T Cell Extracellular Vesicles: Orchestrators of Type 2 Inflammation in the Airway

Abstract

T cells are central orchestrators of immune responses and drive tissue pathology in diverse inflammatory diseases. To effectively coordinate tissue inflammation, T cells communicate with other cells in the local microenvironment through cell contact-mediated and secreted signals, including extracellular vesicles (EVs). EVs have emerged as mediators of communication between immune cells, but the functions of T cell EVs in signaling during tissue inflammation remain incompletely understood. In this dissertation, I investigated how T cell EVs contribute to inflammation through their interactions with eosinophils, critical effectors of allergic inflammation, in the pathological context of allergic asthma. By leveraging T cell-specific membrane tagging and single vesicle flow cytometry, I quantified T cell EVs in the airways during induced allergic inflammation in mice and found that T cell EVs are increased >10-fold in the lung lining fluid during allergic inflammation in mouse models of asthma. I further treated in vitro differentiated eosinophils with EVs isolated from primary T cell culture media and performed cell death assays and RNA sequencing. T cell EVs promoted eosinophil survival and induced pro-survival, activation, and metabolic gene expression in eosinophils. Additionally, I utilized small molecule inhibitor, blocking antibody, and enzyme immunoassay studies to identify that T cell EVs carry the surface cargo IL-3, which inhibits apoptosis in eosinophils through the activation of Jak/Stat signaling. The effect of EV-associated IL-3 is more potent at lower doses and longer lasting than that of soluble IL-3. This effect depends on T cell activation state, as only T cells activated through the T cell receptor secrete EVs carrying IL-3 that support eosinophil survival. Finally, I administered T cell EVs into the airways of mice with allergic inflammation and assessed lung eosinophilia. Instillation of activated T cell EVs into the airways was sufficient to prolong eosinophilia during an allergic reaction. In conclusion, the work presented in this dissertation supports a role for T cell EVs and their cytokine cargoes as a critical signaling axis in allergic lung inflammation. As cytokine-based communication is ubiquitous during immune responses, the capacity of EVs to serve as vehicles for cytokines could extend to virtually all inflammatory pathologies.