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Manipulation of Autoantibody Idiotypes in Autoimmune Diseases
©1997 Elsevier Science B.V. All rights reserved. Idiotypes in Medicine: Autoimmunity, Infection and Cancer Y. Shoenfeld, R.C. Kennedy and S. Ferrone, editors.
MANIPULATION OF AUTOANTIBODY IDIOTYPES IN AUTOIMMUNE DISEASES Dan Buskila, Mahmoud Abu-Shakra and Yehuda Shoenfeld Rheumatic Disease Unit, Soroka Medical Center and Ben-Gurion University, Beer Sheva, and Research Unit of Autoimmune Diseases, Department of Medicine "B ", Sheba Medical Center, Tel-Hashomer, and Sackler Faculty of Medicine, Tel-Aviv University, Israel The idiotypic network is an important mechanism for controlling the immune repertoire (Jeme, 1974; Paul et al., 1990; Buskila and Shoenfeld, 1992), and autoimmune diseases may be attributed to the disturbance of the network (Zanetti, 1985; Burdette and Schwarts, 1987). Thus, one may speculate that manipulation of idiotypes (pathogenic, cross-reactive) of autoantibodies (anti-Id immunity) may be effective in the treatment of autoimmune diseases. Indeed, there are encouraging reports coming from another field of medicine, which is using anti-idiotypic (anti-Id) antibodies in the treatment of B-cell tumors (Miller et al., 1982; 1989; Brown et al., 1989). In this novel approach to treating B-cell lymphomas and leukemias, anti-Id antibodies have as their target a tumor-specific antigen, the idiotype of the cell surface immunoglobulin present on B cells.
Table 1. Methods by which Autoantibody Idiotypes Might be Manipulated • Injection of anti-Id: Anti-Id directly regulates autoantibodies. • Direct injection of a common Id: Formation of anti-Id down regulates autoantibodies. • Injection of anti-Id conjugated to a cytotoxic agent: a) Anti-Id targets Ab-producing cells b) Toxin specifically destroys them • Passage of plasma over an anti-Id column: Removal of Ab bearing the common Id. • Treatment with poly specific immunoglobulins (IVIG): Anti-Id suppression of autoantibodies mediated by anti-Ids present in IVIG. Treatment with Id-specific T cells.
These results prompted in part the studies and research towards a similar treatment modality in autoimmune diseases. Thus successful in vitro and in vivo manipulations of autoantibody production by antiId antibodies were described in several animal models of autoimmunity (Hahn and Ebling, 1984; Zanetti et al., 1984; Aguis and Richmann, 1986; Koazky and Mirshahi, 1990; Roubaty et al., 1990; Nordling et al., 1991; Zou and Whitaker, 1993; Blank et al., 1994). In this chapter, we will review the idiotype-based approaches that have recently been initiated as potential interventions in autoimmune disease progression and remission.
ANTI-Id MODULATION OF AUTOANTIBODIES The possible methods by which the idiotype network might be manipulated are summarized in Table 1 and in the following sections of this chapter. Included are in vitro studies using peripheral blood lymphocytes from animal models of autoimmunity and human patients with autoimmune diseases, as well as in vivo studies in different autoimmune animals (Table 2) (Hahn and Ebling, 1984; Zanetti et al., 1984; Aguis and Richmann, 1986; Koazky and Mirshahi, 1990; Roubaty et al., 1990; Nordling et al., 1991; Zhou and Whitaker, 1993; Blank et al., 1994). In Vitro Anti-Id Modulation of Autoantibodies In vitro studies demonstrating modulation by anti-Id support the theory that anti-Id may modulate autoantibody activity in vivo.
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Table 2. Animal Models of Autoimmunity Treated by Manipulation of Autoantibody Idiotypes with Anti-Id Antibodies Reference Experimental systemic lupus erythematosus Murine lupus and lupus nephritis Autoimmune tubulointerstitial nephritis Collagen arthritis Experimental autoimmune myastenia gravis Autoimmune uveoretinitis Autoimmune thyroiditis Experimental allergic encephalomyelitis ANIMAL STUDIES Kim et al. (1987) have demonstrated that anti-DNA production by anti-DNA-secreting hybridomas can be inhibited by the addition of anti-Ids to anti-DNA. In this study, a series of anti-DNA antibody-producing hybridomas were obtained by fusing spleen cells from 6-month-old MRL/lpr autoimmune prone mice with P3X63-Ag8 myeloma cells. Rabbit anti-Id antibodies specific for several of the hybridoma proteins were prepared. It was shown that the anti-Id antibody inhibited immunoglobulin secretion by the hybridoma cells in an Id-specific manner. Inhibition of antibody production was not due to a cytotoxic effect, since the anti-Id, in fact, stimulated proliferation of the hybridoma cells. In order to assess the anti-Id network in murine experimental autoimmune encephalomyelitis (EAE), Id-bearing monoclonal antibodies (mAb) to human myelin basic protein (MBP) peptide acetyl 1-9, as well as mAb anti-Id, were developed in EAE-susceptible PL/j mice (H-2u) (Zhou and Whitaker, 1992). These mice recognize MBP residues acetyl 1-9 as an encephalitogenic determinant. Reactivities of PL/j Idbearing mAbs to MBP and to MBP peptides were identical to those of mAbs generated against the same MBP peptide in EAE-resistant BALB/C mice (H-2d), even though isotypes of the mAbs differed. By using an inhibitory ELISA and immunoblotting, it was demonstrated that one PL/j mAb anti-Id recognized a public or framework Id, whereas another PL/j mAb-anti Id was directed to a private Id more restricted to the paratopic site. Two Id-bearing PL/j mAbs shared a cross-reactive Id (IdX) on the light chain, and an interstrain IdX was present on both the heavy and light chains of mAbs raised in PL/j and BALB/C mice to the same MBP peptide. The PL/j mAb anti-Id was
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Blank et al, 1994 Hahn and Ebling, 1984 Zanetti et al., 1984 Nordling et al., 1991 Aguis and Richmann, 1986 Koazky and Mirshahi, 1990 Roubaty et al., 1990 Zou and Whitaker, 1993
capable of cross-regulating the production of Id-bearing mAbs by hybridomas across murine strains. These findings suggest that manipulation of the Id network may provide a means for modifying autoimmune demyelinating diseases of the central nervous system (Zhou and Whitaker, 1992).
STUDIES OF PERIPHERAL LYMPHOCYTES IN HUMAN AUTOIMMUNE DISEASE Abdou et al. (1981) reported that the binding of human anti-DNA antibodies to DNA could be blocked by autologous sera obtained from patients with SLE when their disease was in remission and by the F(ab')2 and Fab fragments derived from these sera. The inhibition of binding was interpreted as being due to the presence of anti-Ids in the inactive sera that reacted with the binding site of the anti-DNA antibodies present in the sera of patients when their disease was active. Additional findings extending this concept have also been presented (Reissman and Abdou, 1983). Studies of anti-DNA and anti-F(ab')2 antibodies were performed by enzyme-linked immunosorbent assay (ELISA) in 51 patients with SLE (Silvestris et al., 1984). Patients with severe, uncontrolled disease showed high levels of anti-DNA and low levels of anti-F(ab')2 antibodies. Patients with quiescent SLE usually showed high levels of anti-F(ab')2 and low levels of anti-DNA antibodies. Isolated anti-F(ab')2 antibodies from autologous SLE remission serum or from the sera of unaffected siblings of SLE patients showed maximum inhibition in test systems using affinity-purified SLE anti-DNA antibodies reacting with single-stranded DNA. In another study, it was demonstrated that specific anti-Ids can suppress the production of anti-DNA
antibodies by peripheral blood mononuclear cells from active SLE patients (Epstein et al., 1987). These authors have developed an ELISA system for measuring in vitro anti-DNA antibody production by peripheral blood mononuclear cells (PBMC) from patients with SLE. Using this technique, the PBMC from 74% of serologically active SLE patients produced levels of anti-DNA antibodies that were increased 2 SD above the mean of 18 ± 9 lU/ml for normal subjects. Furthermore, the addition of 3-1, a monoclonal antiId antibody that recognizes a cross-reactive determinant on anti-DNA antibodies, was shown to specifically inhibit anti-DNA production/« vitro. This finding supports previous work that implicates antiIds among the regulatory mechanisms that can control synthesis of anti-DNA antibodies in patients with SLE and previous studies reporting inhibition of idiotypic antibodies by the addition of anti-Id in vitro cultures of human PBMC. Zhou and Whitaker (1990) raised a mAb of the IgGl/kappa isotype against human myelin basic protein (MBP) pepfide acetyl 1-9. This mAb, termed F23, reacted with human MBP and human MBP peptides acetyl 1-9, 1-14 and 1-44, but not with MBP peptides 10-19, 80-89, or 45-89. According to the guidelines of the molecular recognition theory, a complementary peptide to human MBP peptide 1-9 was synthesized and used to raise murine mAb with anti-Id activity. Two mAb anti-Id, F25F7 and F25C8, both of the IgM/kappa isotype, were selected for further study. The cross-reactive anti-Id suppressed antibody secretion of Id-producing hybridoma cells in an Idspecific manner, and kinetic studies suggest an intracellular mechanism for the suppression. These cross-reactive Id among antibodies to different MBP peptides imply that the same V region genes of kappa L chains are involved in the selection of antibodies to an autoantigen, like MBP, and may play a role in the modulation of immune responses against MBP in certain inflammatory demyelinating diseases (Zhou and Whitaker, 1990). In another study (Fong et al., 1984), rabbit anti-Id antibodies to human rheumatoid factor (RF) autoantibodies were isolated by affinity chromatography on rabbit anti-human IgG Fc sepharose 4B. The antiId antibodies bore the "internal image" of the antigen, human IgG. They reacted specifically with multiple human monoclonal and polyclonal IgM-RF, independent of any particular light or heavy chain amino acid sequence. The anti-Ids did not react with IgM or IgG proteins lacking RF activity. The experi-
ments in this study (Fong et al., 1984) determined the potential of the "internal image" antibodies to modulate in vitro lymphocyte fiinctions. The addition of anti-Id antibody to peripheral blood mononuclear cell cultures from patients with rheumatoid arthritis elicited lymphocyte proliferation, but not RF synthesis. The antibody did not induce the proliferation of lymphocytes from a normal individual. Moreover, the anti-Id specifically suppressed IgM-RF secretory responses when preincubated with B cells before co-culture with autologous pokeweed mitogenactivated T cells. This study showed that the anti-Id antibodies with the "internal image" of antigen are capable of interacting with B-cell receptors in an antigen-restricted manner, and posses specific immunomodulatory properties (Fong et al., 1984). Takeuchi et al. (1985), further studied the effect of anti-Id antibody on the in vitro production of RF in rheumatoid arthritis patients with cross-reactive idiotypic determinants. Anti-Id antibodies were developed against monoclonal RF (Kam-RF) by a cell fusion procedure. These antibodies were idiotypespecific. The anti-Id antibody strongly suppressed the in vitro production of RF by lymphocytes from unrelated rheumatoid arthritis patients with cross-reactive idiotypes. These results indicate that anti-Id antibody may influence the regulation of RF production in patients with rheumatoid arthritis (Takeuchi et al., 1985). Kajima et al. (1986) have reported on the suppression of in vitro human anti-thyroglobulin antibody secretion in Epstein-Barr virus transformed B lymphocytes by private and cross-reactive anti-Id antibodies. It was suggested that interactions between idiotype and anti-Id may play a role in the immune regulation of human chronic thyroiditis (Kajima et al., 1986). Anti-Ids as Specific Carriers of Toxins Another method by which anti-Ids can be employed in the treatment of autoimmune diseases is as specific carriers of toxins. Sasaki et al. (1986) have developed a new way of using anti-Id antibodies by conjugating them with cytotoxic agent, NCS (Neocarzinostatin). The conjugates killed Id-positive EBV-transformed B-cell clones, resulting in the suppression of anti-DNA production. Later on, the same group demonstrated that this method is capable of manipulating the human anti-DNA system through the specific elimination of anti-DNA Id-positive cells from lymphocytes in the peripheral blood (Sasaki et al., 1989).
