Apolipoprotein A1 (APOA1) is the major protein component of HDL particles in plasma. It is a cofactor for lecithin cholesterolacyltransferase (LCAT) which is responsible for the formation of most plasma cholesteryl esters. ApoA1 was also isolated as a prostacyclin (PGI2) stabilizing factor, and thus may have an anticlotting effect. ApoA1 is often used as a biomarker for prediction of cardiovascular diseases. Besides, Plasminogen Activator, Urokinase (uPA) has been identified as an interactor of APOA1, thus a functional binding ELISA assay was conducted to detect the interaction of recombinant rat APOA1 and recombinant human uPA. Briefly, APOA1 were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100 ul were then transferred to uPA-coated microtiter wells and incubated for 2h at 37℃. Wells were washed with PBST and incubated for 1h with anti-APOA1 pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody, wells were aspirated and washed 3 times. With the addition of substrate solution , wells were incubated 15-25 minutes at 37℃. Finally, add 50 µL stop solution to the wells and read at 450/630 nm immediately. The binding activity of recombinant rat APOA1 and recombinant human uPA was shown in Figure 1. The binding activity of recombinant rat APOA1 and recombinant human uPA was shown in Figure 1, and this effect was in a dose dependent manner.