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Background/Aim: To investigate the possible association between the polymorphism of the CTLA-4 exon 1 +49 A/G and susceptibility to Crohn′s disease (CD) and ulcerative colitis (UC) in the Tunisian population. Methods: The +49 A/G dimorphism was analyzed in 119 patients with CD, 65 patients with UC, and 100 controls by the polymerase chain reaction-restriction fragment length polymorphism method. Results: Significantly higher frequencies of the CTLA-4 +49A allele and A/A homozygous individuals were observed in patients with CD when compared with controls (pc = 0.0023 and pc = 0.0003, respectively). Analysis of CTLA-4 A/G polymorphism with respect to sex in CD showed a significant difference in A/A genotypes between female patients and controls (pc = 0.0001 and pc = 0.038, respectively). There were no differences in the subgroups of patients with CD. Conclusions: Forty-nine A alleles and AA genotype are associated with CD susceptibility in Tunisians. Other genes involved in the T-cell regulation remain strong candidates for IBD susceptibility and require further investigation.

Aim: Interleukin (IL)-18 can regulate the Th2-mediated immune response and it may be involved in the pathogenesis of Th1 and Th2 chronic inflammatory diseases. This study sought to detect a possible association between two single nucleotide polymorphisms (SNPs) (-137G/C and -607C/A) in the IL-18 gene promoter region and susceptibility to inflammatory bowel disease (IBD) including Crohn's disease (CD) and ulcerative colitis (UC) in the Tunisian population. Methods: The (-137G/C and -607C/A) IL-18 polymorphism was analyzed in 105 patients with CD, 59 patients with UC, and 100 controls using the sequence-specific polymerase chain reaction method. Results: The distribution of allele and genotype frequencies illustrate that the -137G/G genotype frequency was significantly higher in UC than in controls (p value corrected (pc) = 0.038). On the other hand, we found a statistically significant association (pc = 0.033) between genotype AA of the IL-18 gene promoter (-607C/A) polymorphism in UC patients and the distal localization of the lesions. In CD, no significant differences were observed at positions -607 and -137. The analysis of IBD patients according to clinical behavior revealed no difference. Conclusion: The two SNPs at position -607 (C/A) and -137 (G/C) in the promoter region of the IL-18 gene was associated with the development of UC but not CD, providing a strong support for an IBD susceptibility gene in the region surrounding IL-18. It remains to be determined precisely how the IL-18 alleles influence the pathogenesis of IBD. Copyright © 2011 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]