ARG1 and neoplasm: In the tumor microenvironment, TGF-β and granulocyte colony-stimulating factor (G-CSF) polarize neutrophils to the N2 phenotype and neutrophil depletion induces a decrease in tumor growth in mouse models.33,34 A single-cell sequencing study demonstrated that specific surface markers of neutrophils such as CD177 were highly expressed in critically ill patients.35 In addition, the expression of immunosuppressive molecules ARG1 and PD-L1 also increased significantly in neutrophils from severely infected patients.