Hi everyone,
As we know, CD11b+Ly6g+Ly6cint cells are recognized as PMN-MDSCs (immature neutrophils) in mouse. However, ly6g is expressed on neutrophils as well. The question is how can we distinguish the function of PMN-MDSCs from neutrophils, especially when we use anti-ly6g antibody to deplete ly6g+ cells in vivo, or isolate ly6g+ cells for in vitro functonal experiments with anti-Ly-6G MicroBeads (Miltenyi Biotec) . It seems that most published literatures have not clarified such problems.
Are there any other specific markers for PMN-MDSCs and neutrophils?
Thanks!
I used to have the same issue. As far as I know, there are none. I used to base my gating on the paper linked below. It states that "Presently, the only method allowing for separation of neutrophils from PMN-MDSC is gradient centrifugation using 1.077 g l−1 density (standard Ficoll gradient used for the isolation of mononuclear cells). PMN-MDSC are enriched in low density (mononuclear cell fraction), whereas neutrophils are high-density cells" and goes on to mention the problems associated with this strategy. And obviosuly this won't work when doing in vivo depletions.
https://www.nature.com/articles/ncomms12150
Hi Chuangzhong,
Unfortunately, there really isn't a good surface marker to distinguish PMN-MDSCs from neutrophils. I've heard many professors at Penn and Wistar express that people have searched high and low for a simpler way to do so. The distinction has to be made functionally, in the manners outlined by Drs. Bronte and Gabrilovich in the cited paper (and in the numerous other papers published by this duo). The most definitive would be done through ELISPOT (e.g. adding the suspected Ly6G+ cells in with peptide-pulsed DCs and T-cells) or through CSFE-style analysis (combining suspected Ly6G+ cells with CSFE-stained naive T cells in the presence of CD3/CD28 Dynabeads). Biochemical analysis may be possible as well (IRF-8, p-STAT-3, NOX), but you'd have to see how many papers have been published using these indicators alone.
Happy Hunting,
Richard
Thanks Julie and Richard!
A recent work from Prof. Gabrilovich's Lab showed that FATP2 (Fatty acid transport protein 2) played an important role in mediating the immunosuppressive activity of PMN-MDSC (paper linked below) . Of note, the WB result from Extended Data Fig. 2a-b showed that FATP2 was expressed in tumor bearing PMN-MDSC but not ctrl normal PMN. So, i suppose FATP2 may be a potential marker to identify PMN-MDSC from neutrophils.
What do you think? Richard William Davis , Julie Joseph .
https://www.nature.com/articles/s41586-019-1118-2.pdf
Chuangzhong Deng, thanks for the link. I hadn't come across that paper. Although I am no longer working in the field, it is nice to know. I am assuming it is expressed on cell surface. If you could find an antibody against FATP2, you could use it to sort out PMN-MDSCs from PMNs after isolation with Ly6G microbeads. In vivo depletions might need some work depending on the expression levels of FATP2 on cells.