Differential expression of chemokine receptors on peripheral blood B cells from patients with rheumatoid arthritis and systemic lupus erythematosus

Tolerogenic antigen-specific vaccine induces VISTA-enriched regulatory T cells and protects against arthritis in DRB1∗04:01 mice

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by joint inflammation, cartilage damage, and bone erosion. Despite improvements with the introduction of biological disease-modifying anti-rheumatic drugs (DMARDs), RA remains an incurable life-long disease. Advancements in peptide-based vaccination may open new avenues for treating autoimmune diseases, including RA, by inducing immune tolerance while maintaining normal immune function. We have already demonstrated the efficacy of a potent vaccine against RA, consisting of the mouse major histocompatibility complex class II (Aq) protein bound to the immunodominant type II collagen peptide COL2259-273, which needed to be galactosylated at position 264. To translate the vaccine to humans and to further enhance vaccine efficacy, we modified the glycine residue at position 265 and conjugated it with the human DRB1∗04:01 molecule. Remarkably, this modified vaccine (named DR4-AL179) provided robust effectiveness in suppressing arthritis in DRB1∗04:01-expressing mice without the need for galactosylation at position 264. DR4-AL179 vaccination induces tolerance involving multiple immunoregulatory pathways, including the activation of V-type immunoglobulin domain-containing suppressor of T cell activation (VISTA)-positive nonconventional regulatory T cells, which contribute to a potent suppressive response preventing arthritis development in mice. This modified RA vaccine offers a novel therapeutic potential for human autoimmune diseases.

B Cell Activation, Differentiation, and Their Potential Molecular Mechanisms in Osteoarthritic Synovial Tissue

Objective

The objective of this study was to characterize the activation and differentiation of B cells in the synovium of osteoarthritis (OA) and to explore the underlying molecular mechanisms.

Methods

Peripheral blood and synovial samples from OA patients at different stages were collected, and flow cytometry was employed to analyze the activation and differentiation of B cells. Immunofluorescence staining of joint synovium from OA mice at different stages was conducted to assess mice joint synovium B cell activation and differentiation. Co-culture experiments of synovial fibroblasts with B cells were performed to investigate the influence of synovial cells on B cell activation and differentiation. Finally, transcriptome analysis was utilized to identify potential key molecules and pathways.

Results

In OA patients, the infiltration, activation, and differentiation of B cells in synovium and peripheral blood exhibited distinct characteristics. Specifically, the proportion of activated CD86+ B cells and the differentiation marker HLA-DR+ increased with disease severity, whereas the proportion of the differentiation marker IgM decreased. The proportion of CD38+ B cells also decreased with increasing severity, although this change lacked statistical significance. Immunofluorescence staining of CD19+ and CD86+ cells in mice indicated increased expression with greater OA severity. Co-culture experiments demonstrated that OA synovial fibroblasts promoted B cell activation and differentiation, as evidenced by higher expression levels of CD86+ and HLA-DR+ in the OA group compared to controls. Additionally, the proportion of naive B cells decreased as disease severity progressed.

Conclusion

Synovial fibroblasts in OA have been shown to promote the differentiation and activation of B cells, indicating that B cells play a significant role in the pathogenesis of synovium inflammation in OA.

An analysis of single-cell data reveals therapeutic effects of AMG487 in experimental autoimmune uveitis

Uveitis, an ocular autoimmune disease that poses a significant threat to vision, is caused by immune cells erroneously attacking retinal cells and currently lacks specific and effective therapeutic interventions. The CXC chemokine receptor 3 (CXCR3) facilitates the migration of immune cells to sites of inflammation. AMG487, a CXCR3 antagonist, holds potential for treating autoimmune diseases by blocking immunes cells chemotaxis. However, its effects and mechanisms in uveitis remain unclear. Using single-cell assay for transposase-accessible chromatin sequencing and RNA sequencing, we observed increased expression of CXCR3 and chemotactic pathways in peripheral blood of Vogt-Koyanagi-Harada patients and cervical lymph nodes of experimental autoimmune uveitis mice. AMG487 treatment in experimental autoimmune uveitis was shown to be therapeutically effective. Analysis of flow cytometry and single-cell RNA sequencing in AMG487-treated mice revealed reduced expression of inflammatory genes in immune cells. Specifically, AMG487 decreased the proportion of plasma cell in B cells, restored the ratio between effector T cells and regulatory T cells, and diminished T helper (Th) 17 cell pathogenicity by suppressing highly inflammatory granulocyte-macrophage colony-stimulating factor-producing Th17 cells while enhancing anti-inflammatory interleukin-10-producing Th17 cells. Our study presents an exhaustive single-cell transcriptional analysis of immune cells under AMG487 treatment, thereby elucidating potential mechanisms and providing a potential reference for the development of novel therapeutic strategies for autoimmune diseases.

