadenylation sequence, a polylinker region for inserting the nucleic acid encoding the polypeptide to be expressed, and a selectable marker element. Each of these sequences is discussed below. 10 Optionally, the vector may contain a "tag"-encoding sequence, i.e., an oligonucleotide molecule located at the 5' or 3' end of the OPGL polypeptide coding sequence; the oligonucleotide sequence encodes polyHis (such as hexaHis), or another "tag" such as FLAG, HA (hemaglutinin influenza virus), or nyc, for which commercially available antibodies exist. This tag is typically fused to the polypeptide upon expression 15 of the polypeptide, and can serve as a means for affinity purification or detection of the OPGL antibody from the host cell. Affinity purification can be accomplished, for example, by column chromatography using antibodies against the tag as an affinity matrix. Optionally, the tag can subsequently be removed from the purified OPGL polypeptide by various means such as using certain peptidases for cleavage. 20 Flanking sequences may be homologous (i.e., from the same species and/or strain as the host cell), heterologous (i.e., from a species other than the host cell species or strain), hybrid (i.e., a combination of flanking sequences from more than one source), synthetic or native. As such, the source of a flanking sequence may be any prokaryotic or eukaryotic organism, any vertebrate or invertebrate organism, or any plant, provided that 25 the flanking sequence is functional in, and can be activated by, the host cell machinery. Flanking sequences useful in the vectors of this invention may be obtained by any of several methods well known in the art. Typically, flanking sequences useful herein will have been previously identified by mapping and/or by restriction endonuclease digestion and can thus be isolated from the proper tissue source using the appropriate 30 restriction endonucleases. In some cases, the full nucleotide sequence of a flanking sequence may be known. Here, the flanking sequence may be synthesized using the methods described herein for nucleic acid synthesis or cloning. 39 WO 03/086289 PCT/US03/10749 Whether all or only a portion of the flanking sequence is known, it may be obtained using polymerase chain reaction (PCR) and/or by screening a genomic library with a suitable probe such as an oligonucleotide and/or flanking sequence fragment from the same or another species. Where the flanking sequence is not known, a fragment of 5 DNA containing a flanking sequence may be isolated from a larger piece of DNA that may contain, for example, a coding sequence or even another gene or genes. Isolation may be accomplished by restriction endonuclease digestion to produce the proper DNA fragment followed by isolation using agarose gel purification, Qiagen* column chromatography (Chatsworth, CA), or other methods known to the skilled artisan. The 10 selection of suitable enzymes to accomplish this purpose will be readily apparent to one of ordinary skill in the art. An origin of replication is typically a part of prokaryotic expression vectors, particularly those purchased commercially, and the origin aids in the amplification of the vector in a host cell. If the vector of choice does not contain an origin of replication site, 15 one may be chemically synthesized based on a known sequence, and ligated into the vector. For example, the origin of replication from the plasmid pBR322 (New England Biolabs, Beverly, MA) is suitable for most gram-negative bacteria and various origins (e.g., SV40, polyoma, adenovirus, vesicular stomatitus virus (VSV), or papillomaviruses such as HPV or BPV) are useful for cloning vectors in mammalian cells. Generally, the 20 origin of replication component is not needed for mammalian expression vectors (for example, the SV40 origin is often used only because it contains the early promoter). A transcription termination sequence is typically located 3' of the end of a polypeptide-coding region and serves to terminate transcription. Usually, a transcription termination sequence in prokaryotic cells is a G-C rich fragment followed by a poly-T 25 sequence. While the sequence is easily cloned from a library or even purchased commercially as part of a vector, it can also be readily synthesized using methods for nucleic acid synthesis such as those described herein. A selectable marker gene element encodes a protein necessary for the survival and growth of a host cell grown in a selective culture medium. Typical selection marker 30 genes encode proteins that (a) confer resistance to antibiotics or other toxins, e.g., ampicillin, tetracycline, or kanamycin for prokaryotic host cells; (b) complement auxotrophic deficiencies of the cell; or (c) supply critical nutrients not available from 40 WO 03/086289 PCT/US03/10749 complex media. Preferred selectable markers are the kanamycin resistance gene, the ampicillin resistance gene, and the tetracycline resistance gene. A bacterial neomycin resistance gene can also be used for selection in both prokaryotic and eukaryotic host cells. 5 Other selection genes can be used to amplify the gene that will be expressed. Amplification is a process whereby genes that cannot in single copy be expressed at high enough levels to permit survival and growth of cells under certain selection conditions are reiterated in tandem within the chromosomes of successive generations of recombinant cells. Examples of suitable amplifiable selectable markers for mammalian cells include 10 dihydrofolate reductase (DHFR) and promoterless thymidine kinase. In the use of these markers mammalian cell transformants are placed under selection pressure wherein only the transformants are uniquely adapted to survive by virtue of the selection gene present in the vector. Selection pressure is imposed by culturing the transformed cells under conditions in which the concentration of selection agent in the medium is successively 15 increased, thereby leading to the amplification of both the selectable gene and the DNA that encodes another gene, such as an antibody that binds to OPGL polypeptide. As a result, increased quantities of a polypeptide such as an anti-OPGL antibody are synthesized from the amplified DNA.A ribosome-binding site is usually necessary for translation initiation of mRNA and is characterized by a Shine-Dalgarno sequence 20 (prokaryotes) or a Kozak sequence (eukaryotes). The element is typically located 3' to the promoter and 5' to the coding sequence of the polypeptide to be expressed. In some cases, for example where glycosylation is desired in a eukaryotic host cell expression system, various presequences can be manipulated to improve glycosylation or yield. For example, the peptidase cleavage site of a particular signal peptide can be 25 altered, or pro-sequences added, which also may affect glycosylation. The final protein product may have, in the -1 position (relative to the first amino acid of the mature protein) one or more additional amino acids incident to expression, which may not have been totally removed. For example, the final protein product may have one or two amino acid residues found in the peptidase cleavage site, attached to the amino-terminus. 30 Alternatively, use of some enzyme cleavage sites may result in a slightly truncated yet active form of the desired polypeptide, if the enzyme cuts at such area within the mature polypeptide. 41 WO 03/086289 PCT/US03/10749 The expression and cloning vectors of the present invention will typically contain a promoter that is recognized by the host organism and operably linked to nucleic acid encoding the anti-OPGL antibody. Promoters are untranscribed sequences located upstream (i.e., 5') to the start codon of a structural gene (generally within about 100 to 5 1000 bp) that control transcription of the structural gene. Promoters are conventionally grouped into one of two classes: inducible promoters and constitutive promoters. Inducible promoters initiate increased levels of transcription from DNA under their control in response to some change in culture conditions, such as the presence or absence of a nutrient or a change in temperature. Constitutive promoters, on the other hand, 10 initiate continual gene product production; that is, there is little or no experimental control over gene expression. A large number of promoters, recognized by a variety of potential host cells, are well known. A suitable promoter is operably linked to the DNA encoding anti-OPGL antibody by removing the promoter from the source DNA by restriction enzyme digestion or amplifying the promoter by polymerase chain reaction and inserting 15 the desired promoter sequence into the vector. Suitable promoters for use with yeast hosts are also well known in the art. Yeast enhancers are advantageously used with yeast promoters. Suitable promoters for use with mammalian host cells are well known and include, but are not limited to, those obtained from the genomes of viruses such as polyoma virus, fowlpox virus, adenovirus (such as 20 Adenovirus 2), bovine papilloma virus, avian sarcoma virus, cytomegalovirus, retroviruses, hepatitis-B virus and most preferably Simian Virus 40 (SV40). Other suitable mammalian promoters include heterologous mammalian promoters, for example, heat-shock promoters and the actin promoter. Additional promoters that may be of interest include, but are not limited to: the 25 SV40 early promoter region (Bernoist and Chambon, 1981, Nature 290: 304-10); the CMV promoter; the promoter contained in the 3' long terminal repeat of Rous sarcoma virus (Yamamoto, et al., 1980, Cell 22: 787-97); the herpes thymidine kinase promoter (Wagner et al., 1981, Proc. Natl. Acad. Sci. U.S.A. 78: 1444-45); the regulatory sequences of the metallothionine gene (Brinster et al., 1982, Nature 296: 39-42); prokaryotic 30 expression vectors such as the beta-lactamase promoter (Villa-Kamaroff et al., 1978, Proc. Natl. Acad. Sci. US.A., 75: 3727-31); or the tac promoter (DeBoer et al., 1983, Proc. Natl. Acad. Sci. U.S.A. 80: 21-25). Also of interest are the following animal 42 WO 03/086289 PCT/US03/10749 transcriptional control regions, which exhibit tissue specificity and have been utilized in transgenic animals: the elastase I gene control region that is active in pancreatic acinar cells (Swift et al., 1984, Cell 38: 639-46; Ornitz et al., 1986, Cold Spring Harbor Symp. Quant. Biol. 50: 399-409; MacDonald, 1987, Hepatology 2: 425-515); the insulin gene 5 control region that is active in pancreatic beta cells (Hanahan, 1985, Nature 315: 115-22); the mouse mammary tumor virus control region that is active in testicular, breast, lymphoid and mast cells (Leder et al., 1986, Cell 45: 485-95); the albumin gene control region that is active in liver (Pinkert et al., 1987, Genes and Devel. 1: 268-76); the alpha feto-protein gene control region that is active in liver (Krumlauf et al., 1985, Mol. Cell. 10 Biol. 5: 1639-48; Hammer et al., 1987, Science 235: 53-58); the alpha 1-antitrypsin gene control region that is active in the liver (Kelsey et al., 1987, Genes and Devel. 1: 161-71); the beta-globin gene control region that is active in myeloid cells (Mogram et al., 1985, Nature 315: 338-40; Kollias et al., 1986, Cell 46: 89-94); the myelin basic protein gene control region that is active in oligodendrocyte cells in the brain (Readhead et al., 1987, 15 Cell 48: 703-12); the myosin light chain-2 gene control region that is active in skeletal muscle (Sani, 1985, Nature 314: 283-86); the gonadotropic releasing hormone gene control region that is active in the hypothalamus (Mason et al., 1986, Science 234: 1372 78); and most particularly the immunoglobulin gene control region that is active in lymphoid cells (Grosschedl et al., 1984, Cell 38: 647-58; Adames et al., 1985, Nature 20 318: 533-38; Alexander et al., 1987, Mol. Cell Biol. 7: 1436-44). An enhancer sequence may be inserted into the vector to increase the transcription of a nucleic acid encoding an anti-OPGL antibody of the present invention by higher eukaryotes. Enhancers are cis-acting elements of DNA, usually about 10-300 bp in length, that act on promoters to increase transcription. Enhancers are relatively 25 orientation and position independent. They have been found 5' and 3' to the transcription unit. Several enhancer sequences available from mammalian genes are known (e.g., globin, elastase, albumin, alpha-feto-protein and insulin). Typically, however, an enhancer from a virus will be used. The SV40 enhancer, the cytomegalovirus early promoter enhancer, the polyoma enhancer, and adenovirus enhancers are exemplary 30 enhancing elements for the activation of eukaryotic promoters. While an enhancer may be spliced into the vector at a position 5' or 3' to a nucleic acid molecule, it is typically located at a site 5' from the promoter. 