title: Sun exposure rapidly reduces plasmacytoid dendritic cells and inflammatory dermal dendritic cells in psoriatic skin.
abstract: BACKGROUND
  Interferon (IFN)-α-producing plasmacytoid dendritic cells (pDCs), inflammatory CD11c+CD1c- myeloid dendritic cells (mDCs) and macrophages have been found to contribute to the pathogenesis of psoriasis. Heliotherapy is a well-established treatment modality of this disease, although the details of how the effects are mediated are unknown.
  
  
  OBJECTIVE
  To test the hypothesis that exposure to natural sun affects pathogenic DC subsets in lesional skin.
  
  
  METHODS
  Skin biopsies were obtained from lesional and nonlesional skin in 10 patients with moderate to severe psoriasis subjected to controlled sun exposure on Gran Canaria. Biopsies were obtained at baseline, day 2 and day 16 and examined by immunohistochemistry.
  
  
  RESULTS
  Sixteen days of heliotherapy had excellent clinical effect on patients with psoriasis, with significant reductions in Psoriasis Area and Severity Index (PASI) scores. In lesional skin pDC numbers and expression of MxA, a surrogate marker for IFN-α, were rapidly reduced. Inflammatory CD11c+CD1c- mDCs were significantly reduced whereas resident dermal CD11c+CD1c+ mDCs were unaffected. Expression levels of the maturation marker DC-LAMP (CD208) on mDCs were significantly reduced after sun exposure, as were the numbers of lesional dermal macrophages. A decrease of dermal DC subsets and macrophages was already observed after 1 day of sun exposure. An additional finding was that DC-SIGN (CD209) is primarily expressed on CD163+ macrophages and not DCs.
  
  
  CONCLUSIONS
  The clinical improvement in psoriasis following sun exposure is associated with rapid changes in dermal DC populations and macrophages in lesional skin, preceding the clinical effect. These findings support the concept that these DC subsets are involved in the pathogenesis of psoriasis and suggest that sun-induced clinical benefit may partly be explained by its effect on dermal DCs.
authors.affiliation: LIIPAT, Institute of Pathology and Centre for Immune Regulation, Oslo University Hospital and University of Oslo, Norway. ingvild.heier@rr-research.no
authors.forename: I
authors.initials: I
authors.lastname: Heier
authors.forename: E
authors.initials: E
authors.lastname: Søyland
authors.forename: A-L
authors.initials: AL
authors.lastname: Krogstad
authors.forename: C
authors.initials: C
authors.lastname: Rodríguez-Gallego
authors.forename: M S
authors.initials: MS
authors.lastname: Nenseter
authors.forename: F L
authors.initials: FL
authors.lastname: Jahnsen
mesh_terms: D000328:Adult; D000368:Aged; D018949:Antigens, CD1 / Q000378:metabolism; D018845:CD11 Antigens / Q000378:metabolism; D003713:Dendritic Cells / Q000528:radiation effects*; D005260:Female; D019204:GTP-Binding Proteins / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism; D006370:Heliotherapy / Q000379:methods*; D006801:Humans; D007150:Immunohistochemistry; D007801:Langerhans Cells / Q000528:radiation effects*; D008264:Macrophages / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D064547:Myxovirus Resistance Proteins; D011565:Psoriasis / Q000209:etiology / Q000473:pathology* / Q000628:therapy; D013472:Sunlight; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D018949:Antigens, CD1; D018845:CD11 Antigens; C437944:CD1C protein, human; D006023:Glycoproteins; C579071:MX1 protein, human; D064547:Myxovirus Resistance Proteins; D019204:GTP-Binding Proteins