What is the Immune System?
Posted on: 11/18/2008
As originally published in Rochester Healthy Living
by John J Condemi, MD
What is the Immune System?
The immune system is a network of cells, tissues, and organs that work together to defend the body against attacks by “foreign” invaders including cancer cells. These are primarily viruses, bacteria, parasites, and fungi that can cause infections. It is the immune system’s job to keep them out or, failing that, to seek out and destroy them.
When the immune system hits the wrong target, however, it can cause a torrent of disorders, including allergic diseases, arthritis, and a form of diabetes. If the immune system is crippled patients are more easily infected and develop more cancers.
But why does it “hit the wrong target?
The key to a healthy immune system is its remarkable ability to distinguish between the body’s own cells, recognized as “self,” and foreign cells, or “nonself.” The body’s immune defenses normally coexist peacefully with cells that carry distinctive “self” marker molecules. But when immune defenders encounter foreign cells or organisms carrying markers that say “nonself,” they quickly launch an attack.
Anything that can trigger this immune response is called an antigen. An antigen can be a microbe such as a virus, or a part of a microbe such as a molecule. Tissues or cells from another person (except an identical twin) also carry nonself markers and act as foreign antigens. This explains why tissue transplants may be rejected.
In abnormal situations, the immune system can mistake self for nonself and launch an attack against the body’s own cells or tissues. The result is called an autoimmune disease.
Every organ can be the target resulting in diabetes, thyroid abnormalities, arthritis, and even loss of all hair.
In other cases, the immune system responds to harmless foreign substances such as ragweed pollen. The result is hayfever and asthma.
The immune system is amazingly complex. It can recognize and remember millions of different enemies, and it can produce secretions (release of fluids) and cells to match up with and wipe out nearly all of them.
The secret to its success is an elaborate and dynamic communications network. Millions and millions of cells, organized into sets and subsets, gather like clouds of bees swarming around a hive and pass information back and forth in response to an infection. Once immune cells receive the alarm, they become activated and begin to produce powerful chemicals. These substances allow the cells to regulate their own growth and behavior, enlist other immune cells, and direct the new recruits to trouble spots, or self.
Although scientists have learned much about the immune system, they continue to study how the body launches attacks that destroy invading microbes, infected cells, and tumors while ignoring healthy tissues. New technologies for identifying individual immune cells are now allowing scientists to determine quickly which targets are triggering immune response to self and nonself. Improvements in microscopy are permitting the first-ever observations of living cells as they interact within lymph nodes and other body tissues.
In addition, scientists are rapidly unraveling the genetic blueprints that direct the human immune response. The combination of new technology and expanded genetic information will no doubt reveal even more about how the body protects itself from disease and misdirects the immune system to attack self or innocuous foreign substances such as ragweed and animal dander.
About the Author
Dr. John J. Condemi is an Allergist and Rheumatologist at Allergy Asthma Immunology of Rochester (AAIR) and the Medical Director of AAIR Research Center.
Allergy, Asthma, Immunology of Rochester
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585.442.1980