Different faces of regulatory DCs in homeostasis and immunity

Adaptive immunity protects against infection and cancer but is also a potential threat to the host because of the risk of excessive inflammation or the development of autoimmunity and allergy. Therefore, immune responses are subject to negative regulation. An important aspect of negative regulation is the generation of adaptive regulatory T (Treg) cells, which are currently thought to be induced mainly by immature (or partially mature) dendritic cells (DCs). In this Opinion, arguments will be presented for the concept that mature DCs can also have a key role in the development of Treg cells, both under conditions of immunity and homeostasis. Knowledge regarding the biology of regulatory DCs is of crucial importance for the development of novel therapeutic tools to correct immune aberrances in disease.