Phenotypic and functional analysis of hESC-NK cells compared with UCB-NK cells. (A) Flow cytometric analysis for 4 individual KIRs demonstrates a higher percentage of hESC-NK cells expressing these regulatory receptors compared with what is found on UCB-NK cells. (B) Expression of CD161 and NKp44 on hESC- and UCB-NK cells. (C) Expression of perforin and granzyme B on CD56⁺ NK cells was evaluated by intracellular flow cytometric straining. Histograms of CD56⁺-gated cells are shown. Mean fluorescent intensity (MFI) was analyzed from all hESC-derived CD56⁺ cells and from perforin and granzyme B-positive CD56⁺ cells from UCB. Isotype control is indicated in open histograms. (D) Cytolytic activity against K562, PC3, and MCF7 tumor cells was compared between purified CD117^−/lowCD94⁺ NK cells derived from hESCs (□) and UCB () at the indicated effector-to-target cell ratios. Representative results from 2 separate experiments are shown. (E) Flow cytometric analysis of cell trafficking molecules on hESC- and UCB-derived NK cells. Histograms of CD56⁺-gated NK cells are shown. Open histogram indicates isotype control.