Myeloid-Derived Suppressor Cells and Therapeutic Strategies in Cancer

Figure 1

Surface markers and suppressive mechanisms of MDSCs. In murine cancer models, G-MDSCs (CD11b⁺) and M-MDSCs (CD11b⁺Ly6G⁻) can be discriminated by the cell surface markers. However, identifying human MDSCs is still challenging because of their phenotypic heterogeneity and the absence of cognate surface markers in mice. Generally, human MDSCs can be defined as CD11b⁺CD33⁺HLA- and further divided to CD15⁺ or CD66b⁺ G-MDSCs and CD14⁺ M-MDSCs. A substantial population shows both CD15 (or CD66b) and CD14 negative, suggesting that G-MDSCs and M-MDSCs are not completely distinct population. M-MDSCs can differentiate mature dendritic cells and macrophages or putatively G-MDSCs.