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IgE
IgE Full Name
immunoglobulin heavy chain (epsilon polypeptide)
IgE Introduction
Immunoglobulin E (IgE) is a unique antibody that plays various physiological roles, including Type I hypersensitivity reactions, defense against parasites, autoimmune processes, and venom protection. Immunoglobulin molecules, including IgE, have a common structure consisting of two small polypeptide chains (light chains) and two large polypeptide chains (heavy chains). The heavy chains make up the Fc region responsible for binding to cellular receptors, while the Fab region, made up of both heavy and light chains, is where antigen recognition and binding occur. The variable regions in the antigen binding sites can be altered to improve affinity for specific antigens. The chains are organized into layers of B-pleated sheets, creating a three-dimensional structure for antigen binding. The rest of the chains are constant regions held together by strong dipeptide bonds.
Figure 1. Structure of IgE.
(Source: Novosad, J. et al., 2020)
Unlike some antibodies, such as IgM, which can form pentamers capable of binding multiple antigens, IgE is a monomer composed of two epsilon-heavy chains and two light chains, allowing it to bind two antigens. The C-terminal regions of the heavy chains form four C-epsilon dimers, which are crucial for binding specific cellular receptors. IgE lacks a hinge region found in other immunoglobulins, enhancing its flexibility during receptor interactions. It is heavily glycosylated, with seven glycosylation sites on each heavy chain, enabling binding to the high-affinity receptor Fc-epsilon-R1.
IgE antibodies play a crucial role in the development of human allergic diseases. They are primarily produced by plasma cells located in the lymphoid tissue associated with the gastrointestinal and respiratory tracts. IgE can be found in various forms: free in mucosal secretions, bound to mast cells in local tissues, or distributed throughout the body via the systemic circulation, binding to mast cells and basophils. Total serum IgE concentrations tend to be higher in allergic individuals compared to non-allergic individuals. However, the value of total serum IgE as a screening test for allergic disease is limited. The measurement of allergen-specific IgE levels has greater clinical significance. Allergen-specific IgE concentrations vary based on factors such as age, recent allergen exposure, and cross-reactivity. Quantitative assays for allergen-specific IgE have been suggested as valuable tools in recent studies. It's worth noting that increased serum IgE levels can also be observed in certain non-allergic conditions, including infectious and parasitic diseases. However, in these cases, the IgE changes are typically specific to the particular infectious agent, whereas they are non-specific in other diseases. Therefore, analyzing total and allergen-specific IgE levels can provide valuable clinical information in the diagnosis and management of allergic diseases.
Alternate Names for IgE
Immunoglobulin E;IGHE;Immunoglobulin heavy chain (epsilon polypeptide);IGH2;IGHEP1
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