Dendritic cells in tolerance induction.

Regulatory T cells (Treg) in broader terms consist of different subsets of T cells that are characterized by their ability to suppress proliferation of conventional effector T cells by various means. To date three main groups of Treg can de distinguished, mainly by their functional properties. The regulatory T cell family: distinct subsets and their interrelations. Briefly, T regulatory (Tr)-1 cells as well as T helper (Th)-3 T cells express common T cell markers such as CD4 and are characterized by secretion of IL-10 and TGF-beta, which provides a means by which proliferation of conventional CD4(+) cells is blocked. In contrast, genuine Treg that are characterized by their expression of CD25 block T cell proliferation by an unknown cell to cell contact dependent mechanism. However, there are many overlapping features shared by the different subtypes of regulatory T cells and the common denominator is the production of regulatory cytokines such as IL-10 and TGF-beta.