Neutrophils from p40 ^phox−/− mice exhibit severe defects in NADPH oxidase regulation and oxidant-dependent bacterial killing

Abstract

The generation of reactive oxygen species (ROS) by the reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex plays a critical role in the antimicrobial functions of the phagocytic cells of the immune system. The catalytic core of this oxidase consists of a complex between gp91 ^phox , p22 ^phox , p47 ^phox , p67 ^phox , p40 ^phox , and rac-2. Mutations in each of the phox components, except p40 ^phox , have been described in cases of chronic granulomatous disease (CGD), defining their essential role in oxidase function. We sought to establish the role of p40 ^phox by investigating the NADPH oxidase responses of neutrophils isolated from p40 ^phox−/− mice. In the absence of p40 ^phox , the expression of p67 ^phox is reduced by ∼55% and oxidase responses to tumor necrosis factor α/fibrinogen, immunoglobulin G latex beads, Staphylococcus aureus, formyl-methionyl-leucyl-phenylalanine, and zymosan were reduced by ∼97, 85, 84, 75, and 30%, respectively. The defect in ROS production by p40 ^phox−/− neutrophils in response to S. aureus translated into a severe, CGD-like defect in the killing of this organism both in vitro and in vivo, defining p40 ^phox as an essential component in bacterial killing.