title: Antineutrophil cytoplasmic autoantibodies in patients with systemic lupus erythematosus recognize a novel 69 kDa target antigen of neutrophil granules.
abstract: OBJECTIVE
  Antineutrophil cytoplasmic autoantibodies (ANCA) were found in patients with systemic lupus erythematosus (SLE). Cathepsin G and lactoferrin were the major target antigens. However, some ANCA-positive sera did not recognize either of them. The present study was to investigate the unknown target antigens of ANCA in patients with SLE and their clinical significance.
  
  
  METHODS
  Sera were collected from 72 patients with SLE. ANCA were detected in both indirect immunofluorescence and antigen-specific enzyme-linked immunosorbent assay (ELISA). Mixed neutrophil granules were separated from normal human peripheral neutrophils; soluble acid extracts in non-reducing conditions were used as antigens in western blot analysis to detect ANCA.
  
  
  RESULTS
  SLE sera could blot a few bands. Interestingly, 14/72 (19.4%) sera recognized a novel 69 kDa protein band and 10/72 (13.9%) sera recognized the 55 kDa protein band, which might be bactericidal/permeability-increasing protein (BPI). The 69 kDa target antigen was different from the known target ANCA antigens such as cathepsin G and lactoferrin. Further study revealed that the percentages of patients with photosensitivity and oral ulcer in the anti-69 kDa autoantibodies-positive group were significantly higher than those in the anti-69 kDa autoantibodies-negative group (57.1%vs 10.3%, P < 0.005 and 50.0%vs 12.1%, P < 0.05, respectively).
  
  
  CONCLUSIONS
  A 69 kDa protein in human neutrophil granules was identified as a novel target antigen of ANCA in patients with SLE. The anti-69 kDa autoantibodies might be associated with photosensitivity and oral ulcer in patients with SLE.
authors.affiliation: Renal Division and Institute of Nephrology, Peking University First Hospital, Beijing, China.
authors.forename: Min
authors.initials: M
authors.lastname: Chen
authors.forename: Ming-Hui
authors.initials: MH
authors.lastname: Zhao
authors.forename: You-Kang
authors.initials: YK
authors.lastname: Zhang
authors.forename: Hai-Yan
authors.initials: HY
authors.lastname: Wang
mesh_terms: D000293:Adolescent; D000328:Adult; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000097:blood / Q000276:immunology*; D000918:Antibody Specificity; D001324:Autoantigens / Q000737:chemistry / Q000276:immunology*; D015153:Blotting, Western; D003594:Cytoplasmic Granules / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D008970:Molecular Weight; D009504:Neutrophils / Q000276:immunology*
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic; D001324:Autoantigens; D000939:Epitopes