Detection of Circulating and Tissue Myeloid-Derived Suppressor Cells (MDSC) by Flow Cytometry

Flow cytometry allows the multiparameter analysis of heterogeneous cell populations and is an essential tool for detecting and characterizing different cell populations from peripheral blood and dissociated tissues. Myeloid-derived suppressor cells (MDSC) are a heterogeneous and plastic group of myeloid precursors with immune-suppressive capacity, which are a characteristic feature of chronic inflammation, such as cancer. The optimal measurement of MDSC levels could be used as a biomarker for clinicians for prognosis and/or management and for researchers to track and understand the role of MDSC in different pathological diseases.The criteria for defining MDSC include phenotypic surface markers, but ideally should also include the functional immunosuppressive effect on T cells, and, if possible, assessing the main biochemical and molecular features. Two major functional mechanisms to suppress T cell responses are the production of arginase-1 and reactive oxygen species (ROS) molecules. Here is presented a nine-parameter seven-color flow cytometric assay to identify and quantify MDSC from both peripheral blood mononuclear cells (PBMC) and dissociated tissue (e.g., tumor) by using fluorescence-tagged antibodies against surface markers. Also, the intracellular levels of arginase-1 and superoxide (O₂^-) content were performed to potentially distinguish their functional status.