DOCK2 deficiency enables engraftment of MHC class I–deficient BM cells. (A) Four days after intravenous injection of WT or β2m^−/− BM cells into lethally irradiated WT (n = 3) or DOCK2^−/− (n = 3) mice, splenic CFU assays were performed in the presence of IL-3 (50 U/mL) or GM-CSF (50 U/mL). Data are expressed as the mean ± SD of 3 mice, and are representative of 2 independent experiments. **P < .01. (B) Four days after intravenous injection of β2m^−/− BM cells into lethally irradiated WT or DOCK2^−/− mice, splenic sections were stained with hematoxylin and eosin. Data are representative of 6 mice per category. Asterisks or arrowheads indicate extramedullary hematopoiesis or megakaryocytes, respectively. The lower panels indicate high-magnification images of the boxed area. Black bar, 500 μm; White bar, 50 μm.