Origin and differentiation of brain m/chDCs. (A) The indicated numbers of purified MDPs, CDPs, pre-DCs, and monocytes from bone marrow of CD45.1⁺CD45.2⁺ mice were transferred into naive CD45.2⁺ congenic hosts. Dot plots show the phenotype of m/chDCs, and the numbers indicate percentages derived from the donor 7 d after transfer. (B) Dot plots show percentages of CD45⁺Lin⁻CD11c⁺MHC II⁻Flt3⁺SIRPα^lo pre-DCs among bulk brain and meningeal leukocytes. Numbers in the parentheses represent the mean pre-DC percentage of CD45⁺ leukocytes (red arrows, pre-DCs). Histograms show GFP expression of gated pre-DCs in CX₃CR1^gfp (line) versus WT (shaded) mice. (C) CD45.1 and CD45.2 mice were surgically joined for 60 d. Graph shows the percentage of partner-derived T cells, blood pre-DCs, spleen DCs, brain m/chDCs, and microglia. Dot plots show representative percentages of CD45.1 and CD45.2 cells among m/chDCs and microglia in CD45.1 and CD45.2 parabionts. The bar graph shows two independent experiments with more than three mice in total. (D) CD45.2 and CD45.1 B6 mice were surgically joined for 60 d together before being separated. Graphs show the percentage of parabiont-derived DCs among each DC subset in the spleen and brain at different time points after separation. Bars represent two separate parabionts at each time point. (C and D) Error bars show mean ± SEM.