The Body's Defenses

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DesLee26
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216884
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The Body's Defenses
Updated:
2013-05-03 08:36:03
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BIO 220
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FINAL
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  1. Body's Defenses
    - Nonspecific defense mechanisms
    • First line of defense:
    •   A)  Skin
    •   B)  Mucus membranes
    •   C)  Secretions from both
    •   2)  Second line of defense:
    •   A)  Phagocytic white blood cells
    •   B)  Antimicrobial proteins
    •   C)  Inflammatory response
  2. Specific defense mechanisms
    • Third line of defense (Immune System):
    •   A)   Lymphocytes
    •   B)  Antibodies
  3. First Line of Defense (Skin and Mucus Membranes)
    • Skin is barrier that cannot normally be penetrated by bacteria or viruses.
    • -  However, cuts or abrasions could allow entry.
    • -  Provide physical barriers but also produce secretions.  (Examples: oil,   sweat).
  4. Skin and mucus membranes: secretions
    • Secretions have lower pH (more acidic)
    • -  Secretions may contain antimicrobial proteins.  (Examplelysozyme).
    •   Lysozyme:
    •   -  In tears and upper respiratory system.
    •   -  Attacks cell walls of bacteria
  5. Mucus
    Mucus  (thick, viscous secretion), produced by mucus membranes, can   trap microbes and particles. Example:  Upper respiratory system
  6. Second Line of Defense
    Cells
    • phagocytes
    • neutrophils
    • monocytes
    • eosinophils
  7. Phagocytes
    neutrophils
    • Phagocytes:
    •   -  Provide main internal mechanism of nonspecific defense.
    •   -  Main phagocytic cells = Neutrophils
    • Neutrophils:
    •   -  60-70% of all white blood cells
    •   -  attracted by chemical signals (Chemotaxis)
  8. Monocytes
    Eosinophils
    • Monocytes
    •   -  5% of white blood cells
    •   -  even more effective than Neutrophils
    •   -  become Macrophages ("big eaters")
    • Eosinophils:
    •   -  1.5% of white cells
    •   -  limited pagocytic activity
  9. Antimicrobial proteins
    • Complement:
    •   -  A group of > 20 proteins that act in cascade of activation   steps to lyse invading microbes.
    •   Interferons:
    •   -  Produced by virus-infected cells.
    •   -  Helps other cells resist infection.
  10. Inflammatory Response
    • Localized Inflammation:
    •   -  Inflammation = "setting on fire"
    •   -  Tissue damage triggers vasodilation in small vessels increasing blood   supply to damaged area.
    •   -  Example:  Histamine release from basophils and mast cells.
    •   -  Example: Prostaglandin release by damaged tissue.
    •   -  Vasodilation also delivers clotting elements.
    •   -  Perhaps the most important aspect of vasodilation is phagocyte migration
  11. Systemic inflammation
    • Release of large numbers of neutrophils from bone marrow.
    •   -  Fever caused by pyrogens.
  12. Third Line of Defense: Basic features
    • Specificity:
    •   -  Recognize antigens
    •   -  Produce antibodies
    •   2)  Diversity:
    •   -  Immune system can respond to millions of kinds of invaders.
    •   -  Stems from huge variety of lymphocytes.
  13. Third Line of Defense: Basic features pt. 2
    •  Self/Non-Self Recognition:
    •   -  Ability to distinguish body's own molecules.
    •   -  Malfunctions can lead to autoimmune disorders.
    •   4)  Memory:
    •   -  Acquired Immunity:  remembers antigen seen before responds faster second time.
    •   iActive Acquired Immunity:
    •   -  Depends on person's own immune system.
    •   Examples: Plague, Vaccinations
    •   ii)   Passive Acquired Immunity:
    •   -  Pregnant woman's body passes antibodies to fetus or newborn
  14. Immune System Has 2 subdivisions
    1st
    • Humoral Immunity:
    •   -  Results in antibody production by B lymphocytes.
    •   -  Defends against toxins, bacteria and viruses that are free in body fluids
  15. Cell-mediated immunity
    • Cell Mediated Immunity:
    •   -  Depends on direct action T lymphocytes (T cells).
