Fibrinogen Like Protein 1 (FGL1), also known as fibrinogen-related protein 1 or HFREP-1, is a member of the fibrinogen family. FGL1 has multiple biological functions, which plays an important role in intercellular signaling, immune regulation, cell adhesion and angiogenesis. In addition, the expression of FGL1 protein is also up-regulated in tumor tissues, such as lung, prostate, melanoma, colorectal, breast cancer, and brain tumors, suggesting that it may play an important role in the development and progression of these diseases. Fibrinogen Alpha Chain (FGA) has been identified as an interactor of FGL1, thus a functional binding ELISA assay was conducted to detect the interaction of recombinant human FGL1 and recombinant mouse FGA. Briefly, biotin-linked FGL1 were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100 ul were then transferred to FGA-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST 3 times and incubation with Streptavidin-HRP for 30min, then wells were aspirated and washed 5 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 nm immediately. The binding activity of recombinant human FGL1 and recombinant mouse FGA was shown in Figure 1, the EC50 for this effect is 0.07 ug/mL.