The immune system is a complex network of specialized cells and organs that has evolved to defend the body against attacks by "foreign: invaders.
The immune system displays both enormous diversity and extraordinary specificity; not only is it able to recognize many millions of distinctive nonself molecules, it can produce molecules and cells to match up with and counteract each one of them.
Although people can live without a spleen, persons whose spleens have been damaged by trauma or by disease such as sickle cell anemia, are highly susceptible to infection; surgical removal of the spleen is especially dangerous for young children and the immunosuppressed.
IgM, which usually combines in star-shaped clusters, tends to remain in the bloodstream, where it is very effective in killing bacteria.
IgA concentrates in body fluids-tears, saliva, the secretions of the respiratory and gastrointestinal tracts-guarding the entrances to the body.
IgE, which under normal circumstances occurs only in trace amounts, probably evolved as a defense against parasites, but it is more familiar as the villain in allergic reactions (Allergy).
IgD is almost exclusively found inserted into the membranes of B cells, where it somehow regulates the cell's activation.
Dairy Allergies Dairy allergy, or milk allergy, refers to any allergic reaction caused by a component of cow's milk. The three components of cow's milk that cause dietary reactions are casein protein, whey protein, and lactose sugar.
Egg Allergies Most egg allergies begin in childhood, and eggs are one of the most common food allergies for children. Up to 80 percent of children will outgrow their allergy to egg products by the age of six. However, egg allergies develop at older ages as well.
The immune system is a complex network of specialized cells and organs that has evolved to defend the body against attacks by "foreign" invaders. When functioning properly it fights off infections by agents such as bacteria, viruses, fungi, and parasites. When it malfunctions, however, it can unleash a torrent of diseases, from allergy to arthritis to cancer to AIDS.
Get Tested for Your Immune System Problem
The Opti-Plus panel consists of a series of 47 different tests that can evaluate not only medical conditions, but to also pin point underlying functional disturbances that continue to make you have less than optimal health. You will receive not only the actual lab values, but rather a thorough explanation of what the values mean in an easy-to-understand format.
In addition, lifestyle and dietary recommendations are made that fit into the context of your lab values that result in truly improved health.
Finally, you will also receive a detailed list of supplements that target your out-of-range values to return your body back to a normal functioning state.
Components of the Immune System
The immune system evolved because we live in a sea of microbes. Like man, these organisms are programmed to perpetuate themselves. The human body provides an ideal habitat for many of them and they try to break in; because the presence of these organisms is often harmful, the body's immune system will attempt to bar their entry or, failing that, to seek out and destroy them.
The immune system, which equals in complexity the intricacies of the brain and nervous system, displays several remarkable characteristics. It can distinguish between "self" and "nonself." It is able to remember previous experiences and react accordingly; thus, once you have had chicken pox, your immune system will prevent you from getting it again. The immune system displays both enormous diversity and extraordinary specificity; not only is it able to recognize many millions of distinctive nonself molecules, it can produce molecules and cells to match up with and counteract each one of them. And it has at its command a sophisticated array of weapons.
The success of this system in defending the body relies on an incredibly elaborate and dynamic regulatory-communications network. Millions and millions of cells, organized into sets and subsets, pass information back and forth like clouds of bees swarming around a hive. The result is a sensitive system of checks and balances that produces an immune response that is prompt, appropriate, effective, and self-limiting.
The organs involved with the immune system are called the lymphoid organs, which affect growth, development, and the release of lymphocytes (a certain type of white blood cell). The blood vessels and lymphatic vessels are important parts of the lymphoid organs, because they carry the lymphocytes to and from different areas in the body. Each lymphoid organ plays a role in the production and activation of lymphocytes. Lymphoid organs include:
adenoids (two glands located at the back of the nasal passage)
blood vessels (the arteries, veins, and capillaries through which blood flows)
bone marrow (the soft, spongy tissue found in bone cavities)
lymph nodes (small organs shaped like beans, which are located throughout the body and connect via the lymphatic vessels)
lymphatic vessels (a network of channels throughout the body that carries lymphocytes to the lymphoid organs and bloodstream)
Peyer’s patches (lymphoid tissue in the small intestine)
thymus (two lobes that join in front of the trachea behind the breast bone)
tonsils (two oval masses in the back of the throat)
Self & Non-self
At the heart of the immune system is the ability to distinguish between self and nonself. Virtually every body cell carries distinctive molecules that identify it as self.
