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A new HLA-D specificity was found in the Japanese population in two different laboratories. Japanese cell YT, found at Stanford, California, was A9,BW22J,CW1 and cell Wa, found at Sapporo, Japan, was A9,BW22J homozygous. They were shown to be HLA-D identical to the homozygous Japanese cell AH which submitted to the VIth International Histocompatibility Testing Workshop (Workshop number 2-001). This specificity was common in the Japanese (gf = 0.089) but completely absent from 62 Caucasians tested. Strong association of this specificity with HLA-BW22J was demonstrated.

With the goal of identifying changes in gene expression in CD4 + T cells during the development of diabetes in the nonobese diabetic (NOD) mouse, we used DNA microarrays to analyze gene expression in CD4 + T cells from the pancreatic draining lymph nodes of NOD/BDC 2.5 T cell receptor transgenic and WT NOD mice at different ages. At 4 and 6 weeks of age, we found up-regulation of a number of genes that are known to be induced by IFN-α. IFN-α levels and IFN-α–producing plasmacytoid dendritic cells were increased in the PLNs of 3- to 4-week-old NOD mice. Moreover, blockade of IFN-α receptor 1 in NOD mice by a neutralizing antibody at 2–3 weeks of age significantly delayed the onset and decreased the incidence of type 1 diabetes, increased the relative number of immature dendritic cells in the PLNs, and enhanced the ability of spleen CD4 + T cells to produce IL-4 and IL-10. These findings demonstrate that IFN-α in the PLNs is an essential initiator in the pathogenesis of type 1 diabetes in NOD mice.

Before the onset of autoimmune destruction, type 1 diabetic patients and an animal model, the nonobese diabetic (NOD) mouse, show morphological and functional abnormalities in target organs, which may act as inciting events for leukocyte infiltration. To better understand these abnormalities, but without the complications associated with lymphocytic infiltrates, we examined genes expressed in autoimmune target tissues of NOD/severe combined immunodeficient (scid) mice and of autoimmune-resistant C57BL/6/scid mice. Our results suggest that the NOD genetic background may predispose them to diabetic complications, including insulin resistance in the absence of high circulating glucose levels and without autoimmune destruction of their β cells. Several of these genes lie within known type 1 and 2 diabetes loci. These data suggest that the NOD mouse may be a good candidate to study an interface between type 1 and type 2 diabetes.

This presentation is an overview of mechanisms for developing and maintaining self-tolerance in mammalian organisms. Because this meeting is focused on type 1 diabetes and its mechanisms, the discussion deals primarily with mechanisms of T-cell tolerance, since type 1 diabetes in both effector and initiator phases is primarily a T-cell–mediated autoimmune disease. Emphasis is placed on more recently discovered mechanisms of maintaining self-tolerance (autoimmune regulator [AIRE]) and a new defect in T-cell negative selection. The emerging picture is that of a polygenic disease with various combinations of different alleles of many genes with important roles in the normal immune response or normal immune responses.

To improve the feasibility of in vivo monitoring of autoreactive T cells in the diabetogenic process, we generated T1 and T2 doubly transgenic non-obese diabetic (NOD) mice in which transgenic human CD90 (hCD90) is simultaneously expressed on IFN-gamma-producing cells or murine CD90.1 (mCD90.1) is expressed on IL-4-producing cells. These transgenic NOD mice develop diabetes with the same kinetics and incidence as wild type NOD mice, permitting the physiological characterization of CD4(+)hCD90(+) cells, which represent T(H)1 cells in lymphoid organs and at the site of insulitis. CD4(+)hCD90(+) cells had a higher capacity to secret IFN-gamma than CD4(+)hCD90(-) cells in an autoantigen-specific manner. Transgenic mice treated with GAD65 plasmid were protected from autoimmune diabetes, and had a lower number of CD4(+)hCD90(+) cells, confirming the pathogenic role of CD4(+)hCD90(+) cells in autoimmune diabetes. To further investigate the effect of IL-12 on the development of T(H)1 cells in autoimmune diabetes, we crossed these doubly transgenic mice to IL-12p35-deficient NOD mice. Despite severe disturbance of diabetes in p35(-/-) mice, the frequency of T(H)1 cells in these mice was slightly lower than in wild type mice. These data support the pathological role of IL-12 in autoimmune diabetes and suggest the existence an IL-12-independent pathway of T(H)1 development.

TNF-α has been linked to the development of type 1 diabetes (T1D). We previously reported that neonatal treatment of nonobese diabetic (NOD) mice with TNF-α accelerated the onset of T1D, whereas TNF-α blockade in the same time period resulted in a complete absence of diabetes. The mechanisms by which TNF-α modulates development of T1D in NOD mice remain unclear. Here we tested the effects of TNF-α on the maturation of dendritic cells (DCs) in the NOD mouse. We found that neonatal treatment with TNF-α caused an increase in expression of maturation markers on CD11c+CD11b+DC subpopulations, whereas treatment with anti-TNF-α resulted in a decrease in expression of maturation markers in the CD11c+CD11b+subset. Moreover, neonatal treatment with TNF-α resulted in skewed development of a CD8α+CD11b-CD11c+DC subset such that TNF-α decreases the CD8α+CD11c+DC subset, increases the CD11c+CD11b+subset, and causes an increase in the expression of CD40 and CD54 on mature DCs capable of inducing immunity. Anti-TNF-α-treated mice had an increase in the CD8α+CD11c+DCs. Notably, adoptively transferred naïve CD4+T cells from BDC2.5 T cell receptor transgenic mice proliferated in the pancreatic lymph nodes in TNF-α-treated NOD mice but not in anti-TNF-α-treated mice. Finally, we show that anti-TNF-α-treated mice showed immunological tolerance to islet cell proteins. We conclude that TNF-α plays an important role in the initiation of T1D in the NOD mouse by regulating the maturation of DCs and, thus, the activation of islet-specific pancreatic lymph node T cells.

CD4+CD25+Foxp3+ regulatory T cells (Treg) are critical for controlling autoimmunity. Evidence suggests that Treg development, peripheral maintenance, and suppressive function are dependent on Ag specificity. However, there is little direct evidence that the Treg responsible for controlling autoimmunity in NOD mice or other natural settings are Ag specific. In fact, some investigators have argued that polyclonal Ag-nonspecific Treg are efficient regulators of immunity. Thus, the goal of this study was to identify, expand, and characterize islet Ag-specific Treg in NOD mice. Ag-specific Treg from NOD mice were efficiently expanded in vitro using IL-2 and beads coated with recombinant islet peptide mimic-MHC class II and anti-CD28 mAb. The expanded Ag-specific Treg expressed prototypic surface markers and cytokines. Although activated in an Ag-specific fashion, the expanded Treg were capable of bystander suppression both in vitro and in vivo. Importantly, the islet peptide mimic-specific Treg were more efficient than polyclonal Treg in suppressing autoimmune diabetes. These results provide a direct demonstration of the presence of autoantigen-specific Treg in the natural setting that can be applied as therapeutics for organ-specific autoimmunity.

