Impaired immunoglobulin synthesis in multiple myeloma: a B-cell dysfunction.

Peripheral blood samples collected from normal individuals and patients with benign monoclonal gammopathy and multiple myeloma were separated and assayed for their T- and B-cell subpopulations as well as immunoglobulin (IgG, IgM) synthesis in vitro. To rule out any functional or quantitative alterations related to therapy, only newly diagnosed multiple myeloma patients and subjects with benign monoclonal gammopathy were included in our study. Multiple myeloma patients were further subdivided into two groups. Group A consisted of patients with low and intermediate tumor burdens, while group B included patients with high tumor mass. B- and T-cell subset analysis revealed an abnormal ratio between B/T and OKT4+/OKT8+ lymphocytes compared to healthy controls. These alterations were especially prominent in group B multiple myeloma. Immunoglobulin synthesis was studied in pokeweed-mitogen-stimulated lymphocyte cultures. The results indicate that the failure to synthesize and secrete immunoglobulin resides within the B-cell lineage and is probably due to a functional B-cell defect. T-cell immunoregulatory functions seem to be unaffected in both multiple myleoma and benign monoclonal gammopathy patients.