title: The role of hair follicle immune privilege collapse in alopecia areata: status and perspectives.
abstract: Alopecia areata (AA) may represent a CD8+T cell-mediated, organ-specific autoimmune disease in which as yet elusive autoantigens are recognized, once they become exposed by ectopic major histocompatibility complex class I expression by anagen hair follicles (HFs) that have lost their relative immune privilege (IP). On this basis, AA research is chiefly challenged with identifying the autoreactive CD8+T cells and their cognate autoantigens as well as key inducers of HF-IP collapse and "HF-IP guardians" that prevent and/or can restore IP collapse. However, natural killer group 2D-positive (NKG2D+) cells (incl. NK, NKT, and CD8+T cells) and NKG2D-activating ligands from the MICA (MHC I-related chain A) family may also have a key role in AA pathogenesis, as a massive infiltrate of IFN-γ-secreting NKG2D+ cells alone suffices to induce the AA phenotype. Therefore, we speculate that AA may represent a stereotypic, but distinct HF response pattern to inflammatory insults associated with HF-IP collapse.
authors: 1] Department of Dermatology, University of Lübeck, Lübeck, Germany [2] Institute of Inflammation and Repair, University of Manchester, Manchester, UK.
authors: Ralf
authors: R
authors: Paus
authors: Marta
authors: M
authors: Bertolini
mesh_terms: D000506:Alopecia Areata / Q000276:immunology*; D000818:Animals; D001324:Autoantigens / Q000276:immunology; D001327:Autoimmune Diseases / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes; D058851:GPI-Linked Proteins / Q000276:immunology; D018859:Hair Follicle / Q000276:immunology*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000276:immunology; D007694:Killer Cells, Natural / Q000737:chemistry / Q000276:immunology; D051379:Mice; D055655:NK Cell Lectin-Like Receptor Subfamily K / Q000032:analysis; D017634:Self Tolerance / Q000276:immunology*
chemical_list: D001324:Autoantigens; D058851:GPI-Linked Proteins; D036341:Intercellular Signaling Peptides and Proteins; C527085:KLRK1 protein, human; D055655:NK Cell Lectin-Like Receptor Subfamily K; C423230:ULBP2 protein, human