Clinical & Translational Immunology

This manuscript has been withdrawn by the authors as it was submitted and made public without appropriate approval. Therefore, the authors do not wish this work to be cited as reference for the project. If you have any questions, please contact the corresponding author.

A better understanding of sepsis-induced immunosuppression pathophysiology is desirable for the development of novel therapeutic strategies to prevent and reduce the rates of secondary infections and their associated mortality. Here we demonstrate that PD-L1+CD44+B220LowCD138+IgM+ regulatory plasma cells (PCs) are induced in a murine model of sepsis-induced immune alterations and in critically ill patients with bacterial sepsis and COVID-19. This was revealed both by detailed analysis of their phenotypical features and gene expression profile and by functional explorations comparing capacity of purified B cells and PCs to suppress T cell proliferation and IFN{gamma} secretion ex vivo. Sepsis-induced regulatory PCs exerted their suppressive function on T cells through IL-10 production and increased PD-L1 expression independently of regulatory T cells. Our findings thus reveal a novel pathophysiological mechanism of sepsis-induced immunosuppression that involves regulatory PCs. As such, these PCs constitute valid therapeutic targets to improve immune cell functions impaired by sepsis.

During pregnancy, the human placenta establishes tolerance toward fetal allogeneic tissue, where specialized trophoblast subtypes play a complex role in local and peripheral immunomodulation. However, due to inadequate models to study the early gestation of the human placenta, each trophoblast subtypes role in modulating the maternal immune response has remained elusive. Here, we derived human placental organoids from early gestation trophoblast stem cells to (1) identify patterns of immunomodulatory protein expression by trophoblast subtype and (2) evaluate the effects of the placental organoid secretome on immune cell activation and regulation. We show that the three primary trophoblast phenotypes had distinct influences on immune cell phenotype and activation and that three-dimensional culture significantly alters trophoblast immunomodulation relative to traditional two-dimensional trophoblast culture.

This manuscript has been withdrawn as it was submitted and made public without the full consent of all the authors. Therefore, the authors do not wish this work to be cited as reference for the project. If you have any questions, please contact the corresponding author.

PurposeSepsis-associated immunothrombosis significantly contributes to high mortality, yet the role of N-glycosylation in this process remains poorly understood. This study aimed to comprehensively profile the plasma N-glycosylation landscape in sepsis and elucidate how its specific reprogramming in the complement and coagulation cascades influences immunothrombotic balance and patient outcomes. MethodsWe performed in-depth 4D-DIA proteomic and N-glycomic analyses on plasma from 43 sepsis patients and 9 healthy controls. Differential expression, weighted gene co-expression network analysis (WGCNA), and protein-glycosylation correlation analyses were used to characterize molecular features. Clinical relevance was assessed via correlation and survival analyses. ResultsExtensive N-glycosylation reprogramming was observed in sepsis plasma,with marked enrichment in complement and coagulation pathways(KEGG p=7.76x10- {superscript 2}{superscript 1}).Pro-coagulant proteins(eg,vWF,fibrinogen)showed increased abundance together with enhanced site-specific glycosylation,potentially amplifying their activity.In contrast,key anticoagulant proteins(eg,SERPINC1)displayed unchanged glycosylation at critical sites despite abundance changes,which may impair function.Survival analysis revealed distinct prognostic values of glycoproteins and specific glycosylation sites.For instance,high vWF protein levels predicted mortality(HR=2.83),whereas elevated glycosylation at vWF N211 was associated with improved survival(HR=0.135),suggesting a negative regulatory role.These glycosylation markers correlated closely with disease severity and prognosis,representing potential early-warning biomarkers independent of current clinical coagulation indicators. ConclusionOur study demonstrates widespread reprogramming of the plasma proteome and N-glycome in sepsis.We propose that decoupling of protein function from abundance through N-glycosylation in the complement-coagulation network contributes to immunothrombotic imbalance.Specific N-glycosylation sites may serve as novel prognostic biomarkers,offering new perspectives for early risk stratification and glycosylation-targeted therapies in sepsis. Key PointsO_LISepsis plasma exhibits specific N-glycosylation reprogramming overwhelmingly focused on the complement and coagulation cascade. C_LIO_LIA dominant "glycosylation-dominated co-upregulation" mode in procoagulant factors, coupled with a "silent" glycosylation state in key anticoagulants, drives prothrombotic imbalance. C_LIO_LISite-specific N-glycosylation levels provide prognostic information distinct from, and often superior to, their carrier protein abundance, offering novel early-risk biomarkers. C_LI

