Effects of cytokines on ADCC activity of PBMCs against RPMI 8226. PBMCs from healthy donors (A, n = 5) and myeloma patients (B, n = 5) were cultured with various cytokines for 3 days and were used as effector cells in the presence of 1 μg/mL control human IgG (□) or humanized anti-HM1.24 MoAb (▪). Cytotoxicity was determined by a 4-hour ⁵¹Cr-release assay at an E/T ratio of 50. Data represent the mean ± SD of triplicates. *P < .05 or †P < .001, compared with the data of nonactivated PBMCs in the presence of humanized anti-HM1.24 MoAb.