Good guys among bacteria bolster our immune system

Washington: Scientists have long known that certain types of bacteria boost the immune system and now researchers have discovered exactly how bacteria perform this essential task.

The human body is teeming with bacteria. In each person, there are about 10 times as many bacterial cells as human cells.

Bacteria live on skin, in the respiratory tract and throughout the digestive tract. The digestive tract alone is home to between 500 and 1,000 bacterial species.

While some bacteria cause infections, most species are harmless or perform beneficial functions, such as aiding digestion. These beneficial bugs are called commensal bacteria. One of the most important functions of commensal bacteria is boosting the immune system.

Studies by other researchers have found that mice raised in sterile, germ-free environments have poorly developed immune systems. But until now, scientists have not known the mechanism by which bacteria help the immune system.

Researchers at the Loyola University, led by Katherine L. Knight, studied the spores from rod-shaped bacteria called Bacillus, found in the digestive tract. (A spore consists of the DNA of a bacterium, encased in a shell. Bacteria form spores during times of stress, and re-emerge when conditions improve.

The researchers found that when they exposed immune system cells called B lymphocytes to bacterial spores, the B cells began dividing and reproducing. They further found that molecules on the surfaces of the spores bound to molecules on the surfaces of B cells.

This binding is what activated the B cells to divide and multiply. B cells are one of the key components of the immune system. They produce antibodies that fight harmful viruses and bacteria.

The findings suggest the possibility that some day, bacterial spores could be used to treat people with weakened or undeveloped immune systems, such as newborns, the elderly and patients undergoing bone marrow transplants, said an LUCSSM release.

In cancer patients, bacterial spores perhaps could boost the immune system to fight tumours. However, Knight cautioned that it would take years of research and clinical trials to prove whether such treatments were safe and effective.

Knight is professor and head of the microbiology and immunology department at Loyola University Chicago Stritch School of Medicine (LUCSSM). Knight`s co-authors are Kari M. Severson, Adam Driks and Michael Mallozzi.

These findings appeared in the Journal of Immunology.


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