Development of homogeneously mature NK cells from hESCs. (A) Phenotypic analysis of hESC-NK cells compared with UCB-NK cells. hESC- and UCB-derived progenitors cultured in NK-cell conditions for 30 days were evaluated by flow cytometry for surface antigen expression. Two distinct populations, CD117⁺CD94⁻ and CD117^−/lowCD94⁺, are found in UCB-derived cells, whereas almost all hESC-derived cells are CD117^−/lowCD94⁺. Additional analysis for CD94 and CD16 expression on the CD56⁺ cell population also demonstrates distinct differences between the hESC and UBC-NK cell populations. (B) Time-course analysis for expression of CD117 and CD94 on CD56⁺ NK cells. Cells were harvested after 14, 23, and 30 days in NK culture. FSC indicates forward scatter; and SSC, side scatter.