Cytotoxic effect of Pasteurella haemolytica on bovine polymorphonuclear leukocytes and impaired production of chemotactic factors by Pasteurella haemolytica-infected alveolar macrophages

Pasteurella haemolytica exerted a cytotoxic effect on bovine polymorphonuclear neutrophil leukocytes. This effect was less than that seen with cultured alveolar macrophages or peripheral blood monocytes. When alveolar macrophages were cultured with Pasteurella haemolytica, macrophages produced less chemotactic factors for polymorphonuclear leukocytes than did noninfected controls. This effect was reversible, in that removal of the bacteria permitted remaining macrophages to elaborate more chemotactic factors than was seen in controls. The possible consequences of this impairment of function of alveolar macrophages are discussed.