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Chapter 17

Chapter 17. Specific Defenses of the Host: The Immune Response. Differentiate between innate and acquired immunity. Specific Defenses of the Host: The Immune Response. Differentiate between immunity and nonspecific resistance.

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Chapter 17

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  1. Chapter 17 Specific Defenses of the Host: The Immune Response

  2. Differentiate between innate and acquired immunity.

  3. Specific Defenses of the Host:The Immune Response Differentiate between immunity and nonspecific resistance. • Innate (nonspecific) Defenses against any pathogen, genetically predetermined resistance (gender, age, nutrition) • Immunity Specific antibody and lymphocyte response to an antigen (counteract infection) • Antigen (Ag) A substances that causes the body to produce specific antibodies or sensitized T cells • Antibody (Ab) Proteins made in response to an antigen

  4. Terminology • Acquired immunity Resistance to infection during life of host • Naturally acquired Resulting from infection, may be active immunity long-lasting • Serology Study of reactions between antibodies and antigens • Antiserum Generic term for serum because it contains Ab • Globulins Serum proteins • Gamma () globulin Serum fraction containing Ab

  5. Serum Proteins – separation by gel electrophoresis • Immune serum globulin or gamma globulin Figure 17.2

  6. The Immune Response Differentiate between humoral (antibody-mediated) and cell-mediated immunity. • Acquired immunity Developed during an (vaccination) individual's lifetime • Humoral immunity Involves Ab (antibodies) (in body fluids) produced by B cells • Defend against bacteria, viruses, toxins in blood plasma and lymph • Cell-mediated immunity Involves T cells (certain lymphocytes) • Response to intracellular bacteria, viruses, parasites, transplanted tissue, cancer cells

  7. Acquired Immunity Contrast the four types of acquired immunity. • Naturally acquired active immunity • Resulting from infection • Naturally acquired passive immunity • Transplacental or via colostrum • Artificially acquired active immunity • Injection of Ag (antigen - vaccination) • Artificially acquired passive immunity • Injection of Ab (antibody) or antiserum

  8. Antigenic Determinants (epitopes) Define antigen and hapten. • Antibodies recognize and react with antigenic determinants or epitopes (specific regions on surface of antigen). • Antigens cause body to produce specific antibodies. Are components of invading microbes generally. Figure 17.3

  9. Haptens • Hapten is a molecule too small to stimulate antibody formation by itself, until combined with larger carrier molecule like a serum protein, becoming an antigen. Figure 17.4

  10. Antibody Structure (Immunoglobulin) – protein produced by B cells in response to antigen • Explain the function of antibodies and describe their structural and chemical characteristics. Figure 17.5a-c

  11. IgG antibodies Name one function for each of the five classes of antibodies. • Monomer (single bivalent antibody unit) • 80% of serum antibodies • Fix complement • In blood, lymph, intestine • Cross placenta • Enhance phagocytosis; neutralize toxins & viruses; protects fetus & newborn • Half-life = 23 days

  12. IgM antibodies • Pentamer (5 monomers) • 5-10% of serum antibodies • Fix complement • In blood, lymph, on B cells • Agglutinates microbes; first Ab produced in response to infection • Half-life = 5 days

  13. IgA antibodies • Dimer • 10-15% of serum antibodies • In secretions • Mucosal protection • Half-life = 6 days

  14. IgD antibodies • Monomer • 0.2% of serum antibodies • In blood, lymph, on B cells • On B cells, initiate immune response • Half-life = 3 days

  15. IgE antibodies • Monomer • 0.002% of serum antibodies • On mast cells and basophils, in blood • Allergic reactions; lysis of parasitic worms • Half-life = 2 days • Involved in allergic reactions

  16. Clonal Selection Name the function of B cells. • Humoral (fluid) immunity involves antibodies produced by B cells • Bone marrow gives rise to B cells. • Mature B cells migrate to lymphoid organs. • A mature B cells recognizes epitopes (antigen receptor).

