An autoimmune disease is one in which the body’s immune system turns against its own tissues (auto is a Greek prefix, meaning self). There are a number of diseases that fall into this category, including, lupus, rheumatoid arthritis, psoriasis or Crohn’s disease.
Multiple sclerosis (MS) is thought by many medical researchers to be an autoimmune disease. In MS, attacks are against the fatty myelin coating that surrounds and insulates nerve cells (a process called demyelination), resulting in lesions. Oligodendrocytes, which are myelin-producing cells, and nerve fibers are also damaged.
Some researchers, however, consider MS to be an “immune-mediated” disease, because the precise antigen, or substance (usually proteins), that triggers the immune system to produce antibodies against the central nervous system (CNS) is still not identified.
The immune system
The immune system is the body’s defense against disease and infection (immune comes from the Latin word immunis, meaning free or untouched). It is made up of different organs, cells and proteins, each one playing a specific role in protecting us from viruses, bacteria and foreign substances. These roles include:
- Neutralizing pathogens such as viruses, bacteria, parasites or fungi, and removing them from the body.
- Recognizing and neutralizing foreign and harmful substances from the environment.
- Fighting malignant cells involved in cancer, or other cells changed due to illness.
The immune system is incredibly complex, second only in complexity to the nervous system. It can be activated to defend against already known pathogens stored in its “memory,” allowing for a quick immune response. At the same time, it knows to recognize its own cells, so as not to work against itself.
Problems arise, however, if a foreign substance looks too much like its “self,” like its own tissues, and is ignored — or if the immune system misreads its tissues and takes them as foreign invaders. In autoimmune diseases, the immune system activates a defense against its tissues — whether nerve cells (MS), joints (rheumatoid arthritis), or the skin (scleroderma), damaging whatever’s under attack.
The immune system in MS
No one yet know the precise cause of MS. But there is little doubt that the immune system contributes to the damage done to the myelin coating on nerve fibers (axons), as well as to the axons themselves and to nerve cell bodies.
Researchers suggest these three possibilities as reasons behind such attacks:
- The immune system is fighting against an infectious agent (e.g., a virus) that mimics or otherwise looks like brain and nerve cells (an event called molecular mimickry).
- The immune system is indeed targeting unhealthy brain cells
- The immune system has begun to identify normal brain cells as foreign invaders
Although the third possibility has long been the favored explanation, recent research suggests that the first two play a role in MS, possibly by a breach in the brain-blood barrier that brings the immune system into contact with the brain for a first time.
Lymphocytes and macrophages are types of white blood cells produced by the immune system as protective agents. They circulate in the blood and cross the brain-blood barrier — a protective barrier designed to prevent blood-borne cells or other substances from crossing into the central nervous system and damaging the brain, optic nerves and spinal cord.
Somehow this system breaks down in MS, and white blood cells (lymphocytes and macrophages) cross the barrier to begin their attacks on the myelin sheath around nerve fibers. Other immune white blood cells, known as T-cells, also for unknown reasons become activated and turn against proteins in the central nervous system, causing inflammation, secreting chemicals that damage nerve axons, and recruiting other damaging immune cells.
MS treatment: Looking for immune system targets
To understand MS and slow the disease’s progression, it is necessary to better understand how the immune system is involved in the disease.
Current research is looking into these areas:
- Understanding how the system’s components (T-cells, B-cells and antibodies) work.
- Identifying new targets for therapies, especially those aiming at specific parts so as to leave much of the immune system unaffected.
- Identifying what substances or processes are behind nerve axon damage
- Identifying those agents that turn on and off immune attacks
A number of studies are being supported by the National MS Society and other patient-advocate groups. One such study identified a group of proteins, known as a complement, that may be involved in the loss of nerve connections (synapses) in the area of the brain associated with memory.
Another looked specifically at macrophages and what might trigger their damaging attacks. In this study, researchers working in a mouse model of the disease were able to differentiate between “good” and “bad” macrophages, a finding that, if supported in future research, could result in treatments that target only destructive or “bad” macrophages, preserving more of the immune system’s ability to protect from disease while limited damage done in MS.
Note: Multiple Sclerosis News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.