We previously described the generation of non-obese diabetic (NOD) mice expressing a transgenic T cell receptor (TCR) specific for peptide epitope 286-300 of the diabetes related self antigen, glutamic acid decarboxylase (GAD)65 in the context of I-A(g7) class II MHC, that are paradoxically protected from diabetes. In this report, we examine the atypical CD8+ cells in these mice. Unlike typical class II restricted TCR transgenic mice, GAD286 mice have normal numbers of CD8+ cells, half of which express high levels of the transgenic TCR. These MHC mismatched CD8+ cells persist in the periphery and proliferate to GAD286-300 peptide in vitro and in vivo in a class II restricted fashion. Interestingly, the CD8+ tetramer(-) T cells that are expressing endogenous TCR can delay diabetes induction in a transfer model, as we previously showed for CD4+ tetramer+ T cells in these mice. The MHC mismatched CD8+ cells appear to be positively selected in an atypical fashion, in that they do not upregulate CD69 or reexpress CD44, and they escape negative selection. We find that production of these CD8+ cells is not dependent on NOD thymus or high affinity of the TCR, but is dependent on the atypical TCR transgenic thymic environment.

Glutamic acid decarboxylase (GAD) 65 is one of the major pancreatic antigens targeted by self-reactive T cells in type I diabetes mellitus. T cells specific for GAD65 are among the first to enter inflamed islets and may be important for the initiation of autoimmune diabetes. However, we previously reported that nonobese diabetic (NOD) mice transgenic for a T cell antigen receptor (TCR) specific for one of the immunodominant epitopes of GAD65, peptide 286-300 (G286), are protected from insulitis and diabetes. To examine whether other GAD65-reactive T cells share this phenotype, we have generated TCR transgenic NOD mice for a second immunodominant epitope of GAD65, peptide 206-220 (G206). As in G286 mice, G206 mice do not develop islet inflammation or diabetes. When adoptively transferred along with diabetogenic T cells, activated G206 T cells significantly delayed the onset of diabetes in NOD.scidrecipients. Both G206 and G286 T cells produce immunoregulatory cytokines IFN-γ and IL-10 at low levels when activated by cognate antigens. These data suggest that GAD65-specific T cells may play a protective role in diabetes pathogenesis by regulating pathogenic T cell responses. A better understanding of the functions of autoreactive T cells in type I diabetes will be necessary for choosing desirable targets for immunotherapy.

The low number of CD4+ CD25+ regulatory T cells (Tregs), their anergic phenotype, and diverse antigen specificity present major challenges to harnessing this potent tolerogenic population to treat autoimmunity and transplant rejection. In this study, we describe a robust method to expand antigen-specific Tregs from autoimmune-prone nonobese diabetic mice. Purified CD4+ CD25+ Tregs were expanded up to 200-fold in less than 2 wk in vitro using a combination of anti-CD3, anti-CD28, and interleukin 2. The expanded Tregs express a classical cell surface phenotype and function both in vitro and in vivo to suppress effector T cell functions. Most significantly, small numbers of antigen-specific Tregs can reverse diabetes after disease onset, suggesting a novel approach to cellular immunotherapy for autoimmunity.

Using BW 5147 T cell hybridomas isolated by fusion with spleen and lymph node cells from NOD female mice, two T cell receptor transgenic NOD mouse lines were produced. Both TCR transgenics respond to their cognate peptide/MHC (GAD65 206-220 and 286-300) and produce IL-2, IFN-gamma, and small amounts of IL-10. Unexpectedly, the transgenic mice do not develop diabetes and have no insulitis. Analysis with a GAD65 286-300/I-A(g7) tetramer reveals that transgenic T cells are negatively selected in the thymus and further negatively selected in the periphery. When crossed to the C(alpha)(-/-) NOD line, CD4 T cells were reduced by 90% in the thymus and periphery. Further, the tetramer positive GAD65 286-300 specific T cells were capable of delaying the onset of diabetes in a standard transfer system. Thus, GAD65 specific TCR transgenic T cells (1) must express a second a chain to survive negative selection, (2) produce IL-2 and IFN-gamma, and (3) have a mildly protective effect on transfer of diabetes with diabetogenic spleen cells.

Immunization of rabbits, and inbred strains of mice with branched, multichain, synthetic polypeptides, such as (T, G) - A--L and (H, G) - A--L, revealed striking differences in the ability of different strains of mice to produce specific antibody. F1 and F1 x parental backcross mice revealed clear genetic control. Initial attempts to link this genetic control to known genetic markers were unsuccessful. The second approach, which attempted to transfer response from high or immediate responders into low responder recipients, initially encountered graft vs. host and host vs. graft reactions. The transfer of F1 spleen cells into the low responder parent demonstrated that ability to respond was a property of immunocompetent cells (spleen cells), not of the recipient's background genes. Mapping studies with recombinant H2 haplotype congenic strains, and a classic 4-point mapping cross were concordant in placing the gene controlling this trait within the H2 complex, between the K and Ss loci. Subsequent studies mapped the genes for stimulation in the mixed lymphocyte culture reaction to the same position, suggesting cell surface expression. Production of antisera to 'I-region' products defined 'Ia' antigens, the 2-chain alpha/beta MHC class II molecules.

To assess the role of lymphotoxin-β receptor (LTβR) in diabetes pathogenesis, we expressed an LTβR–Fc fusion protein in nonobese diabetic (NOD) mice. The fusion protein was expressed in the embryo, reached high levels for the first 2 wk after birth, and then declined progressively with age. High expression of LTβR–Fc blocked diabetes development but not insulitis. After the decline in chimeric protein concentration, mice became diabetic with kinetics similar to the controls. Early expression of fusion protein resulted in disrupted splenic architecture. However, primary follicles and follicular dendritic cells, but not marginal zones, developed in aged mice. Hence, LTβR signaling is required for diabetes development and regulates follicular and marginal zone structures via qualitatively or quantitatively distinct mechanisms.

