What is the main function of an antigen?

The main function of an antigen is to evoke an immune response. Antigens are substances that are recognized by the immune system as foreign or non-self, triggering the production of antibodies. This process is crucial for the body’s defense against pathogens such as bacteria, viruses, and other foreign invaders. When an antigen enters the body, it is detected by immune cells, which then initiate a response aimed at neutralizing or eliminating the threat. This is a fundamental aspect of immunology, illustrating how the body identifies and reacts to potentially harmful substances.

The other options refer to different biological roles: structural components of cells relate to molecules like proteins and lipids, transport of oxygen in the bloodstream is primarily the role of hemoglobin in red blood cells, and genetic messengers refer to molecules like RNA that convey genetic information from DNA. These functions differ significantly from the specific role of antigens in the immune response.