Answer :
Final answer:
Antigens and epitopes play crucial roles in immune responses.
Explanation:
An antigen is a molecule that reacts with some component of the immune response (antibody, B cell receptor, T cell receptor). An epitope is the region on the antigen through which binding with the immune component actually occurs.
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Answer: D. Alloantigen
Explanation:
The antigen that is present in some but not all members of the same species is called an Alloantigen. When introduced to a member of the same species, the immune system recognizes it as foreign and fights it off.