Fact 1: Antigens are found on cancer cells and the cells of transplanted organs.

Fact 2: If an antigen causes cancer, it is referred to as a pathogen.

Given the two facts above, answer the question "What are antigens also?" with the following options: 
- resistance
 - negative
 - humans
 - positive
 - pathogens
 - more abundant
 - complex
 - Allergies


 

     pathogens    