CD16+ Monocyte Subset Was Enriched and Functionally Exacerbated in Driving T-Cell Activation and B-Cell Response in Systemic Lupus Erythematosus

The landscape of innate and adaptive immune cell subsets in patients with adult-onset Still's disease

OBJECTIVE

Adult-onset Still's disease (AOSD) is a systemic autoinflammatory disorder. The understanding of the changes in adaptive immune cells and the crosstalk between innate and adaptive immune systems in AOSD is limited. This study aimed to examine the peripheral immune cell composition and inflammatory protein levels in AOSD patients.

METHODS

Twenty-nine active AOSD patients were enrolled. Flow cytometry was used to analyse the cell populations in peripheral blood. Antibody chips were utilized to detect the protein expression profile in serum.

RESULTS

In active AOSD patients, there was an increase in the percentage of classical and non-classical monocytes among peripheral blood mononuclear cells. The proportion of natural killer (NK) cells decreased, with an increase in CD56dim NK1 cells and a decrease in CD56bright NK2 cells compared with healthy controls (HCs). The percentage of naïve central memory T cells was decreased, while the percentage of effector and effector memory T cells was increased among adaptive lymphocytes. The proportion of naïve B and memory B cells was decreased, while plasma cells were increased in AOSD patients, indicating activation of the adaptive immune system. Additionally, the serum levels of 40 proteins were elevated in AOSD patients, primarily involved in cytokine-cytokine receptor interaction, inflammatory response and regulation of mitogen-activated protein kinase cascade.

CONCLUSION

Our findings showed the activation of the innate and adaptive immune system in AOSD. The protein-protein interaction analysis suggested potential communication between innate and adaptive cell subsets. These findings provide new insights into the pathogenesis of the disease and the development of targeted therapies.

Cellular and transcriptional profiles of peripheral blood mononuclear cells pre-vaccination predict immune response to preventative MUC1 vaccine

A single arm trial (NCT007773097) and a double-blind, placebo controlled randomized trial ( NCT02134925 ) were conducted in individuals with a history of advanced colonic adenoma to test the safety and immunogenicity of the MUC1 tumor antigen vaccine and its potential to prevent new adenomas. These were the first two trials of a non-viral cancer vaccine administered in the absence of cancer. The vaccine was safe and strongly immunogenic in 43% (NCT007773097) and 25% ( NCT02134925 ) of participants. The lack of response in a significant number of participants suggested, for the first time, that even in a premalignant setting, the immune system may have already been exposed to some level of suppression previously reported only in cancer. Single-cell RNA-sequencing (scRNA-seq) on banked pre-vaccination peripheral blood mononuclear cells (PBMCs) from 16 immune responders and 16 non-responders identified specific cell types, genes, and pathways of a productive vaccine response. Responders had a significantly higher percentage of CD4+ naive T cells pre-vaccination, but a significantly lower percentage of CD8+ T effector memory (TEM) cells and CD16+ monocytes. Differential gene expression (DGE) and transcription factor inference analysis showed a higher level of expression of T cell activation genes, such as Fos and Jun, in CD4+ naive T cells, and pathway analysis showed enriched signaling activity in responders. Furthermore, Bayesian network analysis suggested that these genes were mechanistically connected to response. Our analyses identified several immune mechanisms and candidate biomarkers to be further validated as predictors of immune responses to a preventative cancer vaccine that could facilitate selection of individuals likely to benefit from a vaccine or be used to improve vaccine responses.

Disease activity drives divergent epigenetic and transcriptomic reprogramming of monocyte subpopulations in systemic lupus erythematosus

OBJECTIVES

Systemic lupus erythematosus (SLE) is characterised by systemic inflammation involving various immune cell types. Monocytes, pivotal in promoting and regulating inflammation in SLE, differentiate from classic monocytes into intermediate and non-classic monocytes, assuming diverse roles and changing their proportions in inflammation. In this study, we investigated the epigenetic and transcriptomic profiles of these and novel monocyte subsets in SLE in relation to activity and progression.

METHODS

We obtained the DNA methylomes and transcriptomes of classic, intermediate, non-classic monocytes in patients with SLE (at first and follow-up visits) and healthy donors. We integrated these data with single-cell transcriptomics of SLE and healthy donors and interrogated their relationships with activity and progression.

RESULTS

In addition to shared DNA methylation and transcriptomic alterations associated with a strong interferon signature, we identified monocyte subset-specific alterations, especially in DNA methylation, which reflect an impact of SLE on monocyte differentiation. SLE classic monocytes exhibited a proinflammatory profile and were primed for macrophage differentiation. SLE non-classic monocytes displayed a T cell differentiation-related phenotype, with Th17-regulating features. Changes in monocyte proportions, DNA methylation and expression occurred in relation to disease activity and involved the STAT pathway. Integration of bulk with single-cell RNA sequencing datasets revealed disease activity-dependent expansion of SLE-specific monocyte subsets, further supported the interferon signature for classic monocytes, and associated intermediate and non-classic populations with exacerbated complement activation.

CONCLUSIONS

Disease activity in SLE drives a subversion of the epigenome and transcriptome programme in monocyte differentiation, impacting the function of different subsets and allowing to generate predictive methods for activity and progression.

Long COVID Definition, Symptoms, Risk Factors, Epidemiology and Autoimmunity: A Narrative Review

The virus called SARS-CoV-2 emerged in 2019 and quickly spread worldwide, causing COVID-19. It has greatly impacted on everyday life, healthcare systems, and the global economy. In order to save as many lives as possible, precautions such as social distancing, quarantine, and testing policies were implemented, and effective vaccines were developed. A growing amount of data collected worldwide allowed the characterization of this new disease, which turned out to be more complex than other common respiratory tract infections. An increasing number of convalescents presented with a variety of nonspecific symptoms emerging after the acute infection. This possible new global health problem was identified and labelled as long COVID. Since then, a great effort has been made by clinicians and the scientific community to understand the underlying mechanisms and to develop preventive measures and effective treatment. The role of autoimmunity induced by SARS-CoV-2 infection in the development of long COVID is discussed in this review. We aim to deliver a description of several conditions with an autoimmune background observed in COVID-19 convalescents, including Guillain-Barré syndrome, antiphospholipid syndrome and related thrombosis, and Kawasaki disease highlighting a relationship between SARS-CoV-2 infection and the development of autoimmunity. However, further studies are required to determine its true clinical significance.

Identifying the causal relationship between immune factors and osteonecrosis: a two-sample Mendelian randomization study

A wealth of evidence intimates a profound connection between the immune system and osteonecrosis, albeit the specific immune factors underlying this connection remain largely veiled. A bidirectional Mendelian randomization (MR) study was conducted based on genome-wide association study summary data to identify causal links between 731 immune factors and osteonecrosis including drug-induced osteonecrosis. Preliminary MR analysis was accomplished utilizing the inverse-variance weighted method under a multiplicative random effects model, and heterogeneity and potential horizontal pleiotropy were evaluated through Cochrane's Q-test, MR-Egger intercept test, MR-PRESSO global test, and leave-one-out analysis. Upon false discovery rate correction, the gene-predicted level of one immune factor (CD62L - monocyte %monocyte) exhibited a significant positive correlation with osteonecrosis, while eight immune traits associated with monocytes, dendritic cells, and NK cells demonstrated significant causal effects with drug-induced osteonecrosis. Reverse MR revealed no significant correlations. This MR research provides genetic evidence for the causal associations between a broad spectrum of immune factors and osteonecrosis. Such a study aids in unraveling the intricate interaction patterns between the immune and skeletal systems, elucidating the pathogenesis of osteonecrosis, and identifying potential novel therapeutic approaches.

ProBDNF contributed to patrolling monocyte infiltration and renal damage in systemic lupus erythematosus

Monocyte aberrations have been increasingly recognized as contributors to renal damage in systemic lupus erythematosus (SLE), however, recognition of the underlying mechanisms and modulating strategies is at an early stage. Our studies have demonstrated that brain-derived neurotrophic factor precursor (proBDNF) drives the progress of SLE by perturbing antibody-secreting B cells, and proBDNF facilitates pro-inflammatory responses in monocytes. By utilizing peripheral blood from patients with SLE, GEO database and spontaneous MRL/lpr lupus mice, we demonstrated in the present study that CX3CR1+ patrolling monocytes (PMo) numbers were decreased in SLE. ProBDNF was specifically expressed in CX3CR1+ PMo and was closely correlated with disease activity and the degree of renal injury in SLE patients. In MRL/lpr mice, elevated proBDNF was found in circulating PMo and the kidney, and blockade of proBDNF restored the balance of circulating and kidney-infiltrating PMo. This blockade also led to the reversal of pro-inflammatory responses in monocytes and a noticeable improvement in renal damage in lupus mice. Overall, the results indicate that the upregulation of proBDNF in PMo plays a crucial role in their infiltration into the kidney, thereby contributing to nephritis in SLE. Targeting of proBDNF offers a potential therapeutic role in modulating monocyte-driven renal damage in SLE.

