Avian heterophils and monocytes: phagocytic and bactericidal activities against Salmonella enteritidis

The ability of heterophils and monocytes from domestic chickens and turkeys to phagocytize and kill Salmonella enteritidis (SE) was investigated using both a standard plate count (chickens only) and direct microscopic examination by staining with acridine orange (both chickens and turkeys). Optimal phagocytosis of SE by both chicken and turkey phagocytes required opsonization of the bacteria by antibodies as determined by both assays. However, heterophils from both the turkeys and chickens phagocytized more SE than did monocytes from either type of fowl. Regardless of the presence or absence of antibodies, heterophils were more efficient bactericidal cells than were the monocytes since only heterophils killed the intracellular bacteria while the majority of nonopsonized SE survived in the monocytes. Phagocytosis of SE did not result in an increase in the amount of superoxide anion released by the heterophils suggesting that the ultimate fate of the bacteria in these cells was not related to an oxygen-dependent mechanism.