WO1993003728A1

WO1993003728A1 - Xanthine suppression of antigen activation of t- or b-cells

Info

Publication number: WO1993003728A1
Application number: PCT/US1992/007110
Authority: WO
Inventors: Dennis D. Taub; Kenneth J. Blank; Marlena A. Moors; Louis A. Rosenthal
Original assignee: Temple University Of The Commonwealth System Of
Priority date: 1991-08-27
Filing date: 1992-08-24
Publication date: 1993-03-04

Abstract

Antigen-specific or superantigen-induced activation of T- or B-cells is inhibited by 3-alkylxanthines having formula (I) wherein R is selected from the group consisting of hydrogen, methyl, (a) and (b); R1 is selected from the group consisting of hydrogen, methyl, (a) and (b); R2 is selected from the group consisting of C1-C4 straight or branched chain alkylene, preferably methyl; R3 is selected from the group consisting of C2-C6, preferably C2-C4, straight- or branched-chain alkylene; R4 is selected from the group consisting of C2-C6, preferably C2-C4, straight- or branched-chain alkylene; R5 is selected from the group consisting of C1-C3 alkyl; or a pharmaceutically acceptable salt thereof.

Description

XANTHINE SUPPRESSION OF ANTIGEN ACTIVATION OF T- OR B-CELLS

Field of the Invention

The invention relates to inducement of immunosup- pression, by inhibiting antigen activation of T- or B- cells.

Backσround of the Invention Immune Stimulation

Foreign antigens encountered by the immune system stimulate specific antigen responses according to the pathway indicated in Fig. 27. Antigen-specific activation is dependent on accessory cells (Fig. 27, ACC- CELL) which present processed antigenic fragments in the context of major histocompatibility locus class II (MHC- II) molecules. CD4⁺ T-helper cells (T_H) recognize the antigen:MHC-II complex thus formed via /β elements of the T_H cell's T-cell receptor (TCR) . Antigen-specific activation requires the cross-linking of the TCR complex, which results in the secretion of various lymphokines, such as γ-interferon and interleukins. The lymphokines in turn facilitate stimulation and differentiation of antigen-specific B-cells into antibody-forming plasma cells (Fig. 27, P_L) .

Fig. 28 illustrates the activation of the immune system by plant and animal lectins. The term "lectin" refers to a collection of carbohydrate m ltimeric glycoproteins derived from plant and animal sources. Each lectin is distinguished by its specificity for a specific sugar moiety found on cell surface receptors. For example, the plant lectin concanavalin A binds saccharide containing a terminal D-mannose. Phytohemag- glutinin, another plant lectin mitogen, binds N-acetyl- galactosa ine-containing oligosaccharides. Since the exposed portions of many cell surface proteins contain hydrophilic groups, many lectins are able to bind directly to entire subsets of glycoproteins found on T,

B and accessory cells. In this manner, T_H cells may be activated by multiple pathways other than the typical

MHC-II.TCRinteractioncharacteristic of antigen-specific activation. In contrast to the MHC-II- positive accessory cells required for specific antigen activation, lectin-bound ACCs need not be MHC-II-positive. They do not process or alter the bound lectins. Lectin-bound

ACCs polyclonally activate T_H cells independent of antigen specificity, and allow for T_H cell proliferation and secretion of lymphokines. Moreover, in contrast to antigen-specific activation, high concentrations of lectins are able to directly activate T and B cells to proliferate and differentiate even in the absence of accessory cells.

Lectin-stimulated lymphocytes undergo a polyclonal, non-specific transformation and proliferation. Unlike antigen-specific stimulation, wherein only a small fraction of lymphocytes are sensitive to the specific antigen, lectins, for the most part, non-specifically activate major populations of B- and T-cells.

Antigen-specific activation of T- and B-cells, on the other hand, is triggered by antigen binding to antigen-specific receptors. Thus, while the activation of B- and T-cells in response to mitogen stimulation is non-specific andpolyclonal, the specific antigen-induced activation of B- or T-cells is clone-specific.

In addition to activation by antigens and mitogens,

T-cells may be activated by a third class of molecules, known collectively as the "superantigens". The term

"superantigen" has been suggested for certain microbial products and self-antigens.

As a whole, superantigens elicit a variety of biological activities, including mitogenesis of lympho¬ cytes, pyrogenicity and depression of antibody production. They can increase susceptibility of a host to endotoxic shock. Microbial superantigens are not structurally related to the prototypical mitogens, plant lectins (discussed above) , and do not aggregate lymphocytes. They do not appear to bind to simple car¬ bohydrate sites on cell-surface glycoproteins. Super¬ antigens as a class, to some extent, resemble T-cell mitogens in that they stimulate a large proportion of T- cells. They do not, however, activate as large a proportion of T-cells as do the stimulatory plant lectins. This is because superantigens do not appear to bind to simple carbohydrate sites on cell surface glycoproteins, as do mitogens.

T-cell receptors for antigenic peptides bound to MHC proteins are made up of five clonally variable com¬ ponents, B_α, Jα, V_p, D_p, and J_p, as well N-region amino acids contributed by nongermline-encoded bases inserted at the junctional points between V_α and J_a, between V_β and O_p, and between D^ and J^. In contrast to the prototypical plant lectins, conconavalin A and phytohaemagglutinin, which have the ability to stimulate all T-cells, bacterial superantigens stimulate only T- cells which bear particular V_p elements within their antigen-specific /β TCR complex. Superantigen stimulation of T-cells occurs almost exclusively via the V_β region of the TCR.

Superantigen activation of the immune system is illustrated in Fig. 29. Superantigens are completely separable from T-cell mitogens in that they share a property associated with specific antigens, i.e., they requireMHC class II-bearing antigen-presenting accessory cells for stimulation. Superantigens combine with MHC-II molecules on accessory cells to form ligands capable of inducing a proliferative response in CD4⁺ T_H cells bearing the appropriate V_β elements within their TCR complex. The thus-activated T_H cells secrete lymphokines which assist in T- and B-cell activation and differentiation.

While mitogens have no role in the etiology of disease, several superantigens, as more particularly pointed out below, have been implicated in human disease. Superantigen activation of T-cells provokes the release of various T-cell factors which contribute to the pathology of the disease state. Superantigen occurrence has been observed in bacteria and viruses, and probably exists in fungi as well.

