Cell cross talk within the lymphoma tumor microenvironment: follicular lymphoma as a paradigm

ABSTRACT

Follicular lymphoma (FL) is an indolent yet incurable germinal center B-cell lymphoma retaining a characteristic follicular architecture. FL tumor B cells are highly dependent on direct and indirect interactions with a specific and complex tumor microenvironment (TME). Recently, great progress has been made in describing the heterogeneity and dynamics of the FL TME and in depicting how tumor clonal and functional heterogeneity rely on the integration of TME-related signals. Specifically, the FL TME is enriched for exhausted cytotoxic T cells, immunosuppressive regulatory T cells of various origins, and follicular helper T cells overexpressing B-cell and TME reprogramming factors. FL stromal cells have also emerged as crucial determinants of tumor growth and remodeling, with a key role in the deregulation of chemokines and extracellular matrix composition. Finally, tumor-associated macrophages play a dual function, contributing to FL cell phagocytosis and FL cell survival through long-lasting B-cell receptor activation. The resulting tumor-permissive niches show additional layers of site-to-site and kinetic heterogeneity, which raise questions about the niche of FL-committed precursor cells supporting early lymphomagenesis, clonal evolution, relapse, and transformation. In turn, FL B-cell genetic and nongenetic determinants drive the reprogramming of FL immune and stromal TME. Therefore, offering a functional picture of the dynamic cross talk between FL cells and TME holds the promise of identifying the mechanisms of therapy resistance, stratifying patients, and developing new therapeutic approaches capable of eradicating FL disease in its different ecosystems.

NLRP3 inflammasome in sepsis: Don't overlook the small steps-they can make a big difference!

In sepsis, persistent activation of NLRP3 is associated with expansion of both monocytic and granulocytic MDSC, along with high plasma concentration of IL-10.

Innovative cellular therapies for autoimmune diseases: expert-based position statement and clinical practice recommendations from the EBMT practice harmonization and guidelines committee

Autoimmune diseases (ADs) are characterized by loss of immune tolerance, high chronicity, with substantial morbidity and mortality, despite conventional immunosuppression (IS) or targeted disease modifying therapies (DMTs), which usually require repeated administration. Recently, novel cellular therapies (CT), including mesenchymal stromal cells (MSC), Chimeric Antigen Receptors T cells (CART) and regulatory T cells (Tregs), have been successfully adopted in ADs. An international expert panel of the European Society for Blood and Marrow Transplantation and the International Society for the Cell and Gene Therapy, reviewed all available evidence, based on the current literature and expert practices, on use of MSC, CART and Tregs, in AD patients with rheumatological, neurological, and gastroenterological indications. Expert-based consensus and recommendations for best practice and quality of patient care were developed to support clinicians, scientists, and their multidisciplinary teams, as well as patients and care providers and will be regularly updated.

NGFR regulates stromal cell activation in germinal centers

Nerve growth factor receptor (NGFR) is expressed by follicular dendritic cells (FDCs). However, the role of NGFR in the humoral response is not well defined. Here, we study the effect of Ngfr loss on lymph node organization and function, demonstrating that Ngfr depletion leads to spontaneous germinal center (GC) formation and an expansion of the GC B cell compartment. In accordance with this effect, stromal cells are altered in Ngfr-/- mice with a higher frequency of FDCs, characterized by CD21/35, MAdCAM-1, and VCAM-1 overexpression. GCs are located ectopically in Ngfr-/- mice, with lost polarization together with impaired high-affinity antibody production and an increase in circulating autoantibodies. We observe higher levels of autoantibodies in Bcl2 Tg/Ngfr-/- mice, concomitant with a higher incidence of autoimmunity and lower overall survival. Our work shows that NGFR is involved in maintaining GC structure and function, participating in GC activation, antibody production, and immune tolerance.

KDM6B drives epigenetic reprogramming associated with lymphoid stromal cell early commitment and immune properties

Mature lymphoid stromal cells (LSCs) are key organizers of immune responses within secondary lymphoid organs. Similarly, inflammation-driven tertiary lymphoid structures depend on immunofibroblasts producing lymphoid cytokines and chemokines. Recent studies have explored the origin and heterogeneity of LSC/immunofibroblasts, yet the molecular and epigenetic mechanisms involved in their commitment are still unknown. This study explored the transcriptomic and epigenetic reprogramming underlying LSC/immunofibroblast commitment. We identified the induction of lysine demethylase 6B (KDM6B) as the primary epigenetic driver of early immunofibroblast differentiation. In addition, we observed an enrichment for KDM6B gene signature in murine inflammatory fibroblasts and pathogenic stroma of patients with autoimmune diseases. Last, KDM6B was required for the acquisition of LSC/immunofibroblast functional properties, including the up-regulation of CCL2 and the resulting recruitment of monocytes. Overall, our results reveal epigenetic mechanisms that participate in the early commitment and immune properties of immunofibroblasts and support the use of epigenetic modifiers as fibroblast-targeting strategies in chronic inflammation.

Modeling the crosstalk between malignant B cells and their microenvironment in B-cell lymphomas: challenges and opportunities

B-cell lymphomas are a group of heterogeneous neoplasms resulting from the clonal expansion of mature B cells arrested at various stages of differentiation. Specifically, two lymphoma subtypes arise from germinal centers (GCs), namely follicular lymphoma (FL) and GC B-cell diffuse large B-cell lymphoma (GCB-DLBCL). In addition to recent advances in describing the genetic landscape of FL and GCB-DLBCL, tumor microenvironment (TME) has progressively emerged as a central determinant of early lymphomagenesis, subclonal evolution, and late progression/transformation. The lymphoma-supportive niche integrates a dynamic and coordinated network of immune and stromal cells defining microarchitecture and mechanical constraints and regulating tumor cell migration, survival, proliferation, and immune escape. Several questions are still unsolved regarding the interplay between lymphoma B cells and their TME, including the mechanisms supporting these bidirectional interactions, the impact of the kinetic and spatial heterogeneity of the tumor niche on B-cell heterogeneity, and how individual genetic alterations can trigger both B-cell intrinsic and B-cell extrinsic signals driving the reprogramming of non-malignant cells. Finally, it is not clear whether these interactions might promote resistance to treatment or, conversely, offer valuable therapeutic opportunities. A major challenge in addressing these questions is the lack of relevant models integrating tumor cells with specific genetic hits, non-malignant cells with adequate functional properties and organization, extracellular matrix, and biomechanical forces. We propose here an overview of the 3D in vitro models, xenograft approaches, and genetically-engineered mouse models recently developed to study GC B-cell lymphomas with a specific focus on the pros and cons of each strategy in understanding B-cell lymphomagenesis and evaluating new therapeutic strategies.

Enteral citrulline supplementation versus placebo on SOFA score on day 7 in mechanically ventilated critically ill patients: the IMMUNOCITRE randomized clinical trial

BACKGROUND

Restoring plasma arginine levels through enteral administration of L-citrulline in critically ill patients may improve outcomes. We aimed to evaluate whether enteral L-citrulline administration reduced organ dysfunction based on the Sequential Organ Failure Assessment (SOFA) score and affected selected immune parameters in mechanically ventilated medical intensive care unit (ICU) patients.