Functional validation of a novel STAT3 'variant of unknown significance' identifies a new case of STAT3 GOF syndrome and reveals broad immune cell defects

INTRODUCTION

Signal transducer and activator of transcription 3 (STAT3) orchestrates crucial immune responses through its pleiotropic functions as a transcription factor. Patients with germline monoallelic dominant negative or hypermorphic STAT3 variants, who present with immunodeficiency and/or immune dysregulation, have revealed the importance of balanced STAT3 signaling in lymphocyte differentiation and function, and immune homeostasis. Here, we report a novel missense variant of unknown significance in the DNA-binding domain of STAT3 in a patient who experienced hypogammaglobulinemia, lymphadenopathy, hepatosplenomegaly, immune thrombocytopenia, eczema, and enteropathy over a 35-year period.

METHODS

In vitro demonstration of prolonged STAT3 activation due to delayed dephosphorylation, and enhanced transcriptional activity, confirmed this to be a novel pathogenic STAT3 gain-of-function variant. Peripheral blood lymphocytes from this patient, and patients with confirmed STAT3 Gain-of-function Syndrome, were collected to investigate mechanisms of disease pathogenesis.

RESULTS

B cell dysregulation was evidenced by a loss of class-switched memory B cells and a significantly expanded CD19hiCD21lo B cell population, likely influenced by a skewed CXCR3+ TFH population. Interestingly, unlike STAT3 dominant negative variants, cytokine secretion by activated peripheral blood STAT3 GOF CD4+ T cells and frequencies of Treg cells were intact, suggesting CD4+ T cell dysregulation likely occurs at sites of disease rather than the periphery.

CONCLUSION

This study provides an in-depth case study in confirming a STAT3 gain-of-function variant and identifies lymphocyte dysregulation in the peripheral blood of patients with STAT3 gain-of-function syndrome. Identifying cellular biomarkers of disease provides a flow cytometric-based screen to guide validation of additional novel STAT3 gain-of-function variants as well as provide insights into putative mechanisms of disease pathogenesis.

Citrullinated Autoantigen-Specific T and B Lymphocytes in Rheumatoid Arthritis: Focus on Follicular T Helper Cells and Expansion by Coculture

OBJECTIVE

Rheumatoid arthritis (RA) is characterized by circulating anti-cyclic citrullinated peptide (CCP) autoantibodies (ACPAs), resulting in inflammation of the joints and other organs. We have established novel assays to assess immune cell subpopulations, including citrullinated antigen-specific (CAS) autoreactive B and T lymphocytes, in patients with RA.

METHODS AND RESULTS

We found that activated CD25+ T cells were markedly increased in patients with RA compared to healthy controls. Novel combinations of major histocompatibility complex class II citrulline epitope tetramers were developed, which enabled robust detection of CAS T cells and showed increases of CAS-naive T helper cells, Th1.17 cells, CAS total circulating T follicular helper (cTfh) cells, and cTfh1 cells in ACPA+ patients with RA. In addition, an innovative assay using dual labeling with CCP-biotin probes allowed for reproducible identification of primary CAS B cells after enrichment with advantages over existing detection methods. Furthermore, patient-derived immune cells were successfully expanded. Primary RA B cells were successfully cultured on novel feeder cell lines, whereas T cells were expanded ex vivo in the presence of interleukin-2 and citrullinated peptides, and subsequent alterations in cell frequencies were assessed.

CONCLUSION

Novel assays were established to reliably detect CAS T and B cells in patients with RA, and specific CAS-naive T helper cells, Th1.17 cells, cTfh cells, and cTfh1 cells were observed more frequently in RA. Based on these results, new coculture systems of disease-relevant cells are developed to simulate human secondary lymphoid tissues ex vivo. This technology will serve as a platform to identify therapies that modulate disease-specific immune cells.

