Immunologic tolerance maintained by CD25+ CD4+ regulatory T cells:: their common role in controlling autoimmunity, tumor immunity, and transplantation tolerance

There is accumulating evidence that T-cell-mediated dominant control of self-reactive T-cells contributed, to the maintenance of immunologic self-tolerance and its alteration can cause autoimmune disease. Efforts to delineate such a regulatory T-cell population have revealed that CD25(+) cells in the CD4(+) population in normal naive animals bear the ability to prevent autoimmune disease in vivo and, upon antigenic stimulation, suppress the activation/proliferation of other T cells in vitro, The CD25(+) CD4(+) regulatory T cells, which are naturally anergic and suppressive, appear to be produced by the normal thymus as a functionally distinct subpopulation of T cells. They play critical roles not only in preventing autoimmunity but also in controlling tumor immunity and transplantation tolerance.