We also investigated the expression of Arginase 1 (Arg 1), which is known to be involved in immunosuppressive functions as a second pathway regulating the arginine availability in the TME.43,44 Contrary to Nos2, type 2 cytokines IL-4, IL-10, IL-13 or TGFβ stimulation, but not IFNγ, induced Arg 1 expression in murine macrophages.44,45 In line with previous findings,45Arg 1 expression was not directly modulated by IFNs in BMDCs or BMMCs, or in tumor cells (Supplementary information, Fig. S7, Fig. S9a, b). Here, IL4 is linked to neoplasm.