Study of bovine pulmonary response to Pasteurella haemolytica: pulmonary macrophage response.

A resistance state was produced in the bovine lung by exposing calves to an aerosolized mist of Pasteurella haemolytica. Verification of the resistant state was determined by an increase in clearance of P haemolytica from lungs of exposed calves vs lungs from nonexposed calves over 24 hours. Bovine pulmonary macrophages isolated from lung washings of calves exposed to P haemolytica and from lungs of nonexposed calves failed to phagocytize P haemolytica in vitro. Whole serum, pulmonary immunoglobulin (Ig) A, and IgG from exposed and nonexposed calves did not enhance phagocytosis as measured by 14C uptake or fluorescent antibody staining.