KIR⁺NKG2A⁻ NK cells are decreased and KIR⁻NKG2A⁺ NK cells are increased after HCT. CD56⁺CD3⁻–gated NK cells from donors (black bars) and post-HCT recipients (white bars indicate T-cell replete; light gray bars indicate T-cell deplete, and dark gray bars indicate UCB) at 3 and 6 months were further gated based on staining with a cocktail of KIR antibodies and NKG2A into KIR⁻NKG2A⁻, KIR⁻NKG2A⁺, KIR⁺NKG2A⁺, or KIR⁺NKG2A⁻ populations. Bars represent the mean ± SEM frequency of each NK cell population. Donors were compared with recipient samples using the Wilcoxon rank sum test; statistical significance is indicated as *P < .05, **P < .01, and ***P < .0001.