Utility of peripheral blood monocyte subsets, circulating immune complexes and serum cytokines in assessment of SLE activity: an observational, cross-sectional study

INTRODUCTION

SLE disease measurements by current standards are less than perfect. Monocytes and their subsets are part of innate immunity, and one of our objectives was to look at their role in SLE disease activity. We also looked at the common serum cytokines and the role of circulating immune complex (CIC) estimation in the assessment of disease activity.

METHODS

We conducted a single-centre observational cross-sectional study of SLE patients with active and inactive disease as the comparison arms. Blood samples were collected for (a) peripheral blood monocyte separation and flowcytometric analysis of monocyte subsets based on CD14 and CD16 surface markers, and (b) ELISA for serum cytokines and CIC estimation. Results were analysed in terms of the difference in medians between the active and inactive disease groups using the Mann-Whitney U test (non-normally distributed data).

RESULTS

The absolute monocyte count was lower in the active group than the inactive group (median (IQR) of 329 (228.5) vs. 628 (257)/microliter, p = 0.001). The frequency (%) of the intermediate monocyte subset showed a trend towards an increase in active disease (median (IQR) of 15.10% (9.65) vs. 11.85% (8.00), p = 0.09). It also had a significant positive correlation to the SLEDAI scores (r = 0.33, p = 0.046). The mean fluorescence intensity (MFI) of CD163, expressed primarily by intermediate subsets, was increased, and CD11c MFI was reduced in active disease. Serum TNF-a level was elevated in active disease (median (IQR) of 38 (48.5) pg/ml vs. 9 (48.5) pg/ml, p = 0.042). CIC ELISA at an optimal cut-off of 10 meq/ml provided an area under the curve (AUC) of 0.85 for detecting active SLE.

CONCLUSION

Peripheral blood monocytes are depleted in active disease. The intermediate monocyte subset may have a role in disease activity. TNF-alpha correlated modestly with disease activity. CIC estimation by ELISA may be used in addition to or as an alternative to current standards of laboratory tests for the serological assessment of activity.

Neutrophil extracellular trap-induced intermediate monocytes trigger macrophage activation syndrome in adult-onset Still's disease

BACKGROUND

Adult-onset Still's disease (AOSD) is a systemic autoinflammatory disease characterized by innate immune system activation, with a high risk for macrophage activation syndrome (MAS). MAS development is associated with monocyte/macrophage activation and cytokine storm. Monocytes consist of three different subsets, classical monocytes (CMs, CD14brightCD16 -), intermediate monocytes (IMs, CD14brightCD16 +), and non-classical monocytes (NCMs, CD14dimCD16 +), each has distinct roles in inflammatory regulation. However, the frequencies and regulatory mechanism of monocyte subsets in AOSD patients have not been identified.

METHODS

We performed flow cytometry, RNA sequencing, phagocytosis analysis, and enzyme-linked immunosorbent assay to evaluate monocyte subsets, cell functions, and potential biomarkers. The effect of neutrophil extracellular traps (NETs) on monocytes was determined by evaluating mRNA levels of DNA sensors, surface CD16 expression, and inflammasome pathway activation.

RESULTS

Higher proportions of intermediate monocytes (IMs) were identified in active AOSD patients. IMs displayed higher expression of CD80, CD86, HLA-DR, and CD163 than CMs and NCMs. CD163 upregulation was noted on AOSD IMs, accompanied by increased phagocytic activity and elevated cytokine/chemokine production, including IL-1β, IL-6, CCL8, and CXCL10. The frequencies of IMs were correlated with disease activity and higher in AOSD patients with MAS (AOSD-MAS). CCL8 and CXCL10 were highly expressed in RNA sequencing of monocytes from AOSD-MAS patients and plasma CXCL10 level could serve as a potential biomarker for AOSD-MAS. Moreover, DNA-sensing pathway was activated in monocytes from AOSD-MAS patients. Stimulation with NETs derived from AOSD induced DNA sensor expression, the expansion of IMs, and inflammasome pathway activation. These effects can be abrogated by DNase I treatment.

CONCLUSIONS

Our results demonstrated that the proportions of IMs were elevated in AOSD and associated with MAS. The DNA component in NETs from AOSD plays an important role in the formation of IMs, shedding new light for the therapeutic target.

Assessing the causal relationship between immune traits and systemic lupus erythematosus by bi-directional Mendelian randomization analysis

Previous studies have observed relationships between immune cells and systemic lupus erythematosus (SLE), but their causal links remain undetermined. Based on the public available genome-wide association studies (GWAS) summary statistics, we conducted two-sample Mendelian randomization (MR) to evaluate the associations between 731 immune phenotypes and SLE pairs. Pairwise pleiotropy analysis was performed to identify pleiotropic genes for significant immunophenotype-SLE pairs. A comprehensive gene function analysis was undertaken to explore the mechanisms of immune cells in SLE. By using the instrumental variables extracted from GWAS data, we observed that increased levels of five immune phenotypes were causally associated with SLE risk (FDR < 0.05), that were CD20 on IgD+ CD38- naïve, BAFF-R on IgD+ CD38dim, CD39+ secreting Treg AC, CD14- CD16+ monocyte AC, and HLA DR on CD14+ monocyte. Pairwise gene-based analyses identified a total of 38 pleiotropic genes for 5 significant pairs identified and gene set enrichment analysis revealed the involvement of the identified pleiotropic genes in complex pathways (i.e., systemic lupus erythematosus, an integral component of luminal side of endoplasmic reticulum membrane, C-type lectin receptor signaling pathway and regulation of hormone secretion). This study demonstrates that the immune response influences the progression of SLE in a complex pattern. These findings greatly improve our understanding of the interaction between immune response and SLE risk and also aid in the design of therapeutic strategies from an immunological perspective.

Decreased TAX1BP1 participates in systemic lupus erythematosus by regulating monocyte/macrophage function

Systemic lupus erythematosus (SLE) involves disorders of innate and adaptive immune pathways. Tax1-binding protein 1 (TAX1BP1) modulates the production of antibodies in B cells and the T-cell cycle by regulating the NF-κB signaling pathway. However, the potential association of TAX1BP1 with SLE and its role in monocytes/macrophages have not been fully elucidated. In this study, we utilized whole-exome sequencing (WES) in combination with Sanger sequencing and identified 16 gene mutations, including in TAX1BP1, in an SLE family. TAX1BP1 protein expression with western blotting detection was reduced in SLE patients and correlated with disease activity negatively. Furthermore, RNA sequencing and 4D Label-Free Phosphoproteomic analysis were employed to characterize the transcriptome and phosphoproteome profiles in THP-1 and THP-1-differentiated M1 macrophages with TAX1BP1 knockdown. Silencing of TAX1BP1 in THP-1 and THP-1-differentiated M1 macrophages led to an increase in cluster of differentiation 80 (CD80) expression and differential changes in CD14 and CD16 expression, as assessed by flow cytometry. Additionally, western blot analysis showed that knockdown of TAX1BP1 led to a reduction in TRAF6 and p-p65 in THP-1-differentiated macrophages, with or without lipopolysaccharide (LPS) or tumor necrosis factor (TNF)-α stimulation. Taken together, our findings suggest that TAX1BP1 participates in SLE activity by regulating antigen presentation in monocytes and inflammatory responses in M1 macrophages.

