This kit is based on the solid-phase enzyme-linked immunosorbent assay (ELISA) with a double-antibody sandwich technique to quantity the amount of CHO PLBL-2 protein in biological products. A CHO PLBL-2-specific capture antibody was pre-coated into each well of microtiter strips. Both Calibration Standards and test samples were simultaneously added to the microtiter strips, and followed by incubation and washing. The biotinylated detection antibody was added to the microtiter strips to bind the epitope of CHO PLBL-2 protein, thus forming a sandwich structure which further reacted with streptavidin-labeled HRP (SA-HRP). TMB substrate was added into reaction, catalyzed by enzymatic hydrolysis to produce a blue colored produc. Finally, a stop solution was added to terminate the enzymatic reaction, resulting in a yellow colored product (maximum absorption peak at 450 nm). The absorbance values at 450 nm wavelength were positively correlated with the CHO PLBL-2 concentration in the Calibration Standards and the samples. The concentration of CHO PLBL-2 protein in the sample can be calculated using a dose-response curve.