Immunology of articular cartilage.

The extracellular matrix of articular cartilage is, in part, comprised of 2 macromolecular moieties, collagen and proteoglycans. This article discusses the role of an autoimmune response to these macromolecules in both inflammatory synovitis and osteoarthritis (OA). Autoimmunity to Type II collagen involving "arthrogenic epitope(s)", expressed on the Type II collagen molecule, as well as cell mediated immune responses to collagen may be relevant in the overall development of destruction of articular cartilage. In OA, a role for inflammation and the immune response to connective tissue macromolecules has been suggested by recent investigations. In this regard, autoimmunity plays a part in the progression of the degeneration of articular cartilage in OA.