WO1993000366A1

WO1993000366A1 - Method for treating immunological disorders and diseases

Info

Publication number: WO1993000366A1
Application number: PCT/US1992/005360
Authority: WO
Inventors: Aldo A. Rossini; John P. Mordes; Eugene S. Handler; Dale L. Greiner
Original assignee: University Of Massachusetts Medical Center
Priority date: 1991-06-24
Filing date: 1992-06-24
Publication date: 1993-01-07
Also published as: AU2269392A

Abstract

This invention pertains to a method and apparatus for therapeutically treating insulin-dependent diabetes mellitus and other immunological disorders and disease states which are characterized by the presence of immunologically abnormal leukocytes in the body of the afflicted subject. The method involves the therapeutic administration of postthymic T lymphocytes capable of secreting soluble factors that can ameliorate disease state associated with diabetes or other autoimmune disease. Methods of screening and/or detecting insulin-dependent diabetes are also described.

Description

METHOD FOR TREATING IMMUNOLOGICAL DISORDERS AND DISEASES

Background of the Invention

It is generally recognized and accepted that autoimmune diseases and pathological states are not the result of a single causative agent or a solitary mechanism of action. Small amounts of auto-antibody and/or lymphocytes directed against a specific target are normally produced in the afflicted individual and are believed to play pathophysiological roles in cellular interactions throughout the course of the disease or disorder. In many instances, there are observable defects in the helper and/or suppressor lymphocyte functions of the white blood cells, a condition which has been categorized as cell-mediated autoimmunity.

Certain autoimmune diseases which are at least partially cell-mediated comprise those immunological disorders and disease states in which leukocytes, most notably T-cell lymphocytes, have become specifically activated by, directed against, and destructive of autologous tissues. Cytotoxic or killer T-cell lympho¬ cytes generated by this aberrant immune response attack and injure specific organs, sometimes in the total absence of observable serum auto-antibodies. A dimin¬ ished suppressor T-cell activity is believed to result in disordered regulation of immune responses and to allow overactivity of other autoreactive mechanisms, all of which involve functionally abnormal white blood cells circulating within the body of the afflicted subject. Insulin-dependent diabetes mellitus (IDDM) appears to have an autoimmune pathogeneεis in human. It is a pathological disorder in which the body's own lympho¬ cytes destroy the insulin producing beta cells located in the pancreas. Individuals having IDDM are dependent upon injections of insulin for the rest of their lives. Insulin therapy now prevents the early deaths from ketoacidosis that were formerly inevitable; and has substantially extended the life expectancy of these people. Insulin treatment, however, does not prevent the later complications of chronic diabetes. These complications include diseases of the heart, kidneys, eyes and the nervous system. The life expectancy for an individual developing diabetes at age 14 is all too often less than 25 or 30 years. At this time, there is no generally accepted, safe way to prevent the disease or reverse it once pathogenesis has begun.

The cause of IDDM is unknown. While there is evidence to support involvement of viral illness in some instances, most contemporary data indicate that an immunological disorder which is at least partially cell-mediated is involved (Rossini et al. , Ann. Rev. Immunol. 3:289-329 (1985)). Morphologically, "insuli- tis" defined as an inflammation surrounding the insulin producing beta cells of the pancreas is often found at the time of disease onset. Abnormalities of both the cellular and humoral components of the immune system are present. For example, islet cell cytoplasmic antibodies and islet cell surface antibodies are found at the time of clinical diagnosis in children and have been detected in some individuals long before the onset of the clini- cal symptoms. Cellular immune functions are also altered. Activated T-cell lymphocytes capable of cytotoxic function normally, circulate in increased numbers in instances of acute IDDM. Defects in sup¬ pressor cell activity and alterations in the production of lymphokines such as interferon and interleukin-2 have been reported in diabetic children (Baratano et al. , Diabetol. .19:255 (1980); Zier et al. , Diabetes 33:552 (1984)). Lymphocytes from acutely diabetic children that are co-cultured with human beta cells (from an insulin-producing tumor) are reported to have killed the tumor cells (Huang and McClaren, Science 192:64 (1976)). In addition, it is now recognized that immunosuppressive therapy using cyclosporine can ameliorate IDDM if the drug is given at the time of disease onset. Unfortu¬ nately, lifelong drug treatment may be necessary in order to prevent recurrence of diabetes. There is also the risk of serious long-lasting immune system altera¬ tions caused by long-term immunosuppressive therapy such that the therapeutic regimen could have consequences worse than those of the disease.

Recent research has utilized animal test model systems which are directly comparable to human IDDM. A excellent model for studying IDDM is the BioBreeding (BB) rat (Chappel et al. , Metabolism 32(Suppl. I) :8 (1983)). Inheritable diabetes in the BB rat is charac¬ terized by many metabolic, pathologic and immunologic features directly analogous to those observed in human IDDM (Rossini et al. , Ann. Rev. Immunol. 3_^:289""³²⁰ (1985); Yale and Marliss, Clin. Exp. Immunol 57:1-20 (1984)). Functional abnormalities of cellular immunity have been well documented. Mitogen stimulated spleen cells from acutely diabetic rats adoptively transfer both insulitis and diabetes to various recipient rats. Marked lymphopenia involving all lymphocyte subsets occurs consistently in the BB rat. Activated T-lympho¬ cytes have been reported during the early stages of clinical diabetes and to decrease over time with the course of the disease. The responsiveness of BB lymph¬ ocytes to mitogens is defective and lymphocytic thyroid- itis also occurs in these rats. In addition, abnormal humoral immune regulation in the BB rat is suggested by the presence of islet cell surface antigens and auto- antibodies against thyroid, gastric parietal cells, splenic lymphocytes and smooth muscle. Lastly, it has been demonstrated that islets from resistant BB rats transplanted to spontaneously diabetic rats are rapidly destroyed.

