title: Increased Activity and Number of Epidermal Melanocytes in Lesional Psoriatic Skin.
abstract: BACKGROUND
  Psoriatic lesions may resolve with hypo- or hyperpigmentation. The involvement of melanocytes in this dichotomous clinical outcome is not fully investigated.
  
  
  OBJECTIVE
  Qualitative and quantitative assessment of melanocytes in untreated lesional and non-lesional psoriatic skin (n = 15) and healthy controls (n = 10).
  
  
  METHODS
  Skin biopsies were labelled immunohistochemically (APAAP technique) with the antimelanocyte monoclonal antibodies (MoAbs) HMB45, Melan A, tyrosinase and microphthalmia-associated transcription factor (MITF). The labelled melanocytes were evaluated by an independent investigator with a digital image analyser.
  
  
  RESULTS
  Lesional melanocytes, in contrast to those in non-lesional and healthy skin, exhibited features of activation in the form of dilatation, prominent and long dendrites and intense labelling. The number of melanocytes was significantly increased in psoriatic lesions in comparison with non-lesional psoriatic and healthy skin as shown by counts of cells labelled with the MoAbs HMB45 (3-fold; p < 0.001), Melan A (1.6-fold; p < 0.01) and tyrosinase (1.5-fold; p < 0.01). In contrast, labelling with MITF revealed no significant difference (1.2-fold increase; p > 0.05). Likewise, no significant difference between non-lesional psoriatic and healthy skin control was found (p > 0.05). Furthermore, no positively labelled dermal cells were detected, apart from few only detected with Melan A.
  
  
  CONCLUSIONS
  Epidermal melanocyte activity and numbers are increased in the epidermal compartment of psoriatic lesions providing an explanation for postinflammatory hyperpigmentation.
authors: Departments of Dermatology, Venereology, Allergology and Immunology, Dessau Medical Center, Dessau, Germany.
authors: Mohamed Badawy
authors: MB
authors: Abdel-Naser
authors: Aikaterini I
authors: AI
authors: Liakou
authors: Rana
authors: R
authors: Elewa
authors: Sabine
authors: S
authors: Hippe
authors: Jürgen
authors: J
authors: Knolle
authors: Christos C
authors: CC
authors: Zouboulis
mesh_terms: D000328:Adult; D000368:Aged; D001706:Biopsy; D002452:Cell Count; D018450:Disease Progression; D004817:Epidermis / Q000378:metabolism / Q000473:pathology*; D005260:Female; D006801:Humans; D017495:Hyperpigmentation / Q000378:metabolism / Q000473:pathology*; D007150:Immunohistochemistry; D015603:Keratinocytes / Q000473:pathology*; D058965:MART-1 Antigen / Q000378:metabolism; D008297:Male; D008544:Melanocytes / Q000378:metabolism / Q000473:pathology*; D058950:Melanoma-Specific Antigens / Q000378:metabolism; D008875:Middle Aged; D014442:Monophenol Monooxygenase / Q000378:metabolism; D011565:Psoriasis / Q000378:metabolism / Q000473:pathology*; D058951:gp100 Melanoma Antigen
chemical_list: D058965:MART-1 Antigen; D058950:Melanoma-Specific Antigens; C548637:PMEL protein, human; D058951:gp100 Melanoma Antigen; D014442:Monophenol Monooxygenase