Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
An antigen is any substance that triggers an immune response in the body, especially the production of antibodies. It is often a foreign substance from the environment, such as bacteria, viruses, pollen, or chemicals.
Related terms
Antibody: A protein produced by the immune system that specifically binds to a matching antigen to neutralize or destroy it.
Immune response: The body's defensive reaction to foreign substances or pathogens that involves recognizing, targeting, and eliminating these invaders.
Lymphocyte: A type of white blood cell involved in the adaptive immune response, including B cells and T cells that are key players in recognizing and responding to antigens