Self-KIR educate for cytotoxicity and IFNγ production, and low-dose IL-15 exposure restores the post-HCT defect in IFNγ response. (A) Single KIR⁺NKG2A⁻ NK cells from both donors and post-HCT recipients of T-cell replete grafts were grouped as expressing either self-KIR (black bars) or non-self KIR (white bars) based on the donor or recipient KIR ligand status. Bars represent the mean ± SEM. NK cells expressing self-KIR were compared with NK cells expressing non-self KIR using the paired Student t test. Statistical significance is indicated as *P < .05. (B) PBMCs from recipients 3 months after transplantation with T-cell replete grafts were incubated overnight in media alone (squares) or media containing 1 ng/mL IL-15 (triangles). They were then tested for response induced by K562 exposure; CD107a expression and IFNγ production were measured on CD56⁺CD3⁻–gated NK cells. The paired Student t test was used to compare the function of cells incubated in media versus media containing 1 ng/mL IL-15. Statistical significance is indicated as *P < .05 and **P < .01.