Characterization of CCR9⁻ and CCR9⁺ PDCs in murine bone marrow. Expression of the indicated markers was analyzed by FACS in primary BM cells. Dot plots show expression of CD11c versus BST2 in propidium iodide-negative cells and expression of BST2 versus CCR9 in BST2⁺ CD11c⁺ cells. Expression of the indicated markers in CCR9⁺ and CCR9⁻ BST2⁺ CD11c⁺ cells is shown below (overlay with fluorescence minus one [FMO] control, filled histograms) (A). Relative mRNA expression was quantified in CCR9⁺/BST2⁺/CD11c⁺ and CCR9⁻/BST2⁺/CD11c⁺ PDC populations sorted from primary BM cells by quantitative RT-PCR (B, mean ± SD, n = 3). Immunoglobulin D_H-J_H rearrangement was detected by PCR in genomic DNA isolated from CCR9⁺ and CCR9⁻ PDCs (C). CCR9⁺ and CCR9⁻ PDCs were incubated with medium or CpG 2216 for 24 hours. IFN-α, IL-12p40, and IL-6 were measured in the supernatants by ELISA (D, mean ± SD, n = 3). *P < .05. **P < .01. ***P < .001. n.s. indicates not significant.