It has also been demonstrated that weekly transfusions of whole blood from nondiabetic rats to susceptible rats reduced the incidence of diabetes and the incidence of pancreatic insulitis (Rossini et al. , Science 219:975-977 (1983)), and that transfusions of lymphocytes from diabetes resistant rats to diabetes prone BB rats prevent onset of the clinical disease in essentially all recipients (Rossini et al. , J. Clin. Invest. 7_4:39-44 (1984)). It is noted that such trans¬ fusions not only prevent diabetes but also restore the depressed mitogenic responsiveness of BB rat lymphocytes.

The recognized difficulty in a therapeutic treat¬ ment based on the transfer of white blood cells from a normal to an afflicted subject lies in the histoincompat- ibility of the transferred cells themselves within the host. Clearly, the HLA antigens of the major histoco - patibility complex (MHC) must be shared between the donor cells and the recipient tissues. Also unknown is the duration and degree of effectiveness which could be achieved by such a direct transfer of donor white blood cells to a subject afflicted with IDDM. Thus, there is a continuing need for a therapeutic method for treating persons having IDDM and other autoimmune diseases.

Summary of the Invention

The present invention is a method for therapeuti- cally treating insulin-dependent diabetes mellitus and other immunological disorders and disease states which are characterized by the presence of immunologically abnormal leukocytes in the body of an afflicted subject. According to the method, a patient is administered a sufficient quantity of postthymic T lymphocytes capable of secreting soluble factors that can ameliorate disease state associated with diabetes or other autoimmune disease. It has now been shown that postthymic T-cells secrete a soluble T-cell differentiation antigen, referred to as RT6 which plays an important role in the immunoregulation of autoimmune diabetes. Thus, it is desirable that the afflicted person be treated with viable, immunologically normal T-cell leukocytes that are able to provide normal T-cell functions and to produce normal, non-antibody, T-cell secretory products, particularly RT6.

The invention also pertains to the method of administering the T-cell solution to a patient using a sealed diffusion chamber which can be implanted or used extracorporeally. The diffusion chamber is designed to deliver T-cell secretory products, such as RT6, to a preselected site within the afflicated person to ameliorate disease state or disorders associated with the presence of immunologically abnormal leukocytes in the body.

Brief Description of the Figures

Figure 1 is an overhead view of one preferred embodiment of the present invention.

Figure 2 is a cross-sectional view of the embodi¬ ment of the present invention.

Figure 3 is a overhead view of a plurality of sealed diffusion chambers joined together as a unit for implantation in vivo.

Figure 4 is a cross-sectional view of the embodi¬ ment illustrated within Figure 3.

Figure 5 is an overhead view of an active diffu¬ sion chamber suitable for implantation in vivo with a blood vessel of the subject.

Figure 6 is a cross-sectional view of the embodi¬ ment illustrated by Figure 5.

Figure 7 is an overhead view of a preferred embod¬ iment of an active diffusion chamber useful as an implant with a blood vessel off the subject.

Figure 8a and 8b are cross-sectional views of the embodiment illustrated by Figure 7.

Figure 9 is an overhead view of an extracorporeal embodiment of the present invention intended to be externally joined to the circulatory system of the subject. Detailed Description of the Preferred Embodiments

The present invention pertains to a method for therapeutically treating insulin-dependent diabetes mellitus and other autoimmune diseases and disorders. These immunological disorders and pathological disease states are typically characterized by the presence of functionally abnormal white blood cells within the body of the afflicted subject. The present invention is based upon the discovery that clinically observable conditions and symptoms of such immunological disorders and disease states can be counterbalanced by the pres¬ ence of immunologically and functionally normal white blood cells which, after interaction, are able to release a variety of different secretory products which aid in the regulation of the immune system; can prevent the onset of the clinical disease and, in some in¬ stances, restore normal function to injured tissues and organs within the afflicted subject.

It has now been shown that normal post-thymic T-lymphocytes secrete a T-lymphoσyte differentiation antigen, referred to as RT6 which has been shown to play an important role in prevention of insulin-dependent diabetes mellitus. As shown in the examples, administration of the RT6 antigen to a diabetes susceptible rat substantially prevented the onset of diabetes in the rat model. The RT6 antigen is a nonglycosylated 21kd protein that is anchored to the cell via the 1,2-diacylglycerol moiety of phosphatidylinositol or a closely related lipid. Thiele, H.-G. et al. , Immunology 59:195(1986); Koch, F. et al. , J. Exp. Med. 164:1338(1986) . It is expressed on approx. 70% of the peripheral T-cells of rats. Greiner, D.L. et al. , in Frontiers in Diabetes Research, (Shafrir and Renold, Eds.), J. Libbey and Col., Ltd. pp. 61-67 (1988) . RT6 has two known alleles, RT6a and RT6b, which encode the RT6.1 and RT6.2 alloantigens, respectively. Greiner D.L. et al. , J. Immunogenetics 53:43(1982); Gill, T.J. , et al. , Transplant Proc. 15:1683(1983).

