Spontaneous and pokeweed mitogen induced in vitro immunoglobulin and IgM rheumatoid factor production by peripheral blood and synovial fluid mononuclear cells in rheumatoid arthritis.

Enzyme-linked immunosorbent assays (ELISA) were used to measure IgG, IgM and IgM rheumatoid factor (IgM RF) production in supernatants of pokeweed mitogen (PWM) stimulated peripheral blood mononuclear cells (PBMNC) of patients with rheumatoid arthritis (RA) and controls. Spontaneous and stimulated IgG and IgM production by RA and controls was comparable, but spontaneous production of IgM RF was only observed in RA and was related to their drug therapy. A significant difference was found between PWM induced IgM RF production in RA and controls and also between patients on "second-line" and on nonsteroidal anti-inflammatory drugs (NSAID). In addition, spontaneous IgM RF production by synovial fluid cells was significantly higher than the paired PBMNC.