IL-21 stimulation does not affect TLR-induced pDC maturation. Surface expression of the costimulatory molecules CD80, CD86, and CD40 and expression of HLA-DR and CCR7 were measured by flow cytometry on blood pDCs that were cultured in medium, IL-21 (25 ng/mL), R848 (10 μg/mL), or R848 plus IL-21 for 1 or 2 days. (A) Histograms representing the level of protein expression as indicated after 2 days of culture. One representative experiment out of 2 is depicted. Medium, dark gray–shaded histogram; IL-21, light gray–shaded histogram; R848, black line open histogram; R848 plus IL-21, gray line open histogram. (B) Mean fluorescence intensities (MFIs) were calculated based on the flow cytometry data as described in A after 1 and 2 days. Shown are the mean MFIs of 2 experiments. Error bars indicate standard deviation values.