In vivo treatment with IL-1 reduces the severity and duration of antigen-induced arthritis in rats.

IL-1 has been implicated in the pathogenesis of arthritis. Although IL-1 injected in vivo into normal joints results in a transient inflammatory reaction, we have shown that three weekly repetitive injections of IL-1 do not produce a progressive inflammatory condition suggestive of chronic arthritis. In fact, priming normal joints with three weekly IL-1 intraarticular injections results in a significant reduction in joint swelling and diminished histopathologic alterations/lesions caused by subsequent methylated BSA-induced arthritis. Similarly, post treatment with IL-1 intraarticular injection after arthritis induction reduced arthritic swelling and joint injury if IL-1 was given during the developing stage of arthritis. Our results suggest that IL-1 might limit arthritic inflammation and progressive cartilage destruction through an, as yet, undetermined mechanism(s). Further in vivo investigations are required to determine the therapeutic utility of IL-1 in reducing early arthritic inflammation.