Your immune system is your body's defense against germs and other invaders. Without it, bacteria or viruses would run rampant through your body.
Your immune system is made up of special cells, tissues, and organs that work together to protect you.
The lymph, or lymphatic, system is a major part of the immune system. It's a network of lymph nodes and vessels. Lymphatic vessels are thin tubes that branch, like blood vessels, into all the tissues of the body. They carry a clear fluid called lymph. Lymph contains tissue fluid, waste products, and immune system cells. Lymph nodes are small, bean-shaped clumps of immune system cells that are connected by lymphatic vessels. They contain white blood cells that trap viruses, bacteria, and other invaders, including cancer cells.
White blood cells are the cells of the immune system. They are made in one of your lymph organs, the bone marrow. Other lymph organs include the spleen and thymus.
When your immune system doesn't work the way it should, it is called an immune system disorder. You could have an immune system disorder if any of these happen:
You are born with a weak immune system.
You get a disease that weakens your immune system
Your immune system is too active.
Your immune system turns against you, a condition called autoimmune disease.
Having an immune system that is too weak is called an immunodeficiency disorder. If it is something you are born with, it is called primary immunodeficiency. If it is something that you develop later, it is called acquired immunodeficiency.
Here are some common examples:
Severe combined immunodeficiency (SCID). This is an example of an immune deficiency that children are born with. It puts them in constant danger of infections from bacteria, viruses, and fungi. This disorder is sometimes called "bubble boy disease" because of the widely reported story of a boy in the 1970s who had to live in a sterile environment inside a plastic bubble. Children with SCID are threatened with constant infection because they are missing important white blood cells.
Temporary acquired immune deficiencies. You can get a weakened immune system if you are exposed to certain drugs, including those used to fight cancer. If you need an organ transplant, you might be put on drugs that block, or suppress, your immune system to keep you from rejecting the transplant. Common infections like the flu virus, mononucleosis (mono), and measles can also weaken your immune system for a brief time. Your immune system can also be weakened by smoking and poor nutrition.
AIDS. HIV, which causes AIDS, is an acquired infection that can destroy important white blood cells. If you have HIV/AIDS, an infection that people with a healthy immune system would be able to fight off can make you dangerously ill. These infections are called "opportunistic infections" because they take advantage of a weak immune system.
If you are born with certain genes, your immune system may react to substances in your environment that are normally harmless. These substances are called allergens. Having an allergic reaction is the most common example of an overactive immune system. Allergens could be particles of dust, mold, animal dander, or a food that you eat.
Here are some examples:
Asthma. This overactive immune response in your lungs can cause coughing, wheezing, and trouble breathing. Asthma can be triggered by a common allergen like dust mites or by an irritant like tobacco smoke, a viral infection, or even by exercise.
Eczema. Your immune system could overreact to an allergen by causing an itchy rash known as atopic dermatitis.
Allergic rhinitis. Sneezing, sniffling, and swelling of your nasal passages can be caused by indoor allergens like dust and pet danders or outdoor allergens like pollens or molds.
Imagine your immune system as a police force that starts arresting the good guys instead of the bad guys. That's similar to what happens when you have an autoimmune disease: Your body makes T cells, a type of white blood cell, and proteins called auto-antibodies that start to attack normal, healthy tissues. The exact cause of autoimmune diseases is not known, but is probably a combination of genes you are born with and something that triggers those genes in your environment.
Here are three common autoimmune diseases:
Type 1 diabetes. In this disease, T cells start to attack the cells in your pancreas that make insulin. Without insulin you can't remove sugar from your blood to use as energy. If you have this autoimmune disease, you may need to take insulin by injection for the rest of your life.
Rheumatoid arthritis. This disease causes swelling and deformities of the joints. An auto-antibody called rheumatoid factor can be found in the blood of some people with rheumatoid arthritis.
Lupus. Systemic lupus erythematosis is an autoimmune disease that attacks many types of body tissues including lung, kidney, and skin. Many types of auto-antibodies are found in people with lupus.
No one knows exactly what causes autoimmune diseases, but many factors seem to be involved. Disorders of your immune system can have many symptoms, but many different treatments can help. If you have an immune system disorder, learn as much as you can about your illness and work closely with your doctors to manage it. Many of these disorders can be treated.