43 WO 03/086289 PCT/US03/10749 Expression vectors of the invention may be constructed from a convenient starting vector such as a commercially available vector. Such vectors may or may not contain all of the desired flanking sequences. Where one or more of the flanking sequences described herein are not already present in the vector, they may be individually obtained 5 and ligated into the vector. Methods used for obtaining each of the flanking sequences are well known to one skilled in the art. After the vector has been constructed and a nucleic acid molecule encoding an anti-OPGL antibody has been inserted into the proper site of the vector, the completed vector may be inserted into a suitable host cell for amplification and/or polypeptide 10 expression. The transformation of an expression vector for an anti-OPGL antibody into a selected host cell may be accomplished by well-known methods including methods such as transfection, infection, calcium chloride, electroporation, microinjection, lipofection, DEAE-dextran method, or other known techniques. The method selected will in part be a function of the type of host cell to be used. These methods and other suitable methods 15 are well known to the skilled artisan, and are set forth, for example, in Sambrook et al., supra. A host cell, when cultured under appropriate conditions, synthesizes an anti OPGL antibody that can subsequently be collected from the culture medium (if the host cell secretes it into the medium) or directly from the host cell producing it (if it is not 20 secreted). The selection of an appropriate host cell will depend upon various factors, such as desired expression levels, polypeptide modifications that are desirable or necessary for activity (such as glycosylation or phosphorylation) and ease of folding into a biologically active molecule. Mammalian cell lines available as hosts for expression are well known in the art 25 and include, but are not limited to, many immortalized cell lines available from the American Type Culture Collection (ATCC), such as Chinese hamster ovary (CHO) cells, HeLa cells, baby hamster kidney (BHK) cells, monkey kidney cells (COS), human hepatocellular carcinoma cells (e.g., Hep G2), and a number of other cell lines. In certain embodiments, cell lines may be selected through determining which cell lines have high 30 expression levels and produce antibodies with constitutive OPGL binding properties. In another embodiment, a cell line from the B cell lineage that does not make its own antibody but has a capacity to make and secrete a heterologous antibody can be selected. 44 WO 03/086289 PCT/US03/10749 Antibodies of the invention are useful for detecting OPGL in biological samples and identification of cells or tissues that produce the protein. In certain embodiments, antibodies that bind to OPGL and block interaction with other binding compounds may have therapeutic use in modulating osteoclast differentiation and bone resorption. In 5 certain embodiments, antibodies to OPGL may block OPGL binding to ODAR (RANK), which may result in a block in the signal transduction cascade and loss of NF-kB mediated transcription activation. Assays for measuring NF-kB-mediated transcription activation using, e.g., a luciferase reporter assay, are known to those skilled in the art. In certain embodiments, antibodies to OPGL may be useful in treatment of bone 10 diseases such as osteoporosis and Paget's disease. In certain embodiments, antibodies can be tested for binding to OPGL in the absence or presence of OPG and examined for their ability to inhibit OPGL-mediated osteoclastogenesis and/or bone resorption. Anti-OPGL antibodies of the invention can be administered alone or in combination with other therapeutic agents, in particular, in combination with other cancer 15 therapy agents. Such agents generally include radiation therapy or chemotherapy. Chemotherapy, for example, can involve treatment with one or more of the following: anthracyclines, taxol, tamoxifene, doxorubicin, 5-fluorouracil, and other drugs known to the skilled worker. In addition, anti-OPGL antibodies can be administered to patients in combination 20 with antibodies that bind to tumor cells and induce a cytotoxic and/or cytostatic effect on tumor growth. Examples of such antibodies include those that bind to cell surface proteins Her2, CDC20, CDC33, mucin-like glycoprotein and epidermal growth factor receptor (EGFR) present on tumor cells and induce a cytostatic and/or cytotoxic effect on tumor cells displaying these proteins. Examples of such antibodies include HERCEPTIN 25 for treatment of breast cancer and RITUXAN for the treatment of non-Hodgkin's lymphoma. Also, combination therapy can include as cancer therapy agents polypeptides that selectively induce apoptosis in tumor cells, such as the TNF-related polypeptide TRAIL. Anti-OPGL or antigen binding fragments of the invention can be administered prior to, concurrent with, or subsequent to treatment with a cancer therapy agent. Anti 30 OPGL antibodies can be administered prophylactically to prevent or mitigate the onset of loss of bone mass by metastatic cancer or can be given for the treatment of an existing condition of loss of bone mass due to metastasis. 45 WO 03/086289 PCT/US03/10749 Anti-OPGL antibodies of the invention may be used to prevent and/or treat the growth of tumor cells in bone. Cancer that metastasizes to bone can spread readily as tumor cells stimulate osteoclasts to resorb the internal bone matrix. Treatment with an anti-OPGL antibody will maintain bone density by inhibiting resorption and decrease the 5 likelihood of tumor cells spreading throughout the skeleton. Any cancer that metastasizes to bone may be prevented and/or treated with an anti-OPGL antibody. In one embodiment, multiple myeloma may be prevented and/or treated with an anti-OPGL antibody or antigen binding fragment thereof. Multiple myeloma is localized to bone. Affected patients typically exhibit a loss of bone mass due to increased 10 osteoclast activation in localized regions. Myeloma cells either directly or indirectly produce OPGL, which in turn activates osteoclasts resulting in local bone lysis surrounding the myeloma cells embedded in bone marrow spaces. The normal osteoclasts adjacent to the myeloma cell in turn produce IL-6, leading to growth and proliferation of myeloma cells. Myeloma cells expand in a clonal fashion and occupy 15 bone spaces that are being created by inappropriate bone resorption. Treatment of an animal with an anti-OPGL antibody blocks activation of osteoclasts which in turn leads to a decrease in IL-6 production by osteoclasts, and a suppression of mycloma all growth and/or proliferation. Anti-OPGL antibodies may be used alone for the treatment of the above 20 referenced conditions resulting in loss of bone mass or in combination with a therapeutically effective amount of a bone growth promoting (anabolic) agent or a bone anti-resorptive agent including but not limited to bone morphogenic factors designated BMP- 1 to BMP- 12, transforming growth factor-# and TGF-# family members, fibroblast growth factors FGF-1 to FGF-10, interleukin-1 inhibitors, TNFa inhibitors, parathyroid 25 hormone, E series prostaglandins, bisphosphonates and bone-enhancing minerals such as fluoride and calcium. Anabolic agents include parathyroid hormone and insulin-like growth factor (IGF), wherein the latter agent is preferably complexed with an IGF binding protein. Preferred embodiments also include the combination of an anti-OPGL antibody with an interluekin-1 (IL-1) receptor antagonist or an anti-OPGL antibody with 30 a soluble TNF receptor, such as soluble TNF receptor-1 or soluble TNF receptor-2. An exemplary IL-1 receptor antagonist is described in W089/11540 and an exemplary soluble TNF receptor-1 is described in W098/01555. 46 WO 03/086289 PCT/US03/10749 In preferred embodiments, the invention provides pharmaceutical compositions comprising a therapeutically effective amount of the antibodies of the invention together with a pharmaceutically acceptable diluent, carrier, solubilizer, emulsifier, preservative and/or adjuvant. In certain embodiments, pharmaceutical compositions comprising a 5 therapeutically effective amount of anti-OPGL antibodies are provided. Acceptable formulation materials preferably are nontoxic to recipients at the dosages and concentrations employed. The pharmaceutical composition may contain formulation materials for modifying, maintaining or preserving, for example, the pH, osmolarity, viscosity, clarity, color, isotonicity, odor, sterility, stability, rate of dissolution 10 or release, adsorption or penetration of the composition. Suitable formulation materials include, but are not limited to, amino acids (such as glycine, glutamine, asparagine, arginine or lysine); antimicrobials; antioxidants (such as ascorbic acid, sodium sulfite or sodium hydrogen-sulfite); buffers (such as borate, bicarbonate, Tris-HCl, citrates, phosphates or other organic acids); bulking agents (such as mannitol or glycine); 15 chelating agents (such as ethylenediamine tetraacetic acid (EDTA)); complexing agents (such as caffeine, polyvinylpyrrolidone, beta-cyclodextrin or hydroxypropyl-beta cyclodextrin); fillers; monosaccharides; disaccharides; and other carbohydrates (such as glucose, mannose or dextrins); proteins (such as serum albumin, gelatin or immunoglobulins); coloring, flavoring and diluting agents; emulsifying agents; 20 hydrophilic polymers (such as polyvinylpyrrolidone); low molecular weight polypeptides; salt-forming counterions (such as sodium); preservatives (such as benzalkonium chloride, benzoic acid, salicylic acid, thimerosal, phenethyl alcohol, methylparaben, propylparaben, chlorhexidine, sorbic acid or hydrogen peroxide); solvents (such as glycerin, propylene glycol or polyethylene glycol); sugar alcohols (such as mannitol or sorbitol); suspending 25 agents; surfactants or wetting agents (such as pluronics, PEG, sorbitan esters, polysorbates such as polysorbate 20, polysorbate 80, triton, tromethamine, lecithin, cholesterol, tyloxapal); stability enhancing agents (such as sucrose or sorbitol); tonicity enhancing agents (such as alkali metal halides, preferably sodium or potassium chloride, mannitol sorbitol); delivery vehicles; diluents; excipients and/or pharmaceutical 30 adjuvants. (REMINGTON'S PHARMACEUTICAL SCIENCES, 18 th Edition, (A.R. Gennaro, ed.), 1990, Mack Publishing Company. 47 WO 03/086289 PCT/US03/10749 In certain embodiments, optimal pharmaceutical compositions will be determined by one skilled in the art depending upon, for example, the intended route of administration, delivery format and desired dosage. See, for example, REMINGTON'S PHARMACEUTICAL SCIENCES, ibid. Such compositions may influence the physical 5 state, stability, rate of in vivo release and rate of in vivo clearance of the antibodies of the invention. The primary vehicle or carrier in a pharmaceutical composition may be either aqueous or non-aqueous in nature. For example, a suitable vehicle or carrier may be water for injection, physiological saline solution or artificial cerebrospinal fluid, possibly 10 supplemented with other materials common in compositions for parenteral administration. Neutral buffered saline or saline mixed with serum albumin are further exemplary vehicles. Pharmaceutical compositions can comprise Tris buffer of about pH 7.0-8.5, or acetate buffer of about pH 4.0-5.5, which may further include sorbitol or a suitable substitute therefor. Anti-OPGL antibody compositions may be prepared for storage by 15 mixing the selected composition having the desired degree of purity with optional formulation agents (REMINGTON'S PHARMACEUTICAL SCIENCES, ibid.) in the form of a lyophilized cake or an aqueous solution. Further, the anti-OPGL antibody product may be formulated as a lyophilizate using appropriate excipients such as sucrose. Formulation components are present in concentrations that are acceptable to the 20 site of administration. Buffers are advantageously used to maintain the composition at physiological pH or at a slightly lower pH, typically within a pH range of from about 5 to about 8. The pharmaceutical compositions of the invention can be delivered parenterally. When parenteral administration is contemplated, the therapeutic compositions for use in 25 this invention may be in the form of a pyrogen-free, parenterally acceptable aqueous solution comprising the desired anti-OPGL antibody in a pharmaceutically acceptable vehicle. A particularly suitable vehicle for parenteral injection is sterile distilled water in which the anti-OPGL antibody is formulated as a sterile, isotonic solution, properly preserved. Preparation can involve the formulation of the desired molecule with an agent, 30 such as injectable microspheres, bio-erodible particles, polymeric compounds (such as polylactic acid or polyglycolic acid), beads or liposomes, that may provide controlled or sustained release of the product which may then be delivered via a depot injection. 