title: The human hair follicle: a reservoir of CD40+ B7-deficient Langerhans cells that repopulate epidermis after UVB exposure.
abstract: The ability of skin to maintain its protective structural and functional integrity depends on both resident and circulating cells. Until now, it was thought that dendritic antigen presenting cells of epidermis (Langerhans cells) were replaced by circulating bone marrow derived precursors. Here we show by immunostaining studies of timed biopsies taken from human skin after ultraviolet exposure, that hair follicle is a critical reservoir of Langerhans cells that repopulate epidermis depleted of Langerhans cells by a single four minimal erythema dose of ultraviolet B. Immunostaining with antibodies to thymidine dimers showed that ultraviolet B only penetrated the superficial hair follicle opening, whereas deeper follicle was relatively protected. Langerhans cells migrating from hair follicle into epidermis 72 h after ultraviolet exposure have a partial deficiency of molecules important to T cell costimulation. We used four color flow cytometry to show that Langerhans cells isolated from epidermis 72 h after ultraviolet B can upregulate CD40 but not B7-1 or B7-2 expression in culture, suggesting a different phenotype of hair follicle Langerhans cells. Therefore, the hair follicle is a specialized immune compartment of the skin that serves as an intermediate reservoir of Langerhans cells between bone marrow and epidermis, and that may play a critical role in immune surveillance.
authors.affiliation: Department of Dermatology, Case Western Reserve University and University Hospitals of Cleveland, Ohio 44106, USA.
authors.forename: A C
authors.initials: AC
authors.lastname: Gilliam
authors.forename: I B
authors.initials: IB
authors.lastname: Kremer
authors.forename: Y
authors.initials: Y
authors.lastname: Yoshida
authors.forename: S R
authors.initials: SR
authors.lastname: Stevens
authors.forename: E
authors.initials: E
authors.lastname: Tootell
authors.forename: M B
authors.initials: MB
authors.lastname: Teunissen
authors.forename: C
authors.initials: C
authors.lastname: Hammerberg
authors.forename: K D
authors.initials: KD
authors.lastname: Cooper
mesh_terms: D018122:B7-1 Antigen / Q000032:analysis; D019013:CD40 Antigens / Q000032:analysis; D002455:Cell Division / Q000502:physiology; D000078404:Epidermal Cells; D004817:Epidermis / Q000528:radiation effects*; D018859:Hair Follicle / Q000166:cytology* / Q000276:immunology / Q000528:radiation effects*; D006801:Humans; D007801:Langerhans Cells / Q000276:immunology / Q000502:physiology* / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D018122:B7-1 Antigen; D019013:CD40 Antigens