Fig. 8. Neutrophil apoptosis and death in S. aureus PSM mutants infected mice.

Blood samples were collected for flowcytometry analyses from NMRI mice (n = 8–9/group) after intravenous infection with S. aureus Newman (wild type, WT), or the isogenic mutant strains Δpsmα or Δpsmβ mutants (4.1–5.4 × 10⁶ CFU/mouse) on day 3 post-infection. a Representative images of gating strategy for neutrophils (upper panel) and apoptosis/death of neutrophils (lower panel). Annexin V indicate apoptotic cell death, while 7-aminoactinomycin (7-AAD) stained nuclei is considered as necrotic cell death. b Neutrophils are gated as Ly6G⁺/F4/80⁻. c Dead neutrophils are gated as Annexin V⁻/7-AAD⁺. d Apoptotic neutrophils at end stage are gated as Annexin V⁺/7-AAD⁺. e Apoptotic neutrophils at early stage are based on Annexin V⁺/7-AAD⁻. The results from two independent experiments were pooled. Data are presented as the median and analyzed with the Mann-Whitney U test. *P < 0.05; **P < 0.01; ***P < 0.001.