According to the invention, normal leukocytes interact within a sealed diffusion chamber to release secretory products and soluble factors, such as the RT6 antigen, which function as chemical mediators to counterbalance the effects and pathology of the disease or disorder. The methods of the invention are carried out by obtaining a sealed diffusion chamber of definable configuration and internal volume comprising at least one semi-permeable membrane and a suspension of immuno¬ logically normal leukocytes, the semi-permeable membrane retaining the leukocyte suspension within the diffusion chamber while allowing non-cellular materials and fluids to pass therethrough, the leukocytes in the suspension being demonstrably able to provide such cell functions and secretory products which therapeutically counter¬ balance the effects of the immunological abnormality within the afflicted subject; and implanting the sealed diffusion chamber at a preselected site within the afflicted subject. Alternatively, the sealed diffusion chamber can be extracorporeally joined to the circula¬ tory system of the afflicted subject. It is preferred that the suspension of leukocytes within the diffusion chamber be adult, pre-stimulated leukocytes of deter- minable type and preferably include specific T-cell populations from cloned cell lines or cells from human donors which have been enriched prior to use.

Initially, it must be recognized that not all autoimmune disease states are cell-mediated disorders in which immunologically abnormal, functionally deficient, non-antibody producing cells are clinically observable within the afflicted subject. Clearly, disorders involving B-lymphocytes and their direct precursor cells are not within this class of immunological disorder and disease. Similarly, several autoimmune diseases are recognized as being caused by humoral auto-antibody in the absence of cell-mediated autoimmunity. Represen¬ tative examples of humoral antibody-mediated auto¬ immunity include hemolytic anemias, idiopathic thrombo- cytopenia and Goodpasture's syndrome, all of which are presently believed to be mediated solely by auto-anti¬ bodies directed against autologous cell membrane consti¬ tuents. In these diseases, it is the antibody which attaches to the cell membranes, fixes complement and causes severe injury to the cell. Alternatively, antireceptor auto-antibodies are believed to either stimulate or suppress target cell function.

In comparison, those immunological disorders and disease states which are cell-mediated typically present immunofunctionally abnormal leukocyte whose characteris¬ tics include some or all of the following: a poor or totally absent response to mitogens, such as Concanavalin A (hereinafter "CON A") ; a diminished or total inability to produce lymphokines or other soluble cytokinetic secretory products, such as interleukins and interferons; an impaired ability to react to foreign-antigens by mixed lymphocyte reaction; a reduced delayed type hypersenstivity reaction; identifiable alterations and changes in cell activation and formation of cytotoxic cells; a reduced or altered ability to aid those cells directly involved in immunoglobulin synthesis or antigen processing for antibody production; an altered or diminished ability to synthesize polypeptides and proteins; an inability to release secretory products normally obtained from the cell; and/or an altered HLA or MHC cell specificity or type.

The present invention is therapeutically effective for those immunological disorders and diseases in which leukocytes in the body of the subject demonstrate one or more of these immunofunctional abnormalities or immunologically deficient characteristics identified above. The presence of such functionally abnormal or deficient white blood cells circulating within the afflicted subject identifies that pathological state to be one susceptible to treatment using the present invention. The invention is particularly effective for treating patients having insulin-dependent diabetes mellitus.

The invention can also be used for screening and/or detecting insulin-dependent diabetes comprising measuring the level of soluble RT6 antigen in a biological fluid (e.g., serum) or cellular lysates and comparing the level obtained to predetermined levels as indicative of the presence and extent of the disease or absence of the disease. For instance, the presence of soluble RT6 in mammalian cells can be determined at the molecular level using cDNA probes and known molecular techniques to generate mRNA, protein products and antibodies thereto. Rat cDNA probes have been described in Koch et al. , PNAS USA 7:964-967 (1990) and have been shown to be cross-reactive with human DNA at the molecular level. Antibodies specific for the protein coded by the mammalian and human RT6 gene can be raised and used for detecting the presence or absence of soluble RT6 in the individual.

Clinical disorders amenable to treatment using the methods of the present invention include but are not limited to diabetes mellitus, an affliction in which there is a demonstrated deficiency in the production of interleukin-2 (hereinafter "IL-2") , a secretory product of lymphocytes; AIDS, a disease in which a functional

+ deficiency of CD4 helper T-cells has been found and in which there is a decreased production of lymphokines; multiple sclerosis in which alterations in helper and suppressor T-cells have been observed; rheumatoid arthritis, cell-mediated destruction of synorium; Addison's disease, cell-mediated destruction of adrenals; vasculitis; progressive multifocal leukoen- cephalopathy; thymic hypoplasia (DiGeorge's syndrome) ; Wiscott-Aldrich syndrome; Grave's disease; ankylosing spondylitis; and secondary, cell-mediated immunode¬ ficiencies associated with sarcoidosis and Hodgkin's disease. It will be recognized and appreciated that many other immunological disorders and disease states which are at least partially cell-mediated can be therapeutically treated by the present invention to counterbalance the effects of the immunological abnor¬ mality within the afflicted subject. In this regard, the term "to counterbalance" as used herein will be recognized and understood to be employed in its most general connotation and applica¬ tion and includes the more specific conditions of: "to compensate" - that is, to be equivalent to or to supply an equivalent; "to counteract" - that is, to make effective or to mitigate the ill effects of; "to neu¬ tralize" - that is, to nullify or destroy the effect of; "to control" - that is, to regulate or to exercise a restraining or directing influence over; and "to reverse" - that is, to turnabout or place in the oppo¬ site direction. Clearly, the term "counterbalance" and the counterbalancing effect of the invention will thus vary with the particular affliction, the degree of injury to the cells, tissues and organs of the subject already incurred, and the progression of the patholog¬ ical state for the specific disorder. While the entire range of remedial conditions and benefits may be obtain¬ able in one individual under certain instances, it is expected and envisioned that a broad range of corrective reactions leading to a complete remission or cure of the disorder is not likely using the present invention alone. For this reason, it is expected that the methods described herein will comprise but one part of an overall therapeutic regimen which includes conventional pharmaceuticals and drugs, and other therapeutic treatments.

