Type IV Hypersensitivity
Type IV Hypersensitivity (pronunciation: /taɪp foʊr haɪ.pɚ.sɛn.sɪ.tɪv.ɪ.ti/), also known as Delayed Type Hypersensitivity (DTH), is a type of Immunological response that occurs due to the activation of T cells by Antigens. The term "Type IV Hypersensitivity" is derived from the Gell and Coombs classification of hypersensitivity reactions, where it is categorized as the fourth type.
Overview
Type IV Hypersensitivity is unique among the Hypersensitivity reactions as it is the only type that is mediated by T cells rather than Antibodies. It is characterized by a delayed response, typically occurring 48-72 hours after exposure to the antigen. This is in contrast to the immediate response seen in other types of hypersensitivity reactions.
Mechanism
The mechanism of Type IV Hypersensitivity involves the activation of T cells by antigens. These activated T cells then release Cytokines, which recruit and activate Macrophages. The activated macrophages cause tissue damage, leading to the symptoms of the hypersensitivity reaction.
Clinical Manifestations
Clinical manifestations of Type IV Hypersensitivity include Contact dermatitis, Tuberculin skin test reaction, and Granulomatous inflammation. These reactions are typically characterized by redness, swelling, and induration at the site of antigen exposure.
Related Terms
- Hypersensitivity
- T cells
- Antigen
- Cytokines
- Macrophages
- Contact dermatitis
- Tuberculin skin test
- Granulomatous inflammation
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