ARG1 and neoplasm: Specifically, the expansion of these early populations of myeloid cells, including a granulocyte subtype (CD11b+Ly6G+Ly6Clo) and a monocytic subtype (CD11b+Ly6G-Ly6Chi) that migrate to the tumor site, lead to the upregulation of immunosuppressive genes ARG1 and iNOS, suppress T cell activity, and ultimately differentiate into tumor associated macrophages50.