Helminths, allergens, and certain protists all stimulate a type 2 immune response and contribute significantly to the global disease burden. Currently, more than 1 billion individuals worldwide are infected with helminths, and the rising incidence of allergic disease represents an emerging epidemic. The sensing and signaling events that initiate type 2 immunity remain poorly understood, but in the small intestine they require epithelial tuft cells. Tuft cells regulate a tuft-ILC2 circuit in which tuft cell-derived IL-25 activates group 2 innate lymphoid cells (ILC2s) in the underlying tissue. ILC2s secrete the canonical type 2 cytokines IL-5, -9, and -13, which collectively drive hallmarks of type 2 immunity, such as eosinophilia and tissue remodeling. IL-13 also promotes a feed-forward response by inducing tuft and goblet cell hyperplasia. The immune function of tuft cells requires a chemosensory pathway and recent studies identified the microbial metabolite succinate as an intestinal tuft cell ligand that is sufficient to activate the tuft-ILC2 circuit. Tuft cells therefore act as IL-25- secreting immune sentinels, but several lines of evidence support the central hypothesis of this proposal that additional tuft cell effector functions must exist: (1) Tuft cells express IL-25 constitutively, but the feed-forward tuft-ILC2 circuit is only activated in the presence of helminths or protists, suggesting additional activating signals; (2) the initiation of tuft cell hyperplasia after immune sensing has occurred suggests tuft cells contribute to the effector stages of type 2 immunity; and (3) helminth clearance is more delayed in tuft cell- deficient mice than in mice that lack only IL-25. The goal of this proposal is therefore to discover and characterize novel tuft cell effector functions in the small intestine. Using a combination of innovative in vitro assays and in vivo helminth infection of genetically modified mouse strains, we propose to test the regulation and function of tuft cell-derived IL-25, leukotriene C4, and acetylcholine. These studies should identify novel targets for therapeutic intervention in both helminth infection and allergic disease.

Public Health Relevance

Parasitic worms, allergens, and some protists all trigger a ?type 2? immune response, but we do not yet fully understand the underlying mechanisms of immune sensing and regulation. More than 1 billion individuals are currently infected with worms, and the incidence of allergies is rising worldwide. By studying the role of epithelial tuft cells in type 2 immunity, we hope to discover novel targets for therapeutic intervention in helminth infection and allergy.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Gastrointestinal Mucosal Pathobiology Study Section (GMPB)
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Rothermel, Annette L
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University of Washington
Schools of Medicine
United States
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