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Defense Against Infectious Disease

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									Defense Against Infectious
        Disease
                 Review
• Disease- a disruption of homeostasis
• Infectious disease- caused by a pathogen
• Pathogen- disease producing organism
  such as bacteria, viruses, fungi, protozoan
• Innate immunity- non specific immunity
  – Skin and body secretions
  – Inflammation response
  – Phagocytes
     • Neutrophils
     • Monocytes
     • Macrophages (monocytes that have migrated into
       tissue
     • Eosinophils
  – Interferons- proteins that protect against
    viruses
• Acquired immunity- building up an immune
  response to a specific pathogen
• 2 types of responses: Both involve
  lymphocytes which circulate in blood and
  lymphatic system

  – 1. Production of antibodies, called antibody or
    humoral immunity.
  – 2. cellular, or cell mediated, immunity
• Both activated by antigens: foreign
  proteins
• Lymphatic system-
• Collects tissue fluid
  and filters it through
  the lymph nodes and
  thymus

• Lymph nodes- help
  filter out and
  concentrate
  pathogens. Dense
  with lymphocytes
Antibody, aka Humoral, Immunity
• Macrophages eat bacteria- antigens are
  presented on surface
• Helper T cells bind to macrophage and is
  “activated.” Signals B cell lymphocyte to
  react and change into a plasma cell- a
  plasma cell makes antibodies
• Antibodies mark bacteria or other cells for
  death

• Some B cells turn into Memory B cells
Cell-mediated immunity
• Macrophage eats bacteria, presents
  antigen on cell surface. Helper T cell binds
  to macrophage- is “activated”
• Helper T cell stimulates another type of
  lymphocyte- Killer T cell (aka cytotoxic T
  cell)
• Killer T cells multiply and attack the
  pathogen directly- inject enzyme Perforin
  into bacteria or cell, which kills them.
• Release cytokines- signals rest of immune
  system to activate
Passive vs Active immunity
• Passive: Mother’s milk, placental transfer
  or plasma infusion

• Active- patient injected with a vaccine. A
  weakened, dead or incomplete portion of
  pathogen is injected, stimulating an
  antibody response

• History: first safe vaccine 1798 by Edward
  Jenner
        HIV
• Human
  immunodeficiency
  virus
• Spread by direct
  contact of body
  fluids or blood
• Destroys Helper T
  cells
• It may take 8-10
  years for symptoms
  to appear
• What role do phagocytes play in defending
  the body against disease?

• What role does a lymph node play in
  defending your body against
  microorganisms?

• What is the difference between naturally
  acquired passive immunity and naturally
  acquired active immunity?

								
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