Primary Epstein-Barr virus (EBV) infection can lead to post-transplantation lymphoproliferative disorder (PTLD) following renal transplantation (RTx). Despite EBV-driven PTLD (ePTLD) being rare, it is potentially lethal. CD8+ T-cells play a crucial role in controlling viral infections and malignant transformation of cells. We therefore hypothesized that aberrant EBV-specific CD8+ T cell maturation may contribute to ePTLD development. We performed multichannel flow cytometry on MHC class I tetramer-isolated EBV-specific CD8+ T-cells targeting lytic EBV BZLF1/BMLF1 and latent LMP2 proteins. This pilot study characterized differentiation markers, cytotoxicity, and inhibitory receptor expression in circulating EBV-specific CD8 T cells from renal transplant recipients (RTRs) with primary EBV infection and those who developed ePTLD, and compared them to RTRs with latent (inactive) EBV infection and healthy individuals (HIs). We demonstrated that RTRs with primary EBV infection display adequate cellular proliferation, development of effector memory differentiation, and expression of granzyme B and K (GrmB and K) despite immunosuppression. RTRs who developed ePTLD showed a delayed seroconversion, an early viral load peak, and altered effector-memory differentiation.

Epstein-Barr virus (EBV)-associated central nervous system lymphoproliferative diseases (CNSL) are aggressive clinical conditions with poor prognosis. We have reported that durable responses in patients with primary CNS post-transplant lymphoproliferative disease (PTLD) were associated with detection of two ganciclovir (GCV)/zidovudine (AZT) viral drug target proteins, the EBV kinases BGLF4 and BXLF1 in CNSL biopsies. These are associated with lytic EBV and the mechanism for expression in latently infected EBV+ CNSL has been unknown. By carrying out RNA expression analysis in CNSL tissue biopsies (n=12), we confirmed expression of LMP1, BXLF1, and BGLF4, but not BZLF1, pointing to an incomplete lytic EBV program. Biopsies from systemic PTLD (n=24) were used for comparison and showed significantly less expression of BGLF4. By quantifying DNA methylation in EBV gene promoters we showed significantly decreased promoter methylation at BGLF4 in CNSL versus systemic PTLD (p=0.0006). Luciferase reporter analysis of the BGLF4 upstream sequence revealed 3 regions of promoter activity and 5' RACE in n=4 EBV-infected cell lines and n=5 CNSL biopsy samples identified transcription start sites at these promoters. We identified DNA methylation loss at single CpG dinucleotides which were specifically demethylated in CNSL, while surrounding EBV methylation remained high. Lastly, TET2 knockout and expression of TET1/2-suppressive mutant IDH1 in a latent HEK293 EBV model indicated that active demethylation is necessary for activity of BGLF4 promoters. We detail the epigenetic basis of BGLF4 expression in CNSL via locus-specific promoter activation that may hold value for determination of antiviral drug sensitivity. SignificanceWe show site-specific DNA methylation loss as the molecular basis of BGLF4 expression in CNSL. BGLF4 methylation holds potential for further development as a biomarker of antiviral drug response in EBV+ CNSL.

