[Antigens of the synovial fluid. I. Immunodiffusion and electrophoretic studies].

9 rabbits were immunized with the synovial fluid of patients with rheumatoid arthritis. The antisera thus raised contained antibodies against 18 serum proteins and against fibrinogen. After full absorption of the antisera with human blood plasma a maximum of 5 and average of 3 typically synovial antigens could be detected in the synovial fluid by immunodiffusion. One antigen (SF1) was present in all studied human organs and connective tissue extracts. It is thermostable, insoluble in alcohol, but soluble in 0,3 N perchloric acid. The two other antigens had a lipid character, one of them was also thermostable and insoluble in alcohol and smaller amounts there-of were found in organ extracts. The antigens could also be detected in synovial effusions caused by trauma, whereas normal synovial fluid contained only two unidentified antigens in low titre. Using immunodiffusion the antisera did not show any cross reaction with synovial fluids and organ extracts of other species. Immuno-electrophoretically only the line of the SF1 in the alpha1/alpha2 area could be definitely localized.