Different characteristics of Myeloid-derived suppressor cells from septic and tumor-bearing mice

Abstract

Abstract Background Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of myeloid progenitor cells and immature myeloid cells. These cells have immunosuppressive properties and express myeloid differentiation markers Gr-1 and CD11b in mice. The characteristics of MDSCs in different pathological conditions remain unclear. Methods Polymicrobial sepsis was induced by cecal ligation and puncture. For tumor model, mice were injected s.c. in the flank with 5×105 3LL or B16 tumor cells. Splenic Gr-1+ CD11b+ MDSCs were harvested from 7-day septic mice and three-week tumor-bearing mice, which purified using magnetically assisted cell sorting. Results MDSCs from tumor (3LL and B16)-bearing and septic mice shared a common phenotype and morphology. In contrast to tumor-bearing MDSCs, septic MDSCs were mainly characterized as neutrophil like-MDSCs, which expressed lower levels of CD115. Tumor bearing MDSCs have a greater inhibitory effect on Ag-induced CD4+ T cell proliferation than those from septic mice, and expressed higher levels of ARG-1. In addition, septic MDSCs significantly induced macrophage to M1 (F4/80+ CD206−) and expressed proinflamatory cytokine IL-6, whereas tumor-bearing MDSCs induced macrophage to M2 (F4/80+ CD206+) and expressed anti-inflammatory cytokine TGF-beta. Conclusion Sepsis derived MDSCs are functionally different from tumor-bearing MDSCs, which suggests there different functions in the disease’s progress.