Interleukin-2 inhibitor in rheumatoid arthritis synovial fluid does not inhibit mononuclear cell responses to mitogens.

Synovial fluid (SF) from rheumatoid arthritis (RA) patients were tested for their ability to inhibit the proliferative responses of normal peripheral blood mononuclear cells (PBM) to mitogens and interleukin-2 (IL-2). SF significantly inhibited the responses to concanavalin A (CON A) and phytohaemagglutinin (PHA), but significantly enhanced the responses to IL-2. Similarly, SF mononuclear cells (SFM) were hyporesponsive to CON A and PHA compared with autologous PBM, but hyper-responsive to IL-2. It is concluded that an IL-2 inhibitor in RA SF is unlikely to be the cause of SFM hyporesponsiveness to mitogens.