About Immune Deficiencies

What is the function of the immune system?

The immune system has two major functions:

1. To recognize substances that are foreign to the body, and;
2. To react to them.

An immune system that is functioning adequately may defend the body against infectious microorganisms (bacteria, viruses, fungi and parasites) and protect the body from the development of tumors and cancer. The mechanisms within the body that provide these defenses are the specific immune response involving the T-cells, B-cells and antibodies (immunoglobulins), and the nonspecific responses involving phagocytes and complement.

Unfortunately, some individuals have a weakened or absent immune system that is unable to recognize and react to foreign substances. The immune system’s ability to kill invading microorganisms and limit the spread of infections may not be functioning well.

Learn more about the immune system and how it works.

What are Primary and Secondary Immune Deficiency Diseases?

An immune deficiency disease occurs when one or more cells within the immune system do not operate properly, or the system is absent altogether. Some immune deficiency diseases are relatively common, while others are extremely rare.

What is a primary immune deficiency?

A primary immune deficiency occurs when the abnormalities of the immune system develop from an inborn defect in the cells. Affected cells include T-cells, B-cells, phagocytic cells or the complement system.

Most primary immune deficiencies are inherited diseases; examples include X-linked agammaglobulinemia (XLA) and severe combined immunodeficiency (SCID), and this appears to run in families. Other primary immune deficiencies, such as common variable immunodeficiency (CVID), appear less obviously inherited, but the causes of the defects are unknown and genetic factors cannot be ruled out.

What is a secondary immune deficiency?

Secondary immune deficiencies occur when damage is caused by an environmental factor. Radiation, chemotherapy, burns and infections contribute to the many causes of secondary immune deficiencies. Acquired Immune Deficiency Syndrome (AIDS) is a secondary immune deficiency caused by the Human Immunodeficiency Virus (HIV) virus. In leukemia and multiple myeloma, cancerous immune cells crowd out the normal stem cells of the bone marrow. These abnormal cells reduce the number of B cells and lead to hypogammaglobulinemia, another type of secondary immune deficiency.

What are some common infections or issues associated with immune deficiency diseases?

Recurrent infections are the most common problems experienced by individuals with immune deficiencies.

• Recurrent sinus ( sinusitis) and chest (pneumonia, bronchitis) infections are quite common.  Early recognition and treatment of such infections are important to prevent permanent damage. Changes in color or amounts of sputum and nasal secretions may be early signs of infection. Antibiotic therapy is frequently required, usually for extended periods of time.
• Conjunctivitis (eyes that are red or ooze pus) is another condition frequently observed in individuals with immune deficiency diseases. In many cases, if the patient’s immune deficiency is treated monthly with gammaglobulin, the conjunctivitis improves, although additional antibiotics are sometimes needed.
• Diarrhea is a common problem of immune deficient patients. This is often caused by infections or an overgrowth of normal bacteria that live in the gastrointestinal tract. Stool samples should be obtained if a patient experiences pain, bloating or diarrhea. If the results are positive for organisms such as Giardia, antibiotic therapy is necessary.
• Methicillin Resistant Staphylococcus aureus infections (MRSA). While Staphylococcus aureus is a common bacteria (germ) that is normally present on the skin and in the nose of most people, it can cause opportunistic infections in people with suppressed immune systems. What's more, certain strains of this bacteria have become resistant to a common antibiotic (methicilin) used to treat these infections. MRSA is more difficult to treat because it is resistant to methicillin and must be treated with a different antibiotic. Learn more about MRSA including tips on how to prevent this infection

Don't understand a term your doctor used to describe an immune deficiency? Look through our Glossary of the Immune System to learn definitions for some common terms.

This information has been approved by Rafeul Alam, MD (March 2008).