In one embodiment of the present invention, secretory factors, such as RT6, can be delivered to the patient by surgically implantable diffusion chambers or extracor oreal diffusion chambers of a definable configuration and internal volume. A wide variety of diffusion chambers for ^n vivo use of various construction, materials, sizes and internal volumes are conventionally known (Carsten, A.B., Bil. Haemat. 4jB:32l-365 (1984)). Such diffusion chambers comprise at least one semi-permeable membrane whose pore size (diameter of the aperture or hole) and porosity (total void volume) will vary with the intended application. Well described and commercially available porous membrane filters, composed of various compositions including acrylic resins, cellulose-acetate, cellulose-nitrate, nylon, polycarbonate and other mixed esters fibers are commonly employed. Such semi-permeable membranes form at least one wall of the diffusion chamber and are sealed (by adhesives, heat, ultrasound and the like) into the diffusion chamber construction in a leak proof manner. The formed diffusion chamber can take a wide variety of different shapes and orientations and will be constructed with an internal volume to meet the requirements of the intended application. With embodiments intended for human use, it is desirable that the internal volume of the diffu¬ sion chamber be from 10-200 cubic centimeters and that the effective diffusion distance be not greater than 1.0 millimeters. It is expected that prior to in vivo implantation or extracorporeal use, the formed chamber will be sterilized using ethylene oxide, gamma radia¬ tion or other conventional, non-destructive techniques.

The essence and unexpected therapeutic benefits provided by the methods of the present invention lie in the selection and use of the non-antibody producing leukocytes suspended within the internal volume of a sealed diffusion chamber. Clearly, the semi-permeable membrane of the sealed diffusion chamber will retain the leukocyte suspension internally within the interior of the diffusion chamber while allowing non-cellular materials and fluids to pass therethrough. In this manner, nutrients, salts and body fluids can pass through the membrane into the interior of the chamber for reaction with the leukocyte suspension while the soluble secretory products released by the leukocyte suspension may flow out from the diffusion chamber into the body of the afflicted subject. The requirements for the semi-permeable membrane are to act as a physical barrier to retain the leukocyte suspension within the interior of the diffusion chamber while allowing non-cellular materials and products to pass unhindered; and to prevent antibodies of the host from penetrating the interior of the chamber and destroying the donor leukocytes. So long as these requirements are met and satisfied, neither the chemical composition of the semi-permeable membrane; nor the pore size of the membrane; nor the porosity of the membrane employed, is of any consequence.

The nature or composition of the cells comprising the leukocyte suspension sealed within the diffusion chamber is thus of paramount interest. Experiments have demonstrated, as will be described hereinafter, that a mixture of immunologically normal and functional white blood cells of the types and in the proportional ratios similar to that of white blood cells circulating in the body of normal individuals is both operative and functional as a therapeutic treatment and as a preventative measure of human disease conditions known or believed to involve immune system abnormalities. For humans, such a leukocyte mixture comprises: 36-66% neutrophils; 24-44% lymphocytes; 2-8% monocytes; 1-3% eosinophils; and 0-3% basophils.

A preferred alternative leukocyte mixture will comprise a blend of unselected T-cell lymphocytes obtained from an immunologically normal donor. T-cells may be separated from B cells using conventional methods. The entire T-cell lymphocyte population would then be prepared as a suspension in saline, physiologi¬ cal buffer, or a supportive nutrient medium and be introduced into the interior of the diffusion chamber for use. This T-cell lymphocyte population is unselected in that no ratios or specific subpopulations of T-cells have been identified or purposely included within the suspension. Such mixtures of unselected T-cells will provide a wide variety of immunofunctional T-cell lymphocytes of varying characteristics and antigenic specificities which will then interact as individual cells and subsequently release active secretory products such as various lymphokines into the fluid suspension medium. Such secretory products will pass unhindered through the semi-permeable membrane directly into the tissues and cells of the afflicted individual.

In another embodiment, specific T-cell lymphocyte subpopulations which have been identified by specific antisera and whose relative concentrations or ratios are controlled to be within predetermined limits can be used. Accordingly, the leukocyte suspension comprises a predetermined concentration of known T-cell subpopulations which are blended in a predetermined concentration ratios to provide an enriched or enhanced concentration of specifically desired T-cell subpopula¬ tions. It is expected that enriched concentrations of T4 helper/inducer cells and T8 suppressor/cytotoxic cells will dominate such enriched T-cell leukocyte suspensions. In addition, as further information regarding additional T-cell subpopulations (there now being approximately 19 identifiable T-cell subpopula¬ tions) are found and as new immunological and cellular functions are recognized for each specific T-cell subpopulations, that the choice of T-cell subpopulation types and the respective concentrations of each within the leukocyte suspension will be altered to meet specific immunological disorders and disease states. All such variations in T-cell subpopulation selection, ratio of subpopulation concentration, and mode of interaction between different specific T-cell subpop¬ ulations, are deemed to be within the scope of the leukocyte suspensions generally useful within the present invention.

