[Dendritic epidermal T cells: sentinels of the skin]

Dendritic epidermal T cells (DETCs) are T lymphocytes that express a canonical gammadeltaTCR and form a dense network in murine skin. The major difference between ab and gammadeltaT cells is that the latter do not require antigen presentation in the context of MHC I or II for stimulation. Using their gammadeltaTCR they recognize so far unknown ligands expressed by stressed, infected, or transformed keratinocytes. Since DETCs are located only in the skin, they provide the front line of defense against invasion, but also take part in immune regulation. These cells are in intimate contact with neighboring cells and, through their unique antigen recognition, can immediately react to incoming signals and secrete a variety of cytokines, growth factors, and chemokines that have been implicated in tissue repair and cell survival, proliferation, migration, and recruitment. They play a large role in maintaining skin homeostasis by rapid induction of immune response and at the same time they can release immunoregulatory mediators that inhibit inflammation and consequently maintain integrity of the skin.