1. From the Departments of Biochemistry (E.K.A., M.v.B., H.P., C.J.M.d.V.), Experimental Immunology (E.E.), and Radiotherapy (C.v.B.), Academic Medical Center, University of Amsterdam, Amsterdam, and the Gaubius Laboratory TNO-PG (J.M.G., P.H.A.Q.), Leiden, the Netherlands.