Another expected embodiment of the leukocyte suspension will utilize specific T-cell subpopulations which are maintained as individual cell lines and cloned using conventionally known techniques to provide a pure strain of cells. Clones of specific T-cell subpopulations allow the user to maintain individual cell lines of uniform characteristics; of known antigenic specificity; having established receptor sites on the cell surface; and having proven ability to interact with other specific T-cell subpopulations when in a mixture. This provides the user with an added degree of choice and control in blending specific T-cells of desired characteristics and in making a leukocyte suspension for use within the diffusion chamber such that specific secretory products can be expected to be synthesized in advance by virtue of having combined specific T-cell clones.

Regardless of the precise composition of the leukocytes employed in the suspension, the present invention relies on the interaction of these cells and the ability of these cells to release secretory products into the fluid suspension medium. It is the release of such lymphokines and other soluble cell products which act as the therapeutic agents in counterbalancing the effects of the immunological disorder or disease and which aid in preventing further injury to the cells and tissues of the afflicted individual. There is no information avail¬ able at this time to describe the true mechanism of action by which the release of such cytokines or other secretory products act as chemical mediators jji vivo. Interleukins and inferferons are only two examples of this rapidly expanding class of mediator molecules. The invention, however, relies on the release of at least one distinct secretory product, usually in soluble form, which is the result of intrinsic leukocyte activity or leukocyte interaction within the diffusion chamber. Preferably, the soluble factor is the RT6 antigen. The released secretory products will then pass through the semi-permeable membrane of the diffusion chamber and in this manner, be physiologically released into the body of the subject. Such secretory product transfusions are effective not only in treating clinically identifiable diseases such as diabetes, but also in restoring much of the original function to the immunodeficient white blood cells circulating within the afflicted subject. The sealed diffusion chamber, whether surgically implanted or attached as an extracorporeal device, acts as the means for compartmentalizing the prepared leukocyte suspension and physically separates them from their host counterparts. The semi-permeable membranes allow the host to provide fluids and nutritional materials necessary for cell growth while preventing direct donor-recipient cell to cell interaction. These in vivo methods thus provide means for therapeutically treating immunological defects and abnormalities under physiological conditions in a manner which does not further the progression of the disorder/disease and allows for continuous action of the donor cells for indefinite periods of time. It will be recognized, that by segregating the leukocyte suspension to the interior of the sealed diffusion chamber, the histo- compatibility of the donor cells (with relation to the host recipient) becomes immaterial and inconsequential; moreover, because it is solely the secretory products of activated normal leukocytes which act on the affected cells and tissues of the recipient, there are no undesired reactions, new antibodies, or any other immune response by the host's cells and tissues. It will be recognized also, especially in the extracorporeal embodiments of the present invention, that the donor cells can be replaced as frequently as desired with or without a preset schedule; similarly, the implanted diffusion chambers may be removed without major injury or discomfort to the host.

Some preferred embodiments of the present inven¬ tion utilize a semi-permeable membrane as a sealable diffusion chamber without need for any other material or housing construction. Such sealable diffusion chambers comprise semi-permeable hollow fibers composed of polysulfone or acrylic copolymer which have an internal diameter ranging from 300-2,000 micrometers (hereinafter μm) , are approximately 4-7 centimeters long, and whose membranes have a wall thickness ranging from about 50-110 μm. Such fibers are useful individually and as part of the artificial capillary systems (Vitafiber) , manufactured and sold by Amicon Corporation. The pore size of these hollow fiber, semi-permeable membranes will retain molecules ranging between about 10,000-100,000 daltons. Hollow fiber membranes with a mean pore size of 70 Angstroms (corresponding to a cut-off of approximately 80,000 daltons) have been found useful in most applications. When the lumen of these hollow fibers are filled with leukocytes from the immune system of normal donor individuals and the ends of these tubes are subsequently sealed, a passive diffusion chamber is formed. The physical characteristics of the sealed hollow fiber, semi-permeable membranes assures that nutrients can diffuse freely into the interior of the hollow fiber; that the leukocytes within the internal volume of the chambers are protected from destruction by host cells and host immunoglobulins; and that the secretory products released by the cells within the hollow fibers diffusion chamber can diffuse into the host tissues. These hollow fiber membranes have been shown to be well tolerated in vivo and to be non-toxic after implantation in living recipients.

The preferred embodiment of the sealed diffusion chamber employing such hollow fiber membranes is illustrated by Figs. 1 and 2, respectively. As seen therein, a semi-permeable membrane formed in the shape of a hollow fiber tube 10 appears whose ends 12, 14 are tapered and sealed (preferably by heat or ultrasonic welding) . The seals 16, 18 ensure that the leukocyte suspension 20 remains within the lumen 8 of the hollow fiber 10. The embodiment illustrated by Figs. 1 and 2, respectively, is particularly useful for surgical implantation in vivo, especially at a subcutaneous site. Another embodiment is illustrated by Figs. 3 and 4, respectively. As seen therein, a plurality of sealed semi-permeable hollow fibers 50, 60, 70, 80 and 90, respectively, are jointed together by a pair of restraints 40, 42 to form a bundle. Within the lumen of each sealed hollow fiber tube 52, 62, 72, 82, and 92, are a series of leukocyte suspensions 54, 64, 74, 84 and 94, respectively. The prepared bundle may be implanting using standard surgical procedures at any preselected site in a recipient host.

