Introduction: Cytotoxic T-lymphocyte antigen 4 (CTLA-4) is a costimulatory molecule expressed by activated T cells. This study was performed to investigate the allele and genotype frequencies of CTLA4 gene polymorphisms in Iranian patients with ankylosing spondylitis (AS).
Methods: One hundred and fifty-seven patients with AS and 103 controls were included in this study. Polymorphisms of CTLA4 gene at positions +49 (in exon 1), -318, and -1,147 (in the promoter region) were studied on the genomic DNA using PCR restriction fragment-length polymorphism method.
Results: The frequencies of the T allele at position -1147 in the patients with AS was significantly increased in comparison with the control group (11% vs. 5%, P = 0.004); whereas the frequencies of C allele at the same position were significantly decreased in the patient group (89% vs. 95%, P = 0.004). Comparison of genotype frequencies at this position showed that the frequency of CT genotype in comparison with other genotypes was overrepresented in the patient group (20% vs. 8%, P = 0.012), while the CC genotype in comparison with other genotypes was decreased (79% vs. 91%, P = 0.012). There was no significant difference on frequencies of genotypes at the positions -318 and +49.
Conclusion: This study could suggest an association between specific allele in the promoter region of CTLA4 gene and AS disease.