title: Evidence for a role of eosinophils in blister formation in bullous pemphigoid.
abstract: BACKGROUND
  Bullous pemphigoid (BP) is an autoimmune bullous disease of the skin characterized by subepidermal blister formation due to tissue-bound and circulating autoantibodies to the hemidesmosomal antigens BP180 and BP230. Although eosinophils and their toxic mediators are found abundantly in BP lesions, their role in blister formation has remained unclear.
  
  
  OBJECTIVE
  To investigate the role of eosinophils in the pathogenesis of BP with a specific focus on blister formation and to define conditions inducing dermal-epidermal separation (DES).
  
  
  METHODS
  In an ex vivo human model of BP, normal human skin cryosections were incubated with purified human peripheral blood eosinophils with or without activation in the presence or absence of BP autoantibodies, brefeldin A, diphenyleneiodonium, DNase or blocking F(ab')2fragments to CD16, CD18, CD32 and CD64. Dermal-epidermal separation was assessed by light microscopy studies and quantified using Fiji software.
  
  
  RESULTS
  Following activation with IL-5 and in the presence of BP autoantibodies, eosinophils induced separation along the dermal-epidermal junction of ex vivo skin. Dermal-epidermal separation was significantly reduced by blocking any of the following: Fcγ receptor binding (P = 0.048), eosinophil adhesion (P = 0.046), reactive oxygen species (ROS) production (P = 0.002), degranulation (P < 0.0001) or eosinophil extracellular trap (EET) formation (P = 0.048).
  
  
  CONCLUSIONS
  Our results provide evidence that IL-5-activated eosinophils directly contribute to BP blister formation in the presence of BP autoantibodies. Dermal-epidermal separation by IL-5-activated eosinophils depends on adhesion and Fcγ receptor activation, requires elevated ROS production and degranulation and involves EET formation. Thus, targeting eosinophils may be a promising therapeutic approach for BP.
authors.affiliation: Institute of Pharmacology, University of Bern, Bern, Switzerland.
authors.forename: E
authors.initials: E
authors.lastname: de Graauw
authors.affiliation: Department of Dermatology and Centre for Biological Signaling Studies (BIOSS), University Medical Center Freiburg, Freiburg, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Sitaru
authors.affiliation: Centre of Laboratory Medicine, Inselspital, Bern University Hospital, Bern, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Horn
authors.affiliation: Department of Dermatology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.
authors.forename: L
authors.initials: L
authors.lastname: Borradori
authors.affiliation: Institute of Pharmacology, University of Bern, Bern, Switzerland.
authors.forename: S
authors.identifier: http://orcid.org/0000-0002-9855-4305
authors.initials: S
authors.lastname: Yousefi
authors.affiliation: Institute of Pharmacology, University of Bern, Bern, Switzerland.
authors.forename: H-U
authors.initials: HU
authors.lastname: Simon
authors.affiliation: Department of Dermatology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.
authors.forename: D
authors.identifier: http://orcid.org/0000-0001-8965-9407
authors.initials: D
authors.lastname: Simon
mesh_terms: D001323:Autoantibodies / Q000276:immunology; D015415:Biomarkers; D001768:Blister / Q000209:etiology* / Q000473:pathology*; D018821:CD18 Antigens / Q000378:metabolism; D002448:Cell Adhesion / Q000187:drug effects / Q000276:immunology; D015550:Cell Degranulation / Q000276:immunology; D016207:Cytokines / Q000378:metabolism; D004804:Eosinophils / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D015848:Interleukin-5 / Q000378:metabolism; D010391:Pemphigoid, Bullous / Q000276:immunology* / Q000378:metabolism / Q000473:pathology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D017452:Receptors, IgG / Q000378:metabolism; D012867:Skin / Q000187:drug effects / Q000276:immunology / Q000378:metabolism / Q000473:pathology
chemical_list: D001323:Autoantibodies; D015415:Biomarkers; D018821:CD18 Antigens; D016207:Cytokines; D015848:Interleukin-5; D017382:Reactive Oxygen Species; D017452:Receptors, IgG
keywords: blister formation; bullous pemphigoid; degranulation; eosinophils; interleukin-5