CTLA-4 gene 49A/G polymorphism in Turkish patients with Behçet's disease

Genetic factors predisposing individuals to Behçet's disease (BD) are considered to play important roles in the development of the disease. Patients with BD exhibit elevated levels of pro-inflammatory cytokines, and affected organs show a significant neutrophil and lymphocyte infiltration. Current evidence suggests that the activated lymphocytes contribute to neutrophil and endothelial cell activation in these patients. The cytotoxic T lymphocyte-associated antigen (CTLA)-4 molecule plays an important role in immune regulation by downregulating T-cell activation, and the CTLA-4 49A/G polymorphism in the exon 1 has been shown to be associated with a number of autoimmune diseases. In an attempt to demonstrate whether there is an association of the CTLA-4 49A/G polymorphism with BD in the Turkish population, we genotyped 59 Turkish patients and 99 healthy individuals for single-nucleotide polymorphisms. For this purpose, genomic DNA was obtained from the peripheral blood of individuals and the region of interest was amplified using PCR. Genotyping was performed using the BbvI restriction endonuclease. It was shown that the distribution of the CTLA-4 exon 1 49A/G allele and genotype frequencies did not differ between patients with BD and healthy controls. However, allele and genotype frequencies of CTLA-4 49 A and A/A were significantly higher in patients with ocular involvement compared with patients without these symptoms (90.6% vs. 65.1%, odds ratio (OR) = 9.67, P = 0.011; and 81.25% vs. 39.5%, OR = 9.56, P = 0.015, respectively). A statistically significant difference in the A allele frequency was observed in patients with erythema nodosum-like lesions (86.1% vs. 65.8%, OR = 6.24, P = 0.04). There was also an increase in A/A genotype frequency, but the difference was not statistically significant (72.2% vs. 41.5%, OR = 6.5, P = 0.068). Our data suggest that BD patients with ocular involvement and erythema nodosum-like lesions have a higher frequency of both the A allele and the A/A genotype at position 49 of exon 1 of CTLA-4. These results may also indicate that CTLA-4 is a disease-modifying rather than a susceptibility gene for BD.