Light microscopic and ultrastructural evidence of in vivo phagocytosis of Helicobacter pylori by neutrophils

Helicobacter pylori is believed to cause chronic active gastritis. Infection/colonization of the gastric mucosal surface induces a mucosal inflammatory reaction in the form of lymphocytic aggregates, plasma cells and, particularly, neutrophils, which may, in turn, damage the mucosal epithelium. In vitro studies demonstrate that, in culture, the bacilli are readily phagocytosed by neutrophils, this evoking a neutrophilic oxidative burst. However, it has been claimed that neutrophils do not phagocytose H. pylori in vivo. In this study of 19 endoscopic biopsies of gastric mucosa with H. pylori-associated gastritis, Cresyl violet staining for light microscopy and electron microscopy are used to demonstrate that, in vivo, neutrophils actively phagocytose and destroy the bacilli in the epithelial intercellular space and in the mucin on the surface of the mucosa. Direct contact of neutrophils with H. pylori was observed in 17 of 17 cases by light microscopy and in 4 of 15 cases by electron microscopy. Phagocytosis by neutrophils was seen in 14 of 17 cases by light microscopy and in 3 of 15 cases by electron microscopy. It was most evident in the surface mucus coat where 'wolf packs' of neutrophils were seen attacking the microbes. Ultrastructurally, neutrophil phagolysosomes contained both intact and partially digested bacteria, convincing evidence that the primary function of neutrophils in chronic active gastritis is to destroy H. pylori organisms. This study leaves open the question of whether, or how, neutrophils damage the gastric mucosa.