Age-related changes in frequencies of CD57- and c-type lectin-like receptor- expressing NK cell subsets (A). CD56^dim cells were gated into CD57⁻, CD57^intermediate, and CD57⁺ subsets. The CD57⁻ population was gated using an isotype-matched control reagent, and the CD57⁺ gate was set at an MFI of 3000. (B) Frequency distribution by age group of CD57⁻, CD57^int, and CD57⁺ subsets within the CD56^dim NK cell population. Asterisks denote statistically significant trends for changes in NK cell subset frequency by age (***P < .001, F-test). (C) Gating strategy for CD94⁺ cells and (E) CD94 NKG2A⁺ and CD94⁺NKG2C⁺ cells within the CD56^dim NK cell subset. (D) Frequencies of CD94⁺ and (F) NKG2A⁺, and NKG2C⁺ NK cells by age group. Asterisks denote statistically significant differences in frequencies of NKG2A⁺ and NKG2C⁺ cells by age group (*P < .05, analysis of variance). Horizontal bars represent median values, boxes extend from the 25th to the 75th percentile, and whiskers represent the 95th percentiles. Age groups are as shown in Figure 1.