    •   -  Defends against bacteria and viruses inside cells, and fungi,    protozoans and worms.
    •   -  Also attacks transplanted cells
  16. B and T Lymphocytes
    ...originate?
    ...identity?
    ...maturation?
    ...concentration?
    • All originate from stem cells in the bone marrow.
    •   -  Maturation site determines identity.
    •   -   Maturation in thymus gland = T lymphocytes.
    •   -  If remain in bone marrow = B lymphocytes.
    •   -  Mature B and T cells most concentrated in lymphatic   organs.
  17. B and T Lymphocytes
    ...receptors?
    ...antibodies?
    ...antigens?
    ...T cells?
    Specificity?
    ...binding?
    • Both B and T cells have antigenic receptors.
    •   -  B Cells have bound antibodies
    •   -  T Cells have receptors that recognize antigens.
    •   -  Specificity of immune system depends on B and T   cells being able to recognized specific antigens.
    •   -  When antigen binds to receptors on B and T cells,   these cells divide and give rise to effector cells.
  18. Five Subclasses of Immunoglobulins
    IgM and IgG
    •   IgMpentamer
    •   a)  first to arrive
    •   b)   indicates current infection
    •   2)  IgG =  monomer
    •   a)  Most abundant
    •   b)  crosses vessels easily
    •   c)  protects against toxins viruses and   bacteria
  19. Five Subclasses of Immunoglobulins
    IgA and IgD and IgE
    • 3)  IgAdimer
    •   a)  prevent viruses and bacteria from   attaching to epithelial surfaces
    •   b)  secretions (tears and colostrum)
    •   4)  IgD =  monomer
    •   a)   antigen receptor on surface of B cells
    •   5)  IgE =  monomer
    •   a)  on surface of basophils and mast cells
    •   b)  Allergic reactions
  20. Clonal Selection
    • Lymphocytes not plastic in their abilities to respond   to antigens.
    •   -  Rather, specificity pedetermined during development.
    •   -  If antigen binds to receptor on surface of   lymphocyte, cell divisions result in clones.
    •   -  Antigen-specific selection and cloning of   lymphocytes called clonal selection.
  21. Primary Immune Response
    • 5 -10 days
    •   -  T cells become Effector T cells and
    •   -  B cells become plasma cells
  22. secondary immune response
    • Faster: 3-5 days
    •   -  Response more prolonged
    •   -  Antibodies more effective at binding
  23. immunological memory
    • Ability to recognize antigen as previously encountered.
    • Memory cells produced along with short lived effector cells during
    •   primary immune response.
    •   A)  They do not exist until after primary immune response
    •   B)  Proliferate rapidly when re-exposed.
    • -  Confers immunity against diseases.
  24. Self-tolerance
    Lymphocytes with antigen receptors against self undergo   apoptosis (i.e.,"commit suicide“ before birth, a form of   programmed cell death).
  25. Self-tolerance: MHC
    • Major Histocompatibility complex (MHC):
    •   -  Classes I & II
    •   -  glycoproteins
    •   -  20 genes
    •   -  bichemical fingerprint (except identical twins)
  26. The Immune System works in close associatio with what?
    the lymphatic system
  27. Lymphatic system
    • Part of the circulatory system that collects fluids and proteins that have escaped from cells and returns them to the blood.
    • Phagocytic removal of cellular debris, and foreign matter (e.g., pathogens)
  28. Effector Cells
    • Effector cells directly defend body.
    •   From B cells:  Plasma Cells.
    •   From T cells:  Cytotoxic T Cells and Helper T Cells.
  29. Plasma cells
    secrete antibodies
  30. Cytotoxic T cells
    destroy infeected cells and cancer
  31. Helper T cells
    stimulate humoral adn cell-mediated immunity
  32. Antigen
    • usually protein or large polysaccharide (ex: on coat of bacterium)
    • Antigen is anything that can elicit an immune response or allergy that can be bound to (3D structure)
  33. Antibodies
    Antibodies - Only recognizes a localized region on antigen called antigenic determinant or epitope. Belong to class of proteins called Immunoglobulins.
  34. Structure of typical antibody
    • Heavy and light chains
    •   -   constant nd variable regions
    •   -   antigen-binding sites

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