[Roles of extracellular vesicles in allergen-specific immunotherapy]

The prevalence of allergic diseases has been increasing, and sensitization to allergens such as cedar pollen and house dust mites has become a social issue. Allergic inflammation is primarily driven by type 2 inflammation, which is mediated by interleukin (IL)-4, IL-5, and IL-13 produced by Th2 cells and group 2 innate lymphoid cells (ILC2s). Recent studies have suggested that extracellular vesicle (EV) also plays critical roles in the pathogenesis of allergic diseases. EVs are lipid bilayer-enclosed particles containing proteins, mRNA, and microRNA (miRNA), which function as carriers of cytokines, antigens, and miRNAs, thereby activating Th2 cells and ILC2s and contributing to the progression of various inflammatory diseases. In contrast, we demonstrated that EVs contributed to the regression of allergic disease: EVs derived from the serum of allergen immunotherapy-treated mice exhibited suppression of ILC2 activation. Given their dual roles in both promoting and suppressing immune responses, EVs are emerging as promising targets and tools for novel treatment strategies. Understanding the immunomodulatory mechanisms mediated by EVs will be a crucial step toward developing safer and more effective therapies for allergic diseases. This review provides an overview of the role of EVs in allergic inflammation and highlights our recent findings on how allergen immunotherapy influences the properties and functions of EVs, thereby contributing to the regulation of immune responses and alleviation of allergic symptoms.