FIG 2 .

S. pneumoniae sialidase NanA increases neutrophil IL-8 secretion and extracellular trap (NET) formation. (A) Neutrophils were infected with WT S. pneumoniae or ΔNanA mutant (MOI = 10) for 1 or 2 h, and IL-8 released into the culture supernatant was measured by ELISA. Experiments were done twice with biological duplicates from two different donors. (B) Quantification of NETs after coincubation of neutrophils with WT S. pneumoniae or ΔNanA mutant at an MOI = 0.1 for 90 min. Cells were fixed and stained with primary rabbit anti-myeloperoxidase (anti-MPO) antibody followed by a secondary Alexa 488-conjugated goat anti-rabbit antibody to visualize NETs (green). DNA is stained with DAPI (blue). Representative immunofluorescence micrographs of NETs are shown in panel C, and quantitative results are shown in panel B. Statistics analysis was performed using Student’s t test. **, P < 0.01.