Regulatory T Cells in Allergic Disease

Abstract

Allergic diseases, including asthma, are associated with the development of allergen-specific Th2 and IgE responses, which regulate the early and late phase allergic reactions. Naturally occurring T regulatory cells (Treg), which are present in all healthy individuals together with antigen-induced Treg that secrete inhibitory cytokines such as IL-10 and/or TGFβ, in the periphery. The balance between allergen-specific disease-promoting T helper 2 cells (Th2) and various Treg populations appears to be decisive in the development of a disease promoting allergic versus a non-disease promoting or tolerogenic immune response respectively. Treg specific for common environmental allergens represent the dominant subset in non-atopic individuals implying a state of natural or active tolerance to allergen in health. In contrast, there is a high frequency of allergen-specific Th2 cells in allergic individuals. The function of both naturally occurring and adaptive or inducible Treg appears to be impaired in active allergic disease. Therapies associated with amelioration of disease symptoms, including allergen immunotherapy and glucocorticoids, have been shown to modulate favourably Treg function. Strategies to improve current therapeutic regimens are increasingly focusing on manipulation of Treg for patient benefit.