Factors Determining Tolerance to Nasal Allergen Exposure With Advanced Age in a Subset of Birch Pollen Allergic Subjects

Allergic rhinoconjunctivitis (AR) represents a major health burden affecting an estimated 1.4 billion people globally. It is characterized by inflammation of the nasal mucosa and conjunctiva in response to exposure to airborne allergens (e.g. pollen, dust mites). Interestingly, with advanced age, prevalence of AR decreases suggesting that a subset of allergic patients is able to develop tolerance towards allergens resulting in absence of symptoms. Understanding this mechanism governing natural tolerance development in the context of allergy is critical for the development of new therapeutic approaches and thus the aim of the proposed study. To address this question, the investigators plan to conduct a nasal allergen challenge study in patients aged 60+ who (1) are currently suffering from birch pollen allergy, (2) have a history of birch pollen allergy but absence of symptoms for at least three seasons and (3) never suffered from birch pollen allergy. After signing informed consent and fulfilling selection criteria, 38 patients per group will be intranasally challenged with birch pollen extract outside of the birch pollen season (October) and followed closely for up to 10 weeks to assess clinical parameters, cytokines, allergen-specific Immunoglobulin (Ig) levels as well as inflammatory cell subsets under controlled pollen exposure. In summary, this study will yield important information on the mechanisms underlying natural tolerance development in respiratory allergy with advanced age.