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This response involves the interaction of T cells, monocytes, and macrophages. This reaction is caused when CD4 + T h 1 cells recognize foreign antigen in a complex with the MHC class II on the surface of antigen-presenting cells. These can be macrophages that secrete IL-12, which stimulates the proliferation of further CD4 + T h 1 cells.
T cells are called T cells because they mature in the thymus. The two types of T cells that cause damage to tissues in type IV hypersensitivity are CD8+ T cells also known as killer T cells or cytotoxic T cells, as well as CD4+ T cells also known as helper T cells. CD8+ killer T cells do exactly what their name implies - they kill things.
The T helper cells (T h cells), also known as CD4 + cells or CD4-positive cells, are a type of T cell that play an important role in the adaptive immune system. They aid the activity of other immune cells by releasing cytokines .
In molecular biology, CD4 (cluster of differentiation 4) is a glycoprotein that serves as a co-receptor for the T-cell receptor (TCR). CD4 is found on the surface of immune cells such as helper T cells , monocytes , macrophages , and dendritic cells .
A third category called T helper 17 cells (T H 17) were also discovered which are named after their secretion of Interleukin 17. CD8 + cytotoxic T-cells may also be categorized as: [5] T c 1 cells, T c 2 cells. Similarly to CD4 + T H cells, a third category called T C 17 were discovered that also secrete IL-17.
Hypersensitivity (also called hypersensitivity reaction or intolerance) is an abnormal physiological condition in which there is an undesirable and adverse immune response to an antigen. [ 1 ] [ 2 ] It is an abnormality in the immune system that causes immune diseases including allergies and autoimmunity .
This discovery furthered the development of a previously hypothesized theory, the immunosurveillance theory. The immunosurveillance theory suggests that the immune system routinely patrols the cells of the body, and, upon recognition of a cell, or group of cells, that has become cancerous, it will attempt to destroy them, thus preventing the growth of some tumors.
The p-i concept refers to the pharmacological interaction of drugs with immune receptors. It explains a form of drug hypersensitivity, namely T cell stimulation, which can lead to various acute inflammatory manifestations such as exanthems, eosinophilia and systemic symptoms, Stevens–Johnson syndrome, toxic epidermal nercrolysis, and complications upon withdrawing the drug.