Divergent T cell receptor gamma repertoires in rheumatoid arthritis monozygotic twins

p205 is a major target of autoreactive T cells in rheumatoid arthritis

OBJECTIVE

The p205 autoantigen and interleukin-2 (IL-2) function synergistically to stimulate T lymphocytes from patients with rheumatoid arthritis (RA), and a p205-derived amino acid sequence is identical to an immunoglobulin sequence located within a domain that is reactive with rheumatoid factors (RF). This study was conducted to analyze in detail the T cell immune response against p205 and to investigate whether immunity to p205 may play a role in T cell-mediated immunopathology in active RA.

METHODS

Cibachron blue, protein A-Sepharose, and gel filtration on Sephacryl were used successively to enrich p205 from synovial fluid (SF). T lymphocytes from RA patients were isolated from the peripheral blood (PB), lymph nodes, and SF, and p205 and peptides derived from known sequences were assessed by T cell proliferation assays in the presence of IL-2.

RESULTS

P205-specific proliferation of T cells was observed in PB as well as in SF. When p205 was isolated from RA SF, proliferation of RA T cells peaked on day 3. With p205 purified from SF from trauma patients, there was a significant shift of the maximum T cell proliferation to day 8. T cells were of CD4 or CD8 phenotype, and B cells did not proliferate to a significant degree. The T cell response to p205 was always higher for SF mononuclear cells (SFMC) compared with PBMC (P < 0.001). In 1 RA patient who underwent repeated leukapheresis, this led to a reproducible decline in p205-specific T cell proliferation to control levels. PB T cells specifically proliferating in response to p205 were detected in 20 of 32 RA patients (63%). Of 26 patients with other inflammatory rheumatic diseases, only 1 showed a minor response to p205, while normal donors did not demonstrate a significant T cell proliferation. A synthetic p205-derived peptide, with an amino acid sequence identical to an immunoglobulin sequence located in the area where RF binds, was reactive with T cells from RA patients.

CONCLUSION

P205 appears to be a major target of autoreactive T cells in RA. P205-specific T cells are primed and more abundant at the site of inflammation. As a T cell target in RA, p205 may well be an antigen involved in the initiation of RF production.

T cell receptor repertoire in rheumatoid arthritis

CD4+ T cells are a major component of the inflammatory infiltrate in rheumatoid synovitis. Within synovial lesions, clonal CD4+ T cell populations are detectable, supporting the notion of an antigen specific recognition even in the joint. In general, the clonal size of individual T cell clones is small and does not lead to a marked distortion of the synovial T cell receptor (TCR) repertoire. Comparison of TCR sequences derived from different patients has not provided evidence for common sequences. Either multiple antigens are recognized or the TCR repertoire is sufficiently plastic with a multitude of different TCR structures responding to the same antigen(s). However, within one individual, the repertoire of clonal T cell populations is restricted. Identical T cell clones can be identified in different joints and at different timepoints of the disease, emphasizing that the spectrum of antigens recognized is conserved over time and that the T cell response pattern is not subject to evolution. Characterization of antigens involved in the latter stages of the disease may thus provide critical information on disease-initiating events. Recent data have led to the new concept that the role of T cells in rheumatoid arthritis (RA) is not limited to synovial inflammation. Evidence has been provided that the premorbid TCR repertoires of RA patients and normal controls can be distinguished. The T cell repertoire in RA patients is prone to recognize certain microbial products and autoantigens. The selection of this response pattern can only partially be attributed to the disease associated HLA-DRB1 alleles. Additional factors common in RA patients but not in HLA-DR matched control individuals seem to be important in shaping the TCR repertoire. Furthermore, the repertoire of mature T cells in RA patients is characterized by oligoclonality which involves T cells in the peripheral blood compartment. Possibly, these clonal T cell populations react to widespread autoantigens, raising the possibility that RA patients have a defect in controlling peripheral tolerance and an anomaly of lymphoproliferation. In contrast to joint residing CD4+ T cells, expanded clonotypes isolated from the blood of different patients have been described to share TCR beta chain structures. How these characteristic features of the global TCR repertoire in RA patients translate into mechanisms of disease remains to be elucidated.

The human immunoglobulin V(H) gene repertoire is genetically controlled and unaltered by chronic autoimmune stimulation

The factors controlling immunoglobulin (Ig) gene repertoire formation are poorly understood. Studies on monozygotic twins have helped discern the contributions of genetic versus environmental factors on expressed traits. In the present experiments, we applied a novel anchored PCR-ELISA system to compare the heavy chain V gene (V(H)) subgroup repertoires of mu and gamma expressing B lymphocytes from ten pairs of adult monozygotic twins, including eight pairs who are concordant or discordant for rheumatoid arthritis. The results disclosed that the relative expression of each Ig V(H) gene subgroup is not precisely proportional to its relative genomic size. The monozygotic twins had more similar IgM V(H) gene repertoires than did unrelated subjects. Moreover, monozygotic twins who are discordant for RA also use highly similar IgM V(H) gene-subgroup repertoires. Finally, the V(H) gene repertoire remained stable over time. Collectively, these data reveal that genetic factors predominantly control V(H) gene repertoire formation.

