Lymphatic system and body defenses

1. Lymphatic system and body defenses • Nonspecific defenses • Do not distinguish one type of threat from another • 7 types • Specific defenses • Protect against particular threats • Depend upon the activation of lymphocytes

2. SECTION 22-3Nonspecific Defenses

3. Nonspecific Defenses, Physical barriers • Keep hazardous organisms outside the body • Includes hair, epithelia, secretions of integumentary and digestive systems

4. Figure 22.10 Nonspecific Defenses (Part 1 - Physical Barriers) Figure 22.10

5. Nonspecific Defenses, Phagocytes • Remove cellular debris and respond to invasion by foreign pathogens • Monocyte-macrophage system - Fixed and free • Microphages – Neutrophils and eosinophils • Move by diapedesis • Exhibit chemotaxis

6. Figure 22.10 Nonspecific Defenses(Part 2 - Phagocytes) Figure 22.10

7. Nonspecific Defenses, Immunological surveillance • Constant monitoring of normal tissue by NK cells • NK cells • Recognize cell surface markers on foreign cells • Destroy cells with foreign antigens

8. NK cell activation • Recognition of unusual surface proteins • Rotation of the Golgi toward the target cell and production of perforins • Release of perforins by exocytosis • Interaction of perforins causing cell lysis

9. Figure 22.10 Nonspecific Defenses(Part 3 - Immunological Surveillance) Figure 22.10

10. Figure 22.11 How Natural Killer Cells Kill Cellular Targets Figure 22.11

11. Nonspecific Defenses, Interferons (cytokines) • Small proteins released by virally infected cells • Trigger the production of antiviral proteins • Three major types of interferons are: • Alpha– produced by leukocytes and attract/stimulate NK cells • Beta– secreted by fibroblasts causing slow inflammation • Gamma – secreted by T cells and NK cells stimulate macrophage activity

12. Figure 22.10 Nonspecific Defenses(Part 4 - Interferons) Figure 22.10

13. Nonspecific Defenses, Complement system • Cascade of ~11 plasma complement proteins (C) • Destroy target cell membranes • Stimulate inflammation • Attract phagocytes • Enhance phagocytosis

14. Complement proteins interact with on another via two pathways • Classical • Alternative

15. Figure 22.10 Nonspecific Defenses(Part 5 - Complement System) Figure 22.10

16. Figure 22.12 Complement Activation Figure 22.12

17. Nonspecific Defenses, Inflammation • Localized tissue response to injury producing • Swelling • Redness • Heat • Pain • Effects of inflammation include • Temporary repair of injury • Slowing the spread of pathogens • Mobilization of local, regional, and systemic defenses

18. Figure 22.10 Nonspecific Defenses(Part 6 - Inflammatory Response) Figure 22.10

19. Figure 22.13 Inflammation Figure 22.13

20. Nonspecific Defenses, Fever • Maintenance of a body temperature above 37.2oC (99oF) • Pyrogens reset the hypothalamic thermostat and raise body temperature • Pathogens, toxins, antigen-antibody complexes can act as pyrogens

21. Figure 22.10 Nonspecific Defenses(Part 7 - Fever) Figure 22.10

22. SECTION 22-4Specific Defenses

23. Forms of immunity • Innate immunity • Genetically determined • Present at birth • Acquired immunity • Not present at birth • Achieved by exposure to antigen • Active immunity • Passive immunity

24. Figure 22.14 Types of Immunity Figure 22.14

25. Properties of immunity • Specificity – activated by and responds to a specific antigen • Versatility – is ready to confront any antigen at any time • Memory – “remembers” any antigen it has encountered • Tolerance – responds to foreign substances but ignores normal tissues

26. The immune system response • Antigen triggers an immune response • Activates T cells and B cells • T cells are activated after phagocytes exposed to antigen • T cells attack the antigen and stimulate B cells • Activated B cells mature and produce antibody • Antibody attacks antigen

27. Figure 22.15 An Overview of the Immune Response Figure 22.15

28. SECTION 22-5T cells and Cell-mediated Immunity

29. Major types of T cells • Cytotoxic T cells (TC) – attack foreign cells • Helper T cells (TH) – activate other T cells and B cells • Suppressor T cells (TS) – inhibit the activation of T and B cells

30. Antigen presentation • Antigen-glycoprotein combination appears on a cell membrane • Called MHC proteins (Major Histocompatibility Complex) • Coded for by genes of the MHC • T-cells sensitive to the antigen are activated upon contact

31. MHC classes • Class I – found on all nucleated cells • Class II – found on antigen presenting cells and lymphocytes

32. Lymphocytes respond to antigens bound to either class I or class II MHC proteins • Antigen recognition • T cell membranes contain CD markers • CD3 markers present on all T cells • CD8 markers on cytotoxic and suppressor T cells • CD4 markers on helper T cells

33. Figure 22.16 Antigens and MHC Proteins Figure 22.16

34. Figure 22.16 Antigens and MHC Proteins Figure 22.16a

35. Figure 22.16 Antigens and MHC Proteins Figure 22.16b

36. Activation of CD8 cells • Responds quickly giving rise to other T cells • Cytotoxic T cells – seek out and destroy abnormal cells • lymphotoxin • Memory TC cells – function during a second exposure to antigen • Suppressor T cells – suppress the immune response

37. Figure 22.17 Antigen Recognition and the Activation of Cytotoxic T Cells Figure 22.17

38. Figure 22.17 Antigen Recognition and the Activation of Cytotoxic T Cells PLAY Animation: Cytotoxic T Cell Activation Figure 22.17

39. Activation of CD4 T cells by antigens presented on class II MHC proteins • Produces helper T cells and memory T cells • Activated helper T cells • Secrete lymphokines that coordinate specific and nonspecific defenses • Enhance nonspecific defenses • Stimulate the activity of NK cells • Promote activation of B cells

40. Figure 22.18 Antigen Recognition and Activation of Helper T cells PLAY Animation: Antigen Recognition and Helper T Cell Activation Figure 22.18

41. Figure 22.19 A Summary of the Pathways of T Cell Activation Figure 22.19

42. Chapter 22, part 4 The Lymphatic System and Immunity

43. SECTION 22-6B Cells and Antibody-mediated Immunity

44. B cell sensitization of activation • Sensitization – the binding of antigens to the B cell membrane antibodies • Antigens then displayed on B cell Class II MHC • TH cells activated by same antigen stimulate B cell • Active B cell differentiates into Memory B Cell or Plasma cell • Plasma cells synthesize and release antibody

45. Figure 22.20 The Sensitization and Activation of B Cells PLAY Animation: B Cells and Antibody Production Figure 22.20

46. Antibodies structure • Antibodies are Y-shaped proteins consisting of: • Two parallel polypeptide chains • Heavy chains and light chains • Constant region and variable region • Antigen binding site

47. Figure 22.21 Antibody Structure Figure 22.21

48. Figure 22.21 Antibody Structure Figure 22.21a

49. Figure 22.21 Antibody Structure Figure 22.21b-d

50. Actions of antibodies include: • Neutralization • Agglutination and precipitation • Activation of complement • Attraction of phagocytes • Opsinization • Stimulation of inflammation • Prevention of adhesion