Evaluation of cell cycle progression in HIV productively infected cells. CD4⁺ isolated and infected cells were stained with p24 and Ki67 (A-C), p24 and CSFE (D-F), p24 and 7AAD/pyronin (G-I), or p24 and PI (J-L) to discriminate between bystander and HIV-infected subpopulations. Uninfected cells were treated and stained similarly. Histograms are of data from 1 donor, representative of at least 3 donors. In panels G-I, the lower left quadrant designates cells in G₀; lower right quadrant designates cells in G₁; and upper right quadrant designates cells in S/M stage of the cell cycle. In panels J-L, the first peak designates hypodiploid cells; the second peak is G₁; the third peak is S, and the fourth peak is the G₂/M stage.