How Ulcer Bacteria Cause Disease NEW YORK (Reuters) -- A new study shows how the bacteria Helicobacter pylori (H. pylori) can lead to ulcers and stomach cancer, and may help scientists learn how other bacteria cause disease. The study is reported in the Proceedings of the National Academy of Sciences. Half of the people in the world are infected with H. pylori, though most have few symptoms and may live with the bug for decades. But 10% to 20% of infected individuals will eventually develop ulcers or inflammation of the stomach, and 30% to 90% of stomach cancers are tied to H. pylori. In the study, Dr. Jeffrey I. Gordon from Washington University School of Medicine in St. Louis, Missouri, and colleagues inserted a human gene called Lewis b (Leb) into the stomach cells of mice and then infected the mice with H. pylori. The researchers discovered that the bacteria attached to the stomach linings of mice with Leb but not those without Leb, where the bug went into gastric mucus. When H. pylori went onto the stomach lining, the mice with Leb made antibodies to attack the bacteria. But the antibodies were similar to other cells already in the mice, so the animals' immune systems began to attack those cells as well as the bacteria. This caused an inflammatory response similar to chronic active gastritis found in people who have an active H. pylori infection. "This is a rather extraordinary example of a bacterium that can be relatively harmless in some people and cause cancer in others," Gordon said in a statement. "The challenge is to identify patients who are at risk for developing more serious disease." SOURCE: Proceedings of the National Academy of Sciences (1998;95:3925-3930)
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