Exposure of phosphatidsylserine in ISAV infected cells. A. Representative AV/PI flow cytometric dot-plots of ASK cells. Left panel = mock, right panel = 5 days p.i. with ISAV 4. One representative experiment out of three is shown. The lower left quadrant represents viable cells (negative for both AV and PI). Early apoptotic ASK cells in the lower right quadrant exclude PI, demonstrating cytoplasmic membrane integrity. AV+PI positive cells are shown in the upper right quadrant considered to be late apototic or early necrotic cells. The upper left quadrant displays cells that take up PI, considered to be necrotic or dead cells. B. Percentages of cells in the quadrants regarded as viable (upper panel) and AV+PI positive (lower panel). Virus isolates statistically significantly different from mock is marked with an asterisk.