Interleukin 15 (IL15), encoded by the IL15 gene in humans, is a pleiotropic cytokine of the common gamma-chain family. It plays critical roles in immune regulation, especially in maintaining the survival, proliferation, and activation of T cells, natural killer (NK) cells, and dendritic cells. Produced mainly by monocytes, macrophages, and epithelial cells, IL15 exerts its biological effects via a unique "trans-presentation" mechanism, often relying on binding to its receptor. IL15 is linked to immune responses against infections and tumors, and its dysregulation is associated with autoimmune diseases and inflammatory disorders. IL15 binds specifically to Interleukin 15 Receptor alpha (IL15Ra, encoded by IL15RA), forming a complex to initiate downstream signaling.Thus a functional ELISA assay was conducted to detect the interaction of recombinant musculus IL15 and recombinant human IL15Ra. Briefly, IL15 was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to IL15Ra-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-IL15 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 musculus IL15 and recombinant human IL15Ra was shown in Figure 1, the EC50 for this effect is 0.21561µg/mL.