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Chapter 20. Defenses Against Disease
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Chapter 20. Defenses Against Disease


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  • 1. Chapter 20. Defenses Against Disease Organs, Tissues & Cells of the Immune System Nonspecific Defenses Specific Defenses Induced Immunity Disorders of Immunity
  • 2. 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
  • 3. 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
  • 4. 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”
  • 5. 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
  • 6. 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
  • 7. NonSpecific Body Defenses
    • Physical Barriers
    • Inflammatory Reaction
    • Protective Body Cells
    • Protective Proteins
  • 8. 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
  • 9. Inflammatory Reaction
  • 10. Protective Body Cells
    • phagocytes: neutrophils, macrophages
    • natural killer cells: lymphocytes that can attack pathogens and cancer cells without an immune response
  • 11. 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
  • 12. 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)
  • 13. 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
  • 14.  
  • 15. 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
  • 16. Antibody Structure
  • 17. Antibody
  • 18. 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
  • 19.  
  • 20. How T Cells “Kill”
  • 21. Cytotoxic, I.e., “Killer” T Cells attacking a cancer cell
  • 22. 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
  • 23. 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
  • 24. 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
  • 25. Immunization (Vaccination)
  • 26. 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
  • 27. 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
  • 28. 58% 26% 777,000 deaths worldwide
  • 29.  
  • 30. DPT = combined Diptheria, Pertussis, Tetanus vaccine
  • 31. Childhood Mortality: Then & Now
  • 32.  
  • 33.  
  • 34. Passive Immunity by Breastfeeding
  • 35.