48 WO 03/086289 PCT/US03/10749 Formulation with hyaluronic acid has the effect of promoting sustained duration in the circulation. Implantable drug delivery devices may be used to introduce the desired molecule. The compositions may be selected for inhalation. In these embodiments, an anti 5 OPGL antibody is formulated as a dry powder for inhalation, or anti-OPGL antibody inhalation solutions may also be formulated with a propellant for aerosol delivery, such as by nebulization. Pulmonary administration is further described in PCT Application No. PCT/US94/001875, which describes pulmonary delivery of chemically modified proteins. The pharmaceutical compositions of the invention can be delivered through the 10 digestive tract, such as orally. The preparation of such pharmaceutically acceptable compositions is within the skill of the art. Anti-OPGL antibodies that are administered in this fashion may be formulated with or without those carriers customarily used in the compounding of solid dosage forms such as tablets and capsules. A capsule may be designed to release the active portion of the formulation at the point in the gastrointestinal 15 tract when bioavailability is maximized and pre-systemic degradation is minimized. Additional agents can be included to facilitate absorption of the anti-OPGL antibody. Diluents, flavorings, low melting point waxes, vegetable oils, lubricants, suspending agents, tablet disintegrating agents, and binders may also be employed. A pharmaceutical composition may involve an effective quantity of anti-OPGL 20 antibodies in a mixture with non-toxic excipients that are suitable for the manufacture of tablets. By dissolving the tablets in sterile water, or another appropriate vehicle, solutions may be prepared in unit-dose form. Suitable excipients include, but are not limited to, inert diluents, such as calcium carbonate, sodium carbonate or bicarbonate, lactose, or calcium phosphate; or binding agents, such as starch, gelatin, or acacia; or lubricating 25 agents such as magnesium stearate, stearic acid, or talc. Additional pharmaceutical compositions will be evident to those skilled in the art, including formulations involving anti-OPGL antibodies in sustained- or controlled delivery formulations. Techniques for formulating a variety of other sustained- or controlled-delivery means, such as liposone carriers, bio-erodible microparticles or 30 porous beads and depot injections, are also known to those skilled in the art. See, for example, PCT Application No. PCT/US93/00829, which describes the controlled release of porous polymeric microparticles for the delivery of pharmaceutical compositions. 49 WO 03/086289 PCT/US03/10749 Sustained-release preparations may include semipermeable polymer matrices in the form of shaped articles, e.g. films, or microcapsules, polyesters, hydrogels, polylactides (U.S. 3,773,919 and EP 058,481), copolymers of L-glutamic acid and gamma ethyl-L-glutamate (Sidman et al., 1983, Biopolymers 22: 547-556), poly (2-hydroxyethyl-methacrylate) 5 (Langer et al., 1981, J Bioied. Mater. Res. 15: 167-277) and Langer, 1982, Chem. Tech. 12: 98-105), ethylene vinyl acetate (Langer et al., ibid.) or poly-D(-)-3-hydroxybutyric acid (EP 133,988). Sustained release compositions may also include liposomes, which can be prepared by any of several methods known in the art. See e.g., Eppstein et al., 1985, Proc. Natl. Acad. Sci. USA 82: 3688-3692; EP 036,676; EP 088,046 and EP 10 143,949. The pharmaceutical composition to be used for in vivo administration typically is sterile. In certain embodiments, this may be accomplished by filtration through sterile filtration membranes. In certain embodiments, where the composition is lyophilized, sterilization using this method may be conducted either prior to or following 15 lyophilization and reconstitution. In certain embodiments, the composition for parenteral administration may be stored in lyophilized form or in a solution. In certain embodiments, parenteral compositions generally are placed into a container having a sterile access port, for example, an intravenous solution bag or vial having a stopper pierceable by a hypodermic injection needle. 20 Once the pharmaceutical composition of the invention has been formulated, it may be stored in sterile vials as a solution, suspension, gel, emulsion, solid, or as a dehydrated or lyophilized powder. Such formulations may be stored either in a ready-to-use form or in a form (e.g., lyophilized) that is reconstituted prior to administration. The invention also provides kits for producing a single-dose administration unit. 25 The kits of the invention may each contain both a first container having a dried protein and a second container having an aqueous formulation, including for example single and multi-chambered pre-filled syringes (e.g., liquid syringes, lyosyringes or needle-free syringes). The effective amount of an anti-OPGL antibody pharmaceutical composition to be 30 employed therapeutically will depend, for example, upon the therapeutic context and objectives. One skilled in the art will appreciate that the appropriate dosage levels for treatment, according to certain embodiments, will thus vary depending, in part, upon the 50 WO 03/086289 PCT/US03/10749 molecule delivered, the indication for which the anti-OPGL antibody is being used, the route of administration, and the size (body weight, body surface or organ size) and/or condition (the age and general health) of the patient. In certain embodiments, the clinician may titer the dosage and modify the route of administration to obtain the optimal 5 therapeutic effect. Typical dosages range from about 0.1 jig/kg to up to about 30 mg/kg or more, depending on the factors mentioned above. In certain embodiments, the dosage may range from 0.1 jpg/kg up to about 30 mg/kg; or 1 Rg/kg up to about 30 mg/kg; or 5 jig/kg up to about 30 mg/kg. Dosing frequency will depend upon the pharmacokinetic parameters of the anti 10 OPGL antibody in the formulation used. For example, a clinician will administer the composition until a dosage is reached that achieves the desired effect. The composition may therefore be administered as a single dose, or as two or more doses (which may or may not contain the same amount of the desired molecule) over time, or as a continuous infusion via an implantation device or catheter. Further refinement of the appropriate 15 dosage is routinely made by those of ordinary skill in the art and is within the ambit of tasks routinely performed by them. Appropriate dosages may be ascertained through use of appropriate dose-response data. Administration routes for the pharmaceutical compositions of the invention include orally, through injection by intravenous, intraperitoneal, intracerebral (intra 20 parenchymal), intracerebroventricular, intramuscular, intra-ocular, intraarterial, intraportal, or intralesional routes; by sustained release systems or by implantation devices. The pharmaceutical compositions may be administered by bolus injection or continuously by infusion, or by implantation device. The pharmaceutical composition also can be administered locally via implantation of a membrane, sponge or another 25 appropriate material onto which the desired molecule has been absorbed or encapsulated. Where an implantation device is used, the device may be implanted into any suitable tissue or organ, and delivery of the desired molecule may be via diffusion, timed-release bolus, or continuous administration. It also may be desirable to use anti-OPGL antibody pharmaceutical compositions 30 according to the invention ex vivo. In such instances, cells, tissues or organs that have been removed from the patient are exposed to anti-OPGL antibody pharmaceutical 51 WO 03/086289 PCT/US03/10749 compositions after which the cells, tissues and/or organs are subsequently implanted back into the patient. In particular, anti-OPGL antibody can be delivered by implanting certain cells that have been genetically engineered, using methods such as those described herein, to 5 express and secrete the polypeptide. In certain embodiments, such cells may be animal or human cells, and may be autologous, heterologous, or xenogeneic, or may be immortalized. In certain embodiments, the cells may be immortalized. In other embodiments, in order to decrease the chance of an immunological response, the cells may be encapsulated to avoid infiltration of surrounding tissues. In further embodiments, 10 the encapsulation materials are typically biocompatible, semi-permeable polymeric enclosures or membranes that allow the release of the protein product(s) but prevent the destruction of the cells by the patient's immune system or by other detrimental factors from the surrounding tissues. 15 EXAMPLES The following examples, including the experiments conducted and results achieved are provided for illustrative purposes only and are not to be construed as limiting the present invention. 20 Example 1 Production of Human Monoclonal Antibodies Against OPGL Transgenic HuMab Mice Fully human monoclonal antibodies to OPGL were prepared using HCo7, HCo12, and HCo7+HCol2 strains of transgenic mice, each of which expresses human antibody 25 genes. In each of these mouse strains, the endogenous mouse kappa light chain gene has been homozygously disrupted (as described in Chen et al., 1993, EMBO J. 12: 811-820) and the endogenous mouse heavy chain gene has been homozygously disrupted as described in Example 1 of PCT Publication WO 01/09187 (incorporated by reference). Each of these mouse strains carries a human kappa light chain transgene, KCo5 (as 30 described in Fishwild et al., 1996, Nature Biotechnology 14: 845-851). The HCo7 strain 52 WO 03/086289 PCT/US03/10749 carries the HCo7 human heavy chain transgene as described in U.S. Patent Nos. 5,545,806; 5,625,825; and 5,545,807 (incorporated by reference). The HCo12 strain carries the HCo12 human heavy chain transgene as described in Example 2 of PCT Publication WO 01/09187 (incorporated by reference). The HCo7+HCol2 strain carries 5 both the HCo7 and the HCol2 heavy chain transgenes and is hemizygous for each transgene. All of these strains are referred to herein as HuMab mice. HuMab Immunizations: To generate fully human monoclonal antibodies to OPGL, HuMab mice were 10 immunized with purified recombinant OPGL derived from E. coli or CHO cells as antigen. General immunization schemes for HuMab mice are described in Lonberg et al. 91994, Nature 368: 856-859, Fishwild et al., ibid., and PCT Publication WO 98/24884 (the teachings of each of which are incorporated by reference). Mice were 6-16 weeks of age upon the first infusion of antigen. A purified recombinant preparation (50-100 pg) of 15 OPGL antigen (e.g., purified from transfected E. coli or CHO cells expressing OPGL) was used to immunize the HuMab mice intraperitoneally (IP) or subcutaneously (Sc). Immunizations of HuMab transgenic mice were performed twice using antigen in complete Freund's adjuvant, followed by 2-4 weeks IP immunization (up to a total of 9 immunizations) with the antigen in incomplete Freund's adjuvant. Several dozen mice 20 were immunized for each antigen. A total of 136 HuMab mice of the HCo7, HCo12, and HCo7+HCo12 strains were immunized with OPGL. The immune response was monitored by retroorbital bleeds. To select HuMab mice producing antibodies that bound OPGL, sera from immunized mice was tested by ELISA as described by Fishwild et al. supra. Briefly, 25 microtiter plates were coated with purified recombinant OPGL from CHO cells or E. coli at 1-2 pIJmL in PBS and 50 pJL/well incubated at 4*C overnight, then blocked with 200 pIJwell with 5% chicken serum in PBS/Tween (0.05%). Dilutions of plasma from OPGL-immunized mice were added to each well and incubated for 1-2 hours at ambient temperature. The plates were washed with PBS/Tween and then incubated with a goat 30 anti-human IgG Fc-specific polyclonal reagent conjugated to horseradish peroxidase (HRP) for 1 hour at room temperature. After washing, the plates were developed with 53 WO 03/086289 PCT/US03/10749 ABTS substrate (Sigma, A-1888, 0.22 mg/mL) and analyzed at OD of 415-495. Mice with sufficient titers of anti-OPGL human immunoglobulin were used to produce monoclonal antibodies as described below. 