Cell shape sensing licenses dendritic cells for homeostatic migration to lymph nodes.

Immune cells experience large cell shape changes during environmental patrolling because of the physical constraints that they encounter while migrating through tissues. These cells can adapt to such deformation events using dedicated shape-sensing pathways. However, how shape sensing affects immune cell function is mostly unknown. Here, we identify a shape-sensing mechanism that increases the expression of the chemokine receptor CCR7 and guides dendritic cell migration from peripheral tissues to lymph nodes at steady state. This mechanism relies on the lipid metabolism enzyme cPLA2, requires nuclear envelope tensioning and is finely tuned by the ARP2/3 actin nucleation complex. We also show that this shape-sensing axis reprograms dendritic cell transcription by activating an IKKß-NF-κB-dependent pathway known to control their tolerogenic potential. These results indicate that cell shape changes experienced by immune cells can define their migratory behavior and immunoregulatory properties and reveal a contribution of the physical properties of tissues to adaptive immunity.

A Phase I/IIa study of autologous tolerogenic dendritic cells immunotherapy in kidney transplant recipients.

Kidney transplant survival is shortened by chronic rejection and side effects of standard immunosuppressive drugs. Cell-based immunotherapy with tolerogenic dendritic cells has long been recognized as a promising approach to reduce general immunosuppression. Published trials report the safety and the absence of therapy-related adverse reactions in patients treated with tolerogenic dendritic cells suffering from several inflammatory diseases. Here, we present the first phase I clinical trial results using human autologous tolerogenic dendritic cells (ATDC) in kidney transplantation. Eight patients received ATDC the day before transplantation in conjunction with standard steroids, mycophenolate mofetil and tacrolimus immunosuppression with an option to taper mycophenolate mofetil. ATDC preparations were manufactured in a Good Manufacturing Practice-compliant facility and fulfilled cell count, viability, purity and identity criteria for release. A control group of nine patients received the same standard immunosuppression, except basiliximab induction replaced ATDC therapy and mycophenolate tapering was not allowed. During the three-year follow-up, no deaths occurred and there was 100% graft survival. No significant increase of adverse events was associated with ATDC infusion. Episodes of rejection were observed in two patients from the ATDC group and one patient from the control group. However, all rejections were successfully treated by glucocorticoids. Mycophenolate was successfully reduced/stopped in five patients from the ATDC group, allowing tacrolimus monotherapy for two of them. Regarding immune monitoring, reduced CD8 T cell activation markers and increased Foxp3 expression were observed in the ATDC group. Thus, our results demonstrate ATDC administration safety in kidney-transplant recipients.

Dendritic Cells Require TMEM176A/B Ion Channels for Optimal MHC Class II Antigen Presentation to Naive CD4+ T Cells.

Intracellular ion fluxes emerge as critical actors of immunoregulation but still remain poorly explored. In this study, we investigated the role of the redundant cation channels TMEM176A and TMEM176B (TMEM176A/B) in retinoic acid-related orphan receptor γt+ cells and conventional dendritic cells (DCs) using germline and conditional double knockout mice. Although Tmem176a/b appeared surprisingly dispensable for the protective function of Th17 and group 3 innate lymphoid cells in the intestinal mucosa, we found that they were required in conventional DCs for optimal Ag processing and presentation to CD4+ T cells. Using a real-time imaging method, we show that TMEM176A/B accumulate in dynamic post-Golgi vesicles preferentially linked to the late endolysosomal system and strongly colocalize with HLA-DM. Taken together, our results suggest that TMEM176A/B ion channels play a direct role in the MHC class II compartment of DCs for the fine regulation of Ag presentation and naive CD4+ T cell priming.

Regulatory cell therapy in kidney transplantation (The ONE Study): a harmonised design and analysis of seven non-randomised, single-arm, phase 1/2A trials.