Identification of monocyte-associated biomarkers in systemic lupus erythematosus and their pan-cancer analysis

Immune dysregulation is not only a pathogenic mechanism in systemic lupus erythematosus (SLE) but also a potential cause of the link between SLE and cancer. The current understanding of SLE monocyte-associated biomarkers is limited, and the precise mechanism behind the link between SLE and cancer is uncertain. By using WGCNA and immune infiltration to analyze the GSE72326 dataset, we determined the most pertinent modules for monocytes and discovered eight candidate hub genes from them. The limma software was used to find genes that were differently expressed in SLE. The genes that overlapped between the two were chosen using a Venn diagram as the essential genes related to monocytes in SLE, and the essential genes were verified by several datasets. Correlation analysis and GSEA analysis were used to examine the probable immunological pathways connected to key genes. We examined the expression of hub genes in cancer and their interaction with monocytes using the GEPIA and TIMER databases to understand the significance of essential genes in tumorigenesis. In addition, we performed transcription factor identification. We discovered three biomarkers (IFI30, BLVRA, and RIN2) that are mostly involved in interferon-related signaling pathways and are associated with monocyte-mediated immune responses in SLE. The three important genes are also strongly expressed in a number of malignancies and have a relationship with monocytes. As a result, IFI30, BLVRA, and RIN2 may act as SLE-associated biomarkers of monocytes and as a bridge between SLE and tumors. We proposed that interferon-related signaling pathways might function as possible mediators of cancer risk in SLE.

Innate immune memory in inflammatory arthritis

The concept of immunological memory was demonstrated in antiquity when protection against re-exposure to pathogens was observed during the plague of Athens. Immunological memory has been linked with the adaptive features of T and B cells; however, in the past decade, evidence has demonstrated that innate immune cells can exhibit memory, a phenomenon called 'innate immune memory' or 'trained immunity'. Innate immune memory is currently being defined and is transforming our understanding of chronic inflammation and autoimmunity. In this Review, we provide an up-to-date overview of the memory-like features of innate immune cells in inflammatory arthritis and the crosstalk between chronic inflammatory milieu and cell reprogramming. Aberrant pro-inflammatory signalling, including cytokines, regulates the metabolic and epigenetic reprogramming of haematopoietic progenitors, leading to exacerbated inflammatory responses and osteoclast differentiation, in turn leading to bone destruction. Moreover, imprinted memory on mature cells including terminally differentiated osteoclasts alters responsiveness to therapies and modifies disease outcomes, commonly manifested by persistent inflammatory flares and relapse following medication withdrawal.

Transcriptomic and proteomic profiling reveals distinct pathogenic features of peripheral non-classical monocytes in systemic lupus erythematosus

Peripheral blood monocytes propagate inflammation in systemic lupus erythematosus (SLE). Three major populations of monocytes have been recognized namely classical (CM), intermediate (IM) and non-classical monocytes (NCM). Herein, we performed a comprehensive transcriptomic, proteomic and functional characterization of the three peripheral monocytic subsets from active SLE patients and healthy individuals. Our data demonstrate extensive molecular disruptions in circulating SLE NCM, characterized by enhanced inflammatory features such as deregulated DNA repair, cell cycle and heightened IFN signaling combined with differentiation and developmental cues. Enhanced DNA damage, elevated expression of p53, G0 arrest of cell cycle and increased autophagy stress the differentiation potential of NCM in SLE. This immunogenic profile is associated with an activated macrophage phenotype of NCM exhibiting M1 characteristics in the circulation, fueling the inflammatory response. Together, these findings identify circulating SLE NCM as a pathogenic cell type in the disease that could represent an additional therapeutic target.

A LY6E-PHB1-TRIM21 assembly degrades CD14 protein to mitigate LPS-induced inflammatory response

A major theme of host against invading pathogens lies in multiple regulatory nodes that ensure sufficient signals for protection while avoiding excessive signals toward over-inflammation. The TLR4/MD-2/CD14 complex receptor-mediated response to bacterial lipopolysaccharide (LPS) represents a paradigm for understanding the proper control of anti-pathogen innate immunity. In this study, we studied the mechanism by which the glycosylphosphatidylinositol (GPI)-linked LY6E protein constrains LPS response via downregulating CD14. We first showed that LY6E downregulated CD14 via ubiquitin-dependent proteasomal degradation. The subsequent profiling of LY6E protein interactome led to the revelation that the degradation of CD14 by LY6E requires PHB1, which interacts with CD14 in a LY6E-dependent manner. Finally, we identified the PHB1-interacting TRIM21 as the major ubiquitin E3 ligase for the LY6E-mediated ubiquitination of CD14. Together, our study elucidated the molecular basis of LY6E-mediated governance of LPS response, alongside providing new insights to regulatory mechanisms controlling the homeostasis of membrane proteins.

Training vs. Tolerance: The Yin/Yang of the Innate Immune System

For almost nearly a century, memory functions have been attributed only to acquired immune cells. Lately, this paradigm has been challenged by an increasing number of studies revealing that innate immune cells are capable of exhibiting memory-like features resulting in increased responsiveness to subsequent challenges, a process known as trained immunity (known also as innate memory). In contrast, the refractory state of endotoxin tolerance has been defined as an immunosuppressive state of myeloid cells portrayed by a significant reduction in the inflammatory capacity. Both training as well tolerance as adaptive features are reported to be accompanied by epigenetic and metabolic alterations occurring in cells. While training conveys proper protection against secondary infections, the induction of endotoxin tolerance promotes repairing mechanisms in the cells. Consequently, the inappropriate induction of these adaptive cues may trigger maladaptive effects, promoting an increased susceptibility to secondary infections-tolerance, or contribute to the progression of the inflammatory disorder-trained immunity. This review aims at the discussion of these opposing manners of innate immune and non-immune cells, describing the molecular, metabolic and epigenetic mechanisms involved and interpreting the clinical implications in various inflammatory pathologies.

Supporting the differential diagnosis of connective tissue diseases with neurological involvement by blood and cerebrospinal fluid flow cytometry

OBJECTIVE

Neurological manifestations of autoimmune connective tissue diseases (CTD) are poorly understood and difficult to diagnose. We here aimed to address this shortcoming by studying immune cell compositions in CTD patients with and without neurological manifestation.

METHODS

Using flow cytometry, we retrospectively investigated paired cerebrospinal fluid (CSF) and blood samples of 28 CTD patients without neurological manifestation, 38 CTD patients with neurological manifestation (N-CTD), 38 non-inflammatory controls, and 38 multiple sclerosis (MS) patients, a paradigmatic primary neuroinflammatory disease.

RESULTS

We detected an expansion of plasma cells in the blood of both N-CTD and CTD compared to non-inflammatory controls and MS. Blood plasma cells alone distinguished the clinically similar entities N-CTD and MS with high discriminatory performance (AUC: 0.81). Classical blood monocytes indicated higher disease activity in systemic lupus erythematosus (SLE) patients. Surprisingly, immune cells in the CSF did not differ significantly between N-CTD and CTD, while CD4⁺ T cells and the CD4⁺/CD8⁺ ratio were elevated in the blood of N-CTD compared to CTD. Several B cell-associated parameters partially overlapped in the CSF in MS and N-CTD. We built a machine learning model that distinguished N-CTD from MS with high discriminatory power using either blood or CSF.

CONCLUSION

We here find that blood flow cytometry alone surprisingly suffices to distinguish CTD with neurological manifestations from clinically similar entities, suggesting that a rapid blood test could support clinicians in the differential diagnosis of N-CTD.

Peripheral monocytes and soluble biomarkers in autoimmune encephalitis

BACKGROUND AND OBJECTIVES

Autoimmune encephalitis (AE) is an inflammatory disease of the central nervous system which can result in long-term seizures and cognitive dysfunction despite treatment with immunotherapy. The role of the innate immune system in AE is not well established. To investigate the contribution of innate immunity to AE and its long-term outcomes we evaluated peripheral monocytes and serum cytokines in the periphery of patients with AE.

METHODS AND RESULTS

We recruited 40 patients with previously diagnosed AE and 28 healthy volunteers to our cross-sectional observation study and evaluated their peripheral blood monocytes via flow cytometry and serum cytokines (CCL-2, CCL-17, G-CSF, GM-CSF, IFNγ, IL-1α, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-10, IL-17, TNFα) via ELISA.Compared with controls the AE cohort had expansion of the 'pro-inflammatory' CD14⁺CD16⁺ monocyte sub-population (7.13% vs 5.46%, p < 0.01) with higher levels of serum IL-6 (2.34 pg/mL vs 0.54 pg/mL, p < 0.001). These changes were most significant in anti-LGI-1 antibody mediated AE, an AE subtype with poor long-term cognitive outcomes.

CONCLUSION

Expansion of the peripheral CD14⁺CD16⁺ monocyte population and increased serum IL-6 in AE is reflective of changes seen in other systemic inflammatory and neurodegenerative conditions. These changes may indicate a persistent pro-inflammatory state in AE and may contribute to poor long-term outcomes.

