title: MAGE-B2 autoantibody: a new biomarker for pediatric systemic lupus erythematosus.
abstract: OBJECTIVE
  Melanoma-associated antigen gene B2 (MAGE-B2) encodes an embryonic antigen normally silenced after birth except in testis and placenta. We identified the MAGE-B2 gene and autoantibodies in pediatric patients with systemic lupus erythematosus (SLE) glomerulonephritis. We investigated the prevalence of MAGE-B2 autoantibodies in association with active SLE, to determine a pathogenetic role of MAGE-B2 protein through its distribution in cells and tissues.
  
  
  METHODS
  A cross-sectional study analyzed the frequency of MAGE-B2 autoantibodies in 40 patients with pediatric SLE, 23 adult controls, and 16 patients with pediatric juvenile rheumatoid arthritis (JRA) using Western blots containing recombinant MAGE-B2. SLE Disease Activity Index 2000 (SLEDAI-2K) and British Isles Lupus Assessment Group (BILAG) index measured SLE disease activity. Tissue distribution of MAGE-B2 protein was assessed by immunohistochemistry, immunofluorescence, and Western blots.
  
  
  RESULTS
  Seventeen (43%) of 40 pediatric SLE patients had MAGE-B2 autoantibodies as compared to 0 of 16 JRA patients and 2 of 23 adult controls. SLE disease activity was significantly higher in MAGE-B2 autoantibody-positive versus autoantibody-negative patients (SLEDAI-2K, mean 10.9 vs 5.2, p = 0.013; BILAG, mean 15.3 vs 6.3, p = 0.023). Active nephritis was more prevalent (60% vs 24%) in MAGE-B2 autoantibody-positive than autoantibody-negative SLE patients. MAGE-B2 protein was visualized in SLE kidney proximal convoluted tubules and in tumor epithelial cells, but not in lymphoblastoid cells.
  
  
  CONCLUSIONS
  MAGE-B2 autoantibody appears to be a clinically relevant biomarker for pediatric SLE disease activity and nephritis.
authors.affiliation: Division of Allergy, Immunology, and Rheumatology, Department of Pediatrics, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA.
authors.forename: Alice D C
authors.initials: AD
authors.lastname: Hoftman
authors.forename: Lei-Qian
authors.initials: LQ
authors.lastname: Tai
authors.forename: Sheila
authors.initials: S
authors.lastname: Tze
authors.forename: David
authors.initials: D
authors.lastname: Seligson
authors.forename: Richard A
authors.initials: RA
authors.lastname: Gatti
authors.forename: Deborah K
authors.initials: DK
authors.lastname: McCurdy
mesh_terms: D000293:Adolescent; D000951:Antigens, Neoplasm / Q000276:immunology*; D001171:Arthritis, Juvenile / Q000276:immunology; D001323:Autoantibodies / Q000276:immunology*; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008181:Lupus Nephritis / Q000276:immunology*; D008297:Male; D009363:Neoplasm Proteins / Q000276:immunology*; D012720:Severity of Illness Index; D055815:Young Adult
chemical_list: D000951:Antigens, Neoplasm; D001323:Autoantibodies; D015415:Biomarkers; C072012:MAGEB2 protein, human; D009363:Neoplasm Proteins