The life of regulatory T cells

Foxp3(+) regulatory T (T-reg) cells are essential for maintaining self-tolerance and preventing autoimmune reactions. T-reg cells arise as a consequence of self-antigen recognition during the maturation of cells in the thymus, and also following self-antigen recognition in the periphery. Both thymic and peripherally generated T-reg cells respond to antigen recognition by expanding in number, increasing their suppressive activity, and accumulating in the tissue where the antigen is located. A fraction of these activated "effector" T-reg cells survive even in the absence of antigen expression and continue to control inflammatory reaction in the tissues, thus functioning as a population of "memory" T-reg cells. Antigen exposure and the presence of IL-2 are key determinants in the generation of memory T-reg cells. These results provide a foundation for studying the role of memory T-reg cells in controlling and treating autoimmune disorders and for testing the hypothesis that defects in the generation and maintenance of these cells underlie chronic, relapsing inflammatory diseases.