Immunity

• What is an antigen?


  A protein on a pathogens surface causing an immune response
• What are the 2 types of immunity?

  active immunity and passive immunity
• When are you immune to that pathogen?

  once you have memory cells present in your body you are immune to that pathogen
• What is passive immunity?

  Antibodies are received from elsewhere-

  • Can be given by mother through milk or an antiserum (INJECTION OF ANTIBODIES)
• What is active immunity provided by?

  the memory cells
• What is active immunity?

  Provided by the memory cells

  Produced after a primary immune response to a pathogen

  Can be through a vaccine
• how do we get passive immunity?

  given by mother through milk

  given by an antiserum
• whatis an antiserum?

  injection of antibodies
• What is antigenic variability?


  When the antigens on a pathogen change

  some pathogens are more variable than others
• Sometimes the antigens on a pathogen change, this is known as antigenic variability
• Antigenic variability- give details?

  • Antigens can mutate and change shape eg flu, HIV
  • Memory cells cannot recognise pathogen
  • Antibodies no longer complementary to antigens
  • The individual will not be able to initiate a secondary response
• What are the 2 ways that vaccines can be given?

  in mouth

  injected into bloodstream
• What can vaccines be used to prevent?

  both epidemics and pandemcs
• what is an epidemic?


  an infectious disease spreads rapidly in a population or country
• What is a pandemic?


  an infectious disease spreads rapidly across several countries/ continents
• Who might not be vaccinated in a population?

  some people such as very young children or people with a weakened immune system for whom vaccines may not work effectively
• what is the concept of herd immunity?


  if enough of the population have been vaccinated then this also provides some protection to people who have not been vaccinated

  THIS IS CALLED HERD IMMUNITY
• When does herd immunity only work?

  If a high enough % of people have been vaccinated
• when does herd immunity BREAK DOWN and what can this lead to?

  If a significant number of people aren't vaccinated, then herd immunity breaks down

  This can lead to an epidemic of an infectious disease
• Describe how HIV is replicated?

  1. Attachment proteins attach to receptors on helper T cell
  2. RNA enters cell
  3. Reverse transcriptase converts RNA to DNA
  4. Viral protein produced
  5. virus particles assembled and released from cell