Abstract: Myeloid-derived suppressor cells (MDSCs) and regulatory T cell (Treg) in the tumor microenvironment are important inhibitory immune cells. Research finds that MDSC and Treg increase in large number under the conditions of inflammation, infection and cancer and are able to suppress the immunity system and promote tumor-cell invasion and metastasis through multiple mechanisms. Finding the causes of resulting in the increase of MDSCs and Treg in tumor microenvironment and the eliminating methods have become new focuses in the field of anti-tumor immunotherapy.

Key words: Immunosuppression, Inflammation, Neoplasms, T-lymphocytes, regulatory, Myeloid-derived suppressor cells