The cross-talk between dendritic and regulatory T cells: good or evil?

Immune responses against pathogens require fine regulation to avoid excessive inflammation, which could be harmful to the host. Moreover, the immune system must be tolerant to nonpathogenic antigens to prevent allergy, autoimmunity, and transplant rejection. There is accumulating evidence that interactions between dendritic cells (DC) and regulatory T (Treg) cells play a crucial role in the balance between immune response and tolerance. Communications between these cells are complex, bidirectional, and mediated by soluble or cell surface molecules. The maturation status of DC, which may be influenced by different microenvironmental factors, is considered as an important checkpoint for the induction of peripheral tolerance through modifications of the activation status of T cells. Moreover, several lines of experimental evidence suggest that different subsets or the functional status of DC are also involved in the promotion of Treg cell differentiation. A better knowledge of the regulatory mechanisms of the immune response induced or inhibited by DC via their interactions with Treg cells could be relevant for the development of new, immunotherapeutic approaches.