T-cells of multiple myeloma patients triggered by the autologous mixed lymphocyte reaction suppress polyclonal immunoglobulin synthesis.

To elucidate the possible role of T-cells of patients with multiple myeloma (MM) in the suppression of polyclonal immunoglobulin synthesis. T-cells with and without prior activation by the autologous mixed lymphocyte reaction (AMLR) were added to normal immunoglobulin (Ig)-secreting cultures. The suppression induced by AMLR-activated T-cells from patients with MM was compared to that induced by AMLR-activated T-cells from apparently normal controls. The addition of 10% unstimulated autologous T-cells from patients with MM resulted in minimal suppression of IgG synthesis (87 +/- 19% of baseline values for patients and 115 +/- 21% for controls, no significant difference). The suppression sharply increased when T-cells were preactivated by AMLR and then added in the same concentration to the IgG-secreting cultures (38 + 12% of baseline values for patients compared to 106 + 14% for controls, P less than 0.05). AMLR cultures were performed in the presence of adherent monocytes and after their depletion. The T-cell suppressor effect on normal IgG synthesis was unchanged after monocyte depletion. T-cells preactivated in the AMLR from patients with MM sharply suppress in vitro polyclonal IgG synthesis, and the activation of these suppressor T-cells is not dependent on the presence of monocytes.