Virus antibodies in serum and synovial fluid of patients with rheumatoid arthritis and other connective tissue diseases.

Rubella and influenza A (H3N2) haemagglutination inhibition (HI) antibody titres and measles complement-fixing (CF), haemagglutination inhibition (HI), haemolysis inhibition (HLI), and ribonucleoprotein gel precipitation (RNP-GP) antibody titres were studied in the serum and synovial fluid of twenty patients with rheumatoid arthritis (RA), two patients with ankylosing spondylitis, and two patients with Reiter's syndrome. Antibody titres were also studied in the serum and CSF of four patients with systemic lupus erythematosus (SLE), one patient with dermatomyositis, and in the synovial fluid only of five patients with osteoarthritic knee effusions. Antibodies were found with each serological technique used in the synovial fluid of RA patients and the antibody titres were usually at about the same level as in the serum. The mean measles (HI, HLI, and RNP-GP) antibody titres were 4 to 6 times higher in the synovial fluid of RA patients than in synovial fluid of patients with osteoarthritic knee effusions, but a corresponding difference was not found in rubella and influenza A antibody titres. The mean measles antibody titres (CF, HI, HKI, and RNP-GP) were consistently higher in the synovial fluid of RA patients without rheumatoid factor than in the synovial fluid of RA patients with rheumatoid factor. In serum this difference was observed only with measles CF titres. The mean measles, antibody titres were consistently lower in the serum and synovial fluid of the RA patients without the synovial fluid haemolytic complement than in the RA patients with this haemolytic complement. No similar differences were found in the rubella and influenza antibody titres. No significant measles antibody titres were found in the CSF of patients with SLE or dermatomyositis.