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Following these in vitro studies (Sasaki et al., 1986; 1989), Harata et al. (1990) demonstrated a successful treatment of NZBAVF, mice disease by using anti-Idconjugated NCS. In this study (Harata et al., 1990), in vivo administration of anti-Id antibodies conjugated with NCS brought about an improvement in the survival rate of female NZBAV F^ mice. It also caused a retardation of development of lupus nephritis and decreased the numbers of anti-DNA-reproducing cells. The suppression of anti-DNA antibody synthesis was specific and Id-mediated. These results indicate that the use of a limited number of anti-Id antibodies in combination with a cytotoxic agent may be applicable therapeutically to autoimmune diseases. Saporin is one of the most widely used toxin compounds for immunotoxin preparation. We have recently demonstrated the suppression of experimental systemic lupus erythematosus (SLE) with specific anti-Id antibody-saporin conjugate (Blank et al., 1994). The antiId treatment was specifically shown to reduce anti-DNA antibodies by a specific hybridoma cell line (Blank et al., 1994). The immunotoxin (saporin) had a significantly superior result compared with the anti-Id itself Yet, although impressive, the effect of the saporin in reducing anti-DNA antibody production and abrogation of SLE manifestations was not better than the antiId alone (Blank et al., 1994). (For More details on anti-Id treatment in this model, see the next section). Valderrama et al. (1988) have treated experimental myasthenia with autologous idiotypes linked to muramyl dipeptide. Rabbits were injected with purified acetylcholine receptor (AchR) from Torpedo, California. Polyclonal affinity purified anti-AchR antibodies (Ids) were coupled covalently to muramyl dipeptide and injected back into the same (autologous) rabbits from which the Ids were obtained. Treated animals developed anti-Ids that bound to the F(ab')2 fragments of the Ids as demonstrated by ELISA and that also blocked binding of Ids to AchR in a radioimmunoassay. Treated animals showed a protective effect compared to control animals when challenged with a second injecfion of AchR. No apparent toxicity from the treatment was noted (Valderrama et al., 1988). In Vivo Modulation of the Idiotype Network Subsequent to the encouraging results of the experiments involving in vitro modulation of autoantibody idiotypes by anti-Id treatment, in vivo studies were undertaken. These studies were conducted in animals
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and included: 1) passive administration of anti-Id reagents to experimental animals, and 2) immunization of mice against their own pathogenic Id. Passive Administration Of Anti-Id To Autoimmune Animals In mouse models of lupus, resuhs have been conflicting, probably reflecting different influences of various anti-Ids on autoimmune mechanisms. In B/W mice, administration of an anti-Id directed against a major CRI on anti-DNA antibodies resulted in the disappearance of anti-DNA antibodies bearing the target idiotype and in the prolongation of survival due to a delay in the onset of nephritis (Hahn and Ebling, 1984). These researchers have identified three dominating Id in NZB/W F, mice by the time they develop nephritis at 30 weeks of age: IdX, Id GNI and Id GN2 comprise about 85% of their total serum Ig. While Id GNI and GN2 comprise approximately 50% of the Id deposited in the glomeruli, IdX is detectable on less than 5% of glomerular Ig (Hahn and Ebling, 1987). While a monoclonal antibody to Id GNI was administered repeatedly to NZB/W F, female mice beginning at 20 weeks of age, the levels of all three Id were significantly suppressed for 10 weeks, during which time disease developed in the controls, but not in the treated mice. Although IdX continued to be suppressed, levels of Id GNI escaped suppression and rose to levels similar to those in the control mice and fatal nephritis rapidly ensured. The Ig eluted from the glomeruli of these mice were composed entirely of Id GN2 Ig. This treatment with anti-Id GNI or with anti-IdX (Hahn and Ebling, 1987) prolonged the lives of the mice by 10 weeks. In contrast to the data described by Hahn and Ebling (1984), administrating an anti-Id directed against Id-130 (a dominant idiotype of MRL anti-DNA antibodies) to MRL mice, augmented the production of the Id-130 idiotype and anti-DNA antibodies (Teitelbaum et al., 1984). However, Mahana et al. (1987) were able to suppress anti-DNA production in MRL mice by the passive transfer of anti-Id D23 (an idiotype of a monoclonal polyspecific natural autoantibody reacting mainly with ds-DNA and ss-DNA). These conflicting results can be resolved if we assume that various anti-Ids regulate idiotype-bearing autoantibodies in different ways, some acting to suppress idiotype production and others augmenting idiotype expression.
The importance of the idiotypic network is represented in experimental SLE induced by active immunization of naive mice with an anti-DNA idiotype (Ab 1) emulsified in adjuvant. The mice after 4 months of incubation generate Ab3 having anti-DNA activity. In addition, the mice develop other serological markers for SLE associated with clinical and histopathological manifestations characteristic of the disease (Blank et al., 1988; 1990; Mendlovic et al., 1988). To confirm further the etiological role of the idiotype in the experimental model, the mice were treated with specific anti-Id antibodies (anti-Id) which were also conjugated to a toxin-saporin (Immunotoxin (IT)) (Blank et al., 1994). Pretreatment of hybridoma cell line producing the anti-anti-Id (anti-DNA = (Ab3)) for 48 h with the anti-Id MoAb (Ab2) reduced the production of anti-DNA by 58%, while pretreatment with the IT resulted in 86% decrease in antiDNA secretion (saporin alone had only 12% effect). The anti-Id MoAb had no effect on the production of immunoglobulin by an unrelated cell line. In vivo treatment of mice with experimental SLE led to a significant decrease in titers of serum autoantibodies, with diminished clinical manifestations. The results were more remarkable when the IT was employed. These successive effects were specific, since an antiId treatment of experimental anti-phospholipid syndrome was of no avail. The anti-Id effect was mediated via a reduction in specific anti-DNA antibody-forming cells, and lasted only while anti-Id injections were given. Discontinuation of the anti-Id injection was followed by a rise in titres of anti-DNA antibodies. No immunological escape of new anti-DNA Ids was noted. Our results point to the importance of pathogenic idiotypes in SLE and to the specific potential of implementing anti-Id therapy, enhanced by the conjugation of the anti-Id to an immunotoxin, in particular one with low spontaneous toxicity (Blank et al., 1994). The F1 progeny of the cross between SWR and NZB mice (SNFl) develop severe immune complex glomerulonephritis. An idiotypically related family of nephritic antibodies (IdLNFl) has been shown to be important in the pathogenesis of autoimmune glomerulonephritis in these mice. Uner et al. (1994) have injected the SNFl mice with rabbit anti-IdLNFl antibodies, which has resulted in significant suppression of IdLNFl + Ig (G + M) and IgG production. The decrease appeared to be mediated via significant decreases in the percentage of IdLNFl-expressing B cells and CD4 + IdLNFl-specific T cells in the treated SNFl mice compared to the controls (Nordling et al.,
1992). This was accompanied by a significant increase in survival with delayed onset of glomerulonephritis. Surprisingly, there was no difference in the incidence of anti-DNA antibody production between the treated and control SNFl mice. Nordling et al. (1992) have recently described a spontaneously occurring inflammatory and erosive joint disease in male DBA/1 mice. These mice have an increased serum antibody level to collagen II in a fraction of the male DBA/1 mice. Administration of antibodies with an anti-Id activity to anti-collagen II antibodies and with an affinity for determinants on isolated synergeneic IgG Fc but not on intact IgG, was shown to interfere with the development of the spontaneous arthritis. In another study (Tarutani, 1993), collagen-induced arthritis was shown to be suppressed with monoclonal anti-Id antibody. Anti-Id treatment has been tried, as well, in autoimmune tubulointerstitial nephritis (TIN) in Brown Norway rat (Zanetti et al., 1984). In vivo injection of anti-TBM (tubular basement membrane) Id before immunization with TBM, resulted in a significant selective suppression of antibodies to the autologous collagenase-solubilized TBM moiety and a corresponding decrease of TIN (Zanetti et al., 1984). Agius and Richman (1986) have used isogeneic anti-Id monoclonal antibodies to modify experimental autoimmune myasthenia gravis (EAMG) in Lewis rats. Pretreatment with anti-Id not only perturbed this Id—anti-Id network, but also suppressed the overall polyclonal anti-AchR response with resultant protection of actively immunized animal from EAMG (Aguis and Richmann, 1986). Other studies have confirmed the beneficial effect of anti-Id antibodies on EAMG (Blair et al., 1987; Sunblad et al., 1989; Verschuuren et al., 1991). Experimental autoimmune uveoretinitis (EAU) is induced in rats with injection of S-antigen (S-Ag) in complete Freund's adjuvant (CFA) (de Kozak, 1990). de Kozak has shown that injection of rats with the mouse anti-SAg mAb S2D2 either simultaneously with or before S-Ag challenge led to an anti-Id response and to inhibition of EAU. Syngeneic Immunization With Idiotypes Another method for treating animals is by active immunization with the idiotype instead of passive administration of the anti-idiotype. In NZBAV Fl mice, it was found that injection of a monoclonal anti-DNA Id resulted in a decrease of autoantibody levels and a partial improvement of the disease (Hahn and Ebling,
