An off switch for helminth immunity: Group 2 innate lymphoid cells (ILC2s) are involved in responses to helminths, viruses, and allergens. Moriyamaet al.found that ILC2s interact with the nervous system to modulate helminth immunity. ILC2s from the small intestine expressed the β₂-adrenergic receptor (β₂AR), which normally interacts with the neurotransmitter epinephrine. Inactivating β₂AR resulted in lower helminth burden and more ILC2s, eosinophils, and type 2 cytokine production in mice. Conversely, treatment of helminth-infected mice with a β₂AR agonist enhanced worm burden and reduced proliferation of ILC2s. Thus, β₂AR negatively regulates ILC2-driven protective immunity.Science, this issue p.1056