Induction of the early growth response (Egr) family of transcription factors during thymic selection.

There is little known about the regulation of gene expression during TCR-mediated differentiation of immature CD4+8+ (double positive) thymocytes into mature T cells. Using the DPK CD4+8+ thymocyte precursor cell line, we demonstrate that the early growth response-1 gene (Erg-1), encoding a zinc finger transcription factor, is rapidly upregulated after TCR stimulation. We also report that Egr-1 is expressed by a subset of normal double positive thymocytes in the thymic cortex, as well by a majority of medullary single positive thymocytes. Expression of Egr-1 is dramatically reduced in the thymus of major histocompatibility complex knockout mice, but can be induced by anti-CD3 antibody stimulation of isolated thymocytes from these animals. These and other data suggest that high level expression of Egr-1 in the thymus is a consequence of selection. A similar pattern of expression is found for family members Egr-2 and Egr-3. Using the DPK cell line, we also demonstrate that expression of Egr-1, 2, and 3 is dependent upon ras activation, as is the initiation of differentiation to a single positive cell. In contrast, the calcineurin inhibitor cyclosporin A, which inhibits DPK cell differentiation as well as positive selection, inhibits expression of Egr-2 and Egr-3, but not Egr-1. The identification of the Egr family in this context represents the first report of a link between the two known signaling pathways involved in positive selection and downstream transcriptional regulators.

Peptide-specific prevention of experimental allergic encephalomyelitis. Neonatal tolerance induced to the dominant T cell determinant of myelin basic protein.

Experimental allergic encephalomyelitis (EAE) is a model of antigen-specific T cell-mediated autoimmune disease. The alpha-acetylated, NH2-terminal nine amino acids (1-9NAc) of myelin basic protein (MBP) represents the dominant T cell epitope for the induction of EAE in the B10.PL (H-2u) strain. We tolerized neonatal B10.PL mice to 1-9NAc and studied the proliferative responses to this peptide and to whole MBP. Mice exposed to 1-9NAc in the neonatal period were tolerant to subsequent challenge at the proliferative T cell level. Similarly, in the 1-9NAc-tolerant group, both the incidence and severity of 1-9NAc induced EAE were greatly reduced. The fact that we were able to tolerize mice normally responsive to MBP suggests that this self antigen is sequestered (within the central nervous system) and hence tolerance to it is not normally induced. No significant difference in disease incidence was seen in response to rat MBP between control animals and 1-9NAc-tolerized mice (50% in both groups), demonstrating the presence of at least one additional encephalitogenic determinant elsewhere on the molecule. We have successfully prevented disease induction by peptide-induced tolerization. Tolerance induction by peptides provides a new and specific strategy in the prevention of autoimmunity. However, it will be clearly necessary to fully define all epitopes potentially capable of inducing pathogenic T cells to ensure complete and effective therapy of T cell-mediated autoimmune disease.

Two minor determinants of myelin basic protein induce experimental allergic encephalomyelitis in SJL/J mice.

Experimental allergic encephalomyelitis (EAE) is an autoimmune demyelinating disease of the central nervous system (CNS) that occurs after immunization of animals with myelin basic protein (MBP). The disease is a prototype model for the study of antigen-specific T helper cell-mediated autoimmune disease. In SJL/J mice, EAE is mediated by T helper cells directed against a 40-amino acid COOH-terminal peptic fragment of mouse small MBP. To identify the minimal T cell epitopes of MBP responsible for EAE, overlapping peptides completely encompassing the epitopes within this region were synthesized. A 28-residue peptide of mouse MBP spanning residues 87-114 (pM87-114) was able to elicit both a strong T cell response and chronic relapsing disease. To better localize the T cell epitopes, shorter peptides within this region were synthesized and two overlapping peptides, pM87-98 and pM91-104, were able to induce EAE. T cell clones and bulk lymph node cell populations reactive with pM87-98 did not respond to pM91-104. However, lymph node cells reactive with pM91-104 also reacted with pM87-98, thus showing that these two peptides represent contiguous, but distinct encephalitogenic epitopes and that both these epitopes may be contained within pM87-98. In addition, pM87-114 and pM87-98 were found to be minor determinants of the total T cell response to rat and rabbit MBP. The restricted response to MBP in SJL/J mice is similar to that of the PL/J mice in that each appears to have only a single peptide region in MBP that elicits encephalitogenic T cells. However, within the region studied, there were two if not more T cell epitopes. This differs from the single encephalitogenic PL/J epitope. These findings of a single encephalitogenic peptide region with multiple T cell epitopes and the fact that encephalitogenic T cell epitopes may be subdominant have implications for the design of treatments directed at the T cell receptor-MHC-peptide epitope complex in autoimmune disease.

