Interleukin-2-Dependent Allergen-Specific Tissue-Resident Memory Cells Drive Asthma

• Allergen-specific CD4+ Th2 memory cells were tracked with MHC class II tetramers
• Lung resident memory T cells formed after intranasal house dust mite antigen exposure
• IL-2 signaling was required for the formation of lung-resident memory Th2 cells
• The lack of BCL-6 expression or B cells promoted T cell entry into the lung

SummaryExposure to inhaled allergens generates T helper 2 (Th2) CD4+ T cells that contribute to episodes of inflammation associated with asthma. Little is known about allergen-specific Th2 memory cells and their contribution to airway inflammation. We generated reagents to understand how endogenous CD4+ T cells specific for a house dust mite (HDM) allergen form and function. After allergen exposure, HDM-specific memory cells persisted as central memory cells in the lymphoid organs and tissue-resident memory cells in the lung. Experimental blockade of lymphocyte migration demonstrated that lung-resident cells were sufficient to induce airway hyper-responsiveness, which depended upon CD4+ T cells. Investigation into the differentiation of pathogenic Trm cells revealed that interleukin-2 (IL-2) signaling was required for residency and directed a program of tissue homing migrational cues. These studies thus identify IL-2-dependent resident Th2 memory cells as drivers of lung allergic responses.