title: Allergen inhalation challenge in smoking compared with non-smoking asthmatic subjects.
abstract: BACKGROUND
  Smoking asthmatics experience more severe symptoms, require more rescue medication and have more asthma-related hospitalizations than non-smoking asthmatics. However, studies in mice suggest that mainstream cigarette smoke may reduce airway inflammation and may attenuate airway hyperresponsiveness. A comparison of allergen-induced airway inflammatory responses of smoking and non-smoking atopic asthmatics has not been examined previously.
  
  
  OBJECTIVE
  To determine whether allergen-induced airway responses and inflammatory profiles are attenuated in smoking when compared with non-smoking mild allergic asthmatic subjects.
  
  
  METHODS
  Allergen inhalation challenges were performed in 13 smoking and 19 non-smoking mild allergic asthmatic subjects. The forced expired volume in 1 s (FEV(1) ) was measured up to 7 h after allergen inhalation. Methacholine airway responsiveness was measured before and at 24 h after allergen and sputum was induced before and at 7 and 24 h after allergen.
  
  
  RESULTS
  Both the smoking and non-smoking groups developed similar allergen-induced falls in FEV(1) during the early and late asthmatic responses and similar increases in allergen-induced airway eosinophils. The mean maximum fall in FEV(1) during the late response was 16.3 ± 4.3% in non-smokers and 12.9 ± 7.2% in smokers. The smoking asthmatics, however, did not develop allergen-induced methacholine airway hyperresponsiveness, whereas the non-smoking controls developed a 1.18 doubling dose shift in methacholine PC(20) (P < 0.05).
  
  
  CONCLUSIONS
  Mild allergic asthmatic subjects, who were current smokers with a mean 6-year pack history, develop allergen-induced eosinophilic airway inflammation and late responses, similar in magnitude to non-smoking asthmatics, but do not develop methacholine airway hyperresponsiveness associated with the allergen-induced airway eosinophilia.
authors.affiliation: Firestone Institute for Respiratory Health, St. Joseph's Hospital and Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Z
authors.initials: Z
authors.lastname: Meghji
authors.forename: B
authors.initials: B
authors.lastname: Dua
authors.forename: R M
authors.initials: RM
authors.lastname: Watson
authors.forename: G M
authors.initials: GM
authors.lastname: Gauvreau
authors.forename: P M
authors.initials: PM
authors.lastname: O'Byrne
mesh_terms: D000280:Administration, Inhalation; D000293:Adolescent; D000328:Adult; D000485:Allergens / Q000008:administration & dosage / Q000009:adverse effects*; D001249:Asthma / Q000276:immunology / Q000473:pathology*; D003367:Cotinine / Q000652:urine; D006801:Humans; D016210:Methacholine Chloride / Q000008:administration & dosage / Q000009:adverse effects*; D008875:Middle Aged; D012907:Smoking; D013183:Sputum / Q000166:cytology / Q000276:immunology; D055815:Young Adult
chemical_list: D000485:Allergens; D016210:Methacholine Chloride; D003367:Cotinine