METHODS

A randomized, double-blind, multicenter clinical trial of enteral administration of L-citrulline versus placebo for critically ill adult patients under invasive mechanical ventilation without sepsis or septic shock was conducted in four ICUs in France between September 2016 and February 2019. Patients were randomly assigned to receive enteral L-citrulline (5 g) every 12 h for 5 days or isonitrogenous, isocaloric placebo. The primary outcome was the SOFA score on day 7. Secondary outcomes included SOFA score improvement (defined as a decrease in total SOFA score by 2 points or more between day 1 and day 7), secondary infection acquisition, ICU length of stay, plasma amino acid levels, and immune biomarkers on day 3 and day 7 (HLA-DR expression on monocytes and interleukin-6).

RESULTS

Of 120 randomized patients (mean age, 60 ± 17 years; 44 [36.7%] women; ICU stay 10 days [IQR, 7-16]; incidence of secondary infections 25 patients (20.8%)), 60 were allocated to L-citrulline and 60 were allocated to placebo. Overall, there was no significant difference in organ dysfunction as assessed by the SOFA score on day 7 after enrollment (4 [IQR, 2-6] in the L-citrulline group vs. 4 [IQR, 2-7] in the placebo group; Mann‒Whitney U test, p = 0.9). Plasma arginine was significantly increased on day 3 in the treatment group, while immune parameters remained unaffected.

CONCLUSION

Among mechanically ventilated ICU patients without sepsis or septic shock, enteral L-citrulline administration did not result in a significant difference in SOFA score on day 7 compared to placebo.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier NCT02864017 (date of registration: 11 August 2016).

Axicabtagene ciloleucel as second-line therapy in large B cell lymphoma ineligible for autologous stem cell transplantation: a phase 2 trial

Axicabtagene ciloleucel (axi-cel) demonstrated superior efficacy compared to standard of care as second-line therapy in patients with high-risk relapsed/refractory (R/R) large B cell lymphoma (LBCL) considered eligible for autologous stem cell transplantation (ASCT); however, in clinical practice, roughly half of patients with R/R LBCL are deemed unsuitable candidates for ASCT. The efficacy of axi-cel remains to be ascertained in transplant-ineligible patients. ALYCANTE, an open-label, phase 2 study, evaluated axi-cel as a second-line therapy in 62 patients with R/R LBCL who were considered ineligible for ASCT. The primary end point was investigator-assessed complete metabolic response at 3 months from the axi-cel infusion. Key secondary end points included progression-free survival, overall survival and safety. The study met its primary end point with a complete metabolic response of 71.0% (95% confidence interval, 58.1-81.8%) at 3 months. With a median follow-up of 12.0 months (range, 2.1-17.9), median progression-free survival was 11.8 months (95% confidence interval, 8.4-not reached) and overall survival was not reached. There was no unexpected toxicity. Grade 3-4 cytokine release syndrome and neurologic events occurred in 8.1% and 14.5% of patients, respectively. These results support axi-cel as second-line therapy in patients with R/R LBCL ineligible for ASCT. ClinicalTrials.gov Identifier: NCT04531046 .

An International Society for Cell and Gene Therapy Mesenchymal Stromal Cells (MSC) Committee perspectives on International Standards Organization/Technical Committee 276 Biobanking Standards for bone marrow-MSCs and umbilical cord tissue-derived MSCs for research purposes

The rapidly growing field of mesenchymal stromal cell (MSC) basic and translational research requires standardization of terminology and functional characterization. The International Standards Organization's (ISO) Technical Committee (TC) on Biotechnology, working with extensive input from the International Society for Cells and Gene Therapy (ISCT), has recently published ISO standardization documents that are focused on biobanking of MSCs from two tissue sources, Wharton's Jelly, MSC(WJ) and Bone Marrow, MSC(M)), for research and development purposes and development. This manuscript explains the path towards the consensus on the following two documents: the Technical Standard ISO/TS 22859 for MSC(WJ) and the full ISO Standard 24651 for MSC(M) biobanking. The ISO standardization documents are aligned with ISCT's MSC committee position and recommendations on nomenclature because there was active input and incorporation of ISCT MSC committee recommendations in the development of these standards. The ISO standardization documents contain both requirements and recommendations for functional characterization of MSC(WJ) and MSC(M) using a matrix of assays. Importantly, the ISO standardization documents have a carefully defined scope and are meant for research use of culture expanded MSC(WJ) and MSC(M). The ISO standardization documents can be updated in a revision process and will be systematically reviewed after 3-5 years as scientific insights grow. They represent international consensus on MSC identity, definition, and characterization; are rigorous in detailing multivariate characterization of MSCs and represent an evolving-but-important first step in standardization of MSC biobanking and characterization for research use and development.

Phenotypic and proteomic analysis of plasma extracellular vesicles highlights them as potential biomarkers of primary Sjögren syndrome

Sjögren syndrome (SjS) is an autoimmune disease characterized by the destruction of the exocrine gland epithelia, causing a dryness of mucosa called sicca symptoms, and whose main life-threatening complication is lymphoma. There is a need for new biomarkers in this disease, notably diagnostic biomarkers for patients with genuine sicca symptoms that do not meet current criteria, and prognostic biomarkers for patients at risk of lymphoma. Plasma extracellular vesicles (EVs) are promising biomarker candidates in several diseases, but their potential has not yet been explored in SjS. In this proof-of-concept study, we characterized EVs from primary SjS patients (pSS, n=12) at the phenotypic and proteomic levels, compared to EVs from healthy donor (HD, n=8) and systemic lupus erythematosus patients (SLE, n=12). Specific plasma EVs subpopulations, derived from neutrophils, endothelial, and epithelial cells, were found increased in pSS. We also identified a pSS proteomic signature in plasma EVs, including neutrophil-, epithelial-, and endothelial-related proteins, such as integrin alpha M (ITGAM), olfactomedin-4 (OLFM4), Ras-related protein RAB10, and CD36. Overall, our results support the relevance of plasma EVs as biomarkers in SjS.

Functional specialization of short-lived and long-lived macrophage subsets in human tonsils

Macrophages play a central role in tissue homeostasis and host defense. However, the properties of human macrophages in non-diseased tissues remain poorly understood. Here, we characterized human tonsil macrophages and identified three subsets with distinct phenotype, transcriptome, life cycle, and function. CD36hi macrophages were related to monocytes, while CD36lo macrophages showed features of embryonic origin and CD36int macrophages had a mixed profile. scRNA-seq on non-human primate tonsils showed that monocyte recruitment did not pre-exist an immune challenge. Functionally, CD36hi macrophages were specialized for stimulating T follicular helper cells, by producing Activin A. Combining reconstruction of ligand-receptor interactions and functional assays, we identified stromal cell-derived TNF-α as an inducer of Activin A secretion. However, only CD36hi macrophages were primed for Activin A expression, via the activity of IRF1. Our results provide insight into the heterogeneity of human lymphoid organ macrophages and show that tonsil CD36hi macrophage specialization is the result of both intrinsic features and interaction with stromal cells.

