Antigenicity and Immunogenicity

Antigenicity and Immunogenicity are related but distinct immunologic properties makes it sometimes confused.
Immunogenicity is the ability to induce a humoral and/or cellmediated immune response.

A substance that induces a specific immune response is called an antigen,
it is more appropriately called an immunogen.

Antigenicity is the ability to combine specifically with the final products of the above responses.
Although all molecules that have the property of immunogenicity also have
the property of antigenicity, the reverse is not true.
Some small molecules, called haptens, are antigenic but incapable, by themselves,
of inducing a specific immune response.
They do not have immunogenicity.