Anti-PDL1 mAb treatment restored CD8⁺ T-cell function and rescued gal-9 KO mice from AML. WT or gal-9 KO mice (10 mice/group) were injected iv with 10⁶ C1498FFDsR cells. Anti-PDL1 mAb or control rIgG was administered as described. (A) Anti-PDL1 mAb treatment significantly reduced tumor burdens in WT mice 14 and 21 days post-AML injection. Gal-9 KO mice had a more dramatic decrease in tumor burdens on days 14, 21, 28, and 34, compared with WT mice. (B) Anti-PDL1 treatment prolonged the survival of AML-bearing WT mice (□ vs ■, P < .0001). Gal-9 KO mice had an increased survival from AML compared with WT mice (▴ vs ■, P < .05). Gal-9 KO mice were protected from AML by anti-PDL1 treatment and remained tumor-free by 60 days (▵ vs ■, P < .0001).