Randomized Phase III Trial Evaluating Subcutaneous Rituximab for the First-Line Treatment of Low-Tumor Burden Follicular Lymphoma: Results of a LYSA Study

PURPOSE

Rituximab improves progression-free survival (PFS) and time to next treatment (TTNT) when compared with the watch and wait strategy for patients with low-tumor burden follicular lymphoma (FL). Prolonged rituximab maintenance did not prolong TTNT, whereas it raises concerns about resources use and patient adhesion. Our aim was then to investigate the use of short rituximab maintenance using the subcutaneous (SC) route in patients with low-tumor burden FL.

METHODS

Patients with histologically confirmed CD20⁺ low-tumor burden FL were randomly assigned to receive either rituximab, 375 mg/m² once daily on D1, D8, D15, and D22, intravenous route (IV, control arm), or rituximab, 375 mg/m², on day 1 (D1), IV followed by rituximab 1,400 mg total dose, SC once daily on D8, D15, and D22, with maintenance at months 3 (M3), M5, M7, and M9 (experimental arm). The primary end point was PFS. Secondary end points included safety, overall response rates, TTNT, and overall survival (OS).

RESULTS

Two hundred two patients with low-tumor burden FL were randomly assigned to the experimental (n = 100) or control arm (n = 102). The primary end point was met: the 4-year PFS was 58.1% (95% CI, 47.5 to 67.4) and 41.2% (95% CI, 30.6 to 51.6) in experimental and control arms, respectively (hazard ratio, 0.585 [0.393 to 0.871]; P = .0076). Complete response (CR) rates were 59.0% (95% CI, 48.7 to 68.7) in the experimental arm and 36.3% (95% CI, 27.0 to 46.4) in the control arm (P = .001). TTNT and OS were not significantly different. CR was associated with longer PFS and TTNT. High rituximab exposure during the first three months was independently associated with higher CR, PFS, and TTNT.

CONCLUSION

SC rituximab improves PFS for patients with low-tumor burden FL when used in induction followed by short maintenance. High rituximab exposure during the first 3 months after treatment initiation is, however, the only parameter influencing patient outcomes.

Regulatory B Cells Contribute to the Clinical Response After Bone Marrow-Derived Mesenchymal Stromal Cell Infusion in Patients With Systemic Sclerosis

Mesenchymal stromal cells (MSCs) have recently emerged as an interesting therapeutic approach for patients with progressive systemic sclerosis (SSc), a rare and life-threatening orphan autoimmune disease. Whereas MSC immunomodulatory potential is considered as a central mechanism for their clinical benefit, very few data are available on the impact of MSCs on immune cell subsets in vivo. In the current extended study of a phase I/II clinical trial exploring the injection of a single dose of allogeneic bone marrow-MSCs (alloBM-MSCs) in patients with severe SSc (NCT02213705), we performed a longitudinal in-depth characterization of circulating immune cells in 19 MSC-treated patients, including 14 responders and 5 non-responders. By a combination of flow cytometry and transcriptomic analyses, we highlighted an increase in circulating CD24hiCD27posCD38lo/neg memory B cells, the main IL-10-producing regulatory B cell (Breg) subset, and an upregulation of IL10 expression in ex-vivo purified B cells, specifically in responder patients, early after the alloBM-MSC infusion. In addition, a deeper alteration of the B-cell compartment before alloBM-MSC treatment, including a higher expression of profibrotic cytokines IL6 and TGFβ by sorted B cells was associated with a non-responder clinical status. Finally, BM-MSCs were able to directly upregulate IL-10 production in activated B cells in vitro. These data suggest that cytokine-producing B cells, in particular Breg, are pivotal effectors of BM-MSC therapeutic activity in SSc. Their quantification as activity biomarkers in MSC potency assays and patient selection criteria may be considered to reach optimal clinical benefit when designing MSC-based clinical trials.

Citrulline enteral administration markedly reduces immunosuppressive extrafollicular plasma cell differentiation in a preclinical model of sepsis

The sustained immunosuppression associated with severe sepsis favors an increased susceptibility to secondary infections and remains incompletely understood. Plasmablast and plasma cell subsets, whose primary function is to secrete antibodies, have emerged as important suppressive populations that expand during sepsis. In particular, sepsis supports CD39^hi plasmablast metabolic reprogramming associated with adenosine-mediated suppressive activity. Arginine deficiency has been linked to an increased risk of secondary infections in sepsis. Overcoming arginine shortage by citrulline administration efficiently improves sepsis-induced immunosuppression and secondary infections in the cecal ligation and puncture murine model. Here, we aimed to determine the impact of citrulline administration on B cell suppressive responses in sepsis. We demonstrate that restoring arginine bioavailability through citrulline administration markedly reduces the dominant extrafollicular B cell response, decreasing the immunosuppressive LAG3⁺ and CD39⁺ plasma cell populations, and restoring splenic follicles. At the molecular level, the IRF4/MYC-mediated B cell reprogramming required for extrafollicular plasma cell differentiation is shunted in the splenic B cells of mice fed with citrulline. Our study reveals a prominent impact of nutrition on B cell responses and plasma cell differentiation and further supports the development of citrulline-based clinical studies to prevent sepsis-associated immune dysfunction.

Niche-expressed Galectin-1 is involved in pre-B acute lymphoblastic leukemia relapse through pre-BCR activation

B-cell acute lymphoblastic leukemia (B-ALL) reflects the malignant counterpart of developing B cells in the bone marrow (BM). Despite tremendous progress in B-ALL treatment, the overall survival of adults at diagnosis and patients at all ages after relapse remains poor. Galectin-1 (GAL1) expressed by BM supportive niches delivers proliferation signals to normal pre-B cells through interaction with the pre-B cell receptor (pre-BCR). Here, we asked whether GAL1 gives non-cell autonomous signals to pre-BCR⁺ pre-B ALL, in addition to cell-autonomous signals linked to genetic alterations. In syngeneic and patient-derived xenograft (PDX) murine models, murine and human pre-B ALL development is influenced by GAL1 produced by BM niches through pre-BCR-dependent signals, similarly to normal pre-B cells. Furthermore, targeting pre-BCR signaling together with cell-autonomous oncogenic pathways in pre-B ALL PDX improved treatment response. Our results show that non-cell autonomous signals transmitted by BM niches represent promising targets to improve B-ALL patient survival.

Periosteal skeletal stem cells can migrate into the bone marrow and support hematopoiesis after injury

Functional stromal cells are known to support bone marrow regeneration after chemotherapy or radiation-induced injury to prevent prolonged myelosuppression. However, it is not known how stromal cells within the bone marrow are regenerated after injury. We have utilized a whole bone transplantation model that mimics the initial bone marrow necrosis and fatty infiltration that is seen after bone marrow injury and subsequent recovery. We demonstrate that periosteal skeletal stem cells (P-SSCs) can migrate into the bone marrow and contribute to stromal regeneration and hematopoietic recovery. Once in the bone marrow, P-SSCs are phenotypically and functionally reprogrammed into bone marrow mesenchymal stem cells (BM-MSCs), expressing high levels of hematopoietic stem cell (HSC) niche factors, such as Cxcl12 and Kitl. Additionally, our results further indicate that P-SSCs are more resistant to acute stress than BM-MSCs. Here, we report a new function of P-SSCs, highlighting their major plasticity and the role of the periosteum as a potential source of BM-MSCs following acute bone marrow injury.

