Immunosuppression
Key points
- Immunosuppression is a disorder or condition where the immune response is reduced or absent.
- The immune system protects the body from potentially harmful substances (antigens) such as microorganisms, toxins, cancer cells, and blood or tissues from another person.
- Persistent, recurrent infections, or severe infection by microorganisms that do not usually cause severe infection, may be clues that an immunodeficiency disorder is present.
- Even deliberate immunosuppression (in the treatment of autoimmune disorders for example) attempts to maintain a balance between suppression of parts of the immune system and the ability to fight disease and infection.
Alternative names
Immunodeficiency disorders
Definition
Immunosuppression is a disorder or condition where 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.
It also protects against specific antigens by producing lymphocytes (a group of white blood cells) that become specialized (sensitized). The sensitized lymphocytes recognize and destroy the foreign substance.
Immunity is a product of lymphoid tissue in the body which includes 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 two 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.
This 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.
The deficiency may affect any part of the immune system. Most commonly, it 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.
Written and revised by
Andrey Nailor, M.D.
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