The Immune System

• What is the role of the immune system

  • Pathogens such as bacteria can release toxins that make us feel unwell 
  • The immune system destroys any pathogens that try to enter the body and any toxins it may produce 
  • The immune system protects us incase the same type of pathogen invades us again in the future
• What are the ways that white blood cells can protect us from pathogens

  • Phagocytosis 
  • Production of antibodies 
  • Production of antitoxins
• What is phagocytosis

  Phagocytosis is where white blood cells engulf and destroy pathogens
• Explain how phagocytosis works

  • The pathogen invades the body 
  • The white blood detects chemicals released from the pathogen and moves towards it 
  • The white blood cell then engulfs the pathogen 
  • Then the white blood cell uses enzymes to destroy the pathogen

  
• What are antibodies and antigens

  • Antibodies are special protein molecules which attach to antigens
  • Antigens are markers on the surface of the pathogen
• Explain how the production of antibodies destroys pathogens


  • The white blood cells become sensitised to the antigens on the pathogens 
  • So they begin to produce antibodies , which lock onto the antigens 
  • This causes the pathogens to clump together , so that other white blood cells can destroy them

  
• Features of antibodies

  • Antibodies are extremely specific - e.g. if a person catches measles , they will develop antibodies that only protect against the measles virus. They will not protect against any other pathogens 
  • Antibodies can remain in the blood for a long time - this means that they can protect us incase we ever get infected again with the same pathogen
• What are toxins

  • Certain bacteria can release toxins 
  • These are chemicals that can make us feel unwell
• Explain how the production of antitoxins works against toxins

  • White blood cells can produce chemicals called antitoxins which are chemicals that neutralise the poisonous effects of the toxins  
  • The antitoxins stick to toxin molecules to prevent them from damaging cells