Delayed type hypersensitivity
| Type IV hypersensitivity | |
|---|---|
| Video explanation | |
| Classification and external resources | |
| MeSH | D006968 |
Type 4 hypersensitivity is often called delayed type hypersensitivity as the reaction takes two to three days to develop. Unlike the other types, it is not antibody mediated but rather is a type of cell-mediated response.
CD4+ helper T cells recognize antigen in a complex with MHC II on the surface of antigen-presenting cells. These can be macrophages that secrete IL-12, which stimulates the proliferation of further CD4+ Th1 cells. CD4+ T cells secrete IL-2 and interferon gamma, inducing the further release of other Th1 cytokines, thus mediating the immune response. Activated CD8+ T cells destroy target cells on contact, whereas activated macrophages produce hydrolytic enzymes and, on presentation with certain intracellular pathogens, transform into multinucleated giant cells.
epidermal necrosis, inflammation, skin rash and blisters
Insulitis, beta cell destruction
hypothyroidism, hard goiter, follicular thymitis
induration and erythema around injection site indicates previous exposure
...
Wikipedia