Expression of MHC class I and MHC class II. Expression of (A) MHC class I (HLA-ABC) and (B) MHC class II (HLA-DR) was measured by flow cytometry on freshly isolated human CD1c⁺ mDCs, CD16⁺ mDCs, BDCA3⁺ mDCs, and pDCs and DC stimulated overnight with TLR ligands (4 μg/mL R848 for pDCs, 4 μg/mL R848 and 2 μg/mL poly(I:C) for mDC subsets). The graphs show the mean ± SEM of the MFI of at least 4 independent experiments. Significance was determined by unpaired Student t test (*P < .05).