title: SSA/Ro antigen expressed on membrane of UVB-induced apoptotic keratinocytes is pathogenic but not detectable in supernatant of cell culture.
abstract: OBJECTIVE
  To better understand the potential effect of ultraviolet light on the photosensitivity of patients with lupus erythematosus (LE), to elucidate the mechanisms of SSA/Ro antibody formation after UV exposure, and to investigate the role of this autoantibody in the pathogenesis of skin lesions.
  
  
  METHODS
  Primary human keratinocytes were cultured in Medium-154. After ultraviolet-B light (UVB) irradiation, the keratinocytes were treated with affinity-purified anti-SSA/Ro sera and stained with FITC-labeled goat-anti-human IgG and propidium iodide (PI), followed by enzyme digestion with RNase, RNase-free DNase or RNase plus DNase. As target cells, the irradiated keratinocytes were incubated with affinity-purified anti-SSA/Ro sera, with or without fresh human sera as complement. The supernatants of irradiated keratinocytes were analyzed with ELISA method for SSA/Ro antigens.
  
  
  RESULTS
  UVB irradiation induced apoptotic blebs on the cell surface. The blebs were composed of ribonucleoproteins and contained SSA/Ro antigens. SSA/Ro antigens expressed on UVB irradiated keratinocytes bound to affinity-purified anti-SSA/Ro sera, leading to complement-dependent cytotoxicity. However, no SSA/Ro antigens were detected in the supernatants.
  
  
  CONCLUSIONS
  SSA/Ro, a ribonucleoprotein antigen expressed on UVB irradiated keratinocytes, may be recognized and presented to immune cells by a direct cell-cell contact other than be eliminated into the circulation.
authors.affiliation: Department of Dermatology, Peking Union Medical College Hospital, Beijing 100730, China. wangbx@csc.pumch.ac.cn
authors.forename: B
authors.initials: B
authors.lastname: Wang
authors.forename: X
authors.initials: X
authors.lastname: Dong
authors.forename: Z
authors.initials: Z
authors.lastname: Yuan
authors.forename: Y
authors.initials: Y
authors.lastname: Zuo
authors.forename: J
authors.initials: J
authors.lastname: Wang
mesh_terms: D017209:Apoptosis; D001323:Autoantibodies / Q000276:immunology; D001324:Autoantigens / Q000378:metabolism*; D002462:Cell Membrane / Q000276:immunology; D002478:Cells, Cultured; D006801:Humans; D007231:Infant, Newborn; D015603:Keratinocytes / Q000166:cytology / Q000276:immunology*; D020733:RNA, Small Cytoplasmic; D012261:Ribonucleoproteins / Q000378:metabolism*; D014466:Ultraviolet Rays; D000099207:SS-A Antigen
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; D020733:RNA, Small Cytoplasmic; D012261:Ribonucleoproteins; D000099207:SS-A Antigen; C116006:RO60 protein, human