Pre-NKP and rNKP in vivo–derived NK cells are phenotypically mature and give rise to NK cells on transplantation faster than CLP or LMPP. (A) 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 mature NK cell markers CD27 and Mac1. Each progenitor type was injected into 5 individual mice per experiment. Data are representative of 1 of 2 experiments. (B) Ly5.2⁺ progenitors where transplanted into unconditioned Ly5.1⁺ DKO mice. Mice where bled every week and analyzed by flow cytometry for donor NK cell reconstitution. Pre-NKP gave rise to NK cells as early as 1 week and were exhausted after 3 weeks. CLP gave rise to few, but detectable NK cells at 1 week and also became exhausted by 4 weeks. We observed no NK cells at 1 week in the LMPP transplants, but by 2 weeks they where comparable to both pre-NKP and CLP. Each progenitor type was injected into 5 individual mice per experiment. Data are representative of 1 of 2 experiments. (C) Absolute number of donor-derived NK cells from the spleens of mice transplanted with different progenitors. Data are representative of 1 of 2 experiments.