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Adaptive immunity
- 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. Adaptive Immunity (Specific immunity) • Specificity • Memory • Ability to distinguish b/w self vs non-self • T and B cell
- 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.
- 7. CHECKPOINT • 1. What are the two main types of lymphocytes? • 2. What is an antigen? Name some examples.
- 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. 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. 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. •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. Macrophages
- 13. Antigen-Presenting Cells – B cells – Dendritic cells – macrophages
- 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. The central role of Helper T Cells (Boss) •Chapter 21, Immune System •15 •Figure 21.17a
- 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. 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. •Cytotoxic T cell •1 •Accessory protein •Class I MHC molecule •Infected cell •Antigen receptor •Antigen fragment
- 19. •Cytotoxic T cell •1 •2 •Accessory protein •Class I MHC molecule •Infected cell •Antigen receptor •Antigen fragment •Perforin •Pore •Gran- zymes
- 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. Figure 23.11 (1 of 2) CMI
- 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. 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
- 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. •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. 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. 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
- 30. Antibody Molecule •antigen binding sites •antigen •light chains •heavy chains
- 32. •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)
- 33. First and second exposures to a pathogen
- 34. Role of the antibodies
- 35. •The classical compliment pathway, resulting in lysis of a target cell
- 36. 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
- 39. Immune system Disorders • Allergies • Allergies are exaggerated (hypersensitive) responses to antigens called allergens • Allergens…. antigens •© 2011 Pearson Education, Inc.
Editor's Notes
- Figure 43.17 The killing action of cytotoxic T cells on an infected host cell.
- Figure 43.17 The killing action of cytotoxic T cells on an infected host cell.
- Figure 43.17 The killing action of cytotoxic T cells on an infected host cell.
- Figure 43.18 Activation of a B cell in the humoral immune response.
- Figure 43.18 Activation of a B cell in the humoral immune response.
- Figure 43.18 Activation of a B cell in the humoral immune response.
- I. DEFINITION Immunoglobulins (Ig) Glycoprotein molecules that are produced by plasma cells in response to an immunogen and which function as antibodies. The immunoglobulins derive their name from the finding that they migrate with globular proteins when antibody-containing serum is placed in an electrical field (Figure 1). II. GENERAL FUNCTIONS OF IMMUNOGLOBULINS A. Antigen binding Immunoglobulins bind specifically to one or a few closely related antigens. Each immunoglobulin actually binds to a specific antigenic determinant. Antigen binding by antibodies is the primary function of antibodies and can result in protection of the host. The valency of antibody refers to the number of antigenic determinants that an individual antibody molecule can bind. The valency of all antibodies is at least two and in some instances more. B. Effector Functions Frequently the binding of an antibody to an antigen has no direct biological effect. Rather, the significant biological effects are a consequence of secondary "effector functions" of antibodies. The immunoglobulins mediate a variety of these effector functions. Usually the ability to carry out a particular effector function requires that the antibody bind to its antigen. Not every immunoglobulin will mediate all effector functions. Such effector functions include: 1. Fixation of complement - This results in lysis of cells and release of biologically active molecules (see chapter two) 2. Binding to various cell types - Phagocytic cells, lymphocytes, platelets, mast cells, and basophils have receptors that bind immunoglobulins. This binding can activate the cells to perform some function. Some immunoglobulins also bind to receptors on placental trophoblasts, which results in transfer of the immunoglobulin across the placenta. As a result, the transferred maternal antibodies provide immunity to the fetus and newborn Immunoglobulin classes IgM First response to antigen IgG Most common form IgA Secreted form IgD B cell activation IgE Histamine reactions and allergies