Type IV hypersensitivity
Type IV Hypersensitivity
Type IV hypersensitivity (pronunciation: /taɪp fɔːr haɪ.pɚ.sɛn.sɪ.tɪ.vɪ.ti/), also known as delayed-type hypersensitivity (DTH), is a type of immune response that occurs due to the interaction of T cells and antigens. The etymology of the term comes from the Greek words "hyper" meaning over and "sensitivity".
Overview
Type IV hypersensitivity is the only type of hypersensitivity that is mediated by cellular immunity, rather than by antibodies. It is characterized by a delayed response, typically 48-72 hours after exposure to the antigen. This type of hypersensitivity is involved in many autoimmune and infectious diseases, as well as in the pathogenesis of contact dermatitis and transplant rejection.
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 macrophages cause tissue damage, leading to the characteristic symptoms of this type of hypersensitivity.
Clinical Manifestations
Clinical manifestations of Type IV hypersensitivity include contact dermatitis, tuberculosis, sarcoidosis, and graft-versus-host disease. These conditions are all characterized by tissue damage caused by an overactive immune response.
Diagnosis and Treatment
Diagnosis of Type IV hypersensitivity typically involves skin testing, where a small amount of the suspected antigen is applied to the skin. If a reaction occurs, this indicates a Type IV hypersensitivity to that antigen. Treatment typically involves avoiding the antigen and managing symptoms with anti-inflammatory medications.
See Also
External links
- Medical encyclopedia article on Type IV hypersensitivity
- Wikipedia's article - Type IV hypersensitivity
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