Dramatic reduction of pDCs in the absence of CXCR4. E16.5 fetal liver cells (Ly5.2⁺/Ly5.1⁻) from CXCR4^+/− and CXCR4^{−/ −} mice were transferred into lethally irradiated Ly5.2⁻/Ly5.1⁺ recipients. CXCR4^+/− and CXCR4^{−/ −} chimeric mice were analyzed 16 to 45 weeks after transfer. (A-C) Flow cytometric analysis of bone marrow and spleen. Fluorescence staining profile of Ly5.2⁺CD19⁻NK1.1⁻ cells (A), and the numbers of donor-derived Ly5.2⁺CD11c^intB220⁺PDCA-1⁺ pDCs (n = 4-5) and Ly5.2⁺CD11c^hiB220⁻ cDCs (B). (C) Intracellular IFN-α was measured by flow cytometry gating on donor-derived Ly5.2⁺/Ly5.1⁻CD19⁻ cells with or without activation with poly U or CpG-ODN. (D) IFN-α production analysis by ELISA on supernatants from donor-derived Ly5.2⁺/Ly5.1⁻ sorted cells in bone marrow with or without activation with CpG-ODN (n = 3). Error bars represent SD of the mean.