immunologic tolerance
an immune response consisting of the development of specific nonreactivity of the lymphoid tissues to a given antigen that in other circumstances can induce cell-mediated or humoral immunity; it results from previous contact with the antigen and has no effect on the response to non–cross-reacting antigens. Tolerance is readily induced by administration of antigen to immunologically immature animals (fetuses, neonates). In adults tolerance may be induced by repeated administration of very large doses of antigen (high-dose or high-zone t.), or of small doses that are below the threshold required for stimulation of an immune response (low-dose or low-zone t.). Tolerance is most readily induced by soluble antigens administered intravenously; immunosuppression also facilitates the induction of tolerance.
Medical dictionary.
2011.