What are antigens?

Antigens are defined as molecules that elicit the production of antibodies. They are often foreign substances such as proteins or polysaccharides found on the surface of pathogens (like bacteria and viruses) or other substances that the immune system recognizes as non-self. When an antigen is detected by the immune system, it triggers a response that results in the production of specific antibodies designed to neutralize or eliminate the antigen. This process is fundamental for adaptive immunity, as it helps the body remember and respond more effectively to future encounters with the same antigen.

Antigens can vary widely in their structure and composition, and they play a crucial role in the immune response. The immune system’s ability to identify and respond to an array of antigens is key to protecting the body from infections and diseases. The other answer choices relate to different components or functions of the immune system but do not accurately define antigens. For instance, cells that seek and destroy pathogens refer to immune cells like phagocytes or T-cells, rather than the molecules that invoke an immune response.