Despite the low percentage of CD11b+CD33+ CD14- HLADR- CD34+ cells (immature myeloid cells, IMCs), CML Gr-MDSCs are more immature compared to autologous PMNs and showed lower levels of expression of CD11b, CD15 and CD16 and lower Arg1 expression and activity (data not shown). This evidence concerns the gene ARG1 and chronic myelogenous leukemia, BCR-ABL1 positive.