Final answer:
The immune system recognizes and reacts to 'antigenic epitopes', specific parts of a foreign protein. These epitopes trigger the production of antibodies by B cells, allowing the body to defend against infections.
Step-by-step explanation:
The immune system recognizes and reacts to antigenic epitopes, which are specific parts of a foreign protein. Antigens, often proteins with a molecular weight more than 5000 kDa, are identified by immune system cells such as B cells and T cells. When these cells encounter antigens, they may produce antibodies that specifically bind to these foreign proteins, targeting them for destruction. This process is a crucial part of the body's natural defense mechanism against potentially hazardous or lethal infections caused by viruses, bacteria, and other pathogens.
Antigenic epitopes can be thought of as a 'molecular fingerprint' of a pathogen that is recognized by the immune system. The portion of the antigen recognized and bound by an antibody is known as the epitope. These epitopes are presented on the surface of pathogenic cells and are vital for the adaptive immune response, which includes the production of antibodies by B cells, leading to the eventual neutralization or destruction of the invading pathogen.