ARG1 and neoplasm: Tumor-associated macrophages, when polarized to an M2-like phenotype, suppress antitumor immunity.31 Microglia/macrophage infiltration was comparable in all treatment groups, whereas arginase-1-positive cells (a hallmark of the microglia/macrophage M2 signature) were slightly reduced following all treatments (Supplementary Figure 4G and H).