The present invention provides an immune effector cell comprisinga) an antigen binding receptor, wherein said antigen binding receptor binds to a tag of a tagged polypeptide, and wherein the polypeptide of said tagged polypeptide binds to an antigen expressed on the surface of a target cell, or binds to a tumor associated antigen expressed on the surface of a target cell, wherein said target cell is a cancer cell, and wherein the binding of said antigen binding receptor to said tag or said tumor associated antigen activates and stimulates an immune response of said immune effector cell； andb) a chimeric costimulatory receptor (CCR), wherein said CCR binds to a further antigen, wherein said further antigen is not expressed on the surface of said target cell,and wherein the binding of said CCR to said further antigen boosts said immune response of said immune effector cell and/or ensures survival of said immune effector cell.