Thymic selection of the human T cell receptor V beta repertoire in SCID-hu mice.

Implantation of pieces of human fetal liver and thymus into SCID mice results in the development of a human thymus-like organ, in which sustained lymphopoiesis is reproducibly observed. In this model, T cell development can be experimentally manipulated. To study the influence of thymic selection on the development of the human T cell repertoire, the T cell receptor (TCR) V beta gene repertoire of double-positive (CD4+CD8+) and single-positive (CD4+CD8- and CD4-CD8+) T cells was analyzed in the SCID-hu thymus using a multiprobe ribonuclease protection assay. TCR diversity in double-positive SCID-hu thymocytes was found to be comparable with that present in the thymus of the fetal liver donor, did not change with time, and was independent of the origin of the thymus donor. Thymic selection in SCID-hu thymus induces changes in V beta usage by the single-positive CD4+ or CD8+ T cells comparable with those previously reported for single-positive cells present in a normal human thymus. Finally, significant differences were observed in the V beta usage by CD4 or CD8 single-positive T cells that matured from genetically identical stem cells in different thymic environments. Collectively, these data suggest: first, that the generation of TCR diversity at the double-positive stage is determined by the genotype of the stem cells; and second, that polymorphic determinants expressed by thymic epithelium measurably influence the V beta repertoire of mature single-positive T cells.

Bacterial superantigens mediate T cell deletions in the mouse severe combined immunodeficiency-human liver/thymus model.

The ability to analyze T cell receptor (TCR) thymic repertoire shaping in humans by self and foreign ligands is hampered by the lack of suitable models. We recently documented that the mouse severe combined immunodeficiency (SCID)-human fetal liver/thymus model recapitulates the TCR V beta gene repertoire of human thymocytes. Here, we show that an exogenous superantigen, staphylococcal enterotoxin B, administered to such mice induces clonal deletions in both CD4+8- and CD8+4- cells involving the same human V beta clones that are selected in vitro by this toxin. This model, therefore, may allow comprehensive studies into the effects of microbial and other agents on human T cell thymic selection processes in a biologically relevant setting.

Loci predisposing to autoimmunity in MRL-Fas lpr and C57BL/6-Faslpr mice.

Background genes determine the incidence and severity of lymphoaccumulation and histopathologic manifestations of systemic autoimmunity in mice homozygous for the apoptosis-defective Faslpr mutation. By interval mapping of 274 F2 mice intercrossed between MRL-Faslpr (severe disease) and C57BL/6-Faslpr (minimal disease), four loci were identified with significant linkage to lymphadenopathy and/ or splenomegaly on chromosomes 4, 5, 7, and 10, which were named lupus in (MRL-Faslpr x B6-Faslpr)F2 cross1-4 (Lmb1-4), respectively. Lmb1, -2, and -3 were also linked to the production of anti-dsDNA antibodies, but not glomerulonephritis, whereas Lmb4 was associated with glomerulonephritis. Lmb2, -3, and -4 were inherited from the MRL background, but interestingly, Lmb1 was derived from the C57BL16-Faslpr. Nevertheless, each locus, regardless of the strain of origin, appeared to act in an additive manner, although certain combinations were more effective. Only a single suggestive locus on chromosome 1 could be correlated with arthritis. The identification of loci with highly significant linkage to disease manifestations in Faslpr strains will make it possible to map and clone new genetic defects contributing to autoimmunity.

T cell receptor biases and clonal proliferations among lung transplant recipients with obliterative bronchiolitis.

Obliterative bronchiolitis (OB) is the most serious late complication of lung transplantation, but the pathogenesis of this disorder has not been elucidated. We sought evidence that OB is mediated by a cellular immunologic response by characterizing T cell antigen receptor beta-chain variable gene (TCRBV) repertoires in lung allograft recipients. Expression levels of 27 TCRBV among recipients were determined by multiprobe RNase protection assay after PCR amplification. In comparison to recipients with no evidence of rejection (n = 9), the PBL TCRBV repertoires of OB subjects (n = 16) exhibited more frequent expansions (16 vs. 9% of all measured TCRBV, P < 0.02), and the magnitudes of these abnormalities were greater (8.2 +/- 0.8 vs. 4.5 +/- 0.3 SD from mean normal values, P < 0.01). TCRBV sequencing showed these expansions were composed of clonal or oligoclonal populations. Thus, T cell responses in the recipients are marked by highly selective clonal expansions, presumably driven by indirect recognition of a limited number of immunodominant alloantigens. These processes are exaggerated among allograft recipients with OB, implying that cognate immune mechanisms are important in the pathogenesis of the disorder. Furthermore, the prominence of finite, distinct TCR phenotypes raise possibilities for development of novel diagnostic modalities and targeted immunotherapies for OB and other manifestations of chronic allograft rejection.