5 Generation of hybridomas producing human monoclonal antibodies to OPGL Mice were prepared for monoclonal antibody production by boosting with antigen intravenously 2 days before sacrifice, and spleens were removed thereafter. The mouse splenocytes were isolated from the HuMab mice and fused with PEG to a mouse myeloma cell line based upon standard protocols. Typically, 10-20 fusions for each 10 antigen were performed. Briefly, single cell suspensions of splenic lymphocytes from immunized mice were fused to one-quarter the number of P3X63-Ag8.653 nonsecreting mouse myeloma cells (ATCC, CRL 1580) using 50% PEG (Sigma Chemical Co., St. Louis, MO). Cells were plated at approximately x 105 cells/well in flat bottom microtitre plates, followed by 15 about two week incubation in selective medium containing 10% fetal bovine serum, 10% P388D1 (ATCC, CRL TIB-63) conditioned medium and 3-5% origen (IGEN) in DMEM (Mediatech, CRL 10013, with high glucose, L-glutamine and sodium pyruvate) plus 5 mM HEPES, 0.055 mM 2-mercaptoethanol, 50 mg/mL gentamycin and 1x HAT (Sigma, CRL P-7185). After 1-2 weeks, cells were cultured in medium in which the HAT was 20 replaced with HT. The resulting hybridomas were screened for the production of antigen-specific antibodies. Individual wells were screened by ELISA (described above) for human anti OPGL monoclonal IgG antibodies. Once extensive hybridoma growth occurred, medium was monitored usually after 10-14 days. Antibody secreting hybridomas were replated, 25 screened again and, if still positive by ELISA for human IgG, anti-OPGL monoclonal antibodies were subcloned at least twice by limiting dilution. The stable subclones were then cultured in vitro to generate small amounts of antibody in tissue culture medium for characterization. 30 Selection of Human Monoclonal Antibodies that Bind to OPGL 54 WO 03/086289 PCT/US03/10749 An ELISA assay as described above was used to screen for hybridomas that showed positive reactivity with OPGL immunogen. Hybridomas secreting a monoclonal antibody that bound with high avidity to OPGL were subcloned and further characterized. One clone from each hybridoma, which retained the reactivity of parent cells (as 5 determined by ELISA), was chosen for making a 5-10 vial cell bank stored in liquid nitrogen. An isotype-specific ELISA was performed to determine the isotype of the monoclonal antibodies produced as disclosed herein. In these experiments, microtitre plate wells were coated with 50 pL/well of a solution of 1 pg/mL mouse anti-human 10 kappa light chain in PBS and incubated at 4"C overnight. After blocking with 5% chicken serum, the plates were reacted with supernatant from each tested monoclonal antibody and a purified isotype control. Plates were incubated at ambient temperature for 1-2 hours. The wells were then reacted with either human IgG1 or IgG 3 -specific horseradish peroxidase-conjugated goat anti-human polyclonal antisera and plates 15 developed and analyzed as described above. Monoclonal antibodies purified from six hybridoma supernatants that showed significant binding to OPGL as detected by ELISA were further tested for biological activity using in vitro receptor binding assays and human OPGL-dependent in vitro osteoclast forming assays (described in Example 6 below). The antibodies selected were 20 designated 16E1, 2E11, 18B2, 2D8, 22B3, and 9H7. The heavy chain alignment for these anti-OPGL antibodies is shown in Figure 15. The light chain alignment for the anti OPGL antibodies is shown in Figure 16. Non-consensus sequences are shown in bold and are shaded, and complementarity-determining regions (CDRs) are underlined. 25 Example 2 Cloning the 9H7 anti-OPGL Heavy and Light Chains Cloning of the 9H7 anti-OPGL MAb light chain Three anti-OPGL hybridoma light chain cDNAs (9H7, 16E1 and 18B2) were cloned into pDSR19 mammalian cell expression vector. The construction of a plasmid 30 encoding the 9H7 kappa light chain is explicitly described; cloning of the other light chain species was performed using similar procedures. The anti-OPGL-9H7 kappa light 55 WO 03/086289 PCT/US03/10749 chain variable region was obtained using polymerase chain reaction (PCR) amplification methods from first strand cDNA prepared from hybridoma 9H7 total RNA. First strand cDNA was prepared from 9H7 total RNA using a random primer with an extended 5' adapter (5'-GGCCGGATAGGCCTCACNNNNNNT-3', SEQ ID NO: 53) and the 5 materials and methods provided by the Gibco SuperScript II TM Preamplification System for First Strand cDNA Synthesis kit (Catalogue No. 18089-011). The oligonucleotides below were used for the PCR: 5' GeneRacer Tm (Invitrogen) primer (SEQ ID NO: 54): 5'- GGA CAC TGA CAT GGA CTG AAG GAG TA -3'; 10 3' kappa RACE primer, 2310-03 (SEQ ID NO: 55): 5' - GGG GTC AGG CTG GAA CTG AGG- 3'. The amplified DNAs were cloned into pCRII-TOPO (Invitrogen) and the resulting plasmids were sequenced. The kappa chain consensus sequence was used to design primers for PCR amplification of the variable region of the 9H7 kappa chain. To generate 15 the signal sequence, a three-step PCR was performed. First, primers 2669-73 and 2708 53 (set forth below) were used with a 9H7 cDNA light chain clone template. Conditions used for the reaction were: 94 0 C for 1 minute; 94*C for 20 seconds, 42*C for 30 seconds, 74 0 C for 150 seconds for 2 cycles; 94*C for 20 seconds, 56*C for 30 seconds, 74*C for 150 seconds for 25 cycles; and 74*C for 7 minutes with Pfu polymerase and the 20 appropriate buffer and nucleotides. The PCR product was then amplified with primers 2663-07 and 2708-53 followed by amplification with primers 2663-08 and 2708-53. These primers are shown below. 2663-08 (SEQ ID NO: 56) 25 HindIII XbaI Kozak 5'-C AGC AG AAGCTTCTAGA CCACC ATG GAC ATG AGG GTG CCC GCT CAG CTC CTG GG-3'; 2663-07 (SEQ ID NO: 57) 5'-CC GCT CAG CTC CTG GGG CTC CTG CTG CTG TGG CTG AGA GGT 30 GCC AGA T-3'; 2669-73 (SEQ ID NO: 58) 56 WO 03/086289 PCT/US03/10749 5'-G TGG TTG AGA GGT GCC AGA TGT GAA ATT GTG CTG ACC CAG TCT CCA GCC ACC CTG TCT TTG TCT C-3'; 2708-53 (SEQ ID NO: 59) Safl 5 5'-CTT GTC GAC TCA ACA CTC TCC CCT GTT GAA GCT C-3'. The PCR reactions generated a 741 bp fragment encoding 238 amino acid residues (including the 22 amino acid signal sequence) that was purified using a QlAquick PCR Purification kit (Qiagen Cat. No.28104), cut with XbaI and SalI, and Qiagen purified again. This fragment, containing the complete light chain with a 5' Kozak (translational 10 initiation) site and the following signal sequence for mammalian expression: MDMRVPAQLLGLLLLWLRGARC (SEQ ID NO: 60), was ligated into pDSRacl9 to generate plasmid pDSRa19:9H7 kappa (Figure 17). pDSRxl9 has been described previously (see International Application, Publication No. WO 90/14363, which is herein incorporated by reference for any purpose). Briefly, to 15 make pDSRc19, pDSRa2 was modified in the following ways: the sequence containing the transcription termination/polyadenylation signal from the alpha subunit of the bovine pituitary glycoprotein hormome alpha-FSH (follicle-stimulating hormone) was shortened by approximately 1400 base pairs, to 885 base pairs, and ends at the NdeI site after modification; the dihydrofolate reductase (DHFR) promoter contained 209 base pairs, 20 having been shortened from the 5' end by approximately 1 kilobase; and an approximately 550 base pair BglII fragment from the DHFR polyA sequence was deleted. The 9H7 kappa light chain expression clone was sequenced to confirm that it encoded the same peptide that was identified in the 9H7 hybridoma. The final expression vector, pDSRal9:9H7 kappa is 5479 bp and contains the 7 functional regions described 25 in Table 2. Table 2 Plasmid Base Pair Number: 2 to 881 A transcription termination/polyadenylation signal from the a-subunit of the bovine pituitary glycoprotein hormone (a-FSH) (Goodwin, et al., 1983, Nucleic Acids Res. 11:6873-82; Genbank Accession Number X00004) 882 to 2027 A mouse dihydrofolate reductase (DHFR) minigene containing the endogenous mouse DHFR promoter, the cDNA coding sequences, and the DHFR transcription termination/polyadenylation signals (Gasser et al, 1982, Proc. Nat!. Acad. Sci. U. S. A. 19:6522-6; Nunberg et al., 1980, Cell 19:355-64; Setzer et al., 1982, J. Biol. Chem. 57 WO 03/086289 PCT/US03/10749 257:5143-7; McGrogan et al., 1985, J. Biol. Chem. 260:2307-14) 2031 to 3947 pBR322 sequences containing the ampicillin resistance marker gene and the origin for replication of the plasmid in E. coli (Genbank Accession Number JO 1749) 3949 to 4292 An SV40 early promoter, enhancer and origin of replication (Takebe et al., 1988, Mol. Cell Bio. 8:466-72, Genbank Accession Number J02400) 4299 to 4565 A translational enhancer element from the HTLV-1 LTR domain (Seiki et al., 1983, Proc. Natl. Acad. Sci. U S. A. 80:3618-22, Genbank Accession Number J02029) 4574 to 4730 An intron from the SV40 16S, 19S splice donor/acceptor signals (Okayama and Berg, 1983. Mol. Cell Biol. 3:280-9, Genbank Accession Number J02400) 4755 to 5479 The 9H7D4 kappa light chain cDNA between the Xbal and Sall sites Construction of pDSR19:hIgG1 CH A pDSR19: rat variable region/human constant region IgGi plasmid was constructed using a three-piece ligation of a rat variable region sequence, the human 5 constant region (CHI, hinge, CH2, and CH3 domains) and pDSR19. The linear pDSRa19:hIgG1 CH plasmid was prepared by digesting the pDSR19:rat variable region/human constant region IgGi plasmid with restriction enzymes XbaI and BsnBI to remove the coding portion of the rat variable region. The resulting linear plasmid containing the 1.0 kbp human IgGi constant region domain (CHi, hinge, CH2 and CH 3 10 domains) was gel isolated and used to accept hybridoma derived aOPGL variable regions. Cloning of the 9H7 anti-OPGL MAb heavy chain Three anti-OPGL hybridoma IgGi heavy chain cDNAs; 9H7, 16E1 and 18B2, were cloned into pDSR19 mammalian cell expression vector. The construction of a 15 plasmid encoding the 9H7 IgGi heavy chain is explicitly described here; the other hybridoma heavy chains were cloned using similar procedures. The anti-OPGL-9H7 heavy chain variable region was obtained using PCR amplification methods from first strand cDNA prepared from hybridoma 9H7 total RNA. First strand cDNA was prepared from 9H7 total RNA using a random primer with an extended 5'-adapter (5' 20 GGCCGGATAGGCCTCACNNNNNNT-3', SEQ ID NO: 53) and the materials and methods provided by the Gibco SuperScript II TM Preamplification System for First Strand cDNA Synthesis kit (Cat. No. 18089-011). The oligonucleotides below were used for the PCR: 5' heavy chain RACE primer, 2508-02 (SEQ ID NO: 61): 58 WO 03/086289 PCT/US03/10749 5' - (CG)AG GT(CG) CAG (CT)T(GT) GTG (CG)AG TC- 3'; 3' heavy chain RACE primer, 2420-54 (SEQ ID NO: 62): 5' -CTG AGT TCC ACG ACA CC - 3'. Amplified DNA was cloned into pCRII-TOPO (Invitrogen) and the resulting 5 plasmids were sequenced. The heavy chain consensus sequence was used to design primers for PCR amplification of the variable region of the 9H7 heavy chain. To generate the signal sequence, a three-step PCR was performed. First, primers 2512-98 and 2673 14 were used with a 9H7 heavy chain cDNA clone template. Conditions used for the reaction were: 94 0 C for 1 minute; 94 0 C for 20 seconds, 42"C for 30 seconds, 74*C for 150 10 seconds for 2 cycles; 94'C for 20 seconds, 56*C for 30 seconds, 74*C for 150 seconds for 25 cycles; and 74*C for 7 minutes with Pfu polymerase and the appropriate buffer and nucleotides. The PCR product was then amplified with primers 2663-07 and 2673-14 followed by amplification with primers 2663-08 and 2673-14. The primers are shown below. 