  17. Differentiation of T cells and B cells, both from stem cells in adult red bone marrow or fetal liver

  18. Define apoptosis, and give a potential medical application. • Apoptosis – normal B cell below, B cell above undergoing apoptosis (bubble-like blebs) • Programmed cell death to prevent overpopulation of B cells

  19. Clonal Selection & Differentiation of B cells • Each particular B cell recognizes only one type of antigen, activating the B cell • Produces clone of plasma cells (antibodies) and memory cells Describe the clonal selection theory. Figure 17.8

  20. Self-tolerance Explain how an antibody reacts with an antigen; identify the consequences of the reaction. • Antigen-antibody complex can result in agglutination, inflammation, lysis • Body doesn't make Ab against self • Clonal deletion • The process of destroying B and T cells that react to self antigens • Amount of antibody in serum called antibody titer

  21. Protective Mechanism of Ag-Ab Binding • Result of antigen-antibody binding • Tags foreign cells and molecules for destruction by phagocytes and complement (serum proteins for phagocytosis and lysis of cells) Figure 17.9

  22. Primary and secondary immune response to antigen • Distinguish a primary from a secondary immune response. • IgM appears first (primary response) • IgG follows and provides longer-term immunity (high antibody titer) Figure 17.10

  23. Monoclonal Antibodies Define monoclonal antibodies and identify their advantage over conventional antibody production. • Hybridomas are produced by fusing a cancer cell with an Ab-secreting plasma cells • The hybridoma cell culture is immortal and produces monoclonal Abs (Mabs) – serologic identification tests, prevent tissue rejections • Immunotoxins: Mabs conjugated with a toxin to target cancer cells • Chimeric Mabs: Genetically modified mice that produce Ab with a human constant region • Humanized Mabs: Mabs that are mostly human, except for mouse antigen-binding

  24. Monoclonal Antibodies

  25. Immune system cells communicate via cytokines • Identify at least one function of each of the following in cell-mediated immunity: cytokines, interleukins, interferons. • Interleukin-1 Stimulates TH cells • Interleukin-2 Activates TH, B, TC, and NK cells • Interleukin-12 Differentiation of CD4 cells • -Interferon Increase activity of macrophages • Chemokines Cause leukocytes to move to an infection

  26. Chemical messengers: Cytokines • Cells of immune system communicate via cytokines • Interleukins (IL) are cytokines between leukocytes • Interferons protect cells against viruses • Chemokines cause leukocytes to move to infection site

  27. Cell-Mediated Immunity • Specialized lymphocytes, mostly T cells, respond to intracellular Ags • After differentiating in the thymus, T cells migrate to lymphoid tissue • T cells differentiate into effector T cells when stimulated by an Ag • Some effector T cells become memory cells

  28. Pathogens entering the gastrointestinal or respiratory tracts pass through: • M (microfold) cells in • Peyer's patches which contains • Dendritic cells which are antigen-presenting cells and • T cells

  29. Dendritic cells present antigens Figure 17.12

  30. T Cells Describe at least one function for each of the following: TH1 cell, TH2 cell, TC cell, TD cell, TS cell, APC, MHC,activated macrophage, NK cell. • Helper T Cells (CD4, TH) • TH1 Activate cells related to cell-mediated immunity • TH2 Activate B cells to produce eosinophils, IgM, and IgE • Cytotoxic T Cells (CD8, TC) • Destroy target cells with perforin

  31. T Cells • Delayed Hypersensitivity T Cells (TD) • Associated with allergic reaction, transplant rejection, and tuberculin skin test • Suppressor T cells (TS) • Turn off immune response when Ag no longer present

  32. Helper T Cells Figure 17.13

  33. Cell-mediated Cytotoxicity Figure 17.14

  34. Nonspecific Cells – Activated Macrophages • Activated macrophages: Macrophages stimulated by ingesting Ag or by cytokines • Natural killer cells: Lymphocytes that destroy virus-infected cells, tumor Figure 17.15

  35. T-independent Antigens • T-indep. antigen has repeating units that cross-link several antigen receptors on same B cell B cell Compare and contrast T-dependent antigens and T-independent antigens.

  36. Describe the role of antibodies and NK cells in antibody-dependent cell-mediated cytotoxicity.

  37. T-independent Antigens • How helper T cells may activate B cells to make antibodies against T-dependent antigens Figure 17.16

  38. Antibody-Dependent Cell-Mediated Cytotoxicity Compare and contrast cell-mediated and humoral immunity. • Eosinophils adhering to larval stage of parasitic fluke Figure 17.18

  39. Duality of immune system

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