Segmental allergen challenge in patients with atopic asthma leads to increased IL-9 expression in bronchoalveolar lavage fluid lymphocytes.

Background: IL-9 is a T(H)2 cell-derived cytokine that might be involved in the pathophysiology of allergic diseases. Little is known about its expression and release during the allergic response in the human lung.

Objective: The expression of IL-9 was measured in 10 atopic subjects with mild asthma and 5 nonatopic healthy control subjects at baseline and 24 hours after segmental sham and allergen challenge.