15 2663-08 (SEQ ID NO: 63) HindIII Xbal Kozak 5'-C AGC AG AAGCTTCTAGA CCACC ATG GAC ATG AGG GTG CCC GCT CAG CTC CTG GG-3'; 20 2663-07 (SEQ ID NO: 64) 5'-CC GCT CAG CTC CTG GGG CTC CTG CTG CTG TGG CTG AGA GGT GCC AGA T-3'; 2512-98 (SEQ ID NO: 65) 5'-G TGG TTG AGA GGT GCC AGA TGT GAG GTG CAG CTG GTG CAG 25 TCT -3'; 2673-14 (SEQ ID NO: 66) BsmBI 5'-GT GGA GGC ACT AGA GAC GGT GAC CAG GGC TCC CTG GCC CCA GGG GTC GAA -3'. 30 The PCR reactions generated a 443 bp fragment encoding 138 amino acid residues (including the 22 amino acid signal sequence) that was purified using a QlAquick PCR 59 WO 03/086289 PCT/US03/10749 Purification kit (Qiagen Cat. No. 28104), cut with XbaI and BsnBI, and Qiagen purified again. This fragment, containing the heavy chain with a 5' Kozak (translational initiation) site and the following signal sequence for mammalian expression: MDMRVPAQLLGLLLLWLRGARC (SEQ ID NO: 60), 5 was ligated into pDSRa19:hIgG1CH to generate plasmid pDSRa19:9H7 IgG1 (Figure 18). The 9H7 IgGi heavy chain expression clone was sequenced to confirm that it encoded the same peptide that was identified in the 9H7 hybridoma. The final expression vector, pDSRal9:rat variable region/humnan constant region IgGi is 6158 bp and contains 10 the 7 functional regions described in Table 3. Table 3 Plasmid Base Pair Nunber: 2 to 881 A transcription termination/polyadenylation signal from the oi-subunit of the bovine pituitary glycoprotein hormone (a-FSH) (Goodwin, et al., 1983, Nucleic Acids Res. 11.:6873-82; Genbank Accession Number X00004) 882 to 2027 A mouse dihydrofolate reductase (DHFR) minigene containing the endogenous mouse DHFR promoter, the cDNA coding sequences, and the DHFR transcription termination/polyadenylation signals (Gasser et al, 1982, Proc. Natl. Acad. Sci. U. S. A. 79:6522-6; Nunberg et al., 1980, Cell.19:355-64; Setzer et al., 1982, J Biol. Chemn. 257:5143-7; McGrogan et al., 1985, J. Biol. Chem. 260:2307-14) 2031 to 3947 pBR322 sequences containing the ampicillin resistance marker gene and the origin for replication of the plasmid in E. coli (Genbank Accession Number J01 749) 3949 to 4292 An SV40 early promoter, enhancer and origin of replication (Takebe et al., 1988, Mol. Cell Biol. 8:466-72, Genbank Accession Number J02400) 4299 to 4565 A translational enhancer element from the HTLV-1 LTR domain (Seiki et al., 1983, Proc. Nat!. Acad. Sci. U. S. A. 80:3618-22, Genbank Accession Number J02029) 4574 to 4730 An intron from the SV40 16S, 19S splice donor/acceptor signals (Okayama and Berg, 1983. Mol. Cell Biol. 3:280-9, Genbank Accession Number J02400) 4755 to 6158 The rVh/hChl heavy chain cDNA between the Abal and Sall sites. The sequences of which follows (SEQ ID NO: 67): Xbal TCTAG ACCACCATGG ACATCAGGCT CAGCTTAGTT TTCCTTGTCC TTTCATAAA AGGTGTCCAG TGTGAGGTAG AACTGGTGGA GTCTGGGGGC GGCTTAGTAC AACCTGGAAG GTCCATGACA CTCTCCTGTG CAGCCTCGGG ATTCACTITC AGAACCTATG GCATGGCCTG GGTCCGCCAG GCCCCAACGA AGGGTCTGGA GTGGGTCTCA TCAATTACTG CTAGTGGTGG TACCACCTAC TATCGAGACT CCGTGAAGGG CCGCTTCACT ATTIT AGGG ATAATGCAAA AAGTACCCTA TACCTGCAGA TGGACAGTCC GAGGTCTGAG GACACGGCCA CTTAITCTG TACATCAATT BsmBI TCGGAATACT GGGGCCACGG AGTCATGGTC ACCGTCTCTA GTGCCTCCACCAAGGGCCCA TCGGTCTTCC CCCTGGCACC CTCCTCCAAG AGCACCTCTGGGGGCACAGC GGCCCTGGGC TGCCTGGTCA AGGACTACTT CCCCGAACCG GTGACGGTGT CGTGGAACTC AGGCGCCCTG ACCAGCGGCG TGCACACCTT CCCGGCTGTC CTACAGTCCT CAGGACTCTA CTCCCTCAGC AGCGTGGTGACCGTGCCCTC CAGCAGCTTG GGCACCCAGA 60 WO 03/086289 PCT/US03/10749 CCTACATCTG CAACGTGAATCACAAGCCCA GCAACACCAA GGTGGACAAG AAAGTTGAGC CCAAATCTTG TGACAAAACT CACACATGCC CACCGTGCCC AGCACCTGAA CTCCTGGGGG GACCGTCAGT CTTCCTCITC CCCCCAAAAC CCAAGGACAC CCTCATGATC TCCCGGACCC CTGAGGTCAC ATGCGTGGTG GTGGACGTGA GCCACGAAGACCCTGAGGTC AAGTTCAACT GGTACGTGGA CGGCGTGGAG GTGCATAATG CCAAGACAAA GCCGCGGGAG GAGCAGTACA ACAGCACGTA CCGTGTGGTC AGCGTCCTCA CCGTCCTGCA CCAGGACTGG CTGAATGGCA AGGAGTACAAGTGCAAGGTC TCCAACAAAG CCCTCCCAGC CCCCATCGAG AAAACCATCTCCAAAGCCAA AGGGCAGCCC CGAGAACCAC AGGTGTACAC CCTGCCCCCA TCCCGGGATG AGCTGACCAA GAACCAGGTC AGCCTGACCT GCCTGGTCAA AGGCTTCTAT CCCAGCGACA TCGCCGTGGA GTGGGAGAGC AATGGGCAGCCGGAGAACAA CTACAAGACC ACGCCTCCCG TGCTGGACTC CGACGGCTCC TTCITCCTCT ATAGCAAGCT CACCGTGGAC AAGAGCAGGT GGCAGCAGGG GAACGTCTTC TCATGCTCCG TGATGCATGA GGCTCTGCAC AACCACTACA CGCAGAAGAG CCTCTCCCTG TCTCCGGGTA SaI AATGATAAGT CGAC Example 3 9H7 anti-OPGL MAb expression in CHO cells Recombinant anti-OPGL antibodies are produced by Chinese hamster ovary cells, 5 specifically CHO AM-1/D, as disclosed in U.S. Patent No. 6,210,924 (incorporated by reference). DNA sequences encoding the complete heavy or light chains of each anti OPGL antibody of the invention are cloned into expression vectors such as those described above. CHO AM-l/D cells are co-transfected with an expression vector capable of expressing a complete heavy chain and an expression vector expressing the 10 complete light chain of the appropriate anti-OPGL antibody. For example, to generate the 22B3 antibody, cells are co-transfected with a vector capable of expressing a complete heavy chain comprising the amino acid sequence as set forth in SEQ ID NO: 30 and a vector capable of expressing a complete light chain comprising the amino acid sequence set forth in SEQ ID NO: 32. To generate the 2E1 1 antibody, cells are co-transfected with 15 a vector capable of expressing a complete heavy chain comprising the amino acid sequence as set forth in SEQ ID NO: 34 and a vector capable of expressing a complete light chain comprising the amino acid sequence set forth in SEQ ID NO: 36. To generate the 2D8 antibody, cells are co-transfected with a vector capable of expressing a complete heavy chain comprising the amino acid sequence as set forth in SEQ ID NO: 38 and a 20 vector capable of expressing a complete light chain comprising the amino acid sequence 61 WO 03/086289 PCT/US03/10749 set forth in SEQ I) NO: 40. To generate the 18B2 antibody, cells are co-transfected with a vector capable of expressing a complete heavy chain comprising the amino acid sequence as set forth in SEQ ID NO: 42 and a vector capable of expressing a complete light chain comprising the amino acid sequence set forth in SEQ ID NO: 44. To generate 5 the 16E1 antibody, cells are co-transfected with a vector capable of expressing a complete heavy chain comprising the amino acid sequence as set forth in SEQ ID NO: 46 and a vector capable of expressing a complete light chain comprising the amino acid sequence set forth in SEQ ID NO: 48. To generate the 9H7 antibody, cells are co-transfected with a vector capable of expressing a complete heavy chain comprising the amino acid 10 sequence as set forth in SEQ ID NO: 50 and a vector capable of expressing a complete light chain comprising the amino acid sequence set forth in SEQ ID NO: 52. Table 4 summarizes the complete heavy and complete light chains for the various OPGL antibodies. 15 Table 4 Heavy Chain Variable Region Antibody + Complete Heavy Chain Heavy Chain Constant Region 22B3 SEQ ID NO: 6 + SEQ ID NO: 2 SEQ ID NO: 30 2E11 SEQ ID NO: 10 + SEQ ID NO: 2 SEQ ID NO: 34 2D8 SEQ ID NO: 14 + SEQ ID NO: 2 SEQ ID NO: 38 18B2 SEQ ID NO: 18 + SEQ ID NO: 2 SEQ ID NO: 42 16E1 SEQ D NO: 22 + SEQ ID NO: 2 SEQ ID NO: 46 9H7 SEQ ID NO: 26 + SEQ ID NO: 2 SEQ ID NO: 50 Light Chain Variable Region Antibody + Complete Light Chain Light Chain Constant Region 22B3 SEQ ID NO: 8 + SEQ ID NO: 4 SEQ ID NO: 32 2E11 SEQ ID NO: 12 + SEQ ID NO: 4 SEQ ID NO: 36 2D8 SEQIDNO:16+SEQIDNO:4 SEQ IDNO: 40 18B2 SEQ ID NO: 20 + SEQ ID NO: 4 SEQ ID NO: 44 16E1 SEQ ID NO: 24 + SEQ ID NO: 4 SEQ ID NO: 48 9H7 SEQ ID NO: 28 + SEQ ID NO: 4 SEQ ID NO: 52 Stable expression of the 9H7 anti-OPGL MAb was achieved by co-transfection of pDSRal9:9H7 IgG 1 and pDSRc19:9H7 kappa plasmids into dihydrofolate reductase deficient (DHFR-) serum-free adapted Chinese hamster ovary cells (CHO AM-1/D, U.S. 20 Patent No. 6,210,924) using the art-recognized calcium phosphate method. Transfected 62 WO 03/086289 PCT/US03/10749 cells were selected in 96 well plates in medium containing dialyzed serum but not containing hypoxanthine-thymidine to ensure the growth of cells expressing the DHFR enzyme. Over 5000 transfected clones were screened using assays such as HTRF (homogeneous time resolved fluorescence) and ELISA in order to detect expression of 5 9H7 anti-OPGL MAb in the conditioned medium. The highest expressing clones were selected for single cell cloning and creation of cell banks. Example 4 Production of anti-OPGL Antibodies 10 Anti-OPGL antibodies are produced by expression in a clonal line of CHO cells. For each production run, cells from a single vial are thawed into serum-free cell culture media. The cells are grown initially in a T-flask and are serially expanded through a series of spinner flasks until sufficient inoculum has been generated to seed a 20L bioreactor. Following growth for 5-10 days, the culture is then used to inoculate a 300L 15 bioreactor. Following growth for an additional 5-10 days, the culture is used to inoculate a 2000L bioreactor. Production is carried out in a 2000L bioreactor using a fed batch culture, in which a nutrient feed containing concentrated media components is added to maintain cell growth and culture viability. Production lasts for approximately two weeks during which time anti-OPGL antibody is constitutively produced by the cells and 20 secreted into the cell culture medium. The production reactor is controlled at set pH, temperature, and dissolved oxygen level: pH is controlled by carbon dioxide gas and sodium carbonate addition; dissolved oxygen is controlled by air, nitrogen, and oxygen gas flows. At the end of production, the cell broth is fed into a disk stack centrifuge and the 25 culture supernatant is separated from the cells. The concentrate is further clarified through a depth filter followed by a 0.2 pim filter. The clarified conditioned media is then concentrated by tangential flow ultrafiltration. The conditioned media is concentrated 15 to 30- fold. The resulting concentrated conditioned medium is then either processed through purification or frozen for purification at a later date. Figure 19 depicts an 30 exemplary cell culture process for producing an anti-OPGL antibody. 63 WO 03/086289 PCT/US03/10749 Example 5 Screening of Antibodies for binding to OPGL by BlAcore All experiments were performed on a BlAcore 2000 according to the manufacturer's instructions, with the following modifications. Experiments were 5 performed at room temperature using a running buffer containing 10mM Hepes (pH 7.4), 0.15M NaCl, 3mM EDTA, and 0.005% Tween 20. Protein G at 50 pg/mL in 10mM acetate pH 4.5 was immobilized to a level of 1,600 response units (RU) onto a CM5 Research grade sensor chip (BIAcore, Inc.). Antibodies (8-20 pg/mL) were captured onto the Protein G chip at a level of 300-400 RUs. CHO human OPGL (hOPGL) 140 or E. 10 coli mouse OPGL (mOPGL) 158 were passed over the immobilized antibodies at concentrations of 0.25 - 62nM. Langmuir 1:1 model was used to determine binding kinetics. Protein G immobilized to 1600 RUs was used as a blank surface. A mouse monoclonal antibody was used as a positive control to show binding to hOPGL 140 and to monitor surface stability. 15 All anti-OPGL antibodies showed strong binding to CHO hOPGL 140. 