[Rheumatoid factors--recent advances in measurement techniques, their fine specificities and mechanisms of their...

Rheumatoid factors (RF) are autoantibodies directed to the Fc of IgG. RF are present in the blood and synovial fluid of most patients with rheumatoid arthritis, and are also commonly detected in Sjögren syndrome and other autoimmune diseases, in chronic infectious diseases such a viral hepatitis and subacute bacterial endocarditis, and even in healthy individuals at low titers. Although vast studies have been made so far, the precise mechanisms leading to RF production and the fine specificity of human RF have not been well delineated. In this report, we present recent observations of RF concerning the following items: 1) changes in measurement techniques, 2) biological significance of RF in diseased and healthy states, 3) analysis of specificity of RF, and 4) mechanisms inducing RF production.