Lecture 15


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Lecture 15

  1. 1. Cellular Immunity<br />T lymphocyte respond to antigen when they bond to specific antigen called MHC proteins (major histocompatibility complex proteins) on the surface of the antigen presenting cells<br />T cells do not recognize free antigen but do recognize antigens combined with an MHC protein<br />MHC: Cell surface molecule that present antigen to T Cell <br />
  2. 2. <ul><li>The three major type of antigen presenting cells1. Macrophages2. B Lymphocyte3. Dendritic cells</li></li></ul><li>Release of activated T Cell from lymphoid tissue<br />Once exposed to antigen, T lymphocyte proliferate and release large number of activated, specifically reacting T cell <br />Whole activated T cells are formed and release into the lymph and circulated throughout the body<br />T lymphocyte memory cells are formed same way as that B memory cells<br />
  3. 3. CELL MEDIATED IMMUNITY<br />ANTIGENS<br />SPECIFIC DEFENSES<br />(Immune response)<br />APC’s phagocytize Ag & activate T cells<br />bacteria<br />viruses<br />Activated T cells clone & differentiate into:<br /><ul><li> Cytotoxic T cells
  4. 4. Helper T cells
  5. 5. Memory T cells</li></ul>Direct physical &<br /> chemical attack<br />Antigens<br />bacteria<br />viruses<br />
  6. 6. Cellular Immunity<br />Lymphocyte can be divided into two major classes based on cell surface proteins called CD proteins<br />One class of lymphocyte has CD4 and the other CD8<br />About one third of all T cells are CD8 and the other two third have CD4<br />
  7. 7. Activated CD8 cells become cytotoxic T cells<br />Activated CD4 become Helper T cells<br />CD8 bind to the class I MHC proteins<br />CD4 bind to class II MHC proteins<br />
  8. 8.
  9. 9. T Cells Only Recognize Antigen Associated with MHC Molecules on Cell Surfaces<br />
  10. 10. Once a T cell is activated by the presentation of the combined MHC/Antigen, it will clone differentiate into:<br />Activated CD8 cells become cytotoxic T cells – seek out the specific pathogen/infected cell that contains the targeted Antigen and destroys it by secreting various chemicals<br />Activated CD4 becomes helper T cells – necessary for coordination of both specific & non-specific defenses, as well as for stimulating both cell-mediated & antibody-mediated immunity.<br />
  11. 11. Helper T cell <br />The most numerous of T cells<br />Help regulate immune system by forming protein called lymphokines, that act on other cells of the immune system<br />Some of lymphokines are:<br />Interleukin-2<br />Interleukin-3 <br />Interleukin-4 <br />Interleukin-5 <br />Interleukin-6 <br />
  12. 12. T-Helper Cell function<br />Forming lymphokines<br />Immune system is paralyzed in the absence of lymphokines<br />Stimulation of growth and proliferation of cytotoxic T cells and suppressor T cells<br />Interleukin-2 has strong effect in causing growth and proliferation of both cytotoxic and suppressor T cells <br />
  13. 13. Stimulation of B cells growth and differentiation<br />Have direct effect to cause B- cell growth, proliferation, formation of plasma cells and secretion of antibodies<br />Activate macrophage system<br />They slow / stop the migration of the macrophages after they have attracted to the inflamed tissue<br />Stimulate effect on the helper cells<br />Interleukin-2 have direct effect in stimulating activation of helper T cells themselves<br />T-Helper Cell function<br />
  14. 14. Humoral Response to T Dependent Antigens<br />
  15. 15. Central Role of Helper T Cells<br />
  16. 16. Antibody Mediated (Humoral) Immunity<br />
  17. 17. Review of Immune Response<br />
  18. 18. Overview of the Immune Response<br />
  19. 19. Cytotoxic T Cells<br />Also called Killer cells<br />Capable of killing microorganism and even some of the body’s own cells<br />Cytotoxic T cell secret whole forming proteins called perforins that punch holes in the membrane of attacked cell<br />Cytotoxic T cell releases cytotoxic substance into the attacked cell causing lysis of infected cell<br />
  20. 20. Cytotoxic T cell recognize and destroy cancer cells<br />Recognize and destroy transplanted tissue<br />Undergo apoptosis when stimulating antigen is gone<br />Apoptosis<br />Programmed cell death, eliminate cells that are unneeded, infected or cancerous<br />Cytotoxic T Cells<br />
  21. 21. Cytotoxic T Cells Lyse Infected Cells<br />
  22. 22. Suppressor T cells<br />They are capable of suppressing the function of both cytotoxic and helper T cell<br />They serve functions of preventing the cytotoxic cells from causing excessive immune reactions that may damage the body own tissues, this called immune tolerance<br />Immune Tolerance<br />The condition of not mounting an immune response against the antigens that normally found within one’s own body. Lack of self tolerance underlies autoimmune diseases<br />