Hapten tracer method

Several ELISA formats have been considered, and the one currently being tested is called the "hapten tracer" method. First introduced to this project by Dr. Freya Jung while a postdoctoral fellow in Dr. Hammock s laboratory, this method uses microtiter plates coated with a commercial preparation of goat anti-mouse antibody. Enzyme-labeled hapten competes with analyte for receptor sites on a mouse monoclonal antibody specific for the analyte. The amount of enzyme left after washing is inversely proportional to the... 

Antigens, haptens, and antibodies radiolabeled with or are commonly used as tracers in immunoassay. These nuclides can be introduced directly into functional groups normally present in proteins and other macromolecules or into suitable derivatives that can be synthesized by a variety of chemical procedures. The most widely used iodination methods have been direct chemical or enzymic substitution of hydrogen in tyrosine or related groups using chloramine-T or lactoperoxidase, respectively. These methods are described in separate chapters in this volume. 

I-labeled protein A as a tracer for IgG has been extended to a general immunoassay method for fluid-phase antigen and hapten. The steps involved are summarized in Eqs. (2) and (3). 

For a competitive immunoassay, a fixed quantity of tracer is incubated in the presence of a fixed (lesser) quantity of antibody and variable quantities of the analyte. After incubation, the free and bound fractions of the tracer are separated. Quantification of one or other of the fractions allows calculation of the amount of analyte present. This technique is partictdarly suited to hapten assay. This assay method, requiring a separation step, is known as a heterogeneous assay. In a few particular cases, the free and bound fractions of the tracer give different signals, eliminating the need for the separation step. This is known as a homogeneous-phase assay. 

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