A relatively small, lipophilic, nonprotein molecule that is able to elicit an immune response (contact or delayed hypersensitivity) only when bound to a carrier protein. Any chemical, drug, or its metabolite that combines with tissue protein to form a complete antigen; most allergenic drugs are haptens.
A small molecule that can elicit an immune response only when attached to a large carrier such as a protein.
A small foreign molecule that will stimulate an immune system response (e.g., antibody production) if the small molecule (now called a haptenic determinant) is attached to a macromolecule (carrier) to make it large enough to be recognized by the immune system.
A substance that does not stimulate antibody formation but that will combine with a carrier antigen to stimulate antibody formation.
Small antigenic determinants capable of eliciting an immune response only when coupled to a carrier. Haptens bind to antibodies but by themselves cannot elicit an antibody response.
A substance which causes an allergy, probably by changing a protein so that it becomes antigenic.
Fraction of a micro-organism (such as the capsular polysaccharide of the pneumococcus) which is unable by itself to stimulate antibody production, but which will react in vitro with antibodies elaborated in response to infection by the entire organism.
A specific portion of an antigen molecule.
A substance that does not act as an antigen or stimulate an immune response on its own but can do so when combined with an immunogenic carrier molecule.