Rheumatoid arthritis as a bone marrow disorder

Both the concept of rheumatoid arthritis (RA) as an autoimmune process restricted to joints and the major role of T cells in its pathogenesis have been challenged in the literature. Fibroblastlike and macrophagelike synoviocytes play an important role in RA pannus, and these cells originate in or have their counterpart in bone marrow (BM). Yet the B cell autoimmunity characteristic of RA occurs early, and synovial tissue, like BM, favors the B cell response. Because BM is abnormal in RA, and because germinal centers are unique to RA synovium, RA could be regarded as a disorder of the microenvironments able to sustain B cell response. In fact, RA could even begin in BM, with its onset facilitated by stem cell abnormalities. Moreover, most viruses suspected of playing a role in RA share a BM tropism. This may explain why RA frequently overlaps with other autoimmune disorders and benign lymphoproliferations, such as large granular T lymphocytosis. Because remissions from RA have been reported after BM transplantation, careful studies of the rheumatological outcome of RA patients undergoing such therapeutic procedures are needed. Although RA is a complex process, it can be considered initially as a stem cell disorder requiring treatment similar to that administered to transplant patients. Animal models have provided convincing evidence for these assumptions.

Analysis of immunoglobulin VH gene repertoire by an anchored PCR-ELISA

We developed a novel technique to analyze the relative concentration of the expressed immunoglobulin (Ig) VH genes using an enzyme-linked immunosorbent assay (ELISA). Expressed Ig cDNA are amplified via anchored PCR and then subjected to a "nested PCR" reaction that attaches biotin to the 5' end of the antisense strand. This allows us to tether the antisense strand of PCR products onto avidin-coated ELISA plates. Digoxigenin-labeled oligonucleotides specific for the leader sequence sense strand of each major Ig VH gene subgroup are used to probe the plate-tethered, alkaline-denatured, and single-stranded antisense cDNA. Bound probes then are detected with alkaline-phosphatase-conjugated anti-digoxigenin antibodies. Using this method, we assessed the distribution of Ig VH genes used by IgM-expressing blood B cells of normal adults. We found the predominant subgroup is VH3, representing approximately half (range 41-59%) of the expressed IgM repertoire. The next largest subgroups used are VH4 (19-23%), VH1 (15-17%), and VH5 (7-11%). The VH2, VH6, and VH7 subgroups each constitute less than 3% of the expressed IgM repertoire. These results agree with those obtained using traditional and more laborious methods that analyze the distribution of Ig clones in cDNA libraries. In addition, we find that this method compares favorably in sensitivity and specificity to more conventional techniques for assessing the clonality of blood or tissue B-cell populations. This rapid and nonradioactive method should have utility for assessing the Ig repertoires expressed by normal, autoimmune, or neoplastic B-cell populations.

T cell receptor usage in autoimmune disease

Activated T-cells are believed to play a critical role in the pathogenesis of autoimmune disease. In experimental allergic encephalomyelitis (EAE), an animal model resembling human multiple sclerosis (MS), there is evidence that T cells reactive to myelin basic protein mediate an inflammatory response within the central nervous system leading to demyelination. Furthermore, encephalitogenic T cells express TCR with highly restricted V gene usage and consequently specific forms of immunotherapy directed against V gene products have been successful in preventing and treating EAE. These findings prompted studies into the analysis of TCR repertoire expression in human autoimmune diseases in an attempt to identify the TCR usage of autoreactive and potentially pathogenic T cells. However, this has proved difficult as the autoantigens that drive the T cell response in most human autoimmune disorders are unknown. This review examines the data that have accumulated over the past few years on TCR usage in human autoimmune diseases and is focused largely on rheumatoid arthritis and MS.

Diverse T cell receptor beta gene usage by infiltrating T cells in the lacrimal glands of Sjögren's syndrome

Sjögren's syndrome (SS) is an autoimmune disease characterized by T cell infiltration into the salivary and lacrimal glands (LG). Previous studies on T cell receptor (TCR) usage in the minor salivary glands (SG) have yielded controversial results. We studied TCR beta gene usage of the T cells infiltrating to LG, which is the other major target organ of SS. Total RNA was extracted from fresh LG and SG biopsy samples, and peripheral blood mononuclear cells from five SS patients, and converted to cDNA. TCR V beta gene repertoire was then assessed with quantitative polymerase chain reaction (PCR) assay. Oligoclonality was studied by sequencing V-D-J junctional regions of the PCR products. The TCR V beta gene usage in LG was diverse in every patient irrespective of disease duration, and similar to that of peripheral lymphocytes from a corresponding patient. The junctional region sequences of over-expressed V beta families in LG T cells were heterogeneous. We did not find any identical clones shared by LG, SG and peripheral blood. These results showed that the infiltrating T cells in LG of SS patients are polyclonal, and LG and SG do not share the same dominant T cell clonotypes. These suggest that TCR-targeted disease manipulation may have a limited effect on SS.

