title: PR-39, a porcine host defence peptide, is prominent in mucosa and lymphatic tissue of the respiratory tract in healthy pigs and pigs infected with Actinobacillus pleuropneumoniae.
abstract: BACKGROUND
  Host defence peptides are important components of mammalian innate immunity. We have previously shown that PR-39, a cathelicidin host defence peptide, is an important factor in porcine innate immune mechanisms as a first line of defence after infection with Actinobacillus pleuropneumoniae. PR-39 interacts with bacterial and mammalian cells and is involved in a variety of processes such as killing of bacteria and promotion of wound repair. In bronchoalveolar lavage fluid of infected pigs PR-39 concentrations are elevated during the chronic but not during the acute stage of infection when polymorphonuclear neutrophils (known as the major source of PR-39) are highly increased. Thus it was assumed, that the real impact of PR-39 during infection might not be reflected by its concentration in bronchoalveolar lavage fluid.
  
  
  RESULTS
  Using immunohistochemistry this study demonstrates the actual distribution of PR-39 in tissue of the upper and lower respiratory tract of healthy pigs, and of pigs during the acute and chronic stage of experimental infection with Actinobacillus pleuropneumoniae.During the acute stage of infection PR-39 accumulated adjacent to blood vessels and within bronchi. Immune reactions were mainly localized in the cytoplasm of cells with morphological characteristics of polymorphonuclear neutrophils as well as in extracellular fluids. During the chronic stage of infection pigs lacked clinical signs and lung alterations were characterized by reparation and remodelling processes such as tissue sequestration and fibroblastic pleuritis with a high-grade accumulation of small PR-39-positive cells resembling polymorphonuclear neutrophils. In healthy pigs, PR-39 was homogenously expressed in large single cells within the alveoli resembling alveolar macrophages or type 2 pneumocytes. PR-39 was found in all tissue samples of the upper respiratory tract in healthy and diseased pigs. Within the tracheobronchial lymph nodes, PR-39 dominated in the cytoplasm and nuclei of large cells resembling antigen-presenting cells located in the periphery of secondary follicles.
  
  
  CONCLUSIONS
  These immunohistochemical findings indicate that, in addition to polymorphonuclear neutrophils, other cells are involved in the expression, storage, or uptake of PR-39. The presence of PR-39 in healthy lung tissue showed that this antibacterial peptide might be important for the maintenance of health.
authors.affiliation: Clinic for Swine, University of Veterinary Medicine, Vienna, Austria. isabel.hennig@tiho-hannover.de
authors.forename: Isabel
authors.initials: I
authors.lastname: Hennig-Pauka
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Koch
authors.forename: Doris
authors.initials: D
authors.lastname: Hoeltig
authors.forename: Gerald-F
authors.initials: GF
authors.lastname: Gerlach
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Waldmann
authors.forename: Frank
authors.initials: F
authors.lastname: Blecha
authors.forename: Carsten
authors.initials: C
authors.lastname: Brauer
authors.forename: Hagen
authors.initials: H
authors.lastname: Gasse
mesh_terms: D000189:Actinobacillus Infections / Q000276:immunology* / Q000382:microbiology / Q000473:pathology / Q000662:veterinary*; D016977:Actinobacillus pleuropneumoniae / Q000276:immunology; D000208:Acute Disease; D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology / Q000473:pathology; D023181:Antimicrobial Cationic Peptides / Q000096:biosynthesis / Q000276:immunology*; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry / Q000166:cytology; D002908:Chronic Disease; D005260:Female; D054884:Host-Pathogen Interactions; D007113:Immunity, Innate; D007150:Immunohistochemistry; D008168:Lung / Q000276:immunology / Q000473:pathology; D008198:Lymph Nodes / Q000276:immunology* / Q000473:pathology; D016676:Macrophages, Alveolar / Q000276:immunology / Q000473:pathology; D008297:Male; D009504:Neutrophils / Q000276:immunology / Q000473:pathology; D020545:Respiratory Mucosa / Q000276:immunology* / Q000473:pathology; D013552:Swine; D013553:Swine Diseases / Q000276:immunology* / Q000382:microbiology / Q000473:pathology; D014132:Trachea / Q000276:immunology / Q000473:pathology
chemical_list: D023181:Antimicrobial Cationic Peptides; C072212:PR 39