Role of the Phagocyte in Host-Parasite Interactions XI. Relationship Between Stimulated Oxidative Metabolism and Hydrogen Peroxide Formation, and Intracellular Killing

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Abstract
Increased respiratory and hexose monophosphate activities noted in phagocytizing cells results in the formation of H2O2. This is brought about by the oxidation of reduced NADP by its oxidase. Evidence is presented which indicates that this H2O2 is involved in the intracellular killing of bacteria. When molecular O2 was excluded from phagocytizing leukocytes by anaero-biosis thus inhibiting H2O2 formation, reduced intracellular killing was observed. In some cases the impairment of leukocytic bactericidal activity by anaerobiosis could be partially reversed by the addition of H2O2. Exogenous catalase also could reduce intracellular killing. In addition, when leukocytic isolates were dialyzed so as to reduce endogenous H2O2, the bactericidal activity of the leukocytes was significantly decreased under both aerobic and anaerobic conditions. These results occurred with both guinea pig and human leukocytes and with several test microorganisms.