Gastric expression of IL-17A and IFNγ in Helicobacter pylori infected individuals is related to symptoms

Background: Chronic infection with Helicobacter pylori leads to gastritis and in a subpopulation of infected individuals to ulcers and cancer. Bacterial virulence factors and host immune inflammatory responses are risk factors related to disease. CD4⁺ T cells secrete cytokines that promote inflammation and an anti-bacterial response in the gastric mucosa during infection. The aim of the study was to investigate the pattern of expression of CD4⁺ T cell derived cytokines, IL-17A and IFNγ in paired antrum and corpus biopsies and correlate it to H. pylori infection outcome.

Methods: Gene and protein expression of IL-17A and IFNγ was analyzed in gastric biopsies from H. pylori infected subjects with non-ulcer dyspepsia (NUD) or gastric ulcer; and for comparison uninfected individuals.

Results: Upregulation of IL-17A and IFNγ gene expression was seen in corpus and antrum biopsies of H. pylori infected individuals with NUD compared to in uninfected controls. The expression of these cytokines correlated significantly with each other. Immunofluorescence staining revealed increased frequencies of IL-17A⁺ and IFNγ⁺ cells in antrum biopsies of gastric ulcer patients compared to of H. pylori infected NUD individuals; positive cells were not detected in any of the biopsies of uninfected controls. The frequencies of IFNγ and IL-17A⁺ cells correlated positively with inflammation in the antrum, but not the corpus, of H. pylori infected individuals. In the antrum, while there was no significant evidence of correlation between IFNγ and bacterial score, a positive correlation between bacterial score and IL-17A⁺ cells was seen.

Conclusions: In H. pylori infected individuals, the frequencies of IFNγ and IL-17A⁺ cells were increased in the antrum, particularly in patients with H. pylori induced gastric ulcers. Even though H. pylori colonized both the corpus and antrum regions of the stomach, the cytokine responses and subsequent pathology were mainly detected in the antrum.