1 / 84

Chapter 22: The Lymphatic System and Immunity

Chapter 22: The Lymphatic System and Immunity. BIO 211 Lecture Instructor: Dr. Gollwitzer. Today in class we will discuss: Body defenses and the components, mechanisms and functions of: Nonspecific defenses Physical Barriers Phagocytes Immunological surveillance Interferons

gparsons
Télécharger la présentation

Chapter 22: The Lymphatic System and Immunity

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Chapter 22: The Lymphatic System and Immunity BIO 211 Lecture Instructor: Dr. Gollwitzer

  2. Today in class we will discuss: • Body defenses and the components, mechanisms and functions of: • Nonspecific defenses • Physical Barriers • Phagocytes • Immunological surveillance • Interferons • Complement system • Inflammatory response • Fever • Specific defenses • Immune response • T cells • B cells • Types of immunity • Properties of immunity

  3. Immune System • A physiological system that includes several organ systems • Primary = lymphatic system • Plus components of integumentary, cardiovascular, respiratory, digestive, and other anatomic systems • e.g., interactions between lymphocytes and Langerhans cells of skin important in defenses against skin infections

  4. Immune System • Specialized sensory “megaorgan” • Enables us to detect things that are foreign or cannot be seen with the naked eye (microbes, allergens…) • Allows us to fight (defend against) pathogenic microbes while normal flora left alone

  5. Body Defenses • Physical and chemical barriers that prevent or slow entry/progress of infectious organisms • 2 Types of defenses • Nonspecific defenses • Specific defenses

  6. Body Defenses • Nonspecific defenses • NOT unique • Against any invading agent • Many different threats elicit same response • Present from birth (innate) • e.g., physical barriers, phagocytic cells, immunological surveillance, interferons, complement, inflammation, fever

  7. Body Defenses • Specific defenses (AKA: Adaptive defenses) • Protect against specific threats (e.g., one type of bacterium or virus) • Develop after birth as a result of exposure • Depend on activities of lymphocytes • Result in specific resistance or immunity = ability to resist infection and disease through activation of specific defenses

  8. Nonspecific Defenses Figure 22-11

  9. Nonspecific Defenses:Physical Barriers • Keep pathogens from entering body • Epithelial linings • Skin surface layers with keratin and desmosomes water resistant, impregnable wall • Epithelial accessory structures (e.g., hair, cilia) • Protect against mechanical abrasion • Prevent hazardous contact with skin • Epithelial secretions • Mechanical barrier, e.g., mucous in respiratory tract, stomach • Antibacterial, e.g. sebum (oily secretion from sebaceous gland), lysozyme enzyme in tears • Flushing action (tears, urine, mucus in respiratory tract)

  10. Nonspecific Defenses:Phagocytes • Perform “police,” “first-responder,” “janitorial” services in peripheral tissues • First line of cellular defense • Roving cells on look-out for foreign invaders • Remove pathogens and cell debris (cell eaters) • Often attack and remove invaders before lymphocytes aware of them • Attracted to chemicals (chemotaxis) • Chemicals released: • From damaged body cells • By pathogens into surrounding fluids, e.g., cytokines • Move out of bloodstream by squeezing between endothelial cells (diapedesis)

  11. Nonspecific Defenses:Phagocytes • Must be activated • Respond to invasion by foreign compounds or pathogens in several ways • Engulf pathogen or foreign object and destroy with lysozymes • Bind or remove pathogen from interstitial fluid but not able to destroy without assistance from other cells • Destroy pathogen by releasing: • TNF (tumor necrosis factor), NO (nitric oxide), or H2O2 (hydrogen peroxide) • Brief lifespan for active phagocytes (30 min – 1 hr)

  12. Nonspecific Defenses:Phagocytes • 2 Classes of phagocytes • Microphages (“small eaters”) • Macrophages (“big eaters”)

  13. Nonspecific Defenses:Microphages • Circulating neutrophils and eosinophils that leave bloodstream and enter injured or infected tissues • Neutrophils • Abundant, quick, mobile • Engulf pathogens or cellular debris • Eosinophils • Much rarer cells • Target foreign compounds or pathogens (antigens) coated with antibodies, e.g., allergens

  14. Nonspecific Defenses:Macrophages • Large, actively phagocytic cells derived from monocytes • Spend very little time in blood • 2 Types • Fixed/resident macrophages • Permanent cells in certain tissues, e.g., • Microglia in CNS, Kupffer cells in liver, alveolar macrophages in lungs • Free macrophages • Mobile; travel throughout body through tissues or blood

