Common cellular and diverse genetic basis of thymoma-associated myasthenia gravis: role of MHC class II and AIRE genes and genetic polymorphisms.
Generation of autoreactive CD4(+) effector T cells and defective production of regulatory CD4(+) T cells inside thymomas contribute to the development of myasthenia gravis (MG) in >90% of MG(+) thymomas. The molecular basis of these abnormalities is unknown. We report here that a) expression levels of class II major histocompatibility complex (MHCII) genes are variably decreased in thymomas, most prominently in histological WHO types A and AB; b) epithelial cells of type A and AB thymomas exhibit signal transducer and activator of transcription (STAT-1)-related defects of interferon-gamma (IFN-gamma) signaling and human leukocyte antigen (HLA)-DR expression in vitro; c) the promoter III (pIII)- and pIV-driven splice variants of the MHCII transactivator (CIITA) play a key role in MHCII gene expression in thymus and thymomas; and d) the pIV CIITA promoter is heavily methylated in thymomas. Recently, we also found that expression of the autoimmune regulator (AIRE) gene is absent from approximately 95% of thymomas. Among all theses abnormalities, only better preserved expression levels of MHCII (P < 0.001) in thymomas were significantly associated with the presence of MG. Taking the association of a gain-of-function polymorphism of the CTLA-4 and PTPN22 gene with MG in thymomas into account, we conclude that these acquired cellular abnormalities of the thymoma microenvironment in concert with inherited genetic high-risk polymorphisms of immunoregulatory genes have an impact on intratumorous thymopoiesis and appear to tip the balance toward central tolerance failure and development of MG. The findings imply that IFN-gamma and STAT-1 signaling play a role in MHCII expression in the human thymus and in the pathogenesis of paraneoplastic MG.
Institute of Pathology, University Hospital Mannheim, University of Heidelberg, Theodor-Kutzer-Ufer 1-3, 68135 Mannheim, Germany. philipp.stroebel@path.ma.uni-heidelberg.de
Philipp
P
Ströbel
Wen-Yu
WY
Chuang
Sergei
S
Chuvpilo
Andreas
A
Zettl
Tiemo
T
Katzenberger
Hubert
H
Kalbacher
Peter
P
Rieckmann
Wilfred
W
Nix
Berthold
B
Schalke
Ralf
R
Gold
Hans-Konrad
HK
Müller-Hermelink
Pärt
P
Peterson
Alexander
A
Marx
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D019175:DNA Methylation; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D000949:Histocompatibility Antigens Class II / Q000235:genetics* / Q000276:immunology*; D006801:Humans; D007223:Infant; D007371:Interferon-gamma / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000150:complications / Q000235:genetics* / Q000276:immunology* / Q000473:pathology; D011110:Polymorphism, Genetic / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D050794:STAT1 Transcription Factor / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013945:Thymoma / Q000209:etiology / Q000235:genetics* / Q000276:immunology* / Q000473:pathology; D014157:Transcription Factors / Q000235:genetics*; D000096927:AIRE Protein
D000949:Histocompatibility Antigens Class II; D007371:Interferon-gamma; D050794:STAT1 Transcription Factor; D014157:Transcription Factors; D000096927:AIRE Protein; C494079:STAT1 protein, human