Cytochemistry of NADPH oxidase activity in human neutrophils

Human neutrophils respond with a potent and sustained production of superox ide by NADPH oxidase activity after exposure to various stimulants. Superox ide is then converted to other reactive oxygen species. These oxidants part icipate in microbial killing, cause injury to surrounding tissues, regulate apoptosis of neutrophils, and, further, are viewed as a signal transductio n messenger. We present herein the cytochemical approach for detecting NADP H oxidase activity in human neutrophils under both an electron microscope a nd a CCD camera-equipped fluorescence microscope. The applications of the c ytochemical methodology are also mentioned in this review. Especially, the following mechanisms for the release of superoxide from human neutrophils a re considered: the active NADPH oxidase is located exclusively in intracell ular compartments which are delivered to the plasma membrane by membrane fu sion events, and the vesicles whose membrane contain the active oxidase cyc le between the interior of the cell and the plasma membrane.