Basophil-Derived Interleukin-4 Controls the Function of Natural Helper Cells, a Member of ILC2s, in Lung Inflammation

• Basophils are essential for protease allergen-induced airway responses
• Basophil-derived IL-4 controls ILC2-mediated eosinophilic inflammation
• IL-4 is necessary for the expression of CCL11, IL-9, and IL-13 from NH cells
• Interaction of basophils and ILC2 controls the IL-33 mediated allergic responses

SummaryAllergic asthma is an inflammatory disease characterized by lung eosinophilia controlled by type 2 cytokines. Cysteine proteases are potent triggers of allergic inflammation by causing barrier disruption in lung epithelial cells inducing the elevation of interleukin-5 (IL-5) and IL-13 from natural helper (NH) cells, a member of ILC2s, which leads to lung eosinophilia. In this study, we found that basophils play a crucial role in NH cell-mediated eosinophilic inflammation induced by protease allergens. Conditional deletion of basophils caused a resolution of the papain-induced eosinophilia and mucus production. Resolution of eosinophilia was also observed in mice lacking IL-4 specifically in basophils, indicating that basophil-derived IL-4 enhanced expression of the chemokine CCL11, as well as IL-5, IL-9, and IL-13 in NH cells, thus attracting eosinophils. These results demonstrate that IL-4 from basophils has an important role in the NH-derived cytokine and chemokine expression, subsequently leading to protease allergen-induced airway inflammation.

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