Roles of myeloid-derived suppressor cells in tumor immune tolerance

Myeloid-derived suppressor cells (MDSCs),which includes immature dendritc cells,macrophages and other early myeloid progenitors,are a group of myeloid cells with immune suppressive function. MDSCs are characterzied by heterogeneity and plasticity. Increasing evidence has shown that MDSCs are accumulated in tumor mass either in animal model or in the patients with tumor,and this accumulation is involved in tumor immune tolerance. In the present review,we summarize the nature of MDSCs,the factors affecting its accumulation and activation,and its regulation on immune response against tumor.