Local activation of lymphoid cells in rheumatoid synovium

Lymphoid cell phenotype was investigated in the peripheral blood, synovial fluid, and synovial tissue of sixteen patients with rheumatoid arthritis (RA). In the peripheral blood of RA patients the proportion of cells expressing HLA-DR and beta 2-microglobulin receptors was higher than in normal controls, whereas the proportion of cells that were CD5+ (i.e. were T lymphocytes) was lower. Expression of the other cell surface antigens studied remained in the normal range. In the synovial tissue and synovial fluid of RA patients there was an increased percentage of cells expressing HLA-DR, beta 2-microglobulin receptors, CD25, CD5, CD4, and Thy-1, but the proportion of CD8+ cells was significantly decreased compared with that seen in peripheral blood. The CD4+/CD8+ ratio in RA joints was therefore significantly higher than that in peripheral blood. The proportion of cells expressing HLA-DR correlated with disease activity.