In vitro cytotoxic response to human myeloma plasma cells by peripheral blood leukocytes from patients with multiple myeloma and benign monoclonal gammopathy

Peripheral blood leukocytes (PBL) from myeloma patients were studied for their capacity to lyse plasma cells from myeloma patients, benign monoclonal gammopathy (BMG) patients, and nonneoplastic disease patients. Plasma cells were isolated from bone marrow, labeled with 51Cr, and cultured with PBL isolated from patients with myeloma, BMG, or nonneoplastic disease, as well as normal individuals. PBL from patients with multiple myeloma demonstrated responses to autologous or allogeneic myeloma plasma cells. Optimum conditions for cytotoxic response included a responder-to-stimulator ratio of 1:1 and an effector-to-target ratio of 20:1. PBL from normal individuals or patients with BMG failed to demonstrate this response. However, PBL from BMG patients, but not normal individuals, could be induced to kill myeloma plasma cells (but not nonmyeloma plasma cells) by simultaneous stimulation with allogeneic lymphocytes and myeloma plasma cells.