The prevalence and persistence of adaptive immunity responses following a SARS-CoV-2 infection provides insights into potential population immunity. Adaptive immune responses comprise of antibody-based responses as well as T cell responses mainly addressing viruses and virus-infected human cells, respectively. A comprehensive analysis of both types of adaptive immunity is essential to follow population-based SARS-CoV-2-specific immunity. In this study, we assessed SARS-CoV-2-specific immunoglobulin A (IgA) levels, SARS-CoV-2-specific immunoglobulin G (IgG) levels, and SARS-CoV-2-specific T cell activities in patients who recovered from a COVID-19 infection in spring and autumn 2020. Here we observed a robust and stable SARS-CoV-2-specific adaptive immune response in both groups with persisting IgA and IgG levels as well as stable T cell activity. Moreover, there was a positive correlation of a lasting immune response with the severity of disease. Our data give evidence for a persisting adaptive immune memory, which suggest a continuing immunity for more than six months post infection.

BackgroundCovid-19, the disease caused by infection with SARS-CoV-2, has developed to a pandemic causing more than 239, 000 deaths worldwide as of 6th May according to the World Health Organization (WHO). It presents with a highly variable disease course ranging from a large proportion of asymptomatic cases to severe respiratory failure in 17-29% of cases even in the absence of apparent comorbidities 1, 2. This implies a diverse host immune response to SARS-CoV-2. The immunological characteristics underlying these divergent disease courses, however, still remain elusive. While insights into abrogations of innate immunity begin to emerge, adaptive immune responses towards SARS-CoV-2 are poorly investigated, although they serve as immune signatures of protection and vaccine responses. We therefore set out to characterize immune signatures of convalescent COVID-19 patients stratified according to their disease severity. MethodsWe performed high-dimensional flow cytometric profiling of peripheral blood mononuclear cells of convalescent COVID-19 patients who we stratified according to their disease severity by a physician-assisted questionnaire based assessment of COVID-19 symptoms. ResultsSurprisingly, we did not observe any difference in the relative proportions of any major immune cell type in convalescent patients presenting with different severity of COVID-19 disease except for a reduction in monocytes. The frequency of Tnaive T cells was significantly reduced in CD4+ and CD8+ T cells, whereas other T cell differentiations states (TCM, TEM, TEMRA) remained relatively unaffected by COVID-19 severity as assessed approximately two weeks after infection. ConclusionsIn our COVID-19 patient cohort, which is characterized by absence of comorbidities and therapeutic interventions other than symptomatic antipyretics, the immunophenotype is similar irrespective of a highly variable disease severity. Convalescence is therefore associated with a rather uniform immune signature. Abrogations, which were previously identified in the innate and adaptive immune compartment of COVID-19 patients should be scrutinized for direct associations with a preconditioned immune system shaped and made vulnerable for SARS-CoV-2 by preexisting comorbidities.

BackgroundChildren are less clinically affected by SARS-CoV-2 infection than adults with the majority of cases being mild or asymptomatic and the differences in infection outcomes are poorly understood. The kinetics, magnitude and landscape of the antibody response may impact the clinical severity and serological diagnosis of COVID-19. Thus, a comprehensive investigation of the antibody landscape in children and adults is needed. MethodsWe tested 254 plasma from 122 children with symptomatic and asymptomatic SARS-CoV-2 infections in Hong Kong up to 206 days post symptom onset, including 146 longitudinal samples from 58 children. Adult COVID-19 patients and pre-pandemic controls were included for comparison. We assessed antibodies to a 14-wide panel of SARS-CoV-2 structural and accessory proteins by Luciferase Immunoprecipitation System (LIPS). FindingsChildren have lower levels of Spike and Nucleocapsid antibodies than adults, and their cumulative humoral response is more expanded to accessory proteins (NSP1 and Open Reading Frames (ORFs)). Sensitive serology using the three N, ORF3b, ORF8 antibodies can discriminate COVID-19 in children. Principal component analysis revealed distinct serological signatures in children and the highest contribution to variance were responses to non-structural proteins ORF3b, NSP1, ORF7a and ORF8. Longitudinal sampling revealed maintenance or increase of antibodies for at least 6 months, except for ORF7b antibodies which showed decline. It was interesting to note that children have higher antibody responses towards known IFN antagonists: ORF3b, ORF6 and ORF7a. The diversified SARS-CoV-2 antibody response in children may be an important factor in driving control of SARS-CoV-2 infection.