Treatment of murine lupus with cDNA encoding IFN-gammaR/Fc.

IFN-gamma, a pleiotropic cytokine, is a key effector molecule in the pathogenesis of several autoimmune diseases, including lupus. Importantly, deletion of IFN-gamma or IFN-gammaR in several lupus-predisposed mouse strains resulted in significant disease reduction, suggesting the potential for therapeutic intervention. We evaluated whether intramuscular injections of plasmids with cDNA encoding IFN-gammaR/Fc can retard lupus development and progression in MRL-Fas(lpr) mice. Therapy significantly reduced serum levels of IFN-gamma, as well as disease manifestations (autoantibodies, lymphoid hyperplasia, glomerulonephritis, mortality), when treatment was initiated at the predisease stage, particularly when IFN-gammaR/Fc expression was enhanced by electroporation at the injection site. Remarkably, disease was arrested and even ameliorated when this treatment was initiated at an advanced stage. This therapy represents a rare example of disease reversal and makes application of this nonviral gene therapy in humans with lupus (and perhaps other autoimmune/inflammatory conditions) highly promising.

Suggestive evidence for association of human chromosome 18q12-q21 and its orthologue on rat and mouse chromosome 18 with several autoimmune diseases.

Some immune system disorders, such as type 1 diabetes, multiple sclerosis (MS), and rheumatoid arthritis (RA), share common features: the presence of autoantibodies and self-reactive T-cells, and a genetic association with the major histocompatibility complex. We have previously published evidence, from 1,708 families, for linkage and association of a haplotype of three markers in the D18S487 region of chromosome 18q21 with type 1 diabetes. Here, the three markers were typed in an independent set of 627 families and, although there was evidence for linkage (maximum logarithm of odds score [MLS] = 1.2; P = 0.02), no association was detected. Further linkage analysis revealed suggestive evidence for linkage of chromosome 18q21 to type 1 diabetes in 882 multiplex families (MLS = 2.2; lambdas = 1.2; P = 0.001), and by meta-analysis the orthologous region (also on chromosome 18) is linked to diabetes in rodents (P = 9 x 10(-4)). By meta-analysis, both human chromosome 18q12-q21 and the rodent orthologous region show positive evidence for linkage to an autoimmune phenotype (P = 0.004 and 2 x 10(-8), respectively, empirical P = 0.01 and 2 x 10(-4), respectively). In the diabetes-linked region of chromosome 18q12-q21, a candidate gene, deleted in colorectal carcinoma (DCC), was tested for association with human autoimmunity in 3,380 families with type 1 diabetes, MS, and RA. A haplotype ("2-10") of two newly characterized microsatellite markers within DCC showed evidence for association with autoimmunity (P = 5 x 10(-6)). Collectively, these data suggest that a locus (or loci) exists on human chromosome 18q12-q21 that influences multiple autoimmune diseases and that this association might be conserved between species.

Crystal structure of a peptide complex of anti-influenza peptide antibody Fab 26/9. Comparison of two different antibodies bound to the same peptide antigen.

The three-dimensional structure of the complex of a second anti-peptide antibody (Fab 26/9) that recognizes the same six-residue epitope of an immunogenic peptide from influenza virus hemagglutinin (HA1; 75-110) as Fab 17/9 with the peptide has been determined at 2.8 A resolution. The amino acid sequence of the variable region of the 26/9 antibody differs in 24 positions from that of 17/9, the first antibody in this series for which several ligand-bound and free structures have been determined and refined. Comparison of the 26/9-peptide with the 17/9-peptide complex structures shows that the two Fabs are very similar (r.m.s.d. 0.5 to 0.8 A) and that the peptide antigen (101-107) has virtually the same conformation (r.m.s.d. 0.3 to 0.8 A) when bound to both antibodies. A sequence difference in the 26/9 binding pocket (L94; His in 26/9, Asn in 17/9) results in an interaction with a bound water molecule that is not seen in the 17/9 structures. Epitope mapping shows that the relative specificity of 26/9 and 17/9 antibodies for individual positions of the peptide antigen are slightly different. Amino acid substitutions in the peptide, particularly at position SerP107, are tolerated to different extents by 17/9 and 26/9. Structural and sequence analysis suggests that amino acid differences near the peptide-binding site are responsible for altering slightly the specificity of 26/9 for three peptide residues and illustrates how amino acid substitutions can modify antibody-antigen interactions and thereby modulate antibody specificity.

