B cell immunity


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  • 2 x10 12 lymphocytes
  • Macromolecule Protein polysaccharide Most antigens have variety of antigenic determinants
  • 5 classes of antibodies (dependent on heavy chain) but binding sites may be different IgA, IgD, IgE, IgG, IgM IgM antibodies are secreted first IgG major immunoglobin in blood IgE mast cells (later) IgA secretions, saliva respiratory tract secretions IgD ????? All antibodies made by plasma cell have same binding site. Action depends on Fc
  • 10 binding sites Fc site activate complement system
  • Inactivated---specific inhibitory proteins if complement doesn’t bind quickly then ecome inactivated
  • IgG Fc binds to macrophages IgG goes from mother to fetus
  • IgE binds to mast cells release histamine and other agents which activae eosinophils. Histamine help increase premeability, activation of complement
  • MHC-I on all cells because cytotoxic cells must act against all cells MHC-II on B cells, macrophages, dendritic, and antigen presenting cells. Have CD4 and CD8 to help binding CD4 helper bind MHC-II CD8 cytotoxic cell bind MHC-I
  • CD8 on cytotoxic t cells CD4 on helper cells Cytotoxic cell recognize viral particles Infected cells are all nucleated cells antigen presenting cells are B-Cells and macrophages Cytotoxic cells focus attack on cells that make foreign antigens (menace) helper t-cells focue help on cells that take up foreign antigens (essential for immune response)
  • Weak bond between mhc complex and helper cell Strengthened by CD4 and MHC moolecule
  • MOVIE Pore forming protein
  • B cell immunity

    1. 1. IMMUNITY <ul><li>The capability to resist any organism or toxin that tend to damage the tissues and organs. </li></ul>
    2. 2. Immunity Innate = ability to resist damaging organisms and toxins skin, gastric acids, tissue neutrophils and macrophages, complement, NK cells Acquired = specific humoral ----> circulating antibodies(B-cell) cellular ----> activated cells(T-cell mediated)
    3. 4. Preprocessing of the T and B lymphocytes <ul><li>Thymus gland preprocesses the T lymphocytes </li></ul><ul><li>Liver and bone marrow preprocess the B lymphocytes </li></ul>
    4. 5. Lymphoid tissue
    5. 6. <ul><li>Millions of specific types of lymphocytes are stored in the lymphoid tissue. </li></ul><ul><li>All the different lymphocytes that are capable of forming one specificity of antibody or T cell are called a ‘clone of lymphocyte’. </li></ul>
    6. 7. Sequence Dormant lymphocytes Invasion of body by foreign antigen Phagocytosis by macrophages Presentation of antigen to lymphocytes
    7. 8. Antigen An antigen is a substance that can induce an immune response when introduced into an immunocompetent host and that can react with the antibody produced from that response.
    8. 9. Bone Marrow Pre-B Cell Pre-T Cell T-Cell T8-supressor T4-helper B-Cell Plasma Cell IgG IgA IgM IgD IgE Interactions between T- and B-Cells
    9. 10. <ul><li>Humoral immunity and Antibodies </li></ul>
    10. 11. Formation of antibodies by plasma cells <ul><li>Dormant B lymphocyte </li></ul><ul><li>Exposure to a specific antigen </li></ul><ul><li>Macrophage plays role in the activation process </li></ul><ul><li>Helper T cells also contribute in this activation process </li></ul>
    11. 12. <ul><li>These B lymphocytes enlarge to form lymphoblast. </li></ul><ul><li>Further diferentiate into plasmablast </li></ul><ul><li>The mature plasma cells(antibody factories) then produce gamma globulin antibodies . </li></ul>
    12. 13. Formation of Memory cells-difference between primary and secondary response
    13. 14. virgin cells first exposure to antigen second exposure to antigen activated cells memory cells Formation of Activated and Memory Cells Copyright © 2006 by Elsevier, Inc.
