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Chapter 20. Defenses Against Disease
 

Chapter 20. Defenses Against Disease

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    Chapter 20. Defenses Against Disease Chapter 20. Defenses Against Disease Presentation Transcript

    • Chapter 20. Defenses Against Disease Organs, Tissues & Cells of the Immune System Nonspecific Defenses Specific Defenses Induced Immunity Disorders of Immunity
    • The Immune System: protects against Diesease
      • Nonspecific: defend against and/or attack any pathogen without need to develop special cells or chemicals; no immunological memory formed
      • Specific: involves selection of special immune system cells that target specific pathogens; immunological memory results
    • The lymphatic Organs thymus spleen red bone marrow lymph nodes
      • Primary Lymphatic Organs
        • sites of lymphocyte formation and/or maturation
      • Secondary Lymphatic Organs
        • sites where lymphocytes and other immune system cells encounter and bind antigens
    • Primary Lymphatic Organs
      • Red Bone Marrow: site of all blood cell formation including lymphocytes
        • B lymphocytes formed and mature in red bone marrow
      • Thymus: site of T-lymphocyte maturation
        • T lymphocytes formed in red bone marrow, but mature in thymus
        • T lymphocytes that leave thymus can mount an immune response, but tolerate “self”
    • Secondary Lymphatic Organs
      • Spleen
        • filters blood and stores, contains lymphocytes that participate in immune responses
      • Lymph Nodes
        • filter lymph, contains lymphocytes that participate in immune responses
      • Lymphatic Vessels
        • transport lymph to blood stream, pass through lymph nodes on the way
    • Tissues & Cells of the Immune System
      • Tonsils: aggregations of lymphatic nodules in the pharynx
      • Peyer’s Patches: aggregations of lymphatic tissue in the wall of the intestine
      • Appendix: concentrations of lymphatic tissue
      • Note: lymphatic tissue can be found in the loose connective tissues throughout the body, especially in the walls of organs lined by mucus membranes
    • NonSpecific Body Defenses
      • Physical Barriers
      • Inflammatory Reaction
      • Protective Body Cells
      • Protective Proteins
    • Barriers to Entry
      • Skin and Mucus Membranes
        • secretions of these organs are toxic to bacteria (lysozymes, acids)
        • some organs have resident “beneficial” bacteria that exclude pathogens
    • Inflammatory Reaction
    • Protective Body Cells
      • phagocytes: neutrophils, macrophages
      • natural killer cells: lymphocytes that can attack pathogens and cancer cells without an immune response
    • Protective Proteins
      • Complement: Proteins that attack pathogens directly
      • Interferon: Proteins that are produced by virus infected cells that signal nearby cells to activate antiviral infection mechanisms
    • Specific Defenses
      • B lymphocytes
      • produce antibodies (=antibody mediated or humoral immunity)
      • T lymphocytes
      • attack abnormal body cells, such as those infected with virus (=cell-mediated immunity)
    • Antibody Mediated Immunity
      • clonal selection: only a B cell with the antigen receptor that can bind to the antigen is selected
      • it undergoes proliferation (needs cytokines from helper T cells)
      • some clonal cells become antibody producing plasma cells
      • plasma cells undergo apoptosis when infection is destroyed, but other clone members remain behind as memory cells
    •  
    • Structure of IgG (antibody)
      • Y-shaped protein
      • each arm has a “heavy” (long) peptide and a “light” (short) peptide
      • each peptide has a “constant and a variable region
      • the variable region binds to the antigen
      • there are 4 other classes of antibodies: IgM, IgA, IgD, IgE
    • Antibody Structure
    • Antibody
    • Cell-Mediated Immunity
      • Similar to Antibody mediated, but T Cells cannot bind free antigen in body fluids, antigen must be “presented” by antigen presenting cells (APCs)
      • T cell that can bind presented antigen is activated (selected)
      • undergoes clonal expansion, produces cytokines and a variety of T cell types (killers, helpers, etc.)
      • after immune response most T lymphocytes undergo apoptosis
      • some T cells remain as memory cells
    •  
    • How T Cells “Kill”
    • Cytotoxic, I.e., “Killer” T Cells attacking a cancer cell
    • Helper T Cells
      • provide chemical signals, cytokines, that that regulate and enhance the function of other immune cells
      • HIV virus attacks and destroys Helper T Cells, thereby destroying the immune system
    • Immunosuppression
      • HIV destroys immune system resulting in immune deficiency
      • radiation, by destroying bone marrow, also suppresses immunity
      • various environmental pollutants, dioxins, pesticides suppress immunity
      • certain drugs, such as steroids, suppress the immune system
        • immunosuppression is desirable in organ transplant recipients, but not in most individuals
      • some people are born with a part of their immune system not working
    • Induced Immunity
      • Active immunity: acquired by infection
      • Artificial (induced) immunity: acquired by medical intervention
        • active immunity: individual produces their own immunity by being challenged with the “antigen”
        • passive immunity: individual is given antibodies that convey immunity
    • Immunization (Vaccination)
    • University of Port Harcourt Teaching Hospital Study, Port Harcourt, Nigeria
      • 14 year old boy unconcious with cerebral malaria in Nigeria
      • 10.2 % of childhood deaths
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
    • Two year old with severe measles
      • Measles infects 30 to 40 million children per year
      • Measles kills over 500,000 children per year
      • it costs $1 to immunize a child against measles
                                                                                      
    • 58% 26% 777,000 deaths worldwide
    •  
    • DPT = combined Diptheria, Pertussis, Tetanus vaccine
    • Childhood Mortality: Then & Now
    •  
    •  
    • Passive Immunity by Breastfeeding
    •