anti-DR antibodies inhibit in vitro production of human rheumatoid factor

Anti-MHC class II antibodies have been shown to have a profound effect on the immune system and have been used successfully in the therapy of human and animal autoimmune diseases. In addition, naturally-occurring anti-DR antibodies have been observed in the sera of rheumatoid arthritis (RA) and systemic lupus erythematosus patients. Now, we demonstrate that several monoclonal anti-DR, but not anti-DQ antibodies specifically inhibit the production of rheumatoid factor (RF) in pokeweed-stimulated cultures of peripheral blood mononuclear cells from RA patients. Moreover, partially-purified anti-DR antibodies from RA sera have similar inhibitory effects on in vitro RF synthesis. These results indicate the inhibition of autoantibody production as a possible mechanism operative in immunotherapy using anti-class II antibodies. Furthermore, this data also suggests a protective, beneficial role for the endogenous anti-DR autoantibodies in RA.