Understanding the development of Th2 cell-driven allergic airway disease in early life

Allergic diseases, including atopic dermatitis, allergic rhinitis, asthma, and food allergy, are caused by abnormal responses to relatively harmless foreign proteins called allergens found in pollen, fungal spores, house dust mites (HDM), animal dander, or certain foods. In particular, the activation of allergen-specific helper T cells towards a type 2 (Th2) phenotype during the first encounters with the allergen, also known as the sensitization phase, is the leading cause of the subsequent development of allergic disease. Infants and children are especially prone to developing Th2 cell responses after initial contact with allergens. But in addition, the rates of allergic sensitization and the development of allergic diseases among children are increasing in the industrialized world and have been associated with living in urban settings. Particularly for respiratory allergies, greater susceptibility to developing allergic Th2 cell responses has been shown in children living in urban environments containing low levels of microbial contaminants, principally bacterial endotoxins [lipopolysaccharide (LPS)], in the causative aeroallergens. This review highlights the current understanding of the factors that balance Th2 cell immunity to environmental allergens, with a particular focus on the determinants that program conventional dendritic cells (cDCs) toward or away from a Th2 stimulatory function. In this context, it discusses transcription factor-guided functional specialization of type-2 cDCs (cDC2s) and how the integration of signals derived from the environment drives this process. In addition, it analyzes observational and mechanistic studies supporting an essential role for innate sensing of microbial-derived products contained in aeroallergens in modulating allergic Th2 cell immune responses. Finally, this review examines whether hyporesponsiveness to microbial stimulation, particularly to LPS, is a risk factor for the induction of Th2 cell responses and allergic sensitization during infancy and early childhood and the potential factors that may affect early-age response to LPS and other environmental microbial components.

A third dose of the unmodified COVID-19 mRNA vaccine CVnCoV enhances quality and quantity of immune responses

A third vaccine dose is often required to achieve potent, long-lasting immune responses. We investigated the impact of three 8 μg doses of CVnCoV, CureVac's SARS-CoV-2 vaccine candidate containing sequence-optimized unmodified mRNA encoding spike (S) glycoprotein, administered at 0, 4 and 28 weeks on immune responses in rhesus macaques. Following the third dose S-specific binding and neutralizing antibodies increased 50-fold compared with post-dose 2 levels, with increased responses also evident in the lower airways and against the SARS-CoV-2 B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma) and B.1.617.2 (Delta) variants. Enhanced binding affinity of serum antibodies after the third dose correlated with higher somatic hypermutation in S-specific B cells, corresponding with improved binding properties of monoclonal antibodies expressed from isolated B cells. Administration of low dose mRNA led to fewer cells expressing antigen in vivo at the injection site and in the draining lymph nodes compared with a tenfold higher dose, possibly reducing the engagement of precursor cells with the antigen and resulting in the suboptimal response observed following two-dose vaccination schedules in phase IIb/III clinical trials of CVnCoV. However, when immune memory is established, a third dose efficiently boosts the immunological responses as well as improves antibody affinity and breadth.

Altered Balance of Pro-Inflammatory Immune Cells to T Regulatory Cells Differentiates Symptomatic From Asymptomatic Individuals With Anti-Nuclear Antibodies

Systemic Autoimmune Rheumatic Diseases (SARDs) are characterized by the production of anti-nuclear antibodies (ANAs). ANAs are also seen in healthy individuals and can be detected years before disease onset in SARD. Both the immunological changes that promote development of clinical symptoms in SARD and those that prevent autoimmunity in asymptomatic ANA+ individuals (ANA+ NS) remain largely unexplored. To address this question, we used flow cytometry to examine peripheral blood immune populations in ANA+ individuals, with and without SARD, including 20 individuals who subsequently demonstrated symptom progression. Several immune populations were expanded in ANA+ individuals with and without SARD, as compared with ANA- healthy controls, particularly follicular and peripheral T helper, and antibody-producing B cell subsets. In ANA+ NS individuals, there were significant increases in T regulatory subsets and TGF-ß1 that normalized in SARD patients, whereas in SARD patients there were increases in Th2 and Th17 helper cell levels as compared with ANA+ NS individuals, resulting in a shift in the balance between inflammatory and regulatory T cell subsets. Patients with SARD also had increases in the proportion of pro-inflammatory innate immune cell populations, such as CD14+ myeloid dendritic cells, and intermediate and non-classical monocytes, as compared to ANA+ NS individuals. When comparing ANA+ individuals without SARD who progressed clinically over the subsequent 2 years with those who did not, we found that progressors had significantly increased T and B cell activation, as well as increased levels of LAG3+ T regulatory cells and TGF-ß1. Collectively, our findings suggest that active immunoregulation prevents clinical autoimmunity in ANA+ NS and that this becomes impaired in patients who progress to SARD, resulting in an imbalance favoring inflammation.

Immunological Subsets Characterization in Newly Diagnosed Relapsing-Remitting Multiple Sclerosis

Objectives

Using flow cytometry, we characterized myeloid, B, and T cells in patients recently diagnosed with relapsing–remitting multiple sclerosis (RRMS) naive to disease-modifying therapies (DMTs).

Methods

This prospective case–control study was conducted in the tertiary MS center of Catania, Italy. Demographic/clinical data and peripheral bloods were collected from 52 naive patients recently diagnosed with RRMS and sex/age-matched healthy controls (HCs) in a 2:1 ratio. We performed flow cytometry on isolated peripheral blood mononuclear cells to assess immune cell subsets differences between RMMS patients and HCs. We explored the biomarker potential of cell subsets using receiver operating characteristic (ROC) curves and relative area under the curve (AUC) analyses.

Results

Monocytic myeloid-derived suppressor cells (Mo-MDSCs CD14+/HLADR^−/low) and inflammatory monocytes (CD14+CD16+) displayed higher frequencies in RRMS patients when compared with HCs (p <.05). A lower percentage of B-unswitched memory cells was observed in RRMS patients when compared with HCs (p = .026). T cells had a higher frequency of T-helper CD4+ cells and their subset, CD4+CD161+, in RRMS patients when compared with HCs (p <.001). ROC analyses revealed an AUC >70% for Mo-MDSCs CD14+/HLADR^−/low and inflammatory CD14+CD16+, T-helper CD3+CD4+, and T-helper CD4+CD161+.

Conclusions

Patients with a recent RRMS diagnosis and naive to DMTs, showed peculiar myeloid, B-, and T-cell immunophenotypes.

RNASE2 Mediates Age-Associated B Cell Expansion Through Monocyte Derived IL-10 in Patients With Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is characterized by the production of pathogenic autoantibodies. Ribonuclease A family member 2 (RNase2) is known to have antiviral activity and immunomodulatory function. Although RNASE2 level has been reported to be elevated in SLE patients based on mRNA microarray detection, its pathologic mechanism remains unclear. Here, we confirmed that RNASE2 was highly expressed in PBMCs from SLE patients and associated with the proportion of CD11c⁺T-bet⁺ B cells, a class of autoreactive B cells also known as age-associated B cells (ABCs). We showed that reduction of RNASE2 expression by small interfering RNA led to the decrease of ABCs in vitro, accompanied by total IgG and IL-10 reduction. In addition, we demonstrated that both RNASE2 and IL-10 in peripheral blood of lupus patients were mainly derived from monocytes. RNASE2 silencing in monocytes down-regulated IL-10 production and consequently reduced ABCs numbers in monocyte-B cell co-cultures, which could be restored by the addition of recombinant IL-10. Based on above findings, we concluded that RNASE2 might induce the production of ABCs via IL-10 secreted from monocytes, thus contributing to the pathogenesis of SLE.

Circulating inflammatory cell profiling and periodontitis: A systematic review and meta-analysis

Inflammation is a key driver of common noncommunicable diseases. Among common triggers of inflammation, chronic gingival inflammation (periodontitis) triggers a consistent humoral host inflammatory response, but little is known on its impact on circulating inflammatory cell profiles. We aimed to systematically appraise all the evidence linking periodontitis and its treatment to circulating inflammatory cell profiles. From 6 databases, 157 studies were eligible for qualitative synthesis and 29 studies for meta-analysis. Our meta-analysis showed that participants with periodontitis exhibited a significant mean increase in circulating CD4⁺ , CD4⁺ CD45RO⁺ , IFNγ-expressing CD4⁺ and CD8⁺ T cells, CD19⁺ CD27⁺ and CD5⁺ B cells, CD14⁺ CD16⁺ monocytes, and CD16⁺ neutrophils but decrease in CD8⁺ T and CD14⁺⁺ CD16^- monocytes. Our qualitative synthesis revealed that peripheral blood neutrophils of patients with periodontitis consistently showed elevated production of reactive oxygen species (ROS) when compared with those of healthy controls. Some evidence suggested that the treatment of periodontitis reversed the exaggerated ROS production, but limited and inconclusive data were found on several circulating inflammatory cell profiling. We conclude that periodontitis and its treatment are associated with minor but consistent alterations in circulating inflammatory cell profiles. These changes could represent key mechanisms explaining the association of periodontitis with other comorbidities such as cardiovascular disease, diabetes, and rheumatoid arthritis.

