Fig. 1.
Distribution of different myeloid-derived suppressor cell (MDSC) subsets in peripheral blood and tumor tissue of participants with primary glioblastoma (GBM) (A) Representative dot plots are shown to illustrate the gating strategy for the discrimination of different MDSC subsets. After removal of trash, aggregates, and dead cells by forward/side scatter gating, lymphocytes were excluded from CD45+ leukocytes, and cells with high expression of the myeloid marker CD11b were selected to exclude resident microglia or tumor-infiltrating macrophages that usually exhibit a CD11blow expression profile. Cells were then separated into a CD14high and CD14low fraction. Based on the expression of CD15, CD14low cells were further divided into CD15high, CD15int, or CD15neg cells. Similarly, CD14high cells were split into CD15pos and CD15neg cells. (B) Morphologic characteristics of different MDSC subsets in the peripheral blood of GBM participants. PBMCs were stained with CD45, CD11b, CD14, and CD15, and MDSC subsets were sorted by flow cytometry as depicted in (A). Cytospins and H&E staining were conducted. Representative pictures of different MDSC subsets are shown in (B). CD14highCD15pos cells displayed typical features of monocytes with a lobulated or reniform nucleus (usually eccentrically placed) and a grayish-blue cytoplasm. CD14lowCD15high cells revealed the typical morphology of neutrophils with segmented nuclei and pale pink cytoplasm. CD14lowCD15int cells displayed features of eosinophils with a classic bilobed nucleus and eosinophilic cytoplasm filled by numerous red granules of uniform size. CD14lowCD15neg showed big round nuclei with a small basophilic cytoplasm characteristic for immature myeloid cells. (C) Frequencies of different MDSC subsets within PBMCs and tumor cell suspension of healthy donors (PBMC-HD; n = 26) and GBM participants (PBMC-GBM, Tumor-GBM; n = 52). P values were calculated using the 2-tailed Mann-Whitney test. For detailed statistics, see Supplementary material, Table S1.