Allergen-induced Increases in Sputum Levels of Group 2 Innate Lymphoid Cells in Subjects with Asthma

Rationale: Group 2 innate lymphoid cells (ILC2), a major source of type 2 cytokines, initiate eosinophilic inflammatory responses in murine models of asthma.Objectives: To investigate the role of ILC2 in allergen-induced airway eosinophilic responses in subjects with atopy and asthma.Methods: Using a diluent-controlled allergen challenge crossover study, where all subjects (n = 10) developed allergen-induced early and late responses, airway eosinophilia, and increased methacholine airway responsiveness, bone marrow, blood, and sputum samples were collected before and after inhalation challenge.Measurements and Main Results: ILC2 (lin−FceRI−CD45+CD127+ST2+) and CD4+T lymphocytes were enumerated by flow cytometry, as well as intracellular IL-5 and IL-13 expression. Steroid sensitivity of ILC2 and CD4+ T cells was investigated in vitro. A significant increase in total, IL-5+, IL-13+, and CRTH2+ ILC2 was found in sputum, 24 hours after allergen, coincident with a significant decrease in blood ILC2. Total, IL-...