Morphology of effector cells attacking myeloma cells. Myeloma cells were purified from the bone marrow (patient no. 1) and were cultured with PBMCs from a healthy donor in the presence of humanized anti-HM1.24 MoAb (1 μg/mL) for 30 minutes. Cytospin preparations were stained with Wright-Giemsa (original magnification × 330).