title: Antigen-induced airway inflammation and hyper-responsiveness does not enhance airway responses to a subsequent antigen challenge in rats.
abstract: Brown-Norway (BN) rats develop airway hyper-responsiveness and lung eosinophilia 18-24 h after ovalbumin (OA) challenge. We hypothesized therefore that allergen-induced airway inflammation would further enhance airway responses to a subsequent antigen challenge. Animals were sensitized to both OA and bovine serum albumin (BSA) and, 14 days later, challenged by aerosols with both antigens 24 h apart. Measurements of pulmonary resistance (RL) were made for 8 h after the second antigen challenge and bronchoalveolar lavage (BAL) was performed. Animals were divided into three groups and received two challenges as follows: saline-BSA (n=9), OA-saline (n=8) and OA-BSA (n=10). Sensitization was confirmed by measurements of specific OA-IgE and BSA-IgE. Early responses [determined as the highest value of RL within the first 30 min after the challenge] were absent in all study groups. The late responses [determined from the area under the RL versus time curve from 120 to 480 min after the challenge] were significantly greater in animals challenged with BSA (15.16+/-3.86) compared to saline (3.76+/-4.09; P<0.05). However previous exposure to OA did not further increase the late response in animals subsequently challenged with BSA (20.11+/-3.67) despite enhanced airway responsiveness to LTD4 at this time point. BAL eosinophils and lymphocytes were significantly increased following BSA challenge in previously OA-challenged animals, compared to numbers retrieved from animals previously exposed to saline (P<0.05). These data indicate that previous exposure to OA did not further increase the LR to a second antigen challenge despite substantial increases in airway inflammatory cells and airway hyper-responsiveness to LTD4.
authors.affiliation: Meakins-Christie Laboratories, Royal Victoria Hospital, McGill University and the Respiratory Health Network of Centres of Excellence, Montreal, Quebec, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Laberge
authors.forename: P
authors.initials: P
authors.lastname: Rossi
authors.forename: X X
authors.initials: XX
authors.lastname: Yang
authors.forename: J G
authors.initials: JG
authors.lastname: Martin
mesh_terms: D000818:Animals; D000941:Antigens / Q000276:immunology*; D001980:Bronchi / Q000276:immunology*; D001985:Bronchial Provocation Tests; D001991:Bronchitis / Q000276:immunology*; D001992:Bronchoalveolar Lavage Fluid / Q000276:immunology; D007073:Immunoglobulin E / Q000276:immunology; D017998:Leukotriene D4 / Q000276:immunology; D008297:Male; D010047:Ovalbumin / Q000276:immunology*; D051381:Rats; D012709:Serum Albumin / Q000276:immunology*
chemical_list: D000941:Antigens; D012709:Serum Albumin; D007073:Immunoglobulin E; D017998:Leukotriene D4; D010047:Ovalbumin