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1983). The effect was transient, however, and antiDNA antibodies appeared which did not exhibit the injected idiotype. In a different experiment, mice were inoculated with syngeneic anti-DNA IgG together with muramyl dipeptide. It was found that anti-DNA antibody levels were suppressed and that an anti-Id specific for the injected IgG appeared (Zouali et al., 1985). In another study, the immunization of BAV mice with the PME 77 anti-DNA monoclonal antibody (a syngeneic antibody bearing the idiotype present in most B/W sera) was investigated (Jacob and Iron, 1984). The PME 77 mAb immunization regimen induced the production of auto-anti-Id antibodies and abrogated the expression of the PME 77 idiotype in B/W-treated mice. In contrast, untreated mice and control B/W mice receiving NZB polyclonal IgG2b which lacked detectable DNA binding capacity, expressed PME 77 idiotypes. These results demonstrate that the expression of idiotypes borne by autoantibodies may be modified through the induction of auto-anti-Id antibodies. Treatment with anti-AchR idiotypic antibodies resulted in improvement of modulation of the immune response of mice to acetylcholine receptor (Souroujon et al, 1985). In vivo Anti-Id Therapy In Human Autoimmune Diseases Anti-Id therapy has not been tried in human autoimmune diseases directly. One study used the approach of passage of plasma over an anti-Id column which removes antibodies bearing the common idiotype (Macleod et al., 1988). In this study, an anti-3I Id column was used to remove anti-ds DNA antibodies bearing the 31 Id from patients with SLE. There were no significant side effects. The recent development of "humanized" murine or rat monoclonal antibodies opens the way for direct injection of Id-bearing or antiId antibodies into patients. Much attention has been given in recent years to the possibility that the immunomodulating effects seen in autoimmune diseases treated with IVIG (intravenous immunoglobulins) may be applied by anti-Id antibodies present in the gammaglobulin preparations. Indeed, recent studies strengthen the likelihood that anti-Id antibodies present in IVIG preparations may control autoimmune reactions. Patients who developed antibodies to their own circulating factor VIII can bleed severely. IVIG can block the secretion of such
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Table 3. Specific Anti-Ids Against Disease Related Autoantibodies Found In IVIG Anti-DNA Anti-thyroglobulin Anti peripheral nerve Anti-factor VIII: C Anti-intrinsic factor Anti-membrane antigen of erythroblasts Anti-platelet gpIIb/IIIa Anti-neutrophil cytoplasmic antigen antibodies and this property has been attributed to the presence of naturally occurring anti-Id antibody to the antibody against factor VIII (Sultan et al., 1984; Timmerman et al., 1985). Subsequently IVIG, prepared from large pools of plasma from normal donors, were found to contain specific anti-Ids against a number of disease-related autoantibodies (see Table 3), including antibodies to DNA, thyroglobulin, gastric intrinsic factor (Rossi and Kazatchkine, 1989; Dietrich and Kazatchkine, 1990), peripheral nerve (Van Doom et al., 1990), neutrophil cytoplasmic antigens (Rossi et al., 1991), platelet gpIIb/IIIa (Berchtold et al., 1989), and membrane antigen of erythroblasts (McGurie et al., 1987). Dietrich and Kazatchkine (Dietrich and Kazatchkine, 1990) found that anti-Ids in IVIG recognize a cross-reactive idiotype on human anti-thyroglobulin (TG) autoantibodies that was defined by heterologous anti-Id antibodies, termed anti-T44 antibodies. The idiotype was expressed on anti-thyroglobulin IgG of eight out of nine patients with Hashimoto's disease but on no IgG of five healthy individuals who were tested. Anti-thyroglobulin autoantibodies expressing the T44 idiotype exhibited a restricted epitopic specificity against human thyroglobulin, thus, IVIG contain anti-Id antibodies directed against an immunodominant cross-reactive idiotype of human anti-TG autoantibodies. Evans and Abdou (1993) have demonstrated that anti-Id antibody and its (ab')2 fragments prepared from pooled normal human IgG had a partial inhibitory effect on the spontaneous in vitro secretion of anti-DNA antibodies from blood mononuclear cells of lupus patients. The inhibitory effect was specific for anti-DNA secretion as the anti-Id failed to inhibit the spontaneous secretion of anti-tetanus toxoid, in the same culture supematants (Evans and Abdou, 1993).
Several lines of evidence demonstrate the presence in IVIG of anti-Ids against autoantibodies. These include: 1. F(ab')2 fragments from IVIG inhibit the biding of autoantibodies to their autoantigens (Sultan and Kazatchkine, 1984; Rossi et al., 1988; Van Doom et al., 1990); 2. F(ab')2 fragments with autoantibody activity are specifically retained on affinity columns of sepharose-bound F(ab \ fragments from IVIG (Sultan et al., 1987; Rossi et al., 1988; 1991); 3. IVIG contain no antibody specificities against the most common allotypes expressed in the F(ab')2 region of human IgG (Rossi et al., 1988); 4. The binding of IVIG to affmity-purified autoantibodies is specifically displaced by F(ab \ fragments from heterologous polyclonal anti-autoantibody anti-Ids (Rossi and Kazatchkine, 1989). The high number of donors contributing to IVIG endows the preparation with anti-Id specificities that may not necessarily be detectable in plasma from single healthy individuals. The IVIG may be efficient in some autoimmune diseases by providing a source of anti-Ids with a wide range of specificities brought as interconnected antibody species that may compensate for altered connectivity of the immune network of patients with autoimmune diseases (Rossi and Kazatchkine, 1989). Immunomodulation Of Experimental Animal Models Of Autoimmunity With Idiotype-Specific T Cells And Antibodies That bind To T-Cell Receptor (TCR) Still another approach introduced by Shoenfeld and Mozes (1990) utilizes T-suppressor cells specific to pathogenic idiotypes. Several papers have reported decreased numbers and activity of T cells in several mice models for SLE as well as in other animal models for autoimmune conditions as summarized by Tomer and Shoenfeld (1989). Similarly decreased numbers and activity of Ts cells in humans with SLE and other autoimmune diseases have regularly been reported. If the production of autoantibodies in SLE and other autoimmune states is related to down-regulation of Ts, the reconstitution of Ts cell numbers and activity, and especially the Ts specific to the harmful autoantibody in question, may lead to amelioration of disease manifestations. In fact, several studies have suggested this very possibility (Pachner and Kantor, 1984; Smith et al., 1987).
In a recent experiment, Ts cells (CD8+) specific to the pathogenic idiotype 16/6 that were MHC-restricted in their function were generated in vitro. The suppressor cells specific for the pathogenic idiotype 16/6 were generated from populations of normal T cells exposed to silica beads coated with SA-1 (16/6 Id+) mAb in vitro (Mendlovic et al., 1988). Treatment of B ALB/C mice in which SLE was induced experimentally (Blank et al., 1991) with the Id-specific Ts cells, resulted in a decline in the titers of autoantibodies in the sera and in clinical manifestations (increased ESR, low WBC count, and proteinuria). Furthermore, no immunoglobulin deposits were found in the mesangium of the kidneys in contrast to kidneys of the 16/6 Id-immunized mice treated with control IgM specific Ts cells. It should be noted that this treatment failed once the disease was well established (5 months after immunization with 16/6). These results emphasize the importance of the role played by pathogenic idiotypes in murine SLE and the role Ts cells may play in induction as well as in the treatment of autoimmune conditions. In the same vein, strategies that might specifically block or inactivate helper T cells necessary for the sustained production of anti-DNA pathogenic antibodies may provide a specific suppression of disease progression. As discussed earlier, Hahn and her colleagues have raised CD4+ T-cell clones specific for Id GN2. Their program includes inoculating low doses of anti-Id GN2 to NZB/W Fl mice, harvesting T cells by draining lymph nodes, and obtaining T cells from the spleens of lupus mice with active nephritis. Stimulating these clones with rat concanavalin A supernatant, DNA antigen soluble Id GN2, or hybridoma B cells expressing Id GN2 on their surface, yields T-cell clones which significantly increase the production of Id GN2 IgG anti-DNA in a culture using B cells from the spleens of 16-week-old lupus mice. One of these clones, isolated from the spleens of nephritic NZB/W Fl mice (termed TH 27.6), has been characterized (Ando et al., 1987). It increases the synthesis of Id GN2 anti-DNA by NZB/W B cells eightfold, whereas it augmented total IgG only twofold. It is an autoreactive clone of the TH2 types: it can be activated by H2'^ without addition of DNA, and secretes B-cell rather than T-cell growth factors, including IL-4, IL-5 and IL-6, but not IL-2. These studies may pave the way for new directions in disease management.
