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Type I hypersensitivity (or immediate hypersensitivity), in the Gell and Coombs classification of allergic reactions, is an allergic reaction provoked by re-exposure to a specific type of antigen referred to as an allergen. [1] Type I is distinct from type II, type III and type IV hypersensitivities. The relevance of the Gell and Coombs ...
IgE may have evolved as a defense to protect against venoms. [6] [7] [8] IgE also has an essential role in type I hypersensitivity, [9] which manifests in various allergic diseases, such as allergic asthma, most types of sinusitis, allergic rhinitis, food allergies, and specific types of chronic urticaria and atopic dermatitis.
This type of reaction is also sometimes called immediate hypersensitivities, because the reaction happens super fast—on the order of minutes. So most allergic reactions are IgE-mediated, and therefore most allergies are type I hypersensitivity reactions.
According to this system, known as the Gell and Coombs classification [6] or Gell-Coombs's classification, [7] there are four types of hypersensitivity, namely: type I, which is an Immunoglobulin E (IgE) mediated immediate reaction; type II, an antibody-mediated reaction mainly involving IgG or IgM; type III, an immune complex-mediated reaction ...
However, upon re-exposure, the allergen binds to membrane-bound IgE which activates the mast cells, releasing a variety of mediators. [13] This type I hypersensitivity reaction is the basis of the symptoms of allergic reactions, which range from sneezing and rhinorrhoea to anaphylaxis. [13]
Type I hypersensitivity, or sometimes IgE-mediated hypersensitivity or immediate hypersensitivity, is a type of immune reaction in which tissue is damaged due to IgE antibody. Most allergies are caused by type I hypersensitivity reactions.
Bet v 1 is the main cause of type I allergies observed in early spring. Type I, or immunoglobulin E-mediated (IgE-mediated) allergies affect 1 in 5 people in Europe and North America. Commonly observed symptoms are hay fever, dermatitis, asthma and, in severe cases, anaphylactic shock.
Hypersensitivities are categorized according to the parts of the immune system that are attacked and the amount of time it takes for the response to occur. The four types of hypersensitivity reaction are: type 1, immediate IgE-mediated; type 2, cytotoxic; type 3, immune complex-mediated; and type 4, delayed cell-mediated. [58]