Objectives: Little information is available on the potential role of alpha-defensins derived from neutrophils during H. pylori infection, or the effect of H. pylori on the alpha-defensin release. The effects of H. pylori on human granulocytes were investigated in vitro by flow cytometry and ELISA. Additionally we sought to identify by immunohistochemistry the alpha-defensins within the gastric mucosa of patients infected with H. pylori.
Materials and methods: The intracellular expression of alpha-defensin in human granulocytes and in mononuclear cells was determined by flow cytometry. Induction of alpha-defensin release from granulocytes, mononuclear cells, or from whole blood cultures by H. pylori was detected by measuring the HNP1-3 (alpha-defensin) concentrations in the supernatants by ELISA. Immunohistochemistry was used to identify HNP1-3 in infiltrating neutrophils in the gastric mucosa of eight patients.
Results: A considerable intracellular alpha-defensin staining was observed in granulocytes. Stimulation of granulocytes with H. pylori resulted in a decrease in intracellular staining which was due to the extracellular release of alpha-defensin. In whole blood cultures H. pylori infection resulted in significantly high alpha-defensin concentrations (131623 +/- 13986 pg/ml), which were mainly due to the activity of the granulocytes with only a minor amount furnished by the mononuclear cells. In H. pylori-infected mucosa, infiltrating neutrophils showed intense immunostaining with anti-HNP1-3. The intensity of alpha-defensin staining varied parallel with the density of H. pylori in the biopsy samples.
Conclusions: H. pylori induce alpha-defensin release from granulocytes which may well be important in local host response to H. pylori infection in gastroduodenal diseases.