Macrophages Can Drive Sympathetic Excitability in the Early Stages of Hypertension

Hypertension is a major health burden worldwide with many cases resistant to current treatments. Hyperactivity of the sympathetic nervous contributes to the etiology and progression of the disease, where emerging evidence suggests that inflammation may underpin the development of sympathetic dysautonomia. This study examined whether macrophages could drive the sympathetic phenotype in Spontaneously Hypertensive Rats (SHR) before animals develop high pressure. Stellate neurons from wild-type control Wistar rats and SHRs were co-cultured with blood leukocytes from their own strain, and also crossed cultured between strains. The calcium transient response to nicotinic stimulation was recorded using Fura-2 calcium imaging, where SHR neurons had a greater calcium transient compared with Wistar neurons. However, when co-cultured with leukocytes, Wistar neurons began to phenocopy the SHR sympathetic hyperactivity, while the SHR neurons themselves were unaltered. Resident leukocyte populations of the SHR and Wistar stellate ganglia were then compared using flow cytometry, where there was a shift in monocyte-macrophage subset proportions. While classical monocyte-macrophages were predominant in the Wistar, there were relatively more of the non-classical subset in the SHR, which have been implicated in pro-inflammatory roles in a number of diseases. When bone marrow-derived macrophages (BMDMs) were co-cultured with stellate neurons, they made Wistar neurons recapitulate the SHR nicotinic stimulated calcium transient. Wistar BMDMs however, had no effect on SHR neurons, even though SHR BMDMs increased SHR neuron responsiveness further above their hyper-responsive state. Taken together, these findings show that macrophages can be potent enhancers of sympathetic neuronal calcium responsiveness, and thus could conceivably play a role in peripheral sympathetic hyperactivity observed in the early stages of hypertension.

Microbial (co)infections: Powerful immune influencers

It is well established that by modulating various immune functions, host infection may alter the course of concomitant inflammatory diseases, of both infectious and autoimmune etiologies. Beyond the major impact of commensal microbiota on the immune status, host exposure to viral, bacterial, and/or parasitic microorganisms also dramatically influences inflammatory diseases in the host, in a beneficial or harmful manner. Moreover, by modifying pathogen control and host tolerance to tissue damage, a coinfection can profoundly affect the development of a concomitant infectious disease. Here, we review the diverse mechanisms that underlie the impact of (co)infections on inflammatory disorders. We discuss epidemiological studies in the context of the hygiene hypothesis and shed light on the sometimes dual impact of germ exposure on human susceptibility to inflammatory disease. We then summarize the immunomodulatory mechanisms at play, which can involve pleiotropic effects of immune players and discuss the possibility to harness pathogen-derived compounds to the host benefit.

Data-Driven Analysis of COVID-19 Reveals Persistent Immune Abnormalities in Convalescent Severe Individuals

Severe SARS-CoV-2 infection can trigger uncontrolled innate and adaptive immune responses, which are commonly associated with lymphopenia and increased neutrophil counts. However, whether the immune abnormalities observed in mild to severely infected patients persist into convalescence remains unclear. Herein, comparisons were drawn between the immune responses of COVID-19 infected and convalescent adults. Strikingly, survivors of severe COVID-19 had decreased proportions of NKT and Vδ2 T cells, and increased proportions of low-density neutrophils, IgA+/CD86+/CD123+ non-classical monocytes and hyperactivated HLADR+CD38+ CD8+ T cells, and elevated levels of pro-inflammatory cytokines such as hepatocyte growth factor and vascular endothelial growth factor A, long after virus clearance. Our study suggests potential immune correlates of "long COVID-19", and defines key cells and cytokines that delineate true and quasi-convalescent states.

The Th17/IL-17 Axis and Kidney Diseases, With Focus on Lupus Nephritis

Systemic lupus erythematosus (SLE) is a disease characterized by dysregulation and hyperreactivity of the immune response at various levels, including hyperactivation of effector cell subtypes, autoantibodies production, immune complex formation, and deposition in tissues. The consequences of hyperreactivity to the self are systemic and local inflammation and tissue damage in multiple organs. Lupus nephritis (LN) is one of the most worrying manifestations of SLE, and most patients have this involvement at some point in the course of the disease. Among the effector cells involved, the Th17, a subtype of T helper cells (CD4+), has shown significant hyperactivation and participates in kidney damage and many other organs. Th17 cells have IL-17A and IL-17F as main cytokines with receptors expressed in most renal cells, being involved in the activation of many proinflammatory and profibrotic pathways. The Th17/IL-17 axis promotes and maintains repetitive tissue damage and maladaptive repair; leading to fibrosis, loss of organ architecture and function. In the podocytes, the Th17/IL-17 axis effects include changes of the cytoskeleton with increased motility, decreased expression of health proteins, increased oxidative stress, and activation of the inflammasome and caspases resulting in podocytes apoptosis. In renal tubular epithelial cells, the Th17/IL-17 axis promotes the activation of profibrotic pathways such as increased TGF-β expression and epithelial-mesenchymal transition (EMT) with consequent increase of extracellular matrix proteins. In addition, the IL-17 promotes a proinflammatory environment by stimulating the synthesis of inflammatory cytokines by intrinsic renal cells and immune cells, and the synthesis of growth factors and chemokines, which together result in granulopoiesis/myelopoiesis, and further recruitment of immune cells to the kidney. The purpose of this work is to present the prognostic and immunopathologic role of the Th17/IL-17 axis in Kidney diseases, with a special focus on LN, including its exploration as a potential immunotherapeutic target in this complication.

The Transcriptomic Profile of Monocytes from Patients With Sjögren's Syndrome Is Associated With Inflammatory Parameters and Is Mimicked by Circulating Mediators

Primary Sjögren's syndrome (pSS) is a systemic autoimmune disease characterized by infiltration of the exocrine glands and prominent B cell hyperactivity. Considering the key role of monocytes in promoting B cell hyperactivity, we performed RNA-sequencing analysis of CD14⁺ monocytes from patients with pSS, non-Sjögren's sicca (nSS), and healthy controls (HC). We demonstrated that the transcriptomic profile of pSS patients is enriched in intermediate and non-classical monocyte profiles, and confirmed the increased frequency of non-classical monocytes in pSS patients by flow-cytometry analysis. Weighted gene co-expression network analysis identified four molecular signatures in monocytes from pSS patients, functionally annotated for processes related with translation, IFN-signaling, and toll-like receptor signaling. Systemic and local inflammatory features significantly correlated with the expression of these signatures. Furthermore, genes highly associated with clinical features in pSS were identified as hub-genes for each signature. Unsupervised hierarchical cluster analysis of the hub-genes identified four clusters of nSS and pSS patients, each with distinct inflammatory and transcriptomic profiles. One cluster showed a significantly higher percentage of pSS patients with higher prevalence of anti-SSA autoantibodies, interferon-score, and erythrocyte sedimentation rate compared to the other clusters. Finally, we showed that the identified transcriptomic differences in pSS monocytes were induced in monocytes of healthy controls by exposure to serum of pSS patients. Representative hub-genes of all four signatures were partially inhibited by interferon-α/β receptor blockade, indicating that the circulating inflammatory mediators, including type I interferons have a significant contribution to the altered transcriptional profile of pSS-monocytes. Our study suggests that targeting key circulating inflammatory mediators, such as type I interferons, could offer new insights into the important pathways and mechanisms driving pSS, and holds promise for halting immunopathology in Sjögren's Syndrome.

