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IL18 polymorphism is associated with an increased risk of Crohn's disease
Kazuo Tamura1, Yoshihiro Fukuda, Hiroko Sashio
1Laboratory of Hereditary Tumor, Institute for Advanced Medical Sciences, Hyogo College of Medicine, 1-1, Mukogawa-cho, Nishinomiya 663-8501, Japan.
Background:
The etiology of inflammatory bowel disease, which includes ulcerative colitis and Crohn's disease, has not yet been made clear. However, inflammatory bowel disease is recognized as a multifactorial disease, and innate genetic factors might contribute to the pathogenesis. Cytokine genes are thought to be important in inflammatory bowel disease. Recently, interleukin 18, cloned as a novel proinflammatory cytokine, has been implicated in inflammatory bowel disease, especially Crohn's disease.
Methods:
To identify germline mutations in patients with inflammatory bowel disease, the entire coding region of IL18 was examined using a DNA sequencing procedure.
Results:
No functional mutations were found, but a novel single nucleotide polymorphism (SNP) was identified as TCA/TCC at codon 35. In patients with Crohn's disease, the frequency of TCC allele carriers was significantly higher than in healthy controls (chi2 = 9.35, P = 0.002229, OR = 2.58, 95% CI = 1.39-4.80). Also, the magnitude of the association was more remarkable in females (chi2 = 16.36, P = 0.000052, OR = 8.17, 95% CI = 2.73-24.41). The TCC allele at codon 35 of IL18 may increase the risk for Crohn's disease, especially in females.
Conclusions:
IL18 is probably one of several genes that determine susceptibility to Crohn's disease.