Functional Transition of CD11b+CD33+HLA-DR-/lowCD14- G-MDSC: Immunostimulation to Immunosuppression Post Allo-HSCT

The prediction of acute graft-versus-host disease (aGvHD) post allogeneic hematopoietic stem cell transplantation (allo-HSCT) is critical for treatment decisions. The granulocytic myeloid-derived suppressor cells (G-MDSCs) show a fast recovery post-transplantation and constituted the major part of peripheral blood in the early phase after allo-HSCT. These cells were previously believed to exhibit immunosuppressive properties. However, they also promote inflammation under specific conditions. Thus, we conducted a comprehensive study of G-MDSCs from 82 patients after allo-HSCT within 90 days to elucidate the role of them in post-transplantation immunity. Strikingly, our results showed that G-MDSCs promoted inflammation in the early-stage, by facilitating cytokine secretion and proliferation of T cells, as well as their differentiation into pro-inflammatory T helper subsets. At day 28, patients with a higher number of G-MDSCs exhibited an increased risk of developing aGvHD. Besides, adoptive transfer of G-MDSCs from patients into humanized mice exacerbated aGvHD. However, at day 90, G-MDSCs showed immunosuppressive features, characterized by upregulated expression of indoleamine 2,3-dioxygenase gene and interleukin-10 secretion, coupled with the inhibition of T cell proliferation. Furthermore, transcriptional analysis of G-MDSCs at day 28 and day 90 revealed that a total of 1445 genes were differentially expressed. Genes linked to the endoplasmic reticulum stress were upregulated in patients without aGvHD. After the genetic overlap analysis, DERL1 may be the hub-gene. Our findings elucidate the alteration in the immune characteristics of G-MDSCs within the first 90 days post allo-HSCT. Moreover, the quantity of G-MDSCs at day 28 could serve as a predictive indicator for aGvHD.