It is envisioned that under specific circum¬ stances, the rate at which the secretory products are released from the leukocyte suspension within a sealed diffusion chamber may be too slow to provide effective therapy. Such passive diffusion chambers rely on concentration gradients, natural diffusion, and the passive flow of fluids into and out of the diffusion chamber to transport the released secretory products to the areas in the host's body where they will be therapeutically effective. For more rapid release and active distribution of secretory products directly into the circulatory system of the afflicted individual, the embodiment illustrated by Figs. 5 and 6 is preferred. As seen therein, a cylindrically shaped culture tube 100 formed of a biocompatible, non-toxic material houses a plurality of individually sealed diffusion chambers 102. Sealed within each of these hollow fiber diffusion chambers is a leukocyte suspension 104 able to interact and to release cellular secretory products. Each end of the tube 100 is enclosed by a tubing connector 106, 108 and from which extends a blood vessel attachment support 110, 112. This embodiment is intended to be surgically implanted into a blood vessel. The selected blood vessel is surgically severed and each end is attached to a support 110, 112 directly such that the blood exiting the vessel enters the interior of the culture tube 100 and bathes the plurality of semi-permeable diffusion chamber 102. The pressure within the blood vessel will cause a partial pressure and fluid flow axially through the culture tube 100 such that the secretory products released by the leukocyte suspension within the fibers 102 become rapidly transported by the blood fluid passing through the semi-porous membrane material and flowing out of the culture tube 100 back into the host's circulatory system. While the blood circulatory system is preferred as the site of implanation, it is recognized that the active diffusion chamber illustrated by Figs. 6 and 7 may also be placed within the lymphatic fluid system of the individual to achieve equivalent effect.

A preferred format for the active diffusion chamber to be positioned in-line with a blood vessel for rapid distribution of released secretory products is the embodiment illustrated by Figs. 7, 8a and 8b, respectively. Figure 8a is a cross-sectional view along the line AA of Fig. 7; Fig. 8b is a cross-sectional view along the line BB of Fig. 7. This embodiment is most desirable because this format maintains the linear blood flow of the blood uniformly throughout the entirety of the diffusion chamber from end to end. This allows the blood pressure of the system to be kept near its original level and avoids the risk of subsequent complica¬ tions in the body typically caused by interruptions of laminar blood flow.

As seen in Figs. 7, 8a and 8b, a cylindrical shaped tube 160 houses a plurality of axially posi¬ tioned hollow fiber membranes 162 which are indi¬ vidually joined and sealed fluid-tight to individual aperatures 166 in circular support plates 168, 170 positioned at each end of the tube 160. The integrity of the lumen 164 of each hollow fiber membrane within the tube 160 is maintained and each lumen serves as a fluid pathway for the blood through the interior of the tube 160. At each end of the tube is a filling chamber 172, 174, each of which includes a blood vessel attachment 176, 178. Filling the interior 158 of the tube 160 and surrounding the external surfaces of the axially positioned hollow fiber membranes 162 is a prepared leukocyte suspension 180. In the normal course of use, blood exiting the blood vessel joined to the attachment 176 enters the filling chamber 172 and is confronted by the support plate 168 presenting the open ends and lumen of the hollow fiber membranes 162. The blood enters the lumen 164 of each hollow fiber membrane 162 through the aperatures 166 in the support plate 168. The blood then flows through the length of the axially positioned membranes 162 within the interior 158 of the tube 160 to the other support plate 170. The secretory products synthesized and released by the leukocyte suspension 180 within the interior 158 of the tube 160 flow into the hollow fibers 162 and are transported by the blood flowing tangentially through the lumen of the fiber membranes. The blood pressure is maintained through the entirety of the tube 160 and the blood exits the diffusion chamber through the aperatures 166 of the support plate 170 into the filling chamber 174 and re-enters the blood vessel via the attachment 178.

The extracorporeal form of the apparatus used in the present methodology is illustrated by Fig. 9, or alternatively by Fig. 7. The extracorporeal embodi¬ ment is intended to be used when there is a recognized causative agent active and present within the afflicted individual at the time therapeutic treatment is initiated. Such a situation is the AIDS patient. As illustrated by Fig. 9, a plurality of sealed hollow fiber semi-permeable membranes serving as diffusion chambers 200 is contained within a cylindrically shaped housing 202. At each end of the housing 202, is a catheter closure 204, 206, each of which terminates as a catheter 208, 210 for direct connection to the circulatory system of the afflicated individual. This extracorporeal diffusion chamber utilizes the blood pressure of the recipient to propel fluid through a catheter 208 into the interior of the housing 202 and to bathe the leukocyte suspensions within the sealed diffusion chambers 200. The pressurized fluid flow will actively remove released secretory products of the leukocyte suspension from within the diffusion chambers 200 and cause them to flow through the end 206 and the return catheter 210 into the blood system of the recipient. In this manner, the release secretory products produced within the sealed diffusion chambers are actively removed and transported from within the chamber housing at a rate far greater than that provided by passive diffusion and other passive transfer mechanisms.

