Continuous renal replacement therapy attenuates polymorphonuclear myeloid-derived suppressor cell expansion in pediatric severe sepsis

BACKGROUND: Myeloid-derived suppressor cells (MDSCs) expansion is an important mechanism underlying immunosuppression during sepsis. Though continuous renal replacement therapy (CRRT) may attenuate hyperinflammatory response in sepsis, its role in regulating MDSCs is unknown. The aim of this study was to assess the potential role of CRRT involved in sepsis-induced MDSCs expansion in pediatric sepsis. METHOD: The proportion of polymorphonuclear MDSCs (PMN-MDSCs) was detected before CRRT (pre-CRRT), at 24 hours after CRRT (CRRT 1(st) day) and on the 7(th) day after CRRT (CRRT 7(th) day). The correlation analyses were performed to elucidate the relationship of MDSCs with clinical indexes in sepsis. RESULTS: Totally 22 pediatric patients with sepsis were enrolled [median age 44 (IQR15, 83) months]. PMN-MDSCs were expanded in pediatric sepsis compared with healthy controls (4.30% vs. 0.37%, P=0.04). The proportion of PMN-MDSCs showed a decreased tendency on the CRRT 7(th) day compared with that on the CRRT 1(st) day in survivors (2.29% vs.5.32%, P = 0.088). There was no significant difference in the proportion of PMN-MDSCs between survivors and non-survivors before CRRT (4.51% vs. 3.33%, P=0.745). The levels of interleukin 6 (IL-6) was decreased on the CRRT 7(th) day compared with CRRT 1(st) day in survivors. In the subgroups of patients with significantly decreased IL-6 levels after CRRT, the proportion of PMN-MDSCs on the CRRT 7(th) day were also significantly decreased compared with that on the CRRT 1(st) day (2.21% vs. 6.67%, P = 0.033). CONCLUSION: The proportion of PMN-MDSCs was down-regulated on the CRRT 7(th) day in survivors with sepsis. The reduced PMN-MDSCs expansion may relate to decreased IL-6 level.