Increased tumor necrosis factor-α and interleukin-1β expression in the lungs of calves with experimental pneumonic pasteurellosis

We used a well characterized pneumonic pasteurellosis model in calves to determine whether increased proinflammatory cytokines, tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) expression and secretion were associated with pneumonic lesions. Bronchoalveolar lavage fluids, lavage cells consisting of alveolar macrophages and neutrophils with degenerative changes, and lung tissues were analyzed for the presence of TNF-α and IL-1β approximately 48 h following endobronchial inoculation of logarithmic phase Pasteurella haemolytica 12296 organisms. Levels of TNF-α and IL-1β mRNA were significantly increased in lavage cells of P. haemolytica-infected animals but not in cells from phosphate buffered saline (PBS) inoculated controls based on in situ hybridization analysis. Significantly increased levels of TNF-α, and IL-1β mRNA were also expressed within the pneumonic lesions from P. haemolytica-infected calves. In contrast, lung tissues from PBS-inoculated control calves had cytokine mRNAs expressed at extremely low levels. Increased levels of bioactive IL-1 and immunoreactive (not bioactive) TNF-α were found in lavage fluids from P. haemolytica-infected calves compared with lavage fluids from PBS-inoculated calves. These findings indicate that the proinflammatory cytokines TNF-α and IL-1, may be associated with pathogenesis of lung injury in bovine pneumonic pasteurellosis.