The Immune System & Autoimmune Disorders
What is the immune system?
The immune system is the body's means of protection against germs and other "foreign" substances. The immune system is composed of two major parts. One component is the production of antibodies, proteins that attack "foreign" substances and cause them to be removed from the body; this is sometimes called the humoral immune system. The other component is composed of special blood cells, called T lymphocytes, that can attack "foreign" substances directly; this is sometimes called the cellular immune system. At birth, the only protection we have are antibodies that come to the baby from its mother before birth; antibodies and T lymphocytes become protective only after they are exposed to a "foreign" substance for the first time. This is the reason that we use vaccinations: to allow our immune system to recognize weakened or inactivated forms of bacteria and viruses that can cause disease, so that we will be protected if we actually come in contact with them.
Normally, the immune system recognizes that the tissues in the body are not "foreign" and does not attack them. If a transplant is performed, however, the immune system usually recognizes that the organs that are transplanted are different and attacks them, a process called rejection. Drugs that reduce the activity of the immune system (immunosuppressants) are typically given to persons who have received transplants, unless the donor is an identical twin. Cancer cells are sometimes different enough from normal cells that the immune system attacks them, but the immune response alone is usually not enough to keep a cancer from spreading.
What are autoimmune disorders?
Autoimmune disorders are diseases caused by the body producing an immune response against its own tissues. The cause of autoimmune diseases is unknown, but it appears that there is an inherited predisposition to develop autoimmune disease in many cases. In a few types of autoimmune disease (such as rheumatic fever), a bacteria or virus triggers an immune response, and the antibodies or T-cells attack normal cells because they have some part of their structure that resembles a part of the structure of the infecting germ.
Autoimmune disorders fall into two general types: those that damage many organs (systemic autoimmune diseases), and those where only a single organ or tissue is directly damaged by the autoimmune process (localized). (The effect of localized autoimmune disorders, however, can be systemic as they frequently have an indirect effect other body organs and systems.) Some of the most common types of autoimmune disorders include:
| Systemic Autoimmune Diseases | Localized Autoimmune Diseases |
|---|---|
| Rheumatoid arthritis (joints; less commonly lung, skin) | Type 1 Diabetes Mellitus (pancreas islets) |
| lupus.php">Lupus [Systemic Lupus Erythematosus] (skin, joints, kidneys, heart, brain, red blood cells, other) | Hashimoto's thyroiditis, Graves' disease (thyroid) |
| Scleroderma (skin, intestine, less commonly lung) | Celiac disease, Crohn's disease, Ulcerative colitis (GI tract) |
| Sjogren's syndrome (salivary glands, tear glands, joints) | Multiple sclerosis*, Guillain-Barre syndrome (central nervous system) |
| Goodpasture's syndrome (lungs, kidneys) | Addison's disease (adrenal) |
| Wegener's granulomatosis (sinuses, lungs, kidneys) | Primary biliary sclerosis, Sclerosing cholangitis, Autoimmune hepatitis (liver) |
| Polymyalgia Rheumatica (large muscle groups) | Raynaud’s phenomenon (fingers, toes, nose, ears) |
| Temporal Arthritis / Giant Cell Arthritis (arteries of the head and neck) |
* There is still some debate as to whether MS is an autoimmune disease.
