Junctional region sequences of T-cell receptor beta-chain genes expressed by pathogenic anti-DNA autoantibody-inducing helper T cells from lupus mice: possible selection by cationic autoantigens

Urtica dioica agglutinin, a V beta 8.3-specific superantigen, prevents the development of the systemic lupus erythematosus-like pathology of MRL lpr/lpr mice

The V beta 8.3-specific superantigenic lectin Urtica dioica agglutinin (UDA) was used to delete the V beta 8.3+ T cells in MRL lpr/lpr mice. In contrast to the systemic lupus erythematosus-like pathology which progresses with age in the phosphate-buffered saline-injected MRL lpr/lpr controls, UDA-treated animals did not develop overt clinical signs of lupus and nephritis. The pathogenic T cell clones thus reside within the V beta 8.3+ T cell population, which includes an expanded T cell clone described previously. Finally, UDA alters the production of autoantibodies in a sex-dependent manner.

Nucleosomal peptide epitopes for nephritis-inducing T helper cells of murine lupus

Nucleosome-specific T helper (Th) cells provide major histocompatibility complex class II-restricted, cognate help to nephritogenic antinuclear autoantibody-producing B cells in lupus. However, the lupus Th cells do not respond when components of the nucleosome, such as free DNA or histones, are individually presented by antigen-presenting cells. Thus critical peptide epitopes for the pathogenic Th cells are probably protected during uptake and processing of the native nucleosome particle as a whole. Therefore, herein we tested 145 overlapping peptides spanning all four core histones in the nucleosome. We localized three regions in core histones, one in H2B at amino acid position 10-33 (H2B(10-33)), and two in H4, at position 16-39 (H4(16-39)) and position 71-94 (H4(71-94)), that contained the peptide epitopes recognized by the pathogenic autoantibody-inducing Th cells of lupus. The peptide autoepitopes also triggered the pathogenic Th cells of (SWR x NZB)F1 lupus mice in vivo to induce the development of severe lupus nephritis. The nucleosomal autoepitopes stimulated the production of Th1-type cytokines, consistent with immunoglobulin IgG2a, IgG2b, and IgG3 being the isotypes of nephritogenic autoantibodies induced in the lupus mice. Interestingly, the Th cell epitopes overlapped with regions in histones that contain B cell epitopes targeted by autoantibodies, as well as the sites where histones contact with DNA in the nucleosome. Identification of the disease-relevant autoepitopes in nucleosomes will help in understanding how the pathogenic Th cells of spontaneous systemic lupus erythematosus emerge, and potentially lead to the development of peptide-based tolerogenic therapy for this major autoimmune disease.

Hyperexpression of CD40 ligand by B and T cells in human lupus and its role in pathogenic autoantibody production

We investigated the role of the costimulatory molecules, CD40 and its ligand CD40L, in the pathogenesis of human SLE. In comparison to normal subjects or patients in remission, PBMC from active lupus patients had a 21-fold increase in the frequency of CD40L-expressing, CD4+T cells. However, the expression of CD40L induced in either lupus or normal T cells by mitogenic stimulation could be down-regulated equally well by CD40 molecules on autologous B cells. Active lupus patients also had a 22-fold increase in percentage of CD8+ T cells expressing CD40L, consistent with their unusual helper activity in SLE. Surprisingly, patients with active lupus had a 20.5-fold increase in B cells that spontaneously expressed high levels of CD40L, as strongly as their T cells. Although lupus patients in remission had low levels of CD40L+ cells in the range of normal subjects, mitogen-induced upregulation of CD40L expression in the T and B cells was markedly greater than normal, suggesting an intrinsic defect. A mAb to CD40L blocked significantly the ability of lymphocytes from lupus patients with active and established disease to produce the pathogenic variety of antinuclear autoantibodies in vitro, bolstering the possibility of anti-CD40L immunotherapy for lupus. Future studies on the hyperexpression of CD40L could elucidate a regulatory defect in the pathogenic T and B cells of lupus.

