Interleukin-4 inhibits interleukin-11 production by rheumatoid synovial cells

Objective. To examine the effect of interleukin-4 (IL-4) on IL-11 production by rheumatoid synovial cells. Methods. Freshly isolated rheumatoid synovial cells (FRS) were obtained by collagenase digestion of rheumatoid arthritis (RA) synovial tissue specimens taken at the time of operation. Rheumatoid synovial cells at four to eight passages were used as cultured rheumatoid synovial fibroblasts (RSF). IL-11 concentration was measured by ELISA. Results. IL-4 inhibited the production of IL-11 by FRS in a dose-dependent manner. This inhibition was observed in FRS obtained from six patients, and the mean inhibition was 46.5%. The inhibitory effect of IL-4 on IL-11 production was cancelled by the addition of anti-IL-4 antibody. IL-4 also inhibited IL-11 production by IL-1 alpha-stimulated cultured RSF. Conclusion. IL-4 inhibited IL-11 production by rheumatoid synovial cells. IL-4 has a protective effect on bone resorption. On the contrary, IL-11 participates in bone resorption via osteoclastogenesis. Therefore, IL-4 may exert its protective effect on bone resorption, at least in part, via inhibition of IL-11 production in rheumatoid joints.