title: Effects of Pasteurella haemolytica A1 leukotoxin on bovine neutrophils: degranulation and generation of oxygen-derived free radicals.
abstract: To further define the role of Pasteurella haemolytica A1 leukotoxin in the pathogenesis of bovine pneumonic pasteurellosis, its in vitro effects on bovine neutrophils were investigated. Leukotoxin-containing culture supernatant, from P. haemolytica, stimulated a neutrophil respiratory burst as measured by the generation of oxygen-derived free radicals O2- and H2O2. This effect was immediate because preincubation of neutrophils with the culture supernatant for 5 min or longer substantially suppressed this respiratory burst. This suppression was due to cytolysis of the neutrophils. Prolonged incubation of neutrophils with the same culture supernatant caused further cytolysis and degranulation. Heat-inactivated P. haemolytica culture supernatant that had lost its cytotoxic properties failed to stimulate respiratory burst by neutrophils. Furthermore, the respiratory burst, cytolysis and degranulation were abrogated only by leukotoxin-neutralizing monoclonal and polyclonal antibodies, but not by antibodies against the lipopolysaccharide. These studies show that the leukotoxin component in the culture supernatant was responsible for the generation of oxygen-derived free radicals and proteolytic enzymes from neutrophils which may participate in direct lung injury.
authors.affiliation: Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Minnesota, St. Paul 55108.
authors.forename: S K
authors.initials: SK
authors.lastname: Maheswaran
authors.forename: D J
authors.initials: DJ
authors.lastname: Weiss
authors.forename: M S
authors.initials: MS
authors.lastname: Kannan
authors.forename: E L
authors.initials: EL
authors.lastname: Townsend
authors.forename: K R
authors.initials: KR
authors.lastname: Reddy
authors.forename: L O
authors.initials: LO
authors.lastname: Whiteley
authors.forename: S
authors.initials: S
authors.lastname: Srikumaran
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000494:pharmacology; D002417:Cattle; D015550:Cell Degranulation / Q000187:drug effects; D005098:Exotoxins / Q000494:pharmacology*; D005609:Free Radicals; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D016978:Mannheimia haemolytica / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D016897:Respiratory Burst / Q000276:immunology; D013481:Superoxides / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D001427:Bacterial Toxins; D005098:Exotoxins; D005609:Free Radicals; D007166:Immunosuppressive Agents; C018579:leukotoxin; D013481:Superoxides; D006861:Hydrogen Peroxide; D013755:Tetradecanoylphorbol Acetate