The Immune System

The immune system, which is made up of unique cells, proteins, tissues and organs, defends people against germs and microorganisms 24/7. In most cases, the immune system does a great job of keeping people healthy and preventing infections. But every so often problems with the immune system can lead to illness and infection.

What the Immune System Does

The immune system is the body’s main defense against infectious organisms and other nasty invaders. Through a series of steps called the immune response, the immune system literally attacks organisms and substances that assault our systems and cause disease. The immune system is made up of a vast network of cells, tissues, and organs that work in combination together to protect your body. The cells that are part of this defense system are white blood cells, or leukocytes. They appear in two basic types, which combine to seek out and obliterate the organisms or substances that cause disease. Leukocytes are produced or stored in numerous locations throughout the body, including the thymus, spleen and bone marrow. (For this reason, they are called the lymphoid organs.) There are also clumps of lymphoid tissue throughout the body, primarily in the form of lymph nodes, which house in a sense the leukocytes. The leukocytes socialize through the body between the organs and nodes by means of the lymphatic vessels. Leukocytes can also circulate through your blood vessels. In this way, the immune system works in a well-coordinated manner, like your own personal army to monitor the body for germs or substances that might eventually cause problems.

The two basic types of leukocytes are:

1. Phagocytes, which are cells that masticate invading organisms.

2. Lymphocytes, which are cells that allow the body to remember and continually recognize previous invaders and help the body destroy them.

Several different cells are considered to be phagocytes. The most common type is the neutrophil, which mainly fights bacteria. If doctors are worried about a bacterial infection, they might order a blood test to see if a patient has an increased number of neutrophils triggered by an infection. Other types of phagocytes have their own specific jobs to make sure that the body responds properly to a specific type of invader.

There are two kinds of specific lymphocytes: the B-lymphocytes and the T- lymphocytes. Lymphocytes start out in the bone marrow and either hibernate there in a sense and mature into B cells, or they leave for the thymus gland, where they mature into T cells. B-lymphocytes and T-lymphocytes have separate jobs to do. For example, B-lymphocytes are like the body’s military intelligence team, covertly seeking out their targets and sending defenses to lock onto them and kill. T cells are like the little soldiers, destroying the invaders that the intelligence team has identified.

Here’s how it works:

Antigens are foreign substances that invade the body. When an antigen is detected, numerous types of cells work together to recognize and respond to it. These cells trigger the B-lymphocytes to produce antibodies, which are specialized proteins that lock onto specific antigens. Antibodies and antigens fit together like a lock and key. Once the B-lymphocytes have produced antibodies, these antibodies continue to exist in a person’s body, so that if the same antigen is presented to the immune system at another time, the antibodies are already there to do their job and fight the antigens. That is why if someone gets sick with a certain disease, like chickenpox for example, that person typically does not get it again. This is also why we use immunizations to avert getting certain diseases. The immunization introduces the body to the antigen in a way that doesn’t make a person sick, but it does allow the body to manufacture antibodies that will then protect that person from future attack by the germ or substance that produces that particular disease. Although antibodies can recognize an antigen and lock onto it, they are not capable of destroying it without assistance. This is where the job of the T cells come into play. The T cells are part of the system that destroys antigens that have been tagged by antibodies or cells that have been infected or somehow changed. (There actually are T cells that are referred to as “killer cells.”) T cells are also involved in helping signal other cells (like phagocytes) to do their specific duties. Antibodies can also neutralize toxins (poisonous or damaging substances) produced by different organisms. Lastly, antibodies can activate a group of proteins that are also part of the immune system. They are called complement; they assist in killing bacteria, viruses, or infected cells.

All of these specialized cells and parts of the immune system offer the body protection against disease and infection. This particular protection is called immunity.

Humans have three types of immunity — innate, adaptive, and passive:

Innate Immunity:
Everyone is born with innate (or natural) immunity, a type of general protection that all humans have. Many of the germs that affect other species do not harm us. For example, the viruses that cause leukemia in cats or distemper in dogs don’t affect humans. Innate immunity works both ways because some viruses that make humans ill, such as the virus that causes HIV/AIDS, don’t make cats or dogs sick either.

Innate immunity also includes the external barriers of the body, like the skin and mucous membranes (like those that line the nose, throat, and gastrointestinal tract), which are our first line of defense in preventing diseases from entering the body. If this outer defensive wall is broken (like if you get a cut), the skin attempts to heal the break quickly and special immune cells on the skin attack invading germs.

Adaptive Immunity:
We have a second kind of protection called adaptive (or active) immunity. This type of immunity develops in time throughout our lifespan. Adaptive immunity involves the lymphocytes (as in the process described above) and develops as children and adults are exposed to diseases or immunized against diseases through vaccination.

