IL-17A and IL-17F gene expression is strongly induced in the mucosa of H. pylori-infected subjects from Kenya and Germany.

Helicobacter pylori infection is the major cause of gastritis. Immunologically, H. pylori gastritis is associated with an infiltration of immune cells into gastric mucosa and the upregulation of various cytokines. Here, we analysed the gene expression of IL-1- and IL-17-related cytokines in regard to H. pylori infection in 85 German and 51 Kenyan patients with reflux-related or dyspeptic symptoms, respectively. Degree of gastritis and density of colonization were assessed histologically in accordance with the updated Sydney classification. Gene expression levels of cytokines IL-1β, IL-8, IL-18, IL-33, IL-17A, IL-17F and IL-23 as well as IL-23R were analysed by real-time RT-PCR. In both populations, H. pylori-infected individuals had significant higher inflammatory scores for activity and chronicity than H. pylori-negative subjects (P values between 0.006 and <0.0001). IL-8 mRNA was induced up to 6-fold in H. pylori-infected patients (P < 0.05), while the expression levels of IL-1β, IL-18, IL-23, IL-33 and IL-23R did not differ with respect to the H. pylori status in both groups. Most strikingly, a significant induction of both IL-17A and IL-17F was noted in H. pylori-infected individuals of both ethnic groups. Almost all IL-17F-positive samples revealed co-expression of IL-17A (40/42, 95.2%). Analysing IL-17A and IL-17F transcript levels of these 40 'double-positive' samples, a highly significant positive correlation between both genes was identified (P < 0.001). Taken together, H. pylori infection leads to a strong upregulation of both IL-17A and IL-17F in the gastric mucosa suggesting a regulatory link between both genes.