title: Indoleamine 2,3-dioxygenase expression in patients with allergic rhinitis: a case-control study.
abstract: BACKGROUND
  Indoleamine 2,3-dioxygenase (IDO) is a tryptophan catalyzing enzyme. It has been suggested that it has a role in lower airway allergic inflammations, but its role in allergic rhinitis has not been investigated.
  
  
  OBJECTIVE
  Our aim was to evaluate the expression of IDO in the nasal mucosa of allergic rhinitis patients allergic to birch pollen during peak exposure to birch pollen allergen and compare it to non-atopic patients.
  
  
  METHODS
  IDO expression was immunohistochemically evaluated from nasal specimens obtained in- and off-season from otherwise healthy non-smoking volunteers both allergic to birch pollen (having mild or moderate allergic rhinoconjunctivitis) and non-allergic controls.
  
  
  RESULTS
  The IDO expression levels were low in healthy controls and remained low also in patients allergic to birch pollen. There were no differences in the expression of IDO in- and off-season in either healthy or allergic subjects.
  
  
  CONCLUSIONS
  There is a controversy in the role of IDO in upper and lower airways during allergic airway disease. It seems that IDO is associated to allergic inflammations of the lower airways, but does not have a local role in the nasal cavity at least in mild or moderate forms of allergic rhinitis.
authors.affiliation: Helsinki University Hospital, Skin and Allergy Hospital, Helsinki, Finland. Sanna.salmi@helsinki.fi.
authors.forename: Annika
authors.initials: A
authors.lastname: Luukkainen
authors.forename: Jussi
authors.initials: J
authors.lastname: Karjalainen
authors.forename: Teemu
authors.initials: T
authors.lastname: Honkanen
authors.forename: Mikko
authors.initials: M
authors.lastname: Lehtonen
authors.forename: Timo
authors.initials: T
authors.lastname: Paavonen
authors.forename: Sanna
authors.initials: S
authors.lastname: Toppila-Salmi