PMN apoptosis during chronic infection of rhesus macaques with the pathogenic SIVmac251 strain. Panels A, B, and C show the gating strategy to quantify apoptosis. A) Dot plot showing anti-CD11b-PE staining against the side-scatter parameter. A first gate (R1) was drawn around CD11b+ cells. B. Dot plot showing anti-CD11b-PE and anti-CD14-FITC staining, gated on R1. A second gate (R2) was drawn on CD14low cells in order to eliminate monocytes (CD14high cells) from the analysis. C) The combination of annexin V-APC and 7-AAD staining distinguished early apoptotic cells (annexin V+, 7-AAD-) and late apoptotic cells (annexin V+, 7-AAD+) in an SIV- macaque and in an SIV+ macaque moderate progressor (SIV+ MP) (day 240) after incubating whole blood at 37°C for 4 hours (T4h). Panel D. Eleven SIV+ (six slow progressors, SIV+ SP and five moderate progressors, SIV+ MP) and four SIVΔnef macaques were studied after 8 months of infection. Apoptosis was studied after incubating whole blood at 37°C for 4 hours (T4h). Results are expressed as percentage of annexin V+/7-AAD- cells (early apoptotic cells). Data are reported as means ± SEM. Comparisons were based on ANOVA and Tukey's posthoc test, using Prism 3.0 software. * Significantly different from healthy controls (SIV- group) (p < 0.05); † Significantly different from SIVΔnef macaques (p < 0.05); †† Significantly different from SIV+ SP (p < 0.05).