Regulation of immunoglobulin synthesis by monocytes in multiple myeloma and benign monoclonal gammopathy.

The distribution and regulatory function of immunoglobulin (Ig) synthesis by monocytes were assessed using several monoclonal antibodies and a cell sorter in samples from 13 patients with multiple myeloma (MM) and nine patients with benign monoclonal gammopathy (BMG). Since all of these cells were separated directly with the cell sorter, their purity and viability were greater than 98% and greater than 99%, respectively. The absolute number of lymphocytes was significantly reduced. The number of monocytes stained with non-specific esterase was within normal range in MM and BMG, as were the absolute number and the proportion of cells which reacted with OKM1 and Mo2 (OKM1+ cells and Mo2+ cells, respectively). The helper activity of monocytes in Ig synthesis stimulated with pokeweed mitogen (PWM) was impaired in MM compared with normal controls. None of these abnormalities in the distribution and regulatory function of monocytes was observed in BMG. The possible immunoregulatory mechanism of MM is discussed.