Type I hypersensitivity - wikipedia Type I hypersensitivity Type I hypersensitivity SEM of miscellaneous plant pollens : Pollens are very common allergens. Classification and external resources MeSH D006969 ( edit on Wikidata ) Type I hypersensitivity ( or immediate hypersensitivity ) is an allergic reaction provoked by reexposure to a specific type of antigen referred to as an allergen. Type I is not to be confused with type II, type III, or type IV hypersensitivities, nor is it to be confused with Type I Diabetes or Type I of any other disease or reaction. Exposure may be by ingestion, inhalation, injection, or direct contact. Play media Video explanation Contents 1 Pathophysiology 2 Treatment and prognosis 3 Examples 4 See also 5 References Pathophysiology In type 1 hypersensitivity, B - cells are stimulated ( by CD4 + TH2 cells ) to produce IgE antibodies specific to an antigen. The difference between a normal infectious immune response and a type 1 hypersensitivity response is that in type 1 hypersensitivity, the antibody is IgE instead of IgA, IgG, or IgM. During sensitisation, the IgE antibodies bind to FcεRI receptors on the surface of tissue mast cells and blood basophils. Mast cells and basophils coated by IgE antibodies are `` sensitized ''. Later exposure to the same allergen cross-links the bound IgE on sensitized cells, resulting in anaphylactic degranulation, which is the immediate and explosive release of pharmacologically active pre-formed mediators from storage granules and concurrent synthesis of inflammatory lipid mediators from arachidonic acid ; some of these mediators include histamine, leukotriene ( LTC4 and LTD4 ), and prostaglandin, which act on proteins ( e.g., G - protein coupled receptors ) located on surrounding tissues. The principal effects of these products are vasodilation and smooth - muscle contraction. Type 1 hypersensitivity can be further classified into immediate and late - phase reactions. The immediate hypersensitivity reaction occurs minutes after exposure and includes release of vasoactive amines and lipid mediators, whereas the late - phase reaction occurs 2 -- 4 hours after exposure and includes the release of cytokines. List of a few mediators released by mast cells in type 1 hypersensitivity and their actions Vasodilation and increased permeability Histamine PAF Leukotriene C4, D4, and E4 Prostaglandin D2 Neutral proteases Smooth muscle spasm Histamine PAF Leukotriene C4, D4, and E4 Prostaglandin Leukocyte extravasation Cytokines ( e.g. chemokines and TNF ) Leukotriene B4 Chemotactic factors for neutrophils and eosinophils Unless otherwise specified, the reference for this table is : 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 adrenaline ( epinephrine ), antihistamines, and corticosteroids. If the entire body is involved, then anaphylaxis can take place, which is an acute, systemic reaction that can prove fatal. Examples Some examples : Allergic asthma Allergic conjunctivitis Allergic rhinitis ( `` hay fever '' ) Anaphylaxis Angioedema Urticaria ( hives ) Eosinophilia Penicillin allergy Cephalosporin allergy Food allergy Sweet itch See also Type V hypersensitivity References Jump up ^ med / 1101 at eMedicine Jump up ^ `` The Adaptive Immune System : Type I Immediate Hypersensitivity ''. Retrieved 2008 - 09 - 22. ^ Jump up to : Moon TC, Befus AD, Kulka M ( 2014 ). `` Mast cell mediators : their differential release and the secretory pathways involved ''. Front Immunol. 5 : 569. doi : 10.3389 / fimmu. 2014.00569. PMC 4231949. PMID 25452755. This release of pre-formed mediators enables not only rapid anaphylactic reactions and allergic responses but also initiates recruitment of leukocytes to sites of pathogen invasion, activation of innate immune processes, and inflammatory responses ( 1 )... Two types of degranulation have been described for MC : piecemeal degranulation ( PMD ) and anaphylactic degranulation ( AND ) ( Figures 1 and 2 ). Both PMD and AND occur in vivo, ex vivo, and in vitro in MC in human ( 78 -- 82 ), mouse ( 83 ), and rat ( 84 ). PMD is selective release of portions of the granule contents, without granule - to - granule and / or granule - to - plasma membrane fusions... In contrast to PMD, AND is the explosive release of granule contents or entire granules to the outside of cells after granule - to - granule and / or granule - to - plasma membrane fusions ( Figures 1 and 2 ). Ultrastructural studies show that AND starts with granule swelling and matrix alteration after appropriate stimulation ( e.g., FcεRI - crosslinking ). Figure 1 : Mediator release from mast cells Figure 2 : Model of genesis of mast cell secretory granules Figure 3 : Lipid body biogenesis Table 2 : Stimuli - selective mediator release from mast cells Jump up ^ Shiv Pillai MD ; Abul K. Abbas MBBS ; Andrew Wilson ( 2011 ). Cellular and Molecular Immunology : with STUDENT CONSULT Online Access. Philadelphia : Saunders. ISBN 1 - 4377 - 1528 - 1. Jump up ^ Table 5 - 2 in : Mitchell, Richard Sheppard ; Kumar, Vinay ; Abbas, Abul K. ; Fausto, Nelson. Robbins Basic Pathology. Philadelphia : Saunders. ISBN 1 - 4160 - 2973 - 7. 8th edition. Hypersensitivity and autoimmune diseases ( 279.5 -- 6 ) Type I / allergy / atopy ( IgE ) Foreign Atopic eczema Allergic urticaria Allergic rhinitis ( Hay fever ) Allergic asthma Anaphylaxis Food allergy common allergies include : Milk Egg Peanut Tree nut Seafood Soy Wheat Penicillin allergy Autoimmune Eosinophilic esophagitis Type II / ADCC IgM IgG Foreign Hemolytic disease of the newborn Autoimmune Cytotoxic Autoimmune hemolytic anemia Immune thrombocytopenic purpura Bullous pemphigoid Pemphigus vulgaris Rheumatic fever Goodpasture 's syndrome Guillain -- Barré syndrome `` Type V '' / receptor Graves ' disease Myasthenia gravis Pernicious anemia Type III ( Immune complex ) Foreign Henoch -- Schönlein purpura Hypersensitivity vasculitis Reactive arthritis Farmer 's lung Post-streptococcal glomerulonephritis Serum sickness Arthus reaction Autoimmune Systemic lupus erythematosus Subacute bacterial endocarditis Rheumatoid arthritis Type IV / cell - mediated ( T cells ) Foreign Allergic contact dermatitis Mantoux test Autoimmune Diabetes mellitus type 1 Hashimoto 's thyroiditis Multiple sclerosis Coeliac disease Giant - cell arteritis Postorgasmic illness syndrome Reactive arthritis GVHD Transfusion - associated graft versus host disease Unknown / multiple Foreign Hypersensitivity pneumonitis Allergic bronchopulmonary aspergillosis Transplant rejection Latex allergy ( I + IV ) Autoimmune Sjögren 's syndrome Autoimmune hepatitis Autoimmune polyendocrine syndrome APS1 APS2 Autoimmune adrenalitis Systemic autoimmune disease Retrieved from `` https://en.wikipedia.org/w/index.php?title=Type_I_hypersensitivity&oldid=810894641 '' Categories : Type I hypersensitivity Hidden categories : Infobox medical condition Talk Contents About Wikipedia Español Norsk nynorsk Українська 中文 Edit links This page was last edited on 18 November 2017, at 04 : 03. 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Question: type of antigen that triggers an allergic reaction
Answer: allergen