Background: Local allergic rhinitis (LAR) is characterized by in situ production of specific IgE (sIgE) antibodies and a positive response to a nasal allergen provocation test (NAPT) in the absence of atopy.
Objective: The aim of this study was to investigate the immunological mechanisms involved in the immediate and late responses after nasal exposure to Dermatophagoides pteronyssinus (DP) in patients with LAR.
Methods: A total of 40 subjects with LAR to DP were studied and compared with 50 healthy controls. Immediate and late responses to NAPT-DP were assessed using a visual analogue scale of nasal symptoms and acoustic rhinometry. Tryptase, ECP, total and sIgE-DP were measured in the nasal lavage by immunoassay at baseline, 15 min, 1, 6 and 24 h after nasal challenge.
Results: NAPT-DP was positive in all patients, with significant increases in tryptase (45%), ECP (65%) and sIgE-DP (25%) (P<0.05). Sixty percent of the LAR patients presented an immediate response to NAPT-DP and 40% a dual response. Immediate responders showed a fast release of tryptase with a peak at 15 min after NAPT-DP, and a progressive increase in nasal ECP and sIgE-DP from 1 to 24 h after challenge, with a peak at 24 h. Dual responders presented persistently higher levels of tryptase from 15 min to 6 h after challenge, and a similar pattern of nasal release of ECP and sIgE-DP to immediate responders. There were no isolated late responders. NAPT-DP was negative in all healthy controls, with no increases in tryptase, ECP, or total and sIgE-DP in nasal secretions.
Conclusions: The results demonstrated the existence of immediate and dual responses to a NAPT with DP in LAR patients, with the local presence of sIgE and mast cell/eosinophil activation.