ARG2 and pneumonia: Notably, the CXCR2Hi MDSC, with higher ARG2 expression than the CXCR2Low subset (Figure S4C), exhibited a pronounced increase in the sepsis group, as opposed to the healthy and pneumonia groups (0.85% vs. 0.23% and 0.01%, respectively, both p < 0.01) (Figure 3F).