Table 1. Clinical patterns of acute drug hypersensitivity reactions [7,8] In most cases the diagnosis of immediate-type hypersensitivity can be. IgE mediates type 1 hypersensitivity allergic reactions. Plasma levels of IgE are normally very low (,fold lower than for IgG), but can be markedly increased in certain allergic conditions, such as bronchopulmonary aspergillosis, or with parasitic diseases, such as schistosomiasis. Hypersensitivity Reactions. (Types I, II, III, IV) Type I. Produce effector molecules. Capable of ingesting foreign. Particles Pillai, Table


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The IgE becomes bound to mast cells in places such as respiratory tract mucosa. Encountering the allergen again leads to mast cell degranulation with release of primary mediators such as histamine, serotonin which type 1 hypersensitivity reaction vasodilation, bronchoconstriction, etc.

The process of mast cell degranulation is diagrammed below: There are two forms of anaphylaxis: Most clinically relevant immune-mediated immediate-type reactions to drugs are thought to be either IgE-mediated or T-cell mediated [ 2425 ].

Type I hypersensitivity reaction: mechanism and clinical manifestation -

Generally, the more delayed the reaction is, the more likely type 1 hypersensitivity reaction is to be T-cell mediated [ 26 ], with some notable exceptions being abacavir hypersensitivity in human immunodeficiency virus HIV patients and piperacillin reactions in cystic fibrosis patients.

IgE-mediated adverse drug reactions Upon first exposure, free or conjugated drug is taken up by dendritic cells, processed and presented to T and B-cells within the context of a Th2 response, resulting in production of allergen-specific IgE antibodies to the drug or a drug-protein complex.

On subsequent exposure, the drug or drug—protein complex is recognized by IgE antibodies bound to their high affinity receptor on the surface of mast cells and basophils. Cross-linking of IgE leads to activation of a calcium-dependent protein kinase cascade and the type 1 hypersensitivity reaction release of inflammatory mediators such as histamine, prostaglandin D2, sulfidoleukotrines, MCT and various cytokines [ 828 ].

It is noteworthy that for a number of presumed immediate hypersensitivity reactions, drug-specific IgE is not detected. The debate type 1 hypersensitivity reaction whether IgE has a significant role in radiocontrast reactions continues, with an emerging recognition that many radiocontrast media reactions may in fact be IgE mediated [ 31 ].

Direct cross-linking, haptenation and pro-haptens A few drugs with large molecular weights have multiple recurrences of a single epitope and thus are able to cross-link IgE molecules directly [ 32 — 34 ].

The best studied example of this is quaternary ammonium epitopes, which render some NMBDs multivalent.

Type I hypersensitivity - Wikipedia

Smaller molecular weight drugs i. The hapten hypothesis is that chemically reactive small molecules called haptens are able to undergo a stable covalent binding to larger proteins. Haptenation thus results in an alteration of autologous proteins by drug epitopes type 1 hypersensitivity reaction a drug-specific immune response can ensue.

Sensitized type 1 hypersensitivity reaction can produce cytokines, which are biologically active substances that affect the functions of other cells. This type of reaction takes hours, or longer, after contact with the antigen to fully develop.

Many chronic infectious diseases, including tuberculosis and fungal infections, exhibit delayed hypersensitivity. This IgE class of antibodies have high binding affinity to Fc receptor on the surface of tissue mast cells and blood basophils.

Immediate-type hypersensitivity drug reactions

Mast cells and basophils bound by IgE are said to be sensitized. A latter exposure to the same allergens cross links the membrane bound IgE on sensitized mast cell and basophils causing degranulation of these cells. Degranulation causes release of pharmacological active mediators type 1 hypersensitivity reaction act on surrounding tissue causing vasodilation and smooth muscle contraction which may be either systemic or localized.


This effect is also termed as Allergy.