In this sense, PM-MDSCs have been described in different types of hematological malignancies (e.g., multiple myeloma, non-Hodgkin lymphoma, chronic myeloid lymphoma, and myelodysplastic syndromes) to inhibit T cell surveillance, secrete suppressive IL-10 and TGF-β1, show an increase level of Arginase-1 and ROS production, as well as high levels of programmed death receptor ligand 1/programmed death receptor 1 [133,134,135,136,137,138]. The gene discussed is ARG1; the disease is plasma cell myeloma.