What is a respiratory burst, also known as an oxidative burst?

From the Guidelines

Respiratory burst, also known as an oxidative burst, is a rapid release of reactive oxygen species (ROS) by immune cells, primarily neutrophils and macrophages, when they encounter pathogens, playing a crucial role in the body's defense mechanism against infections. This process involves the production of powerful oxidizing agents like superoxide, hydrogen peroxide, and hypochlorous acid, which directly attack and kill invading microorganisms by damaging their cell membranes, proteins, and DNA 1. The importance of oxidative stress and the generation of oxidative compounds in normal physiology is highlighted in the context of inflammation and tissue repair processes, as well as defense mechanisms against invading micro-organisms and malignant cells 1. Key aspects of the respiratory burst include:

• The recognition of pathogens through receptors on the surface of immune cells or during phagocytosis
• The assembly of the NADPH oxidase enzyme complex on the cell membrane upon activation
• The dramatic increase in oxygen consumption by immune cells, which is then converted into ROS
• The potential for defects in respiratory burst capability, such as in chronic granulomatous disease, to lead to recurrent severe infections due to the immune cells' inability to effectively kill certain pathogens. Overall, the respiratory burst is a vital component of the body's immune response, and its dysfunction can have significant implications for morbidity, mortality, and quality of life.

From the Research

Definition of Respiratory Burst

• The respiratory burst, also known as an oxidative burst, is a rapid cellular consumption of oxygen resulting in abundant production of reactive oxygen species (ROS) 2.
• It is most often associated with primary mediators of innate immunity, such as neutrophils and macrophages, which convert ROS into potent antimicrobial oxidants that efficiently kill pathogens 2, 3.

Mechanism of Respiratory Burst

• The respiratory burst is generated by an NADPH oxidase multi-protein complex that has a catalytic core consisting of membrane-bound gp91phox (CYBB) and p22phox (CYBA) sub-units and cytosolic components p47phox (NCF1), p67phox (NCF2), and p40phox (NCF4) 3.
• The process involves the production of large amounts of superoxide and hydrogen peroxide, as well as the metabolism of large quantities of glucose through the hexose monophosphate shunt 3.

Role of Respiratory Burst in Host Defense and Inflammation

• The respiratory burst plays an essential role in host defense against pathogens, with neutrophils and macrophages using ROS to kill internalized bacteria 4, 5.
• However, excessive neutrophil priming can lead to detrimental effects in inflammatory diseases, highlighting the importance of controlled neutrophil priming in host defense 4.
• The respiratory burst can also have destructive consequences, as ROS can support chronic inflammation and aberrant autoimmune responses 2.

Measurement of Respiratory Burst

• Various analytical methods are available to measure oxygen-dependent mechanisms of respiratory burst in phagocytes, including luminol/isoluminol amplified chemiluminescence, cytochrome C reduction, and PHPA oxidation technique 6.
• These techniques are valuable tools in basic and clinically oriented research dealing with phagocyte function 6.