Passive Immunity:
Passive immunity is in a sense “borrowed” from another source and it lasts for only a short period of time. For example, antibodies in a mother’s breast milk provide an infant with temporary immunity against diseases that the mother has been exposed to. This can help defend the infant against infection during the early years of childhood. Everyone’s immune systems are different. Some people never seem to get infections, whereas others seem to be sick all the time. As people get older, they usually become immune to more germs as the immune system comes into contact with more and more of them. That’s why adults and teens tend to get fewer colds than children because their bodies have learned to recognize and immediately attack many of the viruses that cause the common cold.

Things That Can Go Wrong With the Immune System

Disorders of the immune system can be broken down into four main categories:

1. Immunodeficiency disorders – primary or acquired disorders.

2. Autoimmune disorders – in which the bodies own immune system attacks its own tissue such as it would foreign matter.

3. Allergic disorders – in which the immune system overreacts in response to an outside antigen.

4. Cancers of the immune system.

Immunodeficiency Disorders:
Immunodeficiencies occur when a part of the immune system is not present or is not working appropriately. Sometimes a person is born with an immunodeficiency; these are called primary immunodeficiencies. Although primary immunodeficiencies are conditions that a person is born with, symptoms of the disorder sometimes may not show up until later on in life. Immunodeficiencies can also be acquired through infection or produced by drugs. (These are sometimes referred to as secondary immunodeficiencies.) Immunodeficiencies can affect B-lymphocytes, T-lymphocytes, or phagocytes. Acquired immunodeficiencies usually develop after a person has a disease, but can also be the result of malnutrition, burns, or other medical problems with that person. Certain medicines also can cause problems with the functioning of the immune system.

Immunodeficiencies caused by medications
Some medicines intentionally suppress the immune system. One of the drawbacks of chemotherapy treatment, for example, is that it not only attacks cancer cells, but other fast-growing, healthy cells, including those found in the bone marrow and other parts of the immune system. In addition, people with autoimmune disorders or who have had organ transplants may need to take immunosuppressant medications. These medicines can also reduce the immune system’s ability to fight infections and can cause secondary immunodeficiency.

Autoimmune Disorders:

In autoimmune disorders, the immune system mistakenly attacks the body’s healthy organs and tissues as though they were foreign invaders.

Autoimmune diseases include:

· Lupus – which is a chronic disease marked by muscle and joint pain as well as inflammation. The abnormal immune response may also involve attacks on the kidneys and other organs.

· Juvenile rheumatoid arthritis – this is a disease in which the body’s immune system acts as though certain body parts such as the joints of the knee, hand, and foot are foreign tissue and attacks them.

· Scleroderma – which is a chronic autoimmune disease that can lead to the inflammation and damage of the skin, joints, and internal organs.

· Ankylosing spondylitis – this is a disease that involves inflammation of the spine and joints, causing stiffness and severe pain.

· Juvenile dermatomyositis – which is a disorder marked by the inflammation and damage of the skin and muscles.

Allergic Disorders:

Allergic disorders occur when the immune system overreacts to the exposure of antigens in the environment. The substances that provoke such attacks are called allergens. The immune response can cause symptoms such as swelling, watery eyes, and sneezing, and even a life-threatening reaction called anaphylaxis. Taking medications called antihistamines can relieve most, but not all symptoms.

Allergic disorders include:

· Asthma – which is a respiratory disorder that can cause, breathing problems, and frequently involves an allergic response by the lungs. If the lungs are oversensitive to certain allergens (like pollen, molds, animal dander, or dust mites), it can trigger breathing tubes in the lungs to become narrowed, leading to reduced airflow and making it harder for a person to breathe.

· Eczema – this is an itchy rash also known as atopic dermatitis. Although atopic dermatitis is not necessarily caused by an allergic reaction, it more often occurs in kids and teens who have allergies, hay fever, or asthma or who have a family history of these conditions.

· Allergies of several types can occur in kids and teens. Environmental allergies (to dust mites, for example), seasonal allergies (such as hay fever), drug allergies (reactions to specific medications or drugs), food allergies (such as to nuts), and allergies to toxins (bee stings, for example) are the common conditions people usually refer to as allergies.

Cancers of the Immune System:

Cancer occurs when cells grow out of control. This can also happen with the cells of the immune system. Lymphoma involves the lymphoid tissues and is one of the more common childhood cancers. Leukemia, which involves abnormal overgrowth of leukocytes, is the unfortunately the most common childhood cancer. With current medications most cases of both types of cancer in kids and teens are curable.

Although immune system disorders usually cannot be prevented, you can help your immune system stay stronger and fight illnesses by staying informed about your condition(s) and working closely with your doctor.

Staff – Everythingantiaging.com

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