Respiratory Burst

  • Involves the activation of the phagocyte NADPH oxidase complex (eg, in neutrophils, monocytes), which utilizes O2 as a substrate.
  • O2 (+ NADPH oxidase via oxidative burst) → superoxide (+ superoxide dismutase) → hydrogen peroxide (+myeloperoxidase) → HClO
  • H2O2 oxidizes glutathione (from reduced GSH to GSSG)
  • Plays an important role in the immune response → rapid release of reactive oxygen species (ROS).
  • NADPH plays a role in both the creation and neutralization of ROS.
  • Myeloperoxidase contains a blue-green heme-containing pigment that gives sputum its color.
  • Phagocytes of patients with CGD lack NADPH oxidase, but can utilize H2O2 generated by invading organisms (except catalase positive organisms) and convert it to ROS.
  • Pyocyanin of P aeruginosa generates ROS to kill competing pathogens.
  • Oxidative burst also leads to K+ influx, which releases lysosomal enzymes from proteoglycans.
  • Lactoferrin is a protein found in secretory fluids and neutrophils that inhibits microbial growth via iron chelation.
  • Myeloperoxidase deficiency – usually asymptomatic, increased risk for candidiasis
    • Nitroblue tetrazolium test is normal

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