Superoxide generation by human monocytes and macrophages

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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.