Microbiology Chapter 21.txt

  1. Antigens
    Antigens are microbes or microbe parts that provoke an immune response
  2. Antibodies
    Proteins made against antigens
  3. The antigen that provokes the best immune response is a
    • Protein
    • Carbs provoke a little response and lipids a very poor response
  4. Haptens
    • Less than 10000 molecular weight, so no immune response
    • We don't build antibodies to haptens
    • Can attach to something else to provoke an immune response
  5. Antigenic determinants
    • Epitopes
    • Protein receptors on B and T cells recognize discrete regions of the antigen called epitopes
  6. Haptens
    • Non immunogenic molecules that don't stimulate the immune system by themselves, but when they are linked to proteins in the body, the larger combination may be recognized as nonself.
    • Specific immunologic tolerance
    • An example is penicillin
  7. Immunological memory
    The ability to remember past pathogen exposures
  8. Immunocompetent
    • Refers to lymphocytes capable of reacting with a specific epitope
    • B and T cells are waiting in the wings to respond to an antigen
  9. Clonal selection
    Exposure to an antigen only activates those naive B and T cells with receptors recognizing specific epitopes on the antigen.
  10. Autoantigens
    Body attacks self
  11. Immune deficiency
    The loss of the body's ability to respond to antigens and epitopes
  12. Regulatory T cells prevent
    Other T cells from attacking "self" cells
  13. Autoimmune diseases occur when
    Self-tolerance breaks down
  14. If nonimmunogenic molecules (haptens) are linked to proteins,
    • They may not be recognized as "self"
    • Thus they might provoke an immune response (allergies)
  15. Immunological memory
    • The ability to "remember" past pathogen exposures
    • The body fights off any subsequent infections
  16. The humoral immune response involves
    • Activation of B cells
    • Production of antibodies against the identified antigen
  17. T lymphocytes (T cells) provide resistance through
    Lysis of infected or abnormal cells
  18. If the microbes enter cells
    Antibodies are useless
  19. Then the cell mediated immune response (T cells) is activated to
    Eliminate "nonself" cells
  20. B lymphocytes (B cells)
    • Involved in producing antibodies against epitopes
    • Humoral immunity
  21. T lymphocytes (T cells)
    Cell mediated immunity
  22. Where are B cells and T cells found?
    In the lymph nodes and spleen
  23. When are B & T cells activated?
    When an antigen is detected
  24. B cells
    • React quickly when activated
    • Memory cells
    • Plasma cells
    • Each B cell can produce only one type of antibody
  25. Plasma cells
    • Produced from B cell clones
    • Synthesize and secrete antibodies against the invading pathogen
    • B cells that make antibodies
    • Makes about 2000/second
    • Live about 4 days
  26. Memory cells
    • Are long lived B and T cells capable of dividing on short notice to produce more effctor cells and additional memory cells in an immune response
    • Can live for decades
  27. Effector cells
    • Target the pathogen
    • B and T cells contain activated lymphocytes that will develop into effector cells and memory cells.
  28. Hematopoietic stem cells
    • Lymphocytes originate from these cells in the yolk sac, but end up in the bone marrow
    • Develop into myeloid and lymphoid progenitors
  29. Myeloid progenitors
    • Developed from Hematopoietic stem cells
    • Become red blood cells and most of the white blood cells
  30. Lymphoid progenitors
    Become lymphocytes of the immune system
  31. Antigen binding site
    • The variable domains in a light and heavy chain forma highly specific, three-dimensional structure
    • It is this region on the antibody that binds to the antigen with epitopes
  32. Antigen exposure activates
    Only T and B cells with receptors that recognize specific epitopes on that antigen
  33. B and T cell clones contain lymphocytes that develop into
    • Effector cells that which target pathogens
    • Memory cells are long-lived B and T cells
    • They are capable of division on short notice
  34. The immune system originates from
    • Groups of stem cells
    • Hematopoietic stem cells
  35. In the fetus, lymphocytes arise from
    Hematopoietic stem cells in the yolk sac and bone marrow
  36. T lymphocytes are formed in
    The thymus
  37. B cells are formed in
    The bone marrow
  38. Antibodies are of a class of proteins called
    • Immunoglobulins, (Ig)
    • Hooked together with a disulfide bond
  39. Antibodies comprise
    17 % of protein in serum
  40. Epitope recognition requires antibodies to have a special structure of
    • 2 identical heavy (H) chains
    • 2 identical light (L) chains
  41. The humoral immune response
    • Immunoglobulins
    • Results in the activation of B cells and the production of antibodies that recognize epitopes on the identified antigen in the blood or lymphatic fluids
    • The response is so specific that the body can generate antibodies to just about any antigen or epitope it encounters.
