Myeloid progenitors in second trimester liver and bone marrow from DS and normal gestation-matched fetuses. MEPs, CMPs, and GMPs were analyzed by flow cytometry of freshly isolated fetal liver (FL) mononuclear cells (MNCs) (n = 10 with DS and n = 5 normal) and fetal bone marrow MNCs (n = 4 with DS and n = 4 normal). The gating strategy used to identify the MEP compartment, defined as CD34⁺CD38⁺CD123⁻CD45RA⁻, is shown in panel A, representative plots show the proportion of MEPs in DS-FL cells (Bii,iii), gestation-matched normal FL (Bi), DS fetal bone marrow (Cii), and gestation-matched normal fetal bone marrow (Ci). The frequency of MEP was significantly higher in DS-FL compared with normal FL (P < .001), whereas the proportions of CMPs (P = .002) and GMPs (P = .025) were significantly reduced (Biv). There were no significant differences between the frequency of MEPs, CMPs, and GMPs between DS and normal fetal bone marrow (Ciii). Data are means plus or minus SEM.