Interleukin-25 (IL-25) is a cytokine belonging to the IL-17 family, also known as IL-17E. It is primarily secreted by Th2 cells and mast cells, playing a key role in promoting type 2 immune responses. IL-25 induces the production of cytokines such as IL-4, IL-5, and IL-13, stimulating eosinophil expansion and contributing to allergic inflammation and anti-parasitic defenses.IL - 25 binds to a heterodimeric receptor complex composed of IL - 17RA and IL - 17RB. This binding initiates signaling cascades that lead to the activation of downstream immune - related pathways.Thus a functional binding ELISA assay was conducted to detect the interaction of recombinant rat IL-25 and recombinant human IL17RA .Briefly, biotin-linked IL-25 were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100μl were then transferred to IL17RA-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 recombinant rat IL-25 and recombinant human IL17RA was shown in Figure 1, the EC50 for this effect is 0.59ug/mL.