4-1BB (CD137; TNFRSF9), a receptor of TNFSF9/4-1BBL, belongs to the tumor necrosis factor (TNF) receptor superfamily[1]. 4-1BB is helpful for T cell activation and development, and also induces peripheral mononuclear cell proliferation and migration to the tumor microenvironment[2]. 4-1BB is also involved in enhancing Nrf2 and NF-κB pathway mediated apoptosis of endothelial cells[3]. Human 4-1BB protein is a surface glycoprotein with a transmembrane domain (187-213 a.a.). 4-1BB/TNFRSF9 Protein, Human (CHO, Fc) is the extracellular part (L24-Q186) of 4-1BB protein, produced by HEK293 cells with C-terminal hFc-tag.