m/chDCs express Flt3 and have an intrinsic dependence on Flt3L. (A) Histograms show cell surface expression of Flt3 receptor and M-CSF receptor (CD115; line) or isotype antibody control (shaded area) on gated microglia and m/chDCs in the brain versus CD8⁻ and CD8⁺ DC subsets in the spleen (Sp). (B) Bar graph shows percentage of m/chDCs and microglia among CD45⁺ brain leukocytes in WT versus Flt3L KO mice. Bars represent data from two pooled experiments (n = 4). Error bars represent the mean ± SEM (n = 4). (C) Lethally irradiated CD45.1⁺CD45.2⁺ F1 recipient mice were reconstituted with a mixture of 50% CD45.1⁺ Flt3 KO and 50% CD45.2⁺ WT bone marrow and analyzed 2–3 mo later. Bar graph shows the percentage of indicated cells from Flt3 KO CD45.1⁺ (open) and WT CD45.2⁺ (red) donor or CD45.1⁺CD45.2⁺ recipient (blue) origin. Bars represent data from three animals. Error bars represent the mean ± SEM (n = 3; *, P < 0.05; **, P < 0.01). Dot plots show percentage of donor and recipient cells in gated cell populations analyzed by flow cytometry, representing two independent experiments.