Polymorphisms in genes coding for mediators in the interleukin cascade and their effect on susceptibility to sarcoidosis in the Slovenian population.

Sarcoidosis is a chronic inflammatory disease characterised by granulomatous inflammation in various organs. As genetic factors have been implicated in its aetiology, in our study we investigated whether the promotor polymorphisms in three genes coding for inflammatory mediators interleukin-6 (IL-6), interleukin-12 (IL-12), and interleukin-18 (IL-18) could be associated with susceptibility to sarcoidosis. The study sample consisted of 104 patients with sarcoidosis and 100 healthy control subjects. Following DNA isolation from peripheral blood the IL-6/-174G>C single nucleotide polymorphism (SNP), the IL-12B/4 bp insertion polymorphism, and the IL-18/-137G>C SNP were characterised by polymerase chain reaction. Our results showed an increased frequency of IL-6/-174C allele (p<0.01, OR=2.05, 95% CI=1.32-3.16), and also an increased genotype frequency of IL-6/-174 CC and CG carriers (p<0.01, OR=2.78, 95% CI=1.49-5.19) among sarcoidosis patients in comparison with healthy controls. Allele and genotype frequencies did not differ significantly between cases and controls for either the IL-12B/4 bp insertion polymorphism or for the IL-18/-137G>C polymorphism. In conclusion, we demonstrated that the -174G>C promotor polymorphism in the IL-6 gene may be a risk factor for sarcoidosis.