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Unformatted text preview: Microbiology Chapter 16: Disorders In Immunity: Although the immune system is a precisely coordinated system that seeks out, recognizes, and destroys an unending array of foreign materials, it also has another side that promotes rather than prevents disease. Immunopathology is the study of disease states associated with overreactivity or underactivity of the immune response. Overreactions to Anigens: Allergy/Hypersensitivity: Allergy: A condition of altered reactivity or exaggerated immune response that is maanifested by inflammation. Allergic individuals are acutely sensitive to repeated contact with antigens, called allergens, that do no noticeably affect non allergic individuals. Antigens that trigger hypersensitivity eactions are allergens. They can be either exogenous (originate outside of the host) or engodenous (involve the host's own tissue). Allergens typically enter through epithelial portals in the respiratory tract, gastrointestinal tract, and skin. The mucosal surfaces of the gut and respiratory system present a thin, moist surface that is normally quite pentrable. The dry, tough keratin coating of skin is less penetrable. But access still occurs through tiny breaks, glands, or hair follicles. Common Portals of entry: Inhalants, Ingestants, Injectants, Contactants. There are 4 Hypersensitivity States: Type 1 : Immediate hypersensitivity. These allergies are immediate in onset, and are associated with exposure to specific antigens. There are two levels of severity to type 1 hypersensitivities. The first is atopy, or a chronic local allergy such as hay fever or asthma. The second level is anaphylaxis, which is a systemic and sometimes fatal reaction that involves airway obstruction and circulatory collapse. Type 1 is IgE mediated. It involves mast cells, basophils, and allergic mediators. The predisposition for type I allergies has a strong familial association. The actual basis for atopy appears to be a genetic program that favors allergic antibody (IgE production), increased reactivity of mast cells, and increased susceptibility of target tissue to allergic mediators. Other factors that affect the presence of allergy are age, infection, and geographic locale. Some atopic allergies last a lifetime; others "outgrow" them. and still others suddenly develop them later in life. Mechanisms of Type 1 Allergy: Sensitization and Provocation: The initial encounter with an allergen provides a sensitizing dose that primes the immune system for a subsequent encounter with that allergen but generally elicits no signs or symptoms. The memory cells and immunoglobulin are then allergen but generally elicits no signs or symptoms....
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This note was uploaded on 02/14/2012 for the course BIO 226N taught by Professor Blinkova during the Summer '08 term at University of Texas at Austin.
- Summer '08