Microbial superantigens identified to date include the staphylococcal enterotoxins (SEs) produced by Staphylococcus aureus (White et al. , Cell. 56, 27 (1989); Marrack et al. , .Exp.Med. 171, 455 (1990)); strep- tococcal protein toxins having activity on the immune system, such as toxic shock syndrome toxin (TSST-1) (Choi et al. , J.Ex .Med. 172, 981 (1990); Norton et al.. J.Immunol. 144, 2089 (1990)) ; the streptococcal pyrogenic exotoxins (SPEs) A and C (Barsumian et al.. Infect.Immun. 22, 681 (1978); I anishi et al. , J.Immunol. 145, 3170 (1990) ) ; staphylococcal erythrogenic toxin A (Marrack et al. , Nature 349, 524 (1990); Fleischer et al.. J.Immunol. 146, 11 (1991)) ; Group A streptococci M proteins (SMPs) , a group of closely related proteins emanating from the terminal α-helical coil fibrils of Streptococcus pyoσenes (Kotb et al.. J.Cell Biol. 109, 29a (1989) ; Kotb et al.. .Immunol. 145, 1332 (1990); Tomai et al.. J.Exp.Med. 172, 359 (1990)); Pseudomonas aerocrinosa exotoxin A (Misfeldt et al.. Infect.Immun.. 58, 2409 (1990); Misfeldt et al.. Infect.Immun. 58, 978 (1990)); and a Myoplasma arthriditis-secreted protein (Cole et al. _f .Immunol. 144, 420 (1990) ; Cole et al.. J.Immunol. 144, 425 (1990)).

Bacterial superantigens are generally regarded as being responsible for numerous common pathological condi¬ tions. The SEs constitute a family of bacterial super¬ antigens with related biological effects on the immune system. The purified SEs are relatively low molecular weight hygroscopic proteins of 27-30 kDa that are produced by certain strains of Staphylococcus aureus.

All seven of the SEs have been isolated and characterized: SEA, SEB, SEC^ SEC₂, SEC₃, SED and SEE (Bergdoll, "Enterotoxins" in Staphylococci and

Staphylococcal Infections. 2.C., S.F. Easman and C. Adlam

(eds.) Academic Press, London, p. 559).

Staphylococcal food-borne intoxication represents approximately one-fourth of all food poisoning outbreaks. Intoxication results from the ingestion of SE-contamina- ted food. Minute amounts, e.g. 100 ng of SEA, have been found sufficient to cause food poisoning in sensitive individuals. An estimated 3.5 ng is required to cause illness in the average male adult. The SEs mediate enterotoxic effects such as diarrhea and emesis. The SEs are unusually resistant to proteolysis and heat inactivation. It is likely that some or all of the pathological effects of these toxins are caused by their ability to quickly activate so many T-cells. Menstrual toxic shock syndrome is believed mediated by TSST-1. The latter triggers the proliferation of T- cells, resulting in the release of syndrome-causing fac¬ tors. Non-menstrually associated toxic shock syndrome has been associated with the occurrence of other staphylococcal toxins, primarily SEB. Other staphylococcal superantigens have been implicated in toxic shock and toxic shock-like diseases. It is believed that these pathological superantigens cause massive stimulation of the immune system leading to the activation of several immunological pathways leading to the production of large quantities of various cytokines. Recent results suggest that activated T-cells produce or induce cytokine production which are believed to be responsible for the clinical syndrome observed. The reported biological activity of the streptococ- cal pyrogenic exotoxins (SPEs) are similar to those of the SEs. SPE-A and SPE-B have been sequenced; they are homologous to SEA. The SPEs have modes of action similar to other staphylococcal-derived toxins.

Group A streptocci may evoke autoimmune disease in a susceptible host that can affect the heart, namely rheumatic fever. The major virulence factor of these organisms appears to be the surface antigen M proteins (SMPs) , which are a group of closely related proteins emanating from the terminal αt-helical coiled coil fibrils of Streptococcus pyoqenes (Phillips et al.. Proc.Natl. Acad.Sci. USA 78, 4689 (1981)). A number of these M proteins have been cloned and sequenced. Purified streptococcal M proteins stimulate human T cells to undergo brisk proliferation. SMP plays a pivotal role in the pathogenesis of rheumatic fever and rheumatic heart disease. Certain serotypes of SMP contain epitopes that mimic host antigen and therefore can generate autoreactive antobodies.

Pseudomas aeruqinosa is a common and often life- threatening pathogen of immunocompromised hosts (e.g., leukemia, thalassemias, or burn patients) and cystic fibrosis patients. The organism produces several potential virulence factors, the most toxic of which is Pseudomonas aeruqinosa exotoxin A (PEA) . It has recently been shown to possess superantigenic properties. PEA is an ADP-ribosyl transferase with a molecular weight of 66 kDa. The toxin has been cloned and sequenced, and the structure determined by X-ray crystallography.

A yet structurally uncharacterized superantigen has been identified in culture supernatants of another microbe, Mvcoplas a arthriditis (Yowell et al.. J.Immunol.. 131, 543 (1983) ; Cole et al.. J.Immunol. 131, 2392 (1983); Kirchner et al.. Scand. J.Immunol. 24, 245 (1986) ) . This mycoplasma-derived antigen which has been termed "MAM", shares many properties with the SEs. It is capable of inducing chronic inflammatory arthritis in rats. It has also been cultured from the bone marrow of patients with systemic lupus. It has been suggested that the MAM antigen may contribute to the polyclonal B cell activation seen in infected SLE patients. Certain viral antigens may also have superantigen properties. Minor lymphocyte stimulating (Mis) antigens are viral superantigens, so named for their ability to stimulate remarkable proliferative responses of CD4⁺ T- cells in mixed lymphocyte cultures between strains identical at the major histocompatibility complex (MHC) .

It is generally regarded that Mis antigens operate by binding simultaneously to an MHC class II molecule and the V_p TCR element, resulting in a massive proliferative response (Kappler et al.. Science 248, 705 (1990)). Alternatively, the presence of such self-superantigens in a given animal may be detected by the absence of mature T-cells bearing receptors encoded by that V^ gene segment, since the presence of an Mis antigen in a given mouse strain may result in deletion of T cells bearing the responsive V_p gene segment (Marrack et al. , J.Exp.Med. 171, 455 (1990); Sprent et al.. Science 248, 1357 (1990)) . Similar deletions of V^-responsive T-cells have also been observed in mice injected neonatally with various microbial superantigens.

Recently, a connection with endogenous retroviruses and self-superantigens has been made. Marrack et al.. Nature 349, 524-526 (1991) have described a novel self- superantigen that is transmissible in the milk of mice known to pass active mouse memory tumor virus (MMTV) from mother to offspring by this route. Mice cured of MMTV infection by foster nursing do not show clonal deletion, implying that the transmissible superantigen is encoded by this virus. These and other recent findings suggest that the Mis self-superantigens are endogenously encoded retroviral gene elements that contribute to T cell receptor repertoire development (Janeway, Nature 349, 459 (1991)).

Superantigen effects have also been associated with rheumatoid arthritis. It has been suggested that ^14- bearing T-cells are activated by a V_/3l4-specific super¬ antigen, with subsequent recruitment of a few autoreactive V_p14⁺ T-cell clones to the joints while the majority of other V^14⁺ T-cells disappear (Palliard et al. , Science 253, 325-329 (1991)).

Superantigens can be distinguished on the basis of which V_p T-cells they stimulate. For example, staphylo- coccal enterotoxin B (SEB) stimulates a wide variety of human T-cells through the V_p. TSST 1, on the other hand, stimulates only human T-cells bearing the V_p2 antigen.

Several superantigens, most notably SE, TSST-1 and MAM, stimulate T-helper cells to become active and secrete various cytokines.

