Synovial mononuclear cell responses to rubella antigen in rheumatoid arthritis and unexplained persistent knee arthritis.

3H-thymidine uptake responses by synovial mononuclear cells to rubella antigen were studied in 10 patients with rheumatoid arthritis and in 8 patients with unexplained arthritis confined to knee joints. The synovial cells of only 1 rheumatoid subject responded to rubella. In only 1 of the patients with knee joint arthritis was the response to rubella greater than to other tested antigens. Peripheral blood leukocytes did not respond to rubella in either patient. Rubella virus was isolated from the knee joints of both patients.