Background: The Th2 cytokine IL-4 might limit H. pylori associated gastric inflammation and favour H. pylori clearance. The aim of the study was to verify whether IL-4 -588C>T SNP, or two SNPs of the gene coding the alpha chain of IL-4 receptor (IL-4RA Ex5+14A>G, IL-4RA Ex11+828A>G) considered singly or as haplotypes, are correlated with H. pylori virulence genes or H. pylori associated diseases.
Methods: We studied 144 patients with non-cardia gastric cancer (NCGC)(41/50 with present or past H. pylori infection), 75 with duodenal ulcer (DU)(66 H. pylori infected) and 171 with gastritis (CG)(107 H. pylori infected). cagA gene was present in 24/28 NCGC, 45/59 DU and 56/107 CG.
Results: All SNPs were in Hardy-Weinberg equilibrium. IL-4RA haplotypes frequencies were estimated using Arlequin software. Neither the SNPs nor the IL-4RA haplotype correlated with disease diagnosis, H. pylori infection, degree of mucosal inflammation or intestinal metaplasia. IL-4 -588T allele (OR=3.69, 95% CI:1.34-10.16) and IL-4RA GA haplotype (p<0.05) enhanced the risk for cagA positive infections. IL-4RA GA haplotype correlated with IL-4 protein levels in H. pylori infected gastric mucosa.
Conclusions: IL-4 and IL-4RA gene polymorphisms concur in selecting the H. pylori infecting strain, probably influencing the IL-4 signalling pathway.