Dexamethasone antagonizes the immunomodulatory effect of lenalidomide. (A) Healthy donor PBMCs (n = 3) were treated with lenalidomide (*), dexamethasone (▾), lenalidomide and dexamethasone in combination (●), or no drugs (■) and used as effectors against K562 cells (left panel; n = 6). To assess whether dexamethasone-induced NK cell suppression could be rescued, PBMCs were cultured with dexamethasone in the presence of high-dose IL-2 at 500 U/mL (○) or both high-dose IL-2 and lenalidomide (□; right panel). (B) NK cell–mediated cytotoxicity against U266 after drug treatment was also assessed under the same conditions described above. These data are representative of 3 different experiments.