Canadian Medical Guide > Biological Sciences > Biological Phenomena, Cell Phenomena, and Immunity > Immunity > Immune Tolerance Terms and Definitions

Immune Tolerance

Medical Definition:	The specific failure of a normally responsive individual to make an immune response to a known antigen. It results from previous contact with the antigen by an immunologically immature individual (fetus or neonate) or by an adult exposed to extreme high-dose or low-dose antigen, or by exposure to radiation, antimetabolites, antilymphocytic serum, etc.
Guide Notes:	do not confuse X ref IMMUNOSUPPRESSION (PHYSIOLOGY) with the Cat E immunol technique IMMUNOSUPPRESSION: Manual 28.21.1
Also Called:	Immunosuppression (Physiology)

Immune Tolerance Categories.

	Clonal Anergy - Functional inactivation of T- or B-lymphocytes rendering them incapable of eliciting an immune response to antigen. This occurs through different mechanisms in the two kinds of lymphocytes and can contribute to SELF TOLERANCE.
	Clonal Deletion - Removal, via CELL DEATH, of immature lymphocytes that interact with antigens during maturation. For T-lymphocytes this occurs in the thymus and ensures that mature T-lymphocytes are self tolerant. B-lymphocytes may also undergo clonal deletion.
	Self Tolerance - The normal lack of the ability to produce an immunological response to autologous (self) antigens. A breakdown of self tolerance leads to autoimmune diseases. The ability to recognize the difference between self and non-self is the prime function of the immune system.
	Tachyphylaxis - Rapidly decreasing response to a drug or physiologically active agent after administration of a few doses. In immunology, it is the rapid immunization against the effect of toxic doses of an extract or serum by previous injection of small doses. (Dorland, 28th ed)
	Transplantation Tolerance - An induced state of non-reactivity to grafted tissue from a donor organism that would ordinarily trigger a cell-mediated or humoral immune response.

Immune Tolerance Medical Definitions and Terms

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