    14. 16. self-antigens death Central lymphoid organ Peripheral lymphoid organ stimulation self-antigens death inactivation Loss of Antigens to Self
    15. 17. Antibodies antigen binding site hinge region light chain heavy chain Fab fragment Fc fragment IgA, IgD, IgE, IgG, IgM
    16. 18. IgM Antibody
    17. 19. Antibodies <ul><li>IgG </li></ul><ul><ul><li>- 80% total, cross placenta, opsonization </li></ul></ul><ul><li>IgM </li></ul><ul><ul><li>- first produced, 10-15% total, activate complement </li></ul></ul><ul><li>IgD </li></ul><ul><ul><li>- not known, may help CD4 Th </li></ul></ul><ul><li>IgA </li></ul><ul><ul><li>- body fluid, tears, bronchiole secretions, saliva </li></ul></ul><ul><li>IgE </li></ul><ul><ul><li>- allergic reactions, histamine release </li></ul></ul>
    18. 20. Mechanism of action of antibodies Direct Action Complement System
    19. 21. Direct action of antibodies on invading agents <ul><li>AGGLUTINATION </li></ul><ul><li>PRECIPITATION </li></ul><ul><li>NEUTRALIZATION </li></ul><ul><li>LYSIS </li></ul>
    20. 22. Complement System Series of ~ 20 proteins Activated by microorganisms Will coat the microorganisms Present normally among plasma proteins The enzyme precursors can be activated by the so called ‘ classical pathway ’ s
    21. 24. complement bacteria phagocyte bacteria 2 . chemotaxis 1 . lysis 3 . opsonization Functions of Complement Activation Copyright © 2006 by Elsevier, Inc.
    22. 25. Antibody-Activated Phagocytosis Fc receptor bacterium opsonization
    23. 26. IgE and Histamine Release IgE receptor histamine vesicles binding of IgE to Fc receptor antigen antigen release of histamine binding of antigen
    24. 27. Thank You
    25. 28. T-cells Act over a short range Interact with another cell in body Can kill or signal other cell Only recognize antigen when presented on surface of target cell
    26. 29. T-cells Cytotoxic Cells kill infected cells Helper Cells (two types) activate macrophages and B-cells Suppressor Cells regulate activity
    27. 30. TH 1 TH 2 TC LGL B Antibody Production Virally infected cell and some tumor cells Antigen presentation Antigen presentation activation activation cytotoxicity macrophage T-Cell Function
    28. 31. Mhc-molecules MHC-I present foreign peptides to cytotoxic cells MHC-II present foreign peptides to helper cells
    29. 32. CYTOTOXIC T-CELLS HELPER T-CELLS Tc Th Class I MHC Class II MHC foreign protein infected target cell antigen- presenting cell Mhc-molecules
    30. 33. Helper T-cells Helper T-Cells recognize foreign antigen bound to MHC-II proteins on surface of antigen-presenting cells Helper T-Cells stimulate macrophages and B-cells Two signals are required for activation of Helper T-Cells
    31. 34. Activation of Helper T-cells Th antigen- presenting cell signal 1 signal 2 activation signal 2 is chemical (interleukin-1) or membrane bound molecule CD4 antigen
    32. 35. Activation of Helper T-cells Th antigen- presenting cell signal 1 signal 2 Th Il-2 receptor Il-2 Th Th proliferation CD4
    33. 36. Cytotoxic T-cells Cytotoxic T-Cells recognize viral protein fragments on surface of infected cells. Cytotoxic T-Cells induce infected cells to kill themselves Bind to infected cells Induce cell death Punch holes in cell membrane
    34. 37. Cytotoxic T-cells Class I MHC Tc infected target cell CD8 Perforin discharge
    35. 38. Natural Killer <ul><li>destroy virus-infected cells </li></ul><ul><li>do not express antigen specific receptors </li></ul><ul><li>cells with low levels of MHC I </li></ul><ul><li>induce cells to undergo apoptosis </li></ul>
    36. 39. TC TCR CD8 MHC Class I Inhibitory receptor NK Target No MHC Class I NK receptor