Abstract
Interleukin 1 (IL - 1) has been detected in the synovial fluids of patients with rheumatoid arthritis (RA) and, among all inflammatory factors, is now considered to be the one most important in joint destruction. We detected as well IL -1 in the synovial fluids of 15 RA patients examined by radioimmunoassay (0.2-0.6ng/ml) . However, synovial fluids failed to exhibit any IL -1 biological activity in a mouse thymocyte assay, suggesting the presence of an IL -1 inhibitor in these synovial fluids. Such an IL -1 inhibitor activity was shown to be associated with a 50-70 kDa fraction in gel-filtration chromatography using a Sephadex G- 75, and to suppress thymocyte proliferation by IL -1β . This inhibitory factor may have a regulatory function in the chronic inflammatory process in RA.
