Common myeloid progenitors from Irf8^−/− mice overproduce neutrophils at the expense of DCs in vitro and in vivo. Common myeloid progenitors (CMP) were double-sorted from the BM of Irf8^−/− or wild-type controls. (A-B) One thousand progenitors were cultured for 7 days in the presence of Flt3 ligand, IL-3, GM-CSF, and SCF (all 10 ng/mL). DC and neutrophil output was analyzed by flow cytometry. Data show averages from 5 wells and represent 3 independent assays. (C-D) Four thousand common myeloid progenitors from Irf8^+/+ or Irf8^−/− were injected intravenously into each 800 cGy-irradiated (C57BL/6 × B6.SJL) F1 recipient (CD45.1⁺CD45.2⁺). BM and spleens were harvested 10 days after transplantation and the development of DCs and neutrophils was analyzed by flow cytometry. Data shown are for 6 mice in each experimental line pooled from 2 independent experiments with 3 mice per group; **P < .05.