Cytotoxic T lymphocyte antigen-4 gene polymorphisms and susceptibility to type 1 autoimmune hepatitis in the Tunisian population

Genetic factors and gene polymorphisms leading to the onset of autoimmune response in autoimmune hepatitis(AIH)are still not full elucidated.Since the CTLA-4 molecule is a key modulator of the lymphocytes responses we hypothezied that deficiencies or mutations in the gene encoding CTLA4 protein may be involved in AIH susceptibility and trigger the autoimmune response.We investigated 3 distinct polymorphic sites(t49A>G,CT60 G>A and e318C>T)of the CTLA4 gene in 50 AIH patients and 100 healthy controls using the KASP genotyping technology.A significant positive association with AIH susceptibility was found for the GG genotype in t49 position of the CTLA4 gene which was significantly higher in AIH patients compared to controls(28%vs 9%,pZ0.003,ORZ3.93[1.56e9.88]).The CTLA4 A/A genotype in position CT60 was more significantly frequent in controls comparing to AIH patients and could be considered as a protective genotype for the tunisian patients.CTLA4 genotyping in position318 did not show any statistically significant difference in genotype or allele distribution.The CTLA4 gene polymorphism in position t49 is associated to AIH susceptibility in the Tunisian population.Mutation in the CTLA4 gene may lead to a modification of the CTLA4 protein structure that could have functional relevance in AIH pathogenesis and onset.