Rheumatoid factors in the pathogenesis of rheumatoid arthritis.

Rheumatoid factors (RF) participate in the pathogenesis of rheumatoid arthritis by formation of immune complexes. IgM-RF form complement activating immune complexes with IgG-containing antigen-antibody complexes. IgG-RF form unique immune complexes without the presence of separate antigen molecules. The specificities of RF in rheumatoid arthritis have subtle differences from RF formed by B cell neoplasms. Immune deposits in rheumatoid articular cartilage have high potential for generating inflammation and contain RF. The immune deposits in articular cartilage need to be characterized further, and the mechanisms that initiate and perpetuate RF production in patients with rheumatoid arthritis should be elucidated.