FOSL2 truncating variants in the last exon cause a neurodevelopmental disorder with scalp and enamel defects

PURPOSE

We aimed to investigate the molecular basis of a novel recognizable neurodevelopmental syndrome with scalp and enamel anomalies caused by truncating variants in the last exon of the gene FOSL2, encoding a subunit of the AP-1 complex.

METHODS

Exome sequencing was used to identify genetic variants in all cases, recruited through Matchmaker exchange. Gene expression in blood was analyzed using reverse transcription polymerase chain reaction. In vitro coimmunoprecipitation and proteasome inhibition assays in transfected HEK293 cells were performed to explore protein and AP-1 complex stability.

RESULTS

We identified 11 individuals from 10 families with mostly de novo truncating FOSL2 variants sharing a strikingly similar phenotype characterized by prenatal growth retardation, localized cutis scalp aplasia with or without skull defects, neurodevelopmental delay with autism spectrum disorder, enamel hypoplasia, and congenital cataracts. Mutant FOSL2 messenger RNAs escaped nonsense-mediated messenger RNA decay. Truncated FOSL2 interacts with c-JUN, thus mutated AP-1 complexes could be formed.

CONCLUSION

Truncating variants in the last exon of FOSL2 associate a distinct clinical phenotype by altering the regulatory degradation of the AP-1 complex. These findings reveal a new role for FOSL2 in human pathology.

Distinct B-Cell Specific Transcriptional Contexts of the BCL2 Oncogene Impact Pre-Malignant Development in Mouse Models

Simple Summary

Beyond the classical t(14;18) translocation associated with follicular lymphoma, BCL2 is deregulated in multiple B-cell malignancies, including some cases of myeloma, and through diverse genetic anomalies. It is currently unclear how the various deregulation patterns mechanistically impact the phenotype of theses malignancies. We designed two different BCL2 deregulation models in transgenic mice, whereby the oncogene was either associated with the IgH3′RR superenhancer, as in t(14;18), or inserted into the kappa light chain locus. We compared the impact of these models on B-cell fate and lymphoid tissues. Linkage to the IgH superenhancer showed a quite specific impact on germinal center B cell populations. The Ig kappa model was much less specific and strongly boosted the plasma cell in-flow and the accumulation of long-lived plasma cells.

Abstract

Upregulated expression of the anti-apoptotic BCL2 oncogene is a common feature of various types of B-cell malignancies, from lymphoma to leukemia or myeloma. It is currently unclear how the various patterns of deregulation observed in pathology eventually impact the phenotype of malignant B cells and their microenvironment. Follicular lymphoma (FL) is the most common non-Hodgkin lymphoma arising from malignant germinal center (GC) B-cells, and its major hallmark is the t(14:18) translocation occurring in B cell progenitors and placing the BCL2 gene under the control of the immunoglobulin heavy chain locus regulatory region (IgH 3′RR), thus exposing it to constitutive expression and hypermutation. Translocation of BCL2 onto Ig light chain genes, BCL2 gene amplification, and other mechanisms yielding BCL2 over-expression are, in contrast, rare in FL and rather promote other types of B-cell lymphoma, leukemia, or multiple myeloma. In order to assess the impact of distinct BCL2 deregulation patterns on B-cell fate, two mouse models were designed that associated BCL2 and its full P1-P2 promoter region to either the IgH 3′RR, within a “3′RR-BCL2” transgene mimicking the situation seen in FL, or an Ig light chain locus context, through knock-in insertion at the Igκ locus (“Igκ-BCL2” model). While linkage to the IgH 3′ RR mostly yielded expression in GC B-cells, the Igκ-driven up-regulation culminated in plasmablasts and plasma cells, boosting the plasma cell in-flow and the accumulation of long-lived plasma cells. These data demonstrate that the timing and level of BCL2 deregulation are crucial for the behavior of B cells inside GC, an observation that could strongly impact the lymphomagenesis process triggered by secondary genetic hits.

Multiple Sclerosis CSF Is Enriched With Follicular T Cells Displaying a Th1/Eomes Signature

BACKGROUND AND OBJECTIVES

Tertiary lymphoid structures and aggregates are reported in the meninges of patients with multiple sclerosis (MS), especially at the progressive stage, and are strongly associated with cortical lesions and disability. Besides B cells, these structures comprise follicular helper T (Tfh) cells that are crucial to support B-cell differentiation. Tfh cells play a pivotal role in amplifying autoreactive B cells and promoting autoantibody production in several autoimmune diseases, but very few are known in MS. In this study, we examined the phenotype, frequency, and transcriptome of circulating cTfh cells in the blood and CSF of patients with relapsing-remitting MS (RRMS).

METHODS

The phenotype and frequency of cTfh cells were analyzed in the blood of 39 healthy controls and 41 untreated patients with RRMS and in the CSF and paired blood of 10 patients with drug-naive RRMS at diagnosis by flow cytometry. Using an in vitro model of blood-brain barrier, we assessed the transendothelial migratory abilities of the different cTfh-cell subsets. Finally, we performed an RNA sequencing analysis of paired CSF cTfh cells and blood cTfh cells in 8 patients sampled at their first demyelinating event.

RESULTS

The blood phenotype and frequency of cTfh cells were not significantly modified in patients with RRMS. In the CSF, we found an important infiltration of Tfh1 cells, with a high proportion of activated PD1⁺ cells. We demonstrated that the specific subset of Tfh1 cells presents increased migration abilities to cross an in vitro model of blood-brain barrier. Of interest, even at the first demyelinating event, cTfh cells in the CSF display specific characteristics with upregulation of EOMES gene and proinflammatory/cytotoxic transcriptomic signature able to efficiently distinguish cTfh cells from the CSF and blood. Finally, interactome analysis revealed potential strong cross talk between pathogenic B cells and CSF cTfh cells, pointing out the CSF as opportune supportive compartment and highlighting the very early implication of B-cell helper T cells in MS pathogenesis.

DISCUSSION

Overall, CSF enrichment in activated Tfh1 as soon as disease diagnosis, associated with high expression of EOMES, and a predicted high propensity to interact with CSF B cells suggest that these cells probably contribute to disease onset and/or activity.

Modified nanofat grafting: Stromal vascular fraction simple and efficient mechanical isolation technique and perspectives in clinical recellularization applications

Background: Nanofat grafting (NG) is a simple and cost-effective method of lipoaspirates with inter-syringe passages, to produce stromal vascular fraction (SVF) and isolate adipose-derived stem cells (ASCs). This represents a tremendous interest in the future clinical needs of tissue engineering. In this study, we optimized the NG technique to increase the yield of ASC extractions.

