T-cell exhaustion has been observed in murine models of ALL, in which B-ALL induces the expression of PD1, TIM3 and LAG328, and pediatric cases of B-cell precursor acute lymphoblastic leukemia (BCP-ALL) where high numbers of TIM-3+ CD4+ T-cells is correlated with a higher risk of relapse29. Here, PDCD1 is linked to precursor B-cell acute lymphoblastic leukemia.