CD3+CD4-CD8- alphabeta-TCR+ T cell as immune regulatory cell.

Down-regulation of immune responses by regulatory T cells is one of the major mechanisms involved in the induction of tolerance to self- and alloantigens as demonstrated in a number of models of transplantation and autoimmunity. It is clear that regulatory T cells consist of different subsets. Recently a novel subset of antigen-specific alphabeta-TCR+ CD4-CD8- (double negative, DN) regulatory T cells has been found to be able to inhibit the function of the CD8+ T cells carrying the same T cell receptor specificity and prevent the rejection of skin allografts. Identification of the DN regulatory T cells and their novel mechanism of suppression can help us to understand how donor-specific transplantation tolerance can be achieved and to explain how tolerance to self-antigens can be maintained in the periphery.