FLT3 ligand is dispensable for generation, reconstitution, and posttransplantation expansion of fetal liver HSCs. (A) Representative FACS plots of LSKFLT3⁻CD150⁺ cells in day 14.5 fetal liver from WT and Fl^−/− mice. Cells have first been gated as Lin⁻ as indicated. Numbers indicate frequencies of populations within indicated gates or quadrants of total fetal liver cells. (B) Mean (SEM) numbers of LSKFLT3⁻CD150⁺ cells in day 14.5 fetal liver of WT and Fl^−/− mice (n = 5 per genotype). (C-E) Liver cells (2 × 10⁵) from WT and Fl^−/− day 14.5 fetuses (CD45.1) were transplanted into lethally irradiated adult WT and Fl^−/− recipients (CD45.2), respectively. Fetuses from at least 2 different litters were used. (C) Mean (SEM) donor-derived total B, T, and myeloid (M) reconstitution in PB at 16 weeks after transplantation from 9 recipient mice of each genotype. (D,E) Mean (SEM) total number (per 2 tibiae and 2 femora) of donor-derived Mac-1⁺ myeloid cells (D) and LSKFLT3⁻ cells (E) in the BM of recipient mice (9 per genotype in 2 experiments) 16 weeks after transplantation. ns indicates not significant; ***P < .001.