Explore the vast range of titles available.

The use of chimeric antigen receptor (CAR)-engineered regulatory T cells (Tregs) has emerged as a promising strategy to promote immune tolerance. However, in conventional T cells (Tconvs), CAR expression is often associated with tonic signaling, which can induce CAR-T cell dysfunction. The extent and effects of CAR tonic signaling vary greatly according to the expression intensity and intrinsic properties of the CAR. Here, we show that the 4-1BB CSD-associated tonic signal yields a more dramatic effect in CAR-Tregs than in CAR-Tconvs with respect to activation and proliferation. Compared to CD28 CAR-Tregs, 4-1BB CAR-Tregs exhibit decreased lineage stability and reduced in vivo suppressive capacities. Transient exposure of 4-1BB CAR-Tregs to a Treg stabilizing cocktail, including an mTOR inhibitor and vitamin C, during ex vivo expansion sharply improves their in vivo function and expansion after adoptive transfer. This study demonstrates that the negative effects of 4-1BB tonic signaling in Tregs can be mitigated by transient mTOR inhibition. Chimeric antigen receptor engineering in T cells has been shown to be of great potential therapeutic benefit in a range of immune pathologies, although the functionality of such cell therapies can be limited due to tonic signalling and the induction of dysfunction. Here the authors show transient inhibition of mTOR can rescue their 41-BB-CAR-Tregs from tonic signalling-induced dysfunction.

In kidney transplant recipients, urine CXCL9 and CXCL10 (uCXCL9/10) chemokines have reached a sufficiently high level of evidence to be recommended by the European Society of Organ Transplantation for the monitoring of immune quiescence. To assess the risk of acute rejection (AR), the advantage of uCXCL9/10 is their cost-effectiveness and their high diagnostic performance. Here, we evaluated the feasibility of a next-generation immunoassay for quantifying uCXCL9/10 levels. It demonstrated high efficiency with minimal workflow and a 90-min time to result. Preanalytical studies indicated stability of uCXCL9/10 levels and analytical studies confirmed excellent linearity and precision. In a cohort of 1048 samples collected at biopsy, the results correlated significantly with ELISA quantification and were integrated into a previously validated 8-parameter urine chemokine model. The next generation immunoassay achieved an accuracy of 0.84 for AR diagnosis. This study validates this technology as a robust, locally available and unexpensive platform and marks a significant step towards the widespread implementation of uCXCL9/10, for immune quiescence monitoring. Therefore, we developed an open-access web application using uCXCL9/10 to calculate AR risk and improve clinical decision-making to perform biopsy, ushering in a new era in kidney transplantation, where personalized, data-driven care becomes the norm.

Rejection remains the main cause of premature graft loss after kidney transplantation, despite the use of potent immunosuppression. This highlights the need to better understand the composition and the cell-to-cell interactions of the alloreactive inflammatory infiltrate. Here, we performed droplet-based single-cell RNA sequencing of 35,152 transcriptomes from 16 kidney transplant biopsies with varying phenotypes and severities of rejection and without rejection, and identified cell-type specific gene expression signatures for deconvolution of bulk tissue. A specific association was identified between recipient-derived FCGR3A+ monocytes, FCGR3A +  NK cells and the severity of intragraft inflammation. Activated FCGR3A+ monocytes overexpressed CD47 and LILR genes and increased paracrine signaling pathways promoting T cell infiltration. FCGR3A +  NK cells overexpressed FCRL3 , suggesting that antibody-dependent cytotoxicity is a central mechanism of NK-cell mediated graft injury. Multiplexed immunofluorescence using 38 markers on 18 independent biopsy slides confirmed this role of FcγRIII+ NK and FcγRIII+ nonclassical monocytes in antibody-mediated rejection, with specificity to the glomerular area. These results highlight the central involvement of innate immune cells in the pathogenesis of allograft rejection and identify several potential therapeutic targets that might improve allograft longevity. Although long-term kidney allograft failure is broadly classified as T cell- or antibody-mediated, this dichotomy is not always apparent in all patients, highlighting the need for improved allograft tissue characterisation. Here, the authors use single-cell RNA sequencing and multiplex imaging for transcriptomic and spatial profiling of allograft tissue from patients experiencing different degrees of rejection severity.

Antibody-mediated rejection (ABMR) remains one of the main causes of long-term graft failure after kidney transplantation, despite the development of powerful immunosuppressive therapy. A detailed understanding of the complex interaction between recipient-derived immune cells and the allograft is therefore essential. Until recently, ABMR mechanisms were thought to be solely caused by adaptive immunity, namely, by anti-human leucocyte antigen (HLA) donor-specific antibody. However recent reports support other and/or additive mechanisms, designating monocytes/macrophages as innate immune contributors of ABMR histological lesions. In particular, in mouse models of experimental allograft rejection, monocytes/macrophages are readily able to discriminate non-self via paired immunoglobulin receptors (PIRs) and thus accelerate rejection. The human orthologs of PIRs are leukocyte immunoglobulin-like receptors (LILRs). Among those, LILRB3 has recently been reported as a potential binder of HLA class I molecules, shedding new light on LILRB3 potential as a myeloid mediator of allograft rejection. In this issue, we review the current data on the role of LILRB3 and discuss the potential mechanisms of its biological functions.

