Interleukin-34 (IL-34) is a cytokine that binds to colony-stimulating factor-1 receptor (CSF-1R) and plays crucial roles in monocyte survival, differentiation, and osteoclastogenesis. It is also involved in inflammatory responses, autoimmune diseases, and tumor microenvironment regulation. IL-34 is produced by various cell types, including keratinocytes, neurons, and endothelial cells, and has been implicated in pathological conditions such as rheumatoid arthritis, neurodegenerative disorders, and cancer progression.Besides,Signal Transducer And Activator Of Transcription 3 (STAT3) has been identified as an interactor of IL-34, thus a functional binding ELISA assay was conducted to detect the interaction of recombinant human IL-34 and recombinant human STAT3 . Briefly, biotin-linked IL-34 were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100μl were then transferred to STAT3-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 50µl stop solution to the wells and read at 450nm immediately. The binding activity of IL-34 and STAT3 was shown in Figure 1, the EC50 for this effect is 0.05µg/mL.