IgG and IgM antibody to native type II collagen in rheumatoid arthritis serum and synovial fluid. Evidence for the presence of collagen-anticollagen immune complexes in synovial fluid.

Levels of IgG and IgM antibody to native type II collagen, a component of articular cartilage, were measured by a specific solid-phase radioimmunoassay, in 48 rheumatoid arthritis patients. Good correlations were found between the levels in sera and those in synovial fluids. Collagenase digestion caused a significant rise in specific antibody levels in synovial fluids, indicating the presence of intraarticular collagen-anticollagen complexes. These immune complexes may be one mechanism for perpetuation of inflammation in some rheumatoid arthritis patients.