GM-CSF promotes pDC survival and differentiation into DCs. (A) GCRMA-normalized Affymetrix expression values of cytokine and growth factor receptor chains on pDCs freshly isolated from the blood of healthy donors. The dashed line is the threshold of signal detection. Black bars represent the mRNA levels of the heterodimeric cytokine and growth factor receptors expressed on pDCs; gray bars, the receptors for which we detected only one chain; and white bars, the chains not detectable. Data are the mean of 7 independent experiments each from different donors. Error bars represent SD. (B) Cytokine receptor expression at the surface of freshly isolated pDCs. Filled histograms represent specific staining for receptors; and open histograms, isotype-matched controls. Inset values indicate mean fluorescence intensities over all cells. Data are from one representative of 5 independent pDC experiments each from different donors. (C) pDC viability and maturation after 48 hours of culture in the absence (Med) or presence of recombinant IL-3, IL-6, IL-10, IL-18, IFN-γ, and GM-CSF. Viability is expressed as percentage of 4,6-diamidino-2-phenylindole-negative pDCs. The specific mean fluorescence intensity (MFI) of CD80 is over all the viable pDCs. Data are the mean of 5 or more independent experiments each from different donors. Error bars represent SEM. ***P < .001. **P < .005. (D) Giemsa staining of ex vivo pDCs compared with IL-3– and GM-CSF–treated pDCs (original magnification ×1000).