IL7R and precursor B-cell acute lymphoblastic leukemia: In agreement, homozygous expression of mutant IL7R in CD2CrePos.Il7rcpt/cpt mice led to early accumulation of B cell precursors in the blood (Fig. 5a), rapidly followed by precursor B-ALL establishment (Fig. 5b, c, Supplementary Fig. 16 and Supplementary Data 1).