1. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Lecture prepared by Mindy Miller-Kittrell, University of Tennessee, Knoxville M I C R O B I O L O G Y WITH DISEASES BY BODY SYSTEM SECOND EDITION Chapter 16 Adaptive Immunity

2. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Overview of Adaptive Immunity Adaptive immunity is the body’s ability to recognize and defend itself against distinct invaders and their products Five attributes of adaptive immunity – Specificity – Inducibility – Clonality – Unresponsiveness to self – Memory

3. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Overview of Adaptive Immunity Involves activity of lymphocytes Two main types of lymphocytes – B lymphocytes (B cells) – Mature in the bone marrow – T lymphocytes (T cells) – Mature in the thymus Two types of adaptive immune responses – Humoral immune responses – Cell-mediated immune responses

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5. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Overview of Adaptive Immunity Animation: Host Defenses: Humoral Immunity: Overview Animation: Host Defenses: Humoral Immunity: Overview Animation: Host Defenses: Cell-Medicated Immunity: Overview Animation: Host Defenses: Cell-Medicated Immunity: Overview

6. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Elements of Adaptive Immunity The Tissues and Organs of the Lymphatic System – Screen the tissues of the body for foreign antigens – Composed of lymphatic vessels and lymphatic cells, tissues, and organs

7. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Elements of Adaptive Immunity The Tissues and Organs of the Lymphatic System – Lymphatic vessels and the flow of lymph – Form a one-way system that conducts lymph from local tissues and returns it to the circulatory system – Lymph is a liquid with similar composition to blood plasma, which arises from fluid leaked from blood vessels into surrounding tissues

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9. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Elements of Adaptive Immunity The Tissues and Organs of the Lymphatic System – Lymphoid organs – Primary lymphoid organs – Red bone marrow – Thymus – Secondary lymphoid organs – Lymph nodes – Spleen – Tonsils – Mucosa-associated lymphatic tissue (MALT)

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11. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Elements of Adaptive Immunity Antigens – Properties of antigens – Molecules the body recognizes as foreign and worthy of attack – Body recognizes antigens by three-dimensional regions called epitopes – Include components of bacterial cell walls, capsules, pili, and flagella, as well as proteins of viruses, fungi, and protozoa – Food and dust can also contain antigenic particles

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14. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Elements of Adaptive Immunity B Lymphocytes (B Cells) and Antibodies – Arise and mature in the red bone marrow – Found primarily in the spleen, lymph nodes, and MALT – Small percentage of B cells circulate in the blood – Major function is the secretion of antibodies

15. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Elements of Adaptive Immunity B Lymphocytes (B Cells) and Antibodies – Specificity of the B cell receptor (BCR) – Each B lymphocyte has multiple copies of a single type of protein called the B cell receptor – Each B cell generates a single BCR – The two variable regions of the BCR form the antigen-binding sites – Each BCR recognizes only one epitope – The entire repertoire of an individual’s BCRs is capable of recognizing millions of different epitopes

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17. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Elements of Adaptive Immunity B Lymphocytes (B Cells) and Antibodies – Specificity and antibody structure – Antibodies are immunoglobulins similar to BCRs – Secreted by activated B cells called plasma cells – Have identical antigen-binding sites and antigen specificity as the BCR of the activated B cell

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19. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Elements of Adaptive Immunity B Lymphocytes (B Cells) and Antibodies – Classes of antibodies – Threats confronting the immune system are variable – The class involved in the immune response depends on the type of foreign antigen, the portal of entry, and the antibody function needed – Five different classes of antibodies

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21. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Elements of Adaptive Immunity B Lymphocytes (B Cells) and Antibodies Antibody function – Antigen-binding sites are complementary to epitopes – Due to the close match can form strong, noncovalent interactions – Hydrogen bonds and other attractions may also be involved – Antibodies function in several ways – Activation of complement and inflammation – Neutralization – Opsonization – Killing by oxidation – Agglutination – Antibody-dependent cellular cytotoxicity (ADCC)

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23. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Elements of Adaptive Immunity Animation: Host Defenses: Humoral Immunity: Antibody Function Animation: Host Defenses: Humoral Immunity: Antibody Function

24. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Elements of Adaptive Immunity T Lymphocytes (T Cells) – Produced in the red bone marrow and mature under the influence of the thymus – Circulate in the lymph and blood and migrate to the lymph nodes, spleen, and Peyer’s patches – Antigen-binding sites are complementary to epitopes – T cells have T cell receptors (TCRs) on their cytoplasmic membrane

25. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Elements of Adaptive Immunity T Lymphocytes – Specificity of the T cell receptor (TCR) – TCRs do not recognize epitopes directly – TCRs only bind epitopes associated with a MHC protein – Act primarily against body cells that harbor intracellular pathogens

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27. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Elements of Adaptive Immunity T Lymphocytes – Types of T lymphocytes – Based on surface glycoproteins and characteristic functions – Three types – Cytotoxic T lymphocyte – directly kills other cells – Helper T lymphocyte – functions to “help” regulate the activities of B cells and cytotoxic T cells – Regulatory T lymphocyte – represses adaptive immune responses

28. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Elements of Adaptive Immunity Animation: Host Defenses: Cell-Mediated Immunity: Cytotoxic T Cells Animation: Host Defenses: Cell-Mediated Immunity: Cytotoxic T Cells

29. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Elements of Adaptive Immunity Animation: Host Defenses: Cell-Mediated Immunity: Helper T Cells Animation: Host Defenses: Cell-Mediated Immunity: Helper T Cells