[Formula: see text] The discovery that genes in the major histocompatibility complex (MHC) play an important role in the immune response depended on the chance interaction of several unrelated events. The first, and most important, was the decision by Michael Sela to synthesize a series of branched, multichain, synthetic polypeptides based on a backbone of poly-l-lysine. The prototype compound, (T,G)-A–L, was tipped with short random sequences of tyrosine and glutamic acid. This resulted in a restricted range of antigenic determinants composed of only two or three amino acids with a variable length—ideal for binding to the peptide binding groove of MHC class II molecules.The second was the decision by John Humphrey to immunize various strains of rabbits with this synthetic polypeptide. Two of these rabbit strains showed very large quantitative differences in antibody response to (T,G)-A–L. In transferring this system to inbred mouse strains, the third bit of good fortune was the availability at the National Institute of Medical Research, in Mill Hill (London), of the CBA (H2k) and C57 (H2b) strains. The H2bhaplotype is the only one mediating a uniform high antibody response to (T,G)-A–L. The fourth critical ingredient was the availability of numerous congenic and H2 recombinant inbred strains of mice produced earlier by Snell, Stimpfling, Shreffler, and Klein. A search for congenic pairs of mice expressing the responder and nonresponder H2 haplotypes on the same background revealed that these strains responded as a function of their H2 haplotype, not of their inbred background. Extensive studies in a variety of inbred strains carrying recombinant H2 haplotypes, as well as a four-point linkage cross, mapped immune response to (T,G)A–L within the murine MHC, between the K and Ss loci.The demonstration that stimulation in the mixed lymphocyte reaction (MLR) mapped to the same region quickly led to attempts to produce antisera in congenic H2 recombinant strain combinations. These antisera identified I-region associated (Ia) antigens. Immunoprecipitation and blocking studies showed that the gene products controlling specific immune responses, the mixed lymphocyte reaction, and the structure of Ia antigens were one and the same—now designated as the I-A MHC class II molecules. These antisera and inbred strains enabled Unanue to demonstrate the peptide binding function of class II MHC molecules.

The N-terminal peptide Ac1-11 of myelin basic protein induces experimental autoimmune encephalomyelitis in H-2uand (H-2u× H-2s) mice but does not in H-2smice. Ac1-11 binds weakly to the class II major histocompatibility complex (MHC) molecule I-Aubut not at all to I-As. We have studied the interaction of Ac1-11 and I-Auas a model system for therapeutic intervention in the autoimmune response seen in experimental autoimmune encephalomyelitis. Two polymorphic residues that differ between I-Auand I-As, Y26β and T28β, and one conserved residue, E74β, confer specific binding of Ac1-11 to I-Au. A fourth residue, R70β in I-Au, affects both peptide binding and T cell recognition. These results are consistent with a model that places arginine at position five of Ac1-11 in pockets 4 and 7 of the MHC groove, which is formed in part by residues 26, 28, 70, and 74 of Aβuand places lysine at position four of Ac1-11, previously shown to be a major MHC contact, in hydrophobic pocket 6. The data indicate that the primary region of I-Authat confers specific binding of Ac1-11 lies in the center of the peptide binding groove rather than in the region that contacts the N terminus of the peptide, as has been shown for HLA DR and the homologous I-E molecules.

MHC class II molecules function by selective binding of antigenic peptides, thereby both shaping the T-cell receptor (TCR) repertoire in the thymus and influencing presentation of immunogenic peptides to CD4+ T cells in the periphery. The strong association between a number of human autoimmune diseases (type 1 diabetes, rheumatoid arthritis, and multiple sclerosis) and certain HLA-DR/DQ alleles suggests that it may be possible to alter pathological autoimmune responses by deliberate introduction of autoantigenic peptides in a "tolerogenic" manner. Since there are likely to be differences in epitope selection and epitope spreading in different patients over time, this approach requires identification of all the immunogenic CD4+ T-cell epitopes (dominant, subdominant, or cryptic) of an autoantigen which elicit T-cell responses restricted to the HLA-DR/DQ alleles predisposing to these autoimmune diseases. This paper describes a new approach for the identification of immunogenic peptide epitopes of human autoantigenic proteins using HLA-DR and DQ transgenic mice. These mice are engineered to select a full TCR repertoire which can identify immunogenic peptide epitopes similar or identical to human subjects of the same HLA-DR/DQ genotype. This experimental system also allows comparison of autoantigenic immune responses restricted to disease-susceptible and disease-resistant HLA-DR/DQ alleles.

IDDM is a T-cell-mediated autoimmune disease in which the insulin-producing beta-cells are destroyed. The disease process is complex, involving the recognition of several beta-cell autoantigens. One of these, GAD65, appears to have a critical and not fully defined role in IDDM in humans and in the NOD mouse. We provide evidence that an ongoing diabetogenic response in NOD mice can be suppressed after intravenous administration of GAD65, but not by other beta-cell autoantigens. Furthermore, suppression of the diabetogenic response is mediated by the induction of GAD65-specific CD4+ regulatory T-cells. Finally, cytokine analysis indicates that these CD4+ regulatory T-cells have a T-helper 2 phenotype.

Systemic injection of antigen is one of the approaches that reproducibly induces effective antigen-specific hyporesponsiveness. Here, Roland Liblau and colleagues discuss the cellular and molecular bases of such tolerance, review the current use of this therapeutic strategy in experimental organ-specific autoimmune diseases and analyse what steps are necessary to make this approach suitable for clinical use.

Experimental autoimmune encephalomyelitis (EAE) serves as a rodent model of the autoimmune disease multiple sclerosis. In mice, EAE is induced by immunizing with spinal cord homogenate, components of the myelin sheath, such as myelin basic protein (MBP) or proteolipid protein (PLP), or peptides derived from these components. EAE can be induced in H-2u or (H-2u x H-2s)F1 mice with the N-terminal peptide of MBP, Ac1-11. Coimmunization with Ac1-11 and Ac1-11[4A], an analog in which lysine at position four is substituted with alanine, prevents EAE. The mechanism of inhibition has not been elucidated, but probably does not work through MHC blockade, T cell anergy or clonal elimination of encephalitogenic T cells. We have isolated T cell clones and hybridomas from (PL/J x SJL/J)F1 mice immunized with either Ac1-11 alone or Ac1-11 and Ac1-11[4A] and analysed these cells for differences in their T cell receptor repertoire and in vitro response. Although T cells elicited by coinjection of Ac1-11 and Ac1-11[4A] expressed TCR that used V alpha and Vbeta gene elements similar to those elicited by Ac1-11 alone, they differed in the sequences of the junctional region of the alpha chain. Most of these T cells also responded less well to Ac1-11 in vitro, suggesting that coinjection of Ac1-11 and Ac1-11[4A] preferentially activates T cells bearing TCR of different affinity for Ac1-11 bound to I-A(u), and which may therefore be less encephalitogenic. Furthermore, our results show that a more diverse repertoire of V alpha and Vbeta genes are elicited by Ac1-11 in (PL/J x SJL/J)F1 mice compared to PL/J and B10.PL mice, providing further evidence that a restricted TCR repertoire is not required for the development of autoimmune disease.