Anaphylatoxins orchestrate Th17 response via interactions between CD16+ monocytes and pleural mesothelial cells in tuberculous pleural effusion

The complement system is activated in tuberculous pleural effusion (TPE), with increased levels of the anaphylatoxins stimulating pleural mesothelial cells (PMCs) to secrete chemokines, which recruit nonclassical monocytes to the pleural cavity. The differentiation and recruitment of naive CD4⁺ T cells are induced by pleural cytokines and PMC-produced chemokines in TPE. However, it is unclear whether anaphylatoxins orchestrate CD4⁺ T cell response via interactions between PMCs and monocytes in TPE. In this study, CD16⁺ and CD16^- monocytes isolated from TPE patients were cocultured with PMCs pretreated with anaphylatoxins. After removing the PMCs, the conditioned monocytes were cocultured with CD4⁺ T cells. The levels of the cytokines were measured in PMCs and monocyte subsets treated separately with anaphylatoxins. The costimulatory molecules were assessed in conditioned monocyte subsets. Furthermore, CD4⁺ T cell response was evaluated in different coculture systems. The results indicated that anaphylatoxins induced PMCs and CD16⁺ monocytes to secrete abundant cytokines capable of only inducing Th17 expansion, but Th1 was feeble. In addition, costimulatory molecules were more highly expressed in CD16⁺ than in CD16⁻ monocytes isolated from TPE. The interactions between monocytes and PMCs enhanced the ability of PMCs and monocytes to produce cytokines and that of monocytes to express HLA-DR, CD40, CD80 and CD86, which synergistically induced Th17 expansion. In the above process, anaphylatoxins enhanced the interactions between monocytes and PMCs by increasing the level of the cytokines IL-1β, IL-6, IL-23 and upregulating the phenotype of CD40 and CD80 in CD16⁺ monocytes. Collectively, these data indicate that anaphylatoxins play a central role in orchestrating Th17 response mainly via interactions between CD16⁺ monocytes and PMCs in TPE.

Tuberculous pleural effusion is characterized by intense chronic accumulations of fluid and lymphocyte cells and monocytes/macrophages in the pleural space. Complement mediators play important roles in providing protection against Mycobacterium tuberculosis. Our results demonstrated that Mycobacterium tuberculosis infection induced the amplification of complement activation in TPE. Complement activation produces anaphylatoxins that induce PMCs and CD16⁺ monocytes to secrete abundant cytokines capable of only inducing Th17 expansion, but Th1 was feeble. In addition, costimulatory molecules were more highly expressed in CD16⁺ than in CD16⁻ monocytes isolated from TPE. The interactions between monocytes and PMCs enhanced the ability of PMCs and monocytes to produce cytokines and that of monocytes to express HLA-DR, CD40, CD80 and CD86, which synergistically induced Th17 expansion. In the above process, anaphylatoxins enhanced the interactions between monocytes and PMCs by increasing the level of the cytokines IL-1β, IL-6, IL-23 and upregulating the phenotype of CD40 and CD80 in CD16+ monocytes. In summary, these data highlighted the importance of anaphylatoxins and the innate immune system in eliciting pathogenic T cell responses in TPE and suggested that monocytes, especially the CD16⁺ subset, might be an efficient target for controlling inflammation.

HMGB1 Activates Myeloid Dendritic Cells by Up-Regulating mTOR Pathway in Systemic Lupus Erythematosus

Research has shown that HMGB1 can activate dendritic cells (DCs), but its molecular mechanisms are not clear. In this study, we reported that the myeloid dendritic cells (mDCs) were activated in the peripheral blood of SLE patients, and the activation of mDCs was associated with the up-regulation of HMGB1 and mTOR. After stimulated by HMGB1, expression of mTOR and its substrates P70S6K and 4EBP1 in dendritic cells increased considerably (P < 0.01). The expression of HLA-DR, CD40, and CD86 on dendritic cells also significantly increased following these stimuli (P < 0.01). In addition, stimulation with HMGB1 enhanced cytokine (IL-1β, IL-6, and TNF-a) production in dendritic cells. In contrast, the HMGB1-mediated expression of HLA-DR, CD40, and CD86 on dendritic cells and production of IL-1β, IL-6, and TNF-α were reduced by rapamycin. Rapamycin can inhibit HMGB1-induced activation of mDCs and secretion of pro-inflammatory cytokines. These findings indicated that HMGB1activates mDCs by up-regulating the mTOR pathway in SLE.

Homozygous variant p. Arg90His in NCF1 is associated with early-onset Interferonopathy: a case report

BACKGROUND

Biallelic loss-of-function variants in NCF1 lead to reactive oxygen species deficiency and chronic granulomatous disease (CGD). Heterozygosity for the p.Arg90His variant in NCF1 has been associated with susceptibility to systemic lupus erythematosus, rheumatoid arthritis, and Sjögren's syndrome in adult patients. This study demonstrates the association of the homozygous p.Arg90His variant with interferonopathy with features of autoinflammation and autoimmunity in a pediatric patient.

CASE PRESENTATION

A 5-year old female of Indian ancestry with early-onset recurrent fever and headache, and persistently elevated antinuclear, anti-Ro, and anti-La antibodies was found to carry the homozygous p.Arg90His variant in NCF1 through exome sequencing. Her unaffected parents and three other siblings were carriers for the mutant allele. Because the presence of two NCF1 pseudogenes, this variant was confirmed by independent genotyping methods. Her intracellular neutrophil oxidative burst and NCF1 expression levels were normal, and no clinical features of CGD were apparent. Gene expression analysis in peripheral blood detected an interferon gene expression signature, which was further supported by cytokine analyses of supernatants of cultured patient's cells. These findings suggested that her inflammatory disease is at least in part mediated by type I interferons. While her fever episodes responded well to systemic steroids, treatment with the JAK inhibitor tofacitinib resulted in decreased serum ferritin levels and reduced frequency of fevers.

CONCLUSION

Homozygosity for p.Arg90His in NCF1 should be considered contributory in young patients with an atypical systemic inflammatory antecedent phenotype that may evolve into autoimmunity later in life. The complex genomic organization of NCF1 poses a difficulty for high-throughput genotyping techniques and variants in this gene should be carefully evaluated when using the next generation and Sanger sequencing technologies. The p.Arg90His variant is found at a variable allele frequency in different populations, and is higher in people of South East Asian ancestry. In complex genetic diseases such as SLE, other rare and common susceptibility alleles might be necessary for the full disease expressivity.

IFNs Reset the Differential Capacity of Human Monocyte Subsets to Produce IL-12 in Response to Microbial Stimulation

Human primary monocytes are composed of a minor, more mature CD16+(CD14low/neg) population and a major CD16neg(CD14+) subset. The specific functions of CD16+ versus CD16neg monocytes in steady state or inflammation remain poorly understood. In previous work, we found that IL-12 is selectively produced by the CD16+ subset in response to the protozoan pathogen, Toxoplasma gondii In this study, we demonstrated that this differential responsiveness correlates with the presence of an IFN-induced transcriptional signature in CD16+ monocytes already at baseline. Consistent with this observation, we found that in vitro IFN-γ priming overcomes the defect in the IL-12 response of the CD16neg subset. In contrast, pretreatment with IFN-γ had only a minor effect on IL-12p40 secretion by the CD16+ population. Moreover, inhibition of the mTOR pathway also selectively increased the IL-12 response in CD16neg but not in CD16+ monocytes. We further demonstrate that in contrast to IFN-γ, IFN-α fails to promote IL-12 production by the CD16neg subset and blocks the effect of IFN-γ priming. Based on these observations, we propose that the acquisition of IL-12 responsiveness by peripheral blood monocyte subsets depends on extrinsic signals experienced during their developmental progression in vivo. This process can be overridden during inflammation by the opposing regulatory effects of type I and II IFN as well as the mTOR inhibition.

B cell and monocyte phenotyping: A quick asset to investigate the immune status in patients with IgA nephropathy

Background

IgA nephropathy (IgAN) advances from multiple pathogenic “hits” resulting in poorly O-galactosylated IgA1 glycoforms (Gd-IgA1), production of antibodies and glomerular deposition of immune complexes. A sequence of immune responses arising from plasma cells, T cells and antigen presenting cells (APCs), causes glomerular injury. This study was designed to phenotype subsets of B cells, monocytes and T cells in the peripheral circulation and their association with inflammatory cytokines and kidney function in patients with IgAN, healthy controls (HC) and disease controls with autosomal dominant polycystic kidney disease (ADPKD).

Methods

Patients with IgAN (n = 13), median estimated glomerular filtration rate (eGFR) of 57 ml/min/1.73m² (IQR 42–84), patients with ADPKD (n = 13) matched for kidney function, gender and age and gender and age-matched HC (n = 13) were recruited. CD3+ and CD3- peripheral blood mononuclear cells were isolated and profiled based on their specific surface markers for different subsets of monocytes, B and T cells and analyzed by flow cytometry. Cytokines were analyzed by ELISA.