  42. Immunoglobulin constant region
    Determines the destination (body location) and functional class of the antibody
  43. Immunoglobulin variable region
    • Contains different amino acids for the many antibodies produced
    • Binds to antigen
    • Each variable region can bind to two antibodies
  44. Each immunoglobulin light and heavy chain has:
    • A constant region, which determines the location and functional class of the antibody
    • A variable region, which contains different amino acids for the many antibodies produced
  45. Immunoglobulin variability allows
    Formation of the specific antigen binding site
  46. The Fab fragment of an antibody combines with
    The Epitope
  47. The Fc fragment performs functions in

    • Able to be crystalized
    • It can combine with phagocytes, activate the complement system or attach to certain cells in allergic reactions
  48. How many know Immunoglobulin classes are there?
    There are five immunoglobulin classes
  49. IgM
    • Is the first (but short-lived) Ig to appear in circulation after B cell stimulation
    • Primary antibody response
    • Largest Ab in circulation
    • Doesn't cross the placenta
    • 5 chains
  50. IgG (gamma globulin)
    • Is the major circulating antibody
    • It provides immunity to the fetus and newborn. Crosses the placenta
    • 1st discovered. Classical
    • 80% of all Ig's in the blood
    • A little slow, takes 24-48 hours
    • Secondary Ab response
  51. Memory cells
    IgG memory cells provide long term resistance
  52. IgA
    • Provides resistance in the respiratory and gastrointestinal tracts
    • It is found in colostrum & tears
    • 2 chains hooked together J chain
  53. IgE
    Plays a role in allergic reactions
  54. IgD
    Don't know
  55. A primary antibody response occurs
    • The first time the body encounters a pathogen
    • B cells are activated and effector cells, the plasma cells, start producing and secreting antibody
  56. A secondary antibody response is
    • More powerful and longer lasting
    • It occurs with a subsequent infection by the same pathogen
    • Due to the presence of memory cells, a rapid response to antigen leads to the production of IgG principle antibody.
  57. Antibody diversity is a result of
    Gene arrangements
  58. Somatic recombination
    • A random mix and match of gene segments to form unique antibody genes
    • This accounts for the large number of unique antibodies encoded by immune system genes
    • The information encoded by these genes is expressed in the surface receptor proteins of B cells and in the antibodies later expressed by the stimulated clone of plasma cells.
  59. How many Immunoglobulin genes exist?
    • 300 Variable
    • 50 diversity
    • 4 joiner
    • 8 constant regions
  60. Viral inhibition
    Antibodies react with molecules at the viral surface and prevent the viral attachment to cells
  61. Membrane attack complex
    Forms pores in the bacterial cell membrane increasing cell membrane permeability and inducing the cell to undergo lysis through the unregulated flow of salts and water
  62. Major histocompatibility complex
    Proteins that define the uniqueness of the individual and play a role in the immune response
  63. Antigen presenting cells
    • MHC-II molecules fold to form a pocket in which small antigen (peptide fragments can bind)
    • APCs present antigen fragments to CD4 T cells which will bind them with their TCR/CD4 receptor complex
  64. MHC-1
    • Molecules that are found on all nucleated cells of the body
    • Fold so that they can bind a small antigen fragment from an infecting virus
  65. Interleukin 1
    A cytokine which binds with naive T cells and stimulates T-cell activation
  66. Helper T cells
    • T2: Help in the activation of humoral immunity
    • T1: Recognize and bind to infected APC displaying the appropriate MCH-1 peptide
  67. Perforin
    • Toxic proteins that insert into the membrane of the infected cell forming cylindrical pores in the membrane
    • This releases ions, fluids, and cell structures
  68. Granzymes
    Cytotoxic cells release granzymes that enter the target cell and trigger apoptosis.
  69. Toxin neutralization
    Antibodies called antitoxins combine with toxins and neutralize them and prevent toxin attachment to cells
  70. Opsonization
    Antibodies coat bacterial cells and prevent bacterial attachment to cells
  71. Aggluntination
    Antibodies combine with antigens on the cell surface and bind the cells together or restrict movement.
  72. Precipitation
    • Antibodies combine with dissolved antigens to form lattice like arrangement that precipitate out of solution.
    • Each Antibody attaches to two antigens.
    • Deals with something smaller than a cell
  73. Phagocytosis
    The Fc portion on antibodies encourages phagocytosis by forming a bridge between antigen and receptor sites on the phagocyte.
  74. Five types of antigen-antibody complexes
    • Antitoxins
    • Agglutination
    • Precipitation
    • Opsonization
    • The complement system
  75. Formation of antigen-antibody complexes result in the antigen
    • Death
    • Inactivation
    • Increased susceptibility
  76. Four Types of T Cells
    • Cytotoxic T cells
    • Delayed hypersensitivity T cells
    • Naive cells, (Helper T cells)
    • Suppressor T cells
  77. Cytotoxic T cells
    • Killer T cells
    • The marines
    • Cytotoxic T cells have T-cell receptors (TCRs) and CD8 coreceptor proteins
  78. Naive cells, (Helper T cells)
    • Stimulates B cells and cytotoxin cells
    • Makes other cells not lazy
    • Have TCRs and CD4 coreceptor proteins
    • Formerly known as helper T cells can help with both humoral and cell mediated immunity
    • HIV attaches to the CD4 receptor and infects the cell
  79. Suppressor T cells
    Keeps other T cells from getting too active so they don't attack self
  80. The Cell Mediated Immune Response
    • Cytotoxic T cells
    • Naive T cells
  81. Naive T Cells Mature into
    Effector T Cells
Card Set
Microbiology Chapter 21.txt
Microbiology Chapter 21