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Immunodeficiency disordersDefinition Immunodeficiency disorders occur when the immune response is reduced or absent. Causes, incidence, and risk factors The immune system protects the body from potentially harmful substances (antigens ) such as microorganisms, toxins, cancer cells, and blood or tissues from another person. The immune response consists of general actions, such as phagocytosis, in which white blood cells engulf and destroy foreign material. It also protects against specific antigens by producing antibodies (immunoglobulins), which are molecules that attach to a specific antigen and make destruction of the antigen more efficient. Lymphocytes, a group of white blood cells, become specialized or sensitized. The sensitized lymphocytes recognize and destroy the foreign substance. The immune system is made up of lymphoid tissue in the body, including the thymus, lymph nodes, tonsils, parts of the spleen and gastrointestinal tract, and bone marrow. Lymphocytes (the specialized white blood cells that provide acquired immunity) are produced or mature in various lymphoid tissues. Lymphocytes are divided into 2 groups: T lymphocytes and B lymphocytes.
Immune system disorders occur when the immune response is inappropriate (excessive or lacking). Immunodeficiency disorders occur when the immune system fails to fight tumors or invading substances. Immunodeficiency causes persistent or recurrent infections, severe infections by organisms that are normally mild, incomplete recovery from illness or poor response to treatment, and an increased incidence of cancer and other tumors. Opportunistic infections are widespread infections by microorganisms that are usually controllable. 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. Increasing age also reduces the effectiveness of the immune system to some degree. Immune system tissues (particularly lymphoid tissue such as the thymus) shrink, and there is also reduced lymphocyte number and activity. The following list contains conditions and diseases that can result in an immunodeficient state:
Symptoms The symptoms vary with the specific disorder. Signs and tests Persistent, recurrent infections, or severe infection by microorganisms that do not usually cause severe infection, may be clues that an immunodeficiency disorder is present. Other clues include:
Other tests may be indicated to confirm specific immunodeficiency disorders. Treatment Usually, the immune response is a desired effect. Even deliberate immunosuppression (in the treatment of autoimmune disorders or organ transplant, for example) attempts to maintain a balance between suppression of parts of the immune system and the ability to fight disease and infection. The goal of treatment for immunodeficiency disorders includes protection against (and treatment of) diseases and infections. Immunocompromised patients should avoid contact with persons who have infections or contagious disorders. This may include avoiding people who have been immunized with live virus vaccines within the past two weeks. Any illness or infection is treated aggressively in patients with immunosuppression. This may involve prolonged use of antimicrobials (antibiotics, antifungal medications), use of powerful antimicrobials to treat any infection, and preventive (prophylactic) treatments. Interferon (used to treat viral infections and some types of cancer) and Zidovudine (AZT, used to treat AIDS) are 2 immunostimulant drugs (medications that increase the efficiency of the immune system). Persons with HIV and AIDS may take combinations of drugs to reduce the amount of virus in their immune systems, thus improving their immunity. Patients undergoing a planned splenectomy should be vaccinated 2 weeks prior to the surgery against encapsulated organisms, such as streptococcal pneumonia. Bone marrow transplant may be used to treat certain immunodeficiency conditions. Passive immunity (administration of antibodies produced by another person or animal) may occasionally be recommended to prevent illness after exposure to a microorganism. Expectations (prognosis) Some immunodeficiency disorders are mild and result in occasional illness. Others are severe and may be fatal. Immunosuppression that results from medications is often reversible once the medication is stopped. Complications
Calling your health care provider Call your health care provider immediately if you are taking immunosuppressive drugs (for instance, chemotherapy or prednisone), and you develop a fever greater than 100.5 degrees F, or have cough with shortness of breath. If a stiff neck and headache accompany your fever, go directly to an emergency department. Contact your health care provider if you have recurrent yeast infections or oral thrush. Prevention There is no known prevention for congenital immunodeficiency disorders. Safe sex practices and avoiding the sharing of body fluids may help to prevent HIV infection and AIDS. Good nutrition may prevent acquired immunodeficiency caused by malnutrition. Illustrations
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