CTLA-4 +49A/G polymorphism is associated with Behçet's disease in a Tunisian population

The involvement of excessive T-helper cell functions in the pathogenesis of Behçet's disease (BD) has been reported. Cytotoxic T-lymphocyte antigen-4 (CTLA-4) plays a role in T-cell downregulation. In this report, we investigated the possible association between BD patients and the CTLA-4 +49A/G polymorphism in Tunisian population. A total of 135 Tunisian BD patients and 151 healthy blood donors from the same geographic area were genotyped by polymerase chain reaction for the CTLA-4 +49 A/G polymorphism. A highly significant difference between Tunisian BD patients and healthy controls was found regarding the distribution of CTLA-4 +49 A allele [P < 10(-7); chi(2) = 75.63; odds ratio (OR) = 4.63; 95% confidence interval (CI) = 3.20-6.72] and genotype frequencies (P < 10(-7); chi(2) = 71.02). Furthermore, in the BD group, the A allele was predominant in males (76.3%) when compared with females (62%), (P = 0.014; chi(2) = 5.97; OR = 1.99; 95% CI = 1.10-3.59). No relationship was found between the studied genotype and clinical manifestations. Our results show a gene dose effect of the A allele on the BD. The A allele exerts a stronger effect on disease susceptibility in males compared with females.