Lecture 15
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Lecture 15 Lecture 15 Presentation Transcript

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