What are the possible causes of multiple sclerosis (MS)?

The exact cause of multiple sclerosis (MS) remains unknown, but researchers believe that a combination of several factors may be involved, including:
  • Immunologic reaction -- MS is generally believed to be an autoimmune disease. This means that the immune system, which normally protects us from disease and infection, reacts against normally occurring antigens (proteins that stimulate an immune response) as if they were foreign. In other words, the body mistakenly attacks itself.
  • Viral or other infectious agents -- Some data suggest that a common virus or other infectious agent may play a role in the cause of MS. Whether it is a persistent viral infection or an immune reaction caused by a temporary viral infection in the CNS or elsewhere in the body is not yet known. Environmental studies suggest that some factor -- probably infectious -- must be encountered before the age of 15 in order for MS to develop later in life.
  • Environmental factors -- Epidemiologists, scientists who study disease patterns, have learned that MS occurs more frequently in geographic locations that are farther from the equator. In an effort to understand the puzzling disease patterns found in MS, scientists continue to examine geographic, demographic, and genetic variables. For example, studies have shown that people born in a geographic location with a high incidence of MS, who move to a geographic location with a lower incidence of MS before the age of 15, will acquire the lesser risk associated with their new location. Such data suggest that exposure to some environmental factor or factors prior to puberty, such as diet, exposure to industrial toxins, or content in water or soil may predispose a person to develop MS later in life.

Some researchers believe vitamin D, which the body produces naturally when the skin is exposed to sunlight, may be involved. People who live closer to the equator are continually exposed to greater amounts of sunlight. As a result, they tend to have higher levels of naturally-produced vitamin D, which is thought to have a beneficial impact on immune function and may help protect against autoimmune diseases, like MS.
  • Genetic factors -- While MS is not believed to be a hereditary disease, having a family history of MS (particularly in a parent or sibling) does make a person more likely to develop it. In a family in which one parent has MS, the risk that their children will develop the condition is estimated to be between 2 and 5 percent.
Louis Rosner

Some scientists believe multiple sclerosis (MS) may be caused by a lack of recognition of self versus nonself. It is possible that the immune system registers myelin as an antigen to attack. This is supported by the knowledge that B cells, T cells, and macrophages accumulate at the lesion site in MS. What actually causes the myelin damage is still under investigation. Some researchers believe the T cells latch onto myelin and activate the macrophages, which then attack and eat the myelin. Others believe that B lymphocytes make antibodies that bind to myelin and guide macrophages to the target. Perhaps two or more events are happening simultaneously in MS.

Besides lack of recognition, it is also possible that MS is caused by a "screw-up" in the regulation of the immune system - that a helper-inducer subset of immune system cells, which help keep the immune response going, is numerically or functionally overrepresented. Or suppressor-inducer cells, which might tone down immune response, may be numerically or functionally underrepresented in MS.

A study reported in January 1987 by Dr. Howard L. Weiner, co-director of the Center for Neurologic Diseases at Harvard Medical School, showed that the suppressor cells are indeed underrepresented, at least in patients with progressive MS. Weiner discovered the patients had only about half the normal level of the subset T-4 suppressor-inducer cell.

In October 1989 British researchers reported that Experimental allergic encephalomyelitis (EAE) was, indeed, related to "bad T-cells."

Today, researchers have identified a new T cell, called T regs, which are different from the white blood cells believed to cause the attack in MS. T regs are now being researched to see if they actually inhibit the immune response. A small study at Harvard's Brigham and Women's Hospital in Boston in 2004 compared T reg cells of 15 people with remitting-relapsing MS to the T regs of 21 people without MS. Although the T reg cell count was the same in each group, the T regs were significantly impaired in the group with MS.

A 2005 study of mice with EAE showed researchers could alter the course of disease progress by helping impaired T reg cells function.

One treatment currently under investigation for people with relapsing and progressive MS is a vaccine called NeuroVax, from Immune Response Corporation. Researchers hope the vaccine, which uses protein fragments from T cells, will replenish T reg cells and halt or diminish immune system attacks.

Multiple Sclerosis

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Multiple Sclerosis

Too often, multiple sclerosis is thought of only as "the crippler of young adults." But in fact, 75 percent of all people with MS will never need a wheelchair. In Multiple Sclerosis, Dr. Louis J....

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.