The Immune System


Definitions and about









The immune system is a set of mechanisms that protect an organism from infection by identifying and killing pathogens. This task is extremely difficult, since pathogens range from viruses to parasitic worms and these diverse threats must be detected with absolute specificity amongst normal cells and tissues. Pathogens are also constantly evolving new ways to avoid detection by the immune system and successfully infect their hosts.



The Body's First Line of Defense
The immune system is a complex of organs--highly specialized cells and even a circulatory system separate from blood vessels--all of which work together to clear infection from the body.

The organs of the immune system, positioned throughout the body, are called lymphoid organs. The word "lymph" in Greek means a pure, clear stream--an appropriate description considering its appearance and purpose.

How the Immune System Works

Cells that will grow into the many types of more specialized cells that circulate throughout the immune system are produced in the bone marrow. This nutrient-rich, spongy tissue is found in the center shafts of certain long, flat bones of the body, such as the bones of the pelvis. The cells most relevant for understanding vaccines are the lymphocytes, numbering close to one trillion.



Inside your body there is an amazing protection mechanism called the immune system. It is designed to defend you against millions of bacteria, microbes, viruses, toxins and parasites that would love to invade your body. To understand the power of the immune system, all that you have to do is look at what happens to anything once it dies. That sounds gross, but it does show you something very important about your immune system.

When something dies, its immune system (along with everything else) shuts down. In a matter of hours, the body is invaded by all sorts of bacteria, microbes, parasites... None of these things are able to get in when your immune system is working, but the moment your immune system stops the door is wide open. Once you die it only takes a few weeks for these organisms to completely dismantle your body and carry it away, until all that's left is a skeleton. Obviously your immune system is doing something amazing to keep all of that dismantling from happening when you are alive.

The immune system is complex, intricate and interesting. And there are at least two good reasons for you to know more about it. First, it is just plain fascinating to understand where things like fevers, hives, inflammation, etc., come from when they happen inside your own body. You also hear a lot about the immune system in the news as new parts of it are understood and new drugs come on the market -- knowing about the immune system makes these news stories understandable. In this article, we will take a look at how your immune system works so that you can understand what it is doing for you each day, as well as what it is not.


Immune System Mistakes

Sometimes the immune system makes a mistake. One type of mistake is called autoimmunity: the immune system for some reason attacks your own body in the same way it would normally attack a germ. Two common diseases are caused by immune system mistakes. Juvenile-onset diabetes is caused by the immune system attacking and eliminating the cells in the pancreas that produce insulin. Rheumatoid arthritis is caused by the immune system attacking tissues inside the joints.


THE IMMUNE SYSTEM is a complex and highly developed system, yet its mission is simple: to seek and kill invaders. If a person is born with a severely defective immune system, death from infection by a virus, bacterium, fungus or parasite will occur. In severe combined immunodeficiency, lack of an enzyme means that toxic waste builds up inside immune system cells, killing them and thus devastating the immune system. A lack of immune system cells is also the basis for DiGeorge syndrome: improper development of the thymus gland means that T cell production is diminished. Most other immune disorders result from either an excessive immune response or an 'autoimmune attack'. Asthma, familial Mediterranean fever and Crohn's disease (inflammatory bowel disease) all result from an over-reaction of the immune system, while autoimmune polyglandular syndrome and some facets of diabetes are due to the immune system attacking 'self' cells and molecules. A key part of the immune system's role is to differentiate between invaders and the body's own cells - when it fails to make this distinction, a reaction against 'self' cells and molecules causes autoimmune disease.


The immune system is composed of many interdependent cell types that collectively protect the body from bacterial, parasitic, fungal, viral infections and from the growth of tumor cells. Many of these cell types have specialized functions. The cells of the immune system can engulf bacteria, kill parasites or tumor cells, or kill viral-infected cells. Often, these cells depend on the T helper subset for activation signals in the form of secretions formally known as cytokines, lymphokines, or more specifically interleukins. The purpose of this article is to review the organs, cell types and interactions between cells of the immune system as a commentary on their importance and interdependence on the T helper subset. Such an understanding may help comprehend the root of immune deficiencies, and perceive potential avenues that the immune system can be modulated in the case of specific diseases.


Cells of the Immune System

Cells destined to become immune cells, like all blood cells, arise in your body's bone marrow from stem cells. Some develop into myeloid progenitor cells while others become lymphoid progenitor cells.

The myeloid progenitors develop into the cells that respond early and nonspecifically to infection. Neutrophils engulf bacteria upon contact and send out warning signals. Monocytes turn into macrophages in body tissues and gobble up foreign invaders. Granule-containing cells such as eosinophils attack parasites, while basophils release granules containing histamine and other allergy-related molecules.

