title: Skin sensitivity to UVB irradiation in systemic lupus erythematosus is not related to the level of apoptosis induction in keratinocytes.
abstract: OBJECTIVE
  Accumulation of apoptotic cells has been suggested to be involved in the pathogenesis of systemic lupus erythematosus (SLE). As sunlight exposure is one of the factors that can trigger disease activity, we hypothesized that UV light may induce increased numbers of apoptotic cells in SLE.
  
  
  METHODS
  Fourteen SLE patients and 16 controls were irradiated with UVB to determine their minimal erythemal dose (MED). Subsequently, skin was irradiated with 1 MED and 2 MED, respectively, and after 24 h skin biopsies were analysed immunohistologically for the number of apoptotic cells and presence of pyknotic nuclear debris.
  
  
  RESULTS
  MED was significantly decreased in SLE patients and the presence of decreased MED was associated with a history of butterfly rash. Decreased MED was not related to other skin-related ACR criteria or to autoantibody specificities. No differences were detected in the numbers of apoptotic keratinocytes between patients and controls or in the amount of pyknotic nuclear debris following 1 and 2 MED irradiation, respectively. Absolute UVB doses were correlated with the number of apoptotic keratinocytes; dose-responses did not differ significantly between patients and controls.
  
  
  CONCLUSIONS
  Increased sensitivity of SLE patients to UVB, although associated with a history of malar rash, is not related to increased induction of apoptosis or increased levels of secondary necrosis in the skin. Thus, compared with controls, UVB-induced apoptosis is not increased in SLE patients under physiological conditions.
authors.affiliation: Department of Rheumatology and Clinical Immunology, University Medical Center Groningen, 9700 RB Groningen, The Netherlands. e.reefman@med.umcg.nl
authors.forename: E
authors.initials: E
authors.lastname: Reefman
authors.forename: H
authors.initials: H
authors.lastname: Kuiper
authors.forename: M F
authors.initials: MF
authors.lastname: Jonkman
authors.forename: P C
authors.initials: PC
authors.lastname: Limburg
authors.forename: C G M
authors.initials: CG
authors.lastname: Kallenberg
authors.forename: M
authors.initials: M
authors.lastname: Bijl
mesh_terms: D000328:Adult; D017209:Apoptosis / Q000528:radiation effects*; D002467:Cell Nucleus / Q000473:pathology; D004307:Dose-Response Relationship, Radiation; D004817:Epidermis / Q000473:pathology; D004890:Erythema / Q000209:etiology; D005260:Female; D006801:Humans; D015603:Keratinocytes / Q000473:pathology / Q000528:radiation effects*; D008180:Lupus Erythematosus, Systemic / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000209:etiology / Q000473:pathology; D012867:Skin / Q000473:pathology / Q000528:radiation effects*; D014466:Ultraviolet Rays