EXOGENOUS MYELOPEROXIDASE ENHANCES BACTERIAL PHAGOCYTOSIS AND INTRACELLULAR KILLING BY MACROPHAGES

It is well documented that myeloperoxidase (MyPo) contributes to the b actericidal activities of neutrophils and monocytes. Since mature macr ophages (M phi) are devoid of this enzyme, its participation in M phi- mediated phagocytosis acid bacterial killing has not been completely d efined. The present study demonstrates that exogenously added MyPo, at physiological levels, enhances both phagocytosis and killing of Esche richia coil. Murine peritoneal M phi were exposed to various concentra tions of MyPo for different time intervals. Viable opsonized E. coli w as added either prior to or after addition of MyPo. Thioglycolate-indu ced but not resident M phi exhibited an increase in the number of phag ocytizing cells. Both resident and thioglycolate-induced M phi demonst rated increased bactericidal activity, Physiological levels of soluble MyPo also induced a significant increase in chemiluminescence. Since luminol dependent chemiluminescence measures reactive oxygen intermedi ate production, studies were done to determine whether superoxide anio n or H2O2 was involved in MyPo-iuduced M phi killing. Both superoxide dismutase and catalase ablated MyPo-induced bactericidal activity. The above data suggest that soluble MyPo, released from neutrophils at a site of infection or inflammation, can enhance both phagocytosis and k illing of microorganisms.