Myeloid-Derived Suppressor Cells: Paradoxical Roles in Infection and Immunity

Abstract

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature suppressor cells that are generated due to aberrant myelopoiesis under pathological conditions. Although MDSCs have been recognized for more than 20 years under the guise of different monikers, these particular populations of myeloid cells gained more attention recently due to their immunosuppressive properties, which halt host immune responses to growing cancers or overwhelming infections. While MDSCs may contribute to immune homeostasis after infection or tissue injury by limiting excessive inflammatory processes, their expansion may be at the expense of pathogen elimination and thus may lead to disease persistence. Therefore, MDSCs may be either damaging or obliging to the host by attenuating, for example, antitumor or anti-infectious immune responses. In this review, we recapitulate the biological and immunological aspects of MDSCs, including their generation, distribution, trafficking and the factors involved in their activation, expansion, suppressive functions, and interplay between MDSCs and regulatory T cells, with a focus on the perspectives of infection and inflammation.

Induction of Myeloid-Derived Suppressor Cells in Cryopyrin-Associated Periodic Syndromes

“…However, inflammatory Th17 cells have been reported to be significantly elevated in CAPS [8], providing a rationale to speculate on a counter-regulatory increase of regulatory immune cells in these patients. Myeloid-derived suppressor cells (MDSCs) represent a novel innate immune cell subset generated in tumor, infective, and proinflammatory microenvironments [9,10,11]. These specialized innate immune cells are characterized by their capacity to suppress T-cell responses and thereby modulate the cellular arm of the adaptive immunity [10].…”

Bystander Cells Taking Action

“…The importance of microbial virulence factors is nicely illustrated in an article by Blaschke et al [25], in which they show that cytolysins of the important bacterial pathogen Streptococcus pyogenes induce the expression of cyclooxygenase 2, resulting in proinflammatory activities. The importance of the resolution of inflammation to avoid excessive tissue damage, but also from the microbial side to avoid eradication, illustrates the dichotomy of host responses [8,10,26,27,28]. We hope that you will find this issue of Journal of Innate Immunity interesting and thought provoking!…”

On PAMPs and DAMPs

“…Marlene Ballbach and her collaborators studied how inflammsome products can induce the generation of myeloid-derived suppressor cells (MDSCs) [15]. Though MDSCs were first described more than 20 years ago, these cells have only recently attracted considerable interest [16]. In their article, the authors speculate that increased MDSC levels can be used as therapeutic targets in autoinflammatory diseases.…”