Enhanced T cell suppression is directed toward sensitive circulating B cells in multiple myeloma

Multiple myeloma, a disorder typically accompanied by monoclonal immunoglobulin excess and hypogammaglobulinemia was evaluated to delineate the status of T cell regulation on malignant B cell proliferation. Intact T cells and T cell subsets previously noted by us to be suppressor (Tγ) and helper (T non-γ) were isolated from 10 controls and 10 myeloma patients. Various concentrations of control and patient T cell subsets were mixed with control and patient B cells and stimulated with PWM. T cell effect on B cell proliferation as measured by [³H]thymidine incorporation was then determined. Myeloma Tγ cells were more effective than control Tγ cells in suppressing control or myeloma B cell [³H]thymidine incorporation. Interestingly, myeloma B cells, when added to myeloma Tγ cells, were suppressed to a greater extent than were control B cells when mixed with a similar concentration of myeloma Tγ cells. These in vitro studies suggest a complexity of B and T cell abnormalities in multiple myeloma; first, the myeloma B cells are extremely sensitive to Tγ cell suppression, and second, myeloma Tγ cells have excessive suppressor capacity. It is yet unclear whether these results are associated with an immunoregulatory response to this malignancy or represent part of the basic disease process.