The autoantigen glutamic acid decarboxylase 65 (GAD 65) is believed to be an important target antigen in insulin-dependent diabetes mellitus (IDDM), since an age-related spontaneous breakdown in tolerance is observed, and cell-mediated and autoantibody immune responses have been reported in humans and NOD mice. We sought to identify immunogenic epitopes of GAD 65 which are presented to T cells by the type I diabetes susceptibility allele (A g7 ), using overlapping 15-mer synthetic peptides spanning the entire sequence of this protein. Four epitopes (p206 – 220, p221 – 235, p286 – 300, p571 – 585) were identified by screening a panel of T-cell hybridomas generated from GAD 65-immunized NOD mice. These immunogenic epitopes are unrelated to the previously described T-cell epitopes of GAD 65 reported in NOD mice. Of the GAD 65 amino acid sequence, 206 – 220 and 221 – 235 are the two most dominant T-cell epitopes identified in this study. Sixty-three percent and 25% of GAD 65-responding T cell hybridomas react to p206 – 220 and p221 – 235, respectively. The remaining two peptides (p286 – 300, p571 – 585) are less dominant T-cell responses. The identification of the whole spectrum of GAD 65 Ag7 epitopes should further the investigation of the role of this autoantigen in the pathogenesis of IDDM.

Multiple sclerosis is an autoimmune disease thought to be mediated by CD4+ T helper cells (Th). Experimental autoimmune encephalomyelitis is a rodent model of multiple sclerosis and has been used extensively to explore a variety of immunotherapies using soluble protein or peptide antigens. The underlying mechanisms of such therapy have been attributed to induction of T cell anergy, a switch in Th1 to Th2 responses, or peripheral deletion of autoreactive T cells. In this study, we have developed transgenic mice expressing a T cell receptor (TCR) specific for the NH2-terminal peptide Ac1-11 of the autoantigen myelin basic protein to explore the mechanism of soluble peptide therapy. T cells from these mice are highly skewed toward the CD4 population and have an abnormal thymic architecture, a phenomenon found in other TCR transgenic mice that exhibit a highly skewed CD4/CD8 ratio. Soluble Ac1-11 or the analogues Ac1-11[4A] or Ac1-11[4Y] (which bind to the major histocompatibility complex [MHC] class II molecule I-Au with increasing affinities) given intravenously activates T cells, rendering cells hyperresponsive in vitro for at least two days after injection. Concomitantly, T cells apoptose in the periphery, the degree of which correlates with the affinity of the peptide for the MHC. In addition, a shift in the T helper phenotype of the surviving T cells occurs such that the low affinity peptide, Ac1-11, induces primarily a Th1 response, whereas the highest affinity peptide, Ac1-11[4Y], induces primarily a Th2 type response. These data show that both the nature and the presumed number of the peptide–MHC complexes formed during specific peptide therapy affect both the degree of peripheral programmed cell death as well as the outcome of the T helper subset response in vivo, leading to amelioration of disease.

The possible involvement of Fas/APO-1 (CD95) and TNF in antigen-specific AICD of thymocytes and mature T cells has been investigated. Antigenic stimulation in vivo of influenza hemagglutinin (HA)-specific TCRtg mice was used to demonstrate that the kinetics of thymocyte and peripheral CD4+ T cell deletion are similar in mice with normal (+/+) or defective Fas (lpr/lpr) background, indicating that a Fas-independent pathway(s) is responsible for the deletion of activated T cells. TCRtg–+/+ or TCRtg–lpr/lpr mice injected with murine TNF-blocking MAb (TN3) showed rapid apoptosis of thymocytes after HA stimulation, indicating that death signaling through Fas and TNF receptors is not essential for HA-induced thymocyte deletion. CD4+ peripheral T cells in TCRtg–lpr/lpr mice did not undergo apoptosis following injection with HA and TN3, indicating that TNF-mediated apoptosis is involved in the deletion of mature T cells after antigenic stimulation. However, apoptosis still occurred in TCRtg–+/+ mice injected with TN3, indicating that both Fas- and TNF-mediated cell death can contribute to the deletion of activated peripheral T cells.