Methods: We analyzed three groups of SVF obtained by 20, 30, and 40 inter-syringe passages. The control group was an SVF obtained by enzymatic digestion with Celase. We studied their cell composition by flow cytometry, observed their architecture by confocal microscopy, and observed immunomodulatory properties of the ASCs from each of the SVFs by measuring inflammatory markers of macrophages obtained by an ASC monocyte co-culture.

Results: We have established the first cell mapping of the stromal vascular fraction of adipose tissue. The results showed that SVF obtained by 20 inter-syringe passages contains more statistically significant total cells, more cells expressing the ASC phenotype, more endothelial cells, and produces more CFU-F than the SVF obtained by 30 and 40 passages and by enzymatic digestion. Confocal microscopy showed the presence of residual adipocytes in SVF obtained by inter-syringe passages but not by enzymatic digestion. The functional study indicates an orientation toward a more anti-inflammatory profile and homogenization of their immunomodulatory properties.

Conclusion: This study places mechanically dissociated SVF in the center of approaches to easily extract ASCs and a wide variety and number of other progenitor cells, immediately available in a clinical setting to provide both the amount and quality of cells required for decellularized tissues.

Subcutaneous rituximab induction followed by short rituximab maintenance to improve progression-free survival in patients with low-tumor burden follicular lymphoma: Final results of FLIRT phase III trial, a LYSA study

7512

Background: In low–tumor burden follicular lymphoma (FL), maintenance rituximab (MR) has been shown to improve progression-free survival (PFS) when compared with observation. RESORT study (Kahl et al. 2014) clearly showed that Rituximab (R) retreatment strategy provided similar time to treatment failure that maintenance strategy with less rituximab use. It is not known whether short MR using sub-cutaneous (sc) route could improve PFS while reducing R infusions. Methods: Patients with the diagnosis of low-tumor burden FL (GELF criteria) within the last 4 months before signing informed consent were randomly assigned to either Iv-Arm : 4-weekly iv infusions of R 375 mg/m2 or Sc-Arm: one iv infusion of R (D1, 375 mg/m2) followed by 3 sc infusions of R (1400 mg, on days 8, 15 and 22) followed by Rsc maintenance on months (M) 3, 5, 7 and 9. The primary endpoint was PFS and secondary endpoints included safety, response rates (M3, M12), duration of response (DOR), time to next anti-lymphoma treatment (TTNTL) and overall survival (OS). Results: A total of 202 patients were included, 102 in Iv-Arm and 100 in Sc-Arm and constitute the intent to treat population. The median uses of R were 4 infusions (range: 1-4, Iv-Arm) and 8 infusions (range: 2-8, Sc-Arm). With a median follow-up of 50.2 months (95% CI: 48.3-54.5), 4‐year PFS was 41.2% (95% CI: 30.6%; 51.6%) in Iv-Arm and 58.1% (95% CI: 47.5%; 67.4%) in Sc-Arm. Median PFS was then 36.1 months (95% IC: 23.9-52.6) in Iv-Arm and 73.8 months (95% CI: 39.4-NA) in Sc-Arm (Fig 1.) (HR: 0.58; 95% CI: 0.39-0.87; P = 0.0076). Patients with at least one AE grade ≥ 3 were 8 (7.8%) and 12 (12.4%) in Iv-Arm and Sc-Arm, respectively. According to Cheson criteria, ORR at M3 were: 83% and 80% including 38% and 29% of CR/CRu, in Iv-Arm and Sc-Arm, respectively. According to Lugano criteria, 36.3% (Iv-Arm; 95% CI: 27.0%. 46.4%) and 59.0% (Sc-Arm; 95% CI: 48.7%; 68.7%) were in CMR at M12. The median DOR was 32.7 months (95% IC: 20.6-49.7) and 70.8 months (36.4-NR) (HR: 0.56; 95% IC: 0.37-0.84) in Iv-Arm and Sc-Arm, respectively. 4-year TTNLT was 54% (95% CI: 42.9%; 63.8%) in Iv-Arm and 61.8% (95% CI: 50.8.6%; 71.0%) in Sc-Arm (HR: 0.81, 95% IC: 0.53-1.24). 4-year TTNLT chemotherapy was 60.8 % (95% CI: 49.6%; 70.3%) in Iv-Arm and 71.4% (95% CI: 60.7%; 79.8%) in Sc-arm (HR: 0.69, 95% IC: 0.42-1.12) (Fig 2.). OS was not different according to treatment arm, 4-year OS was 95.0% (95% CI: 88.5%; 97.9%) in Iv-Arm and 96.7% (95% CI: 89.9%; 98.9%) in Sc-Arm. Conclusions: This phase III study met its primary endpoint and demonstrated that Rsc induction followed by a short MRsc improves PFS of patients with low-tumor burden. MRsc did not however improved TTNLT. R in low-tumor burden FL allowed to avoid cytotoxic use in most patients 6 years after treatment initiation. Clinical trial information: NCT02303119.

FlexDotPlot: a universal and modular dot plot visualization tool for complex multifaceted data

Motivation

Dot plots are heatmap-like charts that provide a compact way to simultaneously display two quantitative information by means of dots of different sizes and colors. Despite the popularity of this visualization method, particularly in single-cell RNA-sequencing (scRNA-seq) studies, existing tools used to make dot plots are limited in terms of functionality and usability.

Results

We developed FlexDotPlot, an R package for generating dot plots from multifaceted data, including scRNA-seq data. It provides a universal and easy-to-use solution with a high versatility. An interactive R Shiny application is also available allowing non-R users to easily generate dot plots with several tunable parameters.

Availability and implementation

Source code and detailed manual are available on CRAN (stable version) and at https://github.com/Simon-Leonard/FlexDotPlot (development version). Code to reproduce figures is available at https://github.com/Simon-Leonard/FlexDotPlot_paper. A Shiny app is available as a stand-alone application within the package.

Supplementary information

Supplementary data are available at Bioinformatics Advances online.

Bone Marrow Lymphoid Niche Adaptation to Mature B Cell Neoplasms

B-cell non-Hodgkin lymphoma (B-NHL) evolution and treatment are complicated by a high prevalence of relapses primarily due to the ability of malignant B cells to interact with tumor-supportive lymph node (LN) and bone marrow (BM) microenvironments. In particular, progressive alterations of BM stromal cells sustain the survival, proliferation, and drug resistance of tumor B cells during diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), and chronic lymphocytic leukemia (CLL). The current review describes how the crosstalk between BM stromal cells and lymphoma tumor cells triggers the establishment of the tumor supportive niche. DLBCL, FL, and CLL display distinct patterns of BM involvement, but in each case tumor-infiltrating stromal cells, corresponding to cancer-associated fibroblasts, exhibit specific phenotypic and functional features promoting the recruitment, adhesion, and survival of tumor cells. Tumor cell-derived extracellular vesicles have been recently proposed as playing a central role in triggering initial induction of tumor-supportive niches, notably within the BM. Finally, the disruption of the BM stroma reprogramming emerges as a promising therapeutic option in B-cell lymphomas. Targeting the crosstalk between BM stromal cells and malignant B cells, either through the inhibition of stroma-derived B-cell growth factors or through the mobilization of clonal B cells outside their supportive BM niche, should in particular be further evaluated as a way to avoid relapses by abrogating resistance niches.

