Chapter 18 - Hypersensitivities Any immune response against...

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Hypersensitivities • Any immune response against a foreign antigen that is exaggerated beyond the norm • Four types – Type I (immediate) – Type II (cytotoxic) – Type III (immune-complex mediated) – Type IV (delayed or cell-mediated)
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Hypersensitivities Type I (Immediate) Hypersensitivity – Localized or systemic reaction that results from the release of inflammatory molecules in response to an antigen – Develops within seconds or minutes following exposure to an antigen – Commonly called allergy, and the antigens that stimulate it are called allergens
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[INSERT FIGURE 18.1a]
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Hypersensitivities [INSERT FIGURE 18.1b]
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Hypersensitivities Type I (Immediate) Hypersensitivity – Roles of degranulating cells in an allergic reaction • After sensitization, the cells degranulate – Mast cells – Basophils – Eosinophils • And release histamine, kinins, proteases, leukotrienes, and postaglandins
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Hypersensitivities Type I (Immediate) Hypersensitivity – Clinical signs of localized allergic reactions • Usually mild and localized • Site of reaction depends on portal of entry • Small inhaled allergens may reach the lungs and cause asthma • Some foods contain allergens, and may cause diarrhea and other gastrointestinal signs and symptoms • Local dermatitis (inflammation of the skin) may produce hives or urticaria
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Hypersensitivities Type I (Immediate) Hypersensitivity – Clinical signs of systemic allergic reactions • Degranulation of many mast cells at once causes the release of large amounts of histamine and inflammatory mediators • Acute anaphylaxis or anaphylactic shock can result • Clinical signs are those of suffocation, which must be treated promptly with epinephrine
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Hypersensitivities Type I (Immediate) Hypersensitivity – Prevention of type I hypersensitivity • Identification and avoidance of allergens • Food allergens identified using an elimination diet • Immunotherapy (“allergy shots”) can help prevent allergic reactions – Involve the administration of a series of injections of dilute allergen – Must be repeated every two to three years
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Hypersensitivities Type I (Immediate) Hypersensitivity – Treatment of type I hypersensitivity Administer drugs that counteract the inflammatory mediators released by degranulation – Antihistamines neutralize histamine Treated asthma with an inhalant containing corticosteroid and a bronchodilator Administer epinephrine to quickly neutralize many of the mechanisms of anaphylaxis – Relaxes smooth muscle and reduces vascular permeability – Used in the emergency treatment of severe asthma and anaphylactic shock
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Hypersensitivities Type II (Cytotoxic) Hypersensitivity – Results when cells are destroyed by an immune response, often due to the combined activities of complement and antibodies – A component of many autoimmune diseases – Two significant examples • Destruction of blood cells following an incompatible blood transfusion • Destruction of fetal red blood cells in hemolytic disease of the newborn
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This note was uploaded on 05/24/2011 for the course BIO 119 taught by Professor Stevendroho during the Spring '11 term at Moraine Valley Community College.

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Chapter 18 - Hypersensitivities Any immune response against...

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