Regulatory T cells as a target for induction of immune tolerance in allergy

Purpose of review Reduced activity of regulatory T cells has recently been described in several diseases, including allergy. This concept of an alteration in the balance between the suppression and activation of harmful T helper type 2 immunity in allergy has important potential implications for strategies to prevent and control disease. Recent findings The past year has seen several important advances in analysing the determinants of this balance and models for inducing tolerance through regulatory T cells, including several different subtypes. These include the recognition that although T helper type 2 responses drive atopic sensitization, the expression of disease involves additional factors, and of a potential role for regulatory T cells in the development of neonatal tolerance. In addition to CD4(+)CD25(+) regulatory T cells, experimental protocols for the induction of IL-10-producing, transforming growth factor beta and T helper type 1 regulatory T cells have been described in mouse models of airway disease. IL-6 and costimulation have been identified as potential determinants of the balance between the suppression and activation of allergic responses. Summary Different strategies for inducing regulatory T cells in animal models of allergic inflammation and an improved understanding of the factors accentuating or reducing suppression have identified important questions for future translational research.