The Human Immune System

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The Human Immune System
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What is the immune system?

• The bodys defense against disease-causing
  organisms, viruses, malfunctioning cells, and
  foreign particles

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The First Line of DefenseSkin

• The dead, outer layer of skin, known as the
  epidermis, forms a shield against invaders and
  secretes chemicals that kill potential invaders

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The First Line of DefenseMucus and Cilia

• As you breathe in, foreign particles and bacteria
  bump into mucus throughout your respiratory
  system and become stuck
• Hair-like structures called cilia sweep this
  mucus into the throat for coughing or swallowing

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The First Line of DefenseSaliva
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The First Line of DefenseStomach Acid

• Swallowed bacteria are broken down by incredibly
  strong acids in the stomach that break down your
  food
• The stomach must produce a coating of special
  mucus or this acid would eat through the stomach!

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The Second Line of DefenseThe Inflammatory
Response

• Injured body cells release chemicals called
  histamines, which begin inflammatory response
• Capillaries dilate
• Pain receptors activate
• WBCs flock to infected area like sharks to blood

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The Second Line of DefenseWhite Blood Cells

• If invaders actually get within the body, then
  your white blood cells (WBCs) begin their attack
• WBCs normally circulate throughout the blood, but
  will enter the bodys tissues if invaders are
  detected

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White Blood Cells Phagocytes

• These white blood cells are responsible for
  eating foreign particles by engulfing them

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The Third Line of DefenseAntibodies

• Most infections never make it past the first and
  second levels of defense
• Those that do trigger the production and release
  of antibodies
• Proteins that latch onto, damage, clump, and slow
  foreign particles
• Each antibody binds only to one specific binding
  site, known as an antigen

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Lymphocytes (white blood cells)

• T-Cells identify pathogens by its markers or
  antigens
• B-cells produce antibodies or proteins that
  destroy the pathogen

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What is immunity?

• Resistance to a disease causing organism, virus,
  or harmful substance
• Two types
• Active Immunity
• Passive Immunity

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Active Immunity

• You produce the antibodies
• Your body has been exposed to the antigen in the
  past either through
• Exposure to the actual disease causing antigen
  (chickenpox, for example)
• Planned exposure to a form of the antigen that
  has been killed or weakened vaccine

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Vaccine

• Antigens are deliberately introduced into the
  immune system to produce immunity so body will
  have antibodies ready to destroy pathogen if you
  get exposed later.
• Because the virus or bacteria has been killed or
  weakened, minimal symptoms occur
• Have eradicated or severely limited several
  diseases from the face of the Earth, such as
  polio and smallpox

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How long does active immunity last?

• It depends on the antigen
• Some disease-causing viruses and bacteria mutate
  into new forms that our body doesnt recognize.
  This requires annual vaccinations, like the
  influenza (flu) shot.
• Booster shot - reminds the immune system of the
  antigen so youre still protected.
• Others last for a lifetime, such as chicken pox

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Passive Immunity

• You dont produce the antibodies
• A mother will pass immunities on to her baby
  during pregnancy
• These antibodies will protect the baby for a
  short period of time following birth while its
  immune system develops.
• Other example-rabies antibodies when you are
  bitten but you must get treatment shots to cure it

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Bacterial diseases

• Bacteria are living cells and release toxins.
  Your body cant kill bacteria so most must be
  treated with antibiotics to kill them
• Some examples are strep throat, food poisoning,
  salmonella, etc.

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Viruses

• Viruses enter body cells, hijack their
  organelles, and turn the cell into a virus-making
  factory. The cell will eventually burst,
  releasing thousands of viruses to infect new
  cells.

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The Common Cold

• The common cold is caused by a virus.
• It takes hours before you start having symptoms
  you are infected with a cold virus.
• Your bodys immune response T cells start working
  to identify the pathogen and B cells make
  antibodies to immobilize it. This immobilization
  process can take a week and then you feel better.
  
• Viruses cant be killed with antibiotics since
  they are not living. You can take medicines like
  acetaminophen to relieve symptoms, but they dont
  shorten your cold.
• The cold virus mutates often, so you will never
  get the same cold again. There is no vaccine to
  prevent colds.

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Aquired Immune Deficiency Syndrome

• Caused by the Human Immunodeficiency Virus
• Discovered in 1983
• Specifically targets and kills T-cells
• Because normal body cells are unaffected, immune
  response is not launched

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AIDSThe Modern Plague

• The HIV virus doesnt kill you it cripples your
  immune system
• With your immune system shut down, common
  diseases that your immune system normally could
  defeat become life-threatening
• Can show no effects for several months all the
  way up to 10 years

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HIV/AIDSThe Silent Spread

• Transmitted by blood, and fluids from infected
  people through sexual contact, blood
  trans-fusions, contami-nated needles.
• As of 2014, an estimated 35 million people are
  living with HIV/AIDS. Sadly many dont know or
  arent careful, so the spread continues.
• So far there is no vaccine to prevent HIV/AIDS.