title: Appearance of allergen-induced increases in airway responsiveness only after repeated allergen inhalations in two subjects.
abstract: Observations in two subjects undergoing three allergen challenges for a drug study suggested 'priming' of the late sequelae, namely allergen-induced increase in airway responsiveness. Both subjects had rhinitis and asthma limited to the ragweed season, near normal out-of-season histamine PC20, and extreme IgE sensitivity to ragweed. Both had an isolated early response with no change in histamine PC20 after the first allergen challenge. Significant (3.5- to 5.8-fold) reductions in histamine PC20 occurred after the second and third allergen challenge in Subject 1, and after the third challenge in Subject 2; this was associated with equivocal 5-8% late responses. Such a 'priming' effect, the prevalence of which is not known, may be important in the pathogenesis of naturally occurring allergic asthma, and in the design of clinical trials involving repeated allergen inhalations.
authors.affiliation: Department of Medicine, University Hospital, Saskatoon, Sasakatchewan, Canada.
authors.forename: D W
authors.initials: DW
authors.lastname: Cockcroft
authors.forename: R E
authors.initials: RE
authors.lastname: Ruffin
authors.forename: F E
authors.initials: FE
authors.lastname: Hargreave
mesh_terms: D000293:Adolescent; D000328:Adult; D000485:Allergens / Q000008:administration & dosage*; D001249:Asthma / Q000276:immunology / Q000503:physiopathology*; D001985:Bronchial Provocation Tests; D005260:Female; D005541:Forced Expiratory Volume; D006632:Histamine / Q000097:blood; D006801:Humans; D006969:Hypersensitivity, Immediate; D009241:Ipratropium / Q000008:administration & dosage; D006255:Rhinitis, Allergic, Seasonal / Q000276:immunology
chemical_list: D000485:Allergens; D006632:Histamine; D009241:Ipratropium