Capacity of myeloma plasma cells to stimulate alloreactive T cells (MLR). Allogeneic PBMCs were cultured with different numbers of CD38⁺⁺ plasma cells (▪), CD38⁺ cells (□), BMMCs (•), or PBMCs (○) from one patient. Means ± SD were determined on triplicate values from two experiments. Cell proliferation was measured on day 6. Concanavalin A-induced cell activation in allogeneic PBMCs was 22,305 cpm.