Immunodeficiency disorders occur when the body's immune response is reduced or absent.

See also: Autoimmune disorders

The immune system is made up of lymphoid tissue in the body, which includes the bone marrow, lymph nodes, thymus, tonsils, and parts of the spleen and gastrointestinal tract.

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 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.

Immune system disorders occur when the immune system does not fight tumors or harmful substances as it should. The immune response may be over active or under active.

Immunodeficiency disorders may affect any part of the immune system. Most commonly, such a condition occurs when specialized 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 causes mild to moderate respiratory infections
• Agammaglobulinemia, which results in frequent severe infections and is often deadly

Inherited immunodeficiency disorders that affect T cells 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 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 affect the immune system (such as corticosteroids). Immunosuppression is also a common side effect of chemotherapy.

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.

Persons who have had their spleen removed are at higher risk for from certain bacteria that the spleen would normally help fight. Patients with diabetes are also at higher risk for certain infections.

Increasing age reduces the effectiveness of the immune system to some degree. Immune system tissues (particularly lymphoid tissue such as the thymus) shrink, and the number and activity of white blood cells drop.

The following conditions and diseases can result in an immunodeficiency disorder:

• Ataxia-telangiectasia
• DiGeorge syndrome
• Chediak-Higashi syndrome
• Job syndrome
• Leukocyte adhesion defects
• Panhypogammaglobulinemia
  • Bruton disease
  • Congenital agammaglobulinemia
• Selective deficiency of IgA
• Combined immunodeficiency disease
• Wiscott-Aldrich syndrome
• Complement deficiencies
• Hypogammaglobulinemia

The symptoms vary with the specific disorder.

Persistent, recurrent infections, or severe infection by microorganisms that do not usually cause severe infection, may be a sign that an immunodeficiency disorder is present. Other signs include:

• Poor response to treatment
• Delayed or incomplete recovery from illness
• Certain types of cancers (such as Kaposi's sarcoma or non-Hodgkin's lymphoma)
• Certain infections (such as pneumocystis carinii pneumonia or recurrent fungal yeast infections)

Tests used to help diagnose an immunodeficiency disorder may include:

• White blood cell count
• Antibody/immunoglobulin levels
• T (thymus derived) lymphocyte count
• Complement levels or other measurements of immune-response components

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.

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.

• Disease development
• Frequent or persistent illness
• Opportunistic infections
• Increased risk for certain cancers/tumors

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.

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.

Bonilla FA, Bernstein IL, Khan DA, et al. Practice parameter for the diagnosis and management of primary immunodeficiency. Ann Allergy Asthma Immunol. 2005 May;94(5 Suppl 1):S1-63.