BACKGROUND: Use of cell-based medicinal products (CBMPs) represents a state-of-the-art approach for reducing general immunosuppression in organ transplantation. We tested multiple regulatory CBMPs in kidney transplant trials to establish the safety of regulatory CBMPs when combined with reduced immunosuppressive treatment. METHODS: The ONE Study consisted of seven investigator-led, single-arm trials done internationally at eight hospitals in France, Germany, Italy, the UK, and the USA (60 week follow-up). Included patients were living-donor kidney transplant recipients aged 18 years and older. The reference group trial (RGT) was a standard-of-care group given basiliximab, tapered steroids, mycophenolate mofetil, and tacrolimus. Six non-randomised phase 1/2A cell therapy group (CTG) trials were pooled and analysed, in which patients received one of six CBMPs containing regulatory T cells, dendritic cells, or macrophages; patient selection and immunosuppression mirrored the RGT, except basiliximab induction was substituted with CBMPs and mycophenolate mofetil tapering was allowed. None of the trials were randomised and none of the individuals involved were masked. The primary endpoint was biopsy-confirmed acute rejection (BCAR) within 60 weeks after transplantation; adverse event coding was centralised. The RTG and CTG trials are registered with ClinicalTrials.gov, NCT01656135, NCT02252055, NCT02085629, NCT02244801, NCT02371434, NCT02129881, and NCT02091232. FINDINGS: The seven trials took place between Dec 11, 2012, and Nov 14, 2018. Of 782 patients assessed for eligibility, 130 (17%) patients were enrolled and 104 were treated and included in the analysis. The 66 patients who were treated in the RGT were 73% male and had a median age of 47 years. The 38 patients who were treated across six CTG trials were 71% male and had a median age of 45 years. Standard-of-care immunosuppression in the recipients in the RGT resulted in a 12% BCAR rate (expected range 3·2-18·0). The overall BCAR rate for the six parallel CTG trials was 16%. 15 (40%) patients given CBMPs were successfully weaned from mycophenolate mofetil and maintained on tacrolimus monotherapy. Combined adverse event data and BCAR episodes from all six CTG trials revealed no safety concerns when compared with the RGT. Fewer episodes of infections were registered in CTG trials versus the RGT. INTERPRETATION: Regulatory cell therapy is achievable and safe in living-donor kidney transplant recipients, and is associated with fewer infectious complications, but similar rejection rates in the first year. Therefore, immune cell therapy is a potentially useful therapeutic approach in recipients of kidney transplant to minimise the burden of general immunosuppression. FUNDING: The 7th EU Framework Programme.

Regulatory Macrophages and Tolerogenic Dendritic Cells in Myeloid Regulatory Cell-Based Therapies.

Myeloid regulatory cell-based therapy has been shown to be a promising cell-based medicinal approach in organ transplantation and for the treatment of autoimmune diseases, such as type 1 diabetes, rheumatoid arthritis, Crohn's disease and multiple sclerosis. Dendritic cells (DCs) are the most efficient antigen-presenting cells and can naturally acquire tolerogenic properties through a variety of differentiation signals and stimuli. Several subtypes of DCs have been generated using additional agents, including vitamin D3, rapamycin and dexamethasone, or immunosuppressive cytokines, such as interleukin-10 (IL-10) and transforming growth factor-beta (TGF-ß). These cells have been extensively studied in animals and humans to develop clinical-grade tolerogenic (tol)DCs. Regulatory macrophages (Mregs) are another type of protective myeloid cell that provide a tolerogenic environment, and have mainly been studied within the context of research on organ transplantation. This review aims to thoroughly describe the ex vivo generation of tolDCs and Mregs, their mechanism of action, as well as their therapeutic application and assessment in human clinical trials.

Development and comparative validation of genomic-driven PCR-based assays to detect Xanthomonas citri pv. citri in citrus plants.

BACKGROUND: Asiatic Citrus Canker, caused by Xanthomonas citri pv. citri, severely impacts citrus production worldwide and hampers international trade. Considerable regulatory procedures have been implemented to prevent the introduction and establishment of X. citri pv. citri into areas where it is not present. The effectiveness of this surveillance largely relies on the availability of specific and sensitive detection protocols. Although several PCR- or real-time PCR-based methods are available, most of them showed analytical specificity issues. Therefore, we developed new conventional and real-time quantitative PCR assays, which target a region identified by comparative genomic analyses, and compared them to existing protocols. RESULTS: Our assays target the X. citri pv. citri XAC1051 gene that encodes for a putative transmembrane protein. The real-time PCR assay includes an internal plant control (5.8S rDNA) for validating the assay in the absence of target amplification. A receiver-operating characteristic approach was used in order to determine a reliable cycle cut-off for providing accurate qualitative results. Repeatability, reproducibility and transferability between real-time devices were demonstrated for this duplex qPCR assay (XAC1051-2qPCR). When challenged with an extensive collection of target and non-target strains, both assays displayed a high analytical sensitivity and specificity performance: LOD95% = 754 CFU ml- 1 (15 cells per reaction), 100% inclusivity, 97.2% exclusivity for XAC1051-2qPCR; LOD95% = 5234 CFU ml- 1 (105 cells per reaction), 100% exclusivity and inclusivity for the conventional PCR. Both assays can detect the target from naturally infected citrus fruit. Interestingly, XAC1051-2qPCR detected X. citri pv. citri from herbarium citrus samples. The new PCR-based assays displayed enhanced analytical sensitivity and specificity when compared with previously published PCR and real-time qPCR assays. CONCLUSIONS: We developed new valuable detection assays useful for routine diagnostics and surveillance of X. citri pv. citri in citrus material. Their reliability was evidenced through numerous trials on a wide range of bacterial strains and plant samples. Successful detection of the pathogen was achieved from both artificially and naturally infected plants, as well as from citrus herbarium samples, suggesting that these assays will have positive impact both for future applied and academic research on this bacterium.

