Role of GM-CSF for differentiation of CCR9⁻ PDCs to CD11b⁺ MHCII^high CDC-like cells. Neutralizing antibody against GM-CSF (1 μg/mL) was added to IEC-SN or medium 2 hours before addition to FL-DCs for 48 hours (A-B). The percentage of BST2^high PDCs of all CD11c⁺ cells was determined by FACS (A, mean ± SD, n = 3). CpG 2216 (0.5μM) was added after 24 hours, and cytokines were measured in the supernatants after further 24 hours (B, mean ± SD, n = 3). *P < .05. n.s. indicates not significant. CCR9⁺ and CCR9⁻ PDCs sorted from primary BM cells were cultured with medium alone or medium supplemented with Flt3L (20 ng/mL), M-CSF (1 ng/mL) or GM-CSF (1 ng/mL) for 48 hours. Expression of CD11c and BST2 was measured by FACS. Results of one representative experiment are shown (C).