The generation of reactive oxygen-derived species by phagocytes

The generation of reactive oxygen-derived species is one main constituent of the microbicidal activity of professional phagocytes. This process is known as the respiratory or the oxidative burst. It is initiated by a cyanide- and azide-insensitive increase in O2-consumption and the concomitant generation of superoxide radicals catalyzed by a membrane-localized NADPH oxidase which is triggered by an appropriate stimulation of the cells. The generated O2 is converted to hydrogen peroxide, hydroxyl radicals and other reactive products of oxygen which, if released extracellularly (for example in connection with frustrated phagocytosis), are potentially harmful to the tissue. The oxidative burst is not necessarily dependent on phagocytosis, nor is it necessarily associated with degranulation. Therefore, the process constitutes an important independent variable of phagocyte activity, and researches aiming to characterize various forms of airway inflammation may derive valuable information from an examination of the oxidative burst.