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Background: Helicobacter pylori-induced gastric inflammation is thought to be largely regulated by cytokines., Patients and Methods: The expression of interferon-gamma, interleukin-12, interleukin-4, interleukin-10, interleukin-8, and interleukin-17 mRNA was examined on gastric mucosal samples from 24 children by semiquantitative reverse transcription polymerase chain reaction and southern blotting. Biopsy-based tests, serology, and urea 13C breath test were used to assess Helicobacter pylori status. Gastric biopsies were also evaluated for bacterial density, chronic inflammation, and acute inflammatory activity., Results: Interferon-gamma, interleukin-12, interleukin-8 and interleukin-17 expression was higher in Helicobacter pylori-infected (n=13) than uninfected (n=11) children. Conversely, interleukin-4 and interleukin-10 expression did not differ between Helicobacter pylori-infected and uninfected children. In Helicobacter pylori-infected children, interferon-gamma, interleukin-12, interleukin-8 and interleukin-17 expression correlated with bacterial density, and Interferon-gamma and interleukin-12 expression with chronic inflammation score., Conclusions: The findings of this study indicate that, in children, Helicobacter pylori-induced inflammatory response would favour production of proinflammatory cytokines and development of cell-mediated immunity, namely Th1 response.

Transcripts for interleukin (IL) 15 were detected in the gastric mucosal samples of 5/5 (100%) patients with no evidence of Helicobacter pylori infection and in 4/14 (28%) H. pylori-infected patients (P< 0.05). Both IL-15 mRNA and IL-15 protein were detected in 1/6 (17%) patients who successfully underwent H. pylori eradication therapy, before treatment and in 5/6 (83%) cases after eradication. Even though a parallel significant (P < 0.03) improvement of gastritis score occurred after eradication, the severity of gastritis did not differ according to the mucosal IL-15 expression among H. pylori-infected patients, irrespective of the CagA serology. This study demonstrates, for the first time, that transcripts for IL-15 are expressed in the human gastric mucosa. Changes occurring during H. pylori colonisation and after eradication raise the hypothesis that H. pylori may down-regulate IL-15 expression in the gastric mucosa.