Quantitative polymerase chain reaction analysis reveals marked overexpression of interleukin-1 beta, interleukin-1 and interferon-gamma mRNA in the lymph nodes of lupus-prone mice.

The nature of the stimuli driving autoantibody production in systemic lupus erythematosus (SLE) is unclear, but cytokines are believed to play an important role. Since cytokines primarily appear to act locally at the tissue level, we analysed mRNA expression of several cytokines (IL-1 alpha, IL-1 beta, IL-2, IL-4, IL-5, IL-6, IL-10, IFN gamma, TNF alpha, TNF beta and TGF beta 1) in the lymph nodes of lupus-prone mice, in models of early onset disease. We constructed a multispecific competitor fragment that allowed quantification of these cytokine transcripts by competitive PCR assay. The results reveal considerable overexpression of IL-1 beta, IL-10 and IFN gamma transcripts in SLE-prone MRL-lpr/lpr (MRL/l) and BXSB male (BXSBm) mice, but with some strain differences. IFN gamma was most markedly augmented in MRL/l mice (in some cases over 100-fold greater than control mice), IL-1 beta was most severely overexpressed in BXSBm mice while IL-10 was equally increased in both strains. In addition, TGF beta 1 expression was moderately elevated in the lymph nodes of BXSBm (but not MRL/l) mice. We found no abnormality in the expression of the other cytokines. Cytokine transcript levels were only slightly altered at 4 weeks of age, but were elevated from 10 to 22 weeks of age. The latter phase corresponds to a period where lupus-like disease escalates, resulting in frequent mortality. Interestingly, our results do not reveal a clear Th1 or Th2 cytokine expression pattern in these lupus-prone mice. IL-1 beta, IFN gamma and IL-10 are pleiotropic cytokines with pro-inflammatory and B-cell stimulatory effects. These results point to certain cytokines as potential targets for immunotherapy in lupus.

Expression of protein-tyrosine phosphatases in the major insulin target tissues.

Protein-tyrosine phosphatases (PTPs) are key regulators of the insulin receptor signal transduction pathway. We have performed a detailed analysis of PTP expression in the major human insulin target tissues or cells (liver, adipose tissue, skeletal muscle and endothelial cells). To obtain a representative picture, all tissues were analyzed by PCR using three different primer sets corresponding to conserved regions of known PTPs. A total of 24 different PTPs were identified. A multiprobe RNase protection assay was developed to obtain a semiquantitative measure of the expression levels of selected PTPs. Surprisingly, PTP-LAR, previously suggested to be a major regulator of the insulin receptor tyrosine kinase, was expressed in extremely low levels in skeletal muscle, whereas the related receptor-type PTP-sigma and PTP-alpha were expressed in relatively high levels in all four tissues. The low levels of LAR PTP mRNA in skeletal muscle were further confirmed by Northern blot analysis.

Genetic studies in systemic autoimmunity and aging.

The etiopathogenesis of systemic lupus erythematosus remains an enigma that will probably not be solved until the genetic basis for susceptibility is defined. Through genomewide searches, we have provided a foundation for this by identifying and characterizing loci predisposing to specific disease traits in four major lupus-susceptible mouse strains. Further ongoing work that includes the study of interval-specific congenic lines and precise mapping of loci should lead to identification of the corresponding genes and elucidation of processes critical for disease pathogenesis. Another important area of investigation is the study of cell-cycle and apoptosis genes in systemic autoimmunity and aging. Based on earlier work, we proposed that the characteristic overexpansion of memory phenotype cells in these conditions may be owing to replicative senescence. Understanding the molecular mechanisms that regulate the generation of these cells may permit selective manipulations to control this process. Other areas of investigation that we are actively engaged in are the role of T cell receptor repertoire in disease and the definition of cellular genes affected by infection with human immunodeficiency virus.

Genetics of systemic autoimmunity in mouse models of lupus.

