Immunotherapy doublets result in increased frequencies of tumor antigen-specific T cells at later time points in the periphery. Depicted is an IFN-γ ELISpot of splenocytes harvested on day 14 with open bars being the un-stimulated control and filled bars representing SIY-stimulation. Data are shown as the mean +/− SEM from 10 mice pooled from two experiments. Statistical analysis was done using Mann–Whitney-U test comparing all groups to no treatment. All double treatment groups were significantly different to their respective single treatment and when comparing double treatments within each other a significant difference between αCTLA4 + αPD-L1 and αPD-L1 + IDOi was observed.