Journal of Leukocyte Biology最新文献

Antimicrobial resistance is an increasing worldwide public health burden that threatens to make existent antimicrobials obsolete. An important mechanism of antimicrobial resistance is the overexpression of efflux pumps, which reduce the intracellular concentration of antimicrobials. TolC is the outer membrane protein of an efflux pump that has gained attention as a therapeutic target. Little is known about the immune response against TolC. Here we evaluated the immune response against TolC from Escherichia coli. TolC in silico epitope prediction showed several residues that could bind to human antibodies, and we showed that human plasma presented higher titers of anti-TolC IgG and IgA, than IgM. E. coli recombinant TolC protein stimulated macrophages in vitro to produce nitric oxide, as well as IL-6 and TNF-α, assessed by Griess assay and ELISA, respectively. Immunization of mice with TolC intraperitoneally and an in vitro re-stimulation led to increased T cell proliferation and IFNγ production, evaluated by flow cytometry and ELISA, respectively. TolC mouse immunization stimulated anti-TolC IgM and IgG production, with higher levels of IgG1 and IgG2, amongst the IgG subclasses. Anti-TolC murine antibodies could bind to live E. coli and increase bacterial uptake and elimination by macrophages in vitro. Intraperitoneal or intranasal, but not oral, immunizations with inactivated E. coli also led to anti-TolC antibody production. Finally, TolC immunization increased mouse survival rates to antimicrobial-sensitive or resistant E. coli infection. Our results showed that TolC is immunogenic, leading to the production of protective antibodies against E. coli, reinforcing its value as a therapeutic target.

Intravenously administered perfluorocarbon nanoemulsion (PFC) are taken up by phagocytic immune cells which enables the non-invasive visualization of inflammatory hot spots by combined 1H/19F magnetic resonance imaging (MRI). However, little is known about the influence of inflammatory stimuli on cellular uptake and biodistribution of PFCs. Here, we systematically investigated the impact of inflammation induced by subcutaneous implantation of Matrigel/lipopolysaccharide (Matrigel/LPS) or myocardial infarction (MI; 50 minutes ischemia reperfusion) on PFC-uptake and biodistribution in C57BL/6J mice. We detected strong 19F signals in Matrigel/LPS plugs and infarcted hearts, which were completely absent in controls. Cellular uptake of PFCs was increased in neutrophils isolated from the blood and Matrigel/LPS plugs, whereas uptake by monocytes was only slightly elevated. In contrast, MI caused only a moderate early increase of PFC-uptake in monocytes and neutrophils. Interestingly, the inflammatory model did also affect the biodistribution of the PFCs. The blood half-life of PFCs was slightly increased after Matrigel/LPS implantation, whereas it was reduced after MI. Compared to controls, the 19F signal of the liver was significantly stronger in Matrigel/LPS, but not in MI animals. Interestingly, stimulation of primary immune cells and RAW264.7 macrophages with LPS had no effect on PFC-uptake, whereas CRP-incubation elevated internalization of PFCs at least in RAW264.7 cells. In conclusion, we show that the cellular PFC-uptake can differ between individual inflammatory conditions. This is an important aspect that has to be considered for the proper interpretation of 1H/19F MRI data obtained from inflammatory hot spots.

Prognostic significance of soluble immune checkpoint molecule TIM-3 and its ligands in the plasma has been illustrated in various solid tumors, but such study in newly diagnosed acute myeloid leukemia (AML) remains absent. Soluble TIM-3, Gal-9 and CEACAM1 levels in the bone marrow plasma samples collected from 90 adult AML patients at diagnosis and 12 healthy donors were measured by enzyme-linked immunosorbent assays (ELISA), and 16 AML patients were simultaneously tested cell membrane TIM-3 expression by multi-color flow cytometry. AML patients had significantly elevated soluble TIM-3 levels and similar soluble Gal-9 and CEACAM1 levels compared with healthy donors (p = 0.0003, 0.26 and 0.96). In the whole cohort, high soluble TIM-3 level was the sole independent adverse prognostic factor for relapse-free survival (RFS) (p = 0.0060), and it together with adverse ELN genetic risk were independent poor prognostic factors for event-free survival (EFS) (p = 0.0030 and 0.0040); High soluble CEACAM1 level were significantly related to lower RFS (p = 0.028). In addition, high soluble Gal-9 level had significant association with lower RFS in patients receiving allogeneic hematopoietic stem cell transplantation (allo-HSCT) at the first complete remission (p = 0.037). Furthermore, soluble TIM-3 level tended to have positive correlation with the percentage of non-blast myeloid TIM-3+ cells in nucleated cells in AML (r = 0.48, p = 0.073). Therefore, the high soluble TIM-3 level in the diagnostic BM plasma predicted poor outcome in adult AML patients, and high sGal-9 level was associated with relapse after allo-HSCT.

