Dendritic cells and CD4+ CD25+ T regulatory cells:: Crosstalk between two professionals in immunity versus tolerance

Dendritic cells (DCs) are professional antigen presenting cells (APCs). CD4(+)CD25(+) T regulatory cells (T regs) are recognized as professional regulatory cells. DCs not only initiate T cell immunity by uptake, processing and presentation of specific antigens, but also induce immune tolerance by deletion of T cells and/or induction of regulatory T cells. CD4(+)CD25(+) T regs maintain immune tolerance by suppressing the function of CD4(+) and CD8(+) T cells, B cells, macrophages, DCs and NK cells. It would be inconceivable that the delicate balance between immunity and tolerance could be kept impeccable without the crosstalk between DCs and CD4(+)CD25(+) T regs. This review focuses on the recent development in our understanding of DCs and CD4(+)CD25(+) T regs in immune tolerance, with transforming growth factor-beta (TGF-beta) serving as a potential link between these two professionals.