Decrease of Fc gamma and C3b receptor-bearing granulocytes and of T lymphocytes in myelomatosis

18 patients with myelomatosis had lower percentages of granulocytes bearing receptors for Fc gamma (47.6%) and C3b (43.0%) than controls (80.4% and 75.0%). The percentage of T lymphocytes was decreased in patients when untreated sheep erythrocytes were used as indicator cells. Patients with high serum IgG levels had lower percentages of T lymphocytes. There was no significant difference in receptor profile between treated and untreated patients. The decrease in Fc gamma and C3b receptor-bearing granulocytes in myelomatosis is probably not due to serum or plasma factors since (a) the distribution of receptor-bearing lymphocytes was not different from that of the controls; (b) extra washings of cells or overnight incubation did not enhance the percentage of receptor positive cells; and (c) incubation of normal granulocytes in sera or plasma from myelomatosis patients did not cause a more pronounced reduction in the proportions of Fc gamma of C3b receptor-bearing cells than incubation in normal sera or plasma.