Interleukin 10 in Helicobacter pylori associated gastritis: immunohistochemical localisation and in vitro effects on cytokine secretion

Background/Aims-Interleukin 10 (IL-10) is a counterinflammatory peptide imp licated in the downregulation of human intestinal immune responses. Enhance d secretion of IL-10 has been documented in gastric biopsy organ culture in Helicobacter pylori infection. This study aimed to define the cellular ori gins of IL-10 in H pylori associated gastritis, and to determine the effect s of endogenous IL-10 on proinflammatory cytokine secretion in vitro. Methods-Endoscopic biopsies were obtained from the gastric antrum at endosc opy from patients with dyspepsia. Two pairs of antral biopsies were culture d in vitro for 24 hours, one pair in the presence of neutralising anti-IL-1 0 monoclonal antibody, the other pair as controls. The cytokine content of culture supernatants (tumour necrosis factor alpha (TNF-alpha), IL-6, and I L-g) was determined by enzyme Inked immunosorbent assay and corrected for b iopsy weight. Helicobacter pylori status was established by histology and b iopsy urease test, and histopathology graded by the Sydney system. In a sub group of patients, western blotting was used to establish CagA serological status. Immunohistochemistry for IL-10 was performed on formalin fixed tiss ues using a combination of microwave antigen retrieval and the indirect avi din-biotin technique. Immunoreactivity was scored semiquantitatively. Results-In vitro culture was performed in 41 patients: 31 with H pylori pos itive chronic gastritis and 10 H pylori negative. In vitro secretion of TNF -alpha, IL-6, and IL-8 for "control" biopsies was significantly higher in H pylori positive versus negative samples, with values of TNF-alpha and IL-6 correlating with the degree of active and chronic inflammation and being h igher in CagA seropositive cases. No evidence for enhanced cytokine secreti on was seen in biopsies cocultured in the presence of anti-IL-10 monoclonal antibody. Immunohistochemistry was performed in 29 patients, of whom 13 we re H pylori positive. IL-10 immunoreactivity was observed in the surface ep ithelium in all H pylori positive cases and in 13 of 16 negative cases, esp ecially in areas of surface epithelial degeneration. Lamina propria mononuc lear cells (LPMNCs) were positively stained in all H pylori positive cases and in 12 of 16 negative cases, with a significantly greater proportion of positive LPMNCs in the positive group. Conclusions-This study localised IL-10 protein to the gastric epithelium an d LPMNCs. In vitro proinflammatory cytokine secretion was increased in H py lori infection (especially CagA positive infection), but blocking endogenou s IL-10 secretion did not significantly increase cytokine secretion. IL-10 is implicated in H pylori infection and might "damp down" local inflammatio n. The role of gastric IL-10 secretion in determining the clinicopathologic al outcome of infection merits further study.