Abstract
Peripheral blood and synovial fluid mononuclear cells (MNC) were cultured with pokeweed mitogen for 7 days, and the media which contained secreted IgM rheumatoid factor (IgM RF) were assayed by double antibody radio-immunoassay technique, which was specific and sensitive enough to assay them.
Peripheral blood and synovial fluid MNC from seropositive RA patients synthesized high levels of IgM RF, whereas those from seronegative RA patients, patients of osteoarthritis and normal subjects synthesized low levels of it. The IgM RF titers in media were correlated well with the level present in the sera of the donors which were assayed by haemagglutination methods. Synthesis of IgM RF by synovial fluid MNC but not by peripheral blood MNC led to a concomitant synthesis of total IgM. Moreover B lymphocytes demanded helper activity of T lymphocytes for the synthesis of IgM. These data suggested that peripheral blood and synovial fluid MNC from patients with RA play an important role in the synthesis of IgM RF in vivo.
