The Immune System

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The Immune System

• Biology
• Chapter 41

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• Pathogen-disease causing agent (various types of
  bacteria, viruses, fungi, protists)
• Body uses both specific and nonspecific defense
  mechanisms to prevent infection and destroy
  pathogens

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Nonspecific defenses

• Do not target a specific pathogen
• Skin and mucous membranes (line digestive system,
  lungs, nasal passages)

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Nonspecific defenses

• 2. Inflammatory response-suppress infection and
  speed recovery. Injured cells release Histamine
  which increases blood flow to area bringing more
  white blood cells (WBCs). Also causes swelling
  and redness in the infected area

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Nonspecific defenses

• Temperature response/Fever
• many bacteria do not grow well in higher temps
  however, too high a fever can result in
  destruction of important enzymes

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Nonspecific defenses

• 4. Proteins
• Complement system- proteins that circulate in the
  blood and when they encounter a pathogen they
  form a structure that ruptures the cell membrane
  of the pathogen.
• Interferon- protein released by cells infected
  with a virus, causes nearby cells to produce an
  enzyme that prevents viruses from making proteins
  and RNA.

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5. WBCs- most important counterattacks carried
out by 3 kinds of WBCs

• - Neutrophils-most abundant type, engulf and
  destroy pathogens
• - Macrophages-ingest and kill pathogens,
  concentrated especially in spleen and lungs

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• - Natural killer cells-destroy an infected cell
  by puncturing the cell membrane causing water to
  rush into the cell and burst. One of the best
  defenses against cancer, can detect and kill
  cancer cells before a tumor develops

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Specific Immune Responses

• Cytotoxic T cells-attack and kill infected cells
• B cells- label invaders for later destruction by
  macrophages
• Helper T cells- activate both cytotoxic T cells
  and B cells

cytotoxic T-cell
tumour cell
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Two distinct processes work together in the
immune response

1. B cell response which is a passive, humoral
   defense that aids in the removal of pathogens
2. T cell response, an active, cell-mediated defense
   that involves the destruction of pathogens by
   cytotoxic T cells

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Interactions Between Responses
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• Antigen Proteins or other components on the cell
  surface of the pathogen. WBCs have receptor
  proteins that bind to specific antigens.
• Antibody Y-shaped molecule produced by plasma
  cells upon exposure to specific antigen

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Immune Responses

• Immune responses

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Disease Transmission

• Person-to person contact (contagious/communicable)
  
• Air
• Food
• Water
• Animal Bites

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Kochs Postulates 4 step procedure for
identifying specific pathogens

1. Pathogen must be found in an animal with the
   disease, not a healthy animal
2. Pathogen is isolated and cultured
3. Pathogen is injected into healthy animal animal
   must develop the disease
4. Pathogen taken from second infected animal is
   cultured and it must be the same as the original
   pathogen

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Resistance to a disease is called immunity

• Vaccination is a medical procedure used to
  produce immunity.
• Edward Jenner developed a vaccine against
  smallpox.
• A small amount of dead or modified pathogen is
  injected into the body to produce an immune
  response without symptoms of the infection.
• Your body develops antibodies and memory cells
  against the pathogen (measles, polio, tetanus,
  diphtheria, etc).

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• Some pathogens have the ability to mutate over
  time. The viruses produce new antigens that your
  body does not recognize (antigen shifting). That
  is why you can get the flu, even if you have had
  a vaccination or already had it before.

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Disorders of the Immune System

• Autoimmune disease-body attacks its own cells
  (multiple sclerosis, rheumatoid arthritis,
  Graves disease, Type I Diabetes).
• AIDS is caused by HIV (human immunodeficiency
  virus). HIV invades helper T cells causing them
  to produce more virus and then die.
• HIV is transmitted through HIV-infected WBCs in
  body fluids and can be exchanged through sexual
  contact and/or sharing of needles

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3. Allergic Reactions

• An allergy is the bodys overreaction to a
  normally harmless antigen. Most allergic
  reactions cause cells to produce histamines,
  which cause swelling, redness, increased mucus
  production, runny nose, itchy eyes and congestion
• Most allergy medicines contain antihistamines,
  which prevent the action of the histamine.
• Severe allergic reactions, like asthma and bee
  stings, can be life threatening.