22B3 appears to have a slower off rate than the other antibodies tested. No binding of E. coli mOPGL 158 was detected. The results are summarized in Table 5. Table 5 hOPGL 140 Ab off rate MOPGL 158 ka (1/Ms) kd (1/s) KD (1/M) KD half life t1/2 (s) 917 1.27E+06 2.26E-04 1.93E-10 190pm 3067 no binding 18B2 8.78E+05 1.86E-04 2.11E-10 210pm 3726 no binding 2D8 1.97E+06 1.81E-04 9.20E-11 92pm 3829 no binding 2E11 4.53E+05 1.32E-04 2.92E-10 290pm 5251 no binding 16E1 2.16E+06 1.37E-04 6.33E-11 63pm 5059 no binding 22B3 1.90E+06 6.39E-05 3.37E-1 1 34pm 10847 no binding 20 Example 6 anti-OPGL Antibody Neutralizing Activity 64 WO 03/086289 PCT/US03/10749 Inhibition of Osteoclast Formation RAW 264.7 (Accession No. TIB-71, American Type Culture Collection, Manassas, VA) is a murine macrophage cell line that was derived from an Abelson murine leukemia virus-induced tumor. RAW 264.7 cells will differentiate to osteoclast 5 like cells in the presence of OPGL. An assay for generation of osteoclasts in culture from RAW cells in the presence of OPGL has been described in detail by Hsu et al., 1999, Proc. Nati. Acad. Sci. US.A. 96:3540-3545, which is incorporated by reference herein. RAW cells can be stimulated by OPGL ligand to differentiate into osteoclast-like cells, and the differentiation can be measured by tartrate-resistant acid phosphatase 10 (TRAP) activity, a property of osteoclasts. This activity provides the basis for characterizing anti-OPGL antibodies produced according to the invention, by assaying the effect of said antibodies on osteoclastogenesis. RAW cells were incubated for 4 days in the presence of a constant amount of OPGL (40 ng/mL) and varying amounts of anti-OPOL antibody (6.3 ng/mL to 200 15 ng/mL) in cell culture medium (DMEM, 10% FBS, 0.3 mg/mL L-glutamine, 100 units/mL penicillinG, 100 pg/mL streptomycin sulfate). At the end of 4 days, the cells were stained for tartrate-resistant acid phosphatase (TRAP) activity by permeabilization and acidification, followed by treatment with p-nitrophenylphosphate (PNPP) for 5 minutes. Briefly, the media was aspirated from the cells, and 100 yIL of citrate buffer 20 (having a formula of 410 mL 0.1M citric acid, 590 mL 0.1 M citrate: trisodium salt and 1 mL Triton X-100) was added to each well and the plates incubated for 3 to 5 minutes at room temperature. One hundred microliters of PNPP solution (having a fonnula of 157.8 mg acid phosphatase reagent (Sigma 104-100), 7.2 mL tartrate solution (Sigma Cat. No. 387-3), and 22.8 mL citrate buffer) was then added, and plates were incubated for 3 to 5 25 minutes at room temperature. The reaction was terminated by addition of 50 pL 0.5 M NaOH solution. TRAP converts p-nitrophenylphosphate to para-nitrophenol, which can be quantitated by optical density measurement at 405 nm. The TRAP activity, which is a surrogate marker for osteoclast development, therefore correlates with the optical density 30 at 405 nm. A plot of optical density versus anti-OPGL antibody concentration is shown in Figure 20, and demonstrates that anti-OPGL antibody inhibited osteoclast formation in this assay in a dose-dependent manner. IC 50 values were calculated using the forecast 65 WO 03/086289 PCT/US03/10749 function, and are shown in Table 6. An alkaline phosphatase-linked rat polyclonal anti human OPGL antibody (AP Ra-anti-HuOPGL Ab) with OPGL neutralizing activity was used as a positive control for the anti-huOPGL antibody neutralizing activity assay. Table 6 Sample ICso (ng/mL) AP Ra-anti-HuOPGL Ab 112 9H7 129 18B2 80 2D8 611 2E11 77 16E1 352 22B3 146 IC5 (ng/mL) Running Average AP Ra-anti-HuOPGL Ab Average 140 Stdev 35.8 CV 26% Count 25 5 Example 7 Pharmacokinetics in Cynomolgus Monkeys The in vivo activity and pharmacokinetics of the anti-OPGL antibodies of the 10 invention were assayed using cynomolgus monkeys. Three female cynomolgus monkeys, not greater than 5 years of age and weighing 2 to 5 kg each received single subcutaneous (SC) doses of 1 mg/kg anti-OPGL antibody. Animals were dosed with anti-OPGL antibody expressed from transfected Chinese hamster ovary (CHO) cells and serum samples were taken for determination of 15 anti-OPGL antibody levels, anti-therapeutic antibody analysis, and analysis of the bone turnover marker serum N-telopeptide (serum N-Tx), alkaline phosphatase (ALP), and serum calcium (serum Ca). The serum concentration-time profiles following SC administration are shown in Figure 21. The serum N-Tx concentration-time profiles following SC administration are 20 shown in Figure 22. 66 WO 03/086289 PCT/US03/10749 Example 8 Identification of an Epitope for Antibodies on OPGL Production of variant murine OPGL Human OPGL [143-317] was produced as described in Example 1 of WO 5 01/62932, published August 30, 2001, which is hereby incorporated by reference in its entirety. Murine OPGL [158-316] containing amino acid residues 158 through 316 of murine OPGL (as shown in Figure 1 of International Application, Publication No. W098/4675 1, incorporated by reference) preceded by an introduced N-terminal methionine residue was produced in E. coli. Murine OPGL [158-316] was purified from 10 the soluble fraction of bacteria as described previously (Lacey et al., 1998, Cell 93:165 176). FLAG-tagged murine OPGL [158-316] was produced by introducing a nucleic acid encoding an N-terminal methionine followed by a FLAG-tag sequence fused to the N terminus of residues 158-316 as shown in Figure 1 of International Application, Publication No. W098/46751 using conventional genetic engineering techniques. The 15 FLAG-tagged OPGL [158-316] molecule was cloned into bacterial expression vector pAMG21 (pAMG21 was deposited with the American Type Culture Collection and having Accession No. 98113). A FLAG-tagged murine OPGL [158-316] polypeptide variant was constructed in which amino acid residues SVPTD (SEQ ID NO: 68) at positions 229-233 (as shown in 20 Figure 1 of International Application, Publication No. W098/4675 1) were substituted with corresponding amino acid residues DLATE (SEQ ID NO: 69) at positions 230-234 (as shown in Figure 4 of International Application, Publication No. W098/46751). The. resulting construct referred to as "FLAG-murine OPGL [158-316]/DE" has the nucleic acid and protein sequence as shown in Figure 23 (SEQ ID NO: 72) (which shows only 25 where the mutations are located). The amino acid sequence changes are located in a region of OPGL between the D and E regions. Figure 23 shows a comparison of murine (SEQ ID NO: 70), human (SEQ ID NO: 71), and murine DE variant (SEQ ID NO: 72) amino acid sequences in this region. The sequence changes in the murine variant are S231D, V232L, P233A and D235E with the T at position 234 unchanged. Flanking 30 sequences in this region are virtually identical between murine and human OPGL. 67 WO 03/086289 PCT/US03/10749 This molecule was constructed using a two-step PCR reaction where the first step contained two separate PCR reactions, designated reaction A and reaction B. For both reaction A and reaction B, pAMG21-FLAG-murine OPGL [158-316] DNA was used as a template for PCR. Reaction A employed oligonucleotides #2640-90 and #2640-91 for 5 PCR, whereas reaction B employed oligonucleotides #2640-92 and #2640-93. #2640-90 (SEQ ID NO: 73): CCTCTCATATGGACTACAAGGAC; #2640-91 (SEQ ID NO 74): AGTAGCCAGGTCTCCCGATGTTTCATGATG; 10 #2640-92 (SEQ ID NO: 75): CTGGCTACTGAATATCTTCAGCTGATGGTG; #2640-93 (SEQ ID NO: 76): CCTCTCCTCGAGTTAGTCTATGTCC. Conditions for reactions A and B were: 95"C for 1 min; 95*C for 20 seconds, 15 44*C for 30 seconds, 72'C for 45 seconds for 5 cycles; 95*C for 20 seconds, 60*C for 30 seconds, 72*C for 45 seconds for 25 cycles; and 72 0 C for 10 minutes with Pfu Turbo polymerase (Stratagene) and the appropriate buffer and nucleotides. After thermocycling was performed, PCR products from reactions A and B were purified from an agarose gel using conventional methods. The second step PCR reaction, designated reaction C, 20 utilized purified reaction A and reaction B PCR products as a template and oligonucleotides #2640-90 and #2640-93 as primers. Conditions for reaction C were: 95*C for 1 minute; 95'C for 20 seconds, 37 0 C for 30 seconds, 72*C for 1 minute for 25 cycles; and 72 0 C for 10 minutes with Pfu Turbo polymerase and the appropriate buffer and nucleotides. Following thermocycling, the product from reaction C was cloned into 25 the pCRII-TOPO cloning vector (Invitrogen) and electroporated into DH1Ob (Gibco) cells using methods provided by the manufacturer. Clones were selected and sequenced to confirm the amino acid sequence SVPTD (SEQ ID NO: 68) in murine OPGL [158-316] was changed to DLATE (SEQ ID NO: 69). The sequence-verified DNA was then digested with NdeI and X7oI, purified, and subcloned into bacterial expression vector 30 pAMG21 giving rise to plasmid pAMG21-FLAG-murine OPGL[158-316]/DE. 68 WO 03/086289 PCT/US03/10749 E. coli host GM94 (deposited with the American Type Culture Collection under Accession No. 202173) containing plasmid pAMG21-FLAG-murine OPGL[158-316]/DE was grown in 2XYT media to an exponential growth phase and induced to express the FLAG-tagged murine OPGL[158-316]/DE protein by addition of V fischeri synthetic 5 autoinducer to 100 ng/mL. Approximately 3-6 hours after induction, the cells were pelleted and recombinant FLAG-murine OPGL[158-316]/DE protein was purified from the soluble fraction of E. coli using methods described in Lacey et al., ibid. Binding of Anti-human OPGL Antibodies to human OPGL[143-317], murine 10 OPGL[158-316], and FLAG-murine OPGL[158-316]/DE Costar E.I.A./R.I.A. Plates (Flat Bottom High Binding, Cat# 3590) were coated with 100 pL/well of either human OPGL[143-317] protein, murine OPGL[158-316] protein, or FLAG-tagged murine OPGL[158-316]/DE protein at 3 pg/mL in PBS, overnight at 4*C with agitation. After overnight incubation, the protein solutions were 15 removed from the plate and 200 pL of 5% Chicken Serum (Gibco/BRL Cat# 16110-082) in PBST (PBS plus 0.05% Tween 20) was added to each well of the plate and plates were incubated at room temperature (RT) for 3 hours with agitation. After incubation and blocking, plates were washed 4 times with IX K-P wash solution in dH 2 0 (Cat# 50-63 00, Kirkegaard & Perry Laboratories) and dried. Purified anti-OPGL antibody or human 20 OPGL [22-194]-Fc protein was serially diluted 1:1 from 2 pg/mL to 1.953 ng/mL in 5% Chicken Serum in PBST and 100 pL/well was added to appropriate wells of the microtiter plate coated with either human OPGL[143-317], murine OPGL[158-316], or FLAG-tagged murine OPGL[158-316]/DE protein. Plates were incubated for 2.25 hours at room temperature with agitation, washed four times with 1X K-P wash solution and 25 dried. Goat anti-human IgG (Fe) (Jackson ImmunoResearch, Cat# 109-036-098) was diluted 1:3000 in 5% Chicken Serum in PBST and 100 pL was added to each well. Plates were incubated for 1.25 hours at room temperature with agitation, washed six times with IX K-P wash solution, and dried. 100 pL of undiluted ABTS substrate (Kirkegaard & Perry; Cat# 50-66-00) was added to each well and the dish was incubated at room 30 temperature until sufficient blue-green color developed. Color development was stopped by addition of 100 pL 1% SDS. Quantitation of color development was performed using a microtiter plate reader with detection at 405 nm. 69 WO 03/086289 PCT/US03/10749 The results of the enzyme immunoassay are shown in Figures 24 and 25. All six anti-OPGL antibodies of the invention bind to human OPGL[143-317]. However, only 22B3 antibody shows detectable binding to murine OPGL[158-316] over the concentration range tested (Figure 24). While binding of 22B3 antibody to murine 5 OPGL[158-316] occurs with a much lower affinity than to human OPGL[143-317], the 2D8, 9H7, 16E1, and 22B3 antibodies bind to FLAG-tagged murine OPGL[158-316]/DE (Figure 25) almost as well as to human OPGL[143-317] under the assay conditions above. Thus, the amino acid changes in murine OPGL[158-316]/DE compared to murine OPGL[158-316] are important to the binding activity of antibodies 2D8, 9H7, 16E1, and 10 22B3. Antibodies 2E1 1 and 18B2 show no detectable binding to either murine OPGL[158-316] or murine OPGL[158-316]/DE. The FLAG-murine OPGL[158-316]/DE was assayed for activity in a RAW cell assay as described in Example 6 and observed to have a similar ED50 for osteoclast formation as human OPGL[143-317], indicating that the DE variant is active in 15 promoting osteoclast activity in vitro. Therefore, the binding of the anti-OPGL antibodies to murine OPGL[158-316]/DE is likely to inhibit osteoclast formation. The epitope of the 2D8, 9H7, 16E1, and 22B3 anti-human OPGL antibodies is located to a region of human OPGL that includes at least amino acid residues DLATE (residues 230 through 234 of human OPGL as shown in Figure 4 of International 20 Application, Publication No. W098/46751) termed the D-E loop. The 2E1 1 and 18B2 anti-human OPGL antibodies do not bind to peptide fragments corresponding to the D-E loop region by itself. However, it will be recognized that in the native molecule these antibodies may bind to an epitope outside the D-E loop region or they may bind to all or a portion of the D-E loop region in combination with other portions of the molecule. 25 It should be understood that the foregoing disclosure emphasizes certain specific embodiments of the invention and that all modifications or alternatives equivalent thereto are within the spirit and scope of the invention as set forth in the appended claims. 70

