cell-mediated hypersensitivity

hypersensitivity /hy·per·sen·si·tiv·i·ty/ (-sen″sĭ-tiv´ĭ-te) a state of altered reactivity in which the body reacts with an exaggerated immune response to what is perceived as a foreign substance. The hypersensitivity states and resulting reactions are usually subclassified by the Gell and Coombs classification (q.v.).hypersen´sitive

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antibody-mediated hypersensitivity 

1. type II h.; see Gell and Coombs classification, under classification.

2. occasionally, any form of hypersensitivity in which antibodies, rather than T lymphocytes, are the primary mediators, i.e., types I–III.

cell-mediated hypersensitivity  type IV h.; see Gell and Coombs classification, under classification.

contact hypersensitivity  a type IV hypersensitivity produced by contact of the skin with a chemical substance having the properties of an antigen or hapten.

cytotoxic hypersensitivity  type II h.; see Gell and Coombs classification, under classification.

delayed hypersensitivity  (DH), delayed-type hypersensitivity (DTH) that which takes 24 to 72 hours to develop and is mediated by T lymphocytes rather than by antibodies; usually used to denote the subset of type IV hypersensitivity involving cytokine release and macrophage activation, as opposed to direct cytolysis, but sometimes used more broadly, even as a synonym of type IV h.

immediate hypersensitivity 

1. type I h.; see Gell and Coombs classification, under classification.

2. occasionally, any form of hypersensitivity mediated by antibodies and developing rapidly, generally in minutes to hours (i.e., types I–III ), as distinguished from that mediated by T lymphocytes and macrophages and requiring days to develop (type IV, or delayed h. ).

immune complex–mediated hypersensitivity  type III h.; see Gell and Coombs classification, under classification.

T cell–mediated hypersensitivity  type IV h.; see Gell and Coombs classification, under classification.

type I hypersensitivity  see Gell and Coombs classification, under classification.

type II hypersensitivity  see Gell and Coombs classification, under classification.

type III hypersensitivity  see Gell and Coombs classification, under classification.

type IV hypersensitivity  see Gell and Coombs classification, under classification.

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cell-mediated hypersensitivity,

hypersensitivity initiated by antigen-specific T lymphocytes. Unlike forms of hypersensitivity mediated by antibodies, it takes one or more days to develop and can be transferred by lymphocytes but not by serum. The term is often equated with delayed hypersensitivity, although the latter is sometimes restricted to hypersensitivity involving cytokine-mediated reactions (as contrasted with direct cytolysis).

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cell-mediated

effected by cellular rather than chemical elements.

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cell-mediated hypersensitivity

see delayed hypersensitivity.

cell-mediated immunity

see cellular immunity.

cell-mediated lympholysis assay

a test of cell-mediated immunity in which activated cytoxic T lymphocytes cause lysis of ⁵¹Cr-labeled target cells.