chapter 7 - Chapter 7 Altered Immune Response Allergy...

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Chapter 7 Altered Immune Response Allergy – immune response exaggerated against environmental antigens (most common, least life threatening) Autoimmunity – immune response is misdirected against the host’s own cells. Body against self. Alloimmunity – immune response directed against beneficial foreign tissues, such as transfusions or transplants Immune deficiency – immune response insufficient for protection due to a disease or drugs such as chemo. Hypersensivity Requires sensitization against a particular antigen that initiates primary immune response; disease symptoms appear after an adequate secondary response Pathologic immune response to an antigen after reexposure and results in damage to individual o Immediate-minutes to a few hours o Delayed-several hours or at reexposure Genetic, infectious, and possibly environmental agents contribute to hypersensitivity Auto-antibodies – Antibodies against self antigens Most rapid and severe immediate hypersensitivity reaction is anaphylaxis (airways constrict) *can be systemic (generalized) or cutaneous (localized) When the immune system overreacts, hypersensitivity disorders such as allergies and autoimmune diseases may occur. o Type I Reaction (anaphylactic / atopic) o Type II Cytotoxic and Cytolytic Reactions o Type III Immune –Complex Reactions o Type IV Delayed Hypersensitivity Reactions *four mechanisms are interrelated and usually several mechanisms can work simultaneously Type 1 Reactions (IgE mediated reaction) *mast cells Occurs in susceptible persons who are highly sensitized to specific allergens Most potent mediator - Histamine IgE antibodies o Ige has short lifespan because it binds to Fc receptors on mast cells Fc receptors that bind to IgE that has not previously interacted with antigen (different from phagocytic Fc receptors which bind IgE that already reacted with antigen) After a lot of IgE is bound to mast cell, individual is considered sensitized and additional exposure of individual to antigen results in degranulation of mast cell o Most potent IgE: histamine H1: bronchial constriction, increases vascular permeability (edema), and vasodilation H2: increased gastric secretions **1 st Exposure **Subsequent exposures --example: eating peanuts and one day your allergic because antibodies finally built up Anaphylaxis (immediate reaction) can occur when mediators are released systemically (e.g. , after injection of a drug or after an insect sting). o Most rapid and severe hypersensitivity reaction o Tongue and throat swells **can give ephinephren (epi pen) to help with bleeding Clinical Manifestations Gastrointestinal allergy – enters through mouth (medicines or usually foods) causes cramping, vomiting, diarrhea and abdominal pain Urticaria / Hives – localized release of histamine causing areas of edema, wheal and flare reaction and itching Conjunctivitis / Rhinitis / Asthma (symptoms caused by vasodilation, increased mucus, and swelling of respiratory
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chapter 7 - Chapter 7 Altered Immune Response Allergy...

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