Stem Cell Factor Receptor (SCFR), also known as c-Kit and CD117, is a widely expressed 145 kDa receptor tyrosine kinase. Binding of SCF R to SCF promotes the survival, differentiation, and mobilization of progenitor cells in multiple lineages. Mature human SCFR consists of a 499 amino acid (aa) extracellular domain (ECD) with five tandem immunoglobulin-like domains, a 21 aa transmembrane segment, and a 431 aa cytoplasmic domain with the split tyrosine kinase domain. SCFR is up-regulated on dendritic cells by Th2- or Th17-biasing stimuli, and it is required for subsequent dendritic cell induction of Th2 and Th17 responses. Besides, Epidermal Growth Factor (EGF) has been identified as an interactor of SCFR, thus a functional binding ELISA assay was conducted to detect the interaction of recombinant human SCFR and recombinant rat EGF. Briefly, biotin-linked SCFR were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100 ul were then transferred to EGF-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 SCFR and recombinant rat EGF was shown in Figure 1, the EC50 for this effect is 0.09 ug/mL.