Pre-NKP and rNKP are lineage restricted to the NK cell fate in vivo. CD45.1 unfractionated BM, CLP, pre-NKP, and rNKP were transplanted into unconditioned congenic CD45.2 Rag2−/−IL2rγc−/− recipients. Spleens 3 weeks after transplantation were isolated and analyzed by flow cytometry for lineage potential of donor cells. Each progenitor type was injected into 5 individual mice per experiment. Data are representative of 1 of 5 experiments.