Repetitive nasal allergen challenge in allergic rhinitis: priming and Th2-type inflammation but no evidence of remodelling.

BACKGROUND: Local tissue eosinophilia and Th2-cytokines are characteristic features of seasonal allergic rhinitis. Airway-remodelling is a feature of asthma whereas evidence for remodelling in allergic rhinitis (AR) is conflicting. OBJECTIVE: By use of a novel human repetitive nasal allergen challenge (RAC) model, we evaluated the relationship between allergic inflammation and features of remodelling in AR. METHODS: Twelve patients with moderate-severe AR underwent 5-alternate day challenges with diluent which after 4-weeks were followed by 5-alternate day challenges with grass pollen extract. Nasal symptoms, Th1/Th2 cytokines in nasal secretion and serum were evaluated. Nasal biopsies were taken 24 hours after the 1st and 5th challenges with diluent and with allergen. Sixteen healthy controls underwent a single challenge with diluent and with allergen. Using immunohistochemistry, epithelial and sub-mucosal inflammatory cells, and remodelling markers were evaluated by computed image analysis. RESULTS: There was an increase in early and late-phase symptoms after every allergen challenge compared to diluent (both p<0.05) with evidence of both clinical and immunological priming. Nasal tissue eosinophils and IL-5 in nasal secretion increased significantly after RAC compared to corresponding diluent challenges (p