Human FOXO4 / AFX ELISA Kit (A314384) employs the sandwich enzyme immunoassay technique for the quantitative measurement of human FOXO4 / AFX in serum, plasma or other biological fluids. An antibody specific for FOXO4 / AFX has been pre-coated onto a 96-well microtiter plate. The standards and test samples are added into the wells and the FOXO4 / AFX present in each sample is bound to the wells by the immobilized antibody. Biotinylated Anti-FOXO4 / AFX Antibody, which also binds the FOXO4 / AFX present in each sample, and Streptavidin-HRP, which binds the Biotinylated Anti-FOXO4 / AFX Antibody, are added and the microtiter plate is incubated. Following incubation, unbound Biotinylated Anti-FOXO4 / AFX Antibody and unbound Streptavidin-HRP are removed by washing, and two substrate solutions are added to the wells. Color develops in proportion to the amount of FOXO4 / AFX captured in each well. The color development is stopped by addition of stop solution which changes the color from blue to yellow and the intensity of the color is then measured. The concentration of FOXO4 / AFX in the samples can then be calculated by reading the O.D. absorbance at 450nm in a microplate reader and referring to the standard curve.