CD8A and neoplasm: To establish whether CD8+ T cell cytotoxic activity is directly responsible for the reduction in tumor growth, we repeated the orthotopic syngeneic transplantation experiment with 7940b KPC cells in Cd4;Tcf7fl/fl and Cd4;Tcf7+/+ mice, and randomized mice to receive isotype control IgG or anti-CD8 antibody (Fig. 2 F).