Lenalidomide enhances XmAb5574-induced NK cell–mediated ADCC. Ability of XmAb5574 to mediate ADCC against CLL cells through healthy donor NK cells was significantly enhanced by the pretreatment of NK cells with 0.5μM lenalidomide for 24 hours (20.6% higher ADCC with lenalidomide compared with vehicle control; 95% CI, 2.0%-39.2%; *P = .03; n = 21; at E/T of 25:1). Standard 4-hour ⁵¹Cr-release assay using patient CLL cells as target cells and healthy donor NK cells as effector cells was used. Error bars represent SEMs.