Immune System

• Immune system - The body's defense against disease disease-causing organisms, malfunctioning cells, and foreign particles.
• Skin

  • The dead, outer layer of skin, known as the epidermis, forms a shield against invaders and secretes chemicals that kill potential invaders
  • You shed between 40 – 50 thousand skin cells every day!
• Mucus and Cilia

  • 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
• Saliva - Contains many chemicals that break down bacteria
• Stomach 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!
• White Blood Cells (WBCs)

  • 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 body's tissues if invaders are detected
• Phagocytes

  • White blood cells responsible for eating foreign particles by engulfing them
  • Once engulfed, the phagocyte breaks the foreign particles apart in organelles called lysosomes
• 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
• Interferon - Chemical released by virus-infected body cells that interferes with the ability of viruses to attack other body cells
• Cells

  • T-Cells, often called "natural killer" cells, recognize infected human cells and cancer cells
  • T-cells will attack these infected cells, quickly kill them, and then continue to search for more cells to kill
• Inflammatory Response

  • Injured body cells release chemicals called histamines, which begin inflammatory response
  • Capillaries dilate
  • Pyrogens released, reach hypothalamus, and temperature rises
  • Pain receptors activate
  • WBCs flock to infected area like sharks to blood
• Cell-mediated immune system - The efforts of the WBCs known as phagocytes and T-cells
• Antibody-mediated immunity - The other half of the immune system, controlled by antibodies
• Antibodies

  • Proteins that latch onto, damage, clump, and slow foreign particles
  • Each antibody binds only to one specific binding site, known as an antigen
• Antibody Production

  • WBCs gobble up invading particles and break them up
  • They show the particle pieces to T-cells, who identify the pieces and find specific B-cells to help
  • B-cells produce antibodies that are equipped to find that specific piece on a new particle and attach
• Immunity - Resistance to a disease-causing organism or harmful substance
• 2 Types of Immunity

  • Active Immunity
  • Passive Immunity
• Active Immunity - You produce the antibodies
• Active Immunity

  • Your body has been exposed to the antigen in the past either through:
  • Exposure to the actual disease causing antigen – You fought it, you won, you remember it
  • Planned exposure to a form of the antigen that has been killed or weakened – You detected it, eliminated it, and remember it
• Vaccine

  • Antigens are deliberately introduced into the immune system to produce immunity
  • Because the bacteria has been killed or weakened, minimal symptoms occur
• Vaccines have eradicated or severely limited several diseases from the face of the Earth, such as polio and smallpox
• Booster shot - Reminds the immune system of the antigen
• • In 1918, a particularly deadly strain of flu, called the Spanish Influenza, spread across the globe
  • It infected 20% of the human population and killed 5%, which came out to be about 100 million people
• • Although the Center for Disease Control (CDC) recommends certain vaccines, many individuals go without them
  • Those especially susceptible include travelers and students
  • Consider the vaccine for meningitis, which is recommended for all college students and infects 3,000 people in the U.S., killing 300 annually
• Passive Immunity - You don't produce the antibodies
• Placenta - A mother will pass immunities on to her baby during pregnancy through this organ
• Thymus - Endocrine gland responsible for protecting the baby with antibodies for a short period of time following birth while its immune system develops
• Passive immunity lasts until antibodies die
• The mother doesn't just pass on the WBCs that "remember" the antigens
• Allergies

  • Immune system mistakenly recognizes harmless foreign particles as serious threats
  • Launches immune response, which causes sneezing, runny nose, and watery eyes
  • Anti-histamines block effect of histamines and bring relief to allergy sufferers
• AIDS

  • The HIV virus doesn't 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
• Escherichia coli - is common and plentiful in all of our digestive tracts.
• Why are we all not sick?

  • These Escherichia coli bacteria are technically outside the body and aid in digesting material we cannot
  • Only if E. Coli is introduced in an unnatural manner can they break through the first line of defense and harm us.