Differentiation of T Regulatory Cells by Immature Dendritic Cells

The induction of antigen-specific tolerance is critical for the prevention of autoimmunity and maintenance of immune homeostasis. The immune system's ability to distinguish between self and non-self and between innocuous and harmful foreign antigens is controlled by mechanisms of central and peripheral tolerance. Central tolerance is a well established mechanism that involves deletion of self-reactive T cells upon interaction with bone marrow–derived dendritic cells (DCs) in the thymus 1,2. Well characterized mechanisms of peripheral tolerance include the induction of cell death or the development of a state of nonresponsiveness (anergy) of T cells 3,4. In addition, active suppression by T regulatory (Tr) cells is also key for peripheral tolerance 5. However, the mechanisms by which Tr cells arise in vivo and exert their immunoregulatory effects remain to be defined and are the...