CYSTEINE PROTEINASE ACTIVITY IN THE DEVELOPMENT OF ARTHRITIS IN AN ADJUVANT MODEL OF THE RAT

Cathepsin B and L activity was studied histochemically in arthritic ra t ankle joints using specific synthetic substrates in a post coupling method on unfixed and undecalcified cryostat sections of rat ankle joi nts. Activity was strongly increased in chondrocytes and cells of the inflamed synovium with the development of arthritis induced by the syn thetic adjuvant CP20961. Activity reached a maximum 20 days after indu ction of arthritis.and decreased as the rats entered natural remission . Cathepsin B and L were at their highest level when macrophages were present in the joint space, as shown by using monoclonal antibody mark ers for rat macrophages (ED1 and ED2) in a biotin-avidin immunoperoxid ase assay. This suggests that the macrophage infiltrate may have stimu lated proteinase production in chondrocytes through cytokine release. The profile of appearance of cysteine proteinases suggests their invol vement in the breakdown of cartilage and bone in the arthritic joint.