Abstract

Since patients with myeloma have serious abnormalities of humoral immunity, we applied an in vitro assay to determine the capacity of B lymphocytes to mature into immunoglobulin-secreting cells. In peripheral blood lymphocytes from 22 normal persons, geometric mean immunoglobulin synthesis was 4910 ng for IgM, 1270 ng for IgA and 1625 ng for IgG. The synthesis rates of peripheral blood lymphocytes of 22 patients with myeloma were 458 ng for IgM, 321 ng for IgA and 218 ng for IgG. Circulating mononuclear cells from three of six patients tested suppressed polyclonal immunoglobulin synthesis by cocultured normal lymphocytes. Suppressive activity was not mediated by purified T cells alone. Removal of phagocytic mononuclear cells from lymphocyte populations of one patient nullified suppressive activity. Removal of phagocytic mononuclear cells from lymphocyte populations of a second patient led to a nearly 10-fold increase in polyclonal immunoglobulin synthesis. Therefore, host suppressor cells may play a part in the decreased capacity of B lymphocytes to secret immunoglobulin in certain patients with myeloma.