Most humans have been infected by Cytomegalovirus (CMV) by the time they reach forty years of age. Whereas most of these CMV infections are well controlled by the immune system, congenital infection can lead to serious health effects and death for the fetus and neonate. With clear evidence that risk to the fetus is lower during chronic maternal infection, and varies in association with gestational age at the time of primary maternal infection, further research on humoral immune responses to primary CMV infection during pregnancy is needed. Here, systems serology tools were applied to characterize antibody responses to CMV infection among pregnant and non-pregnant women experiencing either primary or chronic infection. Whereas strikingly different antibody profiles were observed depending on infection status, more limited differences were associated with pregnancy status. Beyond known differences in IgM responses that are used clinically for identification of primary infection, distinctions observed in IgA and Fc{gamma}R binding antibody responses and among viral antigen specificities accurately predicted infection status in a cross-sectional cohort. Leveraging machine learning, longitudinal samples were also used to define an immunological clock of CMV infection from primary to chronic states and predict time since primary infection with high accuracy. Humoral responses diverged over time in an antigen-specific manner, with IgG3 responses toward tegument decreasing over time as is typical of viral infections, while those directed to pentamer and glycoprotein B were lower during acute and greatest during chronic infection. In sum, this work provides new insights into the antibody response associated with CMV infection status in the context of pregnancy, revealing aspects of humoral immunity that have the potential to improve CMV diagnostics and to support clinical trials of interventions to reduce mother-to-fetus transmission of CMV.

Despite vaccination and antiviral therapies, immunocompromised individuals are at risk for prolonged SARS-CoV-2 infection, but the immune defects that predispose to persistent COVID-19 remain incompletely understood. In this study, we performed detailed viro-immunologic analyses of a prospective cohort of participants with COVID-19. The median time to nasal viral RNA and culture clearance in the severe hematologic malignancy/transplant group (S-HT) were 72 and 40 days, respectively, which were significantly longer than clearance rates in the severe autoimmune/B-cell deficient (S-A), non-severe, and non-immunocompromised groups (P<0.001). Participants who were severely immunocompromised had greater SARS-CoV-2 evolution and a higher risk of developing antiviral treatment resistance. Both S-HT and S-A participants had diminished SARS-CoV-2-specific humoral, while only the S-HT group had reduced T cell-mediated responses. This highlights the varied risk of persistent COVID-19 across immunosuppressive conditions and suggests that suppression of both B and T cell responses results in the highest contributing risk of persistent infection.

