Effect of drug pretreatment of effector or myeloma cells on antimyeloma immunity. PBMCs were isolated from a healthy donor and stimulated with IL-2 (10 ng/mL) for 24 hours, in the presence or absence of 1μM Len (A), 1μM Pom (B), 10nM Bort (C), or 50nM Dex (D). Luc⁺ MM.1S cells were similarly pretreated with Len, Pom, Bort, or Dex. PBMCs and MM cells were washed and counted, and viable luc⁺ MM.1S target cells were counted and cultured at increasing ratios of viable PBMCs for 4 hours in the absence of drug. Data were normalized to each respective drug- and PBMC-free culture of MM.1S cells. Len and Pom pretreated PBMCs alone or both PBMCs and MM cells significantly increased cytotoxicity (A-B; 2-way ANOVA; P < .0001 for each comparison). Bort pretreatment of MM cells alone or both PBMCs and MM cells also enhanced myeloma cytotoxicity (C; P < .0001). In contrast, Dex pretreatment of only MMs, or only PBMCs, or both did not augment myeloma cytotoxicity (D; n = 4 for each condition).