Immunoassay. Development and directions in antibody technology.

Improvements and new applications for the technique of immunoassay have been extensive, owing in part to improvements in specific binding reagents used. Early reports advocated application of naturally occurring antibodies, specific serum-binding proteins, and receptors as binding reagents in immunoassays. Each is still used today, although applications are limited because affinities are generally low. Polyclonal antibodies produced in laboratory animals in response to injection of specific antigens have been the cornerstone of immunoassay because of their high affinities and wide range of specificities. Recently, monoclonal antibodies have begun to replace polyclonal antibodies because of improved specificity, ease of use, production of an unlimited supply, and advantages of worldwide assay standardization. Although only 50 analytes are currently measured by Food and Drug Administration--approved reagents, widespread use in the future is predicted.