BackgroundThe fetal immune system undergoes pivotal development during gestation, preparing for postnatal antigenic challenges. Bacterial extracellular vesicles (bEVs), bioactive particles shed by bacteria, are emerging as modulators of host immunity. However, their role in shaping fetal intestinal immune development remains largely unexplored. ObjectivesThis study aimed to investigate the effects of bEV exposure on lymphoid and myeloid populations in the fetal murine gut, focusing on their role in priming intestinal immunity, promoting differentiation, and modulating immune cell phenotypes in both normal and germ-free (GF) environments. Materials and MethodsWe used a murine model to evaluate the immune-modulating effects of bEVs during fetal development. bEVs were isolated from bacterial cultures and introduced into the amniotic sac of embryonic day 15.5 (E15.5) fetuses through intra-amniotic injection. Fetal and neonatal mice were either raised under conventional conditions (normal environment, NE) or in germ-free (GF) environments to assess microbiota-dependent effects. Immune profiling of fetal (E17) and postnatal (4 weeks) gut tissues was performed using high-dimensional mass cytometry (CyTOF) in both conventionally housed and germ-free (GF) mice. Clustering and differential expression analyses identified lymphoid and myeloid subpopulations, including progenitors, antigen-presenting cells, and intestinal stem cells (ISCs). secondary immune challenge (LPS or TSST-1) was conducted in postnatal bEV-primed mice to assess immune memory responses. ResultsbEV exposure significantly increased the prevalence of CD45- CD24+ CD44+ ISCs, promoting intestinal renewal and defense via differentiation into Paneth and tuft cells. These ISCs exhibited potential antigen-presenting capabilities through MHC expression. CD45+ lymphoid progenitors were upregulated, highlighting their role in early differentiation pathways. Myeloid progenitors, particularly monocyte-dendritic progenitor subsets, showed a bias toward antigen-presenting phenotypes.Germ-free models revealed heightened sensitivity to bEVs, with pronounced activation of progenitors and a reduction in exhaustion markers. Interestingly, macrophage and neutrophil populations displayed dose-dependent modulation, with low bEV concentrations promoting their expansion and higher doses leading to reduced incidence. Our findings suggest that bEVs act as immune priming agents in the fetal gut, promoting progenitor expansion and differentiation while preparing the intestine for postnatal challenges. Differences in responses between NE and GF models emphasize the importance of environmental influences, including microbiota, on bEV-mediated immune modulation. ConclusionbEVs play a pivotal role in shaping fetal intestinal immunity by priming lymphoid and myeloid progenitors and enhancing ISC function. These results open potential avenues for leveraging bEVs in immunomodulation and vaccine strategies. Future studies should explore the functional responses of bEV-primed cells and their translational relevance in humans.

Recently, unexpectedly high virus-specific IgG4 levels were reported after more than two mRNA vaccinations. Class switch towards IgG4 occurs after long-term antigen exposure, downregulates immune responses and is associated with several autoimmune diseases. Here, we examined differences in antigen-specific IgG subtypes in serum samples from 64 Post-COVID patients and an equally sized cohort of convalescent controls. In both cohorts, the relative amounts of spike protein-specific IgG subtypes were comparable. IgG1 was the most frequent, followed by IgG3, IgG2, and IgG4. A difference between cohorts was observed only for IgG2, which was significantly lower in the Post-COVID cohort. Further analysis of the reactive IgG4 revealed a small but significant difference for the spike protein receptor-binding domain but not for the spike ectodomain. Since the total IgG4 levels are very low, we do not expect a biologically relevant role in Post-COVID syndrome. However, reduced virus-specific IgG2 levels could contribute to the persistence of SARS-CoV-2, causing chronic inflammation in the setting of Post-COVID syndrome.

Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and is associated with a wide range of systemic manifestations. Several observations support a role for vascular endothelial dysfunction in the pathogenesis including an increased incidence of thrombotic events and coagulopathy and the presence of vascular risk factors as an independent predictor of poor prognosis. It has recently been reported that endothelitis is associated with viral inclusion bodies suggesting a direct role for SARS-CoV-2 in the pathogenesis. The ACE2 receptor has been shown to mediate SARS-CoV-2 uptake and it has been proposed that CD147 (BSG) can function as an alternative cell surface receptor. To define the endothelial cell populations that are susceptible to infection with SARS-CoV-2, we investigated the expression of ACE2 as well as other genes implicated in the cellular entry of SARS-Cov-2 in the vascular endothelium through the analysis of single cell sequencing data derived from multiple human tissues (skin, liver, kidney, lung and intestine). We found that CD147 (BSG) but not ACE2 is detectable in vascular endothelial cells within single cell sequencing datasets derived from multiple tissues in healthy individuals. This implies that either ACE2 is not expressed in healthy tissue but is instead induced in response to SARS-Cov2 or that SARS-Cov2 enters endothelial cells via an alternative receptor such as CD147.

