Superoxide generation by human monocytes and macrophages

Abstract

Intracellular and extracellular superoxide (O₂ ^.−) generation by human monocytes and macrophages was quantitated by the nitroblue tetrazolium (NBT) reduction method. Human monocytes reduced 4.4 ± 0.9 nmoles/10⁶ cells/15 minutes with an increase to 12.4 ± 1.3 during phagocytosis of zymosan. Based on inhibition by superoxide dismutase, superoxide generation of these cells was 1.8 ± 0.3 nmoles in the resting state and 16.8 ± 2.8 nmoles with zymosan phagocytosis. Human macrophages obtained by thoracentesis had comparable levels of NBT reduction and O₂ ^.− generation. Monocytes from a patient with chronic granulomatous disease demonstrated no increment in O₂ ^.− production during phagocytosis. Thus, human monocytes and macrophages appear capable of generating substantial amounts of O₂ ^.− during phagocytosis which may play an important role in bactericidal and other cell functions.