The primary function of IgE (Immunoglobulin E) is to mediate allergic reactions and to provide immunity against parasitic worms (helminths).
Detailed Explanation of IgE Function
IgE plays two key roles in the immune system:
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Allergic Reactions (Type I Hypersensitivity):
- IgE is central to the development of allergies and atopic disorders such as allergic rhinitis (hay fever), asthma, and atopic dermatitis (eczema).
- Sensitization Phase: During the initial exposure to an allergen (e.g., pollen, dust mites), IgE antibodies are produced by plasma cells. These IgE antibodies then bind to high-affinity receptors (FcεRI) on the surface of mast cells and basophils. This process is called sensitization.
- Activation Phase: Subsequent exposure to the same allergen triggers the cross-linking of IgE antibodies bound to FcεRI on mast cells and basophils.
- Effector Phase: This cross-linking triggers the release of inflammatory mediators such as histamine, leukotrienes, and prostaglandins from mast cells and basophils. These mediators cause the characteristic symptoms of allergic reactions, including vasodilation, increased vascular permeability, bronchoconstriction, and mucus production.
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Anti-Parasitic Immunity:
- IgE also plays a role in the immune response against parasitic worms (helminths).
- IgE antibodies bind to the surface of parasites.
- Eosinophils, another type of immune cell, possess FcεRI receptors. IgE binding to the parasite recruits eosinophils, which then release cytotoxic substances that kill the parasite.
- IgE also activates mast cells, contributing to inflammation that helps expel the parasite.
Summary
In summary, IgE's functions include mediating allergic responses through mast cell and basophil activation and providing immunity against parasitic worm infections by activating eosinophils and mast cells. Its role in allergic reactions makes it a key target for therapies aimed at managing allergic diseases.
