Fibroblast Growth Factor 19 (FGF19) is a member of the fibroblast growth factor (FGF) family. FGF19 has important roles as a hormone produced in the ileum in response to bile acid absorption, regulates new bile acid synthesis, acting through the FGFR4/Klotho-β receptor complexes in the liver to inhibit CYP7A1. FGF19 also has metabolic effects, affecting glucose and lipid metabolism. Besides, Fibroblast Growth Factor Receptor 1 (FGFR4) has been identified as an interactor of FGF19, thus a binding ELISA assay was conducted to detect the interaction of recombinant human FGF19 and recombinant human FGFR4. Briefly, FGFR4 were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100 µl were then transferred to FGF19-coated microtiter wells and incubated for 2h at 37℃. Wells were washed with PBST and incubated for 1h with anti-FGFR4 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 50µL stop solution to the wells and read at 450nm immediately. The binding activity of FGF19 and FGFR4 was shown in Figure 1, and this effect was in a dose dependent manner, the EC50 was approximately 0.016 ug/mL.