Systemic lupus erythematosus (SLE) is inherited as a complex polygenic trait, involving genetic, environmental and stochastic factors. Although definition of these etiologic processes has been elusive, solid progress has been made toward elucidating the genetic basis for susceptibility. Herein, we summarize our genome wide mapping effort that has defined loci for component phenotypes for lupus-prone NZB, NZW, MRL-Fas(lpr) and BXSB strains. With this framework in place, identification of the specific genetic alterations and mechanisms is now proceeding through the generation of interval congenic lines, precise mapping and screening of candidate genes. In addition to this approach, transgenic and gene knockout studies have begun to identify genes that can induce or modify autoimmunity in nonautoimmune and lupus-prone background mice, including studies by us and others on Th1 and Th2 cytokine genes in lupus. It is apparent that a diversity of genes and mechanisms can independently or in combination promote systemic autoimmunity in mice. This complexity, which is also observed in human lupus, emphasizes the importance of using experimental and less complex mouse models to define these processes, a tactic that has already yielded new insights. With current technologies and the anticipated definition of mammalian genomes, identification of genes predisposing to lupus and elucidation of processes critical for disease pathogenesis appear within grasp.

Xenobiotic acceleration of idiopathic systemic autoimmunity in lupus-prone bxsb mice.

The diverse genetic backgrounds of lupus-prone murine models, which produce both quantitative and qualitative differences in disease expression, may be a valuable resource for studying the influence of environmental exposure on autoimmune disease in sensitive populations. We tested this premise by exposing autoimmune-prone BXSB and the nonautoimmune C57BL/6 mice to the heavy metal mercury. Although both strains express a nonsusceptible H-2 haplotype, exposure to mercury accelerated systemic autoimmunity in both male and female BXSB mice, whereas the C57BL/6 mice were resistant. The subclasses of antichromatin antibodies elicited in BXSB mice by mercury exposure were more consistent with the predominant Th1-type response of idiopathic disease than with the Th2-type response found in mercury-induced autoimmunity (HgIA). The appearance and magnitude of both humoral and cellular features of systemic autoimmunity correlated with the mercury dose. Furthermore, environmentally relevant tissue levels of mercury were associated with exacerbated systemic autoimmunity. These studies demonstrate that xenobiotic exposure can accelerate spontaneous systemic autoimmunity, and they support the possibility that low-level xenobiotic exposure enhances susceptibility to systemic autoimmunity in genetically susceptible individuals.

Lupus-prone mice as models to study xenobiotic-induced acceleration of systemic autoimmunity.

The linkage between xenobiotic exposures and autoimmune diseases remains to be clearly defined. However, recent studies have raised the possibility that both genetic and environmental factors act synergistically at several stages or checkpoints to influence disease pathogenesis in susceptible populations. These observations predict that individuals susceptible to spontaneous autoimmunity should be more susceptible following xenobiotic exposure by virtue of the presence of predisposing background genes. To test this possibility, mouse strains with differing genetic susceptibility to murine lupus were examined for acceleration of autoimmune features characteristic of spontaneous systemic autoimmune disease following exposure to the immunostimulatory metals nickel and mercury. Although NiCl(2) exposure did not exacerbate autoimmunity, HgCl(2) significantly accelerated systemic disease in a strain-dependent manner. Mercury-exposed (NZB X NZW)F1 mice had accelerated lymphoid hyperplasia, hypergammaglobulinemia, autoantibodies, and immune complex deposits. Mercury also exacerbated immunopathologic manifestations in MRL+/+ and MR -lpr mice. However, there was less disease acceleration in lpr mice compared with MRL+/+ mice, likely due to the fact that environmental factors are less critical for disease induction when there is strong genetic susceptibility. Non-major histocompatibility complex genes also contributed to mercury-exacerbated disease, as the nonautoimmune AKR mice, which are H-2 identical with the MRL, showed less immunopathology than either the MRL/lpr or MRL+/+ strains. This study demonstrates that genetic susceptibility to spontaneous systemic autoimmunity can be a predisposing factor for HgCl(2)-induced exacerbation of autoimmunity. Such genetic predisposition may have to be considered when assessing the immunotoxicity of xenobiotics. Additional comparative studies using autoimmune-prone and nonautoimmune mice strains with different genetic backgrounds will help determine the contribution that xenobiotic exposure makes in rendering sensitive populations susceptible to autoimmune diseases.

The pathogenesis of autoimmunity in New Zealand mice.

