Intracellular cytokine staining for IFN-α and TNF-α in pDCs upon 1 μM R-848 stimulation. a pDCs were gated as CD123+CD303+ cells in infant PBMC (left column) after selection for live (Live/Dead Aqua -), single, and large mononuclear cells. All IFN-α producing pDCs upon 1 μM R-848 stimulation also produced TNF-α (right column). One representative example of the gating strategy in infant PBMC is shown. b The percentage of IFN-α + pDCs, c but not TNF-α + pDCs, is higher in female infants compared to male infants upon 1 μM R-848 stimulation. Infant age = 2.1 [1.6-3.8] months (median [95 % CI]). Unstimulated background is subtracted from the values. Bars = median values. Comparisons were performed using the non-parametric Mann Whitney U test. P-values < 0.05 were considered significant.