Figure 2

Flow cytometric analysis of H5N1 NS-induced apoptosis. The dot plot diagrams represent typical apoptotic and necrotic cell populations detected by Annexin V-FITC and PI staining. A. A549 cells transfected with the empty PCMV-Myc vectors. B. A549 cells transfected with pCMV-Myc/NS1. The lower left quadrants of the panels show viable intact cells, which were negative for Annexin V-FITC binding and excluded PI staining (FITC^-/PI^-); the upper right quadrants show nonviable, necrotic cells, which were positive for Annexin V-FITC binding and PI uptake (FITC⁺/PI⁺). The lower right quadrants represent apoptotic cells, positive for Annexin V-FITC and negative for PI (FITC⁺/PI^-).