Role of the phagocyte in host-parasite interactions. XI. Relationship between stimulated oxidative metabolism and hydrogen peroxide formation, and intracellular killing.

The increased respiratory and hexose monophosphate activities noted in phagocytizing cells results in the formation of hydrogen peroxide. This is brought about by the oxidation of reduced nicotinamide adenine dinucleotide phosphate by its oxidase. Evidence is presented which indicates that this H(2)O(2) is involved in the intracellular killing of bacteria. When molecular oxygen was excluded from phagocytizing leukocytes by anaerobiosis, thus inhibiting H(2)O(2) 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 H(2)O(2). Exogenous catalase also could reduce intracellular killing. In addition, when leukocytic isolates were dialyzed so as to reduce endogenous H(2)O(2), 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.