Immunodeficiency disorders

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Antibodies

Immunodeficiency disorders may affect any part of the immune system. Most commonly, this involves decreased functioning of T or B lymphocytes (or both), or deficient antibody production. The causes include congenital (inherited) defects and acquired immunodeficiency caused by a disease that affects the immune system.

Examples of congenital immunodeficiency disorders of antibody production (B lymphocyte abnormalities) include hypogammaglobulinemia (lack of one or more specific antibodies) -- which usually causes repeated mild respiratory infections, and agammaglobulinemia (lack of all or most antibody production) -- which results in frequent severe infections and is often fatal.

Congenital disorders affecting the T lymphocytes may cause increased susceptibility to fungi, resulting in recurring candida (yeast) infections. Inherited combined immunodeficiency affects both T lymphocytes and B lymphocytes. It may be fatal within the first year of life if it isn't treated early, because there is no resistance to disease or infection.

People are said to be immunosuppressed when they experience immunodeficiency that is caused by drugs such as corticosteroids or other immunosuppressant medications. This is a desired part of treatment for disorders such as autoimmune disorders, or after organ transplantation to prevent transplant rejection.

Immunosuppression is also a common side-effect of chemotherapy to treat many types of cancer, because the chemotherapy often reduces the number of white blood cells available to fight infection.

Acquired immunodeficiency may be a complication of diseases such as HIV infection and AIDS (acquired immunodeficiency syndrome). Malnutrition, particularly with lack of protein, and many cancers, may also cause immunodeficiency.

Those who have had a splenectomy (spleen removal) face a higher risk of infection from certain encapsulated bacteria that the spleen would normally help fight. Patients with diabetes are also at higher risk for certain infections.