Committed Human CD23-Negative Light-Zone Germinal Center B Cells Delineate Transcriptional Program Supporting Plasma Cell Differentiation

B cell affinity maturation occurs in the germinal center (GC). Light-zone (LZ) GC B cells (B_GC-cells) interact with follicular dendritic cells (FDCs) and compete for the limited, sequential help from T follicular helper cells needed to escape from apoptosis and complete their differentiation. The highest-affinity LZ B_GC-cells enter the cell cycle and differentiate into PCs, following a dramatic epigenetic reorganization that induces transcriptome changes in general and the expression of the PRDM1 gene in particular. Human PC precursors are characterized by the loss of IL-4/STAT6 signaling and the absence of CD23 expression. Here, we studied the fate of human LZ B_GC-cells as a function of their CD23 expression. We first showed that CD23 expression was restricted to the GC LZ, where it was primarily expressed by FDCs; less than 10% of tonsil LZ B_GC-cells were positive. Sorted LZ B_GC-cells left in culture and stimulated upregulated CD23 expression but were unable to differentiate into PCs – in contrast to cells that did not upregulate CD23 expression. An in-depth analysis (including single-cell gene expression) showed that stimulated CD23-negative LZ B_GC-cells differentiated into plasmablasts and time course of gene expression changes delineates the transcriptional program that sustains PC differentiation. In particular, we identified a B cell proliferation signature supported by a transient MYC gene expression. Overall, the CD23 marker might be of value in answering questions about the differentiation of normal B_GC-cells and allowed us to propose an instructive LZ B_GC-cells maturation and fate model.

[Perspectives for the evolution and use of CAR-T cells]

CAR-T cells have recently made a stunning entry on the arena of immunotherapy of B-cell lymphomas. This new treatment approach represents the culmination of 30 years of efforts to understand the role of T cells in the antitumor response. However, this technology is still in its infancy and suffers from a number of limitations. Many areas for improvement, based in particular on the possibilities of additional genetic manipulations of CAR-T cells, aim at reducing their toxicity, increasing their persistence in vivo, preventing the risk of tumor escape, recruiting other immune effectors, or extending their application to other cancers. Further studies of the dynamic interaction between the patient and these live drugs will allow elucidating the mechanisms determining the antitumor response in this context and thus developing more efficiently the future CAR-T cells.

Nonclassical Monocytes Are Prone to Migrate Into Tumor in Diffuse Large B-Cell Lymphoma

Absolute count of circulating monocytes has been proposed as an independent prognostic factor in diffuse large B-cell lymphoma (DLBCL). However, monocyte nomenclature includes various subsets with pro-, anti-inflammatory, or suppressive functions, and their clinical relevance in DLBCL has been poorly explored. Herein, we broadly assessed circulating monocyte heterogeneity in 91 DLBCL patients. Classical- (cMO, CD14pos CD16neg) and intermediate- (iMO, CD14pos CD16pos) monocytes accumulated in DLBCL peripheral blood and exhibited an inflammatory phenotype. On the opposite, nonclassical monocytes (ncMOSlanpos, CD14low CD16pos Slanneg and ncMOSlanneg, CD14low CD16pos, Slanneg) were decreased in peripheral blood. Tumor-conditioned monocytes presented similarities with ncMO phenotype from DLBCL and were prone to migrate in response to CCL5 and CXCL12, and presented similarities with DLBCL-infiltrated myeloid cells, as defined by mass cytometry. Finally, we demonstrated the adverse value of an accumulation of nonclassical monocytes in 2 independent cohorts of DLBCL.

Fam72a enforces error-prone DNA repair during antibody diversification

Efficient humoral responses rely on DNA damage, mutagenesis and error-prone DNA repair. Diversification of B cell receptors through somatic hypermutation and class-switch recombination are initiated by cytidine deamination in DNA mediated by activation-induced cytidine deaminase (AID)1 and by the subsequent excision of the resulting uracils by uracil DNA glycosylase (UNG) and by mismatch repair proteins1-3. Although uracils arising in DNA are accurately repaired1-4, how these pathways are co-opted to generate mutations and double-strand DNA breaks in the context of somatic hypermutation and class-switch recombination is unknown1-3. Here we performed a genome-wide CRISPR-Cas9 knockout screen for genes involved in class-switch recombination and identified FAM72A, a protein that interacts with the nuclear isoform of UNG (UNG2)5 and is overexpressed in several cancers5. We show that the FAM72A-UNG2 interaction controls the levels of UNG2 and that class-switch recombination is defective in Fam72a-/- B cells due to the upregulation of UNG2. Moreover, we show that somatic hypermutation is reduced in Fam72a-/- B cells and that its pattern is skewed upon upregulation of UNG2. Our results are consistent with a model in which FAM72A interacts with UNG2 to control its physiological level by triggering its degradation, regulating the level of uracil excision and thus the balance between error-prone and error-free DNA repair. Our findings have potential implications for tumorigenesis, as reduced levels of UNG2 mediated by overexpression of Fam72a would shift the balance towards mutagenic DNA repair, rendering cells more prone to acquire mutations.

Neutrophil function and bactericidal activity against Staphylococcus aureus after cardiac surgery with cardiopulmonary bypass

Staphylococcus aureus is the main bacterial pathogen encountered in mediastinitis after cardiac surgical procedures; it remains a devastating complication with a high mortality rate. As neutrophils have a primordial role in the defense against staphylococcus infection and cardiopulmonary bypass (CPB) is known to induce immunosuppression, the aim of this study was to investigate CPB impact on neutrophil functions. Patients without known immunosuppression scheduled for cardiac surgery with CPB were included. Bone marrow and blood samples were harvested before, during, and after surgery. Neutrophil phenotypic maturation and functions (migration, adhesion, neutrophil extracellular trap [NET] release, reactive oxygen species (ROS) production, phagocytosis, and bacteria killing) were investigated. Two types of Staphylococcus aureus strains (one from asymptomatic nasal carriage and another from mediastinitis infected tissues) were used to assess in vitro bacterial direct impact on neutrophils. We found that CPB induced a systemic inflammation with an increase in circulating mature neutrophils after surgery. Bone marrow sample analysis did not reveal any modification of neutrophil maturation during CPB. Neutrophil lifespan was significantly increased and functions such as NET release and ROS production were enhanced after CPB whereas bacteria killing and phagocytosis were not impacted. Results were similar with the two different isolates of Staphylococcus aureus. These data suggest that CPB induces a recruitment of mature neutrophils via a demargination process rather than impacting their maturation in the bone marrow. In addition, neutrophils are fully efficient after CPB and do not contribute to postoperative immunosuppression.

