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 < 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.