Cytokine gene polymorphisms of TNFα, IL-6, IL-10, TGFβ and IFNγ in the Saudi population

Studies have demonstrated associations between cytokine gene polymorphisms and ethnicity. In the present work the authors examine polymorphisms in the genes encoding interleukin-6 (IL-6), IL-10, interferon-gamma (IFNgamma), tumour necrosis factor-alpha (TNFalpha) and transforming growth factor-beta (TGFbeta1) using the polymerase chain reaction sequence-specific primer (PCR-SSP) method in 150 healthy unrelated Saudis, and results compared with those from other studied populations. The genotype distributions were consistent with the Hardy-Weinberg equilibrium, and the genotype frequencies observed among Saudis showed both similarity and difference to other populations. The most notable difference was in the distribution of IL-6, where the Saudi population showed a lower CG genotype frequency compared with White American (22% vs. 39.2%, P = 0.004), Italian (22% vs. 50%, P < 0.0001) and Brazilian (22% vs. 40.8%, P < 0.0001) populations. The study population also showed a higher frequency of the IL-6 GG genotype compared with White Americans (72% vs. 45.1%, P < 0.0001), Italians (72% vs. 41%, P < 0.0001) and Brazilians (72% vs. 49.3%, P < 0.0001). These results may have significant clinical relevance to the understanding of prevalent diseases in Saudi Arabia.