Results

We observed a significant decrease in the proportion of pre-switched B cells and plasmablasts, but an increase in long-lived plasma cells in the peripheral circulation of IgAN patients compared to HC. The proportion of non-classical monocytes was significantly higher in IgAN patients compared to both HC and ADPKD. We also report an association between sCD40L levels and the proportion of pre-switched B cells, as well as sCD40L and MCP-1 levels and albuminuria in IgAN patients.

Conclusions

We applied an easy-access method to analyze subsets of immune cells as well as relevant inflammatory mediators in IgAN patients. Our data demonstrate an altered B cell profile that indicates a pathophysiological role of the B cell lineage and an increased proportion of non-classical monocytes that suggests their role in the disease process.

Aberrant monocyte subsets in patients with Behçet's disease

Monocytes are a versatile and dynamic population, but its implication in Behçet's Disease (BD) remains elusive. We investigated the proportion, phenotypical and functional alterations in classical monocytes (CM), intermediate monocytes (IM) and non-classical monocytes (NCM) subsets in BD. A higher IM and lower NCM population in BD patients were noted, closely correlated with disease activity, and rescued after treatment. CD11b and CD64 expression on CM, IM and NCM in BD were enhanced. BD CM promoted TNF-a and IL-6 production and facilitated Th1 differentiation. BD IM promoted IL-6 production. We further demonstrated a higher level of phosphorylated p65 (p-p65) in BD CM and increased p-p65 and p-p38 in BD IM. Our data highlighted the aberrant populations of IM and CM in BD, potentially implicated in BD' pathogenesis.

Low-density granulocytes and monocytes as biomarkers of cardiovascular risk in systemic lupus erythematosus

OBJECTIVE

The aim was to evaluate the most relevant cell populations involved in vascular homeostasis as potential biomarkers of SLE-related cardiovascular disease (CVD).

METHODS

Low-density granulocytes (LDGs), monocyte subsets, endothelial progenitor cells, angiogenic T (Tang) cells, CD4+CD28null and Th1/Th17 lymphocytes and serum cytokine levels were quantified in 109 SLE patients and 33 controls in relationship to the presence of subclinical carotid atheromatosis or cardiovascular disease. A second cohort including 31 recent-onset SLE patients was also included.

RESULTS

Raised monocyte and LDG counts, particularly those LDGs negative for CD16/CD14 expression (nLDGs), in addition to the ratios of monocytes and nLDGs to high-density lipoprotein-cholesterol (HDLc) molecules (MHR and nLHR, respectively), were present in SLE patients with traditional risk factors or subclinical atheromatosis but not in those who were CV-free, thus revealing their value in the identification of patients at risk of CVD, even at the onset of disease. Accordingly, nLDGs were correlated positively with carotid intima-media thickness (cIMT) and with inflammatory markers (CRP and IL-6). A bias towards more differentiated monocyte subsets, related to increased IFN-α and IL-17 serum levels, was also observed in patients. Intermediate monocytes were especially expanded, but independently of their involvement in CVD. Finally, CD4+CD28null, Th17 and Th1 lymphocytes were increased, with CD4+CD28null and Th17 cells being associated with cIMT, whereas endothelial progenitor and Tang cell levels were reduced in all SLE patients.

CONCLUSION

The present study highlights the potential use of MHR and nLHR as valuable biomarkers of CVD risk in SLE patients, even at diagnosis. The increased amounts of nLDGs, monocytes, Th17 and senescent-CD28null subsets, coupled with reduced pro-angiogenic endothelial progenitor cells and Tang cells, could underlie the development of atheromatosis in SLE.

CD14+CD16- monocytes are the main precursors of osteoclasts in rheumatoid arthritis via expressing Tyro3TK

Background

Monocytes as precursors of osteoclasts in rheumatoid arthritis (RA) are well demonstrated, while monocyte subsets in osteoclast formation are still controversial. Tyro3 tyrosine kinase (Tyro3TK) is a member of the receptor tyrosine kinase family involved in immune homeostasis, the role of which in osteoclast differentiation was reported recently. This study aimed to compare the osteoclastic capacity of CD14⁺CD16⁺ and CD14⁺CD16⁻ monocytes in RA and determine the potential involvement of Tyro3TK in their osteoclastogenesis.

Methods

Osteoclasts were induced from CD14⁺CD16⁺ and CD14⁺CD16⁻ monocyte subsets isolated from healthy control (HC) and RA patients in vitro and evaluated by tartrate-resistant acid phosphatase (TRAP) staining. Then, the expression of Tyro3TK on CD14⁺CD16⁺ and CD14⁺CD16⁻ monocyte subsets in the peripheral blood of RA, osteoarthritis (OA) patients, and HC were evaluated by flow cytometry and qPCR, and their correlation with RA patient clinical and immunological features was analyzed. The role of Tyro3TK in CD14⁺CD16⁻ monocyte-mediated osteoclastogenesis was further investigated by osteoclast differentiation assay with Tyro3TK blockade.

Results

The results revealed that CD14⁺CD16⁻ monocytes were the primary source of osteoclasts. Compared with HC and OA patients, the expression of Tyro3TK on CD14⁺CD16⁻ monocytes in RA patients was significantly upregulated and positively correlated with the disease manifestations, such as IgM level, tender joint count, and the disease activity score. Moreover, anti-Tyro3TK antibody could inhibit Gas6-mediated osteoclast differentiation from CD14⁺CD16⁻ monocytes in a dose-dependent manner.

Conclusions

These findings indicate that elevated Tyro3TK on CD14⁺CD16⁻ monocytes serves as a critical signal for osteoclast differentiation in RA.

The epigenetic face of lupus: Focus on antigen-presenting cells

In recent years, epigenetic mechanisms became widely known due to their ability to regulate and maintain physiological processes such as cell growth, development, differentiation and genomic stability. When dysregulated, epigenetic mechanisms, may introduce gene expression changes and disturbance in immune homeostasis leading to autoimmune diseases. Systemic lupus erythematosus (SLE), the most extensively studied autoimmune disorder, has already been correlated with epigenetic modifications, especially in T cells. Since these cell rely on antigen presentation, it may be assumed that erroneous activity of antigen-presenting cells (APCs), culminates in T cell abnormalities. In this review we summarize and discuss the epigenetic modifications in SLE affected APCs, with the focus on dendritic cells (DCs), B cells and monocytes. Unravelling this aspect of SLE pathogenesis, might result in identification of new disease biomarkers and putative therapeutic approaches.

Antibodies against carbamylated vimentin exist in systemic lupus erythematosus and correlate with disease activity

OBJECTIVES

Antibodies against carbamylated protein (anti-CarP) were found to be a promising marker to evaluate joint damage and disease activity in patients with rheumatoid arthritis (RA). However, whether anti-CarP antibodies were present in systemic lupus erythematosus (SLE) remained ambiguous. We have therefore undertaken this study to assess the levels of serum anti-CarP antibodies and to evaluate their clinical value in SLE.

METHODS

Serum levels of antibodies against carbamylated-vimentin (anti-Carp) were measured by enzyme immunosorbent assay in 100 patients with SLE, 76 with RA, 17 with primary Sjögren syndrome (pSS), and 68 healthy controls. Data analyses between anti-Carp antibodies and other laboratory measures were performed using SPSS 24 software for Windows.

RESULTS

The levels of serum anti-CarP antibodies in patients with SLE were significantly higher than those in healthy controls. In addition, anti-CarP antibodies were present in SLE patients lacking the disease-specific antibodies, including anti-Smith-negative patients (24.4%, 21/86), anti-dsDNA-negative patients (29.3%, 12/41), anti-nucleosome-negative patients (21.4%, 9/42), and antiribosomal P protein antibody-negative patients (23.7%, 18/76). There were significant differences between the anti-CarP-positive and anti-CarP-negative SLE patients in clinical and laboratory features, such as age, erythrocyte sedimentation rate (ESR), C-reactive protein, rheumatoid factor, third-generation cyclic citrullinated peptide (CCP3), anticardiolipin, D-dipolymer, complement 3, immunoglobulin G (IgG), red blood cell count (RBC) and hemoglobin. After adjusting for age and disease duration, the high levels of anti-CarP antibodies were still correlated with low RBC, hemoglobin and high ESR, IgG and CCP3. Active SLE patients demonstrated higher anti-CarP IgG than inactive patients. Moreover, the levels of anti-CarP were significantly higher in SLE patients with arthralgia and/or arthritis than in those without joint involvement.

