Phenotypical and functional specialization of FOXP3+ regulatory T cells

Abstract

T_Reg cells 'walk the line' by preventing autoimmunity while allowing the formation of protective antipathogen and antitumour immune responses. T_Reg cells can be divided, based on their expression of activation and homing receptors, into populations with distinct migratory, functional and homeostatic characteristics. T_Reg cells accumulate within both lymphoid and non-lymphoid tissues, and the proper localization of T_Reg cells is critical to their ability to function and maintain immune homeostasis in vivo. T_Reg cells use distinct molecular programmes to restrain T_H1, T_H2 and T_H17 cell-mediated immune responses. T_Reg cells can alter their phenotype and function in response to molecular cues such as cytokines and vitamin metabolites that are present in the immune environment. The phenotypical and functional stability of T_Reg cells remains controversial, and different experimental systems have yielded conflicting results regarding the ability of T_Reg cells to convert to other pro-inflammatory T cell lineages.