Immunology 1 hypersensitivity and allergy notes 10th february 2011 learning objectives. Understanding of the mechanisms underlying allergies type i hypersensitivity or immediate reactions will enable us to improve our treatment with allergic diseases. Typei hypersensitivity reaction is an immediate type of reaction mediated by ige. Hypersensitivity refers to undesirable reactions produced by the normal immune system vahid naseri supervised. Suspected type iv reaction, mechanism not fully elucidated. Antibiotic hypersensitivity reactions and approaches to desensitization davey p. Type ii reactions that are antibodymediated and may result in thrombocytopenia, neutropenia, or hemolytic anemia. Opsonization and complement and fc receptormediated phagocytosis complement and fc receptormediated inflammation. Type ii hypersensitivity is an antibodydependent process in which specific antibodies bind to antigens, resulting in tissue damage or destruction see fig. Type iii immune complex hypersensitivity mechanism and. Reviews hypersensitivity reactions to biological drugs. Clinical symptoms vary widely, from skin reactions to anaphylaxis. Complexes of antigen and antibody form in the circulation and are then deposited in susceptible tissues.
Type i reactions, which are ige mediated and may lead to anaphylaxis. Type i hypersensitivity or immediate hypersensitivity is an allergic reaction provoked by reexposure to a specific type of antigen referred to as an allergen. Start studying classification and mechanisms of hypersensitivity reactions. Chapter 109 allergy, hypersensitivity, angioedema, and anaphylaxis episode overview key points.
Multiple choice questions on hypersensitivity reactions 1. Hypersensitivity introduction, causes, mechanism and types. Type i immediate type ige monomers anaphylaxis type ii cytotoxic type iggigm monomers druginduced hemolysis type iii immune complex type iggigm multimers serum sickness type iv delayed type t cells ppd rxn contact dermatitis. Mechanisms in the effector phase and anaphylaxis eva untersmayrelsenhuber department of pathophysiologyand allergy research topics of lecture clincal presentation of allergic reactions key players in allergic inflammation mechanisms of anaphylactic reactions ige allergen mast cells. Shows nice animations and descriptions for the mechanism of a type iii hypersensitivty reaction.
Various autoimmune disorders as well as allergies fall under the umbrella of hypersensitivity reactions, the difference being that allergies are immune reactions to exogenous substances antigens or allergens, whereas autoimmune diseases arise from an abnormal immune response to endogenous substances autoantigens. Allergy to penicillin is an example of a type i hypersensitivity. Type iv hypersensitivity is a cellmediated immune reaction. Active defence of plants hypersensitive resistance is induced by the pathogen itself. Type iii hypersensitivity reactions are also termed immune complex reactions. Hypersensitity, and types of hypersensitivity i, ii, iii, iv. Data on prevalence and incidence of drug hypersensitivity reactions dhrs are limited, especially in pediatric age and varies around the world. Tuberculin reactions, chronic asthma, and contact dermatitis are examples of type iv reactions. As its mechanisms do not destroy target cells, they are responsible for induction of organtissue dysfunctions only most of authors prefer it to be and independent, the 5th type of hypersensitivity reactions.
This is illustrated using the example of two almost isogenic lines of nicotiana tabacum microinoculated with the u1 strain of tobacco mosaic virus. Type iv hypersensitivities are regulated by t cells and are delayed reactions to antigens associated with cells. Types i, ii, and iii reactions are antibody dependent and type iv is cell mediated. Type ii hypersensitivity an overview sciencedirect topics.
Immediate hypersensitivity reactions are a conse quence of antigen exposure resulting in reaginic an tibody usually ige but also igg, in humans4 produc. In some cases, an immune mechanism mediated by ige, igg, or t cells is involved. Mechanisms in cutaneous drug hypersensitivity reactions. Use of some antiretroviral arv drugs may cause a hypersensitivity reaction. View enhanced pdf access article on wiley online library html view download pdf for offline viewing. This video includes a beautiful animation that shows clearly all of the steps involved in the early primary and late secondary responses from a type i hypersensitivity reaction. It is induced by certain types of antigen called allergens such as pollengrains, dandruff, dusts, food components etc. Most allergy is igemediated and it is now widely accepted that the use of the term allergy is restricted to those reactions and diseases where this mechanism underlies the pathologic process. Type i immediate type ige monomers anaphylaxis type ii cytotoxic type iggigm monomers druginduced hemolysis type iii immune complex type iggigm multimers serum sickness type. Hypersensitivity reactions are categorized into four major types.
