Joint-derived T cells in rheumatoid arthritis proliferate to antigens present in autologous synovial fluid

TCR repertoire sequencing identifies synovial Treg cell clonotypes in the bloodstream during active inflammation in human arthritis

OBJECTIVES

The imbalance between effector and regulatory T (Treg) cells is crucial in the pathogenesis of autoimmune arthritis. Immune responses are often investigated in the blood because of its accessibility, but circulating lymphocytes are not representative of those found in inflamed tissues. This disconnect hinders our understanding of the mechanisms underlying disease. Our goal was to identify Treg cells implicated in autoimmunity at the inflamed joints, and also readily detectable in the blood upon recirculation.

METHODS

We compared Treg cells of patients with juvenile idiopathic arthritis responding or not to therapy by using: (i) T cell receptor (TCR) sequencing, to identify clonotypes shared between blood and synovial fluid; (ii) FOXP3 Treg cell-specific demethylated region DNA methylation assays, to investigate their stability and (iii) flow cytometry and suppression assays to probe their tolerogenic functions.

RESULTS

We found a subset of synovial Treg cells that recirculated into the bloodstream of patients with juvenile idiopathic and adult rheumatoid arthritis. These inflammation-associated (ia)Treg cells, but not other blood Treg cells, expanded during active disease and proliferated in response to their cognate antigens. Despite the typical inflammatory-skewed balance of immune mechanisms in arthritis, iaTreg cells were stably committed to the regulatory lineage and fully suppressive. A fraction of iaTreg clonotypes were in common with pathogenic effector T cells.

CONCLUSIONS

Using an innovative antigen-agnostic approach, we uncovered a population of bona fide synovial Treg cells readily accessible from the blood and selectively expanding during active disease, paving the way to non-invasive diagnostics and better understanding of the pathogenesis of autoimmunity.

A circulating reservoir of pathogenic-like CD4+ T cells shares a genetic and phenotypic signature with the inflamed synovial micro-environment

Objectives

Systemic immunological processes are profoundly shaped by the micro-environments where antigen recognition occurs. Identifying molecular signatures distinctive of such processes is pivotal to understand pathogenic immune responses and manipulate them for therapeutic purposes. Unfortunately, direct investigation of peripheral tissues, enriched in pathogenic T cells, is often impossible or imposingly invasive in humans. Conversely, blood is easily accessible, but pathogenic signatures are diluted systemically as a result of the strict compartmentalisation of immune responses. In this work, we aimed at defining immune mediators shared between the bloodstream and the synovial micro-environment, and relevant for disease activity in autoimmune arthritis.

Methods

CD4⁺ T cells from blood and synovium of patients with juvenile idiopathic arthritis (JIA) were immunophenotyped by flow cytometry. The TCR repertoire of a circulating subset showing similarity with the synovium was analysed through next-generation sequencing of TCR β-chain CDR3 to confirm enrichment in synovial clonotypes. Finally, clinical relevance was established by monitoring the size of this subset in the blood of patients with JIA and rheumatoid arthritis (RA).

Results

We identified a small subset of circulating CD4⁺ T cells replicating the phenotypical signature of lymphocytes infiltrating the inflamed synovium. These circulating pathogenic-like lymphocytes (CPLs) were enriched in synovial clonotypes and they exhibited strong production of pro-inflammatory cytokines. Importantly, CPLs were expanded in patients with JIA, who did not respond to therapy, and also correlated with disease activity in patients with RA.

Conclusions

CPLs provide an accessible reservoir of pathogenic cells recirculating into the bloodstream and correlating with disease activity, to be exploited for diagnostic and research purposes.

Presence of a population of CD20+, CD38- B lymphocytes with defective proliferative responsiveness in the synovial compartment of patients with rheumatoid arthritis

OBJECTIVE

To provide a comprehensive understanding of the humoral immune response that takes place at the site of inflammation in rheumatoid arthritis (RA), we studied the functional properties of synovial B cells. In particular, the response to various modes of mitogen stimulation was investigated.

METHODS

Purified synovial fluid (SF) B cells were cultured in the presence of CD40 ligand (CD40L)-expressing fibroblasts and cytokines, activated T cells, or phorbol myristate acetate (PMA)/ionomycin. Proliferation was determined by 3H-thymidine incorporation. Release of intracellular calcium was studied by flow cytometry.

RESULTS

The inflamed joints of RA patients contained a population of CD20+,CD38- B cells with dramatically impaired mitogen responsiveness. Although the Ig-producing capacity was intact, these cells failed to proliferate in response to (a) CD40 in the presence of interleukin-2 (IL-2) and IL-10, (b) activated T cells, or (c) stimulation via the B cell receptor. Moreover, SF CD20+,CD38- B cells revealed a defective B cell receptor-induced Ca2+ influx, reminiscent of anergic B cells. Release of intracellular Ca2+ by ionomycin in the presence of the protein kinase C activator PMA did not restore the proliferative capacity. These findings indicate blockades in the proximal and distal intermediates involved in mitogen signaling.

