HELICOBACTER PYLORI AND THE FORMATION OF AUTO-ANTIBODIES
H. pylori infection can lead to the production of auto-antibodies, which are antibodies directed against the infected person’s own cells. This can occur if the antibody produced in response to the H. pylori organism also recognizes, or cross-reacts with, the normal cells of the body. One well-established link between H. pylori and autoantibody formation occurs in the production of antibodies against proteins in the cells of the stomach. These antibodies can bind to the stomach’s cells and elicit a destructive immune response by inflammatory cells in the stomach tissue, leading to elimination of the antibody-bound cell. This is believed to be one way by which H. pylori infection leads to the onset of gastric atrophy. If antibodies recognize cells of the gastric mucosa, they will cause immune destruction of the cells lining the stomach. In one study conducted in Japan, more than half of the H. pylori-infected patients that were studied had antibodies in their blood that recognized normal stomach cells.
A hypothesis that is less well-established is the link between H. pylori and autoimmune thyroid disease. Studies of people with autoimmune thyroid disease have hinted that, in some people, antibodies may cross-react with cells of the thyroid gland, causing destruction of thyroid tissue. Because the thyroid gland secretes thyroid hormones that help regulate the rate of metabolism, destruction of the thyroid gland may lead to a reduction in thyroid hormones and thus a slower metabolic rate.
H. pylori have also been linked to various blood disorders. One study suggests that H. pylori is associated with the formation of antibodies against the body’s own neutrophils. This condition is thought to cause reduced levels of neutrophils in the blood, a condition known as autoimmune neutropenia. In this study, elimination of H. pylori reduced the amount of auto-antibodies in the blood and restored the normal number of neutrophils. However, this is still a controversial theory.
A reduction in blood platelets, the cells in the blood that are responsible for blood clotting, has also been tied to H. pylori and the formation of auto-antibodies. Antibodies that react against platelets cause them to be destroyed by the immune system, thereby lowering their number in the blood, a condition known as immune thrombocytopenia purpura (ITP). This is a very dangerous condition that can lead to excessive bruising
and bleeding, and can also cause a person to bleed to death if they sustain a serious injury or cut. ITP is considered a medical emergency, but treatments are available to suppress the immune reaction that causes the disease. Despite the severity of this disease, it is not known what causes the immune system to form antibodies against its platelets.While H. pylori-associated auto-antibodies have been suggested as one possible cause, this
link is still debated, and additional studies are underway to test this idea.