CD137, a member of the tumor necrosis factor (TNF) receptor family, is a type 1 transmembrane protein, expressed on surfaces of leukocytes and non-immune cells.[5][6] Its alternative names are tumor necrosis factor receptor superfamily member 9 (TNFRSF9), 4-1BB, and induced by lymphocyte activation (ILA). It is of interest to immunologists as a co-stimulatory immune checkpoint molecule, and as a potential target in cancer immunotherapy.
immunotherapy
was invoked but never defined (see the help page).