Table 1.
Fundamental characteristics of MDSCs, neutrophils, and monocytes.
| PMN-MDSCs | Neutrophils | M−MDSCs | Monocytes | |
|---|---|---|---|---|
| phenotypical markers in mice | CD11b+Ly6G+Ly6Clo | CD11b+LY6G+Ly6Clo | CD11b+Ly6G–Ly6Chi | CD11b+Ly6G−Ly6Chi |
| phenotypical markers in human | CD11b+CD14−CD15+CD66b+HLA-DR– | CD11b+CD14–CD15+CD66b+ | CD11b+CD14+CD15–HLA-DR–/lo | CD11b+CD14+CD15–HLA-DR+ |
| density gradient centrifugation | low | high | low | low |
| novel markers | LOX-1 | NA | CXCR1 | NA |
| function | immunosuppression | activation | immunosuppression | activation |
| molecular characteristics | higher expression of genes involved in the cell cycle, autophagy, G-protein signaling, and CREB pathway | higher expression of NF-κB signaling and lymphotoxin-β receptor signaling, lysosomal and proteosomal protein expression | higher expression of PI3K, IL-6 and TGFβ | higher expression of genes involved in the phagocytosis, immune responses and migration |
| chemokines and receptors | lower expression of chemokine receptors CXCR1 and CXCR2 | higher expression of CXCL4 and CXCL12 and lower expression of CCL3, CCL4, and CXCL2 | higher expression of CXCR2, CXCR4, and CXCR1 | higher expression of CCL2, CXCR1, CD62L and CXCR2 |
| transcription factors | activation of STAT3, C/EBPβ and downregulation of IRF-8 | activation of RUNX1, KLF6, RELB, IRF5, and JUNB | activation of STAT3, C/EBPβ, downregulation of IRF-8 | activation of STAT1/3, C/EBPα-p42, c-Jun/JunB, VDR, IRF1/4/8, and C/EBPβ-LAP |
| biochemical characteristics | Arg-1, ROS, PGE2 | MPO, NE, defensins, cathelicidins, MMP | NO, TGFβ, PGE2, IL-10 | TNF, iNOS, IL-10, IL-6 |
Abbreviations: MDSC: myeloid-derived suppressor cell; PMN-MDSCs: polymorphonuclear MDSCs; M−MDSCs: monocytic MDSCs; LOX1: lectin-type oxidized LDL receptor 1; NO: nitric oxide; NA: not applicable; CXCR: CXC-chemokine receptor; CREB: cAMP-response element binding protein; IL-6: interleukin-6; TGF-β: transforming growth factor-β; PI3K: phosphoinositide 3-kinase; CXCL: CXC-chemokine ligand; CCL: C—C motif chemokine ligand 3; STAT: signal transducer and activator of transcription; C/EBP: CCAAT/enhancer binding protein; IRF: interferon related factor; VDR: vitamin D receptor; Arg-1: arginase 1; ROS: reactive oxygen species; PGE2: prostaglandin E2; MPO: myeloperoxidase; NE: neutrophil elastase; MMP: matrix metalloproteinase; iNOS: inducible nitric oxide synthase; TNF: tumor necrosis factor.