Heterogeneous T cell receptor V beta gene repertoire in murine interstitial nephritis

Anti-tubular basement membrane disease (alpha TBM) produces T cell-mediated interstitial nephritis in SJL/J mice following immunization with heterologous renal tubular antigen. Initial mononuclear infiltrates appear in vivo after six to eight weeks, with subsequent progression to renal fibrosis and endstage kidney disease. Cultured lymph node derived nephritogenic T cells from these mice react to a small epitopic region of the 3M-1 target antigen and share a common amino acid motif in their V beta CDR3 regions. We now have used RT-PCR to further characterize the renal expression of T cell receptor (TcR) V beta gene repertoires during the course of this disease. Individual kidneys with focal mononuclear infiltrates characteristic of early alpha TBM disease express up to three different TcR V beta genes; however, the same V beta genes are not found in all kidneys at the same early stage of injury. DNA sequencing of the V beta RT-PCR products reveals a heterogeneous population of VDJ recombinations and deduced CDR3 amino acid sequences. Our studies do not support TcR V beta region gene restriction in histologically-detectable alpha TBM disease, but are more consistent with a dynamic, organ-specific autoimmune disease, directed at multiple autoantigenic epitopes.

T cells in murine lupus: propagation and regulation of disease

MRL/Mp-lpr/lpr mice develop a spontaneous lupus syndrome, including hypergammaglobulinemia, autoantibodies, glomerulonephritis, and lymphadenopathy. To investigate the role of lymphocytes subsets in the pathogenesis of disease, lupus-prone MRL mice deficient in alpha beta T cells, gamma delta T cells, or both were generated. Mice deficient in alpha beta T cells developed a partially penetrant lupus syndrome, characterized by lymphadenopathy, elevated levels of class-switched immunoglobulins, an increased incidence of antinuclear antibodies, and immune deposits in kidneys which progressed to renal insufficiency over time. In comparison to wild type animals, gamma delta T cell-deficient animals developed an accelerated and exacerbated disease phenotype, characterized by accelerated hypergammaglobulinemia and enhanced autoantibody production and mortality. Repertoire analysis of these latter animals identified polyclonal expansion (V beta) of alpha beta CD4+ B220-cells. Mice lacking both alpha beta and gamma delta T cells failed to generate class-switched autoantibodies and immune complex renal disease. First, these findings demonstrate that murine lupus in the setting of Fas-deficiency does not absolutely require the presence of alpha beta T cells, and they also suggest that a significant basis for MRL/lpr disease, including renal disease, involves alpha beta T cell-independent, gamma delta T cell dependent, polyreactive B cell autoimmunity, upon which alpha beta T cell-dependent mechanisms aggravate specific autoimmune responses. Second, these data indicate that gamma delta T cells partake in the regulation of systemic autoimmunity, presumably via their effects on alpha beta CD4+ B220-T cells that provide B cell help. Finally, these results demonstrate that MRL/lpr B cells, despite their intrinsic abnormalities, cannot per se cause tissue injury without T cell help.

Mechanisms of the pathogenic autoimmune response in lupus: prospects for specific immunotherapy

A major step towards understanding the basic mechanism of systemic lupus erythematosus (SLE), the prototypic autoimmune disease that develops spontaneously, has been the identification of nucleosomes as a primary immunogen in this disease. The production of pathogenic autoantibodies in SLE results from an MHC class-II-restricted, cognate interaction between select populations of T helper cells and B cells that are specific for nucleosomal components. These observations pave the way for specific immunotherapy that blocks this pathogenic T and B cell interaction.

Structure and specificity of T cell receptors expressed by potentially pathogenic anti-DNA autoantibody-inducing T cells in human lupus

The production of potentially pathogenic anti-DNA autoantibodies in SLE is driven by special, autoimmune T helper (Th) cells. Herein, we sequenced the T cell receptor (TCR) alpha and beta chain genes expressed by 42 autoimmune Th lines from lupus patients that were mostly CD4+ and represented the strongest inducers of such autoantibodies. These autoimmune TCRs displayed a recurrent motif of highly charged residues in their CDR3 loops that were contributed by N-nucleotide additions and also positioned there by the recombination process. Furthermore, Th lines from four of the five patients showed a marked increase in the usage of the V alpha 8 gene family. Several independent Th lines expressed identical TCR alpha and/or beta chain sequences indicating again antigenic selection. 10 of these Th lines could be tested further for antigenic specificity. 4 of the 10 pathogenic anti-DNA autoantibody-inducing Th lines responded to the non-histone chromosomal protein HMG and two responded to nucleosomal histone proteins; all presented by HLA-DR molecules. Another Th line responded to purified DNA more than nucleosomes. Thus, these autoimmune Th cells of lupus patients respond to charged epitopes in various DNA-binding nucleoproteins that are probably processed and presented by the anti-DNA B cells they selectively help.