CONCLUSION

SF CD20+,CD38- B cells have functionally impaired proliferative responsiveness. The capacity of these cells to respond to activation by the production of Ig supports the notion that these cells might serve as Ig-producing effector cells and, as such, play a role in the pathophysiology of RA.

Differential requirements for induction of total immunoglobulin and physiological rheumatoid factor production by human peripheral blood B cells

Rheumatoid factors (RFs) are autoantibodies directed against the Fc part of IgG. Considerable evidence exists that there are two classes of RFs, pathological and physiological. Whereas pathological RFs are associated with disease, physiological RFs are considered to be a normal component of the immune response. RF(+) precursor B cells present as part of the B cell repertoire of healthy individuals are held responsible for the production of physiological RFs, which is a transient phenomenon with a clear correlation with an initiating stimulus such as immunization or exposure to an infection. Here we demonstrate a difference in the regulatory control of total Ig and RF production by peripheral blood (PB) B cells of both healthy controls (HC) and patients with rheumatoid arthritis (RA). Highly purified B cells from HC and patients with RA were cocultured with T cells stimulated with immobilized anti-CD3 mAb. Similar to IgM production, IgM-RF production was shown to be dependent on CD40 cross-linking. However, activation of PB B cells in the CD40 system in the presence of IL-2, IL-4, IL-10, combinations of these cytokines or supernatant of anti-CD3-stimulated T cells failed to induce detectable IgM-RF, whereas total IgM production was considerable. From these results we conclude that conditions to activate physiological RF(+) B cells require additional contact besides CD40--CD40L interactions between T and B cells. Since the requirements for RF production were similar using PB B cells from HC and patients with RA it is suggested that the regulatory properties of RF(+) precursors in the PB B cell compartment is equal among these groups. Together, these results indicate that conditions for the induction of total Ig and physiological RFs are different.

Secretion of anti-citrulline-containing peptide antibody by B lymphocytes in rheumatoid arthritis

OBJECTIVE

To understand the regulation of anti-citrulline-containing peptide antibody (anti-CCP) production in rheumatoid arthritis (RA), production of anti-CCP by B cells derived from peripheral blood (PB), bone marrow (BM), and synovial fluid (SF) was examined.

METHODS

Purified PB and SF B cells were isolated by negative selection and then cultured in the absence or presence of L-CD40 ligand cells and interleukin-10 or anti-CD3-activated T cells. Total IgM and IgM-anti-CCP were detected after 14 days of culture by enzyme-linked immunosorbent assay. Enzyme-linked immunospot assays were performed to analyze the frequency of cells that spontaneously produced IgM-anti-CCP in BM and SF B cells.

RESULTS

IgM-anti-CCP autoantibodies were induced in PB B cells from healthy controls and RA patients following coculture with activated T cells or application of the CD40 activation system, whereas no production could be detected when PB B cells were cultured in the absence of a stimulus. SF and BM B cells from anti-CCP-seropositive RA patients, but not anti-CCP-seronegative patients, actively produced IgM-anti-CCP without stimulation. The frequency of spontaneous production of IgM-anti-CCP among the IgM-secreting cells ranged from 2.2% to 25%.

CONCLUSION

These results indicate the presence of B cell precursors for anti-CCP autoantibodies that are able to produce antibodies upon stimulation in the PB B cell repertoire of healthy controls and patients with RA. In contrast, B cells that actively secreted anti-CCP were specifically present in the BM and SF compartment of anti-CCP-seropositive RA patients. The local presence of anti-CCP-secreting cells in the inflamed joints provides evidence for an antigen-driven maturation of CCP-specific B cells at the site of inflammation in RA.

High concentration of soluble HLA-DR in the synovial fluid: generation and significance in "rheumatoid-like" inflammatory joint diseases

In the search for its role in inflammatory joint diseases, soluble HLA-DR (sHLA-DR) was quantitated in 72 synovial fluids (SF) by a newly established immunoenzyme assay. Unlike other soluble receptors which accumulated only moderately (sCD25, sCD4) or negligibly (sHLA class I, sCD8) in the SF, SF sHLA-DR levels exceeded serum levels by up to 3 orders of magnitude and varied disease dependently from "control" values (traumatic synovitis and osteoarthritis: 9.9 +/- 6.1 ng/ml). Clear-cut different SF sHLA-DR values in HLA-DR-associated "rheumatoid-like" (136.5 +/- 130.0 ng/ml) vs HLA-B27-associated "spondylarthropathy-like" arthritic forms (28.4 +/- 29.1 ng/ml) were most significant comparing oligoarticular juvenile chronic arthritis type I (147.6 +/- 112.6 ng/ml) and type II (3.3 +/- 1.1 ng/ml), thus offering a new classification marker. Also ex vivo, large amounts of sHLA-DR were released spontaneously by SF mononuclear cells and found to be related to the T-cell activation state. SF sHLA-DR may be shed in large complexes or micelles, as it eluted mainly at >450 kDa on gel filtration. Western blotting revealed that the majority of SF sHLA-DR consisted of full-length alpha- and beta-chains. Minor fractions of smaller sized antigens seemed to be generated by proteolytic cleavage rather than by alternative splicing, since only minute amounts of HLA-DRB mRNA lacking the transmembrane exon could be amplified by RT-PCR. Distinct forms of high-dose sHLA-DR, able to provoke rather than to suppress T-cell responses, are discussed as contributing to some HLA-DR disease association.

