Cell‐Mediated Immune Response in the Diseased Joints in Patients with Reactive Arthritis

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Abstract
To evaluate the level of lymphocyte activation in reactive and rheumatoid arthritis, density gradient‐isolated, synovial fluid mononuclear cells were stained with a panel of antisera directed at lymphocyte activation markers using an avidin‐biotin‐peroxidase complex (ABC) method. More specifically, we studied the expression of immune response‐associated class II HLA antigen (la), of receptors for interleukin 2 (Tac) and transferrin (T9), as well as of gp 40/80 glycoprotein (4F2). Although Ia+ cells formed about 60% of all the synovial fluid mononuclear cells in both disease conditions, the proportion of Tac+ (33±4% vs 3±1%, P+ (34±4% vs 5±2%, P+ (48±6% vs 3±2%, f<0.001) cells was high only in reactive arthritis. All the patients who had reactive arthritis followed a favourable clinical course during the 4‐month‐long prospective follow‐up, whereas disease activity was stable in patients with rheumatoid arthritis. These findings suggest that the diseased joints in reactive arthritis are a site for an active, but normally down‐regulated, cell‐mediated immune response.