- Type I hypersensitivity
Infobox_Disease
Name = Type I hypersensitivity
Caption = SEM of miscellaneous plant pollens. Pollens are very common allergens.
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MeshID = D006969Type I hypersensitivity (or immediate hypersensitivity) is an allergic reaction provoked by reexposure to a specific type of
antigen referred to as anallergen . [eMedicine|med|1101]Exposure may be by
ingestion ,inhalation , injection, or direct contact.Pathophysiology
The difference between a normal immune response and a type I hypersensitive response is that plasma cells secrete
IgE . This class of antibodies binds to Fc receptors on the surface of tissue mast cells and blood basophils.cite web |url=http://student.ccbcmd.edu/courses/bio141/lecguide/unit5/hypersensitivity/type1/type1.html |title=The Adaptive Immune System: Type I Immediate Hypersensitivity |format= |work= |accessdate=2008-09-22] Mast cells and basophils coated by IgE are "sensitized." Later exposure to the same allergen, cross-links the bound IgE on sensitized cells resulting indegranulation and the secretion of pharmacologically active mediators such as histamine,leukotriene , andprostaglandin that act on the surrounding tissues. The principal effects of these products arevasodilation and smooth-muscle contraction.The reaction may be either local or systemic. Symptoms vary from mild irritation to sudden death from anaphylactic shock.
Treatment and prognosis
Treatment usually involves
epinephrine ,antihistamines , andcorticosteroid s. If the entire body gets involved, then anaphylaxis can take place; an acute, systemic reaction that can prove fatal.Examples
Some examples:
*Allergicasthma
*Allergicconjunctivitis
*Allergic rhinitis ("hay fever")
*Anaphylaxis
*Angioedema
*Urticaria (hives)
*Eosinophilia
*Penicillin
*Cephalosporin References
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type IV hypersensitivity — hypersensitivity initiated by antigen specific T lymphocytes; unlike forms mediated by antibodies, it takes one or more days to develop and can be transferred by lymphocytes but not by serum. The term is often equated with delayed… … Medical dictionary
type I hypersensitivity — hypersensitivity that occurs rapidly (within several minutes) upon reexposure to an antigen, due to interaction of IgE and the antigen; see type I hypersensitivity reaction, under hypersensitivity reaction, at reaction … Medical dictionary
type II hypersensitivity — hypersensitivity resulting from antibody antigen interactions on cell surfaces; see type II hypersensitivity reaction, under hypersensitivity reaction, at reaction. Called also antibody mediated h … Medical dictionary
type III hypersensitivity — hypersensitivity due to formation of circulating antigen antibody complexes and their deposition in tissues; see type III hypersensitivity reaction, under hypersensitivity reaction, at reaction. Called also immune complex–mediated h … Medical dictionary
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Type II hypersensitivity — In type II hypersensitivity (or cytotoxic hypersensitivity)cite web |url=http://pathmicro.med.sc.edu/ghaffar/hyper00.htm |title=Hypersensitivity reactions |format= |work= |accessdate=] the antibodies produced by the immune response bind to… … Wikipedia
type IV hypersensitivity — A delayed hypersensitivity response (it appears 24 to 48 hours after antigen exposure). It results from the binding of antigen to activated T lymphocytes, which then release cytokines and trigger inflammation and macrophage attacks that damage… … Dictionary of microbiology
type I hypersensitivity — A form of immediate hypersensitivity arising from the binding of antigen to IgE attached to mast cells, which then release anaphylaxis mediators such as histamine. Examples: hay fever, asthma, and food allergies … Dictionary of microbiology
type II hypersensitivity — A form of immediate hypersensitivity involving the binding of antibodies to antigens on cell surfaces followed by destruction of the target cells (e.g., through complement attack, phagocytosis, or agglutination) … Dictionary of microbiology