CpG induced down-regulation of CMRF-35 binding is IFN-α dependent. (A) pDCs cultured with CpG or IFN-α (10 ng/mL) for 24 and 48 hours were analyzed for CD300a/c expression by flow cytometry using CMRF-35 mAb. Open histogram indicates without IFN-α; filled with gray histogram, with IFN-α; filled with slash line, with CpG. (B) Histograms displaying the binding of CMRF-35 mAb to pDCs that were incubated with either control ODN (− CpG), CpG (+ CpG), anti–IFN-α + CpG or control IgG + CpG for 48 hours. Open histogram with dashed line indicates isotype control. (C) Real-time PCR analysis of CD300a and CD300c mRNA in pDCs cultured with control ODN, CpG, or anti–IFN-α + CpG for 24 hours. Data are representative of 3 experiments. Error bars represent SEM.