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Chapter 24: The Immune System

This chapter provides an overview of the immune system, including its anatomy, function, and defense mechanisms against pathogens and foreign molecules. It covers topics such as non-specific body defenses, specific defenses against pathogens, combined defenses against bacteria and viruses, and allergies and autoimmune problems.

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Chapter 24: The Immune System

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  1. Chapter 24 The Immune System

  2. About this Chapter • Anatomy & function of immune system, organs, & cells • How the body defends itself • Non-specific body defenses • Specific defenses that target one pathogen • Combined defenses against bacteria and viruses • Allergies and autoimmune problems

  3. Immune System Functions: Overview of Defenses • Scavenge dead, dying or abnormal (cancerous) body cells • Protect from pathogens & foreign molecules • Parasites • Bacteria • Viruses

  4. Immune System Functions: Overview of Defenses Figure 24-1: Viruses

  5. HIV or Human Immunodeficiency Virus

  6. Infectious Causes of Gastroenteritis. Bok K, Green KY. N Engl J Med 2012;367:2126-2132.

  7. Body Defenses: Overview • Physical barriers: skin & epithelial linings & cilia • Chemical: acids, mucous & lysozymes • Immune defenses – internal • Innate, non-specific, immediate response (min/hrs) • Acquired – attack a specific pathogen (antigen) • Steps in Immune defense • Detect invader/foreign cells • Communicate alarm & recruit immune cells • Suppress or destroy invader

  8. Lymphatic System: Overview of Immune Defense Organs & Cells • Bone marrow • Thymus • Lymph nodes • Spleen • Lymph vessels • Leukocytes: • (white blood cells – WBCs)

  9. Lymphatic System: Overview of Immune Defense Organs & Cells Figure 24-2 ab: Anatomy of the immune system

  10. Key Cells & Overview of their Function in Immune Defense • Lymphocytes: helper, plasma, cytotoxic & natural killer (NK) • Basophils • Mast cells • Monocytes • Macrophages • Neutrophils • Eosinophils

  11. Key Cells & Overview of their Function in Immune Defense Figure 24-4: Cells of the immune system

  12. Innate Immunity: Phagocytosis & Inflammation • Physical & chemical barriers • Phagocytosis: macrophages, neutrophils, NK cells • Engulf and digest recognized "foreign" cells – molecules • Inflammatory response

  13. Innate Immunity: Phagocytosis & Inflammation Figure 24-6: Phagocytosis

  14. Cells of the Innate Immune System The Innate Leukocytes include: • Natural killer cells • Mast cells • Eosinophils • Basophils • Phagocytic cells: including macrophages, neutrophils and dendritic cells, and All these cells function within the immune system by identifying and eliminating pathogens that might cause infection

  15. Chemical factors produced during inflammation • Histamine • Bradykinin • Serotonin • Leukotrienes • Prostaglandins sensitize pain receptors, cause vasodilation of the blood vessels at the scene, and attract phagocytes, especially neutrophils

  16. Inflammatory Response: Cytokines Signal Initiation • Histamines: from mast cells  swelling, edema, b. v . dilation • Interleukins: fever, b.v. gaps  WBC's & proteins  infection • Bradykinin: pain & swelling • Membrane attack complex proteins

  17. Inflammatory Response: Cytokines Signal Initiation Figure 24-8: Membrane attack complex

  18. Acquired Immunity: Antigen-Specific Responses • Activate T lymphocytes: direct attack • Activate B lymphocytes to become: • Memory cells: 20 immune response to that antigen • Plasma cells: antibodies – attack that antigen

  19. Antigen Presentation to Immature T Cells Antigen presentation stimulates T cells to become either "cytotoxic" CD8+ cells or "helper" CD4+ cells. Cytotoxic cells directly attack other cells carrying certain foreign or abnormal molecules on their surfaces. Helper T cells, or Th cells, coordinate immune responses by communicating with other cells. In most cases, T cells only recognize an antigen if it is carried on the surface of a cell by one of the body’s own MHC, or major histocompatibility complex, molecules.

  20. T Cell Dependent B Cell Activation A TH2 cell (left), B cell (right), and several interaction molecules

  21. B Cell Activation

  22. ANTIBODIES STRUCTURE CLASS

  23. ANTIBODIES POLYCLONAL. MONOCLONAL. Derived from different B Lymphocytes cell lines Derived from a single B cell clone mAb offer Reproducible, Predictable & Potentially inexhaustible supply of Ab with exquisite specificity Batch to Batch variation affecting Ab reactivity & titre NOT Powerful tools for clinical diagnostic tests Enable the development of secure immunoassay systems.

  24. Acquired Immunity: Antigen-Specific Responses Figure 24-13: Functions of antibodies

  25. The Human Leukocyte Antigen (HLA) System • Essential to immune function: HLA molecules present peptide antigens to the immune system (T-cells) • Important for self versus non-self distinction

  26. HLA Class I Monitors Inside of the Cell Tapasin CR CN Dr. Brian Freed

  27. HLA Class II Monitors Outside of Cell Peptides Extra-cellular Proteins DM monitors peptide specificity for DR DM Dr. Brian Freed

  28. Humoral Versus Cellular Immune Response

  29. Class I (1.1 Mb) Class III (0.7 Mb) Complement & cytokines Class II (2.2 Mb)

  30. Transplantion

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