Outcomes following SARS-CoV-2 infection are variable; whilst the majority of patients recover without serious complications, a subset of patients develop prolonged illness termed Long COVID or post-acute sequelae of SARS-CoV-2 infection (PASC). The pathophysiology underlying Long COVID remains unclear but appears to involve multiple mechanisms including persistent inflammation, coagulopathy, autoimmunity, and organ damage. Studies suggest that microclots, also known as fibrinaloids, play a role in Long COVID. In this context, we developed a method to quantify microclots and investigated the relationship between microclot counts and Long COVID. We show that as a cohort, platelet-poor plasma from Long COVID samples had a higher microclot count compared to control groups but retained a wide distribution of counts. Recent COVID-19 infections were also seen to be associated with microclot counts higher than the control groups and equivalent to the Long COVID cohort, with a subsequent time-dependent reduction of counts. Our findings suggest that microclots could be a potential biomarker of disease and/or a treatment target in some Long COVID patients.

Lymphatic vessels are formed during embryonic and postnatal development to facilitate interstitial fluid clearance and immune regulation after birth. Their organ-specific heterogeneity in organisation and function is preceded by heterogenous origins of lymphatic endothelial cells (LECs), the main building blocks of lymphatic vessels. In the dermis, a subset of LECs was reported to arise from blood capillaries, which themselves differentiate, in part, from paraxial mesoderm. However, it is not known whether additional cell lineages contribute to the dermal LEC population. Here, we have combined transcriptomic analyses with genetic lineage tracing and wholemount immunostaining to show that 60% of LECs in the embryonic day (E) 13.5 and E15.5 dermis are derived from a cell lineage that expresses Csf1r, a marker of myeloid cells and their progeny. Csf1r lineage LECs persist in adult dermal lymphatic vasculature and are indispensable for normal lymphatic development, because Prox1 deletion within the Csf1r lineage causes dermal oedema and blood-filled lymphatic vessels. As Csf1r lineage dermal LECs do not themselves express Csf1r and also do not arise from Csf1r-expressing differentiated myeloid cells, our findings imply the existence of a Csf1r-expressing non-LEC precursor population for the majority of dermal LECs and will prompt further work to identify this cell population.

Increasing evidence suggests that autoimmunity may play a role in the pathophysiology of SARS-CoV-2 infection during both the acute and long COVID phases of disease. However, an assessment of autoimmune antibodies in convalescent SARS-CoV-2 patients has not yet been reported. MethodologyWe compared the levels of 18 different IgG autoantibodies (AABs) between four groups: (1) unexposed pre-pandemic subjects from the general population (n = 29); (2) individuals hospitalized with acute moderate-severe COVID-19 (n = 20); (3) convalescent SARS-COV-2-infected subjects with asymptomatic to mild viral symptoms during the acute phase with samples obtained between 1.8 and 7.3 months after infection (n = 9); and (4) unexposed pre-pandemic subjects with systemic lupus erythematous (SLE) (n = 6). Total IgG and IgA levels were also measured from subjects in groups 1-3 to assess non-specific pan-B cell activation. ResultsAs expected, in multivariate analysis, AABs were detected at much higher odds in SLE subjects (5 of 6, 83%) compared to non-SLE pre-pandemic controls (11 of 29, 38%) [odds ratio (OR) 19.4,95% CI, 2.0 - 557.0, p = 0.03]. AAB detection (percentage of subjects with one or more autoantibodies) was higher in SARS-CoV-2 infected convalescent subjects (7 of 9, 78%) [OR 17.4, 95% CI, 2.0 - 287.4, p = 0.02] and subjects with acute COVID-19 (12 of 20, 60%) compared with non-SLE pre-pandemic controls, but was not statistically significant among the latter [OR 1.8,95% CI, 0.6 - 8.1, p = 0.23]. Within the convalescent subject group, AABs were detected in 5/5 with reported persistent symptoms and 2/4 without continued symptoms (p = 0.17). The multivariate computational algorithm Partial Least Squares Determinant Analysis (PLSDA) was used to determine if distinct AAB signatures distinguish subject groups 1-3. Of the 18 autoantibodies measured, anti-Beta 2-Glycoprotein, anti-Proteinase 3-ANCA, anti-Mi-2 and anti-PM/Scl-100 defined the convalescent group; anti-Proteinase 3-ANCA, anti-Mi-2, anti-Jo-1 and anti-RNP/SM defined acute COVID-19 subjects; and anti-Proteinase 3-ANCA, anti-Mi-2, anti-Jo-1, anti-Beta 2-Glycoprotein distinguished unexposed controls. The AABs defining SARS-COV-2 infected from pre-pandemic subjects are widely associated with myopathies, vasculitis, and antiphospholipid syndromes, conditions with some similarities to COVID-19. Compared to pre-pandemic non-SLE controls, subjects with acute COVID-19 had higher total IgG concentration (p-value=0.006) but convalescent subjects did not (p-value=0.08); no differences in total IgA levels were found between groups. ConclusionsOur findings support existing studies suggesting induction of immune responses to self-epitopes during acute, severe COVID-19 with evidence of general B cell hyperactivation. Also, the preponderance of AAB positivity among convalescent individuals up to seven months after infection indicates potential initiation or proliferation, and then persistence of self-reactive immunity without severe initial disease. These results underscore the importance of further investigation of autoimmunity during SARS-CoV-2 infection and its role in the onset and persistence of post-acute sequelae of COVID-19.

