ARG1 and chronic myelogenous leukemia, BCR-ABL1 positive: Since Arg1 appears to be the major mediator of T cell suppression by both Gr-MDSCs and PMNs in cancer patients [29], [30], [39], [40], we analyzed Arg1 expression and activity in these two myeloid subsets comparing CML Gr-MDSCs to autologous PMNs.