The immune system is made up of lymphoid tissue in the body, which includes:
Bone marrow
Lymph nodes
Parts of the spleen and gastrointestinal tract
Thymus
Tonsils
Proteins and cells in the blood are also part of the immune system.
The immune system helps protect the body from harmful substances called antigens. Examples of antigens include bacteria, viruses, toxins, cancer cells, and foreign blood or tissues from another person or species.
When the immune system detects an antigen, it responds by producing proteins called antibodies that destroy the harmful substances. The immune system response also involves a process called phagocytosis. During this process, certain white blood cells swallow and destroy bacteria and other foreign substances. Proteins called "complements" help with this process.
Immune system disorders occur when the immune system does not fight tumors or harmful substances as it should. The immune response may be overactive or underactive.
Immunodeficiency disorders may affect any part of the immune system. Most commonly, these conditions occur when special white blood cells called T or B lymphocytes (or both) do not work as well as they should, or when your body doesn't produce enough antibodies.
Inherited immunodeficiency disorders that affect B cells include:
Hypogammaglobulinemia, which usually leads to respiratory and gastrointestinal infections
Agammaglobulinemia, which results in severe infections early in life, and is often deadly
Inherited immunodeficiency disorders that affect T cells may cause repeated Candida (yeast) infections. Inherited combined immunodeficiency affects both T cells and B cells. It may be deadly within the first year of life if it isn't treated early.
People are said to be immunosuppressed when they have an immunodeficiency disorder due to medicines that weaken the immune system (such as corticosteroids). Immunosuppression is also a common side effect of chemotherapy given to treat cancer.
Acquired immunodeficiency may be a complication of diseases such as HIV infection and malnutrition (especially if the person does not eat enough protein). Many cancers may also cause immunodeficiency.
People who have had their spleen removed have an acquired immunodeficiency, and are at higher risk for infection by certain bacteria that the spleen would normally help fight. Patients with diabetes are also at higher risk for certain infections.
As you get older, the immune system becomes less effective. Immune system tissues (especially lymphoid tissue such as the thymus) shrink, and the number and activity of white blood cells drop.
The following conditions and diseases can lead to an immunodeficiency disorder:
Ataxia-telangiectasia
Chediak-Higashi syndrome
Combined immunodeficiency disease
Complement deficiencies
DiGeorge syndrome
Hypogammaglobulinemia
Job syndrome
Leukocyte adhesion defects
Panhypogammaglobulinemia
Bruton disease
Congenital agammaglobulinemia
Selective deficiency of IgA
Wiscott-Aldrich syndrome
Symptoms
The symptoms depend on the disorder.
Signs and tests
Your doctor might think you have an immunodeficiency disorder if you have:
Infections that keep coming back or do not go away
Severe infection from bacteria or other germs that do not usually cause severe infection
The goal of treatment is to prevent infections and treat any disease and infections that do develop.
If you have a weakened immune system, you should avoid contact with persons who have infections or contagious disorders. You may have to avoid people who have been vaccinated with live virus vaccines within the past 2 weeks.
If you develop an infection, your doctor will treat you aggressively. This may involve long-term use of antibiotic or antifungal medications and preventive (prophylactic) treatments.
Interferon is used to treat viral infections and some types of cancer. It is an immunostimulant drug, a medicine that makes the immune system work better.
Persons with HIV or AIDS may take combinations of drugs to reduce the amount of HIV in their immune systems and improve their immunity.
Patients who are going to have a planned splenectomy should be vaccinated 2 weeks before the surgery against bacteria such as Streptococcus pneumonia and Hemophilus influenzae.
Passive immunity (receiving antibodies produced by another person or animal) may sometimes be recommended to prevent illness after you have been exposed to bacteria or other germs.
Patients with hypogammaglobulinemia are treated with immunoglobulin infusions through a vein. These infusions raise blood immunoglobulin levels ge and protect against many infections.
Expectations (prognosis)
Some immunodeficiency disorders are mild and cause illness from time to time. Others are severe and may be fatal. Immunosuppression caused by medications often goes away once the medication is stopped.
Complications
Frequent or persistent illness
Increased risk for certain cancers or tumors
Increased risk for infection
Calling your health care provider
Call your health care provider immediately if you are on chemotherapy or corticosteroids (such as prednisone, Medrol, or Decadron) and you develop:
A fever higher than 100.5 degrees Fahrenheit
A cough with shortness of breath
Stomach pain
Other new symptoms
Go to the emergency room if you have a stiff neck and headache with the fever.
Contact your health care provider if you have repeated yeast infections or oral thrush.
Prevention
There is no known way to prevent congenital immunodeficiency disorders. If you have a family history of immunodeficiency disorders, you might want to have genetic counseling.
Practicing safe sex and avoiding the sharing of body fluids may help prevent HIV infection and AIDS. Good nutrition may prevent acquired immunodeficiency caused by malnutrition.
Morimoto Y. Immunodeficiency overview. Prim Care. 2008;35:159-173.
Review Date:
5/6/2012
Reviewed By:
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; Stuart I. Henochowicz, MD, FACP, Associate Clinical Professor of Medicine, Division of Allergy, Immunology, and Rheumatology, Georgetown University Medical School. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.