Omenn Syndrome (OS) is a rare hematological disorder, caused by hypomorphic mutations in genes involved in B-/T-cell receptor (BCR/TCR) rearrangement that result in impaired lymphocyte development and immunodeficiency. Notwithstanding, few T-cell clones enriched in self-reactive specificities expand in peripheral tissues, where they trigger severe inflammation and autoimmune reactions. Interestingly, residual OS lymphocytes display characteristics proper of embryonic lymphocytes that emerge before, and independently from, hematopoietic stem cells (HSCs). This prompted us to hypothesize whether OS autoreactive T-cells are generated in the embryo independently from HSCs. Here we show that in the Rag2R229Q/R229Q OS mouse model, embryonic but not adult bone marrow-derived hematopoietic progenitors can generate T-cells. T-lymphopoiesis can be rescued in adult OS blood progenitors via their Lin28-mediated reprogramming to an embryonic-like state. Remarkably, when transplanted in immunodeficient mice, embryonic-like OS progenitors trigger tissue morphological alterations and inflammation in the large intestine of the recipients, recapitulating the typical OS inflammatory phenotype. Our study describes the previously unappreciated contribution of embryonic progenitors to the pool of autoreactive infilitrating T-cells, providing a novel platform for both the detailed study of human autoimmune disorders and the design of more targeted therapies.

Neutrophils are innate immune cells with key immunomodulatory functions. In a murine retroviral model, we previously showed their essential role in promoting protective immunity during antiviral antibody therapy via Fc-Fc{gamma} receptor (Fc{gamma}R) interactions. Here, we investigated the immunomodulatory properties of neutrophils in the context of HIV-1 infection and therapy through a comprehensive analysis of their functional activation and the regulation of Fc{gamma}R expression. Neutrophils from healthy donors (HD) and people living with HIV-1 (PLWH) were stimulated with TLR ligands, free HIV-1, immune complexes (ICs) formed with broadly neutralizing antibodies (bNAbs), or pro-inflammatory cytokines (TNF, IFN{gamma}). In response, they secreted various cytokines and chemokines that can recruit and activate immune cells in a stimulus-dependent manner. Compared to TLR agonist and cytokine activation, HD neutrophils showed limited cytokine production in response to free HIV-1 or ICs alone as well as a minimal Fc{gamma}R modulation. However, PLWH neutrophils showed heightened responsiveness to microbial stimuli linked to HIV-1 pathogenesis, secreting higher levels of IFN{gamma}, CXCL1, CCL2, CCL3, and CCL4. They also expressed higher levels of two activating Fc{gamma}Rs (Fc{gamma}RI and Fc{gamma}RIIIb), as well as CD11b, CD63, CXCR4, and PD-L1, indicating an altered activation state. These findings highlight the influence of the inflammatory milieu on neutrophil function and Fc{gamma}R regulation in HIV-1 infection and mAb-based therapies.