Induction of acute synovitis in the rat by human interferon

Intra-articular injection of human interferon (alpha, beta or gamma) into rat knee joints induced increases in knee diameter, synovial effusion and synovial membrane weight. An inflammatory cell infiltrate was also noted in synovial membranes. Hydrocortisone diminished the inflammatory response when injected together with interferon. Mouse beta interferon did not produce synovitis in rat knees. These results further support the hypothesis that interferon may play a role in the pathogenesis of human arthritis.