Growth Regulated Oncogene Beta (GROb) is a small cytokine belonging to the CXC chemokine family which produced by activated monocytes and neutrophils and expressed at sites of inflammation. Hematoregulatory chemokine, which, in vitro, suppresses hematopoietic progenitor cell proliferation. Besides, Dipeptidyl Peptidase IV (DPP4) has been identified as an interactor of GROb, thus a binding ELISA assay was conducted to detect the interaction of recombinant rat GROb and recombinant rat DPP4. Briefly, GROb were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100ul were then transferred to DPP4-coated microtiter wells and incubated for 2h at 37℃. Wells were washed with PBST and incubated for 1h with anti-GROb 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 of GROb and DPP4 was shown in Figure 1, and this effect was in a dose dependent manner.