  15. Nonspecific Defenses: Immunological Surveillance • Immune system programmed to ignore cells of own body (e.g., intestinal bacteria) unless they become abnormal • Normal tissues constantly monitored by natural killer (NK) cells looking for: • Abnormal cells (cancer cells with tumor-specific antigens) • Cells infected with viruses

  16. Nonspecific Defenses: Immunological Surveillance • NK cells • Lymphocyte “spy system” in peripheral tissue • Recognize/respond to wide variety of proteins on cell membranes • vs. T cells or B cells that can be activated only by exposure to a specific antigen at a specific site on a cell membrane • Respond immediately on contact with abnormal cell • Much more rapidly than T or B cells whose activation is complex and time consuming

  17. Nonspecific Defenses: Immunological Surveillance • NK cell • Attaches to abnormal cell • Producess protein (perforin) that creates large pores in cell membrane  lyses cell • Especially important opponent for cancer cells

  18. How NK Cells Kill Cellular Targets Fig. 22-12

  19. Nonspecific Defenses:Interferons • Small protein chemical messengers (type of cytokine) produced by: • Macrophages • Cells infected with viruses • Activated lymphocytes • Interfere with spread of disease • Coordinate local defenses against viral infection • Stimulate macrophages and NK cells • Signal WBCs and lymphatic system (“tattle tales”) • Increase resistance of cells to viral infections • Trigger production of antiviral proteins that inhibit replication within cells

  20. Nonspecific Defenses:Complement System • System of 11 blood proteins that interact in a chain reaction (cascade) • Assists (complements, supplements) antibodies in destroying pathogens • Begins when first complement protein (C1) binds to antibody (Ab) attached to its specific antigen • Ends with pore formation and lysis of target cell membrane

  21. Complement System Figure 22–12, 7th edition

  22. Nonspecific Defenses:Complement System • Attracts phagocytes to injury or infection (via chemotaxis) • Enhances phagocytosis of antibody-antigen (pathogen) complex • Stimulates inflammation • Enhances histamine release by mast cells (basophils in tissues) • Increases local inflammation and accelerates blood flow

  23. Nonspecific Defenses:Inflammation • Local tissue response to injury or infection • Stimulus • Anything that changes cell and alters chemical composition of interstitial fluid • Anything that kills cells, damages CT fibers, or injures tissue • e.g., impact, abrasion, chemical irritation, infection by pathogens, extreme temperatures

  24. Nonspecific Defenses:Inflammation • Stimulus causes mast cells  • Histamine • Heparin •  • Local vasodilation  increased blood flow redness and heat • Increased capillary permeability  blood proteins into injured tissue  local swelling • Stimulation of pain receptors  pain

  25. Nonspecific Defenses:Inflammation • Inflammatory response • Walls off region, slows spread of injury/ pathogens from site • Combats infection by activating: • Phagocytes • Complement • Specific defenses • Performs temporary repair and prevents access of other pathogens • Mobilizes regeneration (permanent repair)

  26. Figure 22-15

  27. Nonspecific Defenses:Fever • High body temperature (>99 F) • Caused by pyrogens • = Proteins released by macrophages that can raise body temperature • Affect temperature-regulating center in hypothalamus • Stimuli for pyrogens • Pathogens • Bacterial toxins • Antigen-antibody complexes • Act directly as pyrogens • Stimulate release of pyrogens by macrophages

  28. Nonspecific Defenses:Fever • Beneficial phenomenon • Increases body’s metabolic rate so more enzyme made to fight infection • Inhibits pathogenic enzymes • Stimulates cell repair

  29. Specific/Adaptive Defenses:The Immune Response • Immunity • Specific resistance to injury and disease caused by foreign compounds, toxins, or pathogens • Provided by coordinated effort of 2 types of lymphocytes: T and B cells • Lymphocytes • Respond to presence of specific antigens • “Organize” the defense

  30. Figure 22-17

  31. Specific Defenses:The Immune Response • T cells (thymus-dependent) • Initiate, maintain, control the immune response • Responsible for cell-mediated immunity • Defend against abnormal cells and pathogens inside cells (do not respond to pathogens in body fluids) • 3 Major types of T cells • Cytotoxic • Helper • Suppressor

  32. Specific Defenses:The Immune Response • B cells (bone marrow-derived) • Responsible for antibody-mediated (humoral) immunity • Differentiate into plasma cells that produce antibodies • Defend against antigens and pathogens in body fluids (antibodies can’t cross cell membranes)

  33. Specific Defenses:The Immune Response • Types of immunity • Innate immunity • Present at birth (genetically determined) • Does not require exposure to antigen or antibody production •  Diseases that are species specific • Acquired/Adaptive immunity • Not present at birth • Produced by prior exposure to specific antigen or antibody production • 4 types

