EMT Medical Terminology Practice Test

The concept being tested is what an antigen is. An antigen is any foreign molecule or part of a molecule that the immune system recognizes as a target to mount a response. When the immune system detects an antigen, it can produce antibodies specifically designed to bind that antigen. So the term refers to the thing that triggers the antibody response.

Antibodies are the proteins created by B cells that bind to the antigen, not the molecules themselves. A pathogen is a living agent that can cause disease (like bacteria or viruses), and a toxin is a poisonous substance produced by organisms. Both can be associated with antigens, but the word that describes the foreign protein you form antibodies against is antigen.