To examine whether a similar increase in PD-1 expression with leukemia evolution is observed in other mouse leukemia models, we evaluated, together with B-ALLs appearing in Pax5+/− (n = 14) animals, those that originated in transgenic Sca1-ETV6-RUNX1 (n = 3) mice [36,47]. Here, PDCD1 is linked to leukemia.