Follicular lymphoma dynamics

Follicular lymphoma (FL) is an indolent yet challenging disease. Despite a generally favorable response to immunochemotherapy regimens, a fraction of patients does not respond or relapses early with unfavorable prognosis. For the vast majority of those who initially respond, relapses will repeatedly occur with increasing refractoriness to available treatments. Addressing the clinical challenges in FL warrants deep understanding of the nature of treatment-resistant FL cells seeding relapses, and of the biological basis of early disease progression. Great progress has been made in the last decade in the description and interrogation of the (epi)genomic landscape of FL cells, of their major dependency to the tumor microenvironment (TME), and of the stepwise lymphomagenesis process, from healthy to subclinical disease and to overt FL. A new picture is emerging, in which an ever-evolving tumor-TME duo sparks a complex and multilayered clonal and functional heterogeneity, blurring the discovery of prognostic biomarkers, patient stratification and reliable designs of risk-adapted treatments. Novel technological approaches allowing to decipher both tumor and TME heterogeneity at the single-cell level are beginning to unravel unsuspected cell dynamics and plasticity of FL cells. The upcoming drawing of a comprehensive functional picture of FL within its ecosystem holds great promise to address the unmet medical needs of this complex lymphoma.

Consensus International Council for Commonality in Blood Banking Automation-International Society for Cell & Gene Therapy statement on standard nomenclature abbreviations for the tissue of origin of mesenchymal stromal cells

The Cellular Therapy Coding and Labeling Advisory Group of the International Council for Commonality in Blood Banking Automation and the International Society for Cell & Gene Therapy mesenchymal stromal cell (MSC) committee are providing specific recommendations on abbreviating tissue sources of culture-adapted MSCs. These recommendations include using abbreviations based on the ISBT 128 terminology model that specifies standard class names to distinguish cell types and tissue sources for culture-adapted MSCs. Thus, MSCs from bone marrow are MSC(M), MSCs from cord blood are MSC(CB), MSCs from adipose tissue are MSC(AT) and MSCs from Wharton's jelly are MSC(WJ). Additional recommendations include using these abbreviations through the full spectrum of pre-clinical, translational and clinical research for the development of culture-adapted MSC products. This does not apply to basic research focused on investigating the developmental origins, identity or functionalities of endogenous progenitor cells in different tissues. These recommendations will serve to harmonize nomenclature in describing research and development surrounding culture-adapted MSCs, many of which are destined for clinical and/or commercial translation. These recommendations will also serve to align research and development efforts on culture-adapted MSCs with other cell therapy products.

B cell/stromal cell crosstalk in health, disease, and treatment: Follicular lymphoma as a paradigm

Stromal cells organize specific anatomic compartments within bone marrow (BM) and secondary lymphoid organs where they finely regulate the behavior of mature normal B cells. In particular, lymphoid stromal cells (LSCs) form a phenotypically heterogeneous compartment including various cell subsets variably supporting B-cell survival, activation, proliferation, and differentiation. In turn, activated B cells trigger in-depth remodeling of LSC networks within lymph nodes (LN) and BM. Follicular lymphoma (FL) is one of the best paradigms of a B-cell neoplasia depending on a specific tumor microenvironment (TME), including cancer-associated fibroblasts (CAFs) emerging from the reprogramming of LN LSCs or poorly characterized local BM precursors. FL-CAFs support directly malignant B-cell growth and orchestrate FL permissive cell niche by contributing, through a bidirectional crosstalk, to the recruitment and polarization of immune TME subsets. Recent studies have highlighted a previously unexpected level of heterogeneity of both FL B cells and FL TME, underlined by FL-CAF plasticity. A better understanding of the signaling pathways, molecular mechanisms, and kinetic of stromal cell remodeling in FL would be useful to delineate new predictive markers and new therapeutic approaches in this still fatal malignancy.

Comparative immune profiling of acute respiratory distress syndrome patients with or without SARS-CoV-2 infection

Acute respiratory distress syndrome (ARDS) is the main complication of coronavirus disease 2019 (COVID-19), requiring admission to the intensive care unit (ICU). Despite extensive immune profiling of COVID-19 patients, to what extent COVID-19-associated ARDS differs from other causes of ARDS remains unknown. To address this question, here, we build 3 cohorts of patients categorized in COVID-19⁻ARDS⁺, COVID-19⁺ARDS⁺, and COVID-19⁺ARDS⁻, and compare, by high-dimensional mass cytometry, their immune landscape. A cell signature associating S100A9/calprotectin-producing CD169⁺ monocytes, plasmablasts, and Th1 cells is found in COVID-19⁺ARDS⁺, unlike COVID-19⁻ARDS⁺ patients. Moreover, this signature is essentially shared with COVID-19⁺ARDS⁻ patients, suggesting that severe COVID-19 patients, whether or not they experience ARDS, display similar immune profiles. We show an increase in CD14⁺HLA-DR^low and CD14^lowCD16⁺ monocytes correlating to the occurrence of adverse events during the ICU stay. We demonstrate that COVID-19-associated ARDS displays a specific immune profile and may benefit from personalized therapy in addition to standard ARDS management.

Machine-learning analysis of CyTOF data segregates COVID-19⁺ and COVID-19⁻ ARDS

CD169⁺S100A9⁺ monocytes differentiate COVID-19 ARDS from other ARDS

Monocyte compartment alterations correlate with other immune subset modifications

CD14⁺HLA-DR^low and CD14^loCD16⁺ monocytes are markers of adverse COVID-19 evolution

Mass Cytometry Identifies Expansion of T-bet+ B Cells and CD206+ Monocytes in Early Multiple Sclerosis

Multiple sclerosis (MS) is an immune-driven demyelinating disease of the central nervous system. Immune cell features are particularly promising as predictive biomarkers due to their central role in the pathogenesis but also as drug targets, even if nowadays, they have no impact in clinical practice. Recently, high-resolution approaches, such as mass cytometry (CyTOF), helped to better understand the diversity and functions of the immune system. In this study, we performed an exploratory analysis of blood immune response profiles in healthy controls and MS patients sampled at their first neurological relapse, using two large CyTOF panels including 62 markers exploring myeloid and lymphoid cells. An increased abundance of both a T-bet-expressing B cell subset and a CD206⁺ classical monocyte subset was detected in the blood of early MS patients. Moreover, T-bet-expressing B cells tended to be enriched in aggressive MS patients. This study provides new insights into understanding the pathophysiology of MS and the identification of immunological biomarkers. Further studies will be required to validate these results and to determine the exact role of the identified clusters in neuroinflammation.

Mesenchymal stromal cell variables influencing clinical potency: the impact of viability, fitness, route of administration and host predisposition

The International Society for Cell & Gene Therapy mesenchymal stromal cell (MSC) committee has been an interested observer of community interests in all matters related to MSC identity, mechanism of action, potency assessment and etymology, and it has regularly contributed to this conversation through a series of MSC pre-conferences and committee publications dealing with these matters. Arising from these reflections, the authors propose that an overlooked and potentially disruptive perspective is the impact of in vivo persistence on potency that is not predicted by surrogate cellular potency assays performed in vitro and how this translates to in vivo outcomes. Systemic delivery or extravascular implantation at sites removed from the affected organ system seems to be adequate in affecting clinical outcomes in many pre-clinical murine models of acute tissue injury and inflammatory pathology, including the recent European Medicines Agency-approved use of MSCs in Crohn-related fistular disease. The authors further propose that MSC viability and metabolic fitness likely dominate as a potency quality attribute, especially in recipients poised for salutary benefits as defined by emerging predictive biomarkers of response.

