Fig. 1: Recruitment of neutrophils to sites of infection.

a Representative time sequence (maximum intensity z-projection) of vascular colonization by iRFP-expressing Neisseria meningitidis (green). The human and murine endothelia were distinguished using UEA-1 lectin (dashed lines) and mouse-specific anti-CD31 (red) staining, respectively. Time, hh:min. Pictures shown are representatives of N = 6 mice. Scale bar, 50 µm. b Representative images (maximum intensity z-projection) of non-infected (NI) and infected human graft tissue sections at indicated times post infection (p.i.) with GFP-expressing Neisseria meningitidis (green) and stained for the human endothelium (UEA-1 lectin, gray) and neutrophils (GR-1, magenta). Pictures shown are representative of N = 3 mice per condition. Scale bar, 10 µm. c Quantification of neutrophil numbers in human xenografts of non-infected (−, gray circles) and infected (+, purple circles) mice at the indicated times post infection (p.i.). Neutrophil numbers in contralateral mouse skin at 16 h post infection is shown on the right (white circles). Two-tailed Mann–Whitney test (3 h, 6 h, 24 h) and two-tailed Kruskal–Wallis test with Dunn’s correction (16 h). n = 7 (16 h p.i.), 8 (3 h, 16 h non-infected; 6 h p.i.), 9 (3 h p.i., 6 h non-infected), 10 (mouse skin, 16 h p.i.), 18 (24 h non-infected), and 21 (24 h p.i.) mice, pooled from N = 3 (3 h, 6 h, 16 h p.i.) and 5 (24 h p.i.) independent experiments. d Movies obtained from intravital imaging were used to quantify the numbers of neutrophils per square millimeter of endothelium during the first 6 h of the infection. Quantifications were performed on n = 56 vessels, pooled from N = 7 infected mice imaged independently. c, d Data are shown as the mean ± SEM. e Intravital imaging (maximum intensity z-projection) of neutrophil (LysM^GFP/+, magenta) recruitment at 16 h post infection with iRFP-expressing Neisseria meningitidis (green) in grafted Rag₂^−/−γ_c^−/−LysM^GFP/+ mice. Dashed lines delineate the human endothelium, stained using the UEA-1 lectin. The left panel shows an important swarm of neutrophils around the infected vessel. Time, hh:min. Scale bars, 50 µm. The right panel shows the directed migration of neutrophils towards the infected vessel as revealed by cell tracking over 30 min. Pictures shown are representative of N = 3 mice. Scale bar, 50 µm.