CD57 is preferentially expressed on NKG2C⁺ NK cells. CD56^dim NK cells were gated as in Figure 1A, and the frequency of CD57⁻, CD57^int, and CD57⁺ cells is shown within (A) CD94/NKG2A⁺ or (B) CD94/NKG2C⁺ NK cells, by age group. (C) MFI for CD57 expression on NKG2A⁺ and NKG2C⁺ NK cells by age group. Horizontal bars represent median values, boxes extend from the 25th to the 75th percentile, and whiskers represent the 95th percentiles. Asterisks denote statistically significant trends by age within each subset (**P < .01; ***P < .001, F-test). Age groups are as shown in Figure 1.