THE EFFECT OF AN INTERLEUKIN-1 RECEPTOR ANTAGONIST PROTEIN ON TYPE-IICOLLAGEN-INDUCED ARTHRITIS AND ANTIGEN-INDUCED ARTHRITIS IN MICE

Objective. To investigate the anti-arthritic effect of recombinant hum an interleukin-1 receptor antagonist protein (IRAP) in two experimenta l models of arthritis. Methods. Recombinant IRAP was administered dail y to mice with type II collagen-induced arthritis (CIA) or with antige n-induced arthritis (AIA) provoked by methylated bovine serum albumin (mBSA). Disease incidence and severity were assessed by a clinical ind ex and histologic features. Serum antibody to type II collagen, spleen cell proliferation to mBSA, and anti-IRAP antibodies were measured as indices of immune function. Results. IRAP reduced the incidence and d elayed the onset of CIA and suppressed the antibody response to type I I collagen. In contrast, IRAP did not affect the pathogenesis of AIA a nd had no effect on either humoral or cellular immune responses to mBS A in arthritic mice. Conclusion. These observations suggest that inter leukin-1 may play a prominent role in the development of some, but not all, forms of arthritis.