Helicobacter pylori-Induced Ulceration of the Stomach and Intestines

Helicobacter pylori, by means of its flagella, is able to swim through the mucus layer of the stomach or intestines and adhere to the epithelial cells of the mucous membranes. Here the pH is near neutral. To also help protect the bacterium from the acid, H. pylori produces an acid-inhibitory protein that blocks acid secretion by surrounding parietal cells in the stomach. The bacterium then releases toxins that lead to excessive production of cytokines and chemokines, as well as mucinase and phospholipase that damage the gastric or intestinal mucosa. The cytokines and chemokines, in turn, result in a massive inflammatory response. Neutrophils leave the capillaries, accumulate at the area of infection, and discharge their lysosomes for extracellular killing. This not only kills the bacteria, it also destroys the mucus-secreting mucous membranes of the stomach. Without this protective layer, gastric acid causes ulceration of the stomach or intestines. (Note that H. pylori is actually a spiral-shaped bacteria with a lophotrichous arrangement of flagella but showing this in the animation is beyond my technical abilities.)

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