Immunodeficiency disorders

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Antibodies

Immunodeficiency disorders

Definition:

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

Alternative Names:
Immunosuppression
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.

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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 into2 groups: T lymphocytes and B lymphocytes.

T lymphocytes become the sensitized lymphocytes that directly attack antigens (cellular immunity ).
B lymphocytes produce antibodies (humoral immunity) that attach to the antigen and make phagocytes and body chemicals, such as complement proteins, much more efficient in the destruction of the antigen.

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.