title: Aldara®-induced skin inflammation: studies of patients with psoriasis.
abstract: BACKGROUND
  The application of Aldara(®) cream containing 5% imiquimod stimulates Toll-like receptor 7/8 on plasmacytoid dendritic cells, thereby producing a potent immunomodulatory effect. This has been reported to trigger psoriasis.
  
  
  OBJECTIVE
  To establish a human model of Aldara-induced psoriasis-like skin inflammation in patients with psoriasis.
  
  
  METHODS
  Nonlesional psoriatic skin of 13 patients was treated with Aldara for 2 or 7 days. The skin was evaluated clinically and histologically on days 2, 4 and 7. Cytokine expression in Aldara-treated, lesional and nonlesional psoriatic skin was compared using reverse-transcription quantitative polymerase chain reaction.
  
  
  RESULTS
  Nine of the 10 patients receiving application of Aldara under occlusion for 2 days developed redness, induration and scaling. Histological analysis revealed focal parakeratosis, acanthosis and perivascular mononuclear infiltration. On days 4 and 7 both clinical and histological signs of inflammation subsided. Two of the three patients treated with Aldara for 7 days developed erosions leading to psoriasis on day 21. Cytokine markers of activation of the innate immune system [interferon-α, interferon regulatory factor-7 and interleukin (IL)-1β] were equally expressed in lesional and Aldara-treated skin (n = 6). IL-6 and tumour necrosis factor-α were preferentially expressed in Aldara-treated skin. Adaptive immune system activation occurred only partially: IL-23p19 and IL-22 were similarly overexpressed in Aldara-treated and lesional psoriatic skin, but IL-17A and IL-12p40 were significantly underexpressed in Aldara-treated skin compared with lesional psoriatic skin. IL-10 was significantly overexpressed in Aldara-treated skin.
  
  
  CONCLUSIONS
  We were able to induce psoriasis-like skin inflammation although typical psoriasis did not develop, possibly due to incomplete adaptive immune system recruitment and the powerful stimulation of IL-10 counter-regulation.
authors: Department of Dermatology, Aarhus University Hospital, DK-8000, Aarhus C, Aarhus, Denmark.
authors: H
authors: H
authors: Vinter
authors: L
authors: L
authors: Iversen
authors: T
authors: T
authors: Steiniche
authors: K
authors: K
authors: Kragballe
authors: C
authors: C
authors: Johansen
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage / Q000009:adverse effects*; D000279:Administration, Cutaneous; D000634:Aminoquinolines / Q000008:administration & dosage / Q000009:adverse effects*; D003875:Drug Eruptions / Q000209:etiology* / Q000473:pathology; D005260:Female; D006801:Humans; D000077271:Imiquimod; D008297:Male; D008875:Middle Aged; D009824:Ointments / Q000008:administration & dosage; D011565:Psoriasis / Q000139:chemically induced* / Q000473:pathology
chemical_list: D000276:Adjuvants, Immunologic; D000634:Aminoquinolines; D009824:Ointments; D000077271:Imiquimod