Serum IL-9 levels depend on allergen exposure: preliminary study.

Background: Th9 is a new T cell subset characterized by interleukin 9 (IL-9) production. Serum IL-9 levels are related to symptom severity in patients with allergic rhinitis (AR). This study aimed at investigating whether IL-9 may depend on allergen exposure.

Methods: 35 AR patients (16 males, mean age 33.2 years) with monosensitization to Parietaria were studied when symptomatic; 38 AR patients (22 males, mean age 30.9 years) with monosensitization to birch were recruited at the same time, but were symptom free. Serum IL-9 was assayed in all patients.

Results: Patients with Parietaria allergy and exposed to allergen had higher serum IL-9 levels than patients with birch allergy and not exposed to allergen (p<0.05).

Conclusions: This preliminary study shows that serum IL-9 levels may depend on allergen exposure: symptomatic patients with pollen-induced AR, evaluated during the pollen season, have higher values than patients studied outside the pollen season and without symptoms.