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31. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Elements of Adaptive Immunity Clonal Deletion – Vital that immune responses not be directed against autoantigens – Body eliminates self-reactive lymphocytes via clonal deletion – Lymphocytes that react to autoantigens undergo apoptosis

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34. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Elements of Adaptive Immunity Immune System Cytokines – Soluble regulatory proteins that act as intercellular signals when released from certain body cells – Immune system cytokines secreted by various leukocytes – The complex web of signals among all the cell types of the immune system is referred to as the cytokine network

35. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Elements of Adaptive Immunity Immune System Cytokines – Interleukins (ILs) – signal among leukocytes – Interferons (IFNs) – antiviral proteins that may act as cytokines – Growth factors – proteins that stimulate stem cells to divide – Tumor necrosis factor (TNF) – Secreted by macrophages and T cells to kill tumor cells and regulate immune responses and inflammation – Chemokines – chemotactic cytokines that signal leukocytes to move

36. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Preparation for an Adaptive Immune Response The Roles of the Major Histocompatibility Complex – Group of antigens first identified in graft patients – Important in determining the compatibility of tissues in successful grafting – Major histocompatibility antigens are glycoproteins found in the membranes of most cells of vertebrate animals – Function to hold and position antigenic determinants for presentation to T cells

37. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Preparation for an Adaptive Immune Response The Roles of the Major Histocompatibility Complex – Antigens bind in the antigen-binding groove of MHC molecules – Two classes of MHC proteins – MHC class I – MHC class II

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40. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Preparation for an Adaptive Immune Response Antigen Processing – Antigens must be processed for MHC proteins to display epitopes – Antigen processing occurs by different processes for endogenous and exogenous antigens

41. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Preparation for an Adaptive Immune Response Animation: Host Defenses: Antigen Processing and Presentation: Overview Animation: Host Defenses: Antigen Processing and Presentation: Overview

42. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Preparation for an Adaptive Immune Response

43. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Preparation for an Adaptive Immune Response

44. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Preparation for an Adaptive Immune Response Animation: Host Defenses: Antigen Processing and Presentation: Steps Animation: Host Defenses: Antigen Processing and Presentation: Steps

45. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Preparation for an Adaptive Immune Response Animation: Host Defenses: Antigen Processing and Presentation: MHC Animation: Host Defenses: Antigen Processing and Presentation: MHC

46. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Cell-Mediated Immune Responses Responds to intracellular pathogens and abnormal body cells The most common intracellular pathogens are viruses but the response is also effective against cancer cells, intracellular protozoa, and intracellular bacteria

47. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Cell-Mediated Immune Responses Activation of T Cell Clones and Their Functions – Steps involved in activation of cytotoxic T cells – Antigen presentation – Helper T cell differentiation – Clonal expansion – Self-stimulation

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49. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Cell-Mediated Immune Responses

50. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Cell-Mediated Immune Responses Animation: Host Defenses: Cell-Mediated Immunity: Cytotoxic T Cells Animation: Host Defenses: Cell-Mediated Immunity: Cytotoxic T Cells

51. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Cell-Mediated Immune Responses

52. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Cell-Mediated Immune Responses Memory T Cells – Some activated T cells become memory T cells – Persist for months or years in lymphoid tissues – Become functional immediately upon subsequent contacts with epitope specific to its TCR

53. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Cell-Mediated Immune Responses T Cell Regulation – Careful regulation of cell-mediated immune response to prevent T cells from responding to autoantigens – T cells require additional signals from an antigen-presenting cell – Interaction of the T cell and antigen-presenting cell at an immunological synapse stimulates the T cell to respond to the antigen

54. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Humoral Immune Responses Body mounts humoral immune responses against exogenous pathogens Activates only in response to specific pathogens

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56. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Humoral Immune Responses [INSERT FIGURE 16.17]

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58. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Humoral Immune Responses Animation: Host Defenses: Humoral Immunity: Clonal Selection and Expansion Animation: Host Defenses: Humoral Immunity: Clonal Selection and Expansion

59. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Humoral Immune Responses Inducement of T-Dependent Humoral Immunity – Plasma cells – Make up the majority of cells produced during B cell proliferation – Each plasma cell secretes only antibody molecules complementary to the specific antigen – Are short-lived cells that die within a few days of activation, though their antibodies and progeny can persist

60. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Humoral Immune Responses Memory B Cells and the Establishment of Immunological Memory – Cells produced by B cell proliferation that do not secrete antibodies – Cells that have BCRs complementary to the specific antigenic determinant that triggered their production – Long-lived cells that persist in the lymphoid tissue – Available to initiate antibody production if the same antigen is encountered again

61. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Humoral Immune Responses

62. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Humoral Immune Responses Animation: Host Defenses: Humoral Immunity: Primary Immune Response Animation: Host Defenses: Humoral Immunity: Primary Immune Response

63. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Humoral Immune Responses Animation: Host Defenses: Humoral Immunity: Secondary Immune Response Animation: Host Defenses: Humoral Immunity: Secondary Immune Response

64. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Humoral Immune Responses Animation: Host Defenses: The Big Picture Animation: Host Defenses: The Big Picture

65. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Types of Acquired Immunity Specific immunity acquired during an individuals life Two types – Naturally acquired – immune response against antigens encountered in daily life – Artificially acquired – response to antigens introduced via a vaccine Further distinguished as either active or passive – Active – active response to antigens via humoral or cell-mediated responses – Passive – passively receive antibodies from another individual

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