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

Fact 2: Children are born with an immature immune, or defense, system.

Given the two facts above, answer the question "What are molecules that the defense system recognizes as foreign to the body?" with the following options: 
- Allergies
 - lungs
 - antigens
 - bacteria
 - parasites
 - atoms
 - red blood cells
 - acetic acid


 

   antigens      