[An immunochemical study of extracts from synovial fluid cells in rheumatoid arthritis]

Extracts were obtained by ultrasonic vibration from synovial fluid cells of patients with rheumatoid arthritis and rabbit antisera against the extracts were prepared. The antisera were absorbed with normal human plasma. Double immunodiffusion revealed two precipitin lines between the extracts and the antisera. These antigens were called P1 and P2. P1 and P2 antigens were detected in 17 (94%) and 10 (56%), respectively, out of 18 rheumatoid synovial fluids. In osteoarthritic fluids, P1 antigen was detected in only one (4%) of 25 cases but P2 antigen was never detected. The P1 antigen was not inactivated by trypsin or deoxyribonuclease but P2 antigen was digested by trypsin suggesting its protein character. Though it is not clear that these antigens are specific for rheumatoid arthritis, these antigens in synovial fluid cells seem to be associated with the rheumatoid synovial fluid.