Association studies of interleukin-8 gene in Graves' disease and Graves' ophthalmopathy

Graves' disease (GD) is an autoimmune disorder, and the most common extrathyroidal manifestation is Graves' ophthalmopathy (GO), which is believed to be caused by a complex interaction between genetic and environmental factors. Many studies have reported that interleukin-8 (IL-8), a potent pro-inflammatory cytokine, is associated with many autoimmune diseases and could increase the degree of lymphocyte infiltration within the thyroid gland. The aim of the present study is to elucidate whether IL-8 is associated with the development of GD and GO. The serum concentration of IL-8 was tested in 39 primary GD patients, 43 treated active GO patients, and 24 healthy controls. We also performed an association study with the IL-8 gene polymorphism rs2227306 between 642 patients and 648 healthy controls in Chinese population. Our data showed that the expression level of IL-8 was associated with the development of GD, and the C-allele frequency of SNP rs2227306 was significantly higher in GD and GO patients compared with healthy controls. These results suggest that IL-8 is strongly associated with GD and GD.