The body's immune defenses do not normally attack tissues that carry a self marker. Rather, immune cells and other body cells coexist peaceably in a state known as self-tolerance. But when immune defenders encounter cells or organisms carrying molecules that say "foreign," the immune troops move quickly to eliminate the intruders.
Any substance capable of triggering an immune response is called an antigen. An antigen can be a virus, a bacterium, a fungus, or a parasite, or even a portion or product of one of these organisms. Tissues or cells from another individual, except an identical twin whose cells carry identical self-markers, also act as antigens; because the immune system recognizes transplanted tissues as foreign, it rejects them. The body will even reject nourishing proteins unless they are first broken down by the digestive system into their primary, non-antigenic building blocks.
An antigen announces its foreignness by means of intricate and characteristic shapes called epitopes, which protrude from its surface. Most antigens, even the simplest microbes, carry several different kinds of epitopes on their surface; some may carry several hundred. However, some epitopes will be more effective than others at stimulating an immune response.
In abnormal situations, the immune system can wrongly identify self as nonself and execute a misdirected immune attack. The result can be a so-called autoimmune disease such as rheumatoid arthritis or systemic lupus erythematosus.
In some people, an apparently harmless substance such as ragweed pollen or cat hair can provoke the immune system to set off the inappropriate and harmful response known as allergy; in these cases the antigens are known as allergens.
Genes & the Markers of Self
Molecules that mark a cell as self are encoded by a group of genes that is contained in a sections of a specific chromosome known as the major histocompatibility complex (MHC). The prefix "histo" means tissue; the MHC was discovered in the course of tissue transplantation experiments. Because MHC genes and the molecules they encode vary widely in the details of their structure from one individual to another (a diversity known as polymorphism), transplants are very likely to be identified as foreign and rejected by the immune system.
Scientists eventually discovered a more natural role for the MHC: it is essential to the immune defenses. MHC markers determine which antigens an individual can respond to, and how strongly. Moreover, MHC markers allow immune cells such as B cells, T cells, and macrophages to recognize and communicate with one another.
One group of proteins encoded by the genes of the MHC are the markers of self that appear on almost all body cells. Known as class I MHC antigens, these molecules alert killer T cells to the presence of body cells that have been changed for the worse-infected with a virus or transformed by cancer-and that need to be eliminated.
A second group of MHC proteins, class II antigens, are found on B cells, macrophages, and other cells responsible for presenting foreign antigen to helper T cells. Class II products combine with particles of foreign antigen in a way that showcases the antigen and captures the attention of the helper T cell.
This focusing of T cell antigen recognition through class I and class II molecules is known as MHC (or histocompatibility) restriction.
The Anatomy of the Immune System
The organs of the immune system are stationed throughout the body. They are generally referred to as lymphoid organs because they are concerned with the growth, development, and deployment of lymphocytes, the white cells that are the key operatives of the immune system. Lymphoid organs include the bone marrow and the thymus, as well as lymph nodes, spleen, tonsils and adenoids, the appendix, and clumps of lymphoid tissue in the small intestine known as Peyer's patches. The blood and lymphatic vessels that carry lymphocytes to and from the other structures can also be considered lymphoid organs.
Cells destined to become immune cells, like all other blood cells, are produced in the bone marrow, the soft tissue in the hollow shafts of long bones. The descendants of some so-called stem cells become lymphocytes, while others develop into a second major group of immune cells typified by the large, cell-and particle-devouring white cells known as phagocytes.
The two major classes of lymphocytes are B cells and T cells. B cells complete their maturation in the bone marrow. T cells, on the other hand, migrate to the thymus, a multilobed organ that lies high behind the breastbone. There they multiply and mature into cells capable of producing immune response-that is, they become immunocompetent. In a process referred to as T cell "education," T cells in the thymus learn to distinguish self cells from nonself cells; T cells that would react against self antigens are eliminated.
Upon exiting the bone marrow and thymus, some lymphocytes congregate in immune organs or lymph nodes. Others-both B and T cells-travel widely and continuously throughout the body. They use the blood circulation as well as a bodywide network of lymphatic vessels similar to blood vessels.
