Immunophenotyping of Circulating Myeloid-Derived Suppressor Cells (MDSC) in the Peripheral Blood of Cancer Patients.

Myeloid-derived suppressor cells (MDSC) are a heterogeneous group of pathologically expanded myeloid cells with immunosuppressive activity. According to their phenotype, MDSC can be divided into three major subpopulations: early stage MDSC (e-MDSC), lacking myeloid lineage markers, monocytic MDSC (M-MDSC), and granulocytic MDSC (PMN-MDSC). Additionally, PMN-MDSC can be subdivided based on their activation and differentiation status, although it is not clear how this status contributes to immunosuppression and disease pathology. Here, we describe an immunophenotyping and gating strategy for the identification and isolation of MDSC subsets based on fluorescence-activated cell sorting. This method allows direct comparison of MDSC subsets in clinical settings.