Figure 3. Apoptotic cell death of HRCEC treated with HIV-1 gp120. After being treated with gp120 at concentrations of 0.08, 0.1, 0.12, and 0.15 mg/l for 24 h, apoptotic cells were analyzed using the annexin V-FITC/PI double marked method by FCM. Early apoptotic cells were annexin -positive but PI-negative (left blank plots); late apoptotic ells were annexin V- and PI-positive (right corrugated plots). The ratio of apoptotic cells increased significantly with the increase of protein concentration. #p<0.01 compared with control. Data represent the mean±SD of three independent experiments.