The Immune System

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The Immune System

• Defender of the
• Free World

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Organs of Immune System

• Bone marrowproduces white blood cells
• Thymusone place that white blood cells mature
  and specialize (the other is the bone marrow)
• Lymph nodesfilter pathogens from lymph and
  expose them to white blood cells
• Tonsils
• Adenoids
• Spleenfilters pathogens from blood and exposes
  them to white blood cells

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Nonspecific vs Specific Defenses

• React to any pathogen

• Only react to a specific pathogen

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Nonspecific Defenses

• Skin
• Physical barrier
• Produces sweat, oil, wax (all contain toxins
  poisonous to many bacteria)
• Some bacteria on skin is a good thing!

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Nonspecific Defenses

• Mucous membranesepithelial tissue lining body
  entrances
• Produce mucus (traps pathogens)
• Cilia sweep mucus into stomach (acid kills
  pathogens)

Cilia 5,325X
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Inflammatory Response

• Nonspecific response when any pathogen penetrates
  the skin or mucous membrane
• Damaged cells release histamine (increases blood
  flow to area and permeability of surrounding
  capillaries)
• Causes redness, swelling, warmth, and pain

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What is pus?

• Contains dead pathogens and white blood cells

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WBCs involved in inflammatory response

• Phagocyte engulfs pathogens
• Neutrophil
• 50-70 of white blood cells
• Can squeeze between the cells in the wall of a
  capillary
• Macrophage
• Consumes and destroys pathogens
• Rids body of worn-out cells

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WBCs involved in inflammatory response

• Natural Killer -cells attack cells infected by
  pathogens
• Punctures cell membrane ? water rushes in ? cell
  bursts

2 killer T-cells attacking a cancer cell SEM
14,900X
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Other Nonspecific Defenses

• Interferon
• Protein that inhibits virus reproduction in
  surrounding cells
• Produced by cells infected by virus
• Fever
• Stimulates bodys defense mechanisms
• Suppresses growth of some bacteria
• Promotes action of white blood cells
• Why can a fever sometimes be dangerous?

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Lymphocytes (white blood cells)

• B cells
• Mature in bone marrow
• Produce antibodies

• T cells
• Mature in thymus
• Helper T cells
• Killer T cells
• Suppressor T cells

Macrophage using cytoplasmic extensions to
capture bacteria (purple) SEM 17,400X
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Immune Response

• Lymphocytes recognize antigens (pathogens, parts
  of pathogens, bacterial toxins, insect venom,
  pollen, etc.)
• Receptor proteins on surface of lymphocyte
  recognize and bind to antigens that match their
  particular shape
• You have millions of different kinds of
  lymphocytes all with different shaped receptors!

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Summary

• Macrophage Helper T cell (director)
• Cytotoxic T Suppressor T B
  cells
• destroy infected shut down immune
  make
• cells response
  antibodies

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Memory Cells

• Some B or T cells remaining after immune response
  shut down
• Recognize pathogen and divide rapidly
• Eliminate pathogen before it can produce disease

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B Cell Memory
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Immune Response

• Primary
• The first time the body encounters an antigen
• Secondary
• Response of memory cells to subsequent infection
  by same pathogen
• FASTER and MORE POWERFUL

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Immunity Vaccination

• Vaccines contain pathogens that can no longer
  cause disease
• Contain antigens that stimulate immune response
• Memory cells produced

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Allergies

• The inappropriate reaction to a harmless
  substance
• Many symptoms caused by release of histamine by
  cell exposed to antigen
• anithistamines

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Autoimmune Diseases

• Immune system attacks own cells
• Multiple Sclherosis
• T cells attack and slowly destroy the insulating
  material covering nerves

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Additional Topics

• AIDS/HIV
• Tonsillectomies-good or bad?
• How does a vaccine work?
• How did Edward Jenner discover vaccination?
• Flu epidemic of 1918-1919
• Use of antihistamines

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Additional Topics (cond)

• Effect of Europeans on native populations when
  colonizing the Americas
• How does your body make so many different kinds
  of antibodies?
• Eradication of smallpoxgood or bad?
• Allergies
• Autoimmune disorders