Variation + protection from viruses

• Aggulation

  Antigens bind to pathogens causing them to clump together

  Clumps destroyed by phagocytosis

  Easier to engulf more pathogens at a time
• Neutralising toxins

  Neutralising toxins released by pathogens
• Preventing viruses from entering host cells

  Viruses have spike cells which recognise and bind to receptors on the surface of the host cell which allows them entry

  Antibodies bind to these on viruses and stop them from attaching to the host cells
• Antigenic variation

  Some pathogens can form different strains caused by mutations in genetic material, which usually have different antigens

  If rei-nfected memory cells wont be activated as they wont recognise the antigen and the antibodies made last time wont be complimentary

  So the body has to start again with the primary response