Primary biliary cirrhosis is associated with a genetic variant in the 3' flanking region of the CTLA4 gene.
OBJECTIVE
Genetic variation is invoked as a strong component underlying primary biliary cirrhosis (PBC) and other autoimmune disorders. Data suggest that some of this genetic risk is shared, affecting function of the immune mechanisms controlling self-tolerance. Cytotoxic T-lymphocyte antigen 4 (CTLA4) encodes a coinhibitory immunoreceptor that is a key regulator of self-tolerance with established genetic associations to multiple autoimmune diseases but conflicting evidence of involvement with PBC. We aimed to perform a more comprehensive assessment of CTLA4 genetic variation in PBC using a haplotype-tagging based approach.


METHODS
Single nucleotide polymorphisms (SNPs) were genotyped in 402 PBC patients and 279 controls and evaluated for association with PBC and with antimitochondrial antibody (AMA) status and prior orthotopic liver transplantation (OLT) among the PBC patients, both individually and as inferred haplotypes, using logistic regression.


RESULTS
All SNPs were in Hardy-Weinberg equilibrium. We identified a novel and relatively strong association between PBC and rs231725, a SNP in the 3' flanking region of CTLA4 located outside of the area previously investigated in PBC. This SNP tags a common CTLA4 haplotype that contains a number of functionally implicated autoimmune CTLA4 SNPs, which was also found to be associated with PBC and to a lesser extent AMA status and prior OLT.


CONCLUSIONS
Our findings suggest that CTLA4 has an impact on the risk of PBC and possibly plays a role in influencing AMA development as well as progression to OLT among PBC patients. Replication in a suitable, independent PBC cohort is needed.
Juran
Brian D
BD
Center for Basic Research in Digestive Diseases, Division of Gastroenterology and Hepatology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.
Atkinson
Elizabeth J
EJ
Schlicht
Erik M
EM
Fridley
Brooke L
BL
Lazaridis
Konstantinos N
KN
D024509:3' Flanking Region / Q000235:genetics; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015703:Antigens, CD / Q000235:genetics*; D060908:CTLA-4 Antigen; D005260:Female; D020022:Genetic Predisposition to Disease / Q000453:epidemiology; D014644:Genetic Variation; D006239:Haplotypes; D006801:Humans; D008105:Liver Cirrhosis, Biliary / Q000453:epidemiology* / Q000235:genetics* / Q000601:surgery; D016031:Liver Transplantation / Q000706:statistics & numerical data; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide; D012307:Risk Factors
D015703:Antigens, CD; D060908:CTLA-4 Antigen; C556706:CTLA4 protein, human
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