CD57 is preferentially acquired on NKG2C⁺ cells in the first year after CMV reactivation. CD57 co-expression was measured on NKG2C⁺ (○) and NKG2C⁻ (■) NK cells from recipients without CMV infection (top panel) and with CMV infection (bottom panel). The ratio of CD57⁺/CD57⁻ was plotted at the indicated time points. Points represent the means ± SEM. The slope of time for NKG2C⁺ NK cells was compared between recipients who reactivated CMV and those who did not using a linear mixed model, P = .0015.