Abstract:There exists a population of myeloid-origin cells that are associated with tumor immune escape in cancer patients,commonly termed as myeloid derived suppressor cells(MDSCs). MDSCs accumulate in the blood,lymph nodes,bone marrow, and inhibit both adptive and innate immunity.Different suppressive mechanisms are used by MDSCs to block tumor immunity. Reducing the numbers of MDSCs or inhibiting the suppressive pathway conducted by MDSCs will bring new highlight to biotherapy in tumor treatment.