IL-6 promoter polymorphism (−174G/C) and systemic lupus erythematosus
We investigated the possible association between susceptibility to systemic lupus erythematosus (SLE) and single-nucleotide polymorphisms located in the promoter region of the interleukin-6 gene (−174 G/C) in a sample of the Egyptian population and the contribution of this polymorphism in the clinical or immunological manifestation of the disease. Forty-two Egyptian patients with SLE and 40 unrelated healthy control volunteers were genotyped by polymerase chain reaction followed by visualization on 4% agarose gel electrophoresis on ultraviolet transilluminator to detect the genotype distribution and allelic frequencies of the polymorphisms. The homozygous GG genotypes was significantly increased in SLE patients compared to control group (p value = 0.04). On the other hand, the heterozygous G/C genotype was significantly elevated in the controls compared to SLE patients (p value = 0.01). The odds ratio value for G/G was 2.6 with a 95% CI from 1.1 to 6.7. As regard the association of clinical manifestations to the genotype frequency, we found a statistical significant increase in the frequency of GG genotype with chest disease, nephritis, and arthritis. From this study, we suggest that G carrier is more susceptible to develop SLE and that SNP may have a role in the pathogenesis of the disease and may be associated with some of its clinical manifestations.