Dysfunctional phagocytic clearance of β-amyloid (Aβ) in microglia and peripheral macrophages/monocytes has been implicated in Alzheimer's disease (AD), but the mechanisms underlying this dysfunction are not yet well understood. In this study, we examined the role of glia maturation factor-γ (GMFG), an actin-disassembly protein that is highly expressed in immune cells, in macrophage Aβ phagocytosis and in regulating scavenger receptor AI (SR-AI), a cell-surface receptor that has previously been implicated in Aβ clearance. GMFG knockdown increased phagocytosis of Aβ42 in BMDMs and RAW264.7 murine macrophages, while GMFG overexpression reduced Aβ42 uptake in these cells. Blocking with anti-SR-AI antibodies inhibited Aβ42 uptake in GMFG-knockdown cells, establishing a role for SR-AI in Aβ42 phagocytosis. GMFG knockdown increased SR-AI protein expression under both basal conditions and in response to Aβ42 treatment via both the transcriptional and post-transcriptional level in RAW264.7 macrophages. GMFG knockdown modulated Aβ42-induced K48-linked and K63-polyubiquitination of SR-AI, the phosphorylation of SR-AI and JNK, suggesting that GMFG plays a role for intracellular signaling in the SR-AI-mediated uptake of Aβ. Further, GMFG-knockdown cells displayed increased levels of the transcriptional factor MafB, and silencing of MafB in these cells reduced their SR-AI expression. Finally, GMFG was found to interact with the nuclear pore complex component RanBP2, and silencing of RanBP2 in GMFG-knockdown cells reduced their SR-AI expression. Collectively, these data support the role of GMFG as a novel regulator of SR-AI in macrophage Aβ phagocytosis, and may provide insight into therapeutic approaches to potentially slow or prevent the progression of AD.

Neutrophils interact with Leishmania when the sandfly vector inoculates these parasites in the host with saliva and promastigotes-derived extracellular vesicles (EVs). It has been shown that this co-injection induces inflammation and exacerbates leishmaniasis lesions. EVs are a heterogeneous group of vesicles released by cells that play a crucial role in intercellular communication. Neutrophils are among the first cells to interact with the parasites and release neutrophil extracellular traps (NETs) that ensnare and kill the promastigotes. Here, we show that Leishmania amazonensis EVs induce NET formation and identify molecular mechanisms involved. We showed the requirement of neutrophils' Toll-like receptors (TLRs) for EVs-induced NET. EVs carrying the virulence factors lipophosphoglycan (LPG) and the zinc metalloproteases were endocytosed by some neutrophils and snared by NETs. EVs-induced NET formation required reactive oxygen species, myeloperoxidase, elastase, peptidyl arginine deiminase (PAD), and Ca++. The proteomic analysis of the EVs cargo revealed 1,189 proteins; the 100 most abundant identified comprised some known Leishmania virulent factors. Importantly, L. amazonensis EVs-induced NETs lead to the killing of promastigotes and could participate in the exacerbated inflammatory response induced by the EVs, which may play a role in the pathogenesis process.

Chemerin is a distant member of the cystatin protein family, initially discovered as a chemotactic factor and subsequently also reported to act as adipokine and angiogenetic factor. The biological activity of chemerin is regulated at different levels, such as gene expression, protein processing and interaction with both signaling and nonsignaling receptors. Chemerin is mostly produced by stromal cells, such as adipocytes, fibroblasts, epithelial and endothelial cells and circulates in almost all human tissues as a zymogen that needs to be proteolytically activated to exert its biological functions. At the receptor level, chemerin binds a G protein-coupled seven transmembrane domain receptor Chemerin1 (also named ChemR23 and CMKLR1), mostly expressed by innate immune cells, such as macrophages, dendritic cells and NK cells and by border cells. In addition, chemerin may bind GPR1, a weak signaling receptor, and CCRL2, a nonsignaling receptor expressed by barrier cells, such as endothelial and epithelial cells, able to regulate leukocytes migration by multiple mechanisms. The aim of this review is to summarize the contribution of chemerin in the regulation of immune responses.

Pathogenic CD8+T cells play an essential role in neuroinflammation and neural injury, which leads to the progression of inflammatory neurological disorders. Thus, blocking the infiltration of CD8+T cells is necessary for the treatment of neuroinflammatory diseases. Our previous study demonstrated that Astragalus polysaccharides (APS) could significantly reduce the infiltration of CD8+T cells in experimental autoimmune encephalomyelitis (EAE) mice. However, the mechanism by which APS suppress CD8+T cell infiltration remains elusive. In this study, we further found that APS could reduce the CD8+T cell infiltration in EAE and lipopolysaccharide (LPS)-induced neuroinflammatory model. Furthermore, we established the mouse brain endothelial cell (bEnd.3) inflammatory injury model by interleukin-1β (IL-1β) or LPS in vitro. The results showed that APS treatment downregulated the expression of vascular cell adhesion molecule1 (VCAM1) to decrease the adhesion of CD8+T cells to bEnd.3 cells. APS also upregulated the expression of zonula occluden-1 (ZO-1) and vascular endothelial cadherin (VE-cadherin) to reduce the trans-endothelial migration of CD8+T cells. The PI3K/AKT signaling pathway might mediate this protective effect of APS on bEnd.3 cells against inflammatory injury. In addition, we demonstrated the protective effect of APS on the integrity of brain endothelial cells in an LPS-induced neuroinflammatory model. In summary, our results indicate that APS can reduce peripheral CD8+T cell infiltration via enhancing the barrier function of brain endothelial cells, it may be a potential for the prevention of neuroinflammatory diseases.