NK cell function recovers after dexamethasone removal, but the same cells no longer respond to the immunostimulatory effect of lenalidomide. (A) Healthy donor PBMCs (n = 3) were cultured with no drug treatment (■), lenalidomide (*), or lenalidomide and dexamethasone (▴), and cytotoxicity was assessed against K562 at day 3 (left panel). To assess if NK cell function could recover after drug removal, the treated PBMCs were washed to remove drugs, then maintained in culture either without lenalidomide (♢) or with lenalidomide (♦). Chromium release assays using K562 as targets were performed 3 and 6 days after the drug washout (middle and right panels; n = 3). As a negative control, washed PBMCs were also treated with ongoing lenalidomide and dexamethasone (▾). (B) The same NK cell recovery experiment was repeated using U266 as target cells. Figures are pooled data from 3 separate experiments.