Mechanisms underlying the formation of the T cell receptor repertoire in rheumatoid arthritis

The contributions of germline-encoded T cell receptor segments and of HLA-DR polymorphisms in shaping the repertoire of human CD4+ CD45RO- T cells were investigated in healthy unrelated individuals and in patients with rheumatoid arthritis, an HLA-DRB1 04-associated disease. By comparing frequencies of V beta-J beta combinations, healthy individuals segregated into independent clusters, which strongly correlated with the HLA-DRB1 allele expression. The repertoire fingerprint imposed by the HLA-DRB1 alleles involved only a selected group of J beta elements, whereas the distribution of the other J beta segments was HLA independent. The HLA-restricted J beta elements are characterized by a Gly-Pro-Gly sequence within the conserved Phe-Gly-X-Gly motif, which induces rigidity in an otherwise more flexible protein backbone. The T cell receptor repertoire distinguished patients with RA from healthy HLA-DR-matched individuals, suggesting that patients share a selection mechanism that significantly distorts the composition of the T cell receptor repertoire.

Twin studies in rheumatic diseases

Twin studies attract both clinicians and geneticists because of the value of the twin method in helping unravel the genetic predisposition to diseases and the role of environment in their causation. In the field of rheumatology, there are many case reports on twins concordant or discordant for diseases. Interesting as such reports may be, very few generalizations can be made from them. The concordance rate among monozygotic (MZ) twins indicates the maximum level of genetic contribution. Based on studies of systematically compiled twin series, the concordance rate is about 15% for rheumatoid arthritis; the rate is probably of the same order of magnitude for systemic lupus erythematosus (SLE). The fine specificity of antinuclear antibodies of MZ twins at least one of whom is affected by SLE is very similar, despite somatic generation of immune diversity. Up to now, twin studies have provided little information on the role of environmental factors in rheumatic diseases. A notable exception is a case-control study of MZ twins discordant for smoking that reinforced the role of smoking as a cause of lumbar intervertebral disc degeneration.

T-cell antigen receptors in rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic disease of unknown etiology characterized by chronic inflammation mainly in the joints. Several lines of evidence suggest that T cells are involved in the pathogenesis of the disease. RA is associated with certain HLA-DR alleles. Studies analyzing T-cell receptor transcripts in RA have found biased or preferential usage of certain V alpha and/or V beta gene segments by T cells infiltrating the synovial membrane or extravasating into the synovial fluid compared to peripheral blood. In certain patients few T-cell antigen receptor (TCR) clones dominated the infiltrating T cells, suggesting that T cells from the synovial membrane or the synovial fluid comprise oligoclonal populations of T cells. However, other studies have found a polyclonal population of T cells. In interpreting these results the phase of the disease (early vs. late RA), the source of T cells and the limitations of the methods used in these studies should be taken into consideration. However, it appears that synovial T cells comprise oligoclonal populations of T cells and that there is a bias towards particular TCR gene segments, although a specific TCR gene segment in RA has not emerged.

Cellular immune mechanisms in rheumatoid arthritis and other inflammatory arthritides

Advances in molecular genetics, cellular immunology and microbiology have offered promise in unravelling the aetiopathogenesis of inflammatory arthritides such as rheumatoid arthritis and reactive arthritis. Such insights are challenging the orthodox view that these diseases are primarily autoimmune in nature, and should lead to exciting and novel therapeutic approaches.

The expressed T cell receptor V gene repertoire of rheumatoid arthritis monozygotic twins: rapid analysis by anchored polymerase chain reaction and enzyme-linked immunosorbent assay

Because of heterogeneity in the outbred human population, it has been difficult to determine the genetic factors that influence the expressed T cell receptor (TcR) repertoire in autoimmune diseases. To overcome this problem, we have developed a combination of anchored polymerase chain reaction (APCR) and enzyme-linked immunosorbent assay (ELISA) that can accurately assess TcR V gene frequencies in numerous clinical samples. The results are independent of amplification efficiency, and V gene usage can be readily analyzed with an ELISA plate reader and associated software. Using this method, the TcR V beta gene repertoires in peripheral lymphocytes from nine sets of identical twins, normal, concordant or discordant for rheumatoid arthritis (RA), were studied. The TcR V beta results were compared with TcR V gamma frequencies in the same specimens as determined by APCR-ELISA and cDNA sequence analysis. The results showed a marked similarity in the TcR V beta gene repertoires between identical twins, compared to unrelated subjects (p < 0.05) whether or not they were concordant or discordant for RA. In contrast, the TcR V gamma gene repertoires in the monozygotic twins differed as much as in controls. The data imply that (a) the human TcR V beta gene repertoire in peripheral blood is genetically controlled, whereas (b) the TcR V gamma gene repertoire is primarily influenced by environmental stimuli, and (c) RA causes no consistent change in TcR V beta repertoire of peripheral blood. The APCR-ELISA method, in the context of large-scale family and population studies, should facilitate a more precise delineation of the genetic factors that regulate human TcR V beta expression.