3-Alkylxanthines 3,7-Dimethylxanthine, more commonly known as theobromine, is the principal alkaloid of the cocoa bean. It may be extracted therefrom by known techniques, e.g., Die Fabrikation Pharmazeutischer Und Chemisch-Techniker Produkte (Berlin, 1931) . Alternatively, theobromine may be synthesized from 3-methyluric acid according to Fischer, Arch. Ber. 31, 1980 (1898) . Theobromine has utility as a diuretic, bronchodilator and cardiotonic.

1,3-Dimethylxanthine, more commonly known as theophylline, may be synthesized from dimethylurea and ethylcyanocyanate according to known techniques, e.g.,

Traub, Ber. 33, 3035 (1900). Theophylline is useful as a bronchodilator. 1,3,7-Trimethylxanthine, known to the world as caffeine, is a central nervous system stimulant.

U.S. Patents 3,737,433 and 3,422,107 disclose certain 3-methylxanthates, namely 7-[(ω-l)-oxoalkyl]-

1,3-dimethylxanthines and 7-[ (ω-l)-oxoalkyl]-3,7- dimethyl-xanthines, useful as vasodilators. The oxoalkyl group contains from 5 to 8 carbon atoms, the keto group thereof being separated from the xanthine nucleus by at least two carbon atoms. The aforesaid compounds may be prepared from theophylline or theobromine by the methods disclosed in U.S. Patent 3,737,433 and 3,422,107, the entire disclosures of which are incorporated herein by reference.

The preparation of certain 3-alkylxanthines, having at least one tertiary hydroxyalkyl group in the

1- or 7-position, is disclosed in U.S. Patent

4,833,146, the entire disclosure of which is incorporated by reference. The compounds are disclosed as being useful for treatment of peripheral and/or cerebral irrigation disorders.

The preparation of l-5(oxohexyl)-3,7-dimethyl- xanthine, more commonly known as pentoxifylline, is described in U.S. Patents 3,737,433 and 3,422,107. Pentoxifylline has been utilized as a vasodilator, specifically for the treatment of intermittent claudication. It has also been shown to have the ability of preventing certain effects of tumor necrosis factor-α (TNF-α) on polymorphonuclear cells (Salyer, et al.. Am. J. Pathol. 136, 831-841 (1990)). TNF-α is a cytokine produced by mononuclear cells that has a wide spectrum of activity. Strieter, et al.. Bioche . Biophvs. Res. Commun. 155, 1230-1236 (1988) , report pentoxifylline-induced suppression of TNF-α production.

Other effects of pentoxifylline have been des- cribed. For example, pentoxifylline inhibits proliferation and growth of fibroblasts (Berman et al.. J. Invest. Dermatol. 92, 605-610 (1989)). Bessler et al.. Biomedicine & Pharmacotherapy 41, 439- 441 (1987) , report pentoxifylline-induced inhibition of the mitogenic response of human mononuclear cells to the plant lectins, phytohemagglutinin and concanavalin A. Rao et al. , J. Cell. Physiol.. 137, 577-582 (1988), describe inhibition of concanavalin A- induced capping of polymorphonuclear cells and mononuclear cells. Surface immunoglobulin capping of B-lymphocytes was also inhibited by pentoxifylline.

Lectin-induced mitogenib responses represent the polyclonal, non-specific transformation and prolifera¬ tion of lymphocytes. Lectins have no correlation with disease. Thus, the reports of pentoxifylline-induced suppression of mitogen responses are of no practical si .gni .fi .cance. 10

Despite the intensive research into the pharmaceutical properties of 3-alkylxanthines, the effect of these compounds in suppressing pathologically significant superantigen-induced or specific antigen-induced T- and B-cell activation, as demonstrated below, has not heretofore been known.

Summary of the Invention It is an object of the invention to provide for suppression of antigen-specific activation of T- or B- cells.

It is an object of the invention to suppress superantigen-induced activation of T-cells. It is an object of the invention to provide a method for treating pathological conditions characterized by antigen-specific or superantigen- induced activation of T- or B-cells.

It is a further object of the invention to suppress lymphokine release and/or antibody production in pathological conditions characterized by excessive immune stimulation or response to self-an igens.

It is an object to provide a method of immunosup- pression. It is a further object to provide for the preparation of a medicament for suppressing antigen- specific or superantigen-induced activation of T- or B-cells in a mammal. In particular, it is an object of the invention to provide for the preparation of a medicament for treating a pathological condition in a mammal, which condition is characterized by the activation of T- or B-cells.

These and other objects are achieved by the invention as hereinafter described. A method for suppressing antigen-specific or super-antigen-induced activation of T- or B-cells is provided. To an individual in need of such treatment, there is administered an effective amount of a compound according to the formula

wherein

R is selected from the group consisting of

O R₅

II I hydrogen, methyl , -R₃CCH₃ and -R₄CCH₃ ;

OH

R₁ is selected from the group consisting of 0 R,

I I hydrogen, methyl , -R₃CCH₃ and -R₄CCH₃ ;

OH

Rg is selected from the group consisting of C₁-C₄ straight or branched chain alkylene, preferably methyl;

R₃ is selected from the group consisting of C₂-C₆, preferably C₂-C₄, straight- or branched-chain alkylene;

R₄ is selected from the group consisting of C₂-C₆, preferably C₂-C₄, straight- or branched-chain alkylene;

R₅ is selected from the group consisting of C^C_g alkyl; or a pharmaceutically acceptable salt thereof. According to a preferred embodiment of the inven¬ tion, R and R, are selected from methyl or hydrogen, and R₂ is methyl.

According to another preferred embodiment, R is

O R₅ selected from -R₃CCH₃ and -R₄CCH₃; R, is selected from

OH hydrogen and methyl; and R_j is methyl.

Also preferred are compounds wherein Rg is methyl; _g and R₄ are selected from C₂-C₄ straight- or branched- chain alkylene, most preferably straight-chain alkylene; and R₅ is methyl.

Most preferred compounds for use in the present invention comprise the compounds wherein R is hydrogen, and R< and g are methyl (theobromine) ; R₁ is hydrogen and R and Rg are methyl (theophylline) ; R, R₁ and R_g are all methyl (caffeine) ; R₁ and Rg are methyl, and R is 0

-(CH₂)₄ ICCH₃ (pentoxifylline); R₁ is hydrogen, _g is methyl and R is

CH,

-(CH₂)₄CCH₃ (1-(5-hydroxy-5-methyl-

| hexyl)-3-methyxanthine) . OH

Brief Description of the Figures

Fig. 1 is a plot of pentoxifylline suppression of the antigen-induced (conalbumin) activation of mouse TH₂ T-cell clone D10.G4.1, at various concentrations of drug. D10.G4.1 is specific for conalbumin. Antigenic activation is determined from the extent of ³H- thymidine incorporation, which is proportional to the proliferative response of the T-cell clone.

Fig. 2 is a plot of caffeine suppression of the same antigen-induced response of Fig. 1. Fig. 3 is a plot of pentoxifylline suppression of the superantigen-induced (staphylococcal enterotoxin B (SEB)) activation of clone D10.G4.1, at various concentrations of drug.

