Neutrophils - Oxidative Burst

Summary

The Neutrophil Oxidative Burst (Respiratory Burst) produces reactive oxygen species capable of killing pathogens. The three reactive oxygen species produced are superoxide, hydrogen peroxide, and hypochlorous acid (bleach).

First, NADPH Oxidase converts oxygen to superoxide. NADPH Oxidase is deficient in chronic granulomatous disease, an immunodeficiency characterized by a failure to produce reactive oxygen species.

Superoxide may be used to directly kill pathogens, or it may be converted into Hydrogen Peroxide, in a reaction catalyzed by superoxide dismutase (SOD).

Hydrogen Peroxide is also toxic to pathogens, although catalase-positive bacteria use catalase to degrade Hydrogen Peroxide into oxygen and water.

Lastly, Myeloperoxidase or MPO catalyzes the conversion of hydrogen peroxide into hypochlorous acid, commonly known as bleach. Bleach is also toxic to pathogens.

Altogether, these compounds are used by neutrophils to kill invading pathogens, protecting the body from infection.

Key Points

• Neutrophil Oxidative Burst (Respiratory Burst)
  • Produces reactive oxygen species (ROS)
    • Superoxide
    • Hydrogen peroxide
    • Hypochlorite (bleach)
  • Oxygen (O2) → superoxide by NADPH Oxidase
    • NADPH Oxidase is contained in Neutrophil Granules
    • Chronic Granulomatous Disease (CGD) is an immunodeficiency resulting from a deficiency of NADPH oxidase
  • Superoxide → hydrogen peroxide by Superoxide Dismutase (SOD)
    • Hydrogen peroxide is degraded by catalase in some bacteria
    • SOD defects are associated with ALS due to poorly understood reasons
  • Hydrogen Peroxide → Bleach, by Myeloperoxidase (MPO)
    • MPO is contained in Neutrophil Granules