IDO1 and acute lymphoblastic leukemia: After hematopoietic reconstitution with IFN‐γ‐ or control‐transduced HSPC and B‐ALL challenge, we treated the mice with either monoclonal antibodies directed against the inhibitory T cell checkpoints CTLA4 (αCTLA4) or LAG3 (αLAG3), thereby reducing T‐cell exhaustion, or with the IDO inhibitor 1‐methyltryptophan (1‐MT).