Claims (73)

1. An isolated human antibody that specifically binds osteoprotegerin ligand (OPGL), comprising a heavy chain and a light chain, wherein the heavy chain 5 comprises a heavy chain variable region comprising an amino acid sequence as set forth in any of SEQ ID NO: 6, SEQ ID NO: 14, SEQ ID NO: 22, or SEQ ID NO: 26, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof.

2. The antibody of claim 1, wherein the antibody specifically binds the D-E loop 10 region of osteoprotegerin ligand (OPGL).

3. An isolated human antibody that specifically binds osteoprotegerin ligand (OPGL), comprising a heavy chain and a light chain, wherein the heavy chain comprises a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 10 or SEQ ID NO: 18, or an antigen-binding or an 15 immunologically functional immunoglobulin fragment thereof.

4. The antibody of claim 3, wherein the antibody specifically binds to: a. a region of osteoprotegerin ligand (OPGL) that is outside the D-E loop region; or b. both a region of OPGL that is outside the D-E loop region and all or a 20 portion of the D-E loop region.

5. The antibody of claim 4, wherein the antibody specifically binds to both a region of OPGL that is outside the D-E loop region and all or a portion of the D-E loop region, wherein binding is consecutive or simultaneous.

6. An isolated human antibody that specifically binds osteoprotegerin ligand 25 (OPGL), comprising a heavy chain and a light chain, wherein the light chain comprises a light chain variable region comprising an amino acid sequence as set forth in any of SEQ ID NO: 8, SEQ ID NO: 16, SEQ ID NO: 24, or SEQ ID NO: 28, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof. 71 WO 03/086289 PCT/US03/10749

7. The antibody of claim 6, wherein the antibody specifically binds the D-E loop region of osteoprotegerin ligand (OPGL).

8. An isolated human antibody that specifically binds osteoprotegerin ligand (OPGL), comprising a heavy chain and a light chain, wherein the light chain 5 comprises a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 12 or SEQ ID NO: 20, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof.

9. The antibody of claim 8, wherein the antibody specifically binds to: a. a region of osteoprotegerin ligand (OPGL) that is outside the D-E loop 10 region; or b. both a region of OPGL that is outside the D-E loop region and all or a portion of the D-E loop region.

10. The antibody of claim 9, wherein binding to both a region of OPGL that is outside the D-E loop region and all or a portion of the D-E loop region is 15 consecutive or simultaneous.

11. An isolated human antibody that specifically binds osteoprotegerin ligand (OPGL), comprising a heavy chain and a light chain, wherein the heavy chain comprises an amino acid sequence as set forth in any of SEQ ID NO: 30, SEQ ID NO: 38, SEQ ID NO: 46, or SEQ ID NO: 50, or an antigen-binding or an 20 immunologically functional immunoglobulin fragment thereof.

12. The antibody of claim 11, wherein the antibody specifically binds the D-E loop region of osteoprotegerin ligand (OPGL).

13. An isolated human antibody that specifically binds osteoprotegerin ligand (OPGL), comprising a heavy chain and a light chain, wherein the heavy chain 25 comprises a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 34 or SEQ ID NO: 42, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof.

14. The antibody of claim 13, wherein the antibody specifically binds to: a. a region of osteoprotegerin ligand (OPGL) that is outside the D-E loop 30 region; or 72 WO 03/086289 PCT/US03/10749 b. both a region of OPGL that is outside the D-E loop region and all or a portion of the D-E loop region.

15. The antibody of claim 14, wherein binding to both a region of OPGL that is outside the D-E loop region and all or a portion of the D-E loop region is 5 consecutive or simultaneous.

16. An isolated human antibody that specifically binds osteoprotegerin ligand (OPGL), comprising a heavy chain and a light chain, wherein the light chain comprises an amino acid sequence as set forth in any of SEQ ID NO: 32, SEQ ID NO: 40, SEQ ID NO: 48, or SEQ ID NO: 52, or an antigen-binding or an 10 immunologically functional immunoglobulin fragment thereof.

17. The antibody of claim 16, wherein the antibody specifically binds the D-E loop region of osteoprotegerin ligand (OPGL).

18. An isolated human antibody that specifically binds osteoprotegerin ligand (OPGL), comprising a heavy chain and a light chain, wherein the light chain 15 comprises a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 36 or SEQ ID NO: 44, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof.

19. The antibody of claim 18, wherein the antibody specifically binds to: a. a region of osteoprotegerin ligand (OPGL) that is outside the D-E loop 20 region; or b. both a region of OPGL that is outside the D-E loop region and all or a portion of the D-E loop region.

20. The antibody of claim 19, wherein binding to both a region of OPGL that is outside the D-E loop region and all or a portion of the D-E loop region is 25 consecutive or simultaneous.

21. An isolated human antibody that specifically binds osteoprotegerin ligand (OPGL), wherein the antibody comprises: a. a heavy chain having a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 6, an antigen-binding fragment 30 thereof, or an immunologically functional immunoglobulin fragment 73 WO 03/086289 PCT/US03/10749 thereof, and a light chain having a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 8, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof; 5 b. a heavy chain having a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 14, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof, and a light chain having a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 16, an antigen-binding 10 fragment thereof, or an immunologically functional immunoglobulin fragment thereof; c. a heavy chain having a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 22, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment 15 thereof, and a light chain having a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 24, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof; d. a heavy chain having a heavy chain variable region comprising an amino 20 acid sequence as set forth in SEQ ID NO: 26, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof, and a light chain having a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 28, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin 25 fragment thereof; e. a heavy chain comprising an amino acid sequence as set forth in SEQ ID NO: 30, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof, and a light chain comprising an amino acid sequence as set forth in SEQ ID NO: 32, an antigen-binding 30 fragment thereof, or an immunologically functional immunoglobulin fragment thereof; 74 WO 03/086289 PCT/US03/10749 f. a heavy chain comprising an amino acid sequence as set forth in SEQ ID NO: 38, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof, and a light chain comprising an amino acid sequence as set forth in SEQ ID NO: 40, an antigen-binding 5 fragment thereof, or an immunologically functional immunoglobulin fragment thereof; g. a heavy chain comprising an amino acid sequence as set forth in SEQ ID NO: 46, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof, and a light chain comprising 10 an amino acid sequence as set forth in SEQ ID NO: 48, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof; or h. a heavy chain comprising an amino acid sequence as set forth in SEQ ID NO: 50, an antigen-binding fragment thereof, or an immunologically 15 functional immunoglobulin fragment thereof, and a light chain comprising an amino acid sequence as set forth in SEQ ID NO: 52, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof.

22. The antibody of claim 21, wherein the antibody specifically binds the D-E 20 loop region of osteoprotegerin ligand (OPGL).

23. The antibody of claim 21, wherein the heavy chain comprises a heavy chain variable region having an amino acid sequence as set forth in SEQ ID NO: 6, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof, and the light chain comprises a light chain 25 variable region having an amino acid sequence as set forth in SEQ ID NO: 8, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof.

24. The antibody of claim 23, wherein the heavy chain variable region comprises an amino acid sequence that has at least 90% sequence identity to the amino 30 acid sequence set forth in SEQ ID NO: 6, and wherein the light chain variable region comprises an amino acid sequence that has as least 90% sequence 75 WO 03/086289 PCT/US03/10749 identity to the amino acid sequence as set forth in SEQ ID NO: 8, and wherein the antibody specifically binds to an osteoprotegerin ligand (OPGL).

25. The antibody of claim 21, wherein the heavy chain comprises a heavy chain variable region having an amino acid sequence as set forth in SEQ ID NO: 14, 5 an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof, and the light chain comprises a light chain variable region having an amino acid sequence as set forth in SEQ ID NO: 16, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof. 10

26. The antibody of claim 25, wherein the heavy chain variable region comprises an amino acid sequence that has at least 90% sequence identity to the amino acid sequence as set forth in SEQ ID NO: 14, and wherein the light chain variable region comprises an amino acid sequence that has as least 90% sequence identity to the amino acid sequence as set forth in SEQ ID NO: 16, 15 wherein the antibody specifically binds to an osteoprotegerin ligand (OPGL).

27. The antibody of claim 21, wherein the heavy chain comprises a heavy chain variable region having an amino acid sequence as set forth in SEQ ID NO: 22, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof, and the light chain comprises a light chain 20 variable region having an amino acid sequence as set forth in SEQ ID NO: 24, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof.

28. The antibody of claim 27, wherein the heavy chain variable region comprises an amino acid sequence that has at least 90% sequence identity to the amino 25 acid sequence as set forth in SEQ ID NO: 22, and wherein the light chain variable region comprises an amino acid sequence that has as least 90% sequence identity to the amino acid sequence as set forth in SEQ ID NO: 24, wherein the antibody specifically binds to an osteoprotegerin ligand (OPGL).

