Immune Deficiency Disorders

Reviewed by Ann Mullen, RN, CNS, AE-C, CDE, TTS
The immune system protects the body from infection. When the immune system cannot protect the body from infection as well as it should, the immune system is considered deficient.

Therefore, an immune deficiency disorder is defined as a state in which the immune system cannot protect the body from infection as well as it should.

People who have immune deficiency disorders can catch frequent or unusual infections that people with normal immune systems are less likely to catch.

In some cases, an immune deficiency is present at the time of birth and persists throughout life (primary immunodeficiency). In other cases, an immune deficiency appears later in life, either during childhood or adulthood (secondary immunodeficiency). Some of these cases are caused by genetic factors and some are the result of other problems, such as autoimmune disease, cancer or medications.

Each type of immune deficiency is different, and not all immune deficiencies are treated in the same way. It is important to find out as much as possible about your specific immune deficiency to understand the types of infection that you may be more susceptible to getting. You and your doctor can work together to prevent the infections that your immune system has trouble preventing.


How the Immune System Works

The immune system normally protects your health by recognizing “foreign invaders” like bacteria, viruses, parasites and fungi and then figuring out a way to remove them from the body. The immune system isn’t located in just one part of the body. The cells of the immune system can move around to anywhere in the body. Some of the places where immune cells are present in high numbers include the thymus, liver, bone marrow, tonsils, lymph nodes, spleen and blood. These places in the body help make, store and transport the cells and proteins that fight foreign invaders.

The major cells and proteins of the immune system are:

  • B-Cells (also called B-lymphocytes)

  • T-Cells (also called T-lymphocytes)

  • Phagocytes — “Eater Cells”

  • Antigen Presenting Cells — “Recognizer Cells”

  • Killer Cells

  • Antibodies — Special proteins in the blood

  • Complement — Another group of proteins in the blood



B-cells make antibodies, also called immunoglobulins or gamma globulins. Antibodies are sent through the blood to all parts of the body to fight infection. 



Antibodies surround and coat the cells of foreign invaders. This weakens the invader cells. Some examples of antibodies are IgM, IgG and IgA. IgM antibodies travel to the site of infection when it first begins. IgG antibodies are found in the blood and tissues. IgA antibodies are in secretions like tears, saliva, mucus and gastric juices. Antibodies are made by B-cells.



Three kinds of T-cells travel in the blood to infected areas. Helper T-cells tell the immune system when more help is needed. Killer T-cells attack foreign invaders like infectious organisms. Regulatory T-cells tell the immune system that something should be ignored, like your own body parts.



Phagocytes are in the blood and tissues. They eat and kill foreign invaders. Phagocytes send chemical signals to other phagocytes and help make complement. When antibodies and/or complement have coated the foreign invaders, it is easier for phagocytes to eat them.



Complement is made up of 18 proteins in the blood. The presence of foreign invaders and antibodies tells complement to begin its work. Like antibodies, complement coats foreign invaders so that they are easier for phagocytes to kill and eat. Complement also sends signals to phagocytes when more are needed.

B-cells, T-cells, phagocytes, antibodies and complement all work together in a complex system to protect us. That’s what makes the immune system a system. 


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