The KIR expression frequency correlates linearly with KIR gene copy number. Frequency of CD56^dim NK cells expressing the indicated inhibitory (A) and activating (B) KIR stratified based on KIR gene copy number. (C) Representative examples of expression of the indicated KIR in donors with distinct copy numbers. (D) Frequency of 2DL1⁺ (top) and 2DL3⁺ (bottom) NK cells within the indicated subsets and stratified based on KIR gene copy number. Red dots represent the donors with statistical outliers identified by the Chauvenet algorithm. **P < .01; ***P < .001.