Response of sheep after localized deposition of lipopolysaccharide in the lung.

Deposition by fiberoptic bronchoscopy of lipopolysaccharide (LPS) from Pasteurella haemolytica (Type 1A) or Escherichia coli (Type 026:B6) into the lungs of sheep elicited a variety of clinical and pathologic reactions. Sheep given P. haemolytica LPS developed a biphasic hematologic response: a marked decline in leukocyte counts in 4 h that was followed in 18 h by a mild leukocytosis. A gradual rise in leukocyte counts was seen in sheep given E. coli LPS. Neutrophil counts gradually increased after deposition with either LPS, but lymphocyte counts fluctuated with the total leukocyte counts. Body temperature remained normal after LPS deposition. A marked increase in total lung lavage cell counts was observed 22 h after LPS deposition. Up to 83% of the lavage cells were neutrophils. Both LPS induced diffuse fibrinopurulent inflammation, edema, hyperemia, and hemorrhage in the lungs. LPS from P. haemolytica also caused foci of necrosis. In contrast, distilled water caused diffuse edema and hyperemia, with a limited number of neutrophils. Deposition of P. haemolytica or E. coli LPS into the lungs of sheep resulted in lesions similar to those reported in animals with an acute pneumonia experimentally induced with gram-negative bacteria.