moDCs infected by the endothelial cell adapted TB40/E HCMV strain down-regulate major histocompatibility complex class I and II expression. Immature moDCs were incubated overnight with complete medium (MOCK), HCMV (TB40/E), or UV-inactivated HCMV (UV-TB40/E). (A) Cells were stained at 48 hours after infection with a mouse anti-CMV IE-1/IE-2 monoclonal antibody (right panels, FITC) and 4′,6-diamidino-2-phenylindole nuclear staining (left panel). Images were analyzed as described in “HCMV preparation, sequencing of UL40 gene, and infection of moDCs.” (B) Histograms represent the percentages of IE-1/IE-2⁺ cells detected in 8 independent experiments (mean ± SD). (C) Flow cytometry performed at 72 hours after infection. moDCs were surface labeled by indirect immunofluorescence with mAbs specific for HLA class I, class II (HLA-DR), or CD83 mAbs (open histograms represent isotype control; and filled histograms, specific staining). Results of a representative experiment (60% IE-1/IE-2⁺ cells) of 4 performed are shown.