Defense Against Infectious Disease

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Defense Against Infectious Disease
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Review

• Disease- a disruption of homeostasis
• Infectious disease- caused by a pathogen
• Pathogen- disease producing organism such as
  bacteria, viruses, fungi, protozoan

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• 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

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• 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

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• 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

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• 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

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• 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

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• Passive vs Active immunity
• Passive Mothers 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

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• 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

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• 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?