Early attempts to prevent IDDM typically relied on immunosuppressive drugs (cyclosporine) or drugs that indiscriminantly inhibit cell proliferation (imuran), often leading to serious side effects. Therefore, a great deal of effort has focused on selectively targeting those T cells involved in the disease process. One general approach has been to employ monoclonal antibodies specific for molecules expressed by the effector T cell population. Monoclonal antibodies specific for CD4 (Shizuru et al. 1988xImmunotherapy of the nonobese diabetic mouse; treatment with an antibody to T helper lymphocytes. Shizuru, J.A, Taylor-Edwards, C, Banks, B.A, Gregory, A.K, and Fathman, C.G. Science. 1988; 240: 659–662Crossref | PubMedSee all ReferencesShizuru et al. 1988) and CD3, a component of TCRs (Chatenoud et al. 1993xAnti-CD3 antibody induces long-term remission of overt autoimmunity in nonobese diabetic mice. Chatenoud, L, Thervet, E, Primo, J, and Bach, J.F. Proc. Natl. Acad. Sci. USA. 1993; 91: 123–127Crossref | Scopus (456)See all ReferencesChatenoud et al. 1993), have been shown to be effective in the prevention and treatment, respectively, of diabetes in NOD mice. Similarly, prediabetic NOD mice are protected from disease when treated with antibodies that interfere with antigen recognition (anti-class II, Boitard et al. 1988xPrevention of diabetes in nonobese diabetic mice by anti- I-A monoclonal antibodies (transfer of protection by splenic T cells) . Boitard, C, Bendelac, A, Richard, M.F, Carnaud, C, and Bach, J.F. Proc. Natl. Acad. Sci. USA. 1988; 85: 9719–9723Crossref | PubMedSee all ReferencesBoitard et al. 1988; anti-TCR, Sempe et al. 1991xAnti-α/β T cell receptor monoclonal antibody provides an efficient therapy for autoimmune diabetes in nonobese diabetic (NOD) mice. Sempe, P, Bedossa, P, Richard, M.F, Villa, M.C, Bach, J.F, and Boitard, C. Eur. J. Immunol. 1991; 21: 1163–1169Crossref | PubMedSee all ReferencesSempe et al. 1991), cellular activation (anti-B7; Lenschow et al. 1995xDifferential effects of anti-B7-1 and anti-B7-2 monoclonal treatment on the development of diabetes in the nonobese diabetic mouse. Lenschow, D.J, Ho, S.C, Sattar, H, Rhee, L, Gray, G, Nabavi, N, Herold, K.C, and Bluestone, J.A. J. Exp. Med. 1995; 181: 1145–1155Crossref | PubMed | Scopus (528)See all ReferencesLenschow et al. 1995), and homing to the pancreas (anti–L selectin and anti-VLA-4; Yang et al. 1993xInhibition of insulitis and prevention of diabetes in nonobese diabetic mice by blocking L-selectin and very late antigen 4 adhesion receptors. Yang, X.D, Karin, N, Tisch, R, Steinman, L, and McDevitt, H.O. Proc. Natl. Acad. Sci. USA. 1993; 90: 10494–10498Crossref | PubMedSee all ReferencesYang et al. 1993). Finally, antibodies targeting cytokines associated with Th1 activity (anti-IFNγ, anti-TNFα, and anti-IL-12; Rabinovitch 1994xImmunoregulatory and cytokine imbalances in the pathogenesis of IDDM. Therapeutic intervention by immunostimulation. Rabinovitch, A. Diabetes. 1994; 43: 613–621Crossref | PubMedSee all ReferencesRabinovitch 1994) have been able to prevent disease in prediabetic NOD mice. In general, however, the applicability of antibodies specific for these “immune–related molecules” to human IDDM is limited by the side effects of chronic administration, such as immunogenicity, and the lack of selectivity.An alternative approach is to devise protocols in which immunomodulation can be selectively applied through the use of a specific antigen/peptide. Recently, it has been demonstrated that insulin, when adminstered prior to the onset of diabetes, can delay or prevent disease in individuals at high risk for IDDM (Keller et al. 1993xInsulin prophylaxis in individuals at high risk of type I diabetes. Keller, R.J, Eisenbarth, G.S, and Jackson, R.A. Lancet. 1993; 341: 927–928Abstract | PubMed | Scopus (261)See all ReferencesKeller et al. 1993). The precise mechanism by which protection is mediated is not known. Both metabolic and immunologic factors may contribute to the effectiveness of this form of therapy. Nevertheless, multicenter trials of subcutaneous insulin prophylaxis to individuals at high risk for developing diabetes have recently been initiated.In general, antigen-specific tolerance can be induced via two distinct processes: clonal deletion/anergy and induction of regulatory T cells. Clonal deletion/anergy has been shown to be effective in acute experimental autoimmune diseases where the inciting autoantigen/peptide is known. However, the high degree of specificity associated with this approach might be limiting in IDDM, in which the inciting autoantigen is not known, and where spreading of the autoimmune response to a number of epitopes within a single autoantigen and targeting of other autoantigens occur. Despite these reservations, administration of GAD, insulin, or HSP60 (but not carboxypeptidase H or peripherin) to NOD mice appears to result in the induction of antigen-specific regualtory T cells (Th2) that effectively suppress the disease. These regulatory T cells are thought to suppress the effects of nearby diabetogenic T cells through the antigen-stimulated secretion of IL-4, IL-10, and TGFβ. The advantage of this approach is that knowledge of the inciting β cell autoantigen (if only one such antigen truly exists) is not required. However, it is still unclear whether regimens can be devised that effectively induce a long lasting form of active suppression with no deleterious side effects in a clinical setting. For example, oral administration of antigen appears to be nontoxic, but its effects are variable and dose specific. This does not appear to be the case with systemically administered antigen. However, the possibility exists that systemic administration of antigen might have an immunizing effect and exacerbate disease.Although antigen-specific immunotherapy appears to be a promising method to prevent IDDM, it is most likely that a combination of approaches may prove to be more generally effective. Thus, active suppression by antigen-induced regulatory T cells may be enhanced in concert with antibodies targeting cytokines required for Th1 development and function. Furthermore, as additional β cell autoantigens are identified and shown to have a role in the disease process, therapy might employ a number of autoantigens to target the polyclonal population of autoreactive T cells, thereby increasing the likelihood of successful treatment.Even if safe, effective, and long lasting immunotherapies are developed, their application is a formidable challenge. Only 15% of new cases of IDDM occur in families with a previous case in the kindred. Overt diabetes develops only when β cell destruction is nearly complete, and the patient is asymptomatic for months or years until that point is reached. Immunotherapy thus must be preventive, which requires inexpensive, accurate genetic, autoantibody, and T cell screening techniques. Given the large number of islet cell autoantigens now available and the rapid progress in identifying genetic susceptibility markers, such screening techniques should soon be feasible. Hopefully, effective methods of prevention will promote widespread population screening and the application of preventive therapy.

The mechanism by which tolerance is induced via systemic administration of high doses of aqueous antigen has been analyzed by using mice transgenic for a T-cell receptor specific for the influenza virus hemagglutinin (HA) peptide comprising amino acids 126-138. After intravenous injection of 750 (but not 75) micrograms of HA peptide, a state of hyporesponsiveness was rapidly induced. In the thymus, in situ apoptosis in the cortex and at the corticomedullary junction was responsible for a synchronous and massive deletion of CD4+ CD8+ thymocytes. In secondary lymphoid organs, HA-reactive T cells were initially activated but were hyporesponsive at the single cell level. After 3 days, however, those cells were rapidly deleted, at least partially, through an apoptotic process. Therefore, both thymic and peripheral apoptosis, in addition to T-cell receptor desensitization, contribute to high-dose tolerance.

An important issue in autoimmune diseases mediated by T cells, such as experimental allergic encephalomyelitis (EAE), is the affinity of the disease-inducing determinants for MHC class II proteins. Tolerance, either due to clonal deletion or anergy induction, is thought to require high-affinity interactions between peptides and MHC molecules. Low-affinity binding is compatible with the hypothesis that breaking tolerance to self proteins does not have to occur for onset of disease. In contrast, a high-affinity interaction implies that an event leading to a breakdown of tolerance is central to the autoimmune process. Detergent-solubilized and affinity-purified I-Au was incubated with varying concentrations of a set of peptides from myelin basic protein and a biotinylated peptide agonist. The specific complexes were separated from excess peptide by capture on antibody-coated plates, and the affinity of the peptides was measured by adding europium-labeled streptavidin and measuring the resultant fluorescence. The immunodominant and encephalitogenic determinant, Ac 1–11, was shown to bind to I-Au relatively poorly (IC50 = 100 µM), demonstrating that in this protein, immunodominance did not correlate with high-affinity binding. In contrast with the natural sequence, the ability of shorter analogs to induce EAE did correlate with their apparent affinity. The dominance of the natural determinant does not arise from a high-affinity interaction with the MHC class II molecule. This suggests that other mechanisms are operative and that the specific T cell for this peptide/MHC ligand is of high affinity.

