What Does The Immune System Do?
Your body is constantly under attack from things that are trying to do it harm such as toxins, bacteria, fungi, parasites and viruses.
The purpose of the immune system is to act as your body’s army and defend against this constant stream of invaders.
What Makes Up The Immune System?
The immune system is made up of a network of cells, tissues, and organs that work together to protect the body against invaders.
The cells involved are white blood cells, or leukocytes, which seek out and destroy disease-causing organisms or substances.
Leukocytes are produced by bone marrow and are also stored in many locations in the body, including the thymus, spleen, lymph nodes and Peyer’s Patches (which protect the interior of the intestines).
The leukocytes circulate through the body between the organs and nodes via lymphatic vessels and blood vessels.
There are two basic types of leukocytes:
There are a number of different phagocyte cells. The most common type is the neutrophil which primarily fights bacteria. Other types of phagocytes have their own jobs to make sure the body responds appropriately to a specific type of invader.
The two kinds of lymphocytes are B lymphocytes and T lymphocytes. Lymphocytes start out in the bone marrow and either stay there 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 functions: B lymphocytes are like the body’s military intelligence system, seeking out their targets and sending defenses to lock onto them. T cells are like the soldiers, destroying the invaders that the intelligence system has identified.
It is the lymphocytes that allow your body to recognize previous invaders and to help destroy them if they reappear.
Your immune system also includes your Adenoids and your Tonsils, which trap harmful bacteria and viruses that you breathe in or swallow.
How Does The Immune System Work?
When pathogens (organisms capable of producing disease) attempt to get into the body, they first must get past the body’s external armor, mainly the skin or cells lining the body’s internal passageways.
The skin provides an imposing barrier to invading microbes. It is generally penetrable only through cuts or abrasions.
The digestive and respiratory tracts — both portals of entry for a number of pathogens — also have their own protection. Pathogens entering the nose often cause the nasal surfaces to secrete more protective mucus, and attempts to enter the nose or lungs can trigger a sneeze or cough reflex to force microbial invaders out of the respiratory passageways. In addition, the stomach contains a strong acid that destroys many pathogens that are swallowed with food.
If pathogens survive the body’s front-line defenses, they still have to find a way through the walls of the digestive, respiratory, or urogenital passageways to the underlying cells. These passageways are lined with tightly packed epithelial cells covered in a layer of mucus, effectively blocking the transport of many pathogens into deeper cell layers
Mucosal surfaces also secrete a special class of antibody called IgA, which in many cases is the first type of antibody to encounter an invading pathogen.
When pathogens are detected by your body, several types of cells work together to recognize them and respond. These cells trigger the B lymphocytes to produce antibodies, specialized proteins that lock onto specific antigens (proteins on the surface of pathogens).
Once produced, these antibodies continue to exist in a person’s body, so that if the same antigen is presented to the immune system again, the antibodies are already there to do their job. So if someone gets sick with a certain disease, like chickenpox, that person typically doesn’t get sick from it again.
This is also how immunizations prevent certain diseases. An immunization introduces the body to an antigen in a way that doesn’t make someone sick, but does allow the body to produce antibodies that will then protect the 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 help. That’s the job of the T cells, which are part of the system that destroys antigens that have been tagged by antibodies or cells that have been infected or somehow changed. (Some T cells are actually called “killer cells.”) T cells also are involved in helping signal other cells (like phagocytes) to do their jobs.
Antibodies also can neutralize toxins (poisonous or damaging substances) produced by different organisms. Lastly, antibodies can activate a group of proteins called complement that are also part of the immune system. Complement assists in killing bacteria, viruses, or infected cells.
All of these specialized cells and parts of the immune system offer the body protection against disease. This 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. Many of the germs that affect other species don’t 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.
- Adaptive Immunity
The second kind of protection is adaptive (or active) immunity, which develops throughout our lives. Adaptive immunity involves the lymphocytes and develops as people are exposed to diseases or immunized against diseases through vaccination.
- Passive Immunity
Passive immunity is “borrowed” from another source and it lasts for a short time. For example, antibodies in a mother’s breast milk provide a baby with temporary immunity to diseases the mother has been exposed to. This can help protect the baby against infection during the early years of childhood.
What Can Go Wrong With Your Immune System?
The most common types of allergic diseases occur when the immune system responds to a false alarm. In an allergic person, a normally harmless material such as grass pollen, food particles, mold, or house dust mites is mistaken for a threat and attacked.
Sometimes the immune system’s recognition apparatus breaks down, and the body begins to manufacture T cells and antibodies directed against its own cells and tissues. As a result, healthy cells and tissues are destroyed.
Misguided T cells and autoantibodies, as they are known, contribute to many autoimmune diseases. For instance, T cells that attack certain kinds of cells in the pancreas contribute to a form of diabetes, whereas an autoantibody known as rheumatoid factor is common in people with rheumatoid arthritis. People with systemic lupus erythematosus (SLE) have antibodies to many types of their own cells and cell components.
Immune Complex Diseases
Immune complexes are clusters of interlocking antigens and antibodies. Normally, immune complexes are rapidly removed from the bloodstream. Sometimes, however, they continue to circulate and eventually become trapped in the tissues of the kidneys, lungs, skin, joints, or blood vessels. There, they set off reactions with complement that lead to inflammation and tissue damage. Immune complexes work their mischief in many diseases including malaria and viral hepatitis, as well as many autoimmune diseases.
Immune Deficiency Disorders
When the immune system is missing one or more of its parts, the result is an immune deficiency disorder. These disorders can be inherited, acquired through infection, or produced as a side effect by drugs such as those used to treat people with cancer or those who have received transplants.
Temporary immune deficiencies can develop in the wake of common virus infections, including influenza, infectious mononucleosis, and measles. Immune responses can also be depressed by blood transfusions, surgery, malnutrition, smoking, and stress.
AIDS (acquired immunodeficiency syndrome) is an immune deficiency disorder caused by a virus (HIV) (human immunodeficiency virus) that infects immune cells. HIV can destroy or disable vital T cells, paving the way for a variety of immunologic shortcomings. The virus also can hide out for long periods in immune cells. As the immune defenses falter, a person develops AIDS and falls prey to unusual, often life-threatening infections and rare cancers.
How Do Your Keep Your Immune System Healthy?
To keep your Immune system healthy, follow these 3 rules:
- Eat a healthy and well-balanced diet. A well-balanced diet with healthy proteins, complex carbohydrates, and good fats can effectively boost your immune system.
- Exercise. Exercise decreases your chance of infection by slowing the release of the stress hormone cortisol.
- Wash your hands regularly. Proper hand washing is the most effective barrier against the spread of infectious diseases. This article explains the proper way to wash your hands. There is even a video.
This article is part of a series called “Your Body: An Owner’s Manual” which explains how your body systems work and how to maintain them. The first article in the series included a picture of my wife, fitness coach Kathie Lamir, who exemplifies a healthy body. Pictures of Kathie were so well received that I have included one with each article in the series