title: The tumour necrosis factor-alpha inhibitor adalimumab rapidly reverses the decrease in epidermal Langerhans cell density in psoriatic plaques.
abstract: BACKGROUND
  The pathophysiology of psoriasis is poorly understood, and the mechanism of action of biological agents interfering with tumour necrosis factor (TNF)-alpha that improve psoriatic plaques is completely unknown.
  
  
  OBJECTIVE
  To begin to unravel the mechanism of action, cellular changes occurring in plaques following administration of adalimumab, a humanized monoclonal antibody against TNF-alpha, were investigated.
  
  
  METHODS
  Thirteen different patients underwent sequential biopsies as part of a clinical trial. Each biopsy was immunostained and evaluated to calculate the relative density of epidermal Langerhans cells (LCs) before and after treatment (days 2, 7, 28, 84). To explore the basis for reduced epidermal LC densities in plaques, a SCID-Hu animal model was utilized. Acute psoriatic lesions were created within 2 weeks by injection of superantigen-activated CD4+ T cells into engrafted symptomless skin.
  
  
  RESULTS
  Compared with symptomless skin, untreated plaques had a significantly reduced density of epidermal LCs. There was a rapid increase in density of epidermal LCs in plaques following treatment with adalimumab beginning as early as day 7. The paucity of epidermal LCs in plaques was contrasted to the prominent density of LCs in other skin disorders with chronic inflammation and alterations in keratinization, including lichen planus and inflamed seborrhoeic keratosis. Rapid creation of plaques using the SCID-Hu model was accompanied by loss of epidermal LCs, indicating that diminished LC density occurs at an early stage of lesion formation.
  
  
  CONCLUSIONS
  These data shed light on a new immunopathological perspective highlighting a rapid loss of epidermal LCs in acute psoriatic lesions, with sustained decreased density of LCs in chronic plaques. Furthermore, an unexpected insight into the mechanism of action was uncovered for adalimumab, in which rapid restoration of epidermal LC density was observed.
authors.affiliation: Department of Internal Medicine, Division of Dermatology, Loyola University Medical Center, Maywood, IL 60153, USA.
authors.forename: K B
authors.initials: KB
authors.lastname: Gordon
authors.forename: B K
authors.initials: BK
authors.lastname: Bonish
authors.forename: T
authors.initials: T
authors.lastname: Patel
authors.forename: C L
authors.initials: CL
authors.lastname: Leonardi
authors.forename: B J
authors.initials: BJ
authors.lastname: Nickoloff
mesh_terms: D000068879:Adalimumab; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D001706:Biopsy; D002452:Cell Count; D004195:Disease Models, Animal; D004311:Double-Blind Method; D004817:Epidermis / Q000187:drug effects* / Q000473:pathology; D006801:Humans; D007801:Langerhans Cells / Q000187:drug effects* / Q000473:pathology; D051379:Mice; D016513:Mice, SCID; D011565:Psoriasis / Q000188:drug therapy / Q000473:pathology*; D016038:Skin Transplantation; D014183:Transplantation, Heterologous; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors*
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D014409:Tumor Necrosis Factor-alpha; D000068879:Adalimumab