Natural killer activity and antibody-dependent cell-mediated cytotoxicity in multiple myeloma.

Natural killer (NK) activity and antibody-dependent cell-mediated cytotoxicity (ADCC) were studied by routine methods in 11 patients with untreated malignant monoclonal gammopathy. NK and/or ADCC activity was clearly reduced in three patients with advanced disease. Moreover, sera from some myeloma patients impaired the ADCC and NK activity. A large quantity of purified monoclonal IgG from one patient appeared to inhibit NK and ADCC activity as did high concentrations of pooled polyclonal immunoglobulin from healthy persons. In two of these 11 patients, other malignancies were diagnosed prior to chemotherapy. One of these patients, who had nonsecretory myeloma, had marked impairment of NK and ADCC activity; the other, with IgG myeloma, had normal NK and ADCC activity.