Role of myeloid regulatory cells (MRCs) in maintaining tissue homeostasis and promoting tolerance in autoimmunity, inflammatory disease and transplantation.

Myeloid cells play a pivotal role in regulating innate and adaptive immune responses. In inflammation, autoimmunity, and after transplantation, myeloid cells have contrasting roles: on the one hand they initiate the immune response, promoting activation and expansion of effector T-cells, and on the other, they counter-regulate inflammation, maintain tissue homeostasis, and promote tolerance. The latter activities are mediated by several myeloid cells including polymorphonuclear neutrophils, macrophages, myeloid-derived suppressor cells, and dendritic cells. Since these cells have been associated with immune suppression and tolerance, they will be further referred to as myeloid regulatory cells (MRCs). In recent years, MRCs have emerged as a therapeutic target or have been regarded as a potential cellular therapeutic product for tolerance induction. However, several open questions must be addressed to enable the therapeutic application of MRCs including: how do they function at the site of inflammation, how to best target these cells to modulate their activities, and how to isolate or to generate pure populations for adoptive cell therapies. In this review, we will give an overview of the current knowledge on MRCs in inflammation, autoimmunity, and transplantation. We will discuss current strategies to target MRCs and to exploit their tolerogenic potential as a cell-based therapy.

Tolerogenic dendritic cell therapy in organ transplantation.

Although the occurrence of acute rejection was significantly reduced and the allograft survival at 1 year was massively improved by the development of pharmacological immunosuppressive drugs, little progress has been made regarding long-term graft survival. Cell therapy appears to be an innovative and promising strategy to minimize the use of immunosuppression in transplantation and consequently increases long-term graft survival. The strength of cell therapy is that it will induce graft-specific tolerance and not a general immunosuppression of the patients. Several candidates, such as tolerogenic dendritic cells, have been gaining interest as an efficient means of promoting antigen-specific tolerance over recent years. Studies performed in rodent models have demonstrated the feasibility and efficacy of tolerogenic dendritic cells for the induction of tolerance in transplantation. In parallel, protocols to generate human tolerogenic dendritic cells in vitro have been defined, and some phase I clinical trials in autoimmune diseases have been recently performed to evaluate the safety of tolerogenic dendritic cell therapy. In this review, we will focus on the potential therapeutic interest of these cells in transplantation as well as their generation and characterization in humans. Finally, we will describe our current clinical trial using autologous tolerogenic dendritic cells in transplantation.

Transitional-2 B cells acquire regulatory function during tolerance induction and contribute to allograft survival.

In humans, tolerance to renal transplants has been associated with alterations in B-cell gene transcription and maintenance of the numbers of circulating transitional B cells. Here, we use a mouse model of transplantation tolerance to investigate the contribution of B cells to allograft survival. We demonstrate that transfer of B cells from mice rendered tolerant to MHC class I mismatched skin grafts can prolong graft survival in a dose-dependent and antigen-specific manner to a degree similar to that afforded by graft-specific regulatory T (Treg) cells. Tolerance in this model was associated with an increase in transitional-2 (T2) B cells. Only T2 B cells from tolerized mice, not naïve T2 nor alloantigen experienced T2, were capable of prolonging skin allograft survival, and suppressing T-cell activation. Tolerized T2 B cells expressed lower levels of CD86, increased TIM-1, and demonstrated a preferential survival in vivo. Furthermore, we demonstrate a synergistic effect between tolerized B cells and graft-specific Treg cells. IL-10 production by T2 B cells did not contribute to tolerance, as shown by transfer of B cells from IL-10(-/-) mice. These results suggest that T2 B cells in tolerant patients may include a population of regulatory B cells that directly inhibit graft rejection.

