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

Fact 2: Yes, foreigners are called Aliens.

Given the two facts above, answer the question "What are molecules that are recognized by the body as alien?" with the following options: 
- parasites
 - Acids
 - heat or cold
 - negative
 - antigone
 - antibodies
 - antigens
 - blood cells


 

       antigens  