Surface activation marker expression of PDCs after exposure to extracellular nucleotides. PDCs were cultured with IL-3 in the absence or presence of 250 μM ATP or UDP. Where indicated, 1 μg/mL CD40L trimers was added. After a culture period of 36 hours, surface expression of CD83, CD86, HLA-DR, CCR7, and CD62L was assessed by flow cytometry. In the upper panel, data are expressed as n-fold change of mean fluorescence intensity (MFI) with expression levels of IL-3–cultured PDCs normalized to 1. Means of x-fold changes (± SEM) of 4 to 6 different donors are shown. In the lower panel, histogram plots with MFI of PDCs from a representative donor are shown.