Invariant chain (Ii) associates with major histocompatibility complex (MHC) class II molecules and is crucial for antigen presentation by class II molecules. The exact nature of Ii interaction with MHC class II molecules remains undefined. A nested set of Ii peptides, CLIPs (class II-associated Ii peptides), have been eluted from various MHC class II molecules, suggesting that CLIPs correspond, at least in part, to the Ii motif which blocks the conventional peptide binding site in MHC class II molecules. Here we report how CLIPs interact with class II MHC molecules, I-A. We have identified regions critical for binding of CLIPs and I-A class II molecules. In most cases, the binding of CLIPs to a number of I-A molecules is modulated by the steric bulk of methionine residues at positions 93 and 99. In addition, the binding of CLIPs to an I-A molecule, I-Au, is sensitive to substitutions at aspartic acid-59 in the alpha chain and threonine-86 in the beta chain, whereas the binding of an antigen-derived peptide is not. Taken together, these results provide an insight as to how CLIPs bind to MHC class II heterodimers.

CD4+ T cells play a key role in regulating immune system function. When these regulatory processes go awry, organ-specific autoimmune diseases may develop. Here, Roland Liblau, Steven Singer and Hugh McDevitt explore the thesis that a particular subset of CD4+ T cells, namely T helper 1 (Th1) cells, contributes to the pathogenesis of organ-specific autoimmune diseases, while another subset, Th2 cells, prevents them.

OBJECTIVE To evaluate the role of the T cell receptor beta chain locus (TCRB) in genetic susceptibility to rheumatoid arthritis (RA). METHODS Twenty-eight multiplex RA families were recruited from 3 rheumatology outpatient departments. All members were genotyped for a highly informative microsatellite (V beta 6.7), a V beta 12.2 SSCP marker, and a biallelic C beta restriction fragment length polymorphism. Data were analyzed by the SIBPAL program to assess identity-by-descent in affected sib-pairs. RESULTS Using the V beta 12.2 marker, there was suggestive evidence of increased sib-pair sharing (P = 0.005) in affected offspring (a P value of 0.001 is generally taken to establish linkage). Data for V beta 6.7 and C beta yielded significance levels of 0.06 and 0.19, respectively. CONCLUSION These data suggest that a gene in or linked to the TCRB complex may confer genetic susceptibility to RA in these families. Confirmation in a larger panel of families is required.

To elucidate the role of cell adhesion molecules in the pathogenesis of insulin-dependent diabetes mellitus and to determine the predominant lymphocytic homing pathway(s) involved in the selective lymphocytic infiltration of pancreatic islets (insulitis), nonobese diabetic mice were treated with monoclonal antibodies specific for the L-selectin and integrin alpha 4 lymphocyte adhesion molecules. Treatment of neonatal mice with either anti-L-selectin or anti-integrin alpha 4 monoclonal antibodies for the first 4 weeks of life led to a significant and long-term protection against spontaneous occurrence of insulitis and diabetes. The same treatment failed to inhibit lymphocytic infiltration of the salivary glands (sialadenitis). This tissue-specific inhibition of inflammation may be attributed to differences between the pancreas and salivary gland in their expression of endothelial ligands for L-selectin (peripheral vascular addressin) and for integrin alpha 4 (mucosal addressin cell adhesion molecule 1 and vascular cell adhesion molecule 1). Mucosal addressin cell adhesion molecule 1 is highly expressed by vessels within the inflamed islets but was not detected in the salivary glands. In contrast, peripheral vascular addressin- and vascular cell adhesion molecule 1-expressing vessels can be found in almost every area of inflammation within the salivary glands but are seen in only 40-50% of inflamed islets. Anti-L-selectin and anti-integrin alpha 4 treatment had no demonstrable effect on anti-beta-cell autoimmunity or on the immune responses to foreign antigens. Therapeutic treatment with anti-L-selectin after the onset of insulitis from 10 to 14 weeks of age delayed the onset but failed to prevent spontaneous insulin-dependent diabetes mellitus, whereas anti-integrin alpha 4 treatment resulted in a significant and long-lasting suppression of the disease. These data strongly suggest that integrin alpha 4 plays a prominent role in the spontaneous development of insulitis and diabetes in nonobese diabetic mice.

Type 1 1diabetes is the result of an ongoing autoimmune response to specific proteins expressed by the insulin producing β cells. Recently, a number of β cell autoantigens have been identified. However, their role in mediating the diabetogenic response is not know. Here we assess the relative importance of a panel of β cell autoantigens in the disease process. The approach was to inhibit T cell proliferation to a given autoantigen by either i.t. or i.v. injections, and then determine the effect this had on the diabetogenic response. We show that administering murine glutamic acid decarboxylase (GAD) to 3-week-old NOD females can reduce the frequency of insulitis and prevent the onset of diabetes. In contrast, carboxypeptidase H or peripherin do not induce a similar protective effect, suggesting that GAD has a critical role in the diabetogenic response. These results also suggest that GAD may provide a useful target for antigen-specific immunotherapy.

Selective homing of autoreactive lymphocytes to the pancreatic islets of Langerhans is essential for triggering the cascade of molecular and cellular interactions which culminate in the specific destruction of the insulin-producing beta-cells. Based upon the sequential multistep model of lymphocyte adhesion to the endothelium, we investigated the possibility of preventing the progression of insulin-dependent diabetes mellitus (IDDM) by selectively blocking L-selectin and alpha 4-integrin homing receptors, which function at different stages of the adhesion process. Treatment of NOD mice with mAb specific for L-selectin or alpha 4-integrin resulted in a significant inhibition of lymphocytic infiltration (insulitis). Both spontaneous development and acute transfer of IDDM were completely prevented by administration of anti-alpha 4-integrin antibody and partially inhibited by anti-L-selectin antibody. The protective effect was of long duration. Interestingly, the autoimmune T cell responses to a panel of beta cell autoantigens and the lymphocytic infiltration of salivary glands (sialadenitis) appeared unaffected by anti-L-selectin or anti-alpha 4-integrin treatment. These data suggest that prevention of lymphocyte homing to the pancreatic islets may provide a selective target for prevention/treatment of IDDM in patients.