Molecular analysis of the helper T cell response in murine interstitial nephritis. T cells recognizing an immunodominant epitope use multiple T cell receptor V beta genes with similarities across CDR3

Anti-tubular basement membrane disease (alpha TBM disease) produces T cell-mediated interstitial nephritis in SJL mice after immunization with renal tubular antigen. Initial mononuclear infiltrates appear in vivo after several weeks, with the subsequent progression to renal fibrosis and end stage renal disease over many months. We have analyzed the fine specificity of the autoreactive helper T cell repertoire in alpha TBM disease through the isolation and characterization of a panel of CD4+ Th1 clones harvested after 1-2 wk from animals immunized to produce disease. All clones capable of mediating alpha TBM disease are directed towards a 14-residue immunodominant epitope (STMSAEVPEAASEA) contained within the target antigen, 3M-1. Evaluation of the T cell receptor (TCR) V beta repertoire used by these autoreactive T cells reveals the use of several V beta genes, but with some preference for V beta 14. Sequencing across the putative CDR3 region of the TCR beta chains suggests that common amino acids at the V beta(N)D beta junction and the D beta(N)J beta junction may contribute to the specific ability of these cells to recognize the immunodominant epitope.

The expansion of a CD4+ T cell population bearing a distinctive beta chain in MRL lpr/lpr mice suggests a role for the fas protein in peripheral T cell selection

MRL lpr/lpr mice suffer from a systemic lupus erythematosus-like autoimmune disease. The lpr mutation impairs the normal transcription of the fas message, the product of which mediates apoptosis and presumably the proper selection of T cells. We have found an early expansion of CD4+ T cells bearing a distinctive V beta 8.3-D beta 1.1-J beta 1.1 T cell receptor beta chain in the periphery of MRL lpr/lpr mice, which was not detected in MRL +/+ mice nor in the thymus of MRL lpr/lpr mice. Thus, since thymic selection is normal in MRL lpr/lpr mice, we propose that the lpr mutation results in defective negative selection at the periphery.

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.

Nucleosome: a major immunogen for pathogenic autoantibody-inducing T cells of lupus

Only a fraction (12%) of 268 "autoreactive" T cell clones derived from lupus-prone mice can selectively induce the production of pathogenic anti-DNA autoantibodies in vitro and accelerate the development of lupus nephritis when transferred in vivo. The CDR3 loops of T cell receptor beta chains expressed by these pathogenic T helper (Th) clones contain a recurrent motif of anionic residues suggesting that they are selected by autoantigens with cationic residues. Herein, we found that approximately 50% of these pathogenic Th clones were specific for nucleosomal antigens, but none of them responded to cationic idiopeptides shared by variable regions of pathogenic anti-DNA autoantibodies. Nucleosomes did not stimulate the T cells as a nonspecific mitogen or superantigen. Only the pathogenic Th cells of lupus responded to nucleosomal antigens that were processed and presented via the major histocompatibility class II pathway. Although the presentation of purified mononucleosomes to the Th clones could be blocked by inhibitors of endosomal proteases, neither of the two components of the nucleosomes--free DNA or histones by themselves--could stimulate the Th clones. Thus critical peptide epitopes for the Th cells were probably protected during uptake and processing of the nucleosome particle as a whole. The nucleosome-specific Th clones preferentially augmented the production of IgG autoantibodies to histone-DNA complex in vitro. In vivo, nucleosome-specific, CD4+ T cells were not detectable in normal mice, but they were found in the spleens of lupus-prone mice as early as 1 mo of age, long before other autoimmune manifestations. Immunization of young, preautoimmune lupus mice with nucleosomes augmented the production of autoantibodies and markedly accelerated the development of severe glomerulonephritis. Previously, crude preparations containing nucleosomes were shown by others to have polyclonal mitogenic activity for B cells from normal as well as lupus mice. Identification here of pure mononucleosome as a lupus-specific immunogen for the Th cells that selectively help the pathogenic anti-DNA autoantibody producing B cells of lupus could lead to the design of specific therapy against this pathogenic autoimmune response.

TH1 and TH2 cell antigen receptors in experimental leishmaniasis

The complexity and chronicity of parasitic infections have obscured the identification of biologically relevant antigens. Analysis of the T cell receptor repertoire used by mice infected with Leishmania major revealed the expansion of a restricted population of CD4+ cells. These cells expressed the V alpha 8-J alpha TA72, V beta 4 heterodimer in both progressive infection and protective immunity and across several major histocompatibility haplotypes. Thus, the same immunodominant parasite epitope drives the disparate outcomes of this infectious process, suggesting that candidate vaccine antigens selected by screening of immune individuals may be capable of exacerbating disease in genetically susceptible individuals.

