Hypersensitivity Flashcards
defense mechanism by which the body rids itself of potentially harmful antigens. However, in some cases, the antigen can persist, and the immune response can cause damage to the host
immune response
exaggerated response to a typically harmless antigen that results in injury to the tissue, disease, or even death.
hypersensitivity
British immunologists who devised a classification system for these reactions based on four different categories
P. G. H. Gell and R. R. A. Coombs
anaphylactic hypersensitivity
Type I hypersensitivity
exposure to an antigen induces production of specific immunoglobulin E (IgE) antibody, which binds to receptors on mast cells and basophils. Subsequent attachment of the antigen to adjacent cell-bound IgE results in degranulation with release of chemical mediators that produce characteristic allergy symptoms
Type I hypersensitivity
antibody-mediated cytotoxic hypersensitivity
type II hypersensitivity
Immunoglobulin G (IgG) or immunoglobulin M (IgM) antibodies react with antigens on the surface of host cells. This can lead to cell damage by complement-mediated lysis or other mechanisms, dysfunction of the cell by blocking the binding of a ligand to a surface receptor, or overstimulation of a cell’s function
type II hypersensitivity
complex-mediated hypersensitivity
Type III hypersensitivity
IgG or IgM antibodies react with soluble antigens to form small complexes that precipitate in the tissues and activate complement. Recruitment of neutrophils to the site results in an inflammatory response that causes injury to the tissues
Type III hypersensitivity
cell-mediated hypersensitivity
Type IV hypersensitivity
*differs from the other three types because sensitized T cells, rather than antibody, are responsible for the symptoms that develop.
*involves the release of cytokines that induce
inflammation and tissue damage.
Type IV hypersensitivity
symptoms develop within a few minutes to a few hours after exposure to the antigen
immediate hypersensitivity
Examples of immediate hypersensitivity
Types I through III
manifestations are not seen until 24 to 48 hours after contact with the antigen
delayed hypersensitivity
Example of delayed hypersensitivity
Type IV hypersensitivity