Immunologic modulation of cartilage metabolism.

Preservation of the structural integrity of cartilage requires that metabolic homeostasis be maintained between chondrocyte anabolic and catabolic functions. This critical balance is perturbed in osteoarthritis (OA) in which synovial tissue and subchondral intratrabecular marrow often contain a focal and at times more diffuse mononuclear cell infiltration. Cytokines derived from T lymphocytes and monocytes have a capacity to: a) cause qualitative changes in and reversibly suppress chondrocyte proteoglycan, collagen, and non-collagen protein synthesis, and b) induce the synthesis and release of chondrocyte proteinases. Factors having comparable metabolic regulatory activity are produced by synovial tissue derived from idiopathic and secondary forms of OA.