CONCLUSIONS

Anti-CarP antibodies were present in SLE patients and associated with the disease severity. These might provide a potential supplement to other specific autoantibodies for diagnosis of SLE and serve as a promising marker for measuring joint damage in the disease.

Monocyte subsets involved in the development of systemic lupus erythematosus and rheumatoid arthritis

AbstractMonocytes are evolutionally conserved innate immune cells that play essential roles for the protection of the host against pathogens and also produce several inflammatory cytokines. Thus, the aberrant functioning of monocytes may affect not only host defense but also the development of inflammatory diseases. Monocytes are a heterogeneous population with phenotypical and functional differences. Most recent studies have shown that monocytes are divided into three subsets, namely classical, intermediate and non-classical subsets, both in humans and mice. Accumulating evidence showed that monocyte activation is associated with the disease progression in autoimmune diseases, such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). However, it remains to be determined how monocytes contribute to the disease process and which subset is involved. In this review, we discuss the pathogenic role of monocyte subsets in SLE and RA on the basis of current studies by ourselves and others to shed light on the suitability of monocyte-targeted therapies in these diseases.

ADAM17-Mediated Reduction in CD14++CD16+ Monocytes ex vivo and Reduction in Intermediate Monocytes With Immune Paresis in Acute Pancreatitis and Acute Alcoholic Hepatitis

Impaired immune responses and increased susceptibility to infection characterize acute inflammatory conditions such as pancreatitis and alcoholic hepatitis and are major causes of morbidity and mortality. However, the mechanisms that drive this apparent immune paresis remain poorly understood. Monocytes mediate host responses to damage and pathogens in health and disease, and three subsets of monocytes have been defined based on CD14 and CD16 expression. We sought to determine the changes in monocyte subsets in acute pancreatitis (AP) and acute alcoholic hepatitis (AAH), together with functional consequences and mechanisms that underlie this change. Peripheral blood mononuclear cells (PBMCs) from patients with AP or AAH were compared with healthy controls. Monocyte subsets were defined by HLA-DR, CD14, and CD16 expression. Changes in surface and intracellular protein expression and phosphorylation were determined by flow cytometry. Phenotype and function were assessed following stimulation with lipopolysaccharide (LPS) or other agonists in the presence of specific inhibitors of TNFα and a disintegrin and metalloproteinase 17 (ADAM17). Patients with AP and AAH had reduced CD14⁺⁺CD16⁺ intermediate monocytes compared to controls. Reduction of intermediate monocytes was recapitulated ex vivo by stimulating healthy control PBMCs with Toll-like receptor (TLR) agonists LPS, flagellin or polyinosilic:polycytidylic acid (poly I:C). Stimulation caused shedding of CD14 and CD16, which could be reversed using the ADAM17 inhibitor, TMI005 but not direct inhibitors of TNFα, a known ADAM17-target. Culturing PBMCs from healthy controls resulted in expansion of intermediate monocytes, which did not occur when LPS was in the culture medium. Cultured intermediate monocytes showed reduced expression of CX₃CR1, CCR2, TLR4, and TLR5. We found reduced migratory responses, intracellular signaling and pro-inflammatory cytokine production, and increased expression of IL-10. Stimulation with TLR agonists results in ADAM17-mediated shedding of phenotypic markers from CD16⁺ monocytes, leading to apparent “loss” of intermediate monocytes. Reduction in CD14⁺⁺CD16⁻ monocytes and increased CD14⁺⁺CD16⁺ is associated with altered responses in functional assays ex vivo. Patients with AP and AAH had reduced proportions of CD14⁺⁺CD16⁺ monocytes and reduced phosphorylation of NFκB and IL-6 production in response to bacterial LPS. Together, these processes may contribute to the susceptibility to infection observed in AP and AAH.

Nonclassical Monocytes in Health and Disease

Monocytes are innate blood cells that maintain vascular homeostasis and are early responders to pathogens in acute infections. There are three well-characterized classes of monocytes: classical (CD14+CD16−in humans and Ly6Chiin mice), intermediate (CD14+CD16+in humans and Ly6C+Treml4+in mice), and nonclassical (CD14−CD16+in humans and Ly6Cloin mice). Classical monocytes are critical for the initial inflammatory response. Classical monocytes can differentiate into macrophages in tissue and can contribute to chronic disease. Nonclassical monocytes have been widely viewed as anti-inflammatory, as they maintain vascular homeostasis. They are a first line of defense in recognition and clearance of pathogens. However, their roles in chronic disease are less clear. They have been shown to be protective as well as positively associated with disease burden. This review focuses on the state of the monocyte biology field and the functions of monocytes, particularly nonclassical monocytes, in health and disease.

HIV vaccine candidate activation of hypoxia and the inflammasome in CD14+ monocytes is associated with a decreased risk of SIVmac251 acquisition

Qualitative differences in the innate and adaptive responses elicited by different HIV vaccine candidates have not been thoroughly investigated. We tested the ability of the Aventis Pasteur live recombinant canarypox vector (ALVAC)-SIV, DNA-SIV and Ad26-SIV vaccine prime modalities together with two ALVAC-SIV + gp120 protein boosts to reduce the risk of SIVmac251 acquisition in rhesus macaques. We found that the DNA and ALVAC prime regimens were effective, but the Ad26 prime was not. The activation of hypoxia and the inflammasome in CD14+CD16- monocytes, gut-homing CCR5-negative CD4+ T helper 2 (TH2) cells and antibodies to variable region 2 correlated with a decreased risk of SIVmac251 acquisition. By contrast, signal transducer and activator of transcription 3 activation in CD16+ monocytes was associated with an increased risk of virus acquisition. The Ad26 prime regimen induced the accumulation of CX3CR1+CD163+ macrophages in lymph nodes and of long-lasting CD4+ TH17 cells in the gut and lungs. Our data indicate that the selective engagement of monocyte subsets following a vaccine prime influences long-term immunity, uncovering an unexpected association of CD14+ innate monocytes with a reduced risk of SIVmac251 acquisition.

The Potential Role of Trained Immunity in Autoimmune and Autoinflammatory Disorders

During induction of trained immunity, monocytes and macrophages undergo a functional and transcriptional reprogramming toward increased activation. Important rewiring of cellular metabolism of the myeloid cells takes place during induction of trained immunity, including a shift toward glycolysis induced through the mTOR pathway, as well as glutaminolysis and cholesterol synthesis. Subsequently, this leads to modulation of the function of epigenetic enzymes, resulting in important changes in chromatin architecture that enables increased gene transcription. However, in addition to the beneficial effects of trained immunity as a host defense mechanism, we hypothesize that trained immunity also plays a deleterious role in the induction and/or maintenance of autoimmune and autoinflammatory diseases if inappropriately activated.

Renal-infiltrating CD11c+ cells are pathogenic in murine lupus nephritis through promoting CD4+ T cell responses

Lupus nephritis (LN) is a major manifestation of systemic lupus erythematosus (SLE), causing morbidity and mortality in 40-60% of SLE patients. The pathogenic mechanisms of LN are not completely understood. Recent studies have demonstrated the presence of various immune cell populations in lupus nephritic kidneys of both SLE patients and lupus-prone mice. These cells may play important pathogenic or regulatory roles in situ to promote or sustain LN. Here, using lupus-prone mouse models, we showed the pathogenic role of a kidney-infiltrating CD11c⁺ myeloid cell population in LN. These CD11c⁺ cells accumulated in the kidneys of lupus-prone mice as LN progressed. Surface markers of this population suggest their dendritic cell identity and differentiation from lymphocyte antigen 6 complex (Ly6C)^low mature monocytes. The cytokine/chemokine profile of these renal-infiltrating CD11c⁺ cells suggests their roles in promoting LN, which was confirmed further in a loss-of-function in-vivo study by using an antibody-drug conjugate (ADC) strategy targeting CX₃ CR1, a chemokine receptor expressed highly on these CD11c⁺ cells. However, CX₃ CR1 was dispensable for the homing of CD11c⁺ cells into lupus nephritic kidneys. Finally, we found that these CD11c⁺ cells co-localized with infiltrating T cells in the kidney. Using an ex- vivo co-culture system, we showed that renal-infiltrating CD11c⁺ cells promoted the survival, proliferation and interferon-γ production of renal-infiltrating CD4⁺ T cells, suggesting a T cell-dependent mechanism by which these CD11c⁺ cells promote LN. Together, our results identify a pathogenic kidney-infiltrating CD11c⁺ cell population promoting LN progression, which could be a new therapeutic target for the treatment of LN.