A peptide derived from an autoantibody can stimulate T cells in the (NZB x NZW)F1 mouse model of systemic lupus erythematosus

OBJECTIVE

To assess the ability of peptides derived from anti-DNA to stimulate syngeneic T lymphocytes and influence lupus in (NZB x NZW)F1 (NZB/W) mice.

METHODS

We synthesized (by Geysen pin method) overlapping 12-mer peptides recapitulating the amino acid sequence of the VH region of a nephritogenic monoclonal IgG2a anti-DNA antibody (A6.1) from an NZB/W mouse. Splenic T cells were cultured with the peptides; multiple experiments assayed 12-mer and 16-mer peptides which contained a triple-base motif (KFKGK). We immunized 20-week-old NZB/W mice with the 12-mer and evaluated them for evidence of nephritis and for quantities of antibodies in plasma and glomeruli.

RESULTS

Three clusters of peptides caused proliferation of spleen cells from young, nonimmunized mice. Both the 12-mer FYNQKFKGKATL and the 16-mer GDTFYNQKFKGKATLT peptides stimulated purified T cells. The KXKXK motif occurs in 15% of murine Ig VH (NBRF protein database), compared with 100% (6 of 6) of NZB/W anti-DNA monoclonal antibody. Immunization with the 12-mer peptide increased plasma levels of IgG, anti-DNA, and immune complexes, and levels of anti-DNA in glomeruli; nephritis was accelerated.

CONCLUSION

NZB/W anti-DNA contain peptide sequences in their VH regions that stimulate self-T cells. At least one motif is frequent in NZB/W anti-DNA. If some activated T cells provide help, this mechanism may contribute to sustained up-regulation of autoantibodies in murine lupus.

Dissociation of autoaggression and self-superantigen reactivity

Self-superantigens have been described as products of endogenous retroviruses of the mouse ('minor lymphocyte stimulating loci') that are capable of interacting without prior processing with conserved domains of TCR V beta chains, causing the activation and deletion of most T cells expressing products of determined V beta gene families [1-4]. The fact that superantigens activate a far higher percentage of T cells (1-20%) than conventional, peptidic antigens (< 0.1%) provides the methodological advantage that the degree of clonal deletion may be measured by the analysis of the TCR repertoire using appropriate anti-V beta antibodies. Although much information on the spatio-temporal organization of repertoire-purging has been gathered by virtue of self-superantigens, serious doubts exist as to the possibility that such structures serve as pathogenetically relevant autoantigens. Thus, certain inbred mice spontaneously develop autoimmune diseases, although they bear T-cell repertoires that appear to be purged from self-superantigen-reactive V beta products. In addition, therapeutic interventions targeted to V beta gene products that are not specific for self-superantigens are successful in preventing disease development. The lack of correlation between superantigen-related V beta deletions and autoimmune disease development is substantiated in further models of murine autoimmunity. Based on these observations, we formulate the hypothesis that self-superantigen-reactive T cells are not involved in the development of autoimmune diseases.

Attenuation of autoimmune disease and lymphocyte accumulation in MRL/lpr mice by treatment with anti-V beta 8 antibodies

MRL-MP-lpr/lpr mice are afflicted by a severe systemic autoimmune disease that is aggravated by the lpr mutation resulting in the accumulation of phenotypically abnormal lpr cells (CD3+CD4-CD8-) in all lymphoid issues including hyperplastic lymph nodes. Given that products of the T cell receptor V beta 8 gene family are overrepresented among lpr cells, different schedules aimed at selectively decreasing the frequency of lpr cells were designed. First, continuous administration of the monoclonal antibody F23.1 (specific for V beta 8 products) resulted in a significant depletion of V beta 8+ cells and prevented the manifestation of lymph accumulation at the same time as it reduced the serological, clinical, and histopathological signs of autoimmune disease. Along the same line, administration of either F23.1 or two different anti-F23.1 anti-idiotypic antibodies to MRL/Mp-lpr/lpr mothers elicited, in the offspring, the production of antibodies sharing a recurrent idiotype with F23.1 and resulted in long-term amelioration of autoimmunity and lymphadenopathy. Thus, a strategy aimed at specifically reducing the frequency of a subset of lpr cells proved successful in mitigating the autoimmune process.