This observation is most likely in agreement with the low frequency of PSGL-1 expression on ALL blasts (Figure 1B) or a deficient post-translational modification of PSGL-1 and, in contrast to AML blasts, suggests that E-selectin ligands may play a critical role, in the majority of ALL, in promoting primary lymphoblast adhesion to endothelial selectins. This evidence concerns the gene SELPLG and acute myeloid leukemia.