Flow cytometry analysis of cell-surface molecule expression on human adult DCs. Mock- (A) or SARS-CoV–infected (B) adult immature DCs (MOI = 1) were harvested at 48 hours after infection and stained for flow cytometry analysis. Surface staining is shown by filled histogram, and isotype control is marked by the dotted line. SARS-CoV alone did not up-regulate the expression of CD83, CD86, MHC class I, and MHC class II. However, SARS-CoV–infected cells can be stimulated by LPS (10 μg/mL; thick line) to up-regulate the expression of these molecules to similar levels as in the mock-infected controls. Data shown are representative of adult immature DCs from 5 independent donors. FSC indicates forward scatter; SSC, side scatter.