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Definition of Immune tolerance

Immune tolerance: A state of unresponsiveness to a specific antigen or group of antigens to which a person is normally responsive. Immune tolerance is achieved under conditions that suppress the immune reaction and is not just the absence of a immune response.

Immune tolerance can result from a number of causes including:

  • Prior contact with the same antigen in fetal life or in the newborn period when the immune system is not yet mature;
  • Prior contact with the antigen in extremely high or low doses;
  • Exposure to radiation, chemotherapy drugs, or other agents that impair the immune system;
  • Heritable diseases of the immune system;
  • Acquired diseases of the immune system such as HIV/AIDS.

Immune tolerance can be defined as a state in which a T cell can no longer respond to antigen. The T cell "tolerates" the antigen.

Source: MedTerms™ Medical Dictionary
http://www.medterms.com/script/main/art.asp?articlekey=10101
Last Editorial Review: 6/14/2012

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