Induction of Cartilage Degradation in Experimental Arthritis Produced by Allogeneic and Xenogeneic Proteoglycan Antigens

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Abstract
A single intra-articular injection of proteoglycan (PG) antigens induced sterile inflammatory response and cartilage degradation in preimmunized rabbits and dogs. Both cell-mediated and humoral immune reactions could be detected against PG antigens in these animals, but there was no response against collagen Type II. The lymphocytes isolated from the inflamed synovial layer proved to be predominantly of T cell type. The cartilage degradation was indicated by the accumulation of lgG and complement in the superficial layer of the articular cartilage, by the diminished number of chondrocytes and by the increased binding of specific antibodies in the ground substance. The results suggest that PG antigens trigger local immune reactions which become self-sustaining by enzymatic exposure of antigenic sites. The anti-PG antibodies are cytotoxic to articular chondrocytes and thus can block the continuous neogenesis of matrix components which may lead ultimately to deterioration of the cartilage. This type of experimental arthritis appears to be a model closely related to rheumatoid arthritis.