delayed hypersensitivity reaction


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delayed hypersensitivity reaction

A localized skin response mediated by T cells, which occurs 24 to 72 hr after injection of a specific antigen to which the person has been previously sensitized. It is used routinely to screen for tuberculosis infection through injection of purified protein derivative of Mycobacterium tuberculosis. In patients with immunodeficiency, common microbial antigens to which most people have been exposed, such as diphtheria, tetanus, measles, or Candida, are used to determine the presence of defects in T-cell–mediated immunity (CMI). If patients do not develop induration at the site, indicating a positive response to the antigen, a CMI defect is present. Delayed hypersensitivity is a type IV hypersensitivity reaction mediated by cytokines released by macrophages and helper T cells.
Synonym: nonimmediate allergic reaction
References in periodicals archive ?
This type of delayed hypersensitivity reaction would also not be expected to predispose to anaphylaxis.
We conducted a prospective study of 60 patients in a tertiary care referral center to ascertain the status of cell-mediated immunity as determined by delayed hypersensitivity reactions in patients with nasopharyngeal carcinoma (NPC) or allergic rhinitis.
Various immunosuppressive mechanisms are implicated in the depression of delayed hypersensitivity reaction during active tuberculosis infection.
None of those 20 patients were observed to have developed immediate or delayed hypersensitivity reactions, investigators reported.
Delayed hypersensitivity reactions are also possible, characterized by erythema, edema, itching, a change in the contour of the injected implant, and, occasionally, an indurated papule or inflamed dermal nodule, but they are very rare after HA application.

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