Antigens are molecules that the immune system recognizes as foreign to the body.
Antibodies are produced to fight antigens.
When the immune system recognizes a foreign substance, antibodies are produced.
What happens when the immune system recognizes a foreign substance?
Options:
  - an area swollen with pus
  - The immune system fails
  - irradiation
  - Bacteria dies
  - Antibodies are formed
  - major threat to health
  - Something that causes allergies
  - Viruses reproduce