Increased proliferation of human synovial fibroblasts treated with recombinant immune interferon

Because immune lymphocytes are commonly found in inflamed rheumatoid synovium, we tested the hypothesis that immune or gamma-interferon, a product of activated lymphocytes, may modulate synovial cell growth. Using a cell culture model, we found that addition of gamma-interferon at 10 to 100 antiviral units/ml to cultures of human synovial fibroblasts or human foreskin fibroblasts resulted in a two- to threefold increase in proliferation, measured by incorporation of [3H]thymidine and cell number. The proliferative effect was abrogated if the gamma-interferon was neutralized with a specific monoclonal antibody. Increased proliferation induced by gamma-interferon was antagonized by all-transretinoic acid but was enhanced by prednisolone. Our data indicate that the T cell product, gamma-interferon, can directly modulate synovial cell function and suggest that this interaction may play a role in the proliferative lesion of rheumatoid arthritis.