CD137 is a member of the tumor necrosis factor(TNF) receptor family. Its alternative names are tumor necrosis factor receptor superfamily member 9(TNFRSF9), 4-1BB and induced by lymphocyte activation(ILA). CD137 gene was localized to chromosome 1p36.Members of this receptor family and their structurally related ligands are important regulators of a wide variety of physiological processes and play an especially important role in the regulation of immune responses. CD137 can be expressed by activated T cells, but to a larger extent on CD8 than on CD4 T cells. The best characterized activity of CD137 is its costimulatory activity for activated T cells. Crosslinking of CD137 enhances T cell proliferation, IL-2 secretion survival and cytolytic activity. Further, it can enhance immune activity to eliminate tumors in mice.
