ArhGAP15 regulates neutrophil-mediated phagocytosis, ROS generation, and in vitro bacterial killing. (A) Representative images of E. coli (red) phagocytosed by neutrophils (Gr-1 staining in green). (B) Quantification of Texas Red fluorescence (E. coli) in ArhGAP15^+/+ and ArhGAP15^−/− neutrophils; n ≥ 100 cells/genotype. (C-D) ROS generation by neutrophils induced by (C) 2.5μM fMLF or (D) 100nM C5a; n = 5/genotype. (E) Quantification of MPO release by ArhGAP15^+/+ and ArhGAP15^−/− neutrophils; n = 4/genotype. (F-G) Determination of Rac2 activation after C5a stimulation in neutrophils. Representative detection of active (Rac2-guanosine triphosphate) and total Rac2 is shown. Normalization was obtained by setting the percentage stimulation of ArhGAP15^+/+ neutrophils after 15 seconds for 100%; n = 5/genotype. (H) In vitro killing of E. coli by isolated ArhGAP15^+/+ and ArhGAP15^−/− neutrophils; n = 4/genotype. #P < .05. **P < .001.