KIR expression positively correlates with IFNγ production. The percentages of CD56⁺CD3⁻–gated NK cells producing IFNγ following incubation with K562 cells were plotted against the percentages of KIR⁺ NK cells or NKG2A⁺KIR⁻ NK cells from both donors and post-HCT recipients of T-cell replete grafts. The estimated regression line is shown with the r value and significance based on the Pearson correlation coefficient. Significance is calculated as P < .05.