Association of pDCs with cellular niches in the bone marrow of wild-type and CXCR4-deficient mice. (A,B) Bone marrow sections from CXCL12/GFP knock-in mice stained with antibodies against PDCA-1 (red) and PECAM-1 (white) (A). Many PDCA-1⁺ pDCs (arrows; red) are found in close association with CAR cells (green) in the intersinal space (A). S indicates vascular sinus. Scale bars equal 10 μm. (B) Frequency of PDCA-1⁺ pDCs in contact with CAR cells and CAR cells surrounding morphologically identifiable PECAM-1⁺ sinusoidal endothelial cells or residing near the bone surface. (C) Flow cytometric analysis of the numbers of LSK Flt3^lo primitive hematopoietic cells and CD11c^intB220⁺PDCA-1⁺ pDCs in bone marrow of pIpC-treated CXCL12/GFP/MxCre/CXCR4^f/wt mice, untreated CXCL12/GFP/MxCre/CXCR4^f/null mice, and pIpC-treated CXCL12/GFP/MxCre/CXCR4^f/null mice 1 week after the final pIpC treatment (n = 3). (D) Bone marrow sections from pIpC-treated CXCL12/GFP/MxCre/CXCR4^f/wt (left) and CXCL12/GFP/MxCre/CXCR4^f/null mice (right) stained with antibodies against PDCA-1 (red). Many PDCA-1⁺ pDCs (arrows; red) are found in close association with CAR cells (green) in pIpC-treated CXCL12/GFP/MxCre/CXCR4^f/wt mice (left), but PDCA-1⁺ pDCs are undetectable in pIpC-treated CXCL12/GFP/MxCre/CXCR4^f/null mice (right). Scale bars equal 10 μm.