Insulin-like growth factor 2 (IGF2) is one of three protein hormones that share structural similarity to insulin. It has growth-regulating, insulin-like and mitogenic activities.IGF2 exerts its effects by binding to the IGF-1 receptor and to the short isoform of the insulin receptor. IGF2 may also bind to the IGF2 receptor (also called the cation-independent mannose 6-phosphate receptor), which acts as a signalling antagonist; that is, to prevent IGF2 responses. Besides, Insulin Receptor (INSR) has been identified as an interactor of IGF2, thus a functional binding ELISA assay was conducted to detect the interaction of recombinant rat IGF2 and recombinant human INSR. Briefly, IGF2 were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100 ul were then transferred to INSR-coated microtiter wells and incubated for 2h at 37℃. Wells were washed with PBST and incubated for 1h with anti-IGF2 pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody, wells were aspirated and washed 5 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 450 nm immediately. The binding activity of recombinant rat IGF2 and recombinant human INSR was shown in Figure 1, the EC50 for this effect is 0.71 ug/mL.