The affinity biosensor IAsys was used to monitor the interaction of interleukin-2（IL-2） and its soluble receptor in real-time in order to reveal the interaction mechanism of IL-2 and its soluble receptor in vivo.Biotin-labeled sIL-2R was immobilized on the surface of IAsys cuvette

then IL-2 was added into the cuvette.The interaction between IL-2 and sIL-2R was studied by detecting the change in the refractive index on the biosensor surface.The experimental results show that IL-2 could bind to sIL-2R specifically.IAsys biosensor has been known independently as surface sensitive analytical device capable of on-line monitoring of interfacial reactions between biomolecules.It provides an effective method and new idea for the study of interaction between cytokine and receptor.