15] Two-site enzyme immunoassay for nerve growth factor

Abstract

Publisher Summary This chapter describes immunological determinations of nerve growth factor (NGF), although it should be noted that probably as many difficulties occur in the determination of its biological activity. The enzyme immunoassay presented in the chapter is sufficiently sensitive to analyze the physiologically relevant NGF levels. The use of both mono- and polyclonal anti-NGF antibodies together with the use of nonspecific antibody preparations as background control is essential to ensure the specificity of the NGF determination with the two-site enzyme immunoassay. Many false-positive NGF determinations have been obtained using competition assays. Such results could not be confirmed with both reliable two-site immunoassays and biological assay methods. The difficulties encountered in NGF determinations are because of the presence of NGF-binding proteins and the strong nonspecific adsorptivity of NGF. These difficulties become significant at the extremely low NGF levels in tissues in which NGF has a physiological role. Problems arising from the presence of binding proteins are not unique for NGF, but have also been reported for other rare proteins such as platelet-derived growth factor.