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Pathophysiology of and immune response to Helicobacter pylori infection

Section Editor
Mark Feldman, MD, MACP, AGAF, FACG
Deputy Editor
Shilpa Grover, MD, MPH


Helicobacter pylori (H. pylori) is highly adapted to the gastric environment where it lives within or beneath the gastric mucous layer (see "Bacteriology and epidemiology of Helicobacter pylori infection"). The bacterium generally does not invade gastroduodenal tissue. Instead, it renders the underlying mucosa more vulnerable to acid peptic damage by disrupting the mucous layer, liberating enzymes and toxins, and adhering to the gastric epithelium. In addition, the host immune response to H. pylori incites an inflammatory reaction which further perpetuates tissue injury.

The chronic inflammation induced by H. pylori upsets gastric acid secretory physiology to varying degrees and leads to chronic gastritis which, in most individuals is asymptomatic and does not progress (picture 1A-B). In some cases, however, altered gastric secretion coupled with tissue injury leads to peptic ulcer disease, while in other cases, gastritis progresses to atrophy, intestinal metaplasia, and eventually gastric carcinoma or rarely, due to persistent immune stimulation of gastric lymphoid tissue, gastric lymphoma. (See "Association between Helicobacter pylori infection and duodenal ulcer" and "Acute and chronic gastritis due to Helicobacter pylori" and "Gastric intestinal metaplasia" and "Metaplastic (chronic) atrophic gastritis" and "Association between Helicobacter pylori infection and gastrointestinal malignancy".)

As a result, the pathophysiology of H. pylori infection and its eventual clinical outcome should be viewed as a complex interaction between the host and the bacterium. This interaction is influenced by the environment and modulated by a number of largely as yet unidentified factors [1,2].

The pathophysiology of H. pylori infection as it relates to gastrointestinal disease in general will be reviewed here. The role of H. pylori in specific disease processes is discussed separately. (See "Association between Helicobacter pylori infection and duodenal ulcer" and "Acute and chronic gastritis due to Helicobacter pylori" and "Association between Helicobacter pylori infection and gastrointestinal malignancy".)


Tissue injury induced by H. pylori depends upon bacterial attachment and the subsequent release of enzymes and other microbial products that can cause cellular damage.


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Literature review current through: Sep 2016. | This topic last updated: Oct 14, 2015.
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