Fig. (3) Detection of intracellular HIV-1 expression in CD8+ T-cells. CD8+ T-cells were infected with 300 TCID₅₀/mL of HIV_IIIBor left uninfected. (A) Intracellular p24 was examined on the CD8+ T-cell population by flow cytometry at day 15 post-infection with antibodies to HIV-1_gag (p24-RD1) and CD8. In the infected population, the number in the upper right quadrant represents the number of cells found in the circle as to minimize any false-positives. (B) To determine the contribution of CD4+ cells to in vitro CD8+ T-cell infection, intracellular HIV-1 expression was examined in the CD8+ T-cell population by flow cytometry at day 15 post-infection with antibodies to HIV-1_gag and CD4 only. Numbers in the quadrants represent the percentage of gated cells in each quadrant. A minimum of 10, 000 events was assessed for each analysis.