Immune System Disorders Hypersensitivities (≈ Allergies) I) Anaphalactic II) Cytotoxic III) Immune...
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Transcript of Immune System Disorders Hypersensitivities (≈ Allergies) I) Anaphalactic II) Cytotoxic III) Immune...
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Immune System Disorders
Hypersensitivities (≈ Allergies)I) Anaphalactic
II) Cytotoxic
III) Immune Complex
IV) Cell-mediated (Delayed)
Autoimmune Diseases
Transplant Rejection
Hypersensitivity results from a second exposure to what could be normally harmless antigen (≈ allergen). The second response is not an appropriate normal one. The immune system goes too far.
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I) AnaphalaxisAllergies to pollen, pet dander, insect venoms, fungal spores, dust mites, peanuts, & penicillin.
Localized: (asthma, allergic rhinitis; true food allergies)
Systemic (anaphalactic shock): vasodilation throughout body, BP drops; capillaries become porous; edema; constricts brachioles; fatality.
IgE from first exposure to antigen (≈ allergen) bind to mast cells and basophils; the person is “sensitized”.
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Treatment of Anaphalaxis
• Short-Term:
- anti-histamines; epinephrine
- leukotriene receptor blockers
• Long-Term:
- Controlled repeat exposures; boost IgG
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II) Cytotoxic• IgG and IgM antibodies bind to foreign antigens on the
surface of otherwise healthy human blood cell types.
• This results in activation of the complement cascade via the classic pathway, which leads to cytolysis of blood cells with the foreign antigen.
• Further antibody and complement C3b binding results in opsonization (i.e. enhanced phagocytosis by phagocytes) of the blood cells with the foreign antigen.
• Which foreign antigens will cause a cytotoxic reaction?– AB red blood cell (RBC) antigens & Rh RBC antigen
– Drugs (haptens) that bind to blood platelets to become antigenic.
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Transfusion Rh Incompatibility & Hemolytic Disease of the Newbornes
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Thrombocytopenic purpura
Bruising due to low platelet count; poor clotting favors hemorrhages.
Intracerebral hemorrhaging
Stroke
= thrombocyte
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III) Immune ComplexThe right proportions of antigen to IgG antibody results in small immune complexes avoid phagocytosis and instead get stuck beneath endothelial cells of capillaries. Damaging to kidney glomeruli (glomerulonephritis).
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IV) Cell-Mediated (Delayed)Takes days not hours or minutes; requires T cell and macrophage migration to foreign antigen exposure sight.
Allergic Contact Dermatitis:
Latex gloves
Poison ivy
TB skin test is cell-mediated.
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Autoimmune Diseases• Lymphocytes become involved in attacking the bodies own cells (antigens).
• Self-tolerance of lymphocytes is lost: B cells produce antibodies and Tc cells activate their cytotoxicity.
Causes:• Similarities between viral and self antigens (Hepitius C autoimmunity).
• Cell malfunction due to antibody binding (Grave’s Disease; thyroid gland).
• Immune complex forms (rheumatoid arthritis; joints).
• Cell-mediated destruction of specific cell types (insulin-dependent diabetes mellitus; insulin-secreting cells of pancreas).
• Some individuals are genetically predisposed (higher risk) due to specific human leukocyte antigen (HLA) gene alleles that they possess.
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Transplant Rejection• Non-self hypothesis: for most tissues if the HLA classes do not match
there will be rejections by T cell, antibody, and complement attack on transplant blood vessels; see graft-versus-host (GVH) disease.
• This does not apply for privileged sites; those that are non-vascular (cornea, heart valves); rare exceptions.
• Grafts are the new tissues transplanted to a target site.– Autographs; – isographs; – allographs; and – xenographs.
• Immunosuppression by cyclosporine to minimize transplant rejection; its action is suppression of IL-2 release. Other IL-2 receptor blockers are also available (rapamycin).