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Module 5: Allergenicity

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IgE-Mediated Food Allergies

Mechanism

An allergic reaction involves the overactivity of several components of the body’s immune system, as a result from exposure to an allergen. Several types of cells are involved in the stimulation of the allergic response. Lymphocytes are a prime component of the immune system. Specifically B-lymphocytes, which are located in the thymus, lymph nodes, blood, and spleen, are responsible for the production and secretion of immunoglobulin (Ig) antibodies. There are five classes of Ig antibodies, namely IgA, IgD, IgG, IgE, and IgM (4). The IgE antibody is responsible for mediating the allergic response, through its binding to receptors on mast cells and basophils (2).

Mast cells are usually found in connective tissues, particularly around lymph nodes, nerves, and blood vessels (2). Basophils circulate in the bloodstream. Both of these cells contain granules, which contain powerful chemicals, such as histamine. When a person is exposed to a particular allergen, the B-lymphocytes produce IgE antibodies in response to the antigen. The millions of IgE antibodies then bind to receptors of the surface of mast cells and basophils (4).

When a person is re-exposed to the particular allergen or antigen, the sensitized mast cells and basophils react by releasing the powerful chemicals and histamine from the granules, which produce the allergic reaction (2, 4).

The animation below will help you get a visual picture and a better understanding of the sequence of events that take place during an IgE-mediated allergic reaction.




Allergenic Response Animation

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