Studies on heterophile antibodies in rheumatoid arthritis.

Sera and synovial fluids of patients with rheumatoid arthritis were studied for the presence of heterophile antibodies to sheep and bovine erythrocytes by means of hemolysis in agar gel. It was demonstrated that 18 of 146 sera had hemolytic antibody titers of 160 or more; all 18 (12%) against sheep and 8 (6%) against bovine erythrocytes. Of 31 synovial fluids examined, 5 showed hemolysin titers of 40 or more; all 5 (16%) against sheep and 3 (10%) against bovine erythrocytes. These heterophile antibodies were shown to belong to IgM and/or IgG class. Absorption and inhibition studies revealed that antibodies of 10 positive sera and 2 synovial fluids were of Forssman specificity and antibodies of 6 sera and 3 synovial fluids were of Hanganutziu-Deicher specificity. Two remaining sera were shown to contain a mixture of Forssman antibodies and immune anti-B antibodies.