Venoarterial extracorporeal membrane oxygenation induces early immune alterations

Background

Venoarterial extracorporeal membrane oxygenation (VA-ECMO) provides heart mechanical support in critically ill patients with cardiogenic shock. Despite important progresses in the management of patients under VA-ECMO, acquired infections remain extremely frequent and increase mortality rate. Since immune dysfunctions have been described in both critically ill patients and after surgery with cardiopulmonary bypass, VA-ECMO initiation may be responsible for immune alterations that may expose patients to nosocomial infections (NI). Therefore, in this prospective study, we aimed to study immune alterations induced within the first days by VA-ECMO initiation.

Methods

We studied immune alterations induced by VA-ECMO initiation using cytometry analysis to characterize immune cell changes and enzyme-linked immunosorbent assay (ELISA) to explore plasma cytokine levels. To analyze specific changes induced by VA-ECMO initiation, nine patients under VA-ECMO (VA-ECMO patients) were compared to nine patients with cardiogenic shock (control patients).

Results

Baseline immune parameters were similar between the two groups. VA-ECMO was associated with a significant increase in circulating immature neutrophils with a significant decrease in C5a receptor expression. Furthermore, we found that VA-ECMO initiation was followed by lymphocyte dysfunction along with myeloid-derived suppressor cells (MDSC) expansion. ELISA analysis revealed that VA-ECMO initiation was followed by an increase in pro-inflammatory cytokines such as IL-6, IL-8 and TNF-α along with IL-10, a highly immunosuppressive cytokine.

Conclusion

VA-ECMO is associated with early immune changes that may be responsible for innate and adaptive immune alterations that could confer an increased risk of infection.

SARS-CoV-2-Induced ARDS Associates with MDSC Expansion, Lymphocyte Dysfunction, and Arginine Shortage

Purpose

The SARS-CoV-2 infection can lead to a severe acute respiratory distress syndrome (ARDS) with prolonged mechanical ventilation and high mortality rate. Interestingly, COVID-19-associated ARDS share biological and clinical features with sepsis-associated immunosuppression since lymphopenia and acquired infections associated with late mortality are frequently encountered. Mechanisms responsible for COVID-19-associated lymphopenia need to be explored since they could be responsible for delayed virus clearance and increased mortality rate among intensive care unit (ICU) patients.

Methods

A series of 26 clinically annotated COVID-19 patients were analyzed by thorough phenotypic and functional investigations at days 0, 4, and 7 after ICU admission.

Results

We revealed that, in the absence of any difference in demographic parameters nor medical history between the two groups, ARDS patients presented with an increased number of myeloid-derived suppressor cells (MDSC) and a decreased number of CD8^pos effector memory cell compared to patients hospitalized for COVID-19 moderate pneumonia. Interestingly, COVID-19-related MDSC expansion was directly correlated to lymphopenia and enhanced arginase activity. Lastly, T cell proliferative capacity in vitro was significantly reduced among COVID-19 patients and could be restored through arginine supplementation.

Conclusions

The present study reports a critical role for MDSC in COVID-19-associated ARDS. Our findings open the possibility of arginine supplementation as an adjuvant therapy for these ICU patients, aiming to reduce immunosuppression and help virus clearance, thereby decreasing the duration of mechanical ventilation, nosocomial infection acquisition, and mortality.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10875-020-00920-5.

Integrative Analysis of Cell Crosstalk within Follicular Lymphoma Cell Niche: Towards a Definition of the FL Supportive Synapse

Simple Summary

Follicular lymphoma, the most frequent indolent non-Hodgkin’s B cell lymphoma, arises from a germinal center B cell proliferation supported by a multidirectional crosstalk with the tumor microenvironment, in particular with follicular helper T cells and mesenchymal stromal cells. Here, we explored this complex network, starting from a comparative analysis of the molecular signatures of B cells, T cells, and stromal cells obtained from normal versus lymphoma tissues, and focusing on deregulated genes reflecting the crosstalk between these three cell subsets organizing the lymphoma cell niche. This helps us to point out new lymphoma-specific pathways, related to transcriptomic and functional specific features of T and stromal cells, and contributing to tumor B cell support directly or through the recruitment and/or activation of other pro-tumoral cell components. In the future, targeting these cell interactions with specific drugs in the FL niche could represent an attractive option for novel therapeutic strategies.

Abstract

Follicular lymphoma (FL), the most frequent indolent non-Hodgkin’s B cell lymphoma, is considered as a prototypical centrocyte-derived lymphoma, dependent on a specific microenvironment mimicking the normal germinal center (GC). In agreement, several FL genetic alterations affect the crosstalk between malignant B cells and surrounding cells, including stromal cells and follicular helper T cells (Tfh). In our study, we sought to deconvolute this complex FL supportive synapse by comparing the transcriptomic profiles of GC B cells, Tfh, and stromal cells, isolated from normal versus FL tissues, in order to identify tumor-specific pathways. In particular, we highlighted a high expression of IL-6 and IL-7 in FL B cells that could favor the activation of FL Tfh overexpressing IFNG, able in turn to stimulate FL B cells without triggering MHC (major histocompatibility) class II expression. Moreover, the glycoprotein clusterin was found up-regulated in FL stromal cells and could promote FL B cell adhesion. Finally, besides its expression on Tfh, CD200 was found overexpressed on tumor B cells and could contribute to the induction of the immunosuppressive enzyme indoleamine-2,3 dioxygenase by CD200R-expressing dendritic cells. Altogether our findings led us to outline the contribution of major signals provided by the FL microenvironment and their interactions with malignant FL B cells.

Human Lymphoid Stromal Cells Contribute to Polarization of Follicular T Cells Into IL-4 Secreting Cells

Fibroblastic reticular cells (FRCs) are the specialized lymphoid stromal cells initially identified as triggering T-cell recruitment and dynamic motion in secondary lymphoid organs. Interestingly, FRCs also display antigen presentation capacities and support lymphocyte survival. CXCR5⁺CD4⁺ follicular T cells are important players of B-cell maturation and antibody response. Our study reported that in vitro-differentiated FRC-like cells enhanced the growth of the whole CXCR5⁺CD4⁺ T-cell compartment, while enhancing IL-4 secretion specifically by the PD1^dimCXCR5⁺CD4⁺ cell subset, in a Notch- and ICAM1/LFA1-dependent manner. In addition, we revealed that in follicular lymphoma (FL) tissues, previously identified as enriched for PD1^hiCXCR5^hiCD4⁺ mature follicular helper T cells, PD1^dimCXCR5⁺CD4⁺ T cells displayed an enrichment for Notch and integrin gene signatures, and a Notch and ICAM-1-dependent overexpression of IL-4 compared to their non-malignant counterparts. These findings suggest that the crosstalk between FRCs and CXCR5⁺PD1^dimCD4⁺ T cells may contribute to the FL IL-4 rich environment, thus providing new insights in FL lymphomagenesis.