antigen
//ˈæn.tɪ.dʒən//
Noun
antigenSingular
antigensPlural
1
A substance, typically a protein or polysaccharide, that triggers an immune response in the body, especially the production of antibodies.
The antigen in the vaccine stimulates the body to produce antibodies.
2
A molecule or molecular structure on the surface of a pathogen, such as a virus or bacterium, that is recognized by the immune system as foreign.
The immune system produces antibodies when it detects antigens on the surface of a virus.