Nasal response to a single antigen challenge in patients with allergic rhinitis - inflammatory cell recruitment persists up to 48 hours

Background Allergen challenge in some patients with respiratory allergy is followed by an early and a late reaction. Objective To evaluate the duration of mediator release and inflammatory cel l recruitment during the late antigen-induced nasal response. Methods Eight patients with seasonal allergic rhinitis due to grass pollen underwent local challenge with the relevant allergen, a non-relevant allerg en (Parietaria judaica), and nebulized saline solution. Nasal lavages were performed at baseline and 6, 24, 48, 72 h after challenge. Eosinophil catio nic protein (ECP), leukotriene C-4 (LTC4), leukotriene B-4 (LTB4) myelopero xidase (MPO) and prostaglandin D-2 (PGD(2)) levels were radioimmunoassayed and histamine concentration was measured by an automated fluorometric metho d. Results Nasal challenge with the relevant antigen induced a response 6 h af ter stimulation, which subsided within 24 h. Eosinophilia, observed in the nasal lavages collected from 6 to 24 h after this challenge, was accompanie d by ECP release. Neutrophilia were found in the nasal lavages collected fr om 6 to 24 h after challenge. The increase in neutrophil number correlated with MPO levels and LTB4 concentrations, but not with the intensity of nasa l obstruction. Antigen challenge also induced significant recruitment of mo nonuclear cells 48 h after provocation. The challenge significantly raised histamine, but not PGD(2), levels in the nasal lavages collected 6 h after provocation. A trend towards an increase in LTC4 levels in the nasal lavage s collected 6 h after specific antigen challenge was also found. Nasal chal lenge with a non-relevant allergen or with saline solution did not cause ei ther inflammatory cell recruitment or mediator release. Conclusion Nasal challenge with the relevant antigen can induce a late resp onse characterized by local accumulation of eosinophils, neutrophils and mo nonuclear cells persisting for 48 h and accompanied by release of ECP, MPO, LTB4 and histamine. These results indicate that a single antigen challenge in patients with allergic rhinitis causes prolonged inflammatory alteratio ns which may contribute to the development of airway hyperreactivity.