Fig. 1.

MDSC development and cell subsets in mice and humans. IMCs are part of the normal process of myelopoiesis. IMCs can differentiate into granulocytes, macrophages, and dendritic cells. However, IMCs can also differentiate into MDSCs, especially in some pathological conditions. MDSCs have two major subsets. In mice, G-MDSCs are defined as CD11b⁺Ly6C^lowLy6G⁺ cells, and M-MDSCs are defined as CD11b⁺Ly6C^highLy6G⁻ cells. In humans, G-MDSCs are characterized as CD11b⁺CD14⁻CD15⁺/CD11b⁺CD14⁻CD66⁺ cells, and M-MDSCs are defined as CD11b⁺CD14⁻CD15⁻/CD11b⁺CD14⁻CD66⁻ or CD11b⁺CD14⁺HLA⁻DR^low cells