OBJECTIVE: New Zealand mice were the first spontaneous animal model of human systemic lupus erythematosus (SLE). Since their initial discovery in 1959, studies of these mice have provided insights into the immunopathogenesis and genetics of lupus and have had a substantial impact on our understanding of autoimmunity. METHODS: We extensively reviewed published data for the past 40 years, including work in cellular immunology and molecular biology, to provide new information on the role of lymphoid subpopulations, cytokines, costimulatory molecules, apoptosis, and genetic susceptibility in the natural history of immunopathology in murine lupus. RESULTS: Genetic factors constitute the most important contribution to autoimmunity in New Zealand mice, and specific major susceptibility loci have been described. In addition, there is evidence for a pluripotent stem cell defect, which has implications for developmental and functional defects of T and B cells. The end result of these defects is a breakdown of self-tolerance and production of autoantibodies. Further studies will undoubtedly shape our understanding of this murine model and provide the basis for novel diagnostic and therapeutic approaches in humans. CONCLUSIONS: The advent of molecular biology, including the use of monoclonal antibody therapy in New Zealand mice, has been instrumental in our understanding of the loss of self-tolerance in SLE. Finally, identification of genetic susceptibility loci in the murine system has also led to important comparable studies in humans with SLE. RELEVANCE: The observations in New Zealand mice are of particular importance to systemic lupus erythematosus (SLE).

A ribosomal protein of Yersinia pseudotuberculosis having partial epitope identity with HLA-B27.

The phenotype HLA-B27 is common in patients who develop reactive arthritis after having an infection. One hypothesis concerning the pathogenesis of reactive arthritis is that molecular mimicry between HLA-B27 and certain bacterial components might be involved. It is known that an infection with Yersinia is commonly associated with reactive arthritis in B27 positive patients. Therefore, we were interested to investigate whether cross-reactivity between Yersinia and HLA-B27 exists. A gene library of Yersinia pseudotuberculosis was created in the plasmid vector pUC13. One of the resulting clones contained a gene encoding an intracytoplasmic protein that seems to have partial epitope identity with HLA-B27. It reacted in western blot. ELISA and immunoprecipitation with three different HLA-B27 specific monoclonal and polyclonal antibodies of the IgG and IgM class. However DNA-sequencing of the cloned Yersinia gene and the predicted amino acid sequence revealed only a very remote similarity with HLA-B27 in the primary structure. Instead, an extremely high degree of similarity with the ribosomal protein L4 of the S10 operon of Escherichia coli was identified indicating that the protein encoded by the cloned Y. pseudotuberculosis gene is a corresponding ribosomal protein.

T-cell receptor genes in autoimmunity.

T cells are primary participants in the pathogenesis of the MHC-dependent autoimmune diseases, and therefore, evidence for association of TCR V-gene repertoires with such disorders has been actively sought. With very few exceptions, no clear-cut evidence for correlation of particular RFLP-defined V-C-region genomic polymorphisms with autoimmune disease predisposition has thus far been demonstrated. With regard to TCR V-gene repertoires engaged in responses to autoantigens, restricted use of certain V beta and V alpha genes in response to myelin basic protein has been documented in animal models. In many spontaneous and experimentally induced animal and human autoimmune diseases, however, the picture is far from clear. Although dominance of certain TCR V genes has been noted, the clonal restrictions are not absolute; they differ from one study to another and from one patient to another. Such variations may be caused by MHC allele-dependent determinant selection mechanisms, secondary T-cell infiltrates in inflammatory sites, different patient populations and stages of disease, or the involvement of different pathogens that, nevertheless, lead to the same clinical entity. Overall, the results indicate that efforts to intervene therapeutically in autoimmune diseases by vaccination with modified T-cell clones, V region-synthetic peptides, or TCR blocking analogues may not be easily applicable. Further studies on the characterization of the specific antigens involved in autoimmune disease pathogenesis is required in order to accurately address the issue of TCR utilization in autoimmune diseases.

An animal model to study serum immunoglobulin response to infection by Yersinia enterocolitica.

Using an Elisa method, we tested whether the serum immunoglobulin response of CBA/H mice, orally infected by a serotype 03 strain of Yersinia enterocolitica was of sufficient magnitude to serve as an experimental model. We found that the dose of bacteria administered was important. At a dose of 10(10)-10(12) bacteria per mouse, easily detectable IgM, IgG and IgA antibody titers could be obtained. At 10(8) bacteria per mouse, although diarrhea occurred and Yersinia was shed into the stool, the antibody titers were minimal.