Cartilage-reactive T cells in rheumatoid synovium

Rheumatoid arthritis (RA) is an inflammatory polyarthritis genetically linked to HLA-DR4 and related haplotypes. RA synovial tissue is characterized by T cell infiltration and activation of macrophage-like cells, strongly implicating a T cell-antigen-presenting cell (APC) interaction in RA pathogenesis. To investigate the nature of the antigens driving the T cell response, synovial tissue was obtained from a patient with chronic RA and T cells were enriched. These T cells were stimulated by endogenous APC from the same synovial tissue. The T cell lines were subsequently evaluated for responsiveness to autologous APC and cartilage antigens. Specific proliferative responses to autologous APC which were enhanced by cartilage extract were seen. Immunomagnetic bead selection and RT-PCR was used to identify TCR alphabeta pairs which appeared to respond to antigen(s) in the cartilage extract. T cell clones derived from the same joint were shown to release IL-2 in response to the cartilage extract and expressed a related TCR. With these experiments we have shown direct evidence that autoreactive T cells are found within the inflamed rheumatoid synovium and, further, that the antigens driving these T cells are cartilage derived. Since the antigens recognized by these populations of T cells are found within cartilage our data provides evidence that RA pathology could be related to a self-driven autoimmune response to cartilage proteins.

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.

Structural motifs in rheumatoid T-cell receptors

The linkage of rheumatoid arthritis (RA) to HLA-DR haplotypes, high levels of HLA-DR expression, and T-cell infiltration in the joints, indicate a central role for the interaction of T-cell receptors (TCR) with antigen (Ag) + major histocompatibility complex (MHC) complexes in pathogenesis. Receptor analysis in RA has uncovered a restricted heterogeneity of TCR transcripts, suggesting an antigen-driven response. We analyzed the sequence and structural features of RA-associated TCRs in light of the recently published TCR crystal structures. The surface-exposed residues of the third complementarity-determining region (CDR3s) showed preferential use of certain amino acid residues when sequences derived from synovial fluid or tissue were compared with those derived from peripheral blood, particularly for alpha chains. Sequence alignment of oligoclonal synovial TCR CDR3s revealed groupings with similar CDR3 lengths and amino acid compositions, which suggests shared antigen recognition. Given the limitations of analyzing TCR sequences without knowing their structures, we developed several in vivo-activated synovial-tissue Vbeta17 + RA T-cell clones. Two Vbeta17/V alpha7 clones with different CDR3 sequences were analyzed by molecular modeling. Although distinct topologic features were seen, a central patch of residues with similar chemical and geometric characteristics was present in both. Electrostatic maps revealed similar binding surfaces of both alpha domains and central patches, with differences in the beta domains. This suggests that an alpha-domain-focused binding trajectory would allow shared antigen recognition by these TCRs. These studies support recognition of a limited diversity of Ag + MHC complexes by synovial RA TCRs.

TCRB clonotypes are present in CD4+ T cell populations prepared directly from rheumatoid synovium

The identification of clonal T cells at sites of inflammation is hampered by the large number of polyclonal T cells that nonspecifically accumulate. In this report, we combine the use of T cell sorting with spectratyping of the third complementarity determining region (CDR3) and direct sequence analysis to rapidly screen for and identify clonal expansions of T cells from synovial tissue specimens from patients with rheumatoid arthritis (RA). Initially, we used a polymerase chain reaction specific for the variable region gene of the T cell receptor beta chain (TCRBV) to compare the TCRBV repertoire expressed by CD4+ T cells from the peripheral blood and synovium of five patients with long-standing RA. Each patient had several TCRBV genes that were amplified to a greater degree from synovium. Extensive sequence analysis (n > 170) showed that each patient contained junctional sequences that occurred more than once, implying the presence of T cell clones within the starting CD4+ T cell population. To assess a more straightforward approach to identifying clones, six additional patients were recruited and CD4+, TCRBV2+ synovial T cells were positively selected and analyzed by CDR3 spectratyping. Bands deviating from a normal distribution were excised from the gel and sequenced directly. Clones were detected in half of the patients. These data are consistent with the possibility of an antigen-driven T cell response in RA that remains present in the setting of advanced disease.