Interleukin 2 and interleukin 2 inhibitors in human serum and synovial fluid. I. Characterization of the inhibitor and its mechanism of action.

An inhibitor of the murine interleukin 2 (IL-2) dependent cell line (CTLL-2) has been demonstrated in sera from healthy subjects as well as in sera and synovial fluid from patients with inflammatory arthritides. This inhibitor inhibits the mitogenic response of normal peripheral blood mononuclear cells and seems to be primarily due to impaired IL-2 production. The inhibitor does not appear to bind to IL-2 or the IL-2 receptor. This inhibition can be reversed with IL-2 but not interleukin 1. These observations may apply to the defects in IL-2 production and response demonstrable in rheumatoid arthritis and other autoimmune disorders.