Significance of immune complex deposits in osteoarthritic cartilage.

Deposits of immunoglobulins and complement in cartilage with synovial mononuclear cell infiltrates suggest local immune reactions in osteoarthritic joints. The variabilities defined in deposition pattern and synovial histopathology, the patterns and extent of polyarthritis, without evidence of systemic illness, suggest that these immune reactions mark past events in the host's response localized in mechanically prejudiced articulations. The current data give little support for an immune initiation for osteoarthritis nor for the induction of autoimmunity; rather, they suggest episodes of immune insult which may at times initiate and at times prolong clinical inflammation in mechanically deranged sites and which, via the activation of complement and mononuclear cell mediators, accelerate cartilage damage.