Multiple sclerosis and the immune system: What do we know?

 The body’s immune system is a beautiful and complex defense system designed to protect us from infections. In the case of multiple sclerosis and other autoimmune conditions, however, these defenses turn on the body.

In this feature, we investigate the complicated relationship between the immune system and multiple sclerosis (MS), as well as which way the causal relationship may lie.

In a person with MS, the immune system attacks axons — or nerve fibers — in the central nervous system (CNS), which are protected by an insulating layer called myelin.

MS damages these axons in the brain, spinal cord, and optic nerves, which send visual information from the eye to the brain.

The scar tissue that MS causes as a result of its attacks is visible in the brain’s white and gray matter. During an MS attack — also called an exacerbation — different types of immune cells damage or destroy most of the myelin within the targeted area.

Experts regard MS as an autoimmune disease, but the scientific community has not been able to identify any MS-specific antigens, which are proteins that prompt the immune system to attack.

Although much is still unknown, what do we know so far about the immune system and its role in MS?

Autoimmunity: Attacking the wrong side

Similar conditions to MS that are regarded as autoimmune diseases include:

• psoriasis
• Crohn’s disease
• lupus
• rheumatoid arthritis (RA)
• type 1 diabetes

With MS, we know that T cellsTrusted Source — which play an important part in the immune system — become activated in the lymph system and then enter the CNS through blood vessels.

They then release chemicals that cause the damage associated with the condition, also activating B cells and other immune system cells to join the immune attack.

What scientists do not understand, however, is what finally knocks the immune system out of balanceTrusted Source, allowing the T and B cells to become activated.

Experts consider conditions, such as MS, RA, lupus, type 1 diabetes, and celiac disease, to be examples of autoimmune diseases that are associated with the production of autoantibodies and self-reactive T cells.

However, with psoriasis, inflammatory bowel disease, or ankylosing spondylitis, immunity against these so-called self-antigens is not a feature, even though the immune system is involved.

The question that researchers must tackle in the wake of MS is: what could prevent these self-activating T cells from attacking the CNS?

Source: Medical News Today