IFN-γ production and cytotoxicity of NK cells from patients after SCT. (A) IFN-γ production by NK-cell subsets. CD16^–/low and CD16^high cells were purified, expanded, and stimulated with IL-2 (□) or IL-12 plus IL-18 (▪). Frequency of IFN-γ⁺ NK cells was determined by MACS IFN-γ secretion assay as described in “Patients, materials, and methods.” Results obtained with healthy donors (n = 3) and 3 patients (pt) after SCT are shown. (B) Cytotoxicity of NK cells against K562 target cells. NK cells were purified from PB of healthy donors (○) or patients after allogeneic SCT (♦) collected at 14 and 30 days after SCT. Cytotoxicity was measured as LDH released from lysed K562 cells (“Patients, materials, and methods”). Results obtained with 3 healthy donors and 5 patients after SCT are shown (mean ± SEM).