IL2 and allergic disease: In the context of Treg cell expansion, an increase in Treg cell numbers by the administration of low-dose IL-2 efficiently suppresses both allergy and auto-immune disease.44,45 Daily intraperitoneal injection of IL-2 for 5 days successfully expands the Treg cell population without affecting effector T cells.44 Our study revealed an increase in local IL-2-producing desensitized (or regulatory) MCs upon OIT, whereas a decrease in the abundance of these MCs simultaneously decreased Treg cell abundance at the local mucosa.