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Roubaty et al. (1990) have described the protective immunity against experimental autoimmune thyroiditis induced exclusively by a thyroglobulin (Tg)-specific cytotoxic T-cell clone and showed that this down-regulation occurred through the generation of anti-Id antibodies (Ab2 Beta) which recognized the paratope of anti-Tg mAb (Abl) specific to the pathogenic epitope of the Tg molecule (Roubaty et al., 1990). Protection from experimental allergic encephalomyelitis (in Lewis rats) was conferred by a monoclonal antibody directed against a shared idiotype on rat T-cell receptors specific for myelin basic protein (MBP) (Owhashi and Heber Katz, 1988). Finally, it was demonstrated by Rohowsky et al. (1994) that T-cell clones specific for MBP have the ability to induce proliferative responses in resting T lymphocytes in the autologous mixed lymphocyte culture (AMLC). Modulation of the T-cell receptor from the surface of the clones decreased their AMLC stimulatory ability, indicating that idiotype-like determinants on the T-cell receptor of autoantigen T-cell clones are capable of triggering anti-Id T-cell responses (Rohowasky-Kochan et al., 1994).
HOW CAN THE MANIPULATION OF THE IDIOTYPE NETWORK AFFECT IDIOTYPE EXPRESSION The mechanism of suppression of the idiotype antibody response by the anti-Id antibody is unclear. Two possibilities exist and they entail clonal deletion of B cells and production of suppressor T cells (Kohler et al., 1974; Eichmann, 1975). Simple binding of idiotypes by the anti-Id antibody is probably inadequate to explain the mechanism of suppression; the small amount of anti-Id necessary for suppression in the above mentioned experiments was greatly exceeded by the amounts of idiotypic antibody produced by immunized control animals (Hart et al., 1972). The down-regulation of idiotype expression may be caused by the blocking of immunoglobulin synthesis or by the formation of complexes. For example, it has been suggested that the decrease in the binding affinity of an antibody response is related to the appearance of an auto-anti-Id (Zouali and Diamond, 1990). It is not yet clear if the anti-Id acts directly on B cells to down-regulate production of anti-DNA antibodies or if it acts through an idiotypic network involving T cells (Zouali and Diamond, 1990). Indeed, besides inducing anti-Id Ab, treatment of
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mice anti-DNA IgG and MDP could also have induced either a depression of Id-specific T-helper cells or a stimulation of Id-bearing T-suppressor cells (Zouali et al., 1985). Support for this view comes from the recent demonstration that administration of an antiId Ab to anti-DNA suppresses the pathogenic Ab to DNA NZBAV mice (Hahn and Ebling, 1984). Future experiments will no doubt add to the better understanding of the mechanisms involved in idiotype expression by manipulation of the idiotype network. Therapeutic Problems In Modulation Of Idiotypes of Autoantibodies It is now understood that the manipulation of autoantibody idiotypes might be utilized in the treatment of autoimmune diseases. Indeed, encouraging results have been reported in lupus-prone mice models. However, the effect of anti-Id antibodies appears to be complicated in the case of in vivo administration in autoimmune mice (Hahn and Ebling, 1984; Teitelb a u m e t a l , 1984). There are many factors influencing the biological effectiveness of anti-Id treatment (Table 4). Id manipulation can result in down- or up-regulation of the immune response depending on the time-window of the disease, the age of the animals, the isotype, the affinity, and the amount of the Id or the anti-Id injected. The biological effectiveness of the treatment also depends on the functional properties of the antiId, i.e., whether it mimics the configuration of the antigenic motifs, or whether it interacts with regulatory Id that ensures connectivity between various Id families (Brown et al., 1979; Zouali et al., 1985; Sasaki et al., 1986; Zouali and Diamond, 1990). Some of the problems observed in treatment with Id manipulation are summarized in Table 5. Although some studies have shown that anti-Id administration can suppress the production of anti-DNA antibodies and nephritis. Table 4. Factors Influencing the Biological Effectiveness of Treatment with Id Modulation Isotype of Id anti-Id injection Affinity of Id or anti-Id injected Amount of the Id or anti-Id injected Functional properties of the anti-Id Time-window of the disease Age of the animals Method of manipulation: passive transfer, immunization
Table 5. Modulation of Autoantibody Idiotypes with Anti-Id Antibodies: Therapeutic Problems • No effect of treatment • Partial effect of treatment • Transient reduction of autoantibodies • Necessity for repeated administration of anti-Id • Change in the dominant Id on pathogenic autoantibody: escape from suppression • Inadequacy of therapy while using anti-Id alone: treatment with anti-Id cytotoxic agent or "cocktail" of anti-Ids • Unpredictability of treatment with Id manipulation: up- rather than down-regulation of immune response the effect was transient and anti-DNA antibodies appeared which did not bear the injected idiotype (Hahn and Ebling, 1983). Moreover, in other studies, treatment of mice with anti-Id anti-DNA antibodies was found to have no effect (Teitelbaum et al., 1984). Yet another problem is the escape from suppression of Id production by anti-Id (Hahn and Ebling, 1984). Therefore, although administration of anti-Id was effective in reducing an undesirable antibody response after the target Id was present on circulating antibodies, the benefits were limited probably by Id "switch" or by increased synthesis of pathogenic antibodies bearing a minor Id. Such a change may be prevented by administration of polyclonal or mixed monoclonal anti-Id reagents. More distressing, however, is the fact that anti-Id reagents can augment rather than suppress the secretion of idiotypic antibodies (Teitelbaum et al., 1984). These conflicting results can be resolved if we assume that various anti-Ids regulate idiotype-bearing autoantibodies in different ways: some acting to suppress idiotype production and others augmenting idiotype expression.
REFERENCES Abdou NI, Wall H, Lindsley HB, Halsey JF, Suzuki T Network theory in autoimmunity. In vitro suppression of serum anti-DNA antibody binding to DNA by antiidiotypic antibody in systemic lupus erythematosus. J Clin Invest 1981;67:1297-1304. Aguis MA, Richmann DP. Suppression of development of experimental autoimmune myasthenia gravis with isogeneic monoclonal anti idiotypic antibody. J Immunol 1986;137:2195-2198. Ando DG, Scroarz LL, Hahn BH. Mechanisms of T and B
It is clear that modulation of the autoantibodies' idiotype-anti-idiotype (Id-anti-Id) network will perturb other Id-anti-Id systems through the connections and cross-reactivities of the idiotypes and anti-Ids involved. Removal of specific idiotypes will eliminate not only those borne by specific autoantibodies but those on antibodies directed against other auto-antigens and bacteria. This might have unpredictable consequences on the body's ability to fight infection.
CONCLUSIONS The central goal in the therapy of autoimmune diseases is to develop potent tools able to exert specific control of the immune response to self antigen. Anti-Id treatment may provide such specific immunomodulation because the relevance of the idiotypic network in autoimmunity is well documented. Indeed, encouraging results have been reported in experimental autoimmune diseases. There are, however, some problems in this treatment, such as nonresponse or transient, partial response to anti-Id manipulation. Moreover, unpredictable consequences as up-regulation instead of down-regulation of production of autoantibodies bearing pathogenic idiotypes have been observed. In order to devise anti-Id therapy to autoimmune diseases, it is crucial to define the panel of pathogenic idiotypes of autoantibodies involved in autoimmune disease. More animal experiments may highlight the conditions necessary to induce suppression rather than enhancement of antibody production. Through the use of in vitro immunization methods, human anti-Id antibodies may ultimately be produced obviating the need to administer animal antibodies. Thus, despite all the present obstacles, treatment with anti-Id antibodies may well be practical in the not too distant future.
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B-cell lymphoma with monoclonal anti-idiotype antibody. N Engl J Med 1982;306:517-522. Miller RA, Hart S, Samoszuk M, Coulter C, Brown S, Czerwinski D, Kelkenberg J, Ronyston I, Levy R. Shared idiotypes expressed by human B-cell lymphomas. N Engl J Med 1989;321:851-857. Nordling C, Holmdahl R, Klareskog L. Down of collagen arthritis after in vitro treatment with a syngenic monoclonal anti-idiotypic antibody to a cross reactive idiotype on collagen II autoantibodies. Immunology 1991;72:486— 492. Nordling C, Kleinau S, Klareskog L. Down-regulation of a spontaneous arthritis in male DBA/1 mice after administration of monoclonal anti-idiotypic antibodies to a cross-reactive idiotype on anti-collagen antibodies. Immunology 1992;77:144-146. Owhashi M, Heber Katz E. Protection from allergic encephalomyelitis conferred by a monoclonal antibody directed against a shared idiotype on rat T cell receptors specific for myelin basic protein. J Exp Med 1988; 168: 2153-2164. Pachner AR, Kantor ¥S. In vitro and in vivo actions of acetylcholine receptor educated suppressor T-cells lines in murine experimental autoimmune myasthenia gravis. Clin Exp Immunol 1984;56:659-668. Paul E, Manhiemer-Lory A, Livneh A, et al. Pathogenic anti-DNA antibodies in SLE: idiotypic families and genetic origins. Int Rev Immunol 1990;5:295-313. Reissman P, Abdou NI. The network theory in autoimmunity: modulation of z>z vitro anti-DNA antibody secretion by specific autologous anti-idiotype activated T suppressor cells in human systemic lupus erythematosus (SLE): correlation with disease activity (abstract). Clin Res 1983;31:351A. Rohowasky-Kochan C, Eiman D, Denny T, Oleske J, Cook SD. Induction of autologous mixed lymphocyte culture responses by myelin basic protein-reactive T cell clones. J Neuroimmunol 1994;50:59-70. Rossi F, Kazatchkine MD. Anti-idiotypes against autoantibodies in polled normal human polyspecific Ig. J Immunol 1989; 143:410^^-4109. Rossi F, Sultan Y, Kazatchkine MD. Anti-idiotypes against autoantibodies and alloantibodies to VIILC (antihemophylic factor) are present in therapeutic polyspecific normal immunoglobulins. Clin Exp Immunol 1988;74: 311-316. Rossi F, Jayne DR, Lockwood CM, et al. Anti-idiotypes against anti-neutrophil cytoplasmic antigen autoantibodies in normal human polyspecific IgG for therapeutic use and in the remission sera of patients with systemic vasculitis. Clin Exp Immunol 1991;83:298— 303. Roubaty C, Bedin C, Charriere J. Prevention of experimental autoimmune thyroiditis through the anti-idiotypic network. J Immunol 1990;144:2167-2172. Sasaki I, Muryoin T, Takai O, Tamate E, Ono Y, Koide Y, Ishida N, Yoshinaga K. Selective elimination of anti-DNA antibody-producing cells by anti-idiotypic antibody con-
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idiotypes linked to muramyl dipeptide. Clin Exp Immunol 1988;73:123-127. Van Doom PA, Brand A, Rossi F, et al. On the mechanism of high-dose intravenous immunoglobulin treatment of patients with chronic inflammatory demyelinating polyneuropathy. J Neuroimmunol 1990;29:57-61. Verschuuren JJ, Graus YM, Van-Breda-Vriesman PJ, Tzartos S, De-Baets MH. In vivo effects of neonatal administration of antiidiotype antibodies on experimental autoimmune myasthenia gravis. Autoimmunity 1991; 10:173-179. Zanetti M. The idiotype network in autoimmunoprocesses. Immunol Today 1985;6:299-302. Zanetti M, Mampaso F. Wilson CB. Anti idiotype as a probe in the analysis of autoimmune tubulointerstial nephritis in Brown Norway rat. J Immunol 1984;131:1268-1274. Zhou SR, Whitaker JN. An idiotype shared by monoclonal antibodies to different peptides of human myelin basic
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protein. J Immunol 1990;145:2554-2560. Zhou SR, Whitaker JN: Interstrain cross-reactive idiotypes on monoclonal antibodies to an encephalitogenic myelin basic protein peptide. Clin Immunol Immunopathol 1992;63:7^83. Zhou SR, Whitaker JN. Specific modulation of T cells and murine experimental allergic encephalomyelitis by monoclonal anti idiotypic antibodies. J Immunol 1993; 150: 162916-^2. Zouali M, Diamond B. Idiotype-mediated intervention in systemic lupus erythematosus. J Autoimmun 1990;3:381— 388. Zouali M, Jolivet M, Leclerc C, Ravisse P, Audibert F, Eyquem A, Chedio L. Suppression of murine lupus autoantibodies to DNA by administration of muramyl dipeptide and syngeneic anti-DNA. J Immunol 1985; 135: 1091-1095.
