Unraveling the Mystery of Autoimmunity

Everybody wants to have a strong immune system. It is the body's own personal Department of Defense, protecting you from invading armies of harmful viruses and bacteria. Yet even with all the smart weaponry at its command, the immune system can sometimes go awry, attacking the body it was suppose to protect.

Dr. Noel Rose, from the Department of Pathology at Johns Hopkins School of Medicine and Director of the Johns Hopkins Center for Autoimmune Disease Research, has spent the better part of his career following the common thread that weaves autoimmune diseases together. Below, Rose shows how autoimmune diseases are linked and what the future might hold.

What is autoimmunity?
Traditionally, the immune response has been understood as the body's method of defending itself against disease, which it does by identifying and destroying foreign invading microorganisms. Usually its specialized cells, called lymphocytes, do a fine job of keeping illness at bay. But by contrast, autoimmunity involves an immune response to something within the body itself.

How does the immune system distinguish between what belongs in our bodies and what doesn't?
The job of the immune system is to produce antibodies against antigens which cause harm. So why doesn't the immune system normally produce antibodies to molecules in our own bodies? The answer lies in the complex mechanisms that govern self-recognition and self-tolerance.

Everyone produces lymphocytes that are potentially capable of recognizing and even attacking "self." Normally, these cells are either deleted very early or they're held in check by regulatory controls. When these safeguards fail, so-called autoantibodies develop. Everyone has autoantibodies - antibodies in your blood that react to something in your own bodies.

Are autoantibodies and autoimmunity are normal?
Autoimmunity is mostly harmless. Some immunologists even believe it may be helpful. Autoantibodies may help to remove worn out or dead cells, but firm evidence for this is not yet at hand. Clearly, though, an autoimmune reaction can go too far, and that's where the problem begins.

What is autoimmune disease?
The definition of an autoimmune disease is sometimes very hard to pin down. There is no universal agreement on which diseases are autoimmune and which are not. Autoimmunity may be present in the disease, but may not be actually causing it.

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