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Multiple Sclerosis May Be Triggered by Beneficial Bacteria


Beneficial bacteria that everyone needs for proper digestion may be a trigger for development of multiple sclerosis, according to scientists from the Max Planck Institute of Neurobiology. Although multiple sclerosis also has a genetic component, these bacteria could prompt the disease in predisposed individuals.

Diet may have a role in multiple sclerosis

More than 2,000 different bacterial species live in the human intestinal tract, and while many of these microorganisms are part of beneficial activities, such as digestion and development of the intestines, they can also be involved in autoimmune disorders, such as Crohn’s disease. Multiple sclerosis is an autoimmune disorder in which the body’s immune system attacks the fatty protective coating, called the myelin layer, on nerve fibers in the central nervous system.

The search for environmental factors involved with multiple sclerosis led the Max Planck scientists to the current discovery. Using newly developed genetically modified mice placed in a sterile environment, they “vaccinated” the animals with natural intestinal bacteria, and the mice became ill with an inflammatory reaction similar to multiple sclerosis in humans.

However, mice in a sterile environment not exposed to the intestinal bacteria did not become ill. The explanation for these findings involves two types of immune system cells, T cells and B cells.

According to co-author Gurumoorthy Krishnamoorthy, in the mice that responded to the bacteria, the T cells became active and multiplied. These cells, along with proteins of the myelin layer, then stimulated B cells to form infectious antibodies. These processes triggered inflammation in the brain which destroyed the myelin layer, a “process that is very similar to the way multiple sclerosis develops in humans.”

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Other researchers have also been investigating other possible environmental factors in multiple sclerosis. It’s known, for example, that the disease occurs more frequently in areas farther from the equator, which has led some scientists to speculate exposure to the sun and vitamin D are involved. Vitamin D may improve immune function and thus help protect against autoimmune diseases like MS.

Infectious agents, such as viruses or bacteria also have been proposed as possible triggers. Thus far, studies of Chlamydia pneumonia, measles, Epstein-Barr, and other microorganisms have not turned up any proven candidates.

Scientists at Max Planck feel certain that intestinal bacteria can trigger the necessary response in the immune system to attack the myelin layer in individuals who have a genetic predisposition for multiple sclerosis. That means diet could be a primary factor in the disease, because nutrition has a direct impact on the bacteria that live in the intestinal tract.

Thus far, however, scientists are not certain exactly which beneficial bacteria could trigger multiple sclerosis in susceptible individuals. One way researchers can make that determination is to analyze the entire microbial genome of people who have multiple sclerosis.

Max Planck Institute
National Multiple Sclerosis Society

Picture credit: Wikimedia Commons