Dendritic epidermal T cells: their role in the early phase of ectromelia virus infection.

INTRODUCTION: Dendritic epidermal T cells (DETCs) are bone marrow-derived T lymphocytes that express a canonical gammadelta TCR and form a dense network in the murine skin. Here, we sought to determine their role during the early phase of ectromelia virus (ECTV) infection. MATERIALS/METHODS: In vivo and in vitro models were established for this purpose. In the first model, C57BL/6 mice were intradermally infected into the central part of the ear pinnas with 105 PFU ECTV-Mos strain per ear. At indicated time-points, the total pinna cell population was isolated to determine the presence of DETCs and the enumeration of DETCs secreting IFN-gamma under in vitro stimulation. Purified DETCs were also analyzed for certain gene expressions by RT-PCR. In the second model, purified DETCs isolated from pinnas of uninfected C57BL/6 mice were stimulated in vitro with 5 MOI of UV-inactivated ECTV-Mos. Total RNA was isolated at indicated time-points for RT-PCR gene expression evaluation. RESULTS: A rapid increase in DETCs number in the pinnas was observed for 24 hours post-infection. During the next 24 h the DETCs number decreased, reaching control values. Rapid but short-lasting INF-gamma secretion by purified DETCs in vitro was observed and correlated well with the expression of the beta chemokine CCL5 gene responsible for macrophage and neutrophil attraction. It was also accompanied by DETCs expression of the immunoregulatory factors TGF-beta, GM-CSF, and KGF genes important for maintaining skin integrity. CONCLUSIONS: DETCs from mice infected with ECTV-Mos were rapidly induced to cascade the secretion of mediators that contribute to both immune protection and the control of skin integrity.

[Dendritic epidermal T cells: sentinels of the skin]. / Dendrytyczne epidermalne limfocyty T--straznicy skóry.

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.