Regulatory T cells protect against the development of allergic diseases

Allergic diseases are caused by the overdevelopment of TH2-biased immune responses in susceptible individuals. While our understanding of TH2 responses has rapidly improved over the past ten years, our knowledge of the mechanisms that downregulate TH2-biased inflammatory responses has remained rudimentary. Both naturally occurring CD4(+)CD25(+) regulatory T cells and inducible forms of regulatory T cells have been shown to inhibit the inappropriate immune responses that lead to allergic diseases. Evidence is emerging that regulatory T cells play an important role in the homeostasis of immune responses not only in animal models, but also in patients. The article reviews the recent findings in this field and discusses the hypothesis that impaired expansion of natural and/or adaptive regulatory T cells leads to the development of allergy, and that treatment to induce allergenspecific regulatory T cells could provide curative therapies for allergy.