Serologic assays for antigens and antibodies

The number of analytes measured by immunologic methods continues to increase as new biomolecules are identified and characterized. These molecules are either detected as antigens using specific antisera as reagents or as antibodies that bind to their respective solution phase or insolubilized antigen. Although a spectrum of immunologic methods historically has been used to detect antigens and antibodies in serum, only nephelometric-turbimetric assays based on immunoprecipitation and the immunoassay in its many forms possess a sufficient sensitivity in the microgram-per-liter range to be classified as primary tools for sensitive analyte quantitation in today's clinical laboratory. This article describes several immunoassay formats for antigen and antibody measurement and illustrates the sequence necessary in their development.