Fig. 4 is a plot of caffeine suppression of the same superantigen-induced response of Fig. 3.

Fig. 5 is a plot of theophylline suppression of the same antigen-induced response of Fig. 1. Fig. 6 is a plot of theobromine suppression of the same antigen-induced response of Fig. 1.

Fig. 7 is a plot of theophylline suppression of the same superantigen-induced response of Fig. 3. Fig. 8 is a plot of theobromine suppression of the same superantigen-induced response of Fig. 3.

Fig. 9 is a plot of pentoxifylline and caffeine suppression of the antigen-induced (pigeon cytochrome

C (PCC)) activation of mouse TH, T-cell clone A.E7, at various concentrations of drug. Clone A.E7 is a T- cell clone specific for PCC. Antigenic activation was determined from the extent of ³H-thymidine incorporation, which is proportional to the prolifera¬ tive response of the T-cell clone. Fig. 10 is a plot of pentoxifylline and caffeine suppression of the superantigen-induced (SEB) activation of clone A.E7, at various concentrations of drug.

Fig. 11 is a plot of pentoxifylline suppression of the antigen-induced activation of immune mouse splenocytes from a mouse previously immunized with sheep red blood cells. Antigenic activation, as a function of antibody production, was determined by a hemolytic plaque assay. Fig. 12 is a plot of caffeine suppression of the antigen-induced activation of immune mouse splenocytes, similar to Fig. 11.

Fig. 13 is a plot of theophylline suppression and theobromine suppression of the antigen-induced activation of immune mouse splenocytes, similar to Fig. 11.

Fig. 14 is a plot of pentoxifylline suppression of the antigen-induced activation of immune mouse splenocytes, similar to Fig. 11, except that in the lanes marked "Pretreat Pentoxifylline", the immune splenocytes were pretreated with drug in advance of, rather than during, the hemolytic plaque assay.

Fig. 15 is a plot of l-(5-hydroxy-5-methylhexyl)- 3-methylxanthine (HMX) suppression of antigen-induced activation of immune mouse splenocytes, similar to the plot in Fig. 14.

Fig. 16 is a plot of suppression of the super- antigen-induced minor lymphocyte-stimulating l^a (Mls- l^a) response of mouse lymphocytes treated with pentoxifylline, caffeine and theophylline.

Fig. 17 is a plot of suppression of the super¬ antigen-induced minor lymphocyte-stimulating 2^a (Mls- 2^a) response of mouse lymphocytes treated with pentoxifylline, caffeine and theophylline.

Fig. 18 is a plot of pentoxifyllene and caffeine suppression of the antigen-induced (conalbumin) activation of the TH₂ T-cell clone D10.G4.1, at various drug concentrations. The clone releases the lym¬ phokines interleukin-4 (IL-4) and interleukin-5 (IL- 5) . Antigenic activation was determined from the extent of IL-4 release, which is proportional to the proliferative response of target IL-2/IL-4-dependent cells (CTLL-2) incubated with the T-cell clone culture supernatant.

Fig. 19 is a plot of the pentoxifylline and caf¬ feine suppression of the superantigen-induced (SEB) activation of clone D10.G4.1 at various concentrations of drug.

Fig. 20 is a plot of pentoxifyllene and caffeine suppression of the an igen-induced (PCC) activation of the TH, T-cell clone A.E7, at various drug concentrations. Clone A.E7 releases the lympokines interleukin-2 (IL-2) and γ-interferon. As in Fig. 18, antigenic activation was determined by the extent of interleukin (here IL-2) release, which is proportional to the proliferative response of IL-2/IL-4-dependent target cells (CTLL-2) incubated with the T-cell clone culture supernatant.

Fig. 21 is a plot of the pentoxifylline and caf¬ feine suppression of the superantigen-induced (SEB) activation of clone A.E7 at various concentrations of drug.

Fig. 22 is a plot of the pentoxifylline and caf¬ feine suppression of the antigen-induced (tetanus toxin) activation of human peripheral blood leukocytes (PBLs) , at various concentrations of drug. Antigenic activation was determined from the extent of ³H- thymidine incorporation, which is proportional to the proliferative response of the cultured PBL populations. Fig. 23 is a plot of the pentoxifylline and caf¬ feine suppression of the superantigen-induced (SEB) activation of human PBLs, at various concentrations of drug. Antigenic activation was determined from the extent of ³H-thymidine incorporation. Fig. 24 is a plot of the effect of pentoxifylline and caffeine on the proliferative response of human PBLs to the plant lectin, phytohemagglotinin. Proliferation was determined by the extent of ³H- thymidine incorporation. Fig. 25 is a plot of the effect of pentoxifylline on the proliferation of the T-cell hybridoma BDK 23.1 in response to specific antigen (keyhole limpet hemocyanin) , at various concentrations of drug.

Fig. 26 is a plot of the effect of pentoxifylline on the antigen-induced (keyhole limpet hemocyanin) activation of hybridoma BDK 23.1, at various concentrations of drug. Antigenic activation was determined from the extent of IL-2 release which is proportional to the proliferative response of CTLL-2 target cells.

Fig. 27 is a schematic representation of the steps in the immune response following challenge by a specific antigen. Antigen is processed and bound to MHC-II molecules on accessory (ACC) cells. Presentation of processed antigen to the TCR complex of CD4⁺ T-helper (T_H) cells results in the production of various interleukins and γ-interferon, which facilitate the activation and differentiation of antigen-specific B cells into antibody producing plasma cells (P_L) .

Fig. 28 is a schematic representation of the steps in the superantigen-triggered immune response. Fig. 29 is a schematic representation of the polyclonal response elicited by the prototypical mitogens, the lectins. Antigen binds non-specifically to sugar moieties, causing activation of accessing cells, T-helper cells and B-cells by multiple pathways in a widespread polyclonal response.

Detailed Description of the Invention We have found that 3-alkylxanthines have a profound effect in suppressing antigen-specific activation of T-cells and B-cells, and in suppressing superantigen-induced activation of T-cells. As such, the 3-alkylxanthines are believed useful as immunosuppressive agents. This novel activity is distinct from, and unrelated to, suppression of the lectin-induced T-cell proliferative response.

By "activation" of B- or T-cells is meant the transformation of such cells from a resting to an active state, characterized by the occurrence of one or more of the following: lymphokine receptor expression and cytokine release, proliferation, differentiation, and/or antibody production. Typically, upon encountering antigen bound^' to accessory cells, first T-cells, and subsequently B- cells, proceed to enlarge, initiate DNA synthesis, proliferate and differentiate into effector cells. The triggering of these events is characteristic of B- or T-cell activation. For the most part, lymphokine release is considered the hallmark of cell activation and a stringent requirement for cellular mitogenesis. By "antigen-specific activation" is meant activa¬ tion in a protein-specific immune response, as opposed to the general (nonspecific) polyclonal transformation of lymphocytes which is characteristic of lectin or mitogen stimulation. The cells involved in antigen- specific activation are generally clonal and of limited specificity.

