The clinical significance of myeloid-derived suppressor cells in patients with sepsis: a prospective cohort study

Accumulating evidence has established a correlation between Myeloid-derived suppressor cell (MDSC)-mediated immunosuppression and the prognosis of sepsis and septic shock. Nevertheless, whether MDSCs are associated with distinct infection foci or pathogen types has yet to be determined. The present study therefore aimed to clarify the significance of peripheral blood MDSCs in this context. This single-center, prospective observational cohort study enrolled patients according to predefined inclusion and exclusion criteria. Demographic characteristics, clinical data, and blood samples were collected from all participants. Flow cytometry was performed to detect the percentage of MDSCs in different groups, and the results were subsequently compared and analyzed to further elucidate the role of MDSCs in sepsis by investigating their association with distinct infectious origins. The expression levels of both PMN-MDSCs and M-MDSCs were significantly higher in the sepsis group than in the healthy control group (4.92 ± 0.31 vs. 2.20 ± 0.14, t = 6.87, P < 0.01; 19.40 ± 1.31 vs. 7.93 ± 0.45, t = 6.80, P < 0.01, respectively). However, no significant differences were observed in the levels of these subsets between the general sepsis and septic shock groups (t = 0.56, P = 0.58; t = -1.43, P = 0.16). Patient mortality was significantly correlated with both PMN-MDSCs (Wald = 5.56, P = 0.01, 95% CI: 0.43-0.92) and M-MDSCs (Wald = 5.25, P = 0.02, 95% CI: 0.98-1.26). Regarding infection sites, M-MDSC expression was significantly lower in pulmonary infections compared to urinary tract infections (t = 2.77, P = 0.01). In contrast, no significant differences were found in PMN-MDSC expression between Gram-positive and Gram-negative bacterial infections (t = 0.99, P = 0.32). However, M-MDSC expression levels were significantly higher in Gram-negative infections than in Gram-positive infections (t = 2.97, P = 0.02). MDSC-mediated immunosuppression correlates with patient prognosis and mortality risk. While no early-stage difference in MDSC expression was found between sepsis and septic shock-underscoring the need for dynamic monitoring-expression levels did vary by infection site. Specifically, M-MDSCs were significantly elevated in urinary tract infections and were more pronounced in Gram-negative than in Gram-positive bacterial infections.