Cytokine profiles following interaction between bovine alveolar macrophages and Pasteurella haemolytica

Pasteurella haemolytica is a Gram negative bacterium frequently isolated fr om the lungs of calves suffering from a fibrinous pneumonic condition known as shipping fever. To understand the pathogenesis of this disease, we inve stigated the induction of cytokin gene expression in cultures of bovine alv eolar macrophages (BAM) stimulated with heat-killed Fl haemolytica. Norther n blot analysis of total RNA showed that P. haemolytica induced early, abun dant, and consistent synthesis of IL-1, TNF-alpha, and IL-8 mRNA. Cytokine mRNAs were detected within 1 hr post-stimulation with heat-killed P. haemol ytica. IL-1 and IL-8 mRNA accumulated to high levels with increase in stimu lation time, whereas TNF-alpha mRNA clearly declined by 4 and 8 h post stim ulation. IL-1,TNF-alpha, and IL-8 proteins were also secreted into the cult ure medium of BAM stimulated with heat-killed P. haemolytica. All three pro teins were detected at high levels 8 and 12 h post stimulation with P. haem olytica. BAM cells treated with bovine interferon-alpha and then stimulated with Fl haemolytica produced higher amounts of IL-1, IL-8 and TNF-alpha pr oteins compared to BAM stimulated with P. haemolytica alone. These findings demonstrate the powerful and selective induction of cytokine mRNA and prot ein synthesis in BAM stimulated with heat-killed P. haemolytica and may exp lain certain aspects of shipping fever pathogenesis. (C) 1999 Academic Pres s.