By "superantigen" is meant an antigen, other than a mitogen, which elicits a T-cell receptor (TCR)- specific immune response, depending on the expression of a particular V_β gene segment within the TCR complex. The cells involved in the superantigen-induced response are considered clonal in that only cells having particular V^ elements are activated.

The 3-alkylxanthines suppress T-cell and B-cell activation. Specifically, they suppress specific antigen-induced activation of both B- and T-cells, and superantigen activation of T-cells. The 3- alkylxanthines are therefore believed useful in treating conditions characterized by overt lymphocyte activation. The 3-alkylxanthines may be administered to suppress antigen-induced or superantigen-induced T- or B-cell activation according to the present inven- tion by any of the various administration routes and formulations previously utilized for the prior indications of such compounds. Thus, the 3- alkylxanthines may be applied in combination with a carrier, excipient or a solvent and administered in any desired manner. They may be dissolved or applied in a pharmaceutically compatible vehicle such as saline solution, for intravenous injection. Further additives may be required to increase solubility for injection. For example, it is known to dissolve theophylline in water with ethylene diamine as a solublizer.

The compounds may also be administered orally, in solid or solution form, in controlled or non- controlled release form. Specialized delivery systems for oral administration of alkylxanthines may be utilized. U.S. Patent 4,189,469, for example, discloses an admixture of certain methylxanthine compounds and saliva-forming agents to reduce gastro- intestinal incompatibility.

Some of the 3-alkylxanthines are known to form pharmaceutically acceptable salts. For example, theobromine and theophylline may be administered as the sodium salt thereof. Thus, the present invention contemplates not only the administration of the 3- alkylxanthines per se for immunosuppressive treatment, but also pharmaceutically acceptable salt forms thereof. The 3-alkylxanthines may be administered accord¬ ing to the practice of the invention to suppress activation of B- or T-cells in any amount effective to achieve such results. The extent of such immunosuppression induced may be adjusted by manipulating the dosage of compound. This is so since, as hereinafter shown, the immunosuppressive effect is dose-dependent. The actual dosage administered may take into account the size and weight of the patient, whether the nature of the treatment is prophylactic or therapeutic in nature, the age, weight, and health and sex of the patient, the route of administration, and other factors. Those skilled in the art should be readily able to determine suitable dosages and schedules of administration to suit the specific circumstance. A suitable daily dosage may range from about 0.01 to about 5 gram per day for oral administration, and a lower dosage, about 0.01 to about 0.5 gram per day for intravenous administration. Greater or lesser amounts of active agent may be administered, as required.

The 3-alkylxanthines may be administered according to the practice of the present invention in circumstances where suppression of specific antigen- induced activation of B- and/or T-cells, or superantigen-induced activation of T-cells, is desired. In particular, it is contemplated that the 3-alkylxanthines would be administered to forestall undesired or exuberant immune responsiveness to self- or nonself-antigens. The 3-alkylxanthines may be administered to treat pathological effects of any of the superantigen-implicated disease states mentioned above. The progress of those disease states is believed to involve the superantigen-induced activation of T-cells. Hence, the 3-alkylxanthines, through their ability to inhibit superantigen-induced activation of T-cells, are believed useful for treating disease states variously attributable to superantigen agents, such as streptococcal and staphylococcal proteins, and other microbial-derived superantigens. Those disorders include, for example, SE-mediated conditions such as food poisoning; streptoccocal protein-mediated conditions such as toxic shock syndrome; SMP-mediated conditions such as rheumatic fever and rheumatic heart disease; Pseudominas aeruqinosa infection; viral infection; and any other disease conditions or inflammatory syndromes characteristic of excessive or prolonged T-cell activation harmful to the host.

Since T-and B-cells are presumed to play a role in the etiology of autoimmune disease, suppression of their activation is a basis for treatment for autoimmune disorders. Thus, the 3-alkylxanthines may be utilized as general immunosuppressants, for the treatment of such disorders, and for preventing graft rejection or graft versus host disease.

Inflammatory diseases are caused by activation of the immune system in response to specific antigen expression by pathogens, or by superantigen pathogens. Such inflammatory disorders include, for example, TSS and pelvic inflammatory disease. The 3-alkylxanthines are believed useful in treating inflammatory disorders. Suppression of antigen-specific T-cell activation according to the process of the present invention is illustrated in Examples 1 through 6 below. T-cells responsive to specific antigen (conalbumin, pigeon cytochrome C or keyhole limpet hemocyanin) were cultured in the presence of varying concentrations of drug and appropriate antigen-presenting accessory cells loaded with antigen (ACCs) . Drug inhibition of T-cell activation was observed by a decrease in proliferation or lymphokine release.

Example 1

Suppression of Antigen-Specific and Superantigen-induced T-cell Activation As Indicated by Proliferation Assay.

T-cell clones. The TH, clone, A.E7 (Hecht et al..

J. Immunol. 131, 1049 (1983) is specific for pigeon cytochrome C (PCC) in the context of I-E^k, and bears the V_β3 T cell receptor allele. The TH₂ clone D10.G4.1 (ATCC TIB 224; Kaye et al.. J. Exp. Med. 158, 836 (1983)) is specific for conalbumin in the context of I-E^k. It is also alloreactive to I-A^b molecules. D10.G4.1 bears the V^ 8.2 allele. The aforementioned T-cell clones were grown in a clone medium (CM) composed of RPMI 1640, supplemented with 0.1 mM nonessential amino acids, 1 mM sodium pyruvate, 2 mM L-glutamine, 10% fetal calf serum (FCS) , 0.05 mM 2 mercaptoethanol, and 50 μg/ml gentomycin.

Preparation of antigen-presenting cells. Antigen-presenting accessory cells (ACC) , comprising spleen cells genetically matched to the T-cell clone, were prepared as follows. Single cell suspensions were prepared from the spleens of C3H/HeJ mice in RPMI 1640. Erythrocytes were lysed with 0.17 M NH₄C1, and the remaining cells were irradiated using 2000 rad of X-irradiation. The irradiated splenocyte suspension was then treated with monoclonal anti-Thy-1 (jlJ) and anti-CD3 antibodies followed by 1:1 dilution in baby rabbit complement (LOW TOX-M, Cedarlane Laboratories, Cedarlane, PA) , essentially as described previously by Kaye et al. , supra. The predominant population of ACC are B cells and macrophages which together comprise greater than 95% MHC class II-bearing cells. Superantigen- or antigen-pulsed ACC were then prepared from the T-cell-depleted population by incubation with 1 μg/ml superantigen (SEB, Sigma Chem. Co., St. Louis, MO) or 100 μg/ml antigen (PCC or conalbumin, both from Sigma) respectively, for 45 min. at 37°C in 5% C0₂. These cells were then washed extensively with medium to remove unbound superantigen or antigen.

Superantigen- and antigen-specific proliferation of T-cell clones. 2 x 10⁴ T-cells were cultured with 5 x 10⁵ superantigen- or antigen-pulsed accessory cells per ml in the presence or absence of various concentrations of drug (pentoxifylline, caffeine, theobromine or theophylline) in a final volume of 0.2 ml at 37°C in 5% C0₂. Cells were pulsed with 1 μCi of ³H-thymidine per well after 48 hours in culture, and harvested 18 hours later. The level of radiolabel incorporation was determined by liquid scintillation counting. The results are indicated in Figures 1-10.

