Human CD33 ELISA Kit (A311794) employs the sandwich enzyme immunoassay technique for the quantitative measurement of human CD33 in serum, plasma or other biological fluids. An antibody specific for CD33 has been pre-coated onto a 96-well microtiter plate. The standards and test samples are added into the wells and the CD33 present in each sample is bound to the wells by the immobilized antibody. Biotinylated Anti-CD33 Antibody, which also binds the CD33 present in each sample, and Streptavidin-HRP, which binds the Biotinylated Anti-CD33 Antibody, are added and the microtiter plate is incubated. Following incubation, unbound Biotinylated Anti-CD33 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 CD33 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 CD33 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.