TYPE IV/DELAYED TYPE HYPERSENSITIVITY
Author: Sanketh DS, MDS
The immune system protects the human body against disease by dispatching a bunch of immune cells whenever the body encounters foreign material or antigens. These immune cells elicit an inflammatory response in order to remove or eliminate the foreign antigen without causing much damage to the host. However, under certain conditions, the host may elicit an exaggerated or an inappropriate immune response to a foreign antigen causing much damage to host tissues. This exaggerated or inappropriate immune response is termed hypersensitivity. There are four types of hypersensitivity reactions them being Type I, Type II, Type III and Type IV hypersensitivity.
Type IV hypersensitivity reaction is a T-cell mediated response primarily caused by CD4+ T cells, though these reactions can also be caused by CD 8+ T cells. Type IV hypersensitivity is also called delayed type hypersensitivity due to its delayed onset of reaction.
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