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 sel f-reactive T-cells contributed, to the maintenance of immunologic self-tole rance and its alteration can cause autoimmune disease. Efforts to delineate such a regulatory T-cell population have revealed that CD25(+) cells in th e CD4(+) population in normal naive animals bear the ability to prevent aut oimmune disease in vivo and, upon antigenic stimulation, suppress the activ ation/proliferation of other T cells in vitro, The CD25(+) CD4(+) regulator y T cells, which are naturally anergic and suppressive, appear to be produc ed 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.