Antigenic variation

• What does the immune system produce in response to foreign antigens?

  Antibodies and memory cells
• How can the immune response be initiated artificially?

  Through vaccination
• Why do different pathogens require different antibodies?

  They display different antigens on their surface
• What happens when a person is vaccinated against measles?

  They produce antibodies against measles
• What is required for immunity against each type of pathogen?

  A specific immune response
• How can immunity be gained aside from natural infection?

  Through vaccination
• What is antigenic variability?

  Changes in surface antigens due to mutations
• Why do new strains of pathogens pose a challenge to the immune system?

  They may not be recognized by memory cells
• What must occur when a new strain of a pathogen is encountered?

  A new primary immune response must occur
• Why must a new flu vaccine be developed every few years?

  To counteract the most common strains
• How many varieties of the virus that causes the common cold exist?

  Around 100 varieties
• Why is it difficult to develop a vaccine for the common cold?

  Many strains exist and it's non-serious
• What are the differences between active and passive immunity?

  • Active immunity:
  • Acquired through natural infection or vaccination
  • Long-lasting protection
  • Passive immunity:
  • Acquired through maternal antibodies or injections
  • Short-term protection