Type i hypersensitivity is the most common type of hypersensitivity reaction. Type i hypersensitivity mechanism described concisely. True penicillin allergy is rare with the estimated frequency of anaphylaxis at 15 per 10 000 cases of penicillin therapy. Reactions of this kind depend on the presence in the circulation of a sufficient number of t. Hypersensitivity is however, its most important adverse reaction resulting in nausea, vomiting, pruritus, urticaria, wheezing, laryngeal oedema and. When an immune response result in exaggerated or in appropriate reactions harmful to the host the term hypersensitivity or allergy used. Unlike the normal immune response, the type i hypersensitivity response is. Mechanisms of hypersensitivity reactions induced by drugs ncbi. If the antigen is present on cell surfaces, antibody binding can result in cell lysis through the in. In these disorders, tissue injury may be due to t lymphocytes that induce inflammation or directly kill target cells. Type iv hypersensitivity reactions or cellmediated reactions gell and coombs conceived several organspeci. Classification and mechanisms of hypersensitivity reactions.
A history of sudden urticarial rash accompanied by respiratory difficulty, abdominal pain, or hypotension, strongly favors the diagnosis of anaphylaxis. Type i is distinct from type ii, type iii and type iv hypersensitivities. In this chapter, the features of type i hypersensitivity reactions and the major components involved as well as their potential roles in the induction and regulation of allergic. The gellcoombs classification of hypersensitivity reactions.
This chapter considers type i and iv hypersensitivity. Exposure may be by ingestion, inhalation, injection, or direct contact. Penicillin allergy and desensitization in serious infections during pregnancy. Allergic reactions occur to normally harmless environmental substances known as allergens reactions are acquired, predictable, and rapid include eczema, hives, hay fever, asthma attacks, food allergy, and reactions to. Allergic rhinitis hay fever reactions to plant pollen or house dust. Mechanism of the hypersensitivity reaction of plants.
Figure 1 induction and effector mechanisms in type 1 hypersensitivity. Epinephrine is the firstline treatment in patients with anaphylaxis. Patients need to be closely observed for any allergic reactions during and for at least 30min after iviron injection. Hypersensitivity also called hypersensitivity reaction or intolerance refers to undesirable reactions produced by the normal immune system, including allergies and autoimmunity. The type v reactions are sometimes considered as a subtype of the type ii hypersensitivity. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Type iii reaction that involves an immune complex formation such as vasculitis. In this hypersensitivity reaction, specific antibody igg or igm bound to cell surface antigen and destroy the cell. It is an allergic reaction provoked by reexposure to a specific type of antigen, referred to as an allergen. Chapter 109 allergy, hypersensitivity, angioedema, and. Hypersensitivity reactions, including allergic reactions, can be lifethreatening. Type iii hypersensitivity as in other cases of hypersensitivity occur when the mechanism of self tolerance is breached and some self reactive immune cells are activated to mount reactions against auto antigens such as the dna from an auto cell. An exaggerated immune response to a specific antigen or drug. Hypersensitivity reactions are betatype reactions and include infusion reactions and injection site reactions.
Pdf hypersensitivity responses are a group of reactions in which the immune. They are usually referred to as an over reaction of the immune system and these reactions may be damaging, uncomfortable, or occasionally fatal. Outline the mechanisms by which ige, antibodies, immune complexes and t cells can cause tissue damage and inflammation the four types of hypersensitivity, giving examples of the. Hypersensitivity type i hypersensitivity classic allergy allergens. Type ii hypersensitivity reaction involves antibody mediated destruction of cells. The nsaidsinduced hypersensitivity reactions involve different mechanisms and pres. Hypersensitivity refers to excessive, undesirable damaging, discomfortproducing and sometimes fatal reactions produced by the normal immune system.
Antibiotic related hypersensitivity reactions may be. During the last decade, the development of rapid drug desensitization has been key to allow patients with hsrs to taxanes to be safely retreated although the mechanisms of these hsrs are not fully understood. Gell and coombs classified hypersensitivity reactions into four types. Multiple choice questions on hypersensitivity reactions. Hypersensitivity reactions are the major problem in the use of penicillins. The four types of hypersensitivity reaction i to iv are defined by the principal mechanism responsible for a specific cell or tissue injury that occurs during an immune response. Allergy and hypersensitivity iowa state university. In other words, it does not involve the participation of antibodies but is due primarily to the interaction of t cells with antigens. Type iv hypersensitivity is also called as a immediate hypersensitivity b delayed hypersensitivity c cytotoxic hypersensitivity d immune complex hypersensitivity 3.
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