ARG1 and glioma: Moreover, and consistent with IL-33 driving this pro-tumorigenic environment, assessment of other genetically engineered immunocompetent glioma models identified elevated levels of IL-33 in the neonatal N/tv-a;Cdkn2a−/−;Ptenfl/fl mice (Xfm) PDGFB-driven murine glioma model80 (Fig. 5e), with a corresponding infiltration of Arg1+ TAMs (Fig. 5f).