<p>Paradoxes in the Phenotype, Frequency and Roles of Myeloid-Derived Suppressor Cells During HIV Infection</p>

Abstract

Myeloid-derived suppressor cells (MDSCs) are heterogeneous groups of pathologically activated myeloid cells with potent immunosuppressive function. Due to their role in negatively regulating the immune system, MDSCs have been strongly correlated with disease progression during HIV. However, findings vary considerably between studies. The dominant phenotype of MDSC subsets during HIV is not well ascertained. Moreover, there is no clear understanding on the clinical significance of MDSCs during HIV infection. The existing evidences showed the double-sided roles of MDSCs in HIV. On the one hand, MDSCs are linked to deleterious effects during HIV infection as they inhibit proliferation of protective T cell response. On the other hand, the immunosuppressive abilities of MDSCs were shown to be beneficial in curbing the damaging effects of persistent immune activation associated with chronic HIV infection. Therefore, this review aimed to describe the differences in the existing literatures pertaining to the phenotype, frequency and roles of MDSCs during HIV infection.

Protective and pathological roles of regulatory immune cells in human cytomegalovirus infection following hematopoietic stem cell transplantation

“…Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of activated myeloid regulatory cells, including monocytes, macrophages, dendritic cells, and neutrophils, that are induced and recruited to the site of inflammation. 47 Based on their surface markers, MDSCs can be divided into two major groups: monocytic MDSCs (Mo-MDSCs), which express CD14, and granulocytic MDSCs (GR-MDSC)-which express granulocytic markers like CD66b and/or CD15. 48,49 These cells suppress both innate and adaptive immune responses via a multitude of mechanisms and help resolve inflammation.…”

“…64 In viral infections where MDSCs decrease protective antiviral responses, immune therapies aimed at decreasing MDSC numbers or function may aid in viral clearance and prevent chronic infection; however, increasing MDSC numbers may prove beneficial in viruses that cause severe immunopathology such as HCMV. 47,61 Importantly, the pathogenesis of disease associated with acute HCMV infection is directly linked to lytic virus replication, virus-induced cytopathology or could be a result of the host's immune reaction towards virus-infected cells. 65 In this context MDSCs by regulatory mechanisms, might have beneficial roles in preventing cytopathic effects of acute HCMV infection.…”

“…Further, it has been demonstrated that MDSCs are capable of expanding Tregs in vivo by the production of soluble factors such as TGF‐β and IL‐10 64 . In viral infections where MDSCs decrease protective antiviral responses, immune therapies aimed at decreasing MDSC numbers or function may aid in viral clearance and prevent chronic infection; however, increasing MDSC numbers may prove beneficial in viruses that cause severe immunopathology such as HCMV 47,61 . Importantly, the pathogenesis of disease associated with acute HCMV infection is directly linked to lytic virus replication, virus‐induced cytopathology or could be a result of the host's immune reaction towards virus‐infected cells 65 .…”