Description
Principle of the Assay: The principle of the double antibody sandwich ELISA is represented in Figure 1. In this assay the AGP present in samples reacts with the anti-AGP antibodies which have been adsorbed to the surface of polystyrene microtitre wells. After the removal of unbound proteins by washing, anti-AGP antibodies conjugated with horseradish peroxidase (HRP), are added. These enzyme-labeled antibodies form complexes with the previously bound AGP. Following another washing step, the enzyme bound to the immunosorbent is assayed by the addition of a chromogenic substrate, 3,3',5,5'-tetramethylbenzidine (TMB). The quantity of bound enzyme varies directly with the concentration of AGP in the sample tested; thus, the absorbance, at 450 nm, is a measure of the concentration of AGP in the test sample. The quantity of AGP in the test sample can be interpolated from the standard curve constructed from the standards, and corrected for sample dilution.
Background: AGP is a 52 kDA serine protease inhibitor (serpin) in blood, which protects tissue from enzymes from inflammatory cells, especially elastase. In certain acute phase inflammatory reactions, AGP is elevated in order to limit the damage caused by activated neutrophil granulocytes and their enzyme elastase. Disorders of AGP include AGP deficiency, a hereditary disorder that can lead to severe tissue breakdown during inflammation. This may result in pulmonary emphysema and liver cirrhosis, in severe cases. Genetic variants of AGP do occur