ARG1 and neoplasm: Functionally, MDSCs impair T cell-mediated antitumor immunity through three interconnected mechanisms: (1) direct secretion of ROS, NO, and Arg-1 to disrupt T cell activation and proliferation [141]; (2) induction of Tregs expansion and activation [142]; and (3) subversion of antigen-presenting cell function, thereby blunting tumor antigen-specific immune responses [143].