  34. Figure 22-14, 7th edition

  35. Specific Defenses: Acquired Immunity • Active immunity • Appears after exposure to an antigen • Requires active response by body, i.e., antibody production (immune response) • Two types • Naturally acquired (active) immunity • Through environmental exposure to pathogens • Induced (active) immunity • Through vaccines containing dead/inactive pathogens or antigens • Antibody production stimulated before possible future exposure

  36. Specific Defenses: Acquired Immunity • Passive immunity • Requires no response by body • Produced by transfer of antibodies from one individual to another • Two types • Natural passive immunity • Antibodies acquired from mother during development (across placenta) or in early infancy (through breast milk) • Induced passive immunity • Antibodies (developed in another body) administered via injection • e.g., IG injected into Rh- mother after first Rh+ baby; antirabies virus antibodies injected into person bitten by rabid animal, antivenom…snake bite

  37. Specific Defenses:The Immune Response • Properties of immunity that enable body to respond with a specific defense • Specificity • Versatility • Memory • Tolerance

  38. Specific Defenses:4 Properties of Immunity • Specificity • Specific defenses activated by one specific antigen • Immune response targets that antigen ONLY • Each T and B lymphocyte has receptors that bind to only one specific antigen and ignore all others • T or B cells will destroy or inactivate that antigen without affecting other antigens or normal tissues

  39. Specific Defenses:4 Properties of Immunity • Versatility • Ability of immune system to confront any antigen any time • Results from large diversity of lymphocytes in body • During development, cell differentiation in lymphatic system produces millions of different lymphocyte populations (each has several 1000 identical cells) • Each lymphocyte population responds to a different antigen • Several 1000 lymphocytes not enough to overcome pathogenic invasion, but begin dividing when activated in presence of appropriate antigen • Produce more lymphocytes with same specificity  clone

  40. Specific Defenses:4 Properties of Immunity • Memory • Lymphocytes remember antigens they’ve encountered before • During initial response to antigen, lymphocytes undergo repeated cycles of cell division • Produce 2 types of cells • Activated lymphocytes that attack antigen invader • Memory cells that remain inactive until exposed to same antigen again at a later time • After second exposure, response is faster, stronger, and lasts longer than first time

  41. Specific Defenses:4 Properties of Immunity • Tolerance • Immune system • Ignores “normal” (self) antigens • Attacks foreign (nonself) antigens • Can also develop in response to chronic (long-term) exposure to antigen in environment; lasts only as long as exposure continues • Failure  autoimmune diseases

  42. Today in class we will discuss: • The immune process • Antigens • T cells • B cells • Types of immune responses • Cell-mediated immunity • Antigen presentation • Antigen recognition • T cell activation • Destruction/elimination of target cell/antigen

  43. Immune Response Process • Antigen • = Foreign substance capable of inducing antibody production • Triggers immune response • Activates • Phagocytes  activation of T cells • B cells

  44. Immune Response Process • T cells • Initiate, maintain, control immune response • Carry out direct physical/chemical attack on antigen • Stimulate activation of B cells • B cells • Mature into plasma cells that produce antibodies • Antibodies in bloodstream bind to/attack antigen  antigen-antibody complex that is eliminated from system

  45. Figure 22-17

  46. Immune Responses • 2 types • Cell-mediated immunity (T cells) • Antibody-mediated (humoral) immunity (B cells)

  47. Immune Responses • Cell-mediated immunity • Involves T cells • Process • Antigen presentation • Antigen recognition • T cell activation • Destruction/elimination of target cell/antigen (cytotoxic T cells)

  48. T Cells and Cell-mediated Immunity • Antigen presentation • = Process whereby foreign antigen is displayed (“presented”) on cell membrane • Requires combining foreign antigen + glycoprotein (e.g., MHC protein) Antigen = foreign peptide that has potential to induce antibody formation

  49. T Cells and Cell-mediated Immunity • MHC proteins • Membrane glycoproteins • Synthesis controlled by group of genes called the major histocompatability complex (MHC) • Bind antigens • Differ among individuals • Two classes of MHC proteins • MHC I • MHC II

  50. T Cells and Cell-mediated Immunity • MHC I proteins • Continuously being formed in allnormal, healthy cells that have a nucleus • MHC II proteins • In: • Antigen-presenting cells (APCs) • Present only when cell actively processing foreign antigen • Lymphocytes (B cells and helper T cells) NOTE: these cells also have MHC I proteins

More Related