Neutrophils from mice or human were suspended at 1610 6 cells/mL in RPMI-1640 medium. Degranulation was induced by adding fMLF (Sigma-Aldrich, Saint Louis, MO 63103) to a final concentration of 100 nM followed by incubation at 37uC for 30 min. FITC-labeled E. coli (30610 6 cells/mL) with either Opa 52 or vector control were added to neutrophils (neutrophil/bacteria; 1/30) and incubated at 37uC for 60 min. Infection was arrested by washing the neutrophils with PBS three times.