Augmented Numbers of HLA-DR-Positive T Lymphocytes in the Synovial Fluid and Synovial Tissue of Patients with Rheumatoid Arthritis and Juvenile Rheumatoid Arthritis

Twenty to 40 % of T cells from synovial fluid and synovial tissue and 3–11 % of the peripheral blood T lymphocytes from patients with rheumatoid arthritis (RA) and juvenile rheumatoid arthritis (JRA) expressed HLA-DR antigens as detected by monoclonal anti-HLA-DR antibodies in direct immunofluorescence. Synovial fluid and synovial tissue T lymphocytes had a stimulating capacity comparable to that of non-T cells in the allogeneic primary mixed lymphocyte reaction (MLR). The MLR was inhibited by monoclonal anti-HLA-DR antibodies. This is, to our knowledge, the first report on in-vivo-activated T lymphocytes as stimulator cells in MLR. The results suggest that T cells from synovial fluid and synovial tissue are locally activated by stimuli so far unidentified.