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Lecture 35.docx

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York University
Natural Science
NATS 1670
Motti Anafi

Allergy Allergic reactions are the evil part of the immune system. Your immune system is usually working well if it is in some sort of balance between infection and immunity. If infection is working stronger than immunity, this can result in an allergic reaction. • Allergies are abnormal sensitivities to antigens in the environment • Allergens are antigens that cause allergies Dust mites Dust mites can be found everywhere. They can cause allergic reactions in some people. Pollens The allergic reaction of these takes place in a very unique time of the year. It is seasonal. Development of Allergic Reaction Typical allergic reaction First Type Tissue contact with allergen (antigen)  B cells produce IgE against allergen  IgE attaches to mast cells Sensitization: First exposure to allergen Second Type Allergens complex with IgE on mast cells  Mast cells release histamine and other chemical  Blood Vessels dialate and release plasma Reaction: Second exposure to allergen Mast Cells Resting Mast Cell Activated Mast Cell Mast cells and Basophils • Mast cells and basophils contain granules filled with inflammatory chemicals such as histamine • Sensitized cells bind IgE • They are able to release the potent inflammatory mediators o Degranulation • May be induced by aggregation of IgE bound to high-afinity receptors (Fc receptors) on the surface of these cells • Specific antigen (allergen) is responsible for the IgE aggregation. Clinical Signs of Localized Allergic Reactions • The hypersensitivity reactions are usually mild and localized • Site of the reaction depends on the portal of entry o Inhaled allergens may cause hay fever, an upper respiratory tract response  Marked by watery nasal discharge, sneezing, itchy throat and eyes, and excessive tear production
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