Figure 3. Bactericidal activity of neutrophils and defensins.

(A and B) Neutrophils isolated from blood as described above were incubated with S. aureus or K. pneumoniae at a MOI (bacteria: neutrophils) of 1:1 and 1:10, respectively, and incubated for 10 minutes, after which neutrophils were pelleted by centrifugation and resuspended in HBSS. Samples were taken immediately (time 0) and after 10 and 30 minutes. Neutrophils were lysed in water pH 11 to liberate intracellular bacteria. These were enumerated by CFU after overnight incubation. All experiments were run in triplicate. Results are expressed as CFU relative to time 0. (C and D) Defensins isolated from human neutrophil azurophil granules were incubated with S. aureus or K. pneumoniae for 1 hour at 37°C. The number of surviving bacteria was enumerated as CFU after overnight incubation. Results are expressed as CFU relative to control without defensin.