Figures 1 and 2 (conalbumin-activated D10.G4.1 T- effector cells) indicate that pentoxifylline and caffeine significantly inhibit antigen-specific activation of T-cells, in comparison to the untreated controls. Inhibition of T-cell activation was signaled by a suppression of cell proliferation. Pentoxifylline and caffeine similarly inhibited superantigen (SEB) activation of the same TH₂ T-cell clone. See Figures 3 and 4 respectively.

Theophylline exerted an inhibitory effect on both antigen (conalbumin, Fig. 5) and superantigen (SEB, Fig.7) activation. Inhibition was similarly obtained with theobromine. See Fig. 6 (conalbumin activation) and Fig. 8 (SEB activation) .

The effect of the 3-alkylxanthines on antigen- specific and superantigen-induced activation of the TH, T-cell line A.E7 is shown in Figures 9-10. Both pentoxifylline and caffeine inhibited antigen-specific (PCC) activation of the TH, clone as well as superantigen (SEB) activation.

TH, clones such as A.E7 synthesize both IL-2 and IFN-γ. These lymphokines are not detectably expressed in TH₂ T-cell clones, such as D10.G4.1. TH₂ T-cell clones synthesize detectable amounts of IL-4, IL-5 and probably IL-6, but not IL-2 or IFN-γ Thus, the level of T-cell activation in response to antigen-specific or superantigen-induced stimulation may be assayed by measuring lymphokine production by such IL-2-producing and IL-2-dependent cells.

According to Example 2, below, drug-induced sup- pression of D10.G4.1 and A.E7 activation was determined by such an indirect assay which measures the proliferative response of an IL-2/IL-4 dependent cell line (CTLL-2 (ATCC TIB 214)). Briefly, a T-cell clone responsive to a specific antigen (conalbumin or PCC) , or responsive to superantigen (SEB) , was cultured in the presence of the IL-2/IL-4-dependent line CTLL-2, varying concentrations of drug, and ap¬ propriate antigen-presenting cells loaded with antigen. Drug inhibition of T-cell activation was observed as the suppression of IL-2 or IL-4 release from the T-cell clones, which was assayed as the suppression of IL-2- or IL-4-driven CTLL-2 proli¬ feration, compared to CTLL-2 proliferation in control cultures containing no drug.

Example 2

Suppression of Antigen-Specific and Superantigen-induced T-cell Activation, As Indicated by Lymphokine Release Assay.

Using the same protocol used in Example 1, T-cell clones (2 x 10⁴ T-cells) were cultured with 5 x 10⁵ superantigen- or antigen-pulsed ACC per ml in the presence or absence of various concentrations of drug (pentoxifylline, caffeine, theobromine or theophyl¬ line) in a final volume of 0.2 ml at 37°C in 5% C0₂. After 24 hours, 100 μl of cell-free supernatant were placed into a 96-well plate containing 1 x 10⁴ CTLL-2 cells (ATCC TIB 214) . The supernatant/CTLL-2 mixture was then incubated 18 hrs, after which the cultures were pulsed with ³H-thymidine for 4-6 hrs at 37°C. The pulsed CTLL-2 cells were then harvested and read on a liquid scintillation counter. The results represent triplicate cultures of a given drug and/or antigen concentration cultured with CTLL-2 cells (±SD) . The data is shown in Figs. 18 through 21.

Lymphokine production, which is the benchmark indicia of T-cell activation, was suppressed by the 3- alkylxanthines. Figure 18 (conalbumin-activated D10.G4.1 T-effector cells) indicates that pentoxifylline and caffeine significantly inhibited (IL-4) lymphokine production in response to specific antigen. Pentoxifylline and caffeine similarly suppressed IL-4 production in response to superantigen (SEB) activation of the same TH₂ T-cell clone. See Fig. 19.

Pentoxifylline and caffeine also inhibited lym- phokine (IL-2) release of the TH, clone A.E7 in response to stimulation by its antigen (PCC, Fig. 20) , and by superantigen (SEB, Fig. 21) .

The ability of 3-alkylxanthines to inhibit antigen-specific activation of T-cells was further demonstrated by Examples 3 and 4, using the T-cell hybridoma BDK 23.1, which is specific for keyhole limpet hemocyanin (KLH) in the context of I-A^d. The hybridoma was cultured with varying concentrations of drug and assayed for proliferation (Example 3) and IL- 2 production (Example 4) .

Example 3

Suppression of Antigen-Specific T-cell Hybridoma Activation As Indicated by Proliferation Assay.

APCs were prepared as in Example 1 from BALB/c splenocytes bearing the appropriate molecules for presenting the antigen, KLH, to the KLH-specific T- cell hybridoma BDK 23.1 (from Dr. John Kappler, National Jewish Hosp., Denver, CO). The splenocytes were treated with complement and monoclonal antibody as in Example 1. Then, 2 x 10⁴ cell hybridomas were cultured with 5 x 10⁶ T-cell-depleted ACC and KLH in the presence or absence of drug (pentoxyfillyne) and incubated for 48 hrs. The cells were then cultured with ³H-thymidine for an additional 18 hrs. at 37°C.

The pulsed hybridoma cells were harvested and read in a liquid scintillation counter. The results, graphed in Fig. 25, represent triplicate cultures.

Example 4

Suppression of Antigen-Specific T-cell Hybridoma Activation As Indicated by Lymphokine Release Assay

2 x 10⁴ BDK 23.1 cells were cultured with 5 x 10⁶ T-cell-depleted ACC and KLH in the presence or absence of pentoxyfylline as in Example 3, and incubated for 24 hours at 37°C. After this incubation, 100 μl of supernatant from each of the cultures were transferred into another 96-well plate containing 1 x 10⁴ CTLL-2 cells for IL-assay. The supernatant/CTLL-2 mixtures were then incubated 18 hrs., after which the cultures were pulsed with ³H-thymidine for 4-6 hrs at 37^βC. The pulsed CTLL-2 cells were then harvested and read on a liquid scintillation counter. The results, graphed in Figures 25 and 26, represent triplicate cultures of pentoxifylline and/or antigen concentration cultured with CTLL-2 cells (±SD) .

As indicated in Figure 25, antigen-induced (KLH) proliferation of the T-cell hybridoma was markedly suppressed by pentoxifylline at a concentration as low as 50 μg/ml, indicating that the drug possesses potent antiproliferative activity. Similarly, the results of the IL-2 assay (Fig. 26) indicate that pentoxifylline suppresses another indicia of T-cell activation, namely IL-2 production, at a concentration as low as 1 μg/ml. Typical immunosuppressants such as mitomycin C, X-rays and γ-irradiation inhibit T-cell hybridoma proliferation, without affecting the cell's ability to express surface receptors or produce lymphokines. By contrast, the 3-alkylxanthines suppress both proliferation and lymphokine production, indicating that these drugs have multiple effects on cellular activation.

