What defines an immunogen?

An immunogen is specifically defined as an agent that stimulates an immune response. This means that when an immunogen is introduced into the body, it triggers the immune system to recognize it as foreign, leading to the production of antibodies or activation of T-cells. Immunogens can include various substances such as proteins, polysaccharides, and even some nucleic acids that are capable of eliciting a response from the immune system.

Understanding the significance of immunogens is crucial in areas like vaccine development, where substances are intentionally used to provoke a protective immune response without causing disease. In contrast, substances that do not provoke an immune response or inhibit the immune system do not qualify as immunogens, nor do pathogens that simply cause harm without invoking a specific immune response. The key aspect of an immunogen is its ability to activate the immune system and generate a response that provides protection or immunity against future encounters with the same or similar antigens.