Helicobacter pylori are Gram-negative, microaerophilic bacteria that can inhabit various areas of the stomach, particularly the antrum. It is one of the most common bacterial infections in the world, and leads to chronic inflammation of the stomach.

These bacteria cause a chronic low-level rubor of the stomach lining, and are strongly linked to the development of duodenal and gastric ulcers and stomach cancer. As the symptoms of stomach carcinomas are varied, they are often discovered at a late stage and have a very poor prognosis. Over 80% of individuals infected with H. pylori are generally symptom-free.

Natural killer (NK) cells, a type of immune cell, can both recognize and kill cells that are infected by viruses and bacteria as well as tumor cells. They kill cells by releasing small cytoplasmic granules of proteins called perforin and granzyme that cause the target cell to die by apoptosis.

A team of scientists at the University of Gothenburg (Gothenburg, Sweden) examined how NK cells reacted to H. pylori. They found that a special type of NK cells was active against the stomach ulcer bacterium and the NK cells produced cytokines, which are the immune system's signal substances and act as a defense against the intruder.

Gastric or stomach cancer is a malignant tumor in the mucous membrane of the stomach, and is one of the more common forms of cancer in Sweden. There are about 24,000 new cases of this disease diagnosed annually in the USA.

Asa Lindgren, Ph.D., who wrote her doctoral thesis on the subject, suggests that NK cells can play an important role in the immune defense against H. pylori. Previously it was shown that a high proportion of NK cells in tumor tissue have contributed to a better prognosis and longer survival for patients with stomach cancer, as these cells help to eliminate the tumor cells.

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University of Gothenburg