title: Plasmacytoid dendritic cells in alopecia areata: missing link?
abstract: BACKGROUND
  Type I interferon (IFN) signature has been implicated in alopecia areata (AA). However, type I IFN source has never been documented. Plasmacytoid dendritic cells (PDCs) are generally known to be the main source and most potent producers of local type I IFNs. Their role in AA pathogenesis has never been investigated.
  
  
  OBJECTIVE
  Investigate PDC role in AA.
  
  
  METHODS
  Nineteen AA cases were retrieved from our database and were immunohistochemically tested for PDC occurrence and activity using anti-BDCA-2 and anti-MxA antibodies respectively. Comparison to 10 trichotillomania and 7 androgenetic alopecia (AGA) cases was also done.
  
  
  RESULTS
  Plasmacytoid dendritic cells were present in all AA cases in a peri-bulbar location and, as indirectly assessed by MxA expression, were in an active state producing type I IFNs. All trichotillomania cases showed the presence of PDCs, though significantly less abundant and in a different distribution (mainly superficial perivascular) than that in AA. PDC presence and MxA expression were absent in AGA.
  
  
  CONCLUSIONS
  Plasmacytoid dendritic cells constitute a central component of the peribulbar infiltrate in AA suggesting a significant role in AA pathogenesis. Additionally, PDC distribution could help in microscopically differentiating AA from trichotillomania or AGA.
authors.affiliation: Dermatology Department, American University of Beirut Medical Center, Beirut, Lebanon.
authors.forename: J
authors.initials: J
authors.lastname: Abou Rahal
authors.affiliation: Dermatology Department, American University of Beirut Medical Center, Beirut, Lebanon.
authors.forename: M
authors.initials: M
authors.lastname: Kurban
authors.affiliation: Dermatology Department, American University of Beirut Medical Center, Beirut, Lebanon.
authors.forename: A-G
authors.initials: AG
authors.lastname: Kibbi
authors.affiliation: Dermatology Department, American University of Beirut Medical Center, Beirut, Lebanon.
authors.forename: O
authors.initials: O
authors.lastname: Abbas
mesh_terms: D000293:Adolescent; D000328:Adult; D000505:Alopecia / Q000378:metabolism; D000506:Alopecia Areata / Q000378:metabolism*; D002648:Child; D003713:Dendritic Cells / Q000502:physiology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007370:Interferon Type I / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D064547:Myxovirus Resistance Proteins / Q000378:metabolism; D014256:Trichotillomania / Q000378:metabolism
chemical_list: D007370:Interferon Type I; C579071:MX1 protein, human; D064547:Myxovirus Resistance Proteins