TOXICITY OF COMPLEMENT FOR CHONDROCYTES - A POSSIBLE SOURCE OF CARTILAGE DEGRADATION IN INFLAMMATORY ARTHRITIS

Cartilage from patients with rheumatoid arthritis and from animals wit h antigen-induced arthritis is frequently contaminated with complement -containing immune complexes. A possible role for complement activatio n in cartilage degradation was modeled in vitro by exposing cultured b ovine chondrocytes to homologous serum, and determining cytotoxicity b y monitoring the release of intracellular Cr-51. Complement activation was found to be cytotoxic, having maximal effect at 20 - 30% serum by 18 h. Serum toxicity was ablated by heat (50-degrees-C, 20 min) or me thylamine treatment but not by EGTA, suggesting that in these experime nts activation occurred by the alternate route. The implications of th e results are discussed in relation to ultrastructural evidence for th e involvement of complement in the pathogenesis of cartilage degradati on in inflammatory arthritis.