MANIPULATION OF AUTOANTIBODY IDIOTYPES IN AUTOIMMUNE DISEASES Dan Buskila, Mahmoud Abu-Shakra and Yehuda Shoenfeld Rheumatic Disease Unit, Soroka Medical Center and Ben-Gurion University, Beer Sheva, and Research Unit of Autoimmune Diseases, Department of Medicine "B ", Sheba Medical Center, Tel-Hashomer, and Sackler Faculty of Medicine, Tel-Aviv University, Israel The idiotypic network is an important mechanism for controlling the immune repertoire (Jeme, 1974; Paul et al., 1990; Buskila and Shoenfeld, 1992), and autoimmune diseases may be attributed to the disturbance of the network (Zanetti, 1985; Burdette and Schwarts, 1987). Thus, one may speculate that manipulation of idiotypes (pathogenic, cross-reactive) of autoantibodies (anti-Id immunity) may be effective in the treatment of autoimmune diseases. Indeed, there are encouraging reports coming from another field of medicine, which is using anti-idiotypic (anti-Id) antibodies in the treatment of B-cell tumors (Miller et al., 1982; 1989; Brown et al., 1989). In this novel approach to treating B-cell lymphomas and leukemias, anti-Id antibodies have as their target a tumor-specific antigen, the idiotype of the cell surface immunoglobulin present on B cells.
Table 1. Methods by which Autoantibody Idiotypes Might be Manipulated • Injection of anti-Id: Anti-Id directly regulates autoantibodies. • Direct injection of a common Id: Formation of anti-Id down regulates autoantibodies. • Injection of anti-Id conjugated to a cytotoxic agent: a) Anti-Id targets Ab-producing cells b) Toxin specifically destroys them • Passage of plasma over an anti-Id column: Removal of Ab bearing the common Id. • Treatment with poly specific immunoglobulins (IVIG): Anti-Id suppression of autoantibodies mediated by anti-Ids present in IVIG. Treatment with Id-specific T cells.
These results prompted in part the studies and research towards a similar treatment modality in autoimmune diseases. Thus successful in vitro and in vivo manipulations of autoantibody production by antiId antibodies were described in several animal models of autoimmunity (Hahn and Ebling, 1984; Zanetti et al., 1984; Aguis and Richmann, 1986; Koazky and Mirshahi, 1990; Roubaty et al., 1990; Nordling et al., 1991; Zou and Whitaker, 1993; Blank et al., 1994). In this chapter, we will review the idiotype-based approaches that have recently been initiated as potential interventions in autoimmune disease progression and remission.
ANTI-Id MODULATION OF AUTOANTIBODIES The possible methods by which the idiotype network might be manipulated are summarized in Table 1 and in the following sections of this chapter. Included are in vitro studies using peripheral blood lymphocytes from animal models of autoimmunity and human patients with autoimmune diseases, as well as in vivo studies in different autoimmune animals (Table 2) (Hahn and Ebling, 1984; Zanetti et al., 1984; Aguis and Richmann, 1986; Koazky and Mirshahi, 1990; Roubaty et al., 1990; Nordling et al., 1991; Zhou and Whitaker, 1993; Blank et al., 1994). In Vitro Anti-Id Modulation of Autoantibodies In vitro studies demonstrating modulation by anti-Id support the theory that anti-Id may modulate autoantibody activity in vivo.
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Table 2. Animal Models of Autoimmunity Treated by Manipulation of Autoantibody Idiotypes with Anti-Id Antibodies Reference Experimental systemic lupus erythematosus Murine lupus and lupus nephritis Autoimmune tubulointerstitial nephritis Collagen arthritis Experimental autoimmune myastenia gravis Autoimmune uveoretinitis Autoimmune thyroiditis Experimental allergic encephalomyelitis ANIMAL STUDIES Kim et al. (1987) have demonstrated that anti-DNA production by anti-DNA-secreting hybridomas can be inhibited by the addition of anti-Ids to anti-DNA. In this study, a series of anti-DNA antibody-producing hybridomas were obtained by fusing spleen cells from 6-month-old MRL/lpr autoimmune prone mice with P3X63-Ag8 myeloma cells. Rabbit anti-Id antibodies specific for several of the hybridoma proteins were prepared. It was shown that the anti-Id antibody inhibited immunoglobulin secretion by the hybridoma cells in an Id-specific manner. Inhibition of antibody production was not due to a cytotoxic effect, since the anti-Id, in fact, stimulated proliferation of the hybridoma cells. In order to assess the anti-Id network in murine experimental autoimmune encephalomyelitis (EAE), Id-bearing monoclonal antibodies (mAb) to human myelin basic protein (MBP) peptide acetyl 1-9, as well as mAb anti-Id, were developed in EAE-susceptible PL/j mice (H-2u) (Zhou and Whitaker, 1992). These mice recognize MBP residues acetyl 1-9 as an encephalitogenic determinant. Reactivities of PL/j Idbearing mAbs to MBP and to MBP peptides were identical to those of mAbs generated against the same MBP peptide in EAE-resistant BALB/C mice (H-2d), even though isotypes of the mAbs differed. By using an inhibitory ELISA and immunoblotting, it was demonstrated that one PL/j mAb anti-Id recognized a public or framework Id, whereas another PL/j mAb-anti Id was directed to a private Id more restricted to the paratopic site. Two Id-bearing PL/j mAbs shared a cross-reactive Id (IdX) on the light chain, and an interstrain IdX was present on both the heavy and light chains of mAbs raised in PL/j and BALB/C mice to the same MBP peptide. The PL/j mAb anti-Id was
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Blank et al, 1994 Hahn and Ebling, 1984 Zanetti et al., 1984 Nordling et al., 1991 Aguis and Richmann, 1986 Koazky and Mirshahi, 1990 Roubaty et al., 1990 Zou and Whitaker, 1993
capable of cross-regulating the production of Id-bearing mAbs by hybridomas across murine strains. These findings suggest that manipulation of the Id network may provide a means for modifying autoimmune demyelinating diseases of the central nervous system (Zhou and Whitaker, 1992).