Tolerogenic Donor-Derived Dendritic Cells Risk Sensitization In Vivo owing to Processing and Presentation by Recipient APCs.

Modification of allogeneic dendritic cells (DCs) through drug treatment results in DCs with in vitro hallmarks of tolerogenicity. Despite these observations, using murine MHC-mismatched skin and heart transplant models, donor-derived drug-modified DCs not only failed to induce tolerance but also accelerated graft rejection. The latter was inhibited by injecting the recipient with anti-CD8 Ab, which removed both CD8(+) T cells and CD8(+) DCs. The discrepancy between in vitro and in vivo data could be explained, partly, by the presentation of drug-modified donor DC MHC alloantigens by recipient APCs and activation of recipient T cells with indirect allospecificity, leading to the induction of alloantibodies. Furthermore, allogeneic MHC molecules expressed by drug-treated DCs were rapidly processed and presented in peptide form by recipient APCs in vivo within hours of DC injection. Using TCR-transgenic T cells, Ag presentation of injected OVA-pulsed DCs was detectable for ≤ 3 d, whereas indirect presentation of MHC alloantigen by recipient APCs led to activation of T cells within 14 h and was partially inhibited by reducing the numbers of CD8(+) DCs in vivo. In support of this observation when mice lacking CD8(+) DCs were pretreated with drug-modified DCs prior to transplantation, skin graft rejection kinetics were similar to those in non-DC-treated controls. Of interest, when the same mice were treated with anti-CD40L blockade plus drug-modified DCs, skin graft survival was prolonged, suggesting endogenous DCs were responsible for T cell priming. Altogether, these findings highlight the risks and limitations of negative vaccination using alloantigen-bearing "tolerogenic" DCs.

68 Ga-DOTATOC Pictorial Essay of Various Recurrent Meningiomas Rejected for Treatment With 177 Lu-DOTATATE : Is There a Place for Another Theranostic Examination?

ABSTRACT: We report the cases of 4 patients treated for recurrent meningiomas of various grades. Pretreatment 68 Ga-DOTATOC PET/CT was performed prior to screening for vectorized internal radiotherapy with 177 Lu-DOTATATE or prior external radiotherapy to aid contouring. None of these patients had sufficient uptake to be eligible for 177 Lu-DOTATATE or reliable contouring. Most recurrences were grades II and III, suggesting a loss of physiological somatostatin receptor overexpression in these tumors. Therefore, the benefit of treatment with 177 Lu-DOTATATE in the current indication is questionable. In the absence of a validated systemic treatment, and considering a few case reports, treatment with 177 Lu-PSMA could be investigated as an additional vectorized internal radiotherapy option.

False-Positive Bone Pitfall Lesion and Collateral Circulation: Don't Miss the True-Positive Lesion.

ABSTRACT: We report the case of a patient followed up for squamous cell carcinoma of the buccal floor with lymph node involvement. The initial staging PET/CT revealed bone foci that were not definitively pathological in the context of a regional collateral circulation secondary to a defibrillator. A new monitoring examination, conducted due to the rapid local progression, revealed a dissociated evolution of the bone uptake adjacent to the collateral circulation, some confirming false-positives, but one indicating a real metastasis. This case illustrates that bone uptakes without morphological lesions adjacent to a collateral circulation are not easily interpretable.

False-Positive Bone Lesion With Different PET/CT Tracers: Beyond Thrombosis, Be Aware of Any Collateral Circulation.

ABSTRACT: Collateral circulation is often secondary to a regional thrombosis. This phenomenon can lead to the detection of misleading bone lesions on imaging and is a well-known source of false-positives. Here, we present 2 different tracers PET/CT images, 18F-FDG and 18F-choline, with collateral circulation but without obvious thrombosis. Both cases displayed bone uptake, which mimicked metastasis. However, clinical follow-up ruled out metastasis and revealed false-positive bone lesions related to collateral circulation, even in the lack of acute or chronic underlying thrombotic processes.

Misleading FDG Uptake in Oncology Assessment: Beyond COVID-19 Vaccination-The Role of Pneumococcal Vaccination.

