The mechanism of the production of superoxide by phagocytes.

Superoxide is produced by phagocytic cells at rates sufficient to have cytocidal effects. A wide variety of receptor-dependent and -independent agonists triggers this respiratory burst, including immunoglobin aggregates, complement fragments, and leukotriene B4. Lower rates of O2-. production are triggered by addition of specific cytokines into B-lymphocytes, endothelial cells, fibroblasts, and kidney mesangial cells; low concentration of radicals may act as signals for proliferation or other changes. The NADPH oxidase of phagocytes, characterized by the presence of FAD and a low potential cytochrome b, is organized to transfer electrons electrogenically across the plasma membrane from NADPH to O2. A proton channel permits movement of compensating H+.