The ability of the 3-alkylxanthines to inhibit T- cell activation by a viral superantigen is illustrated in Example 5. Pentoxifylline, caffeine and theobromine suppressed CD4⁺ T-cell activation by minor lymphocyte stimulating (Mis) antigens.

Example 5

Suppression of Mis Response Mis response assays were set up as previously described by Webb et al. , Cell 63, 1249 (1990). Responder lymphocyte populations, i.e., mouse lymphocytes sensitive to activation by Mis viral superantigen (mouse strains C3B6F1 and C57BL/6) , were enriched for T-cells by passage of lymphnode and splenic cells over a nylon wool column. 3 x 10⁵ T- cells were cultured with 5 x 10⁶ mytomycin C-treated spleen stimulator cells (CBA/J and BALB.B) depleted of T-cells by treatment with an •ti-CD3 monoclonal antibody and complement as described in Example 1. C57BL/6, which lack any Mis antigens, were also used as stimulator cells in control experiments (Fig. 16: C57BL/6 → C3B6F1; Fig. 17: C57BL/6 → C57BL/6) . The CBA/J and BALB.B stimulator cells bear Mis antigens on their surface, and are therefore capable of stimulating activation of the responder populations. Mls-l^a and Mls-2^a responses were induced in the presence or absence of varying concentrations of pentoxifylline, caffeine or theophylline. After approximately 72 hours incubation, cultures were pulsed with 1 μCI/well of ³H-thymidine for 12 hours before harvesting onto fiber-filter mats. The cultures were then counted in a scintillation counter. The results are set forth in Fig. 16 (Mls-l^a response) and Fig. 17 (Mls-2^a response) . According to these Figures, all three alkylxanthines tested, i.e., pen- toxifylline, caffeine and theophylline, inhibited the

Mis superantigen activation of responder T-cells in a dose-dependent fashion.

The ability of the 3-alkylxanthines to inhibit antigen-specific activation of human T-cells is illustrated by Example 6, demonstrating inhibition of tetanus toxin activation of human peripheral blood lymphocytes.

Example 6

Suppression of Tetanus Toxin-induced Human Peripheral Blood Lymphocyte Activation.

Peripheral blood was obtained by venipuncture from healthy human donors who were 25 to 30 years old. Human peripheral blood leukocytes (PBLs) were isolated by centrifugation through a Ficoll-Hypaque gradient. Triplicate cultures of 2 x 10⁵ PBL were incubated with 2 μg/ml tetanus toxin (TT) or superantigen (SEB) in the presence or absence of various concentrations of pentoxyfylline or caffeine in a final volume of 0.2 ml RPMI 1640 supplemented with 10% fetal calf serum (FCS) , 1 mM non-essential amino acids, lmM sodium pyruvate, 2 mM glutamine, 0.05 mM 2-mercaptoethanol, and 50 μg/ml gentamycin at 37°C in 5% C0₂. Cultures were pulsed with 2μCi of ³H-thymidine per well after 96 hours and harvested 18 hours later. The amount of radiolabel incorporated was determined by liquid scintillation counting. The results are indicated in Figure 22 (tetanus toxin-induced activation) and Fig. 23 (SEB-induced activation) . Pentoxifylline and caffeine inhibited activation of human T-cells in a dose-dependent fashion at concentrations of drug as low as 25 μg/ml. By contrast, when the same assay was repeated utilizing the plant lectin phytohemagglutinin as the proliferation-inducing agent, a drug concentration of 100 μg/ml was required to inhibit T- cell proliferation (Fig. 24) . 3-Alkylxanthine suppression of B-cell activation is demonstrated in Example 7 according to a typical haemolytic plaque assay. Splenocytes obtained from mice immunized against sheep red blood cells (SRBC) were cultured with SRBC in the presence or absence of varying concentrations of drug. The number of plaque- forming cells was compared to non-treated control groups. In some experiments, in lieu of adding drug to the active culture, B-cells were pretreated with drug in an effort to determine whether or not suppression of antibody production requires the continuous presence of the drug in the culture. The results, discussed below, indicate that continuous presence of drug is not required.

Example 7 Suppression of B-cell Activation

Animals. All mice used in these studies were male BALB/cByJ or BALB/cAnSkh mice between the ages of 6 and 12 weeks.

Splenocyte Preparation. Spleens from immunized (0.2 ml of 10% solution of sheep red blood cells (SRBC) [Rockland Laboratories, Inc. , Gilbertsville, PA] in saline i.p., 2 wk prior to sacrifice) mice were removed aseptically and teased with tweezers to remove connective tissue in holding medium (HM) consisting of AUTO-POW MEM (Flow Laboratories, McLean, VA) , 5% fetal calf serum (FCS) (Flow Laboratories) , and 25 μg/ml gentamicin. A single-cell suspension was made by repeatedly expelling the spleen preparation through a 20-gauge needle. The single-cell suspension was then washed twice with HM.

Mishell-Dutton cultures. Antibody-forming cells were generated in vitro in micro-Mishell-Dutton cultures (Tittle et aJL. , Cell. Immunol. 35, 180 (1978), as modified previously (Donnelly et al. , Cell. Immunol. 72, 166 (1982)). Cells were cultured in flat-bottomed 96-well microtiter plates in which each well received a total of 1 x 10⁶ cells in 50 μl of tissue culture medium (TCM) . Each well culture represented a row of eight wells, and cells were pooled accordingly at the time of the plaque assay.

Twenty-four hours after initiation of the cultures, the cells were fed 50 μl of a nutritional cocktail consisting of 2x non-essential amino acids, 5.5 mg/ml dextrose, 2 mM L-glutamine, 0.63% NaHC0₃, 33% FCS and 41 μg/ml each of adenosine, guanosine, cytosine, and uridine. After 5-days in culture, the cells are harvested and tested for antibody production using a hemolytic plaque assay.

In drug experiments, cells were cultured in 96- well microculture plates at a density of 2 x 10⁷ cells/ml together with either a 0.1% suspension of SRBC and dilutions of drug-containing medium suspended at various concentrations. Unless otherwise noted, the drugs were added on day 0 of a 5-day response. In designated experiments, immune splenocytes were pretreated with various concentrations of drug for 2 hours at 37"C. The cells were then extensively washed and placed back into culture with SRBC. Cultures were incubated in an atmosphere consisting of 10% C0₂, 7% 0₂, and 83% N₂ and cocktailed after an initial 24 hours incubation.

Detection of Primary and Secondary In Vitro An¬ tibody Responses. The anti-SRBC plaque forming cell (PFC) responses in Mishell-Dutton cultures were determined by a hemolytic plaque assay (Kappler, J. Immunol. 112, 127 (1974)) using the Cunningham modification (Cunningham and Szenberg, Immunol. 14, 599 (1968)). Accordingly, Cunningham chambers were constructed using precleaned microscopic slides and double-sided tape. 20 to 30 slides were placed in a row and connected at both ends with strips of double- sided tape. An additional strip was placed down the center of the taped slides. Clean slides were then placed on top of the taped slides in such a way that a microchamber was formed between the two slides. Mild pressure was used to permanently seal the taped edges and centers of the slides. The capacity of the chamber was approximately 150 to 165 μl. Slides were then numbered and separated from each other by flexing adjacent slides to break the tape.

