We show that: a- The previously reported model of acute (Arm) vs. chronic (Cl13) LCMV infection could be employed in modeling antigen-specific T cell exhaustion against cancer cells; b- This correlated with PD-1high GP33+ T cells in the brains of Cl13 but not Arm mice; and c- This lethality was partially but significantly reversed by anti-PD1 treatment. This evidence concerns the gene PDCD1 and cancer.