No abstract

Mesenchymal stromal cells (MSCs) are characterized by their multipotency, regenerative potential, and immunoregulatory properties. Nowadays, MSCs represent a promising cell-therapeutic option for hyperinflammatory conditions such as graft-vs-host disease following allogeneic hematopoietic stem cell transplantation. A better understanding of their biology is a prerequisite for improving their treatment efficacy.Emerging evidence suggests that immunosuppressive properties are not constitutively active in MSCs. Instead, microenvironmental inflammatory stimuli such as the cytokines interferon (IFN)-γ or tumor necrosis factor (TNF)-α license MSCs to acquire a tolerance-promoting phenotype. The immunological checkpoint molecule programmed death-ligand 1 (PD-L1) is an important regulator of T-cell responses.Binding of PD-L1 to the programmed cell death protein 1 (PD-1) receptor on T-cells suppresses their activation, proliferation, and induces apoptosis. Previous studies have revealed that cell surface expression and secretion of PD-L1 are part of the MSCs' immunomodulatory armamentarium. Here, we report that inflammatory licensing leads to an enhanced PD-L1 cell surface expression and secretion, which are both accompanied by an increased posttranslational protein N-glycosylation. These posttranslational modifications have been shown to be critical for key biological processes such as cell trafficking, receptor signaling, and immunohomeostasis. In fact, promoting N-glycosylation in MSCs yielded increased PD-L1 levels. We report for the first time that PD-L1 N-glycosylation plays a decisive role for its transport to the MSCs' cell surface and its subsequent secretion (in response to proinflammatory trigger). Our data offer insights into a novel regulatory mechanism with the potential to be exploited as a means to foster the immunosuppressive potency of human MSCs.

Tigecycline has been used to treat patients with febrile neutropenia (FN). This study aims to analyse the effectiveness of tigecycline as salvage treatment of FN. Patients records from 09/2004 to 04/2019 were reviewed. Cases were eligible if fever persisted/recurred (p/r-FN) after 3 days of second-line treatment with a carbapenem, and were divided into three groups: switch to tigecycline (TGC group), switch to other antibiotics (OAB group), and no switch (W&W group). The primary endpoint was response rate (defervescence for ≥ 7 days or at least until discharge); the key secondary endpoint was 30-day mortality rate. Two hundred cases from 176 patients (median 59 years; 53.5% men) treated were included, mostly acute myeloid leukaemias (61.0%). 45.5% of cases were in the TGC group (in combination with an anti-pseudomonal antibiotic, mostly ceftazidime [95.6%]); 35.5% were in the OAB and 19.0% in the W&W group. There was no significant difference in response rates (TGC, 73.6%; OAB, 62.0%; W&W, 78.9%; p = 0.12) or 30-day mortality rates (TGC, 7.7%; OAB, 7.0%; W&W, 5.3%; p = 0.94). Tigecycline plus an anti-pseudomonal antibiotic does not improve response or 30-day mortality rate compared to other antibiotics in patients with p/r-FN. Also, in some cases, no switch in antibiotics may be necessary at all.