Serum anti-immunoglobulins in multiple myeloma and benign monoclonal hyperglobulinemia

Abstract

Anti-immunoglobulins with specificity to human native IgG and (Fab′) 2 were detected in 69 sera of patients with multiple myeloma and 71 sera from 22 patients with benign monoclonal hyperglobulinemia with titers distinctly higher than those found in two control groups (healthy persons, sarcoidosis patients). Without further differentiation, no correlation of anti-immunoglobulin titers to the clinical status of the disease was observed. Chromatographic separation of sera on Sephadex G-200 revealed three molecular species of anti-immunoglobulins: type I, MW ca. 900,000; type II, MW 160,000; type III, MW < 100,000. Elevated titers of type III anti-immunoglobulins were observed only in multiple myeloma. Using immunoadsorbent techniques type III anti-immunoglobulins were identified as (Fab′) 2 fragments. Lacking idiotypic specificity, type III anti-immunoglobulins were shown to react with allotypic as well as idiotypic immunoglobulins on the surface of PBL B-lymphocytes. In addition, they inhibited significantly antibody-dependent cellular cytotoxicity reactions in vitro using IGR 3 melanoma cells as targets, and preparations of peripheral blood lymphocytes from healthy individuals as effector cells. In contrast, no significant inhibition of cytotoxic activity was observed using type II (IgG) anti-immunoglobulins from benign monoclonal hyperlgobulinemia patients' sera in equal concentrations.