ABSTRACT: Here, we report the case of a 35-year-old woman who performed PET/CT 18F-FDG as an initial workup for HER2+ right breast invasive ductal carcinoma. Examination revealed multifocal breast involvement with homolateral lymph node involvement. Contralateral axillary adenopathy and diffuse splenic and osteomedullary hypermetabolism were also observed, suggesting associated lymphoma in the absence of a recent COVID-19 vaccination. Cytopuncture was discussed and finally postponed after the patient was found to have recently received a pneumococcal vaccination.

Colorectal Adenocarcinoma Mimicking Neuroendocrine Neoplasia on 18 F-FDOPA PET/CT.

ABSTRACT: We present a case of a 48-year-old woman who had previously undergone surgical resection for bladder paraganglioma. An 18 F-FDOPA PET/CT scan performed for suspected colorectal paraganglioma showed intense colorectal uptake associated with adenopathy. Histological examination did not support the presence of a neuroendocrine tumor but instead confirmed the presence of moderately differentiated colorectal adenocarcinoma. Colorectal adenocarcinoma belongs to the list of nonneuroendocrine false-positive tumors that can be detected using 18 F-FDOPA. Therefore, a morphological analysis is important. Thus, 18 F-FDOPA may be a marker for the aggressiveness of colorectal adenocarcinoma.

False-Negative Neuroendocrine Tumor Identified With 68Ga-DOTATOC PET/CT: A Case of Well-Differentiated Somatostatinoma.

ABSTRACT: We report the case of a 25-year-old man who was undergoing follow-up for neurofibromatosis type 1. The man underwent 68Ga-DOTATOC PET/CT for a suspected well-differentiated duodenal neuroendocrine tumor. This examination did not reveal any significant uptake, whereas complementary 18F-FDG PET/CT showed moderate 18F-FDG uptake in the primary tumor as well as the adenopathy. Histology, a well-differentiated duodenal neuroendocrine tumor was confirmed, consistent with the diagnosis of somatostatinoma. Although rare, this well-differentiated neuroendocrine tumor should be kept in mind as a possible source of false-negative somatostatin receptor PET/CT findings.

Absence of Galectin-1 accelerates CD8⁺ T cell-mediated graft rejection.

Galectin-1 (Gal-1) is a member of a family of endogenous ß-galactose-binding proteins with a role in preventing autoimmune diseases and chronic inflammation. In this study, the involvement of Gal-1 in graft rejection was investigated by using Gal-1-deficient mice (Gal-1⁻/⁻). We demonstrate that in the absence of Gal-1, skin grafts are rejected earlier compared with those of WT mice, and that this is due to the role played by CD8⁺ T cells in graft rejection. The difference in graft survival observed between Gal-1⁻/⁻ and WT mice was explained by both an increase in the percentage of antigen-specific CD8+ T cells and by preferential secretion of IFN-γ and IL-17 by CD8⁺ T cells in Gal-1⁻/⁻ mice compared with WT mice. This study suggests that endogenous expression of Gal-1 contributes to graft survival. The results obtained from the use of mice deficient in Gal-1 also confirm a key role for CD8⁺ T cells in graft rejection.

Unintentional Intra-arterial Injection of 177Lu-PSMA-1 in a Patient With a Peritoneal Carcinosis Secondary to a Metastatic Prostate Cancer.

ABSTRACT: We report the case of an 81-year-old man presenting with peritoneal carcinosis secondary to a metastatic castrate-resistant prostate cancer addressed for 177Lu-PSMA-1 therapy. During the second cycle, a diffuse uptake in his left forearm was observed on the 1-hour postinjection scintigraphy, typical for an accidental intra-arterial injection. Less than 24 hours postinjection, a full removal of the intra-arterial injection was observed in the man, without any pain or symptoms. Moreover, the man demonstrated an 85% PSA reduction and a CT OR following the RECIST 1.1 criteria after 3 cycles.

Intense Diffuse Lung Uptake Due to Interstitial Pneumopathy Related to Polyangiitis Granulomata in 68 Ga-PSMA-11 PET/CT.

ABSTRACT: We reported the case of a 73-year-old man for whom a prostatic adenocarcinoma with synchronous bone metastases was diagnosed. Because his disease was progressing despite several lines of chemotherapy and hormonotherapy, he was screened with a 68 Ga-PSMA PET/CT for a possible 177 Lu-PSMA-617 therapy. The examination demonstrated an intense diffuse bone uptake related to the known bone involvement. It also showed an unexpected diffuse and intense lung uptake, secondary to an active polyangiitis granulomata. This intense lung uptake prohibits the radioligand therapy.