The Role of Peroxidase in the Bactericidal Activity of Human Blood Eosinophils

Utilizing cell preparations that contained greater than 90% eosinophils and sodium azide to inhibit the lysosomal enzyme peroxidase, studies of eosinophil bactericidal activity were undertaken. Eosinophils did not kill bacteria as well as neutrophils, principally because of a reduced phagocytic capacity. In contrast to neutrophils, eosinophils had high resting iodination activity but failed to increase this activity following phagocytosis. One millimolar sodium azide, which inhibits both eosinophil and neutrophil peroxidase as measured by the iodination of trichloroacetic acid precipitable protein, impaired neutrophil staphylocidal activity, but enhanced eosinophil killing of Staphylococcus aureus primarily by increasing phagocytic uptake. Bactericidal studies utilizing lysostaphin suggest that neutrophil peroxidase exerts its contribution to bactericidal activity only during the early postphagocytic period. Eosinophil peroxidase is genetically and biochemically distinct from neutrophil peroxidase, and appears to play no role in the bactericidal activity of intact eosinophils.