ABSTRACT
Dendritic cells (DCs) are bone marrow (BM)-derived professional antigen (Ag) presenting cells (APCs) that take up, process, and display Ag for recognition by lymphocytes. Upon migration from blood into peripheral tissue, interstitial immature DCs survey the microenvironment by ingesting surrounding cell products and extracellular fluid by phagocytosis and macropinocytosis. When they encounter foreign Ags, including products of microbial and viral pathogens, DCs rapidly undergo maturation and acquire enhanced ability to migrate via lymph to draining lymph nodes. Research on these highly specialized APCs has shown that they have the potential to induce tolerance (i.e., with respect to self-Ag and in experimental autoimmune disease or transplantation models) as well as augment specific immune responses (i.e., tumor immunity and resistance to infectious agents). These divergent properties of DCs can be traced to the procedures by which they are isolated, propagated, or altered and to their state of maturation. Here, we concentrate on the tolerance-inducing properties of DCs and on how these can be promoted in vitro or in vivo for potential therapeutic application.