Lymphoid precursors develop into the small white blood cells called lymphocytes. Lymphocytes respond later in infection. They mount a more specifically tailored attack after antigen-presenting cells such as dendritic cells (or macrophages) display their catch in the form of antigen fragments. The B cell turns into a plasma cell that produces and releases into the bloodstream thousands of specific antibodies. The T cells coordinate the entire immune response and eliminate the viruses hiding in infected cells.


The Immune System and the Nervous System

Biological links between the immune system and the central nervous system exist at several levels.

Hormones and other chemicals such as neuropeptides, which convey messages among nerve cells, have been found also to "speak" to cells of the immune system--and some immune cells even manufacture typical neuropeptides. In addition, networks of nerve fibers have been found to connect directly to the lymphoid organs.

The picture that is emerging is of closely interlocked systems facilitating a two-way flow of information. Immune cells, it has been suggested, may function in a sensory capacity, detecting the arrival of foreign invaders and relaying chemical signals to alert the brain. The brain, for its part, may send signals that guide the traffic of cells through the lymphoid organs.


What your immune system does:

The immune system protects the body against infections by bacteria, viruses and other parasites. It is really a collection of responses that the body makes to infection. So it is sometimes called the 'immune response'.

The immune system is important to cancer patients in many ways because

* The cancer can weaken the immune system
* Cancer treatment can weaken the immune system
* The immune system may help to fight your cancer

The cancer can weaken the immune system by invading the bone marrow where the cells that help fight infection are made. This happens most often in leukaemia or lymphoma. But it can happen with other cancers too.



Vaccination works by using this 'immune memory'. The vaccine contains a small amount of protein from a disease. This is not harmful, but it allows the immune system to recognise the disease if it meets it again. The immune response can then stop you getting the disease. Some vaccines use tiny amounts of the live bacteria or virus. These are called live attenuated vaccines. Attenuated means that the virus or bacteria has been changed so that it will stimulate the immune system to make antibodies but won't cause the infection. Other types of vaccine use killed bacteria or viruses, or chemicals produced by bacteria and viruses.


Everyone experiences stress. Whether it is everyday hassles, such as being stuck in traffic, or more acute forms of stress, such as pain or traumatic experiences, stress plays a part in everyone's lives. In this paper I will discuss the various forms of stress, how stress affects the immune system, and how that affectation influences diseases.

Before diving right into the technical aspects of stressors and the immune system, I need to define several terms. A stressor is any stimuli that causes a nonspecific response in an indidual, otherwise known as stress (Elliott and Eisdorfer, 1982).

In order to understand these changes, I must first introduce you to the immune system. The immune system protects the body from disease organisms and other foreign bodies, known as antigens. The first line of defense is local barriers such as the skin, peritoneum, etc, and inflammation due to immunoglobulins, or antibodies. If those fail to block or destroy the antigens, the cell-mediated immune response and the humoral immune response kick in. The cell-mediated response uses sensitized T cells (white blood cells derived in the thymus) to recognize, attach to, and render antigens inactive. Other types of T cells, helper T cells, which aid in production of antibodies by B (bone marrow) cells, and suppressor/cytotoxic T cells, which inhibit that production, are also essential for proper immune system function. Helper T cells are also known as CD4 cells, and suppressor T cells are known as CD8 cells (Glaser, Anderson & Anderson, 1992)


The Immune System


The immune system is a network of organs, glands, and tissues that protects the body from foreign substances. These substances include bacteria, viruses, and other infection-causing parasites and pathogens. Usually, the immune system is extremely effective in performing its work of defending the body, but sometimes an error occurs in this highly complex system, and it can lead to terrible mistakes. The result can be an allergic reaction, which can be as simple as a case of the sniffles and as serious as a fatal condition. Or the error can manifest as an autoimmune disorder, such as lupus, in which the body rejects its own constituents as foreign invaders.



Killer blood cells, known by the generic name phagocyte, engulf the bacteria and digest-them, but even as this is occurring, the rapid reproduction of the bacterium provides a challenge to the immune system. If the infectious agent reproduces at a rate beyond the control of the immune system, the physician may provide help in the form of an antibiotic. Alternatively, he or she may lance (cut open) a superficial infection to allow it to drain and to provide access for an antiseptic agent. If the bacterial invasion is minor, the immune system soon dispatches the invader, and the system returns to normal.

Often, some of the white blood cells form antibodies against such invading bacteria, so that the immune system will be better armed to combat any future invasions by the same microorganism. The white blood cell count returns to its normal level, but still with the capability of mobilizing the immune defense on short notice. It is this response that is the basis for inoculations against certain infections, a topic discussed in Immunity. Sometimes, however, something goes wrong in the production of antibodies, and instead of properly protecting the body against invaders, the immune system creates an allergy.



