Polymorphisms in Turkish population

Akdeniz University Teknocity, Kampus Antalya, Turkey.

Cytotoxic T lymphocyte-associated antigen-4 is a cell-surface molecule providing a negative signal for T cell activation. CTLA-4 gene polymorphisms are known to be related with genetic susceptibility to various autoimmune diseases, including systemic lupus erythematosus (SLE). However, the effects of this polymorphism on clinical features of SLE have not been defined. We analysed the CTLA-4 gene +49 A/G polymorphisms in patients with SLE by using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and investigated the effect of polymorphisms on clinical outcomes. Blood was collected from 47 unrelated Turkish SLE patients, all fulfilling the American College of Rheumatology criteria for SLE, and 100 ethnically matched healthy volunteers. The AA genotype was a predominant genotype in the Turkish population and genotype frequencies of CTLA-4 AA were significantly higher in SLE patients (70%) than healthy controls (47%) (P = 0.015). There was a statistically significant difference in the AA genotype [odds ratio (OR): 2.66, confidence interval (CI) 95%: 1.27-5.56, P = 0.014] distribution among patients and controls. There was also an increase in A allele frequency in SLE and controls, but the difference was not statistically significant (81% vs. 70%, P = 0.068, OR = 1.8, CI 95%: 0.99-3.28). Interestingly, mean age and mean age of onset disease was higher in AA homozygote SLE patients compared to non-AA (39.2 +/- 11.5 vs. 31.6 +/- 10.6, P = 0.044; 32.38 vs. 24.31, P = 0.046, respectively). There was no association between genotype and the other clinical features of SLE. Our results suggested that CTLA-4 +49 AA genotype might be a risk factor for the development of SLE in Turkish population and G allele might be involved in early development of SLE. No association with clinical features was found for polymorphism of the promoter region in CTLA-4 +49.

Department of Endocrinology and Metabolic Diseases Department, Ankara University School of Medicine, Ibni Sina Hospital, Ankara, Turkey. drsahinmustafa@yahoo.com

We previously shown that in a Turkish population, the A/G polymorphism in exon 1 of the cytotoxic T cell lymphocyte-associated molecule-4 (CTLA-4) gene is associated with Graves’ disease, and that the G allele may contribute to susceptibility for developing Graves’ disease. This polymorphism was identified in 197 patients with Hashimoto thyroiditis (HT) (126 women, 71 men; aged, 42.92 +/- 13.4 years) and 98 healthy individuals (56 women, 21 men; aged, 42.27 +/- 13.43 years) in Turkish population. Polymorphisms were analysed using a polymerase chain reaction-restriction fragment length polymorphism method. Frequency of the A/G genotypes was not significantly different in patients with HT when compared with controls in both sexes (P > 0.05). There was no statistical difference in age, sex, cigarette smoking, initial serum thyroid hormone levels, initial goiter size and thyroid autoantibodies among the patients with the three different genotypes (G/G, A/G and A/A). We concluded that A/G polymorphism of CTLA molecule is linked to occurrence of Graves’ disease bu not to HT in the Turkish population.