The FBL cell line was a gift from Dr. Philip Greenberg (University of Washington) in 2008 and has been described previously (20 , 21 (link)). FBL has not been authenticated. The FBL cell line is maintained in vivo and cells are harvested from ascites fluid on the day of experiment setup. The HLA-A2+ human melanoma line MeWo was purchased from ATCC in 2014. Peptides from FBL-Gag (CCLCLTVFL) and ovalbumin (SIINFEKL) were obtained from GenScript. Mouse blocking antibodies to CTLA-4 (9D9), PD-1 (RMP1–14) and LAG-3 (C9B7W) were purchased from BioXCell. Human antibodies against CTLA-4, PD-1, and LAG-3 were provided by Bristol-Myers Squibb. All blocking antibodies were administered intraperitoneally (i.p.) at a dose of 100 µg/mouse every 3 days. Fluorochome-conjugated antibodies to mouse CD90.1 (OX-7), CD90.2 (53–2.1), IFNγ (XMG1.2), TNF (MP6-XT22), and anti-CD16/CD32 Fc block (2.4G2) and antibodies to human CD45 (HI30), CD3 (UCHT1), CD4 (RPA-T4), CD8 (SK1), and Foxp3 (259D/C7) were purchased from BD Biosciences. Fluorochrome-conjugated antibody to CD8 (53–6.7) was purchased from BioLegend. Fluorochrome-conjugated antibodies to mouse CD4 (GK1.5), NK1.1 (PK136), Eomes (Dan11mag), and Foxp3 (FJK-16s) and antibody to human T-bet (ebio4b10) were purchased from eBioscience.