Objective: Interleukin-17A and interleukin-17F (IL-17A and IL-17F) are candidate genes for chronic inflammatory disease. We investigated the association between IL17A/F gene polymorphisms and susceptibility to and clinical features of inflammatory bowel disease (IBD).
Methods: A total of 270 ulcerative colitis (UC) patients, 82 Crohn's disease (CD) patients and 268 healthy controls were recruited in this study. Genomic DNA was extracted and analyzed for IL17A/F gene polymorphisms using ligase detection reaction allelic technology.
Results: Compared to the controls, the mutant allele C for IL17F rs763780 was significantly more common in CD patients [14.0 vs 8.4 %, P = 0.033, odds ratio (OR) 1.18, 95 % confidence interval (CI) 1.41-3.04] and was associated with the disease lesion location. This variant of IL17F rs763780 also had a weak correlation with the age of UC onset (P = 0.05, OR 0.97, 95 % CI 0.94-1.00). The IL17A (rs2275913, G-197A) variant had a weak association with the severity of disease: patients with the mutant allele A tended to suffer mild active UC. The haplotype (GGTT) of IL17A formed with four single nucleotide polymorphisms (rs2275913, rs8193037, rs8193038, and rs3804513) was associated with an increased risk of UC (P = 0.034, OR 4.58, 95 % CI 1.54-13.64).
Conclusions: The IL17F (rs763780, 7488T/C) variant was associated with an increased risk for the development of CD, and affected some clinical features of UC and CD. The IL17A (rs2275913, G-197A) variant had a weak association with the severity of UC. There was a risk haplotype in IL17A which could increase the risk of UC.