Parvovirus associated antigen in the synovial membrane of patients with rheumatoid arthritis.

Homogenates of synovium from patients with rheumatoid arthritis (RA) and osteoarthritis (OA) were centrifuged on caesium chloride density gradients to obtain isolates of a density similar to that of parvoviruses. Six of 11 RA isolates and none of six OA isolates reacted with an antiserum raised against a rheumatoid associated, parvovirus-like agent (RA-1 virus). An anti-B19 parvovirus antiserum did not react with any of the isolates tested.