IL-2 restores impaired NK function in MDS patients. PMBCs from patients with MDS and PBMCs from healthy donors were cultured for 3 days in the absence (−IL-2) or the presence of 100 IU/mL IL-2 (+IL-2). (A) The graphic representation of the percent specific lysis at a 50:1 effector-target (E/T) ratio is shown for 5-hour ⁵¹Cr-release assays using K562, MDS1, and 721.221 cells as targets. From a subset of these samples, the (B) percentage and the (C) median fluorescence intensity (MFI) of NKG2D, NKp30, NKp46, NKp44, and CD69 was determined in CD56⁺/CD3⁻ NK cells by flow cytometry. The number of patients and healthy controls included in each group is shown at the bottom of each graph. The graphs represent the average of duplicate samples; SD is indicated by the error bars, and asterisks indicate statistical significance as determined by a paired t test.