In childhood B-cell lymphoblastic leukemia cells, pre-B cells expressed CCR7 and migrated to CCL19, suggesting that CCR7 plays an important role in pre-B-cell lymphoblastic leukemia chemotaxis, whereas pro-B cells required the presence of the CD40 ligand to be CCL19/CCR7 responsive [253]. The gene discussed is CD40LG; the disease is precursor B-cell acute lymphoblastic leukemia.