The Immune System and Multiple Sclerosis (MS)

A healthy immune system protects you from harmful substances entering your body and causing infection or disease. In multiple sclerosis (MS), your immune system malfunctions and starts attacking your central nervous system (CNS).

Your CNS consists of your brain, spinal cord, and the optic nerves of your eyes. Immune system attacks on your CNS may cause a variety of symptoms, including blurry vision, numbness and tingling, muscle weakness, and many more.

In this article, you'll learn how your immune system normally functions and what happens in MS when it goes awry. You'll also learn how various disease-modifying drugs can help curb such attacks.

How the Immune System Works With Multiple Sclerosis - Illustration by Laura Porter

Verywell / Laura Porter

How the Immune System Works

Your immune system is a complex collection of organs, proteins, and cells that work together to protect your body from foreign substances.

Foreign substances include bacteria, viruses, fungi, parasites, and cancer cells, all of which may cause infection and disease if not attacked and destroyed.

A type of white blood cell called a lymphocyte plays an important role in the normal functioning of your immune system.

How Lymphocytes Travel

Lymphocytes move around your body through the lymphatic system, which is an extensive network of organs, nodes, and vessels that carry a clear, watery fluid called lymph back into your bloodstream.

There are two main types of lymphocytes:

  • B cells develop in the bone marrow (the spongy center part of your bones). They produce Y-shaped proteins called antibodies that recognize and lock onto foreign substances to remove them from the body.
  • T cells mature in the thymus gland (a small organ located beneath your breastbone). They respond to any foreign substances by releasing chemicals that cause inflammation and damage. They also activate B cells and other cells to participate in the immune system attack.

When your immune system malfunctions, lymphocytes and other immune system cells may start destroying your own tissue, thinking it's a foreign invader when it's not. This phenomenon is known as an autoimmune disease.

Autoimmune disease can affect one or multiple types of tissue in your body. There are over 100 known autoimmune diseases, and specific symptoms depend on which tissues are being targeted and damaged.

MS is generally considered by most experts to be an autoimmune disease. That said, since no specific antigens (proteins on cells that trigger the immune system to malfunction) have been identified, some experts prefer to call MS an "immune-mediated" disease.

Changes Caused by MS

In MS, your immune system becomes confused and sends T cells to break through your blood-brain barrier (BBB) to enter your central nervous system.

Your BBB is a layer of closely spaced cells located in your brain's capillaries. Its purpose is to serve as a filter or roadblock, preventing harmful substances from entering your brain.

Once in the CNS, the T cells release inflammatory chemicals that damage myelin, nerve fibers (axons), and the cells that make myelin (called oligodendrocytes). They also recruit and stimulate B cells and other types of immune system cells to further the attack.

Myelin's Role

Myelin is the fatty covering that surrounds and insulates nerve fibers. Besides protecting nerve fibers, myelin also allows nerve signals to be transmitted rapidly and efficiently.

When myelin and the nerve fibers are damaged and destroyed, scar tissue called "sclerosis" forms, and communication between your central nervous system and the rest of your body is disrupted. With this disruption of nerve signals, a variety of symptoms may occur.

Symptoms and Complications

The symptoms of MS are highly variable, depending on which nerve signals are impacted.

Common MS symptoms include:

If the symptoms of MS become severe or are not managed well, various complications may arise. For instance, bladder dysfunction can cause repeated urinary tract infections, or kidney stones or damage. Untreated bladder dysfunction may also contribute to MS weakness and spasticity.

Other potential MS complications include:

  • Pressure sores: Areas of skin breakdown that develop after sitting or lying in one position for a prolonged period of time
  • Osteoporosis: A condition of bone weakening and loss due to inactivity or a side effect of taking steroids for MS relapses
  • Aspiration pneumonia: A lung infection caused by inhaling food particles due to problems swallowing and/or an inability to clear mucus from the nose or throat

Treatment for Immune Attacks

Early treatment with disease-modifying therapies (DMTs) offers your best bet for preventing permanent immune-system-related damage to the CNS and delaying disability.

Specifically, DMTs have been found to reduce the number and severity of MS relapses. A relapse, also called a flare-up, occurs when a patient develops new or worsening symptoms. Relapses are followed by periods of symptom recovery (remission).

DMTs have also been found to slow the natural progression of the disease, where symptoms gradually worsen and disability accumulates.

There are numerous DMTs approved to treat MS, and they are unique in terms of their side effect profiles and how they are administered (e.g., by mouth, injected, or infused through a vein).

DMTs also differ in how they work. Some DMTs work by limiting the number of immune system cells that can enter the CNS, whereas others interfere with T cell or B cell activation or movement.

Regardless of their exact manner of action, the goal of all DMTs is to disrupt the immune system's misguided attack on the CNS.

Besides DMTs, there are other treatments under investigation that may alter your immune system and reduce disease activity.

For example, the dietary supplement vitamin D appears to play a role in regulating the immune system. Also, probiotics may alter your gut microbiome and, as a result, calm down your immune system. Your doctor can help you determine whether one or both of these supplements is right for you.


Your immune system is your body's main line of defense against infection and disease. In MS, your immune system mistakenly attacks healthy tissue within your brain and spinal cord. This leads to symptoms that affect how you see, feel, move, and think. Taking a disease-modifying drug can disrupt your immune system's abnormal response and, in effect, slow down your MS.

A Word From Verywell

Exactly why a person's immune system goes haywire in MS remains a mystery. As frustrating and unfair as having MS is, you can try to "right" your immune system by taking a disease-modifying treatment early on and consistently. The good news, too, is that there are several medication options available—ones that can meet your needs, schedule, comfort level, and preferences.

Frequently Asked Questions

  • Is multiple sclerosis an autoimmune disease?

    MS is generally classified as an autoimmune disease. That said, since the specific proteins that trigger the immune system in MS to go wrong have not yet been identified, some experts prefer to call MS an "immune-mediated" disease.

  • Is MS considered immunocompromised?

    Not directly. The immune system in people with MS is not weakened or compromised. However, MS medications like steroids and some disease-modifying therapies can weaken your immune system and make you more vulnerable to infection.

  • What organs are affected by multiple sclerosis?

    MS affects your central nervous system (CNS). Your CNS consists of your brain, spinal cord, and the optic nerves in your eyes.

  • Are MS patients more prone to infections?

    Yes, due to the interplay of multiple factors, people with MS are at an increased risk of infection compared with the general population.

11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Colleen Doherty, MD
 Colleen Doherty, MD, is a board-certified internist living with multiple sclerosis.