Diagram 3: The protective mucus layer of the stomach

H. pylori make an enzyme called urease, which
degrades urea to produce bicarbonate and ammonia. The
ammonia neutralises the acid in the area, increasing the
pH in the mucus to about seven. But the ammonia is also
toxic to the cells lining the stomach and, along with other
toxins made by the bacteria, causes the cells to become
inflamed or to die. Inflammation is caused by the body's
immune system trying to defend itself against invasion
by the bacteria.