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Adaptive immunity

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Adaptive immunity

  1. 1. THE IMMUNE SYSTEM
  2. 2. •Defense Mechanisms
  3. 3. Adaptive Immunity • Immunity that an organism develops during lifetime • Develops after exposure to antigens • Invovles the activity of lymphocytes • Includes 3rd line of defense
  4. 4. Adaptive Immunity (Specific immunity) • Specificity • Memory • Ability to distinguish b/w self vs non-self • T and B cell
  5. 5. Types of Adaptive Immunity 1. Antibody-Mediated Immunity (AMI) or Humoral Immunity – B lymphocytes 2. Cell-Mediated Immunity (CMI) or Cellular Immunity – T lymphocytes Note: B and T cells ……..blood, lymph, lymphoid tissues such as spleen, lymph nodes etc.
  6. 6. •Lymphocyte Formation
  7. 7. CHECKPOINT • 1. What are the two main types of lymphocytes? • 2. What is an antigen? Name some examples.
  8. 8. Cell-Mediated Immune Response • T cells • Immune resoponse to infected cells ( viruses, bacteria and parasites (Pathogens) within cells) • Defense against cancer and transplant cells •Chapter 21, Immune System •8
  9. 9. T-Lymphocytes • Helper T cells – secrete CYTOKINES  help B cells Tc cells to divide • Cytotoxic T cells (killer T cells)  Kill infected body cells • Memory T cells  remain in body
  10. 10. How do T cells know a cell is infected? • Infected cells digest some pathogens and MHC proteins carry pieces to cell surface • Antigen Presenting Cell (APC) • Alerts Helper T cells •MHC proteins displaying foreign antigens infected cell •T cell with antigen receptors •TH cell
  11. 11. •Chapter 21, Immune System •11 • MHC proteins,mark a cell as self • The two classes of MHC proteins are: – Class I MHC proteins – found on virtually all body cells – Class II MHC proteins – found on certain cells in the immune response MHC Proteins
  12. 12. Macrophages
  13. 13. Antigen-Presenting Cells – B cells – Dendritic cells – macrophages
  14. 14. Helper T Cells (TH) • bind to other white blood cells that have previously encountered an antigen – stimulate proliferation of other T cells – Stimulate B cells that have already become bound to antigen • Without TH, there is no immune response •Chapter 21, Immune System •14
  15. 15. The central role of Helper T Cells (Boss) •Chapter 21, Immune System •15 •Figure 21.17a
  16. 16. Cytotoxic T Cell (Tc) • Destroys infected body cells – binds to target cell – secretes perforin protein • punctures cell membrane of infected cell – apoptosis •Chapter 21, Immune System •16
  17. 17. Cytotoxic T cells •Killer T cell binds to infected cell • Destroys infected body cells – binds to target cell – secretes perforin protein • punctures cell membrane of infected cell – apoptosis •infected cell •destroyed
  18. 18. •Cytotoxic T cell •1 •Accessory protein •Class I MHC molecule •Infected cell •Antigen receptor •Antigen fragment
  19. 19. •Cytotoxic T cell •1 •2 •Accessory protein •Class I MHC molecule •Infected cell •Antigen receptor •Antigen fragment •Perforin •Pore •Gran- zymes
  20. 20. The killing action of cytoxic T cells on an infected host cell. •Cytotoxic T cell •3•1 •2 •Accessory protein •Class I MHC molecule •Infected cell •Antigen receptor •Antigen fragment •Perforin •Pore •Gran- zymes •Released cytotoxic T cell •Dying infected cell
  21. 21. Figure 23.11 (1 of 2) CMI
  22. 22. • Human Immunodeficiency Virus – virus infects and destroys helper T cells • helper T cells don’t activate rest of immune system: killer T cells & B cells • AIDS: Acquired ImmunoDeficiency Syndrome – infections by opportunistic diseases – death usually from – “opportunistic” infections • pneumonia, cancers HIV & AIDS •HIV infected T cell
  23. 23. ANTIBODY-MEDIATED (HUMORAL) IMMUNITY • targets extracellular microorganisms (Bacteria and viruses circulating in the blood) • B-lymphocytes (B cells)………. Antibodies • Antibodies… extracellular fluids and surface of B cells
  24. 24. •Pathogen •1 •Antigen-presenting cell •Antigen fragment •Class II MHC molecule •Antigen receptor •Accessory protein •Helper T cell
  25. 25. •Pathogen •1 •2 •Antigen-presenting cell •Antigen fragment •Class II MHC molecule •Antigen receptor •Accessory protein •Helper T cell •B cell •Cytokines •Activated helper T cell ∀+
  26. 26. •Pathogen •3•1 •2 •Antigen-presenting cell •Antigen fragment •Class II MHC molecule •Antigen receptor •Accessory protein •Helper T cell •B cell •Cytokines •Activated helper T cell •Memory B cells •Plasma cells •Secreted antibodies ∀+
  27. 27. Antibody-mediated (humoral) immunity = AMI • 1- Macrophages phagocytize a pathogen and present an antigen to a matching helper-T cell • 2- At the same time, some pathogens contact B-cells matching the pathogen’s antigens • The helper-T cells multiply, secrete lymphokines which stimulate the B-cells to multiply and specialize into plasma cells • The plasma cells secretes antibodies
  28. 28. The Nature of Antibodies • Globular proteins called immunoglobulins • Basic antibody structure has 4 polypeptide chains – 2 identical light chains – 2 identical heavy chains • Regions of heavy and light chains – Variable – Constant
  29. 29. Antibody Molecule •antigen binding sites •antigen •light chains •heavy chains
  30. 30. •Immunoglobin ClassesImmunoglobin Classes • IgM • 1st response to antigen • Can’t cross placenta • IgG • Most common form • Crosses placenta (passive immunity to fetus) • IgA • Secreted from mucus membranes • In colostrum • IgD • B cell activation • Can’t cross placenta • IgE • Histamine reactions and allergies (mast cells, basophils)
  31. 31. First and second exposures to a pathogen
  32. 32. Role of the antibodies
  33. 33. •The classical compliment pathway, resulting in lysis of a target cell
  34. 34. Types of Immunity • Active Immunity Natural active immunity - acquired due to infection Artificial active immunity – vaccination • Passive Immunity Natural passive immunity • placenta to the fetus • Colostrum Artificial passive immunity • Injection of immune serum
  35. 35. Types of Acquired Immunity
  36. 36. Immune system Disorders • Allergies • Allergies are exaggerated (hypersensitive) responses to antigens called allergens • Allergens…. antigens •© 2011 Pearson Education, Inc.
  37. 37. •41 QUESTIONS PLEASE

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