Emergence of Lin⁻CD3⁻CD122⁺NK1.1⁻DX5⁻ NK-cell progenitors in different embryonic sites. (A) Typical FACS profiles of Lin⁻CD3⁻CD122⁺NK1.1⁻DX5⁻ NK-cell progenitors analyzed in the liver from 12.5- to 18.5-day-old fetuses. (B) Total number of fetal liver cells and (C) total number of Lin⁻CD3⁻CD122⁺NK1.1⁻DX5⁻ NK-cell progenitors. Data represent mean ± SD values from 5 to 14 livers from fetuses from 2 to 3 litters. Text above the plots and arrows indicate the gating strategies. Numbers in FACS profiles show mean frequencies of populations within the indicated gates relative to total fetal liver cells. Profile from the adult BM is included as a control. The 0 indicates values below the detection level. (D) Representative profiles of Lin⁻CD3⁻CD122⁺NK1.1⁻DX5⁻ NK-cell progenitors in peripheral blood from 12.5- to 18.5-day-old fetuses. Numbers show mean frequencies from 5 fetuses from 2 litters analyzed per time point in 2-3 replicates. *P < .05, **P < .01, and ***P < .0001.