Novel cytochrome b system in phagocytic vacuoles of human granulocytes

Abstract

NEUTROPHIL granulocytes are the most numerous leukocytes and have a primary microbicidal role. They are the first cells to accumulate at sites of inflammation where they engulf, kill and digest microbes. The phagocytic process is accompanied by a burst of oxygen consumption which is important for the killing of certain bacteria, as the ability to kill bacteria is impaired in anaerobic conditions¹; in chronic granulomatous disease (CGD) this enhancement of oxygen consumption is distinctively lacking². The burst of oxygen metabolism is not inhibited by cyanide or azide³, distinguishing it from mitochondrial respiration by these cells which contain few mitochondria and derive most of their energy from glycolysis. The subcellular localisation and mechanism of this oxidase system have been the subject of considerable investigation and controversy. We describe here a cytochrome b system which becomes incorporated into the phagocytic vacuoles of human neutrophils. It is distinct from the cytochrome systems of the endoplasmic reticulum and mitochondria, and abnormalities in patients with CGD implicate it as an essential component of the microbicidal oxidase system.