Mouse lymphoma cell lines, RMA (H-2b) and TAP-2-deficient RMA-S (H-2b),19 (link) were cultured in RPMI-1640 medium (Sigma-Aldrich, St. Louis, MO) with 10% FCS (Sigma-Aldrich) (R-10). The HHD gene-transfected cell lines, RMA-HHD and RMA-S-HHD, were previously described,15 (link) and maintained in R-10 containing 500 μg/ml G418 (Nacalai Tesque, Kyoto, Japan). A human kidney cell line, 293 cell lines were obtained from the American Type Culture Collection (ATCC) (Rockville, MD). The Ad-293 cell line was provided with the AdEasy adenoviral vector system (Agilent Technologies, La Jolla, CA). 293 and Ad-293 cells were maintained in DMEM (Sigma-Aldrich) supplemented with 10% FCS (Sigma-Aldrich).