29. The antibody of claim 21, wherein the heavy chain comprises a heavy chain 30 variable region having an amino acid sequence as set forth in SEQ ID NO: 26, an antigen-binding fragment thereof, or an immunologically functional 76 WO 03/086289 PCT/US03/10749 immunoglobulin fragment thereof, and the light chain comprises a light chain variable region having an amino acid sequence as set forth in SEQ ID NO: 28, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof. 5

30. The antibody of claim 29, wherein the heavy chain variable region comprises an amino acid sequence that has at least 90% sequence identity to the amino acid sequence as set forth in SEQ ID NO: 26, and wherein the light chain variable region comprises an amino acid sequence that has as least 90% sequence identity to the amino acid sequence as set forth in SEQ ID NO: 28, 10 wherein the antibody in specifically binds to an osteoprotegerin ligand (OPGL).

31. The antibody of claim 21, wherein the heavy chain comprises an amino acid sequence as set forth in SEQ ID NO: 30, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof, and the 15 light chain comprises an amino acid sequence as set forth in SEQ ID NO: 32, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof.

32. The antibody of claim 21, wherein the heavy chain comprises an amino acid sequence as set forth in SEQ ID NO: 38, an antigen-binding fragment thereof, 20 or an immunologically functional immunoglobulin fragment thereof, and the light chain comprises an amino acid sequence as set forth in SEQ ID NO: 40, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof.

33. The antibody of claim 21, wherein the heavy chain comprises an amino acid 25 sequence as set forth in SEQ ID NO: 46, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof, and the light chain comprises an amino acid sequence as set forth in SEQ ID NO: 48, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof. 30

34. The antibody of claim 21, wherein the heavy chain comprises an amino acid sequence as set forth in SEQ ID NO: 50, an antigen-binding fragment thereof, 77 WO 03/086289 PCT/US03/10749 or an immunologically functional immunoglobulin fragment thereof, and the light chain comprises an amino acid sequence as set forth in SEQ ID NO: 52, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof. 5

35. An isolated human antibody that specifically binds osteoprotegerin ligand (OPGL), wherein the antibody comprises: a. a heavy chain having a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 10, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment 10 thereof, and a light chain having a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 12, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof; b. a heavy chain having a heavy chain variable region comprising an amino 15 acid sequence as set forth in SEQ ID NO: 18, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof, and a light chain having a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 20, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin 20 fragment thereof; c. a heavy chain comprising an amino acid sequence as set forth in SEQ ID NO: 34, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof, and a light chain comprising an amino acid sequence as set forth in SEQ ID NO: 36, an antigen-binding 25 fragment thereof, or an immunologically functional immunoglobulin fragment thereof; or d. a heavy chain comprising an amino acid sequence as set forth in SEQ ID NO: 42, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof, and a light chain comprising 30 an amino acid sequence as set forth in SEQ ID NO: 44, an antigen-binding 78 WO 03/086289 PCT/US03/10749 fragment thereof, or an immunologically functional immunoglobulin fragment thereof.

36. The antibody of claim 35, wherein the antibody specifically binds to: a. a region of osteoprotegerin ligand (OPGL) that is outside the D-E loop 5 region; or b. both a region of OPGL that is outside the D-E loop region and all or a portion of the D-E loop region.

37. The antibody of claim 36, wherein binding to both a region of OPGL that is outside the D-E loop region and all or a portion of the D-E loop region is 10 consecutive or simultaneous.

38. The antibody of claim 35, wherein the heavy chain comprises a heavy chain variable region having an amino acid sequence as set forth in SEQ ID NO: 10, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof, and the light chain comprises a light chain 15 variable region having an amino acid sequence as set forth in SEQ ID NO: 12, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof.

39. The antibody of claim 38, wherein the heavy chain variable region comprises an amino acid sequence that has at least 90% sequence identity to the amino 20 acid sequence as set forth in SEQ ID NO: 10, and wherein the light chain variable region comprises an amino acid sequence that has as least 90% sequence identity to the amino acid sequence as set forth in SEQ ID NO: 12, wherein the antibody specifically binds to an osteoprotegerin ligand (OPGL).

40. The antibody of claim 35, wherein the heavy chain comprises a heavy chain 25 variable region comprising an amino acid sequence as set forth in SEQ ID NO: 18, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof, and the light chain comprises a light chain variable region having an amino acid sequence as set forth in SEQ ID NO: 20, an antigen-binding fragment thereof, or an immunologically 30 functional immunoglobulin fragment thereof. 79 WO 03/086289 PCT/US03/10749

41. The antibody of claim 40, wherein the heavy chain variable region comprises an amino acid sequence that has at least 90% sequence identity to the amino acid sequence as set forth in SEQ ID NO: 18, and wherein the light chain variable region comprises an amino acid sequence that has as least 90% 5 sequence identity to the amino acid sequence as set forth in SEQ ID NO: 20, wherein the antibody specifically binds to an osteoprotegerin ligand (OPGL).

42. The antibody of claim 35, wherein the heavy chain comprises an amino acid sequence as set forth in SEQ ID NO: 34, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof, and the 10 light chain comprises an amino acid sequence as set forth in SEQ ID NO: 36, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof.

43. The antibody of claim 35, wherein the heavy chain comprises an amino acid sequence as set forth in SEQ ID NO: 42, an antigen-binding fragment thereof, 15 or an immunologically functional immunoglobulin fragment thereof, and the light chain comprises an amino acid sequence as set forth in SEQ ID NO: 44, an antigen-binding fragment thereof, or an immunologically functional immunoglobulin fragment thereof.

44. The antibody of claim 21 or 35, wherein the heavy chain and light chain are 20 connected by a flexible linker to form a single-chain antibody.

45. The antibody of claim 44, which is a single-chain Fv antibody.

46. The antibody of claim 21 or 35, which is a Fab antibody.

47. The antibody of claim 21 or 35, which is Fab' antibody.

48. The antibody of claim 21 or 35, which is a (Fab') 2 antibody. 25

49. The antibody of claim 21 or 35, wherein the antibody is fully human.

50. The antibody of claim 21 or 35, wherein the antibody inhibits binding of OPGL to an osteoclast differentiation and activation receptor (ODAR).

51. A method of treating an osteopenic disorder in a patient, comprising administering to a patient a pharmaceutically effective amount of the antibody 30 of claim 50. 80 WO 03/086289 PCT/US03/10749

52. A pharmaceutical composition comprising a pharmaceutically acceptable carrier and a therapeutically effective amount of the antibody of claim 50.

53. A method of treating an osteopenic disorder in a patient, comprising administering to a patient the pharmaceutical composition of claim 52. 5

54. A method for detecting OPGL in a biological sample comprising: a. contacting the sample with the antibody of claim 21 or 35, under conditions that allow for binding of the antibody to OPGL; b. and measuring the level of bound antibody in the sample.

55. A heavy chain comprising a variable region and a constant region, wherein the 10 variable region comprises an amino acid sequence as set forth in any of SEQ ID NO: 6, SEQ ID NO: 10, SEQ ID NO: 14, SEQ ID NO: 18, SEQ ID NO: 22, or SEQ ID NO: 26, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof.

56. A heavy chain comprising an amino acid sequence as set forth in any of SEQ 15 ID NO: 30, SEQ ID NO: 34, SEQ ID NO: 38, SEQ ID NO: 42, SEQ ID NO: 46, or SEQ ID NO: 50, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof.

57. A light chain comprising a variable region and a constant region, wherein the variable region comprises an amino acid sequence as set forth in any of SEQ 20 ID NO: 8, SEQ ID NO: 12, SEQ ID NO: 16, SEQ ID NO: 20, SEQ ID NO: 24, or SEQ ID NO: 28, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof.

58. A light chain comprising an amino acid sequence as set forth in any of SEQ ID NO: 32, SEQ ID NO: 36, SEQ ID NO: 40, SEQ ID NO: 44, SEQ ID NO: 25 48, or SEQ ID NO: 52, or an antigen-binding or an immunologically functional immunoglobulin fragment thereof.

59. An isolated human antibody comprising: a. human heavy chain framework regions, a human heavy chain CDR1 region, a human heavy chain CDR2 region, and a human heavy chain 30 CDR3 region, wherein the human heavy chain CDR3 region is the heavy 81 WO 03/086289 PCT/US03/10749 chain CDR3 region of 16E1, 2D8, 22B3, or 9H7 as shown in Figure 15; and b. human light chain framework regions, a human light chain CDR1 region, a human light chain CDR2 region, and a human light chain CDR3 region, 5 wherein the human light chain CDR3 region is the light chain CDR3 region of 16E1, 2D8, 22B3, or 9H7 as shown in Figure 16; wherein the antibody specifically binds to osteoprotegerin ligand (OPGL).

60. The antibody of claim 59, wherein the antibody specifically binds the D-E loop region of osteoprotegerin ligand (OPGL). 10

61. The isolated human antibody of claim 59, wherein the human heavy chain CDR2 region is the heavy chain CDR2 region of 16E1, 2D8, 22B3, or 9H7 as shown in Figure 15 and the human light chain CDR2 region is the light chain CDR2 region of 16E1, 2D8, 22B3, or 9H7 as shown in Figure 16.

62. The antibody of claim 61, wherein the antibody specifically binds the D-E 15 loop region of osteoprotegerin ligand (OPGL).

63. The isolated human antibody of claim 59, wherein the human heavy chain CDR1 region is the heavy chain CDR1 region of 16E1, 2D8, 22B3, or 9H7 as shown in Figure 15 and the human light chain CDRl region is the light chain CDRI region of 16E1, 2D8, 22B3, or 9117 as shown in Figure 16. 20

64. The antibody of claim 63, wherein the antibody specifically binds the D-E loop region of osteoprotegerin ligand (OPGL).

65. An isolated human antibody comprising: a. human heavy chain framework regions, a human heavy chain CDR1 region, a human heavy chain CDR2 region, and a human heavy chain 25 CDR3 region, wherein the human heavy chain CDR3 region is the heavy chain CDR3 region of 2E11 or 18B2, as shown in Figure 15; and b. human light chain framework regions, a human light chain CDR1 region, a human light chain CDR2 region, and a human light chain CDR3 region, wherein the human light chain CDR3 region is the light chain CDR3 30 region of 2E11 or 18B2 as shown in Figure 16; 82 WO 03/086289 PCT/US03/10749 wherein the antibody specifically binds to osteoprotegerin ligand (OPGL).

66. The antibody of claim 65, wherein the antibody specifically binds to: a. a region of osteoprotegerin ligand (OPGL) that is outside the D-E loop region; or 5 b. both a region of OPGL that is outside the D-E loop region and all or a portion of the D-E loop region, wherein binding is consecutive or simultaneous.

67. The antibody of claim 66, wherein binding to both a region of OPGL that is outside the D-E loop region and all or a portion of the D-E loop region is 10 consecutive or simultaneous.

68. The isolated human antibody of claim 65, wherein the human heavy chain CDR2 region is the heavy chain CDR2 region of 2E 11 or 18B2 as shown in Figure 15 and the human light chain CDR2 region is the light chain CDR2 region of 2E11 or 18B2 as shown in Figure 16. 15

69. The antibody of claim 68, wherein the antibody specifically binds to: a. a region of osteoprotegerin ligand (OPGL) that is outside the D-E loop region; or b. both a region of OPGL that is outside the D-E loop region and all or a portion of the D-E loop region, wherein binding is consecutive or 20 simultaneous.

70. The antibody of claim 69, wherein binding to both a region of OPGL that is outside the D-E loop region and all or a portion of the D-E loop region is consecutive or simultaneous.

71. The isolated human antibody of claim 65, wherein the human heavy chain 25 CDR1 region is the heavy chain CDR1 region of 2E1 1 or 18B2 as shown in Figure 15 and the human light chain CDR1 region is the light chain CDRI region of 2E11 or 18B2 as shown in Figure 16.

72. The antibody of claim 71, wherein the antibody specifically binds to: 83 WO 03/086289 PCT/US03/10749 a. a region of osteoprotegerin ligand (OPGL) that is outside the D-E loop region; or b. both a region of OPGL that is outside the D-E loop region and all or a portion of the D-E loop region, wherein binding is consecutive or 5 simultaneous.

73. The antibody of claim 72, wherein binding to both a region of OPGL that is outside the D-E loop region and all or a portion of the D-E loop region is consecutive or simultaneous. 84