Laced along the lymphatic routes-with clusters in the neck, armpits, abdomen, and groin-are small, bean-shaped lymph nodes. Each lymph node contains specialized compartments that house platoons of B lymphocytes, T lymphocytes, and other cells capable of enmeshing antigen and presenting it to T cells. Thus, the lymph node brings together the several components needed to spark an immune response.
The spleen, too, provides a meeting ground for immune defenses. A fist-sized organ at the upper left of the abdomen, the spleen contains two main types of tissue: the red pulp that disposes of worn-out blood cells and the white pulp that contains lymphoid tissue. Like the lymph nodes, the spleen's lymphoid tissue is subdivided into compartments that specialize in different kinds of immune cells. Microorganisms carried by the blood into the red pulp become trapped by the immune cells known as macrophages. (Although people can live without a spleen, persons whose spleens have been damaged by trauma or by disease such as sickle cell anemia, are highly susceptible to infection; surgical removal of the spleen is especially dangerous for young children and the immunosuppressed.)
Nonencapsulated clusters of lymphoid tissue are found in many parts of the body. They are common around the mucous membranes lining the respiratory and digestive tracts-areas that serve as gateways to the body. They include the tonsils and adenoids, the appendix, and Peyer's patches.
The lymphatic vessels carry lymph, a clear fluid that bathes the body's tissues. Lymph, along with the many cells and particles it carries-notably lymphocytes, macrophages, and foreign antigens, drains out of tissues and seeps across the thin walls of tiny lymphatic vessels. The vessels transport the mix to lymph nodes, where antigens can be filtered out and presented to immune cells.
Additional lymphocytes reach the lymph nodes (and other immune tissues) through the bloodstream. Each node is supplied by an artery and a vein; lymphocytes enter the node by traversing the walls of the very small specialized veins.
All lymphocytes exit lymph nodes in lymph via outgoing lymphatic vessels. Much as small creeks and streams empty into larger rivers, the lymphatics feed into larger and larger channels. At the base of the neck, large lymphatic vessels merge into the thoracic duct, which empties its contents into the bloodstream.
Once in the bloodstream, the lymphocytes and other assorted immune cells are transported to tissues throughout the body. They patrol everywhere for foreign antigens, then gradually drift back into the lymphatic vessels, to begin the cycle all over again.
Free Health Tests & Professional Consultations
Take this preliminary to see if your condition could respond to treatment.
Not sure on your treatment options? For a limited time you can schedule a to talk with a licensed doctor or clinician regarding your condition.
Use our to find a doctor in your area.
Understanding the Human Body e-book
Thomas Edison once said, "The doctor of the future will give no medicine, but will interest his patients in the care of the human frame, in diet, and in the cause and prevention of disease." Our extensive eBook on the Human Body does just that. An excellent tool to use for reference and learning, and with over 500 pages of information, you'll be able to find information on any organ in the human body. Complete with thousands of graphics and multimedia presentations. A glossary for those hard-to-find terms. Get your copy today by following this link. If you're going to take care of your body, this is a must!
Eating Your Way to Health e-Book
Are you totally confused and don't know who to trust with nutritional advice? If you've been searching for a sensible, useable book regarding nutrition, this is it. Eating Your Way to Health - The Essential Nutrition Guide To Reclaim Your Health, contains hundreds of articles that dispel the myths about nutrition, you can finally get honest advice about your diet and begin a sensible eating plan to regain your health. Find out the basics regarding carbohydrates, proteins, fats, fiber, vitamins, minerals and food supplements. In addition, we've spent hundreds of hours compiling healthful recipes that would take several cookbooks to fill. Recipes are categorized by food type. Get your personal copy today.
The immune system, which equals in complexity the intricacies of the brain and nervous system, displays several remarkable characteristics. It can distinguish between "self" and "nonself." It is able to remember previous experiences and react accordingly; thus, once you have had chicken pox, your immune system will prevent you from getting it again. The immune system displays both enormous diversity and extraordinary specificity; not only is it able to recognize many millions of distinctive nonself molecules, it can produce molecules and cells to match up with and counteract each one of them. And it has at its command a sophisticated array of weapons.
The organs of the immune system are stationed throughout the body. They are generally referred to as 
The lymphatic vessels carry 
