Interleukin-27 polymorphisms are associated with inflammatory bowel diseases in a Korean population

The cytokine interleukin (IL)-27 is composed of two subunits, Epstein-Barr virus-induced gene 3 (EBI3) and p28, and IL-27 is a novel IL-12 family member that mediates between the innate and adaptive immune systems. We previously identified four polymorphisms in the human IL-27 gene and we suggested that the polymorphism of IL-27 is associated with the susceptibility to asthma. IL-27 transcripts are significantly elevated in active Crohn's disease (CD) but not in ulcerative colitis (UC). To determine whether these IL-27 single nucleotide polymorphisms are associated with the susceptibility to inflammatory bowel disease (IBD), the genotype and allelic frequencies of the IL-27 polymorphisms were analyzed between the IBD patients and the healthy controls.

Genotype analysis of the IL-27 gene was performed by the single-base extension (SBE) method. The haplotype frequencies of IL-27 for multiple loci were estimated using the expectation maximization (EM) algorithm.

The genotype frequencies of the g.-964A > G polymorphism in the IBD patients were significantly different from those of the healthy control group (P = 0.001). In both the UC and CD patients, the genotype frequencies of the g.-964A > G polymorphism were also significantly different from the frequencies of the healthy control group (P = 0.009). The frequencies of the AGT and GGT haplotypes were significantly different between the healthy control group and the IBD patient group (P = 0.00004 and 0.021, respectively).

Our results suggest that the g.-964A > G polymorphism of the IL-27 gene located on the IBD1 locus might be associated with the susceptibility to IBD.