Innate immunity

If microorganisms successfully breach the surface barriers, the cells and mechanisms of the innate immune system are present, and ready to be mobilized to defend the the host. Innate immune defenses are non-specific, meaning that the innate system recognizes and responds to, pathogens in a generic way. The innate system does not confer long-lasting or protective immunity to the host. It is thought to constitute an evolutionarily older defense strategy, and is the dominant system of host defense in plants, fungi, insects, and in primitive multicellular organisms. The innate immune system protects the host by establishing humoral, chemical and cellular barriers to infection.



The Immune System - Defending our Bodies

Ilya Mechnikov, one of the pioneers of immune system research, inserted a thorn into a larva and noticed strange cells gathering around the thorn. The cells were eating any foreign substances entering the ruptured skin. He called these cells phagocytes meaning "devouring cells." He later shared the 1908 Nobel Prize in Physiology or Medicine with another pioneer in the same field, Paul Ehrlich.



Organs of the Immune System

The organs of your immune system are positioned throughout your body.

They are called lymphoid organs because they are home to lymphocytes--the white blood cells that are key operatives of the immune system. Within these organs, the lymphocytes grow, develop, and are deployed.

Bone marrow, the soft tissue in the hollow center of bones, is the ultimate source of all blood cells, including the immune cells.

The thymus is an organ that lies behind the breastbone; lymphocytes known as T lymphocytes, or just T cells, mature there.

The spleen is a flattened organ at the upper left of the abdomen. Like the lymph nodes, the spleen contains specialized compartments where immune cells gather and confront antigens.

In addition to these organs, clumps of lymphoid tissue are found in many parts of the body, especially in the linings of the digestive tract and the airways and lungs--gateways to the body. These tissues include the tonsils, adenoids, and appendix.



Immune System:

The body's defense department - Alternative Medicine
The immune system is not responsive to drugs for healing. Antibiotics used to fight infections actually depress the immune system when used long-term. But natural nutritive forces, like healing foods and herbal medicines can and do support the immune system. By rebuilding immunity, health is naturally restored and disease disappears.

Dr. Lawrence Wilson - "To strengthen the immune system, one must address the needs of the whole body. A strong immune system is essential for health. It is a very complex system of the body, involving the skin, intestines, nasal mucosa, blood, lymph and many other organs and tissues. Factors that impair the immune system include nutrient deficiencies, contaminated air, water and food, unhealthful lifestyles and too much exposure to harmful microbes. Other factors that weaken the immune system are negative attitudes and emotions and the presence of toxic metals, toxic chemicals and biological toxins in the body. Others are sluggish metabolism, lack of rest and sleep, excessive stress or too much exercise. As these causative factors are removed or corrected, the immune system improves."



William J. Hennen, PhD. - “It is increasingly clear that as the world becomes a smaller place with viruses and other pathogens traveling with great ease, we face now a unique challenge. Simply put, we are now, and will be, more exposed to challenges to our health. However, nature has already provided the immune system as the defense to the microbes in our environment. To the degree we are able to educate the immune system to recognize the invader, will determine our ability to cope with the challenges. I urge all people to pay attention to those things that affect your immune system.”

According t o Dr. George C Pack, MD, a cancer specialist at Cornell medical School, almost everyone has cancer cells present at times in our bodies. If our immune system is working properly, these cells are killed or reabsorbed by our defense system before they begin to grow and threaten our health. The only real defense against cancer is the immune system. Everyone gets cancer every day but if the immune system is where it should be those cancer cells are eliminated and we never know it.



What made the difference? The power of the immune system. It's a network that can help us avoid illness -- or sometimes become the underlying reason we get sick.

"The strength of our immune system is what makes the difference between who gets sick and who doesn't. The one with the immune system functioning below base-line normal has an increased risk of getting sick," says Woodson Merrell, MD, director of integrative medicine at Beth Israel Medical Center in New York City.

But is there anything you can do to keep your immune system from dropping below par -- or increase its activity if it does?

Doctors say yes. And the secrets lie in understanding a bit about how the immune system works -- and how your everyday life can stoke the fires of protection.

In simplest terms, the immune system is a balanced network of cells and organs that work together to defend you against disease. It blocks foreign proteins from getting into your body. If a few happen to sneak by your biological sentry, not to worry. With a powerful "search and destroy" task force, your body deploys a host of additional immune cell forces designed to hunt down these unwanted invaders and ultimately works to destroy them.



Feeling insecure in close relationships may take a toll on the immune system, preliminary Italian research suggests.

A team led by Dr Angelo Picardi from the Italian National Institute of Health in Rome reports its findings in the current issue of the journal Psychosomatic Medicine.

In a study of 61 healthy women the researchers found that those who had difficulty establishing close, trusting relationships showed signs of weaker immune function.

Specifically, lab experiments showed that the women's "natural killer" immune system cells were less lethal compared with those from other study participants.

