title: Plasmacytoid dendritic cells are absent in skin lesions of polymorphic light eruption.
abstract: OBJECTIVE
  Polymorphic light eruption (PLE) is a common photodermatosis of potential autoimmune origin, and an overlap with lupus erythematosus (LE) has been described. Plasmacytoid dendritic cell (PDC)-induced expression of interferon (IFN)-alpha has been found to be present in LE skin lesions and plays a pivotal role in the pathogenesis of LE by promoting autoimmunity. We therefore asked whether PDCs may also be involved in the pathogenesis of PLE and searched for those cells [which can be identified by their high levels of interleukin (IL)-3 receptor alpha chain (CD123), combined with other cell markers such as CD68] in skin lesions.
  
  
  METHODS
  Paraffin-embedded biopsy specimens from a total of 27 patients with clinically and histologically confirmed PLE (nine women, mean age 32.7 years, age range 18-43), LE (seven women, four men, CCLE: n=4, SCLE: n=2, lupus tumidus: n=5, mean age 48.5 years, age range 41-65) or psoriasis (four women, three men, mean age 43.3 years, age range 19-54) (as control group) were analyzed by immunohistochemical CD68/CD123 double staining. Quantification of the immunohistochemical staining was performed by visual cell counting of CD68-/CD123+, CD68+/123-, and CD68+/CD123+ cells separately in the epidermis and dermis of the samples in at least 10 random fields per sample at x 400 microscopic magnification by two of the investigators in a blinded fashion.
  
  
  RESULTS
  Microscopic examination of the immunohistochemically stained sections revealed that CD68+/CD123+ cells were present in most specimens obtained from LE [10/11 (91%)] and psoriasis [6/7 (86%)] patients but not at all in those obtained from PLE patients. Quantification and statistical analysis of the dermal infiltrate revealed that CD68+/CD123+ cells were present at a mean+/-SEM field density of 5.6+/-1.3 in LE, 1.6+/-0.6 in psoriasis but totally absent in PLE (P=0.0010 vs. LE, P=0.0135 vs. psoriasis by an unpaired Student's t-test).
  
  
  CONCLUSIONS
  The results confirm the potential significance of PDCs in LE and psoriasis, however the absence of PDCs in PLE contradicts the hypothesis that these cells might play a role in the latter disease.
authors.affiliation: Research Unit for Photodermatology, Medical University of Graz, Graz, Austria.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Wackernagel
authors.forename: Cesare
authors.initials: C
authors.lastname: Massone
authors.forename: Gerald
authors.initials: G
authors.lastname: Hoefler
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Steinbauer
authors.forename: Helmut
authors.initials: H
authors.lastname: Kerl
authors.forename: Peter
authors.initials: P
authors.lastname: Wolf
mesh_terms: D000293:Adolescent; D000328:Adult; D001706:Biopsy; D003713:Dendritic Cells / Q000166:cytology* / Q000378:metabolism; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D007377:Interleukin-3 / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010787:Photosensitivity Disorders / Q000378:metabolism / Q000473:pathology*
chemical_list: D007377:Interleukin-3