Colony Stimulating Factor 3, Granulocyte (GCSF) is a cytokine primarily produced by monocytes, macrophages, and endothelial cells. It plays a crucial role in regulating the proliferation, differentiation, and survival of neutrophils, a type of white blood cell essential for combating bacterial infections. G-CSF is widely used clinically to accelerate neutrophil recovery in patients undergoing chemotherapy or hematopoietic stem cell transplantation. It binds specifically to the Colony Stimulating Factor Receptor, Granulocyte (GCSFR), a member of the cytokine receptor family expressed on myeloid progenitor cells and mature neutrophils, thereby initiating intracellular signaling pathways that promote cell growth and function.To detect the activity of recombinant GCSF a functional ELISA assay was performed to evaluate the interaction between recombinant mouse GCSF and recombinant mouse GCSFR.Briefly, GCSF was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to GCSFR-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-GCSF pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody for 1h at 37℃, 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 450/630nm immediately. The binding activity of recombinant mouse GCSF and recombinant mouse GCSFR was shown in Figure 1, the EC50 for this effect is 0.296µg/mL.