ARG1 and neoplasm: Conversely, M2 macrophages are identified by their ability to suppress anti-tumor responses by producing IL-10 and TGFβ, recruiting Tregs and Th2 cells, supporting fibrosis to exclude CTLs, sequestering L-arginine through Arginase-1 (Arg-1), and expressing immune checkpoint molecules (100, 102, 192–194).