title: Regulation of cutaneous immunity by the environment: an important role for UV irradiation and vitamin D.
abstract: Cutaneous immunity can be controlled by environmental factors such as ultraviolet (UV) irradiation. UV irradiation affects keratinocytes, antigen presenting cells, such as epidermal Langerhans cells (LC), and T lymphocytes. LC are specialized in antigen presentation. Upon encountering exogenous antigens they migrate to skin draining lymph nodes where they present skin-acquired antigens to naive T cells resulting in effector T cell differentiation. T cell effector functions depend on the activation state of LC, which can be influenced by UV irradiation. After completion T cell mediated cutaneous immune responses need to be downregulated. In this context, CD4(+)CD25(+) regulatory T cells have been shown to play an important role in the suppression of cellular immune responses via inhibition of T cell proliferation. Naturally occurring regulatory T cells develop in the thymus and on the molecular level members of the B7- and TNF-superfamilies are critically involved in the peripheral maintenance of CD4(+)CD25(+) T cells. Substantial evidence exists that peripheral regulatory T cells are responsive to environmental stimuli including UV irradiation. UV-induced regulatory T cells are expanded by UV-exposed cutaneous LC and recently, epidermal expression of vitamin D3 or RANKL (CD254) has been shown to connect the environment to the immune system via expansion of CD4(+)CD25(+) regulatory T cells.
authors.affiliation: Department of Dermatology and Interdisciplinary Center of Clinical Research (IZKF), University of Münster, Münster, Germany. loserk@uni-muenster.de
authors.forename: Karin
authors.initials: K
authors.lastname: Loser
authors.forename: Stefan
authors.initials: S
authors.lastname: Beissert
mesh_terms: D000818:Animals; D017951:Antigen Presentation / Q000528:radiation effects; D015704:CD4 Antigens; D002454:Cell Differentiation / Q000528:radiation effects; D002762:Cholecalciferol / Q000276:immunology / Q000378:metabolism*; D004781:Environmental Exposure; D006801:Humans; D007108:Immune Tolerance / Q000528:radiation effects; D007109:Immunity / Q000528:radiation effects*; D053645:Interleukin-2 Receptor alpha Subunit; D053245:RANK Ligand / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D018124:Receptors, Tumor Necrosis Factor / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D015398:Signal Transduction / Q000276:immunology / Q000528:radiation effects; D012867:Skin / Q000276:immunology* / Q000473:pathology / Q000528:radiation effects; D050378:T-Lymphocytes, Regulatory / Q000276:immunology* / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D015704:CD4 Antigens; D053645:Interleukin-2 Receptor alpha Subunit; D053245:RANK Ligand; D018124:Receptors, Tumor Necrosis Factor; D002762:Cholecalciferol