immunogen vs antigen

immunogen and antigen both are nouns.

Word	Noun	Adjective	Verb	Adverb
immunogen	Yes	No	No	No
antigen	Yes	No	No	No

As nouns, antigen is a hypernym of immunogen; that is, antigen is a word with a broader meaning than immunogen:

immunogen: any substance or organism that provokes an immune response (produces immunity) when introduced into the body
antigen: any substance (as a toxin or enzyme) that stimulates an immune response in the body (especially the production of antibodies)

immunogen (noun)	antigen (noun)
any substance or organism that provokes an immune response (produces immunity) when introduced into the body	any substance (as a toxin or enzyme) that stimulates an immune response in the body (especially the production of antibodies)