Rapid Isolation of untouched mouse MDSCs

Abstract Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of cells that regulate immune responses in cancer, chronic infections and inflammatory conditions. In an individual with a tumor burden, MDSCs accumulate in peripheral lymphoid organs and within the tumor microenvironment. In several human cancers, and in mouse tumor models, the presence of high numbers of MDSCs correlates with tumor growth, metastasis and an overall poor prognosis. Approaches that impair the activity or deplete MDSCs have shown promise in animal models. Thus, MDSCs are an attractive target for therapeutic intervention. We have developed an immunomagnetic method for the isolation of untouched mouse MDSCs. Using CyTOF analysis of cell surface antigens on spleen cells from tumor bearing mice, we developed a cocktail of antibodies that targets non-MDSCs for removal using a column-free, negative selection protocol. Our method isolates CD45+CD11b+Gr1+ cells with the following purity and recovery from spleen, BM and blood: MDSCs (CD11b+Gr1+) from tumor-bearing miceTissuePurity (±SD)Recovery (±SD)Spleen94 ± 2.1%50 ± 12%Blood99 ± 0.6%55 ± 7.0%Bone marrow96 ± 1.0%68 ± 5.6% (naïve) As a functional test, naïve mouse splenocytes were labeled with a proliferation dye and the T cells were activated with anti-CD3 and anti-CD28 antibodies. MDSCs isolated from tumor-bearing mice were added at different ratios and after 3 days of culture proliferation of CD4+ and CD8+ T cells was assessed by flow cytometry. This assay showed a dose-dependent suppression of both CD4+ and CD8+ T cells by the isolated MDSCs. Our new EasySep™ Mouse MDSC (CD11b+Gr1+) Isolation Kit offers a fast and easy method that could facilitate MDSC discoveries that impact a wide range of diseases.