Surfactant protein D expression in normal and pneumonic ovine lung

Branka Grubor, Jack M. Gallup, Rafael Ramírez-Romero, Ted B. Bailey, Erika C. Crouch, Kim A. Brogden, Mark R. Ackermann

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

Surfactant protein D (SP-D) is a collagenous calcium-dependent lectin constitutively expressed by alveolar type II pneumocytes and non-ciliated bronchiolar epithelial (Clara) cells. It binds to surface glycoconjugates expressed by a wide variety of microorganisms such as Gram-negative bacteria, influenza A virus, and various fungi, leading to pathogen inactivation or enhanced neutrophil and macrophage activity. Since a hallmark of bronchopneumonia is the initiation of inflammation in the bronchi and bronchoalveolar junction, we chose a classic ruminant model of bronchopneumonia caused by Mannheimia haemolytica to study the expression of SP-D within the bronchioles of infected lambs. Healthy weaned lambs were inoculated with either pyrogen-free saline (controls) or M. haemolytica intrabronchially using a fiber-optic bronchoscope. SP-D protein and mRNA expression in lung was detected by immunohistochemistry (IHC) and fluorogenic real-time relative quantitative reverse transcriptase polymerase chain reaction (real-time RT-PCR), respectively, during acute (1 day), subacute (15 days), and chronic (45 days) bronchopneumonia. At 15 and 45 days post-inoculation, areas of lung had peribronchiolar inflammatory cell infiltrate, epithelial cell hyperplasia, tortuosity of the airway lumens, and decreased intensity of SP-D protein staining and number of positive cells. The levels of SP-D mRNA were not increased or significantly altered by M. haemolytica infection when compared to control animals. In conclusion, cell-associated SP-D protein expression significantly decreases within hyperplastic epithelium of lungs from infected animals during chronic bronchopneumonia. Exhaustion of SP-D protein reserves and absence of SP-D gene upregulation during the progression of bacterial pneumonia into chronicity may result in failure to clear the pathogen from the lung and/or cause animals to be more susceptible to re-infection.

Original languageEnglish
Pages (from-to)235-242
Number of pages8
JournalVeterinary Immunology and Immunopathology
Volume101
Issue number3-4
DOIs
StatePublished - Oct 2004

Keywords

  • LKT
  • M. haemolytica
  • Mannheimia haemolytica
  • NGS
  • PVDF
  • Real-time RT-PCR
  • SP-D
  • Saline
  • fluorogenic real-time relative quantitative reverse transcriptase PCR
  • leukotoxin
  • p.i.
  • polyvinylidine difluoride
  • post-inoculation
  • pyrogen-free saline
  • surfactant protein D

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