The cytotoxic mechanisms responsible for EG7 tumor rejection are present in TILs after treatment with anti-CD137 mAb. Mice were challenged s.c. with 5 × 105 EG7 cells and treated i.p. with anti-CD137 mAb on days 9 and 11. Two days later, tumors were removed and TILs were analyzed by flow cytometry for intracellular granzyme B (A left) and percentage of H-2Kb-SIINFEKL tetramer+ cells (A right), surface FasL (B), intracellular IFNγ (C) and surface CD107a (D) expression on gated CD8+ and CD4+ T lymphocytes. Histograms show CD8+ gated T cells that come from a representative experiment. Grey histograms represent isotype-matched control antibody stainings and open histograms protein-specific surface or intracellular stainings from representative cases. The insets in each histogram show the mean fluorescense intensity (MFI) after subtracting the background staining or the percentage of CD107a positive cells (D) for the indicated immunostainings on CD8+ and CD4+ T cells from individual tumors. The experiment was performed with 7-8 mice per group and mean±SEM is included in each histogram.