+An **antigen** is a molecule capable of triggering an [Immune Response](/wiki/immune_response) in a living organism. Often a foreign substance, it acts as a unique signature, allowing the body to recognize and potentially fight off invaders like a [Virus](/wiki/virus).
+## See also
+- [Antibody](/wiki/antibody)
+- [Pathogen](/wiki/pathogen)
+- [T Cell](/wiki/t_cell)
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