Regulatory T cells in transplantation tolerance

Regulation by CD4+CD25+ T cells is one of the mechanisms used in vivo to both induce and maintain transplantation tolerance. Alloantigen-specific regulatory T (TReg) cells can be generated either in vivo or ex vivo. TReg cells are found in the graft, as well as in the peripheral lymphoid tissues, after transplantation. Alloantigen-specific and naturally occurring CD4+CD25+ TReg cells use similar mechanisms to control immune responsiveness in vivo. Alloantigen-specific TReg cells can be augmented by exposure to alloantigen. CD4+CD25+ TReg cells are one form of immunoregulation used to control responsiveness to alloantigens; the relationships between CD4+CD25+ TReg cells and other populations of regulatory cells remain to be clarified.