ARG1 and chronic myelogenous leukemia, BCR-ABL1 positive: In addition, CML serum leads to anergy of T cells, probably by increased arginase-1 expression (13) and coincubation of isolated monocytic and granulocytic MDSC of CML patients at diagnosis and autologous CFSE-labeled T cells has been shown to inhibit T cell proliferation, whereas control healthy donor MDSC displayed no suppressive activity (70).