Fact 1: Antigens are molecules that the immune system recognizes as foreign to the body.

Fact 2: Antibodies are produced to fight antigens.

Given the two facts above, answer the question "What happens when the immune system recognizes a foreign substance?" with the following 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


 

     Antibodies are formed    