Editorial: Two MDSC faces in obesity: Correcting metabolic dysfunctions but promoting tumor development

Involvement of impaired CD8+ mucosal-associated invariant T cells and myeloid-derived suppressor cells in polycystic ovary syndrome

BACKGROUND

Immune dysfunction is one of the mechanisms to promote polycystic ovary syndrome (PCOS). Various immune cells have been reported to be involved in the development of PCOS. Meanwhile, the disturbance of metabolism is closely related to PCOS. The aim of this study is to explore the association of mucosal-associated invariant T (MAIT) cells and myeloid-derived suppressor cells (MDSCs) with the metabolic dysfunction in PCOS.

METHODS

68 PCOS patients and 40 controls were recruited in this study and we collected the peripheral blood of participants' during their follicular phase. The frequencies of MAIT cells and MDSCs were determined by flow cytometry after being stained with different monoclonal antibodies. And the concentrations of cytokines were determined by ELISA.

RESULTS

Compared to controls with normal metabolism, the frequency of MDSCs, CD8⁺MAIT cells and CD38⁺CD8⁺MAIT cells were significantly decreased in PCOS patients with normal metabolism, however, proportion of CD4⁺MAIT cells exhibited a noticeable increase. Similar results of CD8⁺MAIT, CD38⁺CD8⁺MAIT cells and reduced expression of IL-17 were observed in PCOS patients with metabolic dysfunction as compared to controls with metabolic disorders. PCOS patients with excessive testosterone levels displayed significantly decreased levels of CD8⁺MAIT, CD38⁺CD8⁺MAIT cells, MDSCs and Mo-MDSCs as compared to PCOS patients with normal testosterone concentrations. PCOS patients with abnormal weight showed a lower level and activation of CD8⁺MAIT cells. On the contrary, they displayed an enrichment of CD4⁺MAIT cells. PCOS patients with glucose metabolic disorder displayed a remarkable dysregulation of MDSCs and Mo-MDSCs. MDSCs were positively correlated with MAIT cells. Negative correlations between the frequency of CD8⁺MAIT cells, CD38⁺CD8⁺MAIT cells and body mass index were revealed. CD4⁺MAIT cells positively correlated with BMI. Mo-MDSCs were found to be negatively related to the levels of 2hour plasma glucose and HOMA-IR index.

CONCLUSION

The impairment of CD8+MAIT cells and MDSCs is involved in the metabolic dysfunction of PCOS.

The Yin and Yang of Myeloid Derived Suppressor Cells

In recent years, most of our knowledge about myeloid derived suppressor cells (MDSCs) has come from cancer studies, which depicts Yin side of MDSCs. In cancer, inherent immunosuppressive action of MDSCs favors tumor progression by inhibiting antitumor immune response. However, recently Yang side of MDSCs has also been worked out and suggests the role in maintenance of homeostasis during non-cancer situations like pregnancy, obesity, diabetes, and autoimmune disorders. Continued work in this area has armored the biological importance of these cells as master regulators of immune system and prompted scientists all over the world to look from a different perspective. Therefore, explicating Yin and Yang arms of MDSCs is obligatory to use it as a double edged sword in a much smarter way. This review is an attempt toward presenting a synergistic coalition of all the facts and controversies that exist in understanding MDSCs, bring them on the same platform and approach their "Yin and Yang" nature in a more comprehensive and coherent manner.