Consistent with the accumulation of CXCR2Hi MDSCs, ARG2 contents in blood samples from septic patients were significantly elevated compared to either the healthy (2.89 ng/mL vs. 0.65 ng/mL, p < 0.001) or the pneumonia (2.89 ng/mL vs. 1.67 ng/mL, p = 0.015) group (Figure 3I and Figure S4G). Here, ARG2 is linked to pneumonia.