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How does IgE contribute to allergic reactions?
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antibody
The four-chain structure of an antibody, or immunoglobulin, molecule. The basic unit is composed of two identical light (L) chains and two identical heavy (H) chains, which are held together by disulfide bonds to form a flexible Y shape. Each chain is composed of a variable (V) region and a constant (C) region.
Immunoglobulin E (IgE) plays a central role in Type I hypersensitivity reactions, which include common allergies and the severe systemic reaction known as anaphylaxis.123
The process occurs through the following mechanism:
- Sensitization: Upon initial exposure to an allergen, the immune system produces specific IgE antibodies. These antibodies possess a unique structural property—an extra constant domain—that allows them to bind firmly to the surface of mast cells and basophils.42
- Activation: When an individual is subsequently exposed to the same allergen, the antigen binds to the IgE molecules already attached to these cells.42
- Chemical Release: This binding stimulates the mast cells and basophils to degranulate, releasing potent inflammatory chemicals such as histamine, serotonin, and leukotrienes.23
- Symptoms: These chemicals cause the characteristic symptoms of an allergic reaction, including the dilation of blood vessels (leading to hives or swelling), constriction of bronchial smooth muscles (causing breathing difficulties), and increased vascular permeability.23