Fetal liver monocytes differentiate into LC precursors. Monocytes were purified from E13.5–E14.5 fetal liver of Cx3cr1gfp/+CD45.1+ mice and adoptively transferred in utero into unconditioned E13.5–E14.5 CD45.2+ congenic embryos. (A–C) Flow cytometry analysis of the progeny of adoptively transferred CD45.1+ monocytes (A) in the blood (B) and skin (C) 3 h after injection. (A) Gating strategy (top) for monocytes among fetal liver leukocytes (DAPI−CD45+), purity after sorting (middle), and profile of expression for Gr-1 and CX3CR1/GFP (bottom). (B and C) Percentage CD45.1+ donor-derived monocytes among total CD45+ cells (top), expression of CD11b and F4/80 (middle), and Gr-1 and CX3CR1/GFP (bottom) among indicated populations. (D) Percentage cells derived from donor monocytes for each injected embryo (n = 7) in E14.5 blood and skin 3 h after transfer. Control represents noninjected embryos (n = 9). Bars show means of data from one representative experiment of three. (E) Percentage populations P1 (CD11bhiF480lo) and P2 (CD11bloF480hi) on gated DAPI−CD11b+F480+CD45.1+ donor-derived cells isolated from the skin at indicated time points after transfer (E14.5) and their corresponding profile of expression for Gr-1 and CX3CR1/GFP. (F) Percentage population P2 on gated DAPI−CD11b+F480+CD45.1+ donor derived cells isolated from the skin at indicated time points after transfer. Error bars represent mean ± SEM of pooled data from two experiments (n = 3 to 8). (G) Graph shows the percentage of skin CD11b+F4/80+ cells derived from donor fetal liver monocytes (white squares) or donor fetal liver Ter119+ erythroid progenitors (gray squares; n = 4–11) for each injected embryo at the indicated time points. Bars represent means of data at each time point. ***, P < 0.0001; *, P < 0.01.