TNFRSF9 is a member of the tumor necrosis factor receptor superfamily. It is also called 4-1BB or CD137. 4-1BB/CD137/TNFRSF9 is expressed in activated CD4+ and CD8+ T cells, natural killer cells and dendritic cells. The ligand 4-1BBL/CD137L/TNFSF9 on antigen presenting cells binds to 4-1BB/CD137/TNFRSF9 and costimulates the activation of T cells. The binding of agonistic antibodies to 4 1BB/CD137/TNFRSF9 also leads to costimulation for T cell activation. Studies have shown the effectiveness of targeting 4 1BB/CD137/TNFRSF9 by its agonistic antibodies in cancer immunotherapy.
