MAGE-B2 autoantibody: a new biomarker for pediatric systemic lupus erythematosus.
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.
Hoftman
Alice D C
AD
Division of Allergy, Immunology, and Rheumatology, Department of Pediatrics, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA.
Tai
Lei-Qian
LQ
Tze
Sheila
S
Seligson
David
D
Gatti
Richard A
RA
McCurdy
Deborah K
DK
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
D000951:Antigens, Neoplasm; D001323:Autoantibodies; D015415:Biomarkers; C072012:MAGEB2 protein, human; D009363:Neoplasm Proteins