STUDIES OF PERIPHERAL LYMPHOCYTES IN HUMAN AUTOIMMUNE DISEASE Abdou et al. (1981) reported that the binding of human anti-DNA antibodies to DNA could be blocked by autologous sera obtained from patients with SLE when their disease was in remission and by the F(ab')2 and Fab fragments derived from these sera. The inhibition of binding was interpreted as being due to the presence of anti-Ids in the inactive sera that reacted with the binding site of the anti-DNA antibodies present in the sera of patients when their disease was active. Additional findings extending this concept have also been presented (Reissman and Abdou, 1983). Studies of anti-DNA and anti-F(ab')2 antibodies were performed by enzyme-linked immunosorbent assay (ELISA) in 51 patients with SLE (Silvestris et al., 1984). Patients with severe, uncontrolled disease showed high levels of anti-DNA and low levels of anti-F(ab')2 antibodies. Patients with quiescent SLE usually showed high levels of anti-F(ab')2 and low levels of anti-DNA antibodies. Isolated anti-F(ab')2 antibodies from autologous SLE remission serum or from the sera of unaffected siblings of SLE patients showed maximum inhibition in test systems using affinity-purified SLE anti-DNA antibodies reacting with single-stranded DNA. In another study, it was demonstrated that specific anti-Ids can suppress the production of anti-DNA
antibodies by peripheral blood mononuclear cells from active SLE patients (Epstein et al., 1987). These authors have developed an ELISA system for measuring in vitro anti-DNA antibody production by peripheral blood mononuclear cells (PBMC) from patients with SLE. Using this technique, the PBMC from 74% of serologically active SLE patients produced levels of anti-DNA antibodies that were increased 2 SD above the mean of 18 ± 9 lU/ml for normal subjects. Furthermore, the addition of 3-1, a monoclonal antiId antibody that recognizes a cross-reactive determinant on anti-DNA antibodies, was shown to specifically inhibit anti-DNA production/« vitro. This finding supports previous work that implicates antiIds among the regulatory mechanisms that can control synthesis of anti-DNA antibodies in patients with SLE and previous studies reporting inhibition of idiotypic antibodies by the addition of anti-Id in vitro cultures of human PBMC. Zhou and Whitaker (1990) raised a mAb of the IgGl/kappa isotype against human myelin basic protein (MBP) pepfide acetyl 1-9. This mAb, termed F23, reacted with human MBP and human MBP peptides acetyl 1-9, 1-14 and 1-44, but not with MBP peptides 10-19, 80-89, or 45-89. According to the guidelines of the molecular recognition theory, a complementary peptide to human MBP peptide 1-9 was synthesized and used to raise murine mAb with anti-Id activity. Two mAb anti-Id, F25F7 and F25C8, both of the IgM/kappa isotype, were selected for further study. The cross-reactive anti-Id suppressed antibody secretion of Id-producing hybridoma cells in an Idspecific manner, and kinetic studies suggest an intracellular mechanism for the suppression. These cross-reactive Id among antibodies to different MBP peptides imply that the same V region genes of kappa L chains are involved in the selection of antibodies to an autoantigen, like MBP, and may play a role in the modulation of immune responses against MBP in certain inflammatory demyelinating diseases (Zhou and Whitaker, 1990). In another study (Fong et al., 1984), rabbit anti-Id antibodies to human rheumatoid factor (RF) autoantibodies were isolated by affinity chromatography on rabbit anti-human IgG Fc sepharose 4B. The antiId antibodies bore the "internal image" of the antigen, human IgG. They reacted specifically with multiple human monoclonal and polyclonal IgM-RF, independent of any particular light or heavy chain amino acid sequence. The anti-Ids did not react with IgM or IgG proteins lacking RF activity. The experi-
ments in this study (Fong et al., 1984) determined the potential of the "internal image" antibodies to modulate in vitro lymphocyte fiinctions. The addition of anti-Id antibody to peripheral blood mononuclear cell cultures from patients with rheumatoid arthritis elicited lymphocyte proliferation, but not RF synthesis. The antibody did not induce the proliferation of lymphocytes from a normal individual. Moreover, the anti-Id specifically suppressed IgM-RF secretory responses when preincubated with B cells before co-culture with autologous pokeweed mitogenactivated T cells. This study showed that the anti-Id antibodies with the "internal image" of antigen are capable of interacting with B-cell receptors in an antigen-restricted manner, and posses specific immunomodulatory properties (Fong et al., 1984). Takeuchi et al. (1985), further studied the effect of anti-Id antibody on the in vitro production of RF in rheumatoid arthritis patients with cross-reactive idiotypic determinants. Anti-Id antibodies were developed against monoclonal RF (Kam-RF) by a cell fusion procedure. These antibodies were idiotypespecific. The anti-Id antibody strongly suppressed the in vitro production of RF by lymphocytes from unrelated rheumatoid arthritis patients with cross-reactive idiotypes. These results indicate that anti-Id antibody may influence the regulation of RF production in patients with rheumatoid arthritis (Takeuchi et al., 1985). Kajima et al. (1986) have reported on the suppression of in vitro human anti-thyroglobulin antibody secretion in Epstein-Barr virus transformed B lymphocytes by private and cross-reactive anti-Id antibodies. It was suggested that interactions between idiotype and anti-Id may play a role in the immune regulation of human chronic thyroiditis (Kajima et al., 1986). Anti-Ids as Specific Carriers of Toxins Another method by which anti-Ids can be employed in the treatment of autoimmune diseases is as specific carriers of toxins. Sasaki et al. (1986) have developed a new way of using anti-Id antibodies by conjugating them with cytotoxic agent, NCS (Neocarzinostatin). The conjugates killed Id-positive EBV-transformed B-cell clones, resulting in the suppression of anti-DNA production. Later on, the same group demonstrated that this method is capable of manipulating the human anti-DNA system through the specific elimination of anti-DNA Id-positive cells from lymphocytes in the peripheral blood (Sasaki et al., 1989).
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Following these in vitro studies (Sasaki et al., 1986; 1989), Harata et al. (1990) demonstrated a successful treatment of NZBAVF, mice disease by using anti-Idconjugated NCS. In this study (Harata et al., 1990), in vivo administration of anti-Id antibodies conjugated with NCS brought about an improvement in the survival rate of female NZBAV F^ mice. It also caused a retardation of development of lupus nephritis and decreased the numbers of anti-DNA-reproducing cells. The suppression of anti-DNA antibody synthesis was specific and Id-mediated. These results indicate that the use of a limited number of anti-Id antibodies in combination with a cytotoxic agent may be applicable therapeutically to autoimmune diseases. Saporin is one of the most widely used toxin compounds for immunotoxin preparation. We have recently demonstrated the suppression of experimental systemic lupus erythematosus (SLE) with specific anti-Id antibody-saporin conjugate (Blank et al., 1994). The antiId treatment was specifically shown to reduce anti-DNA antibodies by a specific hybridoma cell line (Blank et al., 1994). The immunotoxin (saporin) had a significantly superior result compared with the anti-Id itself Yet, although impressive, the effect of the saporin in reducing anti-DNA antibody production and abrogation of SLE manifestations was not better than the antiId alone (Blank et al., 1994). (For More details on anti-Id treatment in this model, see the next section). Valderrama et al. (1988) have treated experimental myasthenia with autologous idiotypes linked to muramyl dipeptide. Rabbits were injected with purified acetylcholine receptor (AchR) from Torpedo, California. Polyclonal affinity purified anti-AchR antibodies (Ids) were coupled covalently to muramyl dipeptide and injected back into the same (autologous) rabbits from which the Ids were obtained. Treated animals developed anti-Ids that bound to the F(ab')2 fragments of the Ids as demonstrated by ELISA and that also blocked binding of Ids to AchR in a radioimmunoassay. Treated animals showed a protective effect compared to control animals when challenged with a second injecfion of AchR. No apparent toxicity from the treatment was noted (Valderrama et al., 1988). In Vivo Modulation of the Idiotype Network Subsequent to the encouraging results of the experiments involving in vitro modulation of autoantibody idiotypes by anti-Id treatment, in vivo studies were undertaken. These studies were conducted in animals
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and included: 1) passive administration of anti-Id reagents to experimental animals, and 2) immunization of mice against their own pathogenic Id. Passive Administration Of Anti-Id To Autoimmune Animals In mouse models of lupus, resuhs have been conflicting, probably reflecting different influences of various anti-Ids on autoimmune mechanisms. In B/W mice, administration of an anti-Id directed against a major CRI on anti-DNA antibodies resulted in the disappearance of anti-DNA antibodies bearing the target idiotype and in the prolongation of survival due to a delay in the onset of nephritis (Hahn and Ebling, 1984). These researchers have identified three dominating Id in NZB/W F, mice by the time they develop nephritis at 30 weeks of age: IdX, Id GNI and Id GN2 comprise about 85% of their total serum Ig. While Id GNI and GN2 comprise approximately 50% of the Id deposited in the glomeruli, IdX is detectable on less than 5% of glomerular Ig (Hahn and Ebling, 1987). While a monoclonal antibody to Id GNI was administered repeatedly to NZB/W F, female mice beginning at 20 weeks of age, the levels of all three Id were significantly suppressed for 10 weeks, during which time disease developed in the controls, but not in the treated mice. Although IdX continued to be suppressed, levels of Id GNI escaped suppression and rose to levels similar to those in the control mice and fatal nephritis rapidly ensured. The Ig eluted from the glomeruli of these mice were composed entirely of Id GN2 Ig. This treatment with anti-Id GNI or with anti-IdX (Hahn and Ebling, 1987) prolonged the lives of the mice by 10 weeks. In contrast to the data described by Hahn and Ebling (1984), administrating an anti-Id directed against Id-130 (a dominant idiotype of MRL anti-DNA antibodies) to MRL mice, augmented the production of the Id-130 idiotype and anti-DNA antibodies (Teitelbaum et al., 1984). However, Mahana et al. (1987) were able to suppress anti-DNA production in MRL mice by the passive transfer of anti-Id D23 (an idiotype of a monoclonal polyspecific natural autoantibody reacting mainly with ds-DNA and ss-DNA). These conflicting results can be resolved if we assume that various anti-Ids regulate idiotype-bearing autoantibodies in different ways, some acting to suppress idiotype production and others augmenting idiotype expression.
