What is the primary focus of an antigen?

The primary focus of an antigen is to elicit an immune response. Antigens are typically foreign substances, such as proteins or polysaccharides found on the surface of pathogens like bacteria and viruses, that are recognized by the immune system. When an antigen is detected, it triggers the immune system to produce antibodies and mobilize immune cells, such as T cells, to identify and neutralize the potential threat. This process is crucial for the body's defense mechanisms and plays a fundamental role in how the immune system responds to infections and diseases.

The other options do not accurately reflect the purpose of an antigen. For instance, providing nutrition to cells, responding to physical damage, or assisting in DNA replication pertain to other biological functions and processes not directly tied to the role of antigens in immune responses.