title: Dominant expression of interleukin-8 vs interleukin-1β and tumour necrosis factor alpha in lungs of lambs experimentally infected with Mannheimia haemolytica.
abstract: OBJECTIVE
  To quantify the number of cells infected with Mannheimia haemolytica and expressing interleukin (IL)-1β, tumour necrosis factor alpha (TNFα) and IL-8 using immunohistochemistry, and to measure the immunoreactivity of cytokines in pulmonary tissue extracts using ELISA, in the lung of lambs experimentally infected with M. haemolytica, and to compare the patterns of expression of cytokines in airways at different times post-infection (p.i.).
  
  
  METHODS
  Twenty 3-month-old lambs of both sexes were randomly assigned to two groups, viz infected (n=15), and uninfected controls (n=5). Each lamb in the infected group was inoculated with 1.5 x 10(9) cfu M. haemolytica in 5 mL sterile nutrient broth, control lambs were inoculated with 5 mL sterile nutrient broth and clinical signs were monitored. Infected and control animals were killed at 1, 3, 5, 7, and 15 days p.i. Histopathology and immunohistochemistry were conducted to determine the number of immunolabelled cells in pneumonic lungs, and study the pattern of expression of IL-1β, TNFα and IL-8 in lung extracts using ELISA.
  
  
  RESULTS
  Lesions in bronchi and bronchioles ranged from epithelial desquamation to bronchiolitis obliterans and necrosis. The alveoli had areas of seroproteinaceous fluid, fibrin and bacterial aggregates that evolved to foci of pyogranulomatous inflammation with clustered inflammatory cells, referred to as 'oat cells'. M. haemolytica antigen was observed in the cytoplasm of inflammatory cells. Labelling of IL-1β, TNFα and IL-8 was observed in bronchial and bronchiolar epithelial cells, alveolar exudate, and in interstitial inflammatory infiltrate, with increased expression on 1 and 3 days p.i. for IL-1β and TNFα, and 1, 3, and 5 days p.i. for IL-8. In lung tissue extracts, peak concentrations of IL-1β (55 (SD 5) ng/mL), TNFα (92 (SD 6) pg/mL) and IL-8 (8 [SD 2] μg/mL) occurred at 3 days p.i.
  
  
  CONCLUSIONS
  The results of this study suggested that the inflammatory cytokines IL-1β, TNFα and IL-8 may play an important role in enhancing the biological response to M. haemolytica, and contribute to the development of lesions in the lung in pulmonary pasteurellosis in sheep. Given that the expression of IL-8 in lung was much greater than that of IL-1β and TNFα, anti-cytokine agents directed at this mediator could be useful in the prevention and treatment of this disease.
authors.affiliation: Department of Histology and Pathology, Veterinary Faculty, University of Extremadura, Avenue of the University, 10003 Cáceres, Spain. eloy@unex.es
authors.forename: E
authors.initials: E
authors.lastname: Redondo
authors.forename: A
authors.initials: A
authors.lastname: Gázquez
authors.forename: A
authors.initials: A
authors.lastname: García
authors.forename: S
authors.initials: S
authors.lastname: Vadillo
authors.forename: A J
authors.initials: AJ
authors.lastname: Masot
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology*; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005260:Female; D007150:Immunohistochemistry / Q000662:veterinary; D053583:Interleukin-1beta / Q000276:immunology; D016209:Interleukin-8 / Q000276:immunology; D008168:Lung / Q000276:immunology* / Q000382:microbiology* / Q000473:pathology; D008297:Male; D016978:Mannheimia haemolytica / Q000276:immunology* / Q000472:pathogenicity; D012756:Sheep; D012757:Sheep Diseases / Q000276:immunology / Q000382:microbiology* / Q000473:pathology; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology
chemical_list: D000942:Antigens, Bacterial; D053583:Interleukin-1beta; D016209:Interleukin-8; D014409:Tumor Necrosis Factor-alpha