title: The langerhans cell.
abstract: Langerhans cells are the hone-marrow-derived immune cells of the epidermis; they express Ia antigens and receptors for the Fc portion of IgG and complement components and are required for epidermal-cell-induced antigen-specific, syngeneic and allogeneic T-cell activitation and the generation of epidermal-cell-induced cytotoxic T cells. Their presence within the epidermis and functional integrity determine whether topical application of haptens leads to specific sensitization or unresponsiveness, and in skin grafts of only I region disparate donors, they represent the cells responsible for the critical allosensitizing signal. UV radiation abrogates most of Langerhans cell functions in vitro; under certain conditions in vivo, it prevents contact sensitization favoring the development of specific unresponsiveness. UV radiation abrogates antigen-presenting capacities of epidermal cells by interfering both with the processing I of antigen by Langerhans cells and the production of the epidermal-cell-derived thymocyte activating factor required for optimal T-cell responses.
authors.affiliation: Department of Dermatology I, University of Vienna, Vienna. Austria.
authors.forename: K
authors.initials: K
authors.lastname: Wolff
authors.forename: G
authors.initials: G
authors.lastname: Stingl