Whether this means they're more susceptible to disease is unknown, and for now the answer to that question is a "very prudent maybe", says Picardi.

The findings are in line with research showing that chronic stress can impair immunity, and the extent of the impact may depend on how an individual perceives and responds to stress.

In short, personality traits may affect immune function.



How should echinacea be taken and what is the proper dosage?
When and how much echinacea to take depends on your individual immune system and the medical reason why you want to take it. Best to seek dosage and timing advice from a naturopath or medical doctor knowledgeable about herbal medicines. For example, there are conditions in which you wouldn't want to hype up your immune system, such as illnesses presumably caused by an overactive immune system called "autoimmune diseases."



An army of millions of microscopic soldiers operates within you, each one ready to spring into battle against invading germs and to do sentry duty to prevent disease from occurring in the first place. How you feed these soldiers has a great influence on how well they protect you from germs and disease. Because of poor diets, many school-age children and adults have immune systems that don't operate at peak efficiency. They get sick more often. Here's how to have a well-nourished immune system.

Think of the immune system as an army in which each division has a specific job, depending on the enemy they are fighting. Let's meet the troops to see what each kind of defender does.

White blood cells are the body's infantry, the hard-working soldiers on the front lines. These cells patrol the highway of the body's bloodstream, preventing germs from gaining a foothold. There are millions of these microscopic fighters in each drop of blood. There are also many specialized units. For example, when enemy cells try to hide from the main white cell troops, specialized units of white cells, called macrophages (the word means "big eaters"), mount search-and-destroy missions, going into all the nooks and crannies of the body to gobble up harmful invaders.



Understanding Your Immune System

My immune system was hit hard by chemotherapy. They did a blood count and the intern came back in a panic. "Your white count—there's nothing lower on the scale!" But then my oncologist came in and told me not to worry. "You're going to be fine," he said. I figured, if it's doing this to me, think of what it's doing to the cancer.

Women dealing with breast cancer inevitably wonder: Did I get breast cancer because my immune system was weakened by stress, or by the wrong food? Can my immune system fight breast cancer? Will surgery, chemotherapy, and radiation therapy reduce my body's ability to fight breast cancer and infections? How can I fortify my immune system to become as healthy as possible?



Generalized immune response

The immune system responds immediately when your body encounters any threat, such as a virus or injury. In response to such threats, the immune system produces a generalized, non-specific reaction known as inflammation. This response is like an army artillery attack: Shells burst all over, damaging and killing all varieties of bacteria, viruses, and other microorganisms that happen to be in range—including some of the body's own cells.

Key cells involved in this reaction include the white blood cells, macrophages, and neutrophils, which produce powerful destructive chemicals known as free radicals.



Our Immune System Defends Us Against Infectious Diseases

Our immune system protects us against threats. These include viruses, bacteria and parasites causing infectious diseases, from ordinary flu to full-blown malaria. The white blood cells of the defense system are produced in the marrow of our bones. The cells are carried in the blood to specialized organs, where they develop and communicate to launch immune responses against infections. Immune responses are aggressive and must be controlled. They should be activated only when the body is threatened by disease. To learn how to start or stop the immune system we must understand how microorganisms and sick cells are recognized by white blood cells.



Howstuffworks "How Your Immune System Works"
Inside your body there is a mechanism designed to defend you from millions of bacteria, microbes, viruses, toxins and parasites.

Immune System
The immune system is made up of special cells, proteins, tissues, and organs that defend people against germs and microorganisms.

The Anatomy of the Immune System
In depth look at the immune system and all its separate parts.

Immune system
Genes and disease provides short descriptions of inherited disorders. It is hosted by the National Center for Biotechnology Information (NCBI), ...

The Immune System -- An Overview - The Body
Brief introduction to the organs, cells and processes of the immune system. Includes HIV AIDS related links. Written in 1993 for the Seattle Treatment.

immune system: Definition and Much More from
immune system n. The integrated body system of organs, tissues, cells, and cell products such as antibodies that differentiates self from nonself and.

Stress and the Immune System
Paper by Hannah Koenker regarding the effects of stress on the immune system.

The immune system
This page tells you about the immune system. There is information on What your immune system doesInbuilt immune protectionNeutrophilsAcquired immunityB.

Immune System- National Institutes of Health (NIH)
Health Topics organized under Immune System - National Institutes of Health (NIH)

immune system

Our Immune System Defends Us Against Infectious Diseases
Our immune system protects us against threats. These include viruses, bacteria and parasites causing infectious diseases, from ordinary flu to full-blown.

ScienceDaily: Immune System News
Immunity and the Immune System. Read the latest medical research on immune response, immune deficiency, immune system diseases and immune system boosters.

The Natural Immune System Diet, healthy foods for immune system health
Selection of dietary advice based on the immune system.

Cells of the Immune System
Descriptions and pictures of the cells involved in the immune response.





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