title: Scarring skin lesions of discoid lupus erythematosus are characterized by high numbers of skin-homing cytotoxic lymphocytes associated with strong expression of the type I interferon-induced protein MxA.
abstract: BACKGROUND
  Infiltrating T lymphocytes are considered to play a major pathological role in skin lesions of cutaneous lupus erythematosus (CLE), a cutaneous autoimmune disease of unknown aetiology. Earlier histological studies revealed that the inflammatory infiltrate in CLE skin lesions is predominantly composed of T lymphocytes, with a slight predominance of CD4+ over CD8+ T cells, but failed to explain the development of scarring skin lesions, characteristic for chronic discoid lupus erythematosus (CDLE). Because recent investigations have highlighted the relevance of cytotoxic lymphocytes in autoimmune tissue destruction, we hypothesized that the scarring CDLE lesions might be caused by cytotoxic T lymphocytes.
  
  
  OBJECTIVE
  To analyse skin biopsies of 15 patients with CLE [10 female, five male; localized CDLE (lCDLE), n = 5; disseminated CDLE (dCDLE), n = 5, subacute CLE (SCLE), n = 5] and five control biopsies taken from healthy controls and to characterize the inflammatory infiltrate. Methods We used immunohistochemistry, including staining for the cytotoxic molecule granzyme B, the skin-homing molecule cutaneous lymphocyte antigen (CLA) and the protein MxA, which is specifically induced by type I interferons (IFNs).
  
  
  RESULTS
  We found a strong coexpression of granzyme B and CLA on lesional lymphocytes of patients with scarring lCDLE and dCDLE, which was significantly enhanced when compared with nonscarring SCLE and healthy controls. The increased expression of granzyme B was closely associated with the lesional expression of the type I IFN-induced protein MxA.
  
  
  CONCLUSIONS
  Our results provide evidence that type I IFNs and potentially autoreactive cytotoxic lymphocytes targeting adnexal structures are highly associated with scarring lupus erythematosus lesions and might be responsible for their scarring character.
authors.affiliation: Department of Dermatology, University of Bonn, Sigmund-Freud-Strasse 25, 53105 Bonn, Germany. joerg.wenzel@ukb.uni-bonn.de
authors.forename: J
authors.initials: J
authors.lastname: Wenzel
authors.forename: M
authors.initials: M
authors.lastname: Uerlich
authors.forename: E
authors.initials: E
authors.lastname: Wörrenkämper
authors.forename: S
authors.initials: S
authors.lastname: Freutel
authors.forename: T
authors.initials: T
authors.lastname: Bieber
authors.forename: T
authors.initials: T
authors.lastname: Tüting
mesh_terms: D001706:Biopsy; D002921:Cicatrix / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D005260:Female; D019204:GTP-Binding Proteins / Q000378:metabolism*; D053804:Granzymes; D006801:Humans; D007370:Interferon Type I / Q000096:biosynthesis; D008179:Lupus Erythematosus, Discoid / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D008297:Male; D064547:Myxovirus Resistance Proteins; D012697:Serine Endopeptidases / Q000378:metabolism; D012867:Skin / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
chemical_list: D007370:Interferon Type I; C579071:MX1 protein, human; D064547:Myxovirus Resistance Proteins; C509213:GZMB protein, human; D053804:Granzymes; D012697:Serine Endopeptidases; D019204:GTP-Binding Proteins