Activated T cells secrete extracellular vesicles in the allergic airway that enhance eosinophil viability

T cells are not only central orchestrators of immune responses, but they drive tissue pathology in many inflammatory diseases. In allergic asthma, the activation of CD4+ T helper cells in response to allergens drives chronic type 2 lung inflammation characterized by the recruitment of eosinophils. Given the emerging roles of extracellular vesicles (EVs) as mediators of cell-to-cell communication, we hypothesized that T cells would secrete EVs in the lung to regulate the local inflammatory response. Using T cell specific membrane tagging and single vesicle flow cytometry, we found that T cell EVs are secreted into lung lining fluid during allergic inflammation in a mouse model of asthma. Functionally, EVs secreted by polarized T helper type 2 (Th2) cells promote eosinophil survival in vitro. This effect is only seen with EVs collected from Th2 cells activated through the T cell receptor. Activated Th2 cell EVs promote eosinophil survival by a surface-cargo dependent anti-apoptotic mechanism, inducing pro-survival and activation gene expression programs in these target cells. In vivo, activated Th2 cell EVs prolong eosinophilia in the lung after administration into the airways during allergic inflammation. Together, this study adds to emerging literature linking cellular activation state to EV function and supports a role for T cell EVs in enhancing tissue inflammation. To investigate the effects of Th2 cell extracellular vesicles (EVs) on eosinophils, we differentinated eosinophils from bone marrow and treated the eosinophils with EVs purified from Th2 cell culture media by size exclusion chromatography and ultrafiltration or parallelly processed non-conditioned media as a control. We performed RNA-sequencing on 3 eosinophil biological replicates treated with 5e9 EVs/ml or an equal volume of media control for 24 hours. We then analyzed differential gene expression between Th2 cell EV-treated and media-treated eosinophils.