Cell surface marker changesafterpreactivation and induction of human memory-like NK cells. Purified NK cells (≥ 95% CD56⁺CD3⁻) were cultured for 7 days as in Figure 1A and assayed without restimulation for CD94, NKG2A, NKG2C, NKp46, CD69, KIR, and CD57. Representative flow histograms are shown in pre-gated CD56^bright and CD56^dim NK cell subsets, overlaying control cells (open lines) and preactivated cells(gray filled lines). Summary data are shown as means ± SEM percentage of positive or MFI for the marker indicated in CD56^bright and CD56^dim NK cells. CD56^dim NK cells had significantly increased expression of CD94 and NKG2A 7 days after preactivation compared with controls. Both CD56^dim and CD56^bright NK cells had increased CD69 and NKp46 surface expression 7 days after preactivation (n = 4-6; 2 independent experiments) *P < .05; **P < .01; ***P < .001.