Immunity

• Immunity

  Protection against foreign substances or pathogens from entering the body
• Types of immunity

  • Passive immunity
  • Active immunity
• Passive immunity


  Immunity where someone or something else has provided you with the defense against the infection
• Natural passive immunity


  • Transmission of antibodies from mother to baby via breast milk
• Artificial passive immunity


  When you are given a serum medicine, e.g. for tetanus
• Passive immunity


  • Short-term
  • Does not require actual exposure to the pathogen
• Active immunity

  Immunity developed through exposure to an infection or a vaccine
• Developing active immunity naturally

  1. Exposed to pathogen

  2. Develop antibodies

  3. Better and faster response next time exposed
• Developing active immunity artificially

  1. Injected with dead pathogen or part of pathogen

  2. Body remembers pathogen

  3. No illness when exposed
• Lines of defense in the immune system

  • Non-specific first line
  • Inflammation second line
  • Specific third line
• Non-specific first line of defense

  • Doesn't target specific pathogens
  • Protection on body surface
• Non-specific surface immunity

  • Eyes and antimicrobial tears
  • Respiratory tract and mucous lining
  • Skin and acidic sweat
• Inflammation response

  Swelling, fever, and antimicrobial proteins that attract white blood cells
• Inflammation response

  1. Histamine released

  2. Blood vessels swell and become more permeable

  3. White blood cells attracted to area
• Phagocytosis


  Process where phagocytes (large white blood cells) engulf and digest foreign particles
• Cells involved in third line of defense

  • Helper T cells
  • Killer T cells
  • B lymphocytes
• Helper T cells


  Start immune response and call for help from other cells
• Killer T cells

  Destroy infected host cells
• Antigens

  Proteins on cell surfaces that identify 'self' vs 'foreign'
• Viruses hide inside host cells, making them hard for the body to detect</b>
• Immune response to infected cells

  1. Killer T cells touch infected cell surface

  2. Killer T cells detect changed cell chemistry

  3. Killer T cells destroy infected cell

  4. Phagocytes clean up damaged particles and pathogens
• Antigen


  Proteins on the surface of every cell that identify it as belonging to the body
• Foreign invader antigens don't match body's antigens


  Body recognises it as foreign
• How T cells detect infected cells

  1. T cell touches infected cell

  2. T cell notices different antigen shape

  3. T cell knows infected cell is foreign
• How phagocytes detect foreign invaders

  1. Phagocytes have to touch outer area first

  2. Phagocytes can then tell if it's a foreign invader
• Suppressor T cells

  Stop the immune response when the body is recovering
• B lymphocytes


  • Can destroy both viruses and bacteria
  • Can remember infections and respond faster next time
• B cell activation

  1. B cells detect foreign antigens

  2. B cells send alert via cytokines

  3. B cells become plasma cells producing antibodies

  4. B cells become memory cells
• Antibodies

  Proteins that can burst bacterial cells, clump pathogens together, and neutralise toxins
• Memory cells maintain memory of pathogens' antigens
• Lines of defence

  • Physical barriers (skin, mucous membranes)
  • Inflammation, antimicrobial proteins
  • Specific immunity (T cells, B cells, antibodies, memory cells)
• Pathogens are substances that cause disease (viruses, bacteria, protists, fungi)
• Histamines attract phagocytes to the site of infection
• Plasma cells produce antibodies that match the pathogen's antigens
• Memory cells allow faster immune response upon re-exposure to a pathogen