Chapter 22 Outline (edited by Cang Nguyen on Ultimeaciax-NB @ 1-17-2007 4-37-00 PM)

Chapter 22 Outline (edited by Cang Nguyen on Ultimeaciax-NB @ 1-17-2007 4-37-00 PM)

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Chapter 22 Immune Disorders Introduction 22.1 Type I IgE-Mediated Sensitivity Type I Hypersensitivity Is Induced by Allergens o The sensitizing dose is the first dose of antigen, to which the immune system responds as it would a pathogen o The person is sensitized as IgE antibodies attach to mast cells and basophils o On subsequent allergen exposure, IgE antibodies are cross-linked, causing degranulation which releases mediator substances: Histamine is released into the blood, disseminates, and causes smooth muscle cell constriction Leukotrienes are potent smooth muscle constrictors Prostaglandins can constrict bronchial tubes Cytokines can also stimulate inflammation Systemic Anaphylaxis Is the Most Dangerous Form of a Type I Hypersensitivity o Allergens in the bloodstream can trigger mast cell degranulation that contracts smooth muscle o Small veins constrict and capillary pores expand, forcing fluid into the tissues A drop in blood pressure, edema, and rash occur o Contractions in the gastrointestinal tract and bronchial muscles cause cramps and shortness of breath o The lungs fill with carbon dioxide, which can cause death by asphyxiation in 10-15 minutes Atopic Disorders Are the Most Common Form of a Type I Hypersensitivity o Atopic disease is a common (seasonal) allergy caused by the inhalation of pollen o Year-round allergies can result from chronic exposure to allergens o Food allergies can cause symptoms like swollen lips, abdominal cramps, nausea, diarrhea, hives, and anaphylaxis o Physical factors like extreme temperatures, sunlight, or sweating can cause allergies o Exercise can cause allergies in the form of an asthma attack Allergic Reactions Also Are Responsible for Triggering Many Cases of Asthma o Asthma can be caused by airborne allergens, exercise, or cold temperature o Degranulation of mast cells releases mediators in the lower respiratory tract, causing brochoconstriction, vasodilation, and mucus buildup
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o Recruitment of eosinophils and neutrophils into the lower respiratory tract can cause tissue injury and airway blockage Why Do Only Some People Have IgE-Mediated Hypersensitivities?
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