The importance of the idiotypic network is represented in experimental SLE induced by active immunization of naive mice with an anti-DNA idiotype (Ab 1) emulsified in adjuvant. The mice after 4 months of incubation generate Ab3 having anti-DNA activity. In addition, the mice develop other serological markers for SLE associated with clinical and histopathological manifestations characteristic of the disease (Blank et al., 1988; 1990; Mendlovic et al., 1988). To confirm further the etiological role of the idiotype in the experimental model, the mice were treated with specific anti-Id antibodies (anti-Id) which were also conjugated to a toxin-saporin (Immunotoxin (IT)) (Blank et al., 1994). Pretreatment of hybridoma cell line producing the anti-anti-Id (anti-DNA = (Ab3)) for 48 h with the anti-Id MoAb (Ab2) reduced the production of anti-DNA by 58%, while pretreatment with the IT resulted in 86% decrease in antiDNA secretion (saporin alone had only 12% effect). The anti-Id MoAb had no effect on the production of immunoglobulin by an unrelated cell line. In vivo treatment of mice with experimental SLE led to a significant decrease in titers of serum autoantibodies, with diminished clinical manifestations. The results were more remarkable when the IT was employed. These successive effects were specific, since an antiId treatment of experimental anti-phospholipid syndrome was of no avail. The anti-Id effect was mediated via a reduction in specific anti-DNA antibody-forming cells, and lasted only while anti-Id injections were given. Discontinuation of the anti-Id injection was followed by a rise in titres of anti-DNA antibodies. No immunological escape of new anti-DNA Ids was noted. Our results point to the importance of pathogenic idiotypes in SLE and to the specific potential of implementing anti-Id therapy, enhanced by the conjugation of the anti-Id to an immunotoxin, in particular one with low spontaneous toxicity (Blank et al., 1994). The F1 progeny of the cross between SWR and NZB mice (SNFl) develop severe immune complex glomerulonephritis. An idiotypically related family of nephritic antibodies (IdLNFl) has been shown to be important in the pathogenesis of autoimmune glomerulonephritis in these mice. Uner et al. (1994) have injected the SNFl mice with rabbit anti-IdLNFl antibodies, which has resulted in significant suppression of IdLNFl + Ig (G + M) and IgG production. The decrease appeared to be mediated via significant decreases in the percentage of IdLNFl-expressing B cells and CD4 + IdLNFl-specific T cells in the treated SNFl mice compared to the controls (Nordling et al.,
1992). This was accompanied by a significant increase in survival with delayed onset of glomerulonephritis. Surprisingly, there was no difference in the incidence of anti-DNA antibody production between the treated and control SNFl mice. Nordling et al. (1992) have recently described a spontaneously occurring inflammatory and erosive joint disease in male DBA/1 mice. These mice have an increased serum antibody level to collagen II in a fraction of the male DBA/1 mice. Administration of antibodies with an anti-Id activity to anti-collagen II antibodies and with an affinity for determinants on isolated synergeneic IgG Fc but not on intact IgG, was shown to interfere with the development of the spontaneous arthritis. In another study (Tarutani, 1993), collagen-induced arthritis was shown to be suppressed with monoclonal anti-Id antibody. Anti-Id treatment has been tried, as well, in autoimmune tubulointerstitial nephritis (TIN) in Brown Norway rat (Zanetti et al., 1984). In vivo injection of anti-TBM (tubular basement membrane) Id before immunization with TBM, resulted in a significant selective suppression of antibodies to the autologous collagenase-solubilized TBM moiety and a corresponding decrease of TIN (Zanetti et al., 1984). Agius and Richman (1986) have used isogeneic anti-Id monoclonal antibodies to modify experimental autoimmune myasthenia gravis (EAMG) in Lewis rats. Pretreatment with anti-Id not only perturbed this Id—anti-Id network, but also suppressed the overall polyclonal anti-AchR response with resultant protection of actively immunized animal from EAMG (Aguis and Richmann, 1986). Other studies have confirmed the beneficial effect of anti-Id antibodies on EAMG (Blair et al., 1987; Sunblad et al., 1989; Verschuuren et al., 1991). Experimental autoimmune uveoretinitis (EAU) is induced in rats with injection of S-antigen (S-Ag) in complete Freund's adjuvant (CFA) (de Kozak, 1990). de Kozak has shown that injection of rats with the mouse anti-SAg mAb S2D2 either simultaneously with or before S-Ag challenge led to an anti-Id response and to inhibition of EAU. Syngeneic Immunization With Idiotypes Another method for treating animals is by active immunization with the idiotype instead of passive administration of the anti-idiotype. In NZBAV Fl mice, it was found that injection of a monoclonal anti-DNA Id resulted in a decrease of autoantibody levels and a partial improvement of the disease (Hahn and Ebling,
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1983). The effect was transient, however, and antiDNA antibodies appeared which did not exhibit the injected idiotype. In a different experiment, mice were inoculated with syngeneic anti-DNA IgG together with muramyl dipeptide. It was found that anti-DNA antibody levels were suppressed and that an anti-Id specific for the injected IgG appeared (Zouali et al., 1985). In another study, the immunization of BAV mice with the PME 77 anti-DNA monoclonal antibody (a syngeneic antibody bearing the idiotype present in most B/W sera) was investigated (Jacob and Iron, 1984). The PME 77 mAb immunization regimen induced the production of auto-anti-Id antibodies and abrogated the expression of the PME 77 idiotype in B/W-treated mice. In contrast, untreated mice and control B/W mice receiving NZB polyclonal IgG2b which lacked detectable DNA binding capacity, expressed PME 77 idiotypes. These results demonstrate that the expression of idiotypes borne by autoantibodies may be modified through the induction of auto-anti-Id antibodies. Treatment with anti-AchR idiotypic antibodies resulted in improvement of modulation of the immune response of mice to acetylcholine receptor (Souroujon et al, 1985). In vivo Anti-Id Therapy In Human Autoimmune Diseases Anti-Id therapy has not been tried in human autoimmune diseases directly. One study used the approach of passage of plasma over an anti-Id column which removes antibodies bearing the common idiotype (Macleod et al., 1988). In this study, an anti-3I Id column was used to remove anti-ds DNA antibodies bearing the 31 Id from patients with SLE. There were no significant side effects. The recent development of "humanized" murine or rat monoclonal antibodies opens the way for direct injection of Id-bearing or antiId antibodies into patients. Much attention has been given in recent years to the possibility that the immunomodulating effects seen in autoimmune diseases treated with IVIG (intravenous immunoglobulins) may be applied by anti-Id antibodies present in the gammaglobulin preparations. Indeed, recent studies strengthen the likelihood that anti-Id antibodies present in IVIG preparations may control autoimmune reactions. Patients who developed antibodies to their own circulating factor VIII can bleed severely. IVIG can block the secretion of such
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Table 3. Specific Anti-Ids Against Disease Related Autoantibodies Found In IVIG Anti-DNA Anti-thyroglobulin Anti peripheral nerve Anti-factor VIII: C Anti-intrinsic factor Anti-membrane antigen of erythroblasts Anti-platelet gpIIb/IIIa Anti-neutrophil cytoplasmic antigen antibodies and this property has been attributed to the presence of naturally occurring anti-Id antibody to the antibody against factor VIII (Sultan et al., 1984; Timmerman et al., 1985). Subsequently IVIG, prepared from large pools of plasma from normal donors, were found to contain specific anti-Ids against a number of disease-related autoantibodies (see Table 3), including antibodies to DNA, thyroglobulin, gastric intrinsic factor (Rossi and Kazatchkine, 1989; Dietrich and Kazatchkine, 1990), peripheral nerve (Van Doom et al., 1990), neutrophil cytoplasmic antigens (Rossi et al., 1991), platelet gpIIb/IIIa (Berchtold et al., 1989), and membrane antigen of erythroblasts (McGurie et al., 1987). Dietrich and Kazatchkine (Dietrich and Kazatchkine, 1990) found that anti-Ids in IVIG recognize a cross-reactive idiotype on human anti-thyroglobulin (TG) autoantibodies that was defined by heterologous anti-Id antibodies, termed anti-T44 antibodies. The idiotype was expressed on anti-thyroglobulin IgG of eight out of nine patients with Hashimoto's disease but on no IgG of five healthy individuals who were tested. Anti-thyroglobulin autoantibodies expressing the T44 idiotype exhibited a restricted epitopic specificity against human thyroglobulin, thus, IVIG contain anti-Id antibodies directed against an immunodominant cross-reactive idiotype of human anti-TG autoantibodies. Evans and Abdou (1993) have demonstrated that anti-Id antibody and its (ab')2 fragments prepared from pooled normal human IgG had a partial inhibitory effect on the spontaneous in vitro secretion of anti-DNA antibodies from blood mononuclear cells of lupus patients. The inhibitory effect was specific for anti-DNA secretion as the anti-Id failed to inhibit the spontaneous secretion of anti-tetanus toxoid, in the same culture supematants (Evans and Abdou, 1993).
Several lines of evidence demonstrate the presence in IVIG of anti-Ids against autoantibodies. These include: 1. F(ab')2 fragments from IVIG inhibit the biding of autoantibodies to their autoantigens (Sultan and Kazatchkine, 1984; Rossi et al., 1988; Van Doom et al., 1990); 2. F(ab')2 fragments with autoantibody activity are specifically retained on affinity columns of sepharose-bound F(ab \ fragments from IVIG (Sultan et al., 1987; Rossi et al., 1988; 1991); 3. IVIG contain no antibody specificities against the most common allotypes expressed in the F(ab')2 region of human IgG (Rossi et al., 1988); 4. The binding of IVIG to affmity-purified autoantibodies is specifically displaced by F(ab \ fragments from heterologous polyclonal anti-autoantibody anti-Ids (Rossi and Kazatchkine, 1989). The high number of donors contributing to IVIG endows the preparation with anti-Id specificities that may not necessarily be detectable in plasma from single healthy individuals. The IVIG may be efficient in some autoimmune diseases by providing a source of anti-Ids with a wide range of specificities brought as interconnected antibody species that may compensate for altered connectivity of the immune network of patients with autoimmune diseases (Rossi and Kazatchkine, 1989). Immunomodulation Of Experimental Animal Models Of Autoimmunity With Idiotype-Specific T Cells And Antibodies That bind To T-Cell Receptor (TCR) Still another approach introduced by Shoenfeld and Mozes (1990) utilizes T-suppressor cells specific to pathogenic idiotypes. Several papers have reported decreased numbers and activity of T cells in several mice models for SLE as well as in other animal models for autoimmune conditions as summarized by Tomer and Shoenfeld (1989). Similarly decreased numbers and activity of Ts cells in humans with SLE and other autoimmune diseases have regularly been reported. If the production of autoantibodies in SLE and other autoimmune states is related to down-regulation of Ts, the reconstitution of Ts cell numbers and activity, and especially the Ts specific to the harmful autoantibody in question, may lead to amelioration of disease manifestations. In fact, several studies have suggested this very possibility (Pachner and Kantor, 1984; Smith et al., 1987).