Graft endothelial cells (ECs) express donor alloantigens and encounter cytotoxic T lymphocytes (CTLs) but are generally spared during T cell–mediated rejection (TCMR), which predominantly affects epithelial structures. The mechanisms underlying this vascular immune privilege are unclear. Transcriptomics analyses and endothelial-mesenchymal transition assessments confirmed that the graft endothelium was preserved during TCMR. Coculture experiments revealed that endothelial and epithelial cells were equally susceptible to CTL-mediated lysis, ruling out cell-intrinsic protection. Intravital microscopy of murine kidney grafts and single-cell RNA-Seq of human renal allografts demonstrated that CTL interactions with ECs were transient compared with epithelial cells. This disparity was mediated by a chemotactic gradient produced by graft stromal cells, guiding CTLs away from ECs toward epithelial targets. In vitro, chemotaxis overrode T cell receptor–induced cytotoxicity, preventing endothelial damage. Finally, analysis of TCMR biopsies revealed that disruption of the chemotactic gradient correlated with endothelialitis lesions, linking its loss to vascular damage. These findings challenge the traditional view of cell-intrinsic immune privilege, proposing a cell-extrinsic mechanism, in which chemotaxis preserves graft vasculature during TCMR. This mechanism may have implications beyond transplantation, highlighting its role in maintaining vascular integrity across pathological conditions.

Elimination of apoptotic neutrophils by macrophages, a process called efferocytosis, is a critical step in the resolution of inflammation. Efferocytosis induces the reprogramming of macrophages towards a pro-resolving phenotype and triggers the secretion of pro-resolving factors. While mouse efferocytic macrophages are well-described, less is known about human efferocytic macrophages. Here, using RNA sequencing analysis of three different types of in vitro-derived human efferocytic macrophages, we observed a common modulation of mitochondrial metabolism-related genes in human M0, M1, and M2a-like macrophages, thus correlating with some previous results obtained in other non-human models. These results led us to identify for the first time some particular genes regulated in humans like PLIN5 and MTLN . We also shed light on a mitochondrial gene ( MT-RNR2) coding a secreted factor called HUMANIN. Mainly known for its antioxidant and neuroprotective effects, we found that HUMANIN was also associated with pro-resolving properties in human and mouse models. Indeed, HUMANIN was produced early during the resolution of inflammation in an acute peritonitis mouse model. Preventive HUMANIN administration in this model reduced leukocyte infiltration and pro-inflammatory cytokine secretion. These anti-inflammatory properties were accompanied by the early acquisition of a CD11b low non-efferocytic phenotype by mouse macrophages and by an enhanced expression of pro-resolving genes including Alox15 and Retnla . The ability of HUMANIN to dampen pro-inflammatory cytokine secretion was also confirmed in primary human neutrophils. Finally, HUMANIN was also detected in gingival crevicular fluids of patients suffering from periodontitis after the onset of inflammation, suggesting a role of HUMANIN in the control of inflammation. Overall, our data shed light on new aspects of efferocytosis in humans and identify the pro-resolving potential of HUMANIN. This illustrates its prospective therapeutic interest in inflammatory disorders.

This study aimed to characterize arterial dendritic cells (DCs) in polymyalgia rheumatica (PMR) and giant cell arteritis (GCA). Bulk RNA-sequencing, RT-PCR and immunofluorescence analyses were performed from temporal arteries from GCA, PMR and control patients. Public single-cell RNA-seq (scRNA-seq) data on Peripheral Blood Mononuclear Cells (PBMCs) were analyzed from three GCA and three control patients. Bulk RNA-Seq and RT-PCR analyses demonstrated a high level of expression of DC lineage markers ( CD209 ), DC maturation markers ( CD83 , CCR7 ) and chemokines associated with DC maturation in GCA arteries. The level of expression of DC lineage and DC maturation associated genes was significantly lower in PMR than in GCA arteries and similar between PMR and control arteries. GCA arteries expressed high levels of GM-CSF and IFNG mRNA. ScRNA-seq analysis of GCA PBMCs demonstrated high expression of IFNGR and CSF2R by classical monocytes and cultures of CD14 + monocytes with GM-CSF and IFN-γ were able to promote their differentiation into monocyte derived-DCs (mo-DCs). This work provides evidence that mo-DCs infiltrate GCA lesions and could be generated under the influence of GM-CSF and IFN-γ from monocytes infiltrating the arterial wall. Mo-DCs could play an important role in GCA pathogenesis and be targeted by GM-CSF and/or IFN-γ inhibitors.

