title: The Langerhans cell.
abstract: Langerhans cells are the bone-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 of antigen by Langerhans cells and the production of the epidermal-cell-derived thymocyte activating factor required for optimal T-cell responses.
mesh_terms: D000818:Animals; D000941:Antigens / Q000276:immunology; D003602:Cytotoxicity, Immunologic; D003877:Dermatitis, Contact / Q000276:immunology; D006084:Graft Rejection; D006241:Haptens / Q000276:immunology; D006651:Histocytochemistry; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000276:immunology; D007158:Immunologic Techniques; D007801:Langerhans Cells / Q000166:cytology / Q000276:immunology* / Q000528:radiation effects; D008213:Lymphocyte Activation; D012867:Skin / Q000276:immunology*; D016038:Skin Transplantation; D013601:T-Lymphocytes / Q000276:immunology; D014466:Ultraviolet Rays
chemical_list: D000941:Antigens; D006241:Haptens