Interleukin-18 single nucleotide polymorphisms contribute to the susceptibility to brucellosis in Iranian patients

It seems that IL-18 has a crucial role in immunity against Brucella infection. Since the expression of IL-18 can be affected by polymorphisms in its gene, we decided to investigate any probable relationship between the six different IL-18 gene polymorphisms and brucellosis. A total of 193 patients with brucellosis and 83 healthy farmers who consumed contaminated raw milk and dairy products from the animals with brucellosis, were included in this study. All the individuals were genotyped for six IL-18 polymorphisms at positions −656, −607, −137, +113, +127 and codon 35/3, using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The distributions of alleles for IL-18 polymorphisms at positions −137G/+113T/+127C/codon 35/3A (correlated with higher production of IL-18) were significantly higher in healthy controls than in patients (P = 0.012, 0.012, 0.012 and 0.0018, respectively). It could be suggested that individuals who inherited the aforementioned genotypes/alleles are able to produce higher levels of IL-18 at the onset of infection, and it leads to more IFN-gamma production and control Brucella infection before the emerging brucellosis.