Analysis of apoptotic cells. Apoptotic cells were analyzed by using Annexin V FITC apoptosis ditection kit (Calbiochem, Gibbstown, NJ). A. Control and itonavir (15 and 25 μM) treated MDAH-2774 cells (1 × 105 cells) were fixed stained both with Annexin V FITC and with propidium iodide (20 μg/ml) were processed for flow cytometric analysis. A flow cytometer emitting an excitation light at 488 nm was used to quantify the Annexin V-FITC and propidium iodide signals. Log of FITC signal represented on X axis and log of propidium iodide fluorescence signals were plotted on Y axis. B. MDAH-2774 cells were mixed with annexin V-biotin, incubated for 15 min at room temperature, and treated with streptavidin conjugated to FITC. Apoptotic cells within the same microscopic field were viewed and photographed by phase contrast and by fluorescence emitted at 518 nm (FITC filter) were taken. Using the FITC filter, early apoptotic cells (positive for Annexin V-Biotin-FITC staining) appear bright green.