NKG2A, KIR, and CD57 independently correlate with the proliferative capacity of CD56^dim NK cells. (A) Representative staining for CD57 on NK cells from one healthy donor. (B) Representative staining for CFSE and CD57 on NK cells from one healthy donor after 5 days of culture with the indicated cytokines. (C) Frequency of CD57⁻ and CD57⁺ NK cells diluting CFSE on days 0, 3, 5, and 7 after stimulation with the indicated cytokines (n = 6; mean ± standard error of the mean [SEM]). (D) Histograms of one representative experiment in which the indicated NK-cell subsets were purified by FACS sorting and stimulated with IL-2 for 5 days. (E) Dilution of CFSE on FACS-sorted NK-cell subsets stimulated with IL-2 for 5 days (n = 8; mean). (F) Dilution of CFSE on CD57⁻ and CD57⁺ NK-cell subsets expressing 0, 1, 2, 3, or 4 KIRs stimulated with IL-2 for 5 days (n = 9 0KIR, 36 1KIR, 54 2KIRs, 36 3KIRs, 9 4KIRs; mean).