EBV induces apoptosis in human neutrophils. Cells were cultured in the presence or absence of EBV and were obtained at 4, 10, and 20 hours posttreatment for DNA staining as described in Materials and Methods. Uptake of dyes was evaluated by flow cytometry. (a through c) Unstimulated cells cultured for 4, 10, and 20 hours, respectively. (d through f) EBV-treated neutrophils cultured for 4, 10, and 20 hours, respectively. N, necrotic cells; V, viable cells; V₁, V₂, V₃, three smaller groups of viable cells, from the more viable to the less viable cells, respectively; A, apoptotic cells. Numbers indicate the percentage of positive cells. The results displayed in each histogram are representative of seven experiments. After 20 hours of culture, the percentages of apoptotic cells in controls and in EBV-treated cells are 26% ± 8% and 68% ± 14% (n = 7), respectively. Values are significantly different atP < .05.