What role do antigens play in the immune system?

Antigens play a crucial role in the immune system by triggering an immune response. They are typically foreign substances, such as proteins or polysaccharides found on the surface of pathogens like bacteria, viruses, and fungi, as well as on the surfaces of pollen, transplanted tissues, and other foreign materials.

When an antigen enters the body, it is recognized by immune cells, particularly lymphocytes. B cells can produce antibodies specific to the antigen, while T cells can recognize and kill infected cells or help coordinate the immune response. This recognition and subsequent activation result in the immune system mounting a defense to eliminate or neutralize the threat, thereby protecting the body from disease.

While options like attacking the body's own cells or inhibiting pathogen growth might describe other immune mechanisms or abnormalities, the primary function of antigens is to stimulate an appropriate immune response. Their identification and subsequent interaction with immune cells are what essentially kick-starts the complex cascade of actions necessary to address infections or foreign substances. Additionally, the roles of repairing damaged tissues relate more to the healing process rather than the action of antigens in the immune response.