TNFRSF9, also known as CD137 or ILA, is a member of the TNF superfamily of receptors. This protein is mainly expressed on the surface of a variety of T cells, but also found in B cells, monocytes, and various transformed cell lines. TNFRSF9 is expressed on activated T cells and binds an inducible ligand that is found on B cells, macrophages and dendritic cells. Recombinant human TNFRSF9 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.