Down-regulation of MHC-I expression by KSHV. Results represent at least 3 independent infections with different KSHV batches and error bars correspond to standard deviation from the mean. (A) Representative dot plot of MHC-I expression in LECs and in KLECs, showing that MHC-I down-regulation increases with GFP expression (axes are logarithmic). The percent of cells of the total and geometric mean (geomean) fluorescence are shown for each quadrant. (B) Increasing amounts of KSHV resulted in a proportionate increase of GFP-expressing cells and decrease of MHC-I⁺ cells among the infected cells; •, percentage of GFP-expressing cells after infection; ○, percentage of MHC-I–expressing cells among the GFP⁺ cells. (C) Representative experiment of levels of MHC-I fluorescence at 4 and 8 days after infection for LECs (▪) and GFP expressing KLECs (⊡). (D) Induction of MHC-I surface expression by IFN. LECs and KLECs (3 days after infection) were cultured for 24 hours in the presence of IFN-α (150 U/mL) or IFN-γ (1000 U/mL). The graph shows the fold increase in MHC-I expression in LECs and KLECs after IFN treatment compared to MHC-I expression of untreated LECs and KLECs, respectively. (E) Fold increase in HLA-A mRNA levels in LECs and KLECs after IFN-α treatment. Expression of HLA-A in noninfected and infected cells is normalized to HLA-A levels of untreated LECs and KLECs, respectively. In panels C-E, ▪, LEC levels; ⊡, KLEC levels.