Synovial VLA-1+ T cells display an oligoclonal and partly distinct repertoire in rheumatoid and psoriatic arthritis

VLA-1 integrin expressing T cells are more frequent in inflammatory synovial fluids (SF) compared to peripheral blood. Recent studies suggest that VLA-1 expression mainly marks IFNγ+ T cells while excluding both IL-4+ and regulatory FoxP3+ T cells. To further characterize the TCR repertoire of the potentially pathogenic VLA-1+ IFNγ+ T cells, isolated from SF of adult patients with rheumatoid and psoriatic arthritis, we determined the complementarity determining region (CDR)3 spectratypes. Here we show in a cohort of 9 patients that VLA-1+ T cells display a perturbed repertoire that, moreover, differs from that of VLA-1- synovial T cells and even VLA-1+ PB T cells. Importantly, random sequencing of the CDR3 region of the TCR variable β (BV) 6.1 gene of both VLA-1+ and VLA-1- synovial T cells, in one patient, revealed that their sequences were by and large different (29 out of 33 clones). Thus, our results imply that VLA-1+ T cells that infiltrate into inflamed joints represent a partly distinct and highly oligoclonal population of Th1 cells, probably selected by unique antigens.