type IV hypersensitivity reaction
This type of hypersensitivity reaction is mediated by the action of lymphocytes rather than by antibody.
The process develops over more than 12 hours and may take 2-3 days to evolve.
The reaction involves sensitised T cells, which in response to antigen release lymphokines and interleukins and may also directly kill target cells. There is a mononuclear cell infiltration into the site of antigen deposition.
An example of a type IV hypersensitivity reaction is the response to tuberculin.
Last reviewed 06/2021