Role of the Phagocyte in Host-Parasite Interactions XII. Hydrogen Peroxide-Myeloperoxidase Bactericidal System in the Phagocyte

Abstract

An antimicrobial system in polymorphonuclear neutrophils (PMN) consisting of myeloperoxidase and hydrogen peroxide has been proposed. This system appears to be activated during phagocytosis as a result of the stimulated metabolic activities. A lysed-granules (LG) fraction was prepared from guinea pig exudative PMN. LG alone possessed bactericidal activity which was related to the p H of the reaction; the lower the p H, the more marked the activity. When low concentrations of both H 2 O 2 and LG were combined under conditions where neither factor alone exhibited significant killing power, there was a striking increase in bactericidal activity. This enhanced activity was much greater than an additive effect. The LG-peroxide antibacterial system was most active over a p H range of 4.0 to 6.0. The activity of the LG-peroxide system was essentially abolished by peroxidase inhibitors, NaN 3 , KCN, and aminotriazole. The antibacterial activity of this system was nonspecific in nature, being equally effective against gram-negative and gram-positive organisms.