Immunogenicity Versus Antigenicity

From DrugPedia: A Wikipedia for Drug discovery

Immunogenicity and antigenicity are related but distinct immunologic properties that sometimes are confused. Immunogenicity is the ability to induce a humoral and/or cellmediated immune response: Although a substance that induces a specific immune response is usually 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 (i.e., antibodies and/or cell-surface receptors). 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. In other words, they lack immunogenicity. Immunogenicity is not an intrinsic property of an antigen but rather depends on a number of properties of the particular biological system that the antigen encounters. The next two sections describe the properties that most immunogens share and the contribution that the biological system makes to the expression of immunogenicity.