The HLA-DRB1, -DRB3, -DRB4, and -DRB5 alleles of the Guarani and Kaingang Amerindians were characterized. Our previous serologic analyses detected three class II haplotypes among the Kaingang: DR2-DQ3, DR4-DQ3, and DR8-DQ4. In addition to these, the Guarani presented haplotype DR6-DQ3. Individuals typed serologically (67 Kaingang and 34 Guarani) were selected for molecular analyses. Using a set of 23 SSOs for hybridization of PCR products from generic DRB amplification six different haplotypes were identified, of which only three are shared by the two tribes. The oligonucleotide hybridization patterns are compatible, with haplotypes DRB1 ∗ 1602-DRB5 ∗ 02, DRB1 ∗ 0404-DRB4 ∗ 0101, DRB1 ∗ 0802, and DRB1 ∗ 0901-DRB4 ∗ 0101 in the Kaingang tribe, and haplotypes DRB1 ∗ 1602-DRB5 ∗ 02, DRB1 ∗ 0411-DRB4 ∗ 0101, DRB1 ∗ 1413-DRB3 ∗ 0101, DRB1 ∗ 0802, and DRB1 ∗ 0901-DRB4 ∗ 0101 among the Guarani. DRB1 ∗ 1413 is a new allele, most closely related to DRB1 ∗ 1402, which is common among South and North American Indians. At the segments analyzed, they differ solely at position 57, which is GAT (aspartic acid) in DRB1 ∗ 1402 and AGC (serine) in DRB1 ∗ 1413. This allele probably originated in South American Indians, resulting from a single segmental exchange event between alleles DRB1 ∗ 1402 (the acceptor) and DRB1 ∗ 0411.

Graft-versus-host disease across minor histocompatibility barriers was induced in two different models by transplanting allogeneic bone marrow and spleen cells into irradiated H-2-compatible recipient mice. In this report, we show that administration of peptides with high binding affinity for the respective class II major histocompatibility complex molecules after transplantation is capable of preventing the development of graft-versus-host disease in two different murine models. The peptides used were myelin basic protein residues 1 through 11 with alanine at position 4 (Ac 1–11[4A]) for I-Au (A alpha uA beta u), and the antigenic core sequence 323 through 339 of ovalbumin with lysine and methionine extension (KM core) for I-As (A alpha sA beta s). In both systems, the mechanism of prevention was found to be major histocompatibility complex-associated, because nonbinding control peptides did not have any effect. Engraftment of allogeneic bone marrow cells was shown by polymerase chain reaction analysis of DNA polymorphisms in a microsatellite region within the murine interleukin- 5 gene.

Tumor necrosis factor (TNF) alpha is a cytokine that has potent immune regulatory functions. To assess the potential role of this cytokine in the early development of autoimmunity, we investigated the effect of TNF on the development of insulin-dependent diabetes mellitus (IDDM) in nonobese diabetic (NOD) mice, a spontaneous murine model for autoimmune, insulin-dependent type I diabetes. Treatment of newborn female NOD mice with TNF every other day for 3 wk, led to an earlier onset of disease (10 versus 15 wk of age in control mice) and 100% incidence before 20 wk of age (compared to 45% at 20 wk of age in control phosphate-buffered saline treated female mice). In contrast, administration of an anti-TNF monoclonal antibody, TN3.19.12, resulted in complete prevention of IDDM. In vitro proliferation assays demonstrated that mice treated with TNF developed an increased T cell response to a panel of beta cell autoantigens, whereas anti-TNF treatment resulted in unresponsiveness to the autoantigens. In addition, autoantibody responses to the panel of beta cell antigens paralleled the T cell responses. The effects mediated by TNF appear to be highly age dependent. Treatment of animals either from birth or from 2 wk of age had a similar effect. However, if treatment was initiated at 4 wk of age, TNF delayed disease onset. These data suggest that TNF has a critical role in the early development of autoimmunity towards beta-islet cells.

Peripheral immunological tolerance is traditionally explained by mechanisms for deletion or inactivation of autoreactive T cell clones. Using an autoimmune disease model combining transgenic mice expressing a well-defined antigen, influenza hemagglutinin (HA), on islet beta cells (Ins-HA), and a T cell receptor transgene (TCR-HNT) specific for a class II-restricted HA peptide, we demonstrate that the conventional assumptions do not apply to this in vivo situation. Double transgenic mice displayed either resistance or susceptibility to spontaneous autoimmune disease, depending on genetic contributions from either of two common inbred mouse strains, BALB/c or B10.D2. Functional studies on autoreactive CD4+ T cells from resistant mice showed that, contrary to expectations, neither clonal anergy, clonal deletion, nor receptor desensitization was induced; rather, there was a non-MHC-encoded predisposition toward differentiation to a nonpathogenic effector (Th2 versus Th1) phenotype. T cells from resistant double transgenic mice showed evidence for prior activation by antigen, suggesting that disease may be actively suppressed by autoreactive Th2 cells. These findings shed light on functional aspects of genetically determined susceptibility to autoimmunity, and should lead to new therapeutic approaches aimed at controlling the differentiation of autoreactive CD4+ effector T cells in vivo.

Insulin-dependent diabetes mellitus (IDDM) is thought to result from chronic, cell-mediated, autoimmune islet damage. Our aim was to identify the earliest T-cell autoantigen in IDDM, reasoning that this antigen could be causally involved in the initiation of the disease. Identification of the earliest β-cell-specific autoantigen is extremely important in allowing advances in prevention and treatment of initial events in the development of inflammatory insulitis that precedes β-cell destruction and overt diabetes. Therefore, we analyzed the proliferative responses of peripheral β-cells from young, female nonobese diabetic (NOD) mice to extracts of pancreatic β-cell lines. We were able to demonstrate that T-cells responsive to β-cell antigens exist in the peripheral lymphoid tissue of these mice in the absence of deliberate priming before the manifestation of histologically detectable insulitis. T-cell lines and clones isolated from the peripheral lymphatic tissues of young, unimmunized, female NOD mice were also shown to react with extracts of β-cells. Fractionation of the β-cell extracts showed that these T-cell clones recognized multiple β-cell-specific autoantigens but none of the previously reported putative autoantigens (glutamic acid decarboxylase [GAD]65, GAD67, Hsp65, insulin, ICA 69, car boxy peptidase-H, and peripherin). Thus, we can conclude that these responses are specific for novel β-cell autoantigens. Finally, NOD T-cell proliferative responses were also seen to an extract of human islets suggesting potential shared antigenic determinants between human and mouse β-cells. Our observation that human and murine β-cell-specific antigens are conserved offers the possibility that identification of these murine autoantigens may lead to the discovery of the human homologue. This will pave the way toward effective diagnosis and/or immunotherapy to prevent diabetes.

