In vitro immunoglobulin synthesis by lymphocytes from patients with rheumatoid arthritis. I. Effect of monocyte depletion and demonstration of an increased proportion of lymphocytes forming rosettes with mouse erythrocytes.

We have investigated B cell function in nine patients with rheumatoid arthritis (RA) compared to sex and age matched controls in a pokeweed mitogen driven system. Levels of IgG and IgM synthesized in the supernatant were measured by a competition ELISA. We have found that cultured mononuclear cells from RA patients showed a defective Ig synthesis when depleted of monocytes. In contrast RA mononuclear cells not depleted of monocytes produced substantial levels of Ig after stimulation by the mitogen. The percentages of T and B lymphocytes in the peripheral blood of RA patients were normal; however, an increased number of lymphocytes formed rosettes with mouse erythrocytes indicating an abnormality in the B cell pool. These results demonstrate defective in vitro immunoglobulin synthesis by RA lymphocytes and show the importance of monocytes in this culture system.