Using regulatory APCs to induce/maintain tolerance

It is well established that antigen-presenting cells (APCs) such as dendritic cells (DCs) possess potent immune-stimulatory function. They are considered to be the key driving element for most immune, autoimmune, and host-defense responses. However, recent evidence suggests that as much as APCs can turn things on, they also have the capability to turn things off. To summarize the evidence for such regulatory function of APCs is the purpose of this review article. We are just beginning to understand whether regulatory APC function can be mapped to a separate lineage of APCs or whether it is more commonly acquired under certain maturation conditions. Furthermore, it becomes apparent that it is important to consider differences between human and mouse DCs as well as splenic-, lymph node-, or blood-derived APCs. We believe that, in the upcoming years, better understanding of positive and negative roles of APCs in immune regulation will benefit both sides of APC therapy: their use in enhancing immunity, for example, in vaccine design and cancer, as well as their application for the treatment of autoimmunity.