Airway inflammation and remodeling can be present in the lower airways of patients with allergic rhinitis, although it is less intense than in patients with asthma. During natural exposure, both the nose and lung come into contact with airborne allergens. Nasal inflammation may influence lower airway inflammatory processes by the release of inflammatory mediators into the circulation or through an effect on BM progenitors or inflammatory cells.
As most clinical trials have been performed during natural allergen exposure, studies evaluating the influence of upper airway disease on lower airways cannot properly assess the influence of nasal inflammation on lower airways. Provocative nasal allergen challenge has been used to help sort out the influences of allergic rhinitis on lower airways and specifically determine the influence of the upper airways on lower airway inflammation. Braunstahl performed nasal allergen provocations in allergic rhinitic patients without asthma and in normal control subjects.
An increase of eosinophils as well as increased expression of intercellular adhesion molecule-1 was observed in the nasal and bronchial biopsies of allergic rhinitic patients compared with control subjects. However, Beeh observed no significant difference in sputum eosinophils following nasal allergen provocation, although sputum ECP and intercellular adhesion molecule were increased. In addition, Braunstahl have shown that segmental bronchial allergen challenge can produce nasal eosinophilic inflammation.
Nasal Allergen Challenge: Systemic Effects
In this regard, we recently performed a study using repeated nasal challenges to determine if this can induce lower airway inflammation and to obtain a more accurate model of allergen exposure. Our preliminary results show that a large number of patients with allergic rhinitis with or without asthma can have significant lower airway inflammation after repeated nasal challenge.