Bone marrow progenitor cell-intrinsic role of IRF8 in basophil and mast cell development. (A) Bone marrow transplantation experiments. Irradiated WT recipients reconstituted with WT bone marrow cells (WT→WT), irradiated Irf8^−/− recipients reconstituted with WT bone marrow cells (WT→Irf8^−/−), and irradiated WT recipients reconstituted with Irf8^−/− bone marrow cells (Irf8^−/−→WT) for 5 weeks were analyzed as in Figure 1A. Values in the bar graph are means ± standard deviations from 4 mice. Similar results were obtained in 3 other independent experiments. (B,D) fluorescence-activated cell sorter–purified Flt3^– GPs (B) and splenic BMCPs (D) from WT and Irf8^−/− mice were cultured in the presence of IL-3 for 5 or 7 days, respectively, and analyzed by flow cytometry. Data are representative of 3 independent experiments with similar results, and values in the bar graphs are means ± standard deviations from triplicate samples. (C,E) GP transfer experiments were performed to analyze the generation of basophils (C) and mast cells (E). For basophils (C), 10 000 Flt3⁻ GPs from WT or Irf8^−/− mice (CD45.2⁺) were transplanted into irradiated Ly5.1 mice (CD45.2⁻). Donor-derived (CD45.2⁺) splenic basophils were analyzed on day 4. Numbers in parentheses indicate the percentages relative to total cell counts. For mast cells (E), 20 000 Flt3⁻ GPs (CD45.2⁺) with 3 × 10⁵ Ly5.1 bone marrow cells (CD45.2⁻) were transplanted into irradiated mast cell-deficient Kit^W-sh/W-sh mice. CD45.2⁺ mast cells in the peritoneal cavity were analyzed 5 weeks after transplantation. Values in the bar graph are the mean ± standard deviation of 2 independent experiments with a total of 4 mice per group. *P < .05; **P < .01; ***P < .001 (Student t test). NS, not significant.