Effect of lenalidomide on NK cells. (A) Lenalidomide treatment at 48 hours significantly decreased rituximab but not alemtuzumab-mediated direct cytotoxicity. B CLL cells were incubated with 10 μg/mL rituximab, alemtuzumab, or trastuzumab in the presence of 50 μg/mL cross-linking goat anti–human Fc antibody (αFc). Media and cross-linking were used as control. The percentage of apoptosis was determined by annexin V/propidium iodide staining after 24 hours (N = 10, P = .017). Data shown were normalized on media control. (B) Lenalidomide treatment increases percentage of CD56⁺/CD16⁺ cells. Negatively selected NK cells were incubated with lenalidomide (0.5 μM) or vehicle control. CD56 and CD16 surface expression was analyzed by flow after 72 hours of treatment. The graphs show, respectively, percentage change CD56⁺/CD16⁺ (left panel, N = 12, P < .01) and CD56⁻/CD16⁺ (right panel, N = 12, P < .005) double-positive cells. (C) Representative flow result for CD56 and CD16 surface expression of lenalidomide-treated NK cells.