Immunology 49 See Chapter 21 for an overview

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Immunology 4/9See Chapter 21 for an overview

• The defense of pathogens using the immune system
  (natural defenses).

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The Establishment of Disease

• Respiratory Droplets
• Dust (aerosols)
• Contaminated food or water
• Direct contact with contaminated object
• Arthropod bites
• Contact with animals
• Injection with contaminated soil/object

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Types of Pathogens

• Bacterial
• Viral
• Parasites
• Fungi
• Prions

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What is Immunity?

• A complicated web of cells and chemical signals
  that work in concert to protect the body from
  pathogens and injury
• Cells are educated to distinguish between self
  and non-self

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Two Branches of Immunity

• Innate (Non-specific)
• Adaptive

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Innate Responses

• Physical/Chemical Barriers- skin, pH, mucous
  membranes, cilia, sweat glands, others
• Microbiogical- Direct competition of good
  microbes over bad microbes
• Cellular- Phagocytosis, Granulocytes and
  Inflammation

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Cells without Memory (innate)

• Macrophages-very important cell of the immune
  system. An antigen presenting cell (APC),
  phagocytic cell, and recruiting cell in the
  inflammatory response
• Neutrophils- phagocytic cell that is often the
  first line of defense. Short lived but
  effective.
• Dendritic Cells- Professional APC
• Mast Cells- tissue dwelling cell, often involved
  with allergies
• Eosinophils- responsible for killing parasites,
  often involved with allergies/asthma
• Basophils- similar to eosinophils
• Natural Killer Cell (NK)- direct cell killing
  and/or recruiting cell

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Inflammation (Innate Response)
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Signs of Inflammation

• Heat, Pain, Redness, Swelling (calor, dolor,
  rubor, tumor).
• Cells involved- Macrophages, Neutrophils
• Other substances involved- cytokines, complement

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Specific Resistance (Cells with Memory)

• Terminology
• Antigens- chemical substances capable of
  stimulating the immune response (mostly proteins)
• Antigenic determinant (epitope)- the small part
  of an antigen that the lymphocytes recognize in
  order to stimulate the specific response

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Cells with Memory

• B lymphocytes (B Cells)- differentiate into
  antibody secreting plasma cells
• T lymphocytes (T Cells)-
• CD4 (T Helper Cells)- help with the inflammatory
  response and/or help B Cells make antibodies
• CD8 (Cytotoxic T Cells)- directly kill virally
  infected cells

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Adaptive ResponseClonal Selection Theory

• Random unique receptors confer specificity
• Clones
• Some clones become memory cells
• Response gets better over time (more cells,
  faster response, better specificity)
• Cells capable of recognizing self molecules are
  destroyed.

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Cell-Mediated Immunity

• Macrophage (or other APC) processes and presents
  antigen on MHC class I. Brings antigen to
  closest lymph node
• CD8 (or Cytotoxic T Cell) recognizes antigen
  being displayed on MHC
• Clones
• Some become effector cells (kills virally
  infected cells)
• Some become memory cells for the next time

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Cell-Mediated ImmunityEffector Cells
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Antibody-Mediated Immunity(Humoral Immunity)

• B Cell recognizes (binds to) antigen within a
  lymph node.
• B Cell processes antigen and displays it on MHC
  class II
• Meanwhile, a macrophage activates a T Cell which
  clones itself
• T Cell activates B Cell by binding with the MHC
  displayed on B Cell surface
• T Cell activates B Cell
• Some B Cells become plasma cells and secrete
  antibodies while others become memory B Cells

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Humoral Immunity
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Structure of an Antibody
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Types of Antibodies
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Antibody Isotype Differences

• IgG- most abundant in blood/serum. Crosses the
  placenta. Found in extracellular fluids.
• IgM-first antibody produced, excellent at
  activating complement (proteins used in immune
  reactions)
• IgA-protects the mucosal surfaces, passed in
  breast milk
• IgE-specific for parasitic infections, often seen
  in allergic reactions
• IgD- receptor on B Cell surfaces

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Antibody Functions

• Neutralization- neutralizes toxins so they cant
  hurt cells
• Opsonization- allows for more efficient
  phagocytosis of organisms
• Agglutination- clumps non-soluble antigens
• Precipitation-forms lattices of antibody and
  soluble antigens
• Inhibition- keeps pathogens from binding to
  receptors and gaining access

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Opsonization
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Neutralization
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Inhibition
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Immunity Gone WrongHypersensitivity Reactions

• 4 Types of Hypersensitivity Reactions
• Type I- allergies
• Type II- Cytotoxic- antibodies to cell surface
  antigens (incompatible blood types or hemolytic
  disease of the newborn)
• Type III- Immune complex hypersensitivity-
  accumulation of immune complexes in blood tissues
  (Systemic lupus erythematosus-SLE) or Rheumatoid
  arthritis
• Type IV- Delayed or cellular hypersensitivity- T
  Cell mediated, takes 24-72 hours for effects.
  Poison ivy and other chemical/skin reactions

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Allergy Sensitization
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Allergy Elicitation