Regulation of the in vitro monoclonal immunoglobulin production in cultures of peripheral blood mononuclear cells and bone marrow cells from myeloma patients mediated by T cell dependent mitogens.

In vitro monoclonal immunoglobulin (mIg) production of cultured tumour cells--prepared from the bone marrow (BM) or from the peripheral blood (PB) of 40 multiple myeloma (MM) patients, 16 patients with monoclonal gammopathy of undetermined significance and two patients with M. Waldenström--was measured with an enzyme-linked immunosorbent assay (ELISA) using anti-idiotype and anti-class specific antisera. After in vitro stimulation with pokeweed mitogen (PWM) or OKT3 antibody, mIg production was regularly suppressed in BM cell cultures, whereas enhanced, unaltered or suppressed production was observed in PB cell cultures. These observations show that the expanded clone in MM can still be regulated in vitro. Separation experiments demonstrated the involvement of T cells in this in vitro system. The results could be explained by the hypothesis that activated T cells can suppress mature cells of B cell differentiation, as found in BM of the patients, but stimulate earlier B cells from the peripheral blood towards differentiation into Ig secreting cells.