Lenalidomide augments NK-cell IFN-γ production and cortical actin rearrangements in NK cells isolated from MM patients. (A) Primary NK cells isolated from MM patients were treated with DMSO or 1.0 µM lenalidomide (+150 U/mL IL-2) for 24 hours in wells coated with anti-CD16 mAb or IgG1 isotype-matched control mAb. IFN-γ release was assessed by ELISA. E:T ratio was 10:1. Data shows mean ± SD from 9 MM patients. (B) Proportion of primary NK cells from MM patients expressing IFN-γ after stimulation on anti-CD16 mAb-coated surfaces in the presence of DMSO or 1.0 µM lenalidomide for 120 minutes. Graph shows mean ± SD, n > 100 from 9 MM patients. (C) Average size of holes in the actin mesh at the pNK synapse for NK cells from MM patients stimulated on anti-CD16-coated surfaces and then imaged by STED microscopy. Data show the average per MM patient (20 cells analyzed per patient); black lines show the mean. (D) The proportion of the synapse area predicted to be penetrable by a vesicle of 200- to 500-nm diameter for same cells as in panel C. (E) Superresolution imaged obtained by STED microscopy of membrane proximal actin in NK cells from MM patient who are either in remission or relapsing, treated with DMSO vehicle control or 1.0 µM lenalidomide. Scale bars, 5 µm. (F) IFN-γ release as shown in panel A separated by whether the patients are in remission or relapsing. (G) The proportion of the synapse area predicted to be penetrable by a vesicle of either 200- to 300-nm diameter or 301- to 500-nm diameter in NK cells from MM patients who are in remission or relapsing. *P < .05, **P < .01, ***P < .001, 1-way ANOVA with Tukey posttest.