Final answer:
Antigens are molecules that induce an immune response, while epitopes are specific regions on antigens that are recognized by the immune system. A single antigen can contain multiple epitopes, and the specificity of immune recognition is determined by these individual epitopes.
Step-by-step explanation:
To understand the immune response, we need to clarify two key concepts: epitopes and antigens. Antigens are molecules, often macromolecules like proteins or polysaccharides, that can induce an immune response. These include foreign substances from pathogens like bacteria and viruses. An epitope, on the other hand, is a specific region on an antigen that is recognized by the immune system, specifically by antibodies or by the receptor molecules on the surface of B cells and T cells.
A single antigen can contain multiple epitopes, each of which can be targeted by a different antibody. Each epitope determines the specificity of the immune recognition; that is, how an antibody or receptor recognizes and binds to a particular antigen. The interaction between an antibody and an epitope is highly specific, much like a lock and key, ensuring that the immune system can precisely target and respond to specific pathogens.
Therefore, the correct answer that explains the difference between an epitope and an antigen is (d) All of the above: a) Epitope is a specific region on an antigen recognized by the immune system, b) Antigen is a molecule that can induce an immune response, and c) Epitope determines specificity in immune recognition.