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What is an immune-mediated disease?

Gut Reaction

Find out how scientists are exploring possible links between the gut, the immune system and MS

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On the trail for the trigger

Much research has focused on the possibility that unknown infectious agents such as viruses or bacteria might trigger the disease, though MS is not believed to be contagious.

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Searching for the Cause of MS

Part one of a series that discusses research efforts looking into the cause of multiple sclerosis.

Searching for the Cause of MS

Part one of a series that discusses research efforts looking into the cause of multiple sclerosis.


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Multiple sclerosis is considered to be an immune-mediated disease in which the body's immune system attacks the central nervous system (CNS). Most MS experts believe it to be an autoimmune disease, although this continues to be the subject of debate in the scientific community. Autoimmunity — the prefix “auto” means “self" — means that the immune system is reacting against normally-occurring antigens (proteins that stimulate an immune response) in the body, as if these antigens were foreign. However, no specific antigen has yet been identified in MS, leading some MS experts to conclude that MS cannot be classified as an autoimmune disease at this time. Some diseases thought to have an autoimmune basis are:

  • psoriasis
  • Crohns disease
  • rheumatoid arthritis
  • systemic lupus erythematosus, and
  • insulin-dependent (Type 1) diabetes mellitus.

In the case of MS, the immune system attacks and damages certain structures and cells within the CNS, including:

  • myelin (the fatty sheath that surrounds and protects nerve fibers),
  • oligodendrocytes (myelin producing cells), and
  • underlying nerve fibers.

T cells, which are one type of white blood cell in the immune system, somehow become sensitized to proteins in the CNS. When T cells become activated, they enter the CNS through blood vessels and produce damaging inflammation. Once in the CNS, these T cells not only injure myelin, but also secrete chemicals that damage nerve fibers (axons) and recruit more damaging immune cells to the site of inflammation. It is not known what causes T cells in persons with MS to become activated but it is postulated that both genetic and environmental factors are important.

Dr. Mary Hughes addresses why someone gets MS

Research directed at the role of the immune system in MS

Scientists have begun to identify the sites or “receptors” on the T cells that bind to the myelin. The precise identification of these receptor sites may help lead to the development of more specific immunosuppressant therapies that destroy these sensitized T cells while leaving other cells intact. Much of the ongoing research in MS is directed toward finding answers to questions about the cause of the altered immune response and role of the immune system in the development of MS.