In a recent experiment, Ts cells (CD8+) specific to the pathogenic idiotype 16/6 that were MHC-restricted in their function were generated in vitro. The suppressor cells specific for the pathogenic idiotype 16/6 were generated from populations of normal T cells exposed to silica beads coated with SA-1 (16/6 Id+) mAb in vitro (Mendlovic et al., 1988). Treatment of B ALB/C mice in which SLE was induced experimentally (Blank et al., 1991) with the Id-specific Ts cells, resulted in a decline in the titers of autoantibodies in the sera and in clinical manifestations (increased ESR, low WBC count, and proteinuria). Furthermore, no immunoglobulin deposits were found in the mesangium of the kidneys in contrast to kidneys of the 16/6 Id-immunized mice treated with control IgM specific Ts cells. It should be noted that this treatment failed once the disease was well established (5 months after immunization with 16/6). These results emphasize the importance of the role played by pathogenic idiotypes in murine SLE and the role Ts cells may play in induction as well as in the treatment of autoimmune conditions. In the same vein, strategies that might specifically block or inactivate helper T cells necessary for the sustained production of anti-DNA pathogenic antibodies may provide a specific suppression of disease progression. As discussed earlier, Hahn and her colleagues have raised CD4+ T-cell clones specific for Id GN2. Their program includes inoculating low doses of anti-Id GN2 to NZB/W Fl mice, harvesting T cells by draining lymph nodes, and obtaining T cells from the spleens of lupus mice with active nephritis. Stimulating these clones with rat concanavalin A supernatant, DNA antigen soluble Id GN2, or hybridoma B cells expressing Id GN2 on their surface, yields T-cell clones which significantly increase the production of Id GN2 IgG anti-DNA in a culture using B cells from the spleens of 16-week-old lupus mice. One of these clones, isolated from the spleens of nephritic NZB/W Fl mice (termed TH 27.6), has been characterized (Ando et al., 1987). It increases the synthesis of Id GN2 anti-DNA by NZB/W B cells eightfold, whereas it augmented total IgG only twofold. It is an autoreactive clone of the TH2 types: it can be activated by H2'^ without addition of DNA, and secretes B-cell rather than T-cell growth factors, including IL-4, IL-5 and IL-6, but not IL-2. These studies may pave the way for new directions in disease management.
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Roubaty et al. (1990) have described the protective immunity against experimental autoimmune thyroiditis induced exclusively by a thyroglobulin (Tg)-specific cytotoxic T-cell clone and showed that this down-regulation occurred through the generation of anti-Id antibodies (Ab2 Beta) which recognized the paratope of anti-Tg mAb (Abl) specific to the pathogenic epitope of the Tg molecule (Roubaty et al., 1990). Protection from experimental allergic encephalomyelitis (in Lewis rats) was conferred by a monoclonal antibody directed against a shared idiotype on rat T-cell receptors specific for myelin basic protein (MBP) (Owhashi and Heber Katz, 1988). Finally, it was demonstrated by Rohowsky et al. (1994) that T-cell clones specific for MBP have the ability to induce proliferative responses in resting T lymphocytes in the autologous mixed lymphocyte culture (AMLC). Modulation of the T-cell receptor from the surface of the clones decreased their AMLC stimulatory ability, indicating that idiotype-like determinants on the T-cell receptor of autoantigen T-cell clones are capable of triggering anti-Id T-cell responses (Rohowasky-Kochan et al., 1994).
HOW CAN THE MANIPULATION OF THE IDIOTYPE NETWORK AFFECT IDIOTYPE EXPRESSION The mechanism of suppression of the idiotype antibody response by the anti-Id antibody is unclear. Two possibilities exist and they entail clonal deletion of B cells and production of suppressor T cells (Kohler et al., 1974; Eichmann, 1975). Simple binding of idiotypes by the anti-Id antibody is probably inadequate to explain the mechanism of suppression; the small amount of anti-Id necessary for suppression in the above mentioned experiments was greatly exceeded by the amounts of idiotypic antibody produced by immunized control animals (Hart et al., 1972). The down-regulation of idiotype expression may be caused by the blocking of immunoglobulin synthesis or by the formation of complexes. For example, it has been suggested that the decrease in the binding affinity of an antibody response is related to the appearance of an auto-anti-Id (Zouali and Diamond, 1990). It is not yet clear if the anti-Id acts directly on B cells to down-regulate production of anti-DNA antibodies or if it acts through an idiotypic network involving T cells (Zouali and Diamond, 1990). Indeed, besides inducing anti-Id Ab, treatment of
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mice anti-DNA IgG and MDP could also have induced either a depression of Id-specific T-helper cells or a stimulation of Id-bearing T-suppressor cells (Zouali et al., 1985). Support for this view comes from the recent demonstration that administration of an antiId Ab to anti-DNA suppresses the pathogenic Ab to DNA NZBAV mice (Hahn and Ebling, 1984). Future experiments will no doubt add to the better understanding of the mechanisms involved in idiotype expression by manipulation of the idiotype network. Therapeutic Problems In Modulation Of Idiotypes of Autoantibodies It is now understood that the manipulation of autoantibody idiotypes might be utilized in the treatment of autoimmune diseases. Indeed, encouraging results have been reported in lupus-prone mice models. However, the effect of anti-Id antibodies appears to be complicated in the case of in vivo administration in autoimmune mice (Hahn and Ebling, 1984; Teitelb a u m e t a l , 1984). There are many factors influencing the biological effectiveness of anti-Id treatment (Table 4). Id manipulation can result in down- or up-regulation of the immune response depending on the time-window of the disease, the age of the animals, the isotype, the affinity, and the amount of the Id or the anti-Id injected. The biological effectiveness of the treatment also depends on the functional properties of the antiId, i.e., whether it mimics the configuration of the antigenic motifs, or whether it interacts with regulatory Id that ensures connectivity between various Id families (Brown et al., 1979; Zouali et al., 1985; Sasaki et al., 1986; Zouali and Diamond, 1990). Some of the problems observed in treatment with Id manipulation are summarized in Table 5. Although some studies have shown that anti-Id administration can suppress the production of anti-DNA antibodies and nephritis. Table 4. Factors Influencing the Biological Effectiveness of Treatment with Id Modulation Isotype of Id anti-Id injection Affinity of Id or anti-Id injected Amount of the Id or anti-Id injected Functional properties of the anti-Id Time-window of the disease Age of the animals Method of manipulation: passive transfer, immunization
Table 5. Modulation of Autoantibody Idiotypes with Anti-Id Antibodies: Therapeutic Problems • No effect of treatment • Partial effect of treatment • Transient reduction of autoantibodies • Necessity for repeated administration of anti-Id • Change in the dominant Id on pathogenic autoantibody: escape from suppression • Inadequacy of therapy while using anti-Id alone: treatment with anti-Id cytotoxic agent or "cocktail" of anti-Ids • Unpredictability of treatment with Id manipulation: up- rather than down-regulation of immune response the effect was transient and anti-DNA antibodies appeared which did not bear the injected idiotype (Hahn and Ebling, 1983). Moreover, in other studies, treatment of mice with anti-Id anti-DNA antibodies was found to have no effect (Teitelbaum et al., 1984). Yet another problem is the escape from suppression of Id production by anti-Id (Hahn and Ebling, 1984). Therefore, although administration of anti-Id was effective in reducing an undesirable antibody response after the target Id was present on circulating antibodies, the benefits were limited probably by Id "switch" or by increased synthesis of pathogenic antibodies bearing a minor Id. Such a change may be prevented by administration of polyclonal or mixed monoclonal anti-Id reagents. More distressing, however, is the fact that anti-Id reagents can augment rather than suppress the secretion of idiotypic antibodies (Teitelbaum et al., 1984). These conflicting results can be resolved if we assume that various anti-Ids regulate idiotype-bearing autoantibodies in different ways: some acting to suppress idiotype production and others augmenting idiotype expression.
REFERENCES Abdou NI, Wall H, Lindsley HB, Halsey JF, Suzuki T Network theory in autoimmunity. In vitro suppression of serum anti-DNA antibody binding to DNA by antiidiotypic antibody in systemic lupus erythematosus. J Clin Invest 1981;67:1297-1304. Aguis MA, Richmann DP. Suppression of development of experimental autoimmune myasthenia gravis with isogeneic monoclonal anti idiotypic antibody. J Immunol 1986;137:2195-2198. Ando DG, Scroarz LL, Hahn BH. Mechanisms of T and B
It is clear that modulation of the autoantibodies' idiotype-anti-idiotype (Id-anti-Id) network will perturb other Id-anti-Id systems through the connections and cross-reactivities of the idiotypes and anti-Ids involved. Removal of specific idiotypes will eliminate not only those borne by specific autoantibodies but those on antibodies directed against other auto-antigens and bacteria. This might have unpredictable consequences on the body's ability to fight infection.
CONCLUSIONS The central goal in the therapy of autoimmune diseases is to develop potent tools able to exert specific control of the immune response to self antigen. Anti-Id treatment may provide such specific immunomodulation because the relevance of the idiotypic network in autoimmunity is well documented. Indeed, encouraging results have been reported in experimental autoimmune diseases. There are, however, some problems in this treatment, such as nonresponse or transient, partial response to anti-Id manipulation. Moreover, unpredictable consequences as up-regulation instead of down-regulation of production of autoantibodies bearing pathogenic idiotypes have been observed. In order to devise anti-Id therapy to autoimmune diseases, it is crucial to define the panel of pathogenic idiotypes of autoantibodies involved in autoimmune disease. More animal experiments may highlight the conditions necessary to induce suppression rather than enhancement of antibody production. Through the use of in vitro immunization methods, human anti-Id antibodies may ultimately be produced obviating the need to administer animal antibodies. Thus, despite all the present obstacles, treatment with anti-Id antibodies may well be practical in the not too distant future.
cell collaboration in the in vitro production of anti-DNA antibody in the NZB/NZW F, murine SLE model. J Immunol 1987;138:3185-3190. Berchtold P, Dale GL, Tani P, et al. Inhibition of autoantibody binding to platelet glycoprotein Ilb/IIIa by antiidiotypic antibodies in intravenous gammaglobulin. Blood 1989;74:2414-2417. Blair DA, Mihovilovic M, Agius MA, Fairclough RH, Richman DP. Human x human hybridomas from patients with myasthenia gravis: possible tools for idiotypic therapy for myasthenia. Ann NY Acad Sci 1987;505:155167.
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