Yang, Hongyu

Background Rheumatoid arthritis (RA) is an HLA-DR associated disease with a pivotal role of T cells in the pathogenesis. The mechanisms underlying the HLA association and the generation of a synovial T-cell response are unclear. We have hypothesized that the selection of the primary T-cell repertoire is a predisposing factor for rheumatoid synovitis. Methods The repertoire of T-cell receptors (TCR) expressed by circulating naive CD4 + CD45RO − T cells was compared in 10 patients with RA, 11 HLA-DR matched normal donors and 10 mismatched normal donors by determining the frequencies of TCR BV-BJ combinations in 3 different BV gene segment families. Clonally expanded synovium-specific CD4 T cells were identified in 8 patients by TCR BV-BJ-specific PCR of purified T-cell subsets followed by size fractionation and sequencing of the PCR product. The TCR BV-BJ repertoires of naive peripheral T cells and of synovial clones were compared. Results The repertoires of naive circulating CD4 + CD45RO − T cells were different in RA patients and in HLA-DR matched and unmatched controls, suggesting HLA-DR as well as disease-specific features of T-cell selection. To test the disease relevance of the shifts in the naive repertoire, CD4 T cells undergoing joint-specific clonal expansion were identified. The usage of BV-BJ gene combinations in these synovium-specific clones was biased and significantly different from the expected distribution with a preference for combinations favored in the naive TCR repertoire of RA patients. Conclusions These data suggest that primary T-cell selection in RA patients is of functional importance for the generation of synovium-specific T-cell responses. The synovial repertoire is influenced by aberrations in the naive T-cell repertoire that might indicate a defect in thymic education with the selection of high-affinity self-reactive T cells in RA.

Abstract Fibroblast-like synoviocytes (FLS) from patients with rheumatoid arthritis elicit spontaneous proliferation of autologous T cells in an HLA-DR and CD47 costimulation-dependent manner. T cell costimulation through CD47 is attributed to specific interaction with thrombospondin-1 (TSP1), a CD47 ligand displayed on FLS. CD47 binding by FLS has broad biological impact that includes adhesion and the triggering of specific costimulatory signals. TSP1+ FLS are highly adhesive to T cells and support their aggregation and growth in situ. Long-term cultures of T cells and FLS form heterotypic foci that are amenable to propagation without exogenous growth factors. T cell adhesion and aggregate formation on TSP1+ FLS substrates are inhibited by CD47-binding peptides. In contrast, FLS from arthroscopy controls lack adhesive or T cell growth-promoting activities. CD47 stimulation transduces a costimulatory signal different from that of CD28, producing a gene expression profile that included induction of ferritin L chain, a component of the inflammatory response. Ferritin L chain augments CD3-induced proliferation of T cells. Collectively, these results demonstrate the active role of FLS in the recruitment, activation, and expansion of T cells in a CD47-dependent manner. Because TSP1 is abundantly expressed in the rheumatoid synovium, CD47-TSP1 interaction is proposed to be a key component of an FLS/T cell regulatory circuit that perpetuates the inflammatory process in the rheumatoid joint.

Background —Unstable angina (UA) is associated with systemic inflammation and with expansion of interferon-γ–producing T lymphocytes. The cause of T-cell activation and the precise role of activated T cells in plaque instability are not understood. Methods and Results —Peripheral blood T cells from 34 patients with stable angina and 34 patients with UA were compared for the distribution of functional T-cell subsets by flow cytometric analysis. Clonality within the T-cell compartment was identified by T-cell receptor spectrotyping and subsequent sequencing. Tissue-infiltrating T cells were examined in extracts from coronary arteries containing stable or unstable plaque. The subset of CD4 + CD28 null T cells was expanded in patients with UA and infrequent in patients with stable angina (median frequencies: 10.8% versus 1.5%, P <0.001). CD4 + CD28 null T cells included a large monoclonal population, with 59 clonotypes isolated from 20 UA patients. T-cell clonotypes from different UA patients used antigen receptors with similar sequences. T-cell receptor sequences derived from monoclonal T-cell populations were detected in the culprit but not in the nonculprit lesion of a patient with fatal myocardial infarction. Conclusions —UA is associated with the emergence of monoclonal T-cell populations, analogous to monoclonal gammopathy of unknown significance. Shared T-cell receptor sequences in clonotypes of different patients implicate chronic stimulation by a common antigen, for example, persistent infection. The unstable plaque but not the stable plaque is invaded by clonally expanded T cells, suggesting a direct involvement of these lymphocytes in plaque disruption.

The assembly of inflammatory lesions in rheumatoid arthritis is highly regulated and typically leads to the formation of lymphoid follicles with germinal center (GC) reactions. We used microdissection of such extranodal follicles to analyze the colonizing T cells. Although the repertoire of follicular T cells was diverse, a subset of T cell receptor (TCR) sequences was detected in multiple independent follicles and not in interfollicular zones, suggesting recognition of a common antigen. Unexpectedly, the majority of shared TCR sequences were from CD8 T cells that were highly enriched in the synovium and present in low numbers in the periphery. To examine their role in extranodal GC reactions, CD8 T cells were depleted in human synovium-SCID mouse chimeras. Depletion of synovial CD8 T cells caused disintegration of the GC-containing follicles. In the absence of CD8 T cells, follicular dendritic cells disappeared, production of lymphotoxin-α1β2 markedly decreased, and immunoglobulin (Ig) secretion ceased. Immunohistochemical studies demonstrated that these CD8 T cells accumulated at the edge of the mantle zone. Besides their unique localization, they were characterized by the production of interferon (IFN)-γ, lack of the pore-forming enzyme perforin, and expression of CD40 ligand. Perifollicular IFN-γ+ CD8 T cells were rare in secondary lymphoid tissues but accounted for the majority of IFN-γ+ cells in synovial infiltrates. We propose that CD8+ T cells regulate the structural integrity and functional activity of GCs in ectopic lymphoid follicles.