Association of T Helper 1 Cytokine Gene Single Nucleotide Polymorphisms with Ulcerative Colitis and Crohn’s Disease

Abstract

Background: Inflammatory bowel disease (IBD) mostly comprised of Crohn’s disease (CD) and ulcerative colitis (UC) is a condition arising from the combined effects of genetic, environmental, and immunological factors. IBD is associated with inflammation and altered cytokine profile. Objective: This study was aimed at assessing the association between T helper type 1 (Th1) cytokine polymorphisms (interferon gamma [IFN-γ] +874 A/T, interleukin-12 [IL-12] –1188 A/C, IL-2 –330 G/T, IL-2 +166 G/T) and susceptibility to and clinical features of IBD. Methods: The study population was composed of 75 IBD patients (40 CD patients and 35 UC patients) and 140 healthy controls. Genotyping was performed using polymerase chain reaction with sequence-specific primers. Results: The A allele of IFN-γ +874 polymorphism was overrepresented in the whole population of patients with IBD (OR 1.63; 95% CI 1.08–2.47; p = 0.020) and as well in the subpopulation of patients with CD (OR 2.14; 95% CI 1.26–3.63; p = 0.004), but not in UC. Multiple pairwise comparisons indicated that genotypes of single nucleotide polymorphisms (SNPs) within the IL-2 and IFN-γ genes are correlated with IBD, CD, and UC, while neither allele nor genotype frequency of th1 IL-12 –1188 polymorphism was associated with IBD, CD, or UC. Haplotype analysis also revealed that the presence of IL-2 –330/+166 TG haplotype versus the remaining haplotypes (GG, TT, and GT) is a protective factor against IBD (OR 0.62; p = 0.046). Conclusions: The present study reports (for the first time) significant associations between SNPs within the IFN-γ and IL-2 genes and IBD.