title: Ingestion and killing of Pasteurella haemolytica A1 by bovine neutrophils in vitro.
abstract: In this study, various parameters affecting the ability of bovine neutrophils to ingest and kill a virulent strain of Pasteurella haemolytica A1 in vitro were examined. Ingestion of P. haemolytica was serum dependent (optimal serum concentration 10%) and was mediated principally by heat-stable opsonins, presumably antibodies, that could be removed by absorption with formalin-killed P. haemolytica. Ingested P. haemolytica were killed by neutrophils within 1-4 h incubation; the magnitude of killing being directly dependent on the number of neutrophils present. The number of viable P. haemolytica was reduced by approximately 1.5 log at bacterial concentrations of 0.01-100 P. haemolytica per neutrophil; a concomitant reduction in neutrophil viability was observed at the highest bacterial concentration (100:1). Bovine neutrophils underwent a vigorous luminol-enhanced chemiluminescence response after ingesting opsonized P. haemolytica, thus indicating that reactive oxygen intermediates were being formed that could have contributed to the intracellular killing of P. haemolytica.
mesh_terms: D000818:Animals; D002417:Cattle / Q000097:blood / Q000276:immunology*; D002470:Cell Survival; D008163:Luminescent Measurements; D008854:Microscopy, Electron; D009504:Neutrophils / Q000276:immunology* / Q000382:microbiology / Q000502:physiology / Q000648:ultrastructure; D010325:Pasteurella / Q000276:immunology* / Q000648:ultrastructure; D010587:Phagocytosis