Regulatory T cells: which role in the pathogenesis and treatment of allergic disorders?

Several recent data suggest the importance of different types of cells in the regulation of T‐cell effector‐mediated immune responses. However, a unique specific marker for these cells has not yet been identified. Moreover, in addition to a dedicated functional lineage, even a ‘plastic’ phenotype of regulatory T cells seems to exist. The lack of a unique specific marker for regulatory T cells, as well as their heterogeneity, make it difficult to determine whether a defect of regulatory T cells plays a role in the pathogenesis of common allergic disorders. Novel therapeutic strategies based on the induction or potentiation of regulatory T cells able to hamper allergic inflammatory reactions are desirable, but their possible efficacy and safety are not yet known. At present, therapeutic strategies able to induce an immune deviation of allergen‐specific type 2 T‐helper responses to a less polarized phenotype rather than a general immune suppression appear more realistic.