Analysis of T cell receptors in rheumatoid arthritis: the increased expression of HLA‐DR antigen on circulating γδ+ T cells is correlated with disease activity
The phenotypic characteristics of peripheral blood T cells, isolated from 37 rheumatoid arthritis (RA) patients and 17 healthy controls were determined with special emphasis on γδ+ T cells and CD4−CD8−αβ+ T cells. Two‐ and three‐colour automated flow cytometry analyses were performed using a panel of MoAbs directed against differentiation antigens and T cell receptor molecules. The results demonstrated: (i) no significant difference between the percentages or CD4−CD8−αβ+ T cells in patients and controls; (ii) a significant decrease of the γδ+ T cell level in the peripheral blood of RA patients relative to controls; (iii) phenotypic abnormalities of circulating γδ+ T cells in RA patients suggestive of an activation status in vivo. These abnormalities included a significant reduction in the density of the T cell differentiation antigen CD3 and an increase in the expression of HLA‐DR antigen. The level of circulating HLA‐DR+/γδ+ T cells was significantly higher in patients with active disease. HLA‐DR+/γδ+ T cells were also present in the synovial fluid obtained from three patients with an active disease. In addition, preliminary experiments showed that the activated γδ+ T cells were predominantly Vδ1. Taken together, these data support the involvement of γδ+ T cells in the pathogenesis of RA.