Mammalian antigen-presenting cells that link the innate and adaptive immune systems. They are found on mucosal membranes and in the blood. There are at least two types: myeloid and plasmacytoid dendritic cells, based on cell characteristics, morphology, substances they secrete, and the innate immune receptors with which they interact. When activated, they migrate to the lymph nodes where they signal lymphocytes to initiate and shape the adaptive immune response to an invading pathogen.