Bivariate cyclin B expression versus DNA content distributions (scatter plots) in uninfected (top panels) and HHV-7–infected (bottom panels) SupT1 cells. Cell cycle expression of cyclin B was evaluated by simultaneous staining with propidium iodide and anti-cyclin B MoAb followed by an FITC-conjugated MoAb. Staining of uninfected and HHV-7–infected SupT1 cells with a isotype control MoAb before FITC-conjugated secondary antibody is shown in the left panels. Cyclin B-FITC fluorescence intensity is plotted on the X axis, and fluorescence intensity of propidium iodide DNA staining is plotted on the Y axis. The insets show the percentage of cells, calculated after removal of the apoptotic cells, with a G₁(2n), S, G₂M(4n), and >4n DNA content. The cell populations showing high cyclin B expression, based on DNA content, are marked by arrows. A representative analysis of three separate experiments, performed at 12 days p.i., is shown.