Cytokines, cytokine gene polymorphisms and Helicobacter pylori infection: friend or foe?

Helicobacter pylori (H. pylori) is a flagellated, spiral-shaped, microaerophilic Gram-negative bacillus that colonises the gastric mucosa of more than 50% of the human population. Infection is a risk factor for gastritis, ulcer disease and stomach cancer. Immunity against H. pylori is mainly related to Th1/Th17 skewing, and the activation of regulatory T cells is the main strategy used to limit inflammatory responses, which can result in the pathogen persistence and can lead to chronic gastrointestinal diseases, including cancer. Furthermore, host genetic factors that affect cytokines may determine differences in the susceptibility to many diseases. In this review, we present the cytokine profiles and the main cytokine gene polymorphisms associated with resistance/susceptibility to H. pylori and discuss how such polymorphisms may influence infection/disease outcomes.