Authors:
Thomas WR, Cunningham PT.
Authors notes:
eLS: John Wiley & Sons, Ltd; 2015.
Keywords:
hypersensitivity, allergy, Gell and Coombs, immediate hypersensitivity, delayed hypersensitivity, type I hypersensitivity, type II hypersensitivity
Abstract:
Immunological hypersensitivities are immunological states where the immune system produces harmful responses upon re-exposure to sensitising antigens.
There is a sensitisation phase where the memory T and B cells develop and an effector phase where they elicit inflammatory responses.
In 1963, Gell and Coombs classified hypersensitivity into four types by their different effector mechanisms.
Type 1 encompassed the IgE-mediated hypersensitivities, type II the action of antibodies on cells, type III the action of antigen-antibody complexes and type IV the direct action of lymphocytes exemplified by delayed hypersensitivity.
A category of type V, introduced by others, is sometimes used to describe noncytotoxic responses mediated by antibodies to affect cell function, especially applied to the endocrine system.
Subcategories of type IV were introduced to categorise the clinically distinct hypersensitivities induced by different types of T-cell response and are elaborated here in terms of Th1, Th2 and Th17 differentiation lineages.