Comparison of the in vivo inflammatory activities after intra-articular injection of natural and recombinant IL-1 alpha and IL-1 beta in the rabbit.

Comparison has been made of the in vivo pro-inflammatory activities or procine natural and human recombinant alpha and beta interleukin 1 (IL-1) after injection into the knee joints of rabbits. Both forms of pig IL-1 and human IL-1 were separately equiactive in vitro in stimulating rabbit synovial fibroblasts and articular chondrocytes to synthesize prostaglandin E2 (PGE2). Injection of IL-1 into the rabbit knee joint was not associated with swelling of the joint nor with the appearance of PGE2 in the synovial fluid. However, all preparations of IL-1 induced a dose-dependent increase in inflammatory leukocytes in the synovial lining and joint cavity. In addition, both the alpha and beta forms of IL-1 from both species caused loss of proteoglycan from the matrix of articular cartilage. This study demonstrates that both genetically distinct forms of IL-1 have the same range of inflammatory actions within the joint and that they have similar potencies in these respects.