Category: Food Allergies
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Allergies are abnormal immune responses to allergens like pollen grains, dust, moulds and foodstuffs. The allergens can enter the body through inhalation, ingestion, injection, or external skin contact. Allergens cause abnormal production of immunoglobulin E (IgE), an antibody already present in the body in small amounts. When the antigen makes contact with some part of the body, it is taken up, processed by Antigen Presenting Cell (APC) and presented on a Class II MHC to Helper cells. In the early stages of allergy, a type I hypersensitivity reaction against an allergen, encountered for the first time, causes a response in the T helper cells. These T helper cells produce cytokines which stimulate B-cells to produce large amount of IgE by proliferating IgE producing plasma cells. Secreted IgE circulates in the blood and binds to an IgE-specific receptor on the surface of mast cells and basophils, which are both involved in the acute inflammatory response.
The IgE-coated cells, at this stage are sensitized to the allergen. During second exposure, antigen binds to the IgE antibodies on the mast cells. Activated mast cells and basophils undergo degranulation to release histamine and other inflammatory chemical mediators (cytokines, interleukins, leukotrienes, and prostaglandins) from their granules into the surrounding tissue causing several systemic effects, such as Nasal Stuffyness, Sneezing, Runny nose, Watery eyes and mucous discharge. This animation delineates the process of immune response on encounter with an allergen.