Review on role of Myeloid-derived Suppressor cells in regulation of immune system

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of cells that expands during cancer, inflammation and infection, and together with regulatory T cells (Tregs) have a remarkable ability to suppress immune responses. The phenotype of MDSCs differs in humans and mice, and the exact mechanisms of their suppressive function are still controversially discussed. Limited data are available on MDSC in humans. Suppressor activity has been associated with high arginase 1 and iNOS activity as well as ROS production by MDSC. MDSCs regulate both acquired and innate immunity by direct or indirect pathways. In this Review, we discuss the origin, mechanisms of expansion and suppressive functions of MDSCs, as well as the potential to target these cells for therapeutic benefit.