Knowing the autoantigen target(s) in an organ-specific autoimmune disease is essential to understanding its pathogenesis. Insulin-dependent diabetes mellitus (IDDM) is an autoimmune disease characterized by lymphocytic infiltration of the islets of Langerhans (insulitis) and destruction of insulin-secreting pancreatic beta-cells. Several beta-cell proteins have been identified as autoantigens, but their importance in the diabetogenic process is not known. The non-obese diabetic (NOD) mouse is a murine model for spontaneous IDDM. Here we determine the temporal sequence of T-cell and antibody responses in NOD mice to a panel of five murine beta-cell antigens and find that antibody and T-cell responses specific for the two isoforms of glutamic acid decarboxylase (GAD) are first detected in 4-week-old NOD mice. This GAD-specific reactivity coincides with the earliest detectable response to an islet extract, and with the onset of insulitis. Furthermore, NOD mice receiving intrathymic injections of GAD65 exhibit markedly reduced T-cell proliferative responses to GAD and to the rest of the panel, in addition to remaining free of diabetes. These results indicate that the spontaneous response to beta-cell antigens arises very early in life and that the anti-GAD immune response has a critical role in the disease process during this period.

Type 1 diabetes (T1D) is an autoimmune disease in both humans and the nonobese diabetic (NOD) mouse, in which the insulin-producing-cells of the pancreatic islets are destroyed by a beta islet cell-specific T cell immune response. We recently reported that interferon (IFN)-α is an early trigger of the T1D process in NOD mice. Here, we show that extensive blockade of IFN-α action by a monoclonal antibody specific to IFN-α receptor 1 results in nearly complete prevention of T1D in NOD mice. Whether professional IFN-α producing cells, plasmacytoid dendritic cells (pDCs), are responsible for the initiation of T1D has been unclear. Here we demonstrate that depletion of pDCs in NOD mice by a specific mAb given at 15–25 days of age significantly delays the onset and decreases the incidence of T1D. These findings indicate that pDC and pDC-derived IFN-α are the prime initiators of the pathogenesis of T1D in NOD mice.

The minimum structural requirements for peptide interactions with major histocompatibility complex (MHC) class II molecules and with T cell receptors (TCRs) were examined. In this report we show that substituting alanines at all but five amino acids in the myelin basic protein (MBP) peptide Ac1-11 does not alter its ability to bind A alpha uA beta u (MHC class II molecules), to stimulate specific T cells and, surprisingly, to induce experimental autoimmune encephalomyelitis (EAE) in (PL/J x SJL/J)F1 mice. Most other amino acid side chains in the Ac1-11 peptide are essentially irrelevant for T cell stimulation and for disease induction. Further analysis revealed that binding to A alpha uA beta u occurred with a peptide that consists mainly of alanines and only three of the original residues of Ac1-11. Moreover, when used as a coimmunogen with MBP Ac1-11, this peptide inhibited EAE. The finding that a specific in vivo response can be generated by a peptide containing only five native residues provides evidence that disease-inducing TCRs recognize only a very short sequence of the MHC-bound peptide.

The high degree of polymorphism seen at major histocompatibility complex (MHC) class II loci is a feature unique to the MHC. Most of the beta-chain polymorphism is localized in "hypervariable" regions (HVRs). HVR amino acid sequence similarity between distantly related species has recently been found. We have employed a Monte-Carlo statistic to show that shared HVR polymorphism between beta-chain genes of humans and mice represents direct descent of ancestral sequences rather than convergent evolution. Furthermore, half the sequence polymorphism seen in class II beta-chain genes of mice persists in evolution and is encoded by the same DNA sequence in humans. No evidence for increased mutation rate within the HVR was found. We postulate that the HVR can be considered the genetic unit of recombination, with selection for HVR sequences and combinations of HVRs constrained by functional considerations.

In attempt to evaluate biological roles of tumor necrosis factor (TNF), we studied the effects of anti-TNF mAb in non-obese diabetic (NOD) mice. Anti-murine TNF mAb rendered NOD mice hypersensitive to the lethal effects of radiation and prevented the reconstitution of lethally irradiated mice with adoptively transferred lymphocytes. While TNF-alpha reduced the incidence of diabetes development in the adoptive transfer system even when given 6 days post-transfer, mAb to TNF could not reduce or increase the incidence of diabetes compared to control mice. Administration of TNF-alpha for 4 or 8 weeks significantly reduced the incidence of spontaneous insulitis in NOD mice, while anti-TNF mAb given for 8 weeks increased the incidence of insulitis significantly.

The cellular and molecular requirements for the autoimmune disease EAE are being defined in increasing detail through intense scrutiny of critical autoantigenic peptides, class II MHC molecules, and alpha beta TCRs involved in the disease process. This study has led to novel immunotherapeutic approaches, many of which are based on the administration of synthetic peptides. Since short peptides are understood to be the minimal antigenic units bound by MHC molecules for recognition by T cells, they are attractive experimental tools for finely modulating specific immune responses. It is clear that a large number of defined peptides can dramatically influence the course of EAE. Table IV lists a number of potential mechanisms which may mediate disease prevention. Increasing evidence supports the idea that prevention of autoimmune disease can result from MHC-blockade by peptides which competitively bind to class II molecules. However, for some peptides such as the perplexing partial agonist Ac1-11[4A], the mechanism by which these precisely defined units act is not yet fully understood. Numerous hurdles hinder immediate clinical application of peptide-based immunotherapy. Nevertheless, the knowledge gained by probing experimental autoimmunity with defined peptides promises to inspire original and practical approaches to treating human autoimmune disease.

Oligonucleotide probes were used to investigate the role of DQβ molecules in susceptibility to multiple sclerosis. Although shared amino acid and nucleotide sequences in DQβ1 have been suggested to be critical in disease development, we find that the distribution of sequences corresponding to residues 71–77 is not greater in patients versus controls.

Most autoimmune disorders are associated with particular alleles of the major histocompatibility complex (MHC) class II genes. However, only a minority of individuals with these alleles develop autoimmunity. The identification of alleles more closely associated with an autoimmune disorder such as lupus would facilitate screening and diagnosis and perhaps the understanding of mechanisms of disease. Analysis of sequence variation in the polymorphic first domain of the MHC genes HLA DQ beta and DQ alpha has revealed a novel DQ beta allele in two Caucasian lupus patients and no Caucasian controls. The novel DQ beta allele shares polymorphic amino acids at positions 26 to 30 and 57 with other lupus-associated DQ beta alleles. These hypervariable regions may play a role in lupus susceptibility and may provide insights into the molecular mechanism for this susceptibility.