In solid-organ transplantation, microRNAs (miRNAs) have emerged as key players in the regulation of allograft cells function in response to injury. To gain insight into the role of miRNAs in antibody-mediated rejection, a rejection phenotype histologically defined by microvascular inflammation, kidney allograft biopsies were subjected to miRNA but also messenger RNA (mRNA) profiling. Using a unique multistep selection process specific to the BIOMARGIN study (discovery cohort, N=86; selection cohort, N=99; validation cohort, N=298), six differentially expressed miRNAs were consistently identified: miR-139-5p (down) and miR-142-3p/150-5p/155-5p/222-3p/223-3p (up). Their expression level gradually correlated with microvascular inflammation intensity. The cell specificity of miRNAs target genes was investigated by integrating their in vivo mRNA targets with single-cell RNA sequencing from an independent allograft biopsy cohort. Endothelial-derived miR-139-5p expression correlated negatively with MHC-related genes expression. Conversely, epithelial-derived miR-222-3p overexpression was strongly associated with degraded renal electrolyte homeostasis and repressed immune-related pathways. In immune cells, miR-150-5p regulated NF-κB activation in T lymphocytes whereas miR-155-5p regulated mRNA splicing in antigen-presenting cells. Altogether, integrated omics enabled us to unravel new pathways involved in microvascular inflammation and suggests that metabolism modifications in tubular epithelial cells occur as a consequence of antibody-mediated rejection, beyond the nearby endothelial compartment.

Despite the critical role of cytokines in allograft rejection, the relation of peripheral blood cytokine profiles to clinical kidney transplant rejection has not been fully elucidated. We assessed 28 cytokines through multiplex assay in 293 blood samples from kidney transplant recipients at time of graft dysfunction. Unsupervised hierarchical clustering identified a subset of patients with increased pro-inflammatory cytokine levels. This patient subset was hallmarked by a high prevalence (75%) of donor-specific anti-human leukocyte antigen antibodies (HLA-DSA) and histological rejection (70%) and had worse graft survival compared to the group with low cytokine levels (HLA-DSA in 1.7% and rejection in 33.7%). Thirty percent of patients with high pro-inflammatory cytokine levels and HLA-DSA did not have histological rejection. Exploring the cellular origin of these cytokines, we found a corresponding expression in endothelial cells, monocytes, and natural killer cells in single-cell RNASeq data from kidney transplant biopsies. Finally, we confirmed secretion of these cytokines in HLA-DSA-mediated cross talk between endothelial cells, NK cells, and monocytes. In conclusion, blood pro-inflammatory cytokines are increased in kidney transplant patients with HLA-DSA, even in the absence of histology of rejection. These observations challenge the concept that histology is the gold standard for identification of ongoing allo-immune activation after transplantation.

In solid organ transplantation, monocytes and macrophages play a cross‐cutting role in the rejection process, irrespective of the transplanted tissue and the type of rejection. Here, we integrated multiple single‐cell assays (>150,000 cells) with a broad spectrum of blood‐derived and renal allograft‐derived cells. We observed 6 myeloid cell trajectories enriched in the allograft during rejection, ranging from circulating CD14+ monocytes to differentiated macrophages in the kidney, with one trajectory culminating in a pro‐inflammatory macrophage expressing CXCL9 and CXCL10. By analyzing over 850 biopsies using deconvolution, we report that they are absent in pre‐transplant allografts, while these CXCL10+ macrophages are the immune cells most associated with inflammation during acute rejection. Furthermore, a survival study of over 500 biopsies indicates that they increase the risk of graft loss independently of other immune cells. CXCL10+ macrophages differentiate from recipient monocytes, and we have identified 6 major genes associated with their differentiation, including LILRB2. In vitro, mimicking allogenic activation of blood monocytes via the CD47/SIRP‐a axis induced overexpression of LILRB2, suggesting that CXCL10+ macrophages are activated by this pathway. Finally, we show that macrophages overexpressing LILRB2 induce the proliferation of autologous T lymphocytes. Altogether, the present study provides further insight into the pro‐inflammatory axes of recipient‐derived monocytes/macrophages, and suggests LILRB2 as a therapeutic target. This study uncovers a recipient‐derived monocyte‐to‐macrophage trajectory that drives inflammation during kidney transplant rejection. Using over 150 000 single‐cell profiles and more than 850 biopsies, the authors identify CXCL10+ macrophages as key predictors of graft loss. They reveal LILRB2 as a regulator of their differentiation and activation, suggesting a promising therapeutic target.