HAPTEN

molecular biology> Could be considered an isolated epitope: although a hapten (by definition) has an antibody directed against it, the hapten alone will not induce an immune response if injected into an animal, it should be conjugated to a carrier (usually a protein). The hapten constitutes a single antigenic determinant, probably the excellent known example is dinitro phenol (DNP) that can be conjugated to BSA and against which antiDNP antibodies are produced (antibodies to the BSA can be adsorbed out). Because the hapten is monovalent, immune composite formation will be blocked if the soluble hapten is gift as well as the hapten carrier conjugate (assuming there is more than one hapten for carrier then an immune precipitate can be formed). Competitive inhibition by the soluble little molecule is sometimes referred to as haptenic inhibition and this term has carried over into lectin mediated haemagglutination where monosaccharides are added to try to block haemagglutination: the blocking sugar defines the specificity of the lectin. This entry appears with alow from the Vocabulary of Cell and Molecular Biology