The invention will be further illustrated by the following examples which are not intended to be limiting in any way:

Example 1 The BB/W rat develops spontaneous autoimmune diabetes which is characterized by many metabolic, pathologic, and immunological features similar to those observed in human insulin dependent diabetes mellitus. Rossini et al. , Ann. Rev. Immuno1. .3_^:289~³²⁰ (1985); Yale and Marliss, Clin. Exp. Immunol. 57:1-20 (1984) . These rats are of normal body weight, and both sexes are equally susceptible. At the time of disease onset, diabetic ketoacidosis invariably occurs and is lethal unless treated with insulin. Daily insulin injections are needed to keep affected rats alive. The disorder does not appear to be the result of an infection, and no environmental factors that consistently affect the incidence of diabetes have yet been described.

While the etiology of BB rat diabetes is presently unknown, abnormalities of cellular immunity are well documented. Mitogen stimulated spleen cells from acutely diabetic rats adoptively transfer both insulitis and diabetes to various recipient rats. Marked lymphopenia involving all lymphocyte subsets occurs consistently in the BB rat. Activated T-lymphocytes have been reported to occur during the early stages of diabetes and to decrease with time. The responsiveness of BB lymphocytes to mitogens is defective and lymphocytic thyroiditis also occurs in these rats. Lastly, it has been demonstrated that islets from resistant BB rats transplanted to spontaneously diabetic rats are rapidly destroyed.

Spleen cells from normal Wistar Furth (WF) rats were suspended in supplemented RPMI medium by mechanical dispersion as described in Rossini et al. , J. Clin. Invest. 2i.^:39"⁴⁴ (1984). Wistar Furth rats of various ages and sex were used as donors because they do not become diabetic. The spleens were removed by sterile technique and mechanically disrupted with an autoclaved garlic pressed. Extruded spleen cells were collected in 10 ml of RPMI medium and the volume of the suspension increased to 45 ml with additional RPMI medium. Subsequently, the cells were centrifuged at 1200 x gravity for 10 minutes; washed with saline; and the cells resuspended in RPMI. The cells were then used as freshly prepared or after culturing for 72 hours with 5 μg/ml Con A.

A series of sealed diffusion chambers containing a mixed leukocyte suspension comprising the WF rat spleen cells were prepared. Semi-permeable hollow fibers which are inner-sponge, and have an outer-skin membrane with a mean pore size of 70 Angstroms (which corresponds to approximately 80,000 daltons in molecular weight) were utilized. These hollow fiber semi-permeable membranes were obtained from the Amicon Division of W.R. Grace, Inc. (Lexington, Massachusetts) . These hollow fibers have approximately 1,000 μm diameters and a length of approximately 5.0 centimeters.

A cell suspension of 100-150 x 10 cells/milliliter was introduced into the lumen of each hollow fiber by capillary action and the diffusion chamber sealed by joining each end with Amicon solvent. Approximately 5.0 centimeter length tubes were utilized for ease of handling and maximum length for easy positioning internally within 30 day old BB rats. Each recipient BB rat received four individual fibers or diffusion chambers implanted into the peritoneal cavity by conventional surgical techniques. 29 BB rats received Con A activated spleen cells within their respective diffusion chambers while 10 BB rats received fresh (non-stimulated, non-cultured) spleen cells within their respective diffusion chambers. 11 control BB rat recipients received untreated, empty hollow fibers. In addition, 40 BB rats received no treatment whatsoever, but were evaluated as negative controls. All the rats were clinically tested for evidence of diabetes through 120 days of age. It is recognized that selective beta cell destruction and clinical diabetes occurs by 120 days of age in about one-half of all BB rats. The results are present by Table I below.

TABLE 1

RAT GROUP AND NUMBER NUMBER OF % DIABETIC CONDITION TESTED DIABETIC RATS RATS

Con A Activated 29 WF Spleen Cells

Fresh, Untreated 10 10 WF Spleen Cells

Empty Chamber 11 55

No Treatment 40 19 48

This experiment clearly indicates that the secretory products released by the leukocyte suspension contained within the hollow fiber diffusion chambers can prevent the onset of clinical diabetes. It is the release of these secretory products such as soluble factors or other lymphokines which accounts for the protection and for the counterbalancing effect. The sealed diffusion chamber, however, is not subject to either specific or non-specific host defenses and provides much greater protection over an enduring period of time than can be accomplished by direct transfer of white blood cells from the donor into the circulation of the afflicted subject.

Example 2

Donors Animals: Non-diabetic Diabetes Resistant (DR) (RT6.1⁺) BB/Wor and Wistar Furth WF) (RT6.2⁺) rats between 90 and 120 days of age.

Recipients Animals: DR rats 30 days of age each received implanted chambers and hybridoma supernatants containing an anti-RT6.l lymphocytotoxic monoclonal antibody. This antibody is specific for the RT6.1 alloantigen and does not affect RT6.2 cells. The schedule of treatment was 2.0ml intraperitoneally five times per week for up to four weeks or diabetes onset. Rats were tested for glycosuria (Lilly Testape 4+) twice weekly. If positive, hyperglycemia (>200mg/dl) was verified using the Beckman Glucose Analyzer.

Chambers: Semiperimeable hollow fibers (Amicon Division of W.R. Grace, Inc. Lexington, MA) were composed of acrylic polymer membranes with a mean pore size of 70 Angstroms which corresponds to approximately 80,000 Dalton molecular weight. The hollow fibers were inner-sponge and outer-skin membranes. After filling the fibers, the ends of the chambers were sealed using either heat compression or cement sealant. Four to seven chambers of three to five centimeters in length having a collective chamber volume of approximately

160mm 3 were implanted i.nto the peri.toneal cavi.ty of each test animal.

