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noun, plural: haptens

A substance that induces immune response when bound to a carrier protein or to large antigenic molecule.


Hapten is a type of antigen that elicits production of antibodies only when combined with another antigenic molecule, such as immunogen. It can however react with previously existing antibodies.

A well known example of a hapten is urushiol, which is the toxin found in poison ivy.

Word origin: German : Greek haptein, to fasten + German -en, n. suff. (from Greek -ēnē, -ene).

Variant: haptene
Also called: partial antigen or incomplete antigen

See also: immunogen, antigen.

Related terms: