Frozen PBMCs from adult donor T cell depleted grafts (d28 post transplant) were thawed, rested overnight, and placed in culture with 10 ng/ml IL-15 and OP9-N, OP9-DL1, or OP9-DL4 cells for 7 days. NK cell effectors alone (open bars/Eff) or after 5 hour co-culture with K562 target cells (filled bars/Eff+Targ) were assessed for (A) CD107a, (B) IFNγ, and (C) TNFα (n = 10). (D) CD16 was also measured on these cells to determine if Notch modulates expression on clinical samples (n = 10). Given the stark differences between controls (Eff) and activation group (Eff+Targ) repeated measures ANOVA with Tukey’s multiple comparison test was carried out individually within those groups.