Donor Spleen Cells

Spleens were removed from donor rats and cell suspensions prepared by mechanical dispersion in supplemented RPMI media. Suspensions were diluted to cell concentrations of 100 x 10 /ml. Hollow fibers were filled by capillary action, the ends sealed and chambers containing a total of 20 x 10 cells implanted into recipients. Empty chambers served as control.

Results

Although the rats are RT6 deficient and thus prone to onset of diabetes, recipient DR rats treated with RT6 spleen cells did not become diabetic, as shown below in Table 2. In contrast, RT6.1-depleted DR rats which were not treated with soluble RT6-containing lymphocyte populations became diabetic. The results indicate that RT6 is secreted by the spleen cells and is the soluble antigen which is responsible for protecting the rat from onset of the disease.

Table 2

FREQUENCY OF DIABETES IN RT6.1-DEPLETED DR RATS TREATED WITH SPLEEN CELLS SEQUESTERED IN DIFFUSION CHAMBERS

Experimental Number Number Percent

Group Treated Diabetic Diabetic

Empty Chambers

DR (RT6.1⁺)Spleen Cells

WF (RT6.2⁺)Spleen Cells

Example 3 Isolation and Characterization of Soluble RT6 Antigen in Serum

Blood is obtained from 1) Diabetes Prone BB rats, 2) Diabetes Resistant BB rats and 3) Diabetes Prone BB rats given a transfusion of 200 million spleen cells from Diabetes Resistant BB rats to make them resistant to diabetes. The blood was allowed to clot, centrifuged at moderate speed and the serum removed. The serum was then ultracentrifuged twice in tubes containing molecular sizing filters. The first centrifugation employed a filter with a M cuttoff of 100 kD. The material having an M less than 100 kD which passed through the filter was then collected and ultracentrifuged through a filter with an M cuttoff of 30 kD. After the second ultracentrifugation, the material with an M greater than 30 kD which did not pass through the filter was collected. Between 300 and 600 micrograms of protein from this solution were then run on a conventional 12% SDS polyacrylamide gel under nonreducing conditions. The unstained gel fractionated proteins were then blotted on PVDF membranes and probed with rabbit polyclonal antibody that specifically recognizes the RT6 antigen. The membranes were then washed to remove unbound antibody.

The bound rabbit anti-RT6 was then visualized by incubation with 125I labeled protein A followed by conventional autoradiography.

Results: Evidence of soluble RT6 antigen of M 33 kD was found in the serum obtained from Diabetes Resistant BB rats (Group 2) and Diabetes Prone BB rats that had been transfused with spleen cells from Diabetes Resistant BB rats. No soluble circulating RT6 antigen was present in the serum obtained from intact, untreated Diabetes Prone BB rats.

Since it is know that 1) 60-80% of Diabetes Prone BB rats develop spontaneous autoimmune diabetes, 2) that Diabetes Resistant BB rats very rarely (<1% of the time) develop diabetes and 3) that Diabetes Prone BB rats injected with Diabetes Resistant BB rat spleen cells (which contain RT6 T lymphocytes) do not become diabetic, the results indicate that soluble RT6 antigen confers protection from the development of autoimmune diabetes mellitus.

Equivalents

Those skilled in the art will recognize or be able to ascertain, using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. These and all other equiva¬ lents are intended to be encompassed by the following claims:

Claims

1. An isolated soluble RT6 antigen of mammalian origin.

2. The soluble RT6 antigen of Claim 1 that is the RT6.1 or RT6.2 alloantigen.

3. A composition comprising soluble RT6 antigen in a physiologically acceptable vehicle.

4. A composition comprising an effective amount of RT6-containing T cell leukocytes sufficient to ameliorate disease associated with diabetes or other autoimmune disease, in a physiologically acceptable vehicle.

5. A composition of Claim 4, wherein the T cell leukocytes are of human origin.

6. A composition of any one of Claims 3 and 4, for use in therapy, e.g., treating disease state associated with insulin-dependent diabetes or other autoimmune disease.

7. Use of soluble RT6 antigen of Claim 1, for the manufacture of a medicament for use in treating disease state associated with insulin-dependent diabetes or other autoimmune disease.

8. Use of RT6-containing leukocytes for the manufacture of a medicament for use in treating disease state associated with insulin-dependent diabetes or other autoimmune disease.

9. An in vitro method for detecting insulin-dependent diabetes, comprising measuring the level of soluble RT6 antigen within a biological fluid or cellular lysate and comparing the level obtained to predeter¬ mined levels, the amount being as indicative of the presence and extent of the disease or absence of the disease.

10. A method of Claim 9, wherein the biological fluid is serum.

11. A method of Claim 9, wherein the soluble RT6 level is determined using a cDNA probe.

12. A method for treating a person having insulin-dependent diabetes mellitus, comprising administering to the diabetic person an amount of RT6 antigen sufficient to ameliorate disease state associated with diabetes.

13. A method of Claim 12, wherein the RT6 antigen is administered in a physiologically acceptable vehicle.

14. A method of Claim 12, wherein the RT6 antigen is administered to the diabetic person by a surgically implantable diffusion chamber.

15. A method of Claim 12, wherein the RT6 antigen is administered to the diabetic person by an extra¬ corporeal diffusion chamber.