Target cell-induced IFNγ production is decreased after T-cell replete, T-cell deplete, and UCB transplantation. PBMCs from healthy donors and recipients at 1 (T-cell deplete and UCB only), 3, and 6 months post-HCT were incubated in either media alone (not shown), with K562 cells for 4 hours (top and middle panels), or with IL-12 and IL-18 overnight (bottom panel). After incubation, CD107a expression and IFNγ production were measured on CD56⁺CD3⁻–gated NK cells. Bars represent the mean ± SEM. Donors were compared with recipient samples using the Wilcoxon rank sum test; statistical significance is indicated as *P < .05, **P < .01, and ***P < .0001.