Table 3. Biochemical and molecular parameters associated with MDSC characterization.
| Class of biomarkers | Biomarker | Detection technology | Mainly found in | Reference |
|---|---|---|---|---|
| Transcription factors and apoptotic regulators | ↓ IRF8* Phospho-STAT3*cEBP/β*S100A8/9*RBPhospho-STAT5ROR/RORC1sXBP, CHOP | FC, PPTM (FC, ELI), FAELI, P, T, FAELI, FC, IHC, P, TIF, P, T, FCPTM (FC, IHC, P), FA FC, PP, T | MDSCMDSCMDSCMDSCM-MDSC>PMN-MDSCMDSCPMN-MDSCMDSC | 56,57,58,59,26,31,60,61,28†62,44,46,47 |
| Genes and molecules contributing to the immune-regulatory activity | ARG1*NOS2/NO*NOX2/ROS*PNT/RNS*VEGFPGE2PD-L1 | E, FC, IHC, P, TFC, IF, IHC, P, TE, FC, P, TPTM (IHC), E, FCFC, IHCELIFC, P, T | M-MDSC M-MDSCPMN-MDSCMDSCMDSCM-MDSCMDSC | 63,64,65,64,8,66,46,59,67,27,68,65,69,70,71,72,73 |
| Cytokines and receptors | IL-10*TGFβ*IL-4R (CD124)* | ELI, FC, TELI, FC, T, PFC, T | MDSCM-MDSCM-MDSC | 74,75,66,76,63,77 |
| Cytokines involved in MDSC development | ||||
| These cytokines are not produced by MDSC. However, they are important for the evaluation of MDSC microenvironment. | GM-CSFG-CSFIL-13IL-1 | ELI, TELI, TFCELI | MDSCPMN-MDSCM-MDSCMDSC | 21,78,79,21,79,80,63,81,22,74,75 |
E, enzyme assay; ELI, enzyme-linked immunosorbent assay; FA, functional activity (for example, DNA binding); FC, flow cytometry (including ICS, intracellular staining); IF, immunofluorescence; IHC, immunohistochemistry; IL, interleukin; MDSC, myeloid-derived suppressor cell; M-MDSC, monocytic-MDSC; P, protein detection in cell extracts or supernatants (that is, by western blot, mass spectrometry); PMN-MDSC; polymorphonuclear-MDSC; PTM, post-translational modification; T, transcript analysis (that is, by RT–PCR, RNA-seq or in situ hydridization).
It is important, wherever possible, to use cells from control mice or healthy donors as controls.
PMN-MDSCs are compared with neutrophils and M-MDSCs are compared with monocytes.
Total population of MDSCs in most of these studies was compared with Gr-1+CD11b+ cells from control mice. Characteristics described in the table are the same for MDSC and MDSC-LC.
*Parameters crucial for MDSC biology and, thus, for their identification.
†In this study Rb expression was largely compared between the groups of M-MDSC and PMN-MDSC.