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.