Lymphoid cells harvested from Mishell-Dutton cultures were washed twice in Modified Eagle's Medium (MEM) and were subsequently suspended in 1 ml of MEM for the PFC response. The cell suspensions were maintained on ice until the number of PFC were assessed. A source of indicator cells such as SRBC was prepared by washing the SRBC three times with MEM and a final wash with IX stock of modified barbital buffer (MBB) . Packed SRBC were then suspended to a final concentration of 33% in MBB. A complement mixture was also prepared by diluting 1 ml of guinea pig serum (Rockland Laboratories) with 0.5 ml of MEM prior to use in the assay. In the plaque assay, lOOμl of lymphoid cells were mixed with 25 μl of MEM, 25 μl of indicator cells, and 20 μl of diluted complement. The entire suspension of 165 μl was then placed into a Cunningham chamber which was sealed with a mixture of hot vaseline and paraffin. The chambers were incubated at 37°C for 30 to 45 minutes in a C0₂ incubator. A plaque or zone of red cell lysis in a chamber represented a single IgM antibody-producing cell. Plaques were enumerated and the total number of antibody producing cells per culture was calculated. The hemolytic plaques were quite visible to the naked eye, but were counted under a Bristoline dissecting microscope. Cell suspension was adjusted to a con¬ centration that provides 75 to 100 PFC/chamber, since it is difficult to count more than 150 PFC/chamber. Triplicate determinations of the PFC responses were performed for each culture and the mean value per culture was determined as described previously (Donnelly et al. , supra) . Results were expressed as

PFC per culture and include standard error of the mean for each group.

Tha results of the plaque assay are shown in Figures 11-15. Antibody production was suppressed in a dose-dependent fashion by pentoxifylline (Fig. 11) , caffeine (Fig. 12), theophylline (Fig. 13) and l-(5- hydroxy-5-methylhexyl)-3-methylxanthine ("HMX") (Fig.

15) . (The preparation of the last-mentioned drug is described in Example 6 of U.S. Patent 4,833,146). Drug pretreatment of antibody-producing cells before incubation with SRBCs in lieu of drug inclusion in the splenocyte/SRBC co-culture, also inhibited antibody production. See Fig. 14 ("Pretreat PTX" 100 μg/ml and 50 μg/ml) and Fig. 15 ("Preatreat HMX" 100 μg/ml and 50 μg/ml) .

All references cited with respect to synthetic, preparative and analytical procedures are incorporated herein by reference. The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.

Claims

CLAIMSWe claim:

1. Use of a compound according to the formula

wherein R is selected from the group consisting of hydro¬ gen, methyl,

O R_ς

-R_gCCH₃ and -R₄CCH₃; OH R, is selected from the group consisting of hydro- O R₅

II I gen, methyl, - _gCCH_g and -R₄CCH₃

OH

R_g is selected from the group consisting of C,-C₄ straight- or branched-chain alkylene;

R_g is selected from the group consisting of C₂-C₆ straight- or branched-chain alkylene; R₄ is selected from the group consisting of C₂-C₆ straight- or branched-chain alkylene;

R₅ is selected from the group consisting of C,-C₃ alkyl; or a pharmaceutically acceptable salt thereof; for the preparation of a medicament for suppressing antigen-specific or superantigen-induced activation of

T- or B-cells in an individual in need of such treatment.

2. Use of a compound according to claim 1 wherein R_g is methyl.

3. Use of a compound according to claim 2 wherein R and R, are independently selected from the group consisting of methyl and hydrogen.

4. Use of a compound according to claim 3 wherein R is methyl and R, is hydrogen.

5. Use of a compound according to claim 3 wherein R and R, are each methyl.

6. Use of a compound according to claim 3 wherein R is hydrogen and R, is methyl.

7. Use of a compound according to claim 2 wherein R is selected from the group consisting of 0 R₅

II I

-R₃CCH₃ and -R₄CCH₃, and R, is selected from hydrogen and

OH methyl, wherein Rg and R₄ are selected from C₂-C₄ straight-or branched-chain alkylene, and R₅ is selected from the group consisting of C,-C₃ alkyl.

8. Use of a compound according to claim 7 wherein Rg and R₄ are selected from C₂-C₄ straight- or branched-chain alkylene, and R₅ is methyl.

9. Use of a compound according to claim 7 wherein R is

0

-(CH2)₄C IICH₃ and R, is methyl.

10. Use of a compound according to claim 1 for suppressing superantigen-induced activation of T- or B-cells.

11. Use of a compound according to the formula:

R₂ wherein

R is selected from the group consisting of hydro- gen, methyl,

0 R₅

II I

-R_gCCH_g and -R₄CCH₃; OH

R, is selected from the group consisting of hydro-

O R₅ » I gen, methyl , -R_gCCH₃ and -R₄CCH₃

OH _g is selected from the group consisting of C,-C₄ straight- or branched-chain alkylene;

R_g is selected from the group consisting of C₂-C₆ straight- or branched-chain alkylene;

R₄ is selected from the group consisting of C₂-C₆ straight- or branched-chain alkylene;

R₅ is selected from the group consisting of C,-C₃ alkyl; or a pharmaceutically acceptable salt thereof; for the preparation of a medicament for treating a pethological condition characterized by activation of T- or B-cells.

12. Use of a compound according to claim 11 for treating a superantigen-mediated pathological condition.

13. Use of a compound according to claim 12 when the superantigen comprises a bacterial superantigen.

14. Use of a compound according to claim 12 wherein the superantigen comprises a viral superantigen.

15. Use of a compound according to claim 13 wherein the superantigen comprises staphylococcal protein.

16. Use of a compound according to claim 13 wherein the superantigen comprises a streptococcal protein.

17. Use of a compound according to claim 13 wherein the superantigen comprises Pseudomonas aeroginosa exotoxin A.

18. Use of a compound according to claim 11 wherein Rg is methyl.

19. Use of a compound according to claim 18 wherein R and R, are independently selected from the group consisting of methyl and hydrogen.

20. Use of a compound according to claim 19 wherein R is methyl and R, is hydrogen.

21. Use of a compound according to claim 20 wherein R and R, are each methyl.

22. Use of a compound according to claim 19 wherein R is hydrogen and R, is methyl.

23. Use of a compound according to claim 18 wherein R is selected from the group consisting of 0 R= » V

-R_gCCH_g and -R₄CCH₃, and R, is selected from hydrogen and

OH methyl, wherein g and R₄ are selected from C₂-C₄ straight-or branched-chain alkylene, and R₅ is selected from the group consisting of C,-C₃ alkyl.

24. Use of a compound according to claim 23 wherein R_g and R₄ are selected from C₂-C₄ straight- or branched-chain alkylene, and R₅ is methyl.

25. Use of a compound according to claim 23 wherein R is

0

-(CH2)₄C IICH₃ and R, is methyl.