Comprehensive structural investigation of a potent and selective CXCR4 antagonist via crosslink modification

Macrocyclization presents a valuable strategy for enhancing the pharmacokinetic and pharmacodynamic profiles of short bioactive peptides. The exploration of various macrocyclic characteristics, such as crosslinking tethers, ring size, and orientation, is generally conducted during the early stages of development. Herein, starting from a potent and selective C-X-C chemokine receptor 4 (CXCR4) cyclic heptapeptide antagonist mimicking the N-terminal region of CXCL12, we demonstrated that the disulfide bridge could be successfully replaced with a side-chain to side-chain lactam bond, which is commonly not enlisted among the conventional disulfide mimetics. An extensive investigation was carried out to explore the chemical space of the resulting peptides, including macrocyclization width, stereochemical configuration, and lactam orientation, all of which were correlated with biochemical activity. We identified a novel heptapeptide that fully replicates the pharmacological profile of the parent peptide on CXCR4, including its potency, selectivity, and antagonistic activity, while demonstrating enhanced stability in a reductive environment. At this stage, computational studies were instructed to shed light on how the lactam cyclization features influenced the overall structure of 21 and, in turn, its ability to interact with the receptor. We envisage that these findings can give new momentum to the use of lactam cyclization as a disulfide bond mimetic and contribute to the enhancement of the repertoire for peptide-based drug development, thereby paving the way for novel avenues in therapeutic innovation.

Disulfide bond replacement with non-reducible side chain to tail macrolactamization for the development of potent and selective CXCR4 peptide antagonists endowed with flanking binding sites

The present study describes a small library of peptides derived from a potent and selective CXCR4 antagonist (3), wherein the native disulfide bond is replaced using a side-chain to tail macrolactamization technique to vary ring size and amino acid composition. The peptides were preliminary assessed for their ability to interfere with the interaction between the receptor and anti-CXCR4 PE-conjugated antibody clone 12G5. Two promising candidates (13 and 17) were identified and further evaluated in a125I-CXCL12 competition binding assay, exhibiting IC50 in the low-nanomolar range. Furthermore, both candidates displayed high selectivity towards CXCR4 with respect to the cognate receptor CXCR7, ability to block CXCL12-dependent cancer cell migration, and receptor internalization, albeit at a higher concentration compared to 3. Molecular modeling studies on 13 and 17 produced a theoretical model that may serve as a guide for future modifications, aiding in the development of analogs with improved affinity. Finally, the study provides valuable insights into developing therapeutic agents targeting CXCR4-mediated processes, demonstrating the adaptability of our lead peptide 3 to alternative cyclization approaches and offering prospects for comprehensive investigations into the receptor region's interaction with its C-terminal region.

Disruption of memory B-cell trafficking by belimumab in patients with systemic lupus erythematosus

OBJECTIVES

Autoreactive memory B cells (MBCs) contribute to chronic and progressive courses in autoimmune diseases like SLE. The efficacy of belimumab (BEL), the first approved biologic treatment for SLE and LN, is generally attributed to depletion of activated naïve B cells and inhibition of B-cell activation. BEL's effect on MBCs is currently unexplained. We performed an in-depth cellular and transcriptomic analysis of BEL's impact on the blood MBC compartment in patients with SLE.

METHODS

A retrospective meta-analysis was conducted, pooling flow cytometry data from four randomized trials involving 1245 patients with SLE treated with intravenous BEL or placebo. Then, extensive MBC phenotyping was performed using high-sensitivity flow cytometry in patients with mild/moderate SLE and severe SLE/LN treated with subcutaneous BEL. Finally, transcriptomic characterization of surging MBCs was performed by single-cell RNA sequencing.

RESULTS

In BEL-treated patients, a significant increase in circulating MBCs, in a broad range of MBC subsets, was established at week 2, gradually returning to baseline by week 52. The increase was most prominent in patients with higher SLE disease activity, serologically active patients and patients aged ≤18 years. MBCs had a non-proliferating phenotype with a prominent decrease in activation status and downregulation of numerous migration genes.

CONCLUSION

Upon BEL initiation, an increase of MBCs was firmly established. In the small cohort investigated, circulating MBCs were de-activated, non-proliferative and demonstrated characteristics of disrupted lymphocyte trafficking, expanding on our understanding of the therapeutic mechanism of B-cell-activating factor inhibition by BEL.

TRIAL REGISTRATION

ClinicalTrials.gov, http://clinicaltrials.gov, NCT00071487, NCT00410384, NCT01632241, NCT01649765, NCT03312907, NCT03747159.

CXCR4: from B-cell development to B cell-mediated diseases

Chemokine receptors are members of the G protein-coupled receptor superfamily. The C-X-C chemokine receptor type 4 (CXCR4), one of the most studied chemokine receptors, is widely expressed in hematopoietic and immune cell populations. It is involved in leukocyte trafficking in lymphoid organs and inflammatory sites through its interaction with its natural ligand CXCL12. CXCR4 assumes a pivotal role in B-cell development, ranging from early progenitors to the differentiation of antibody-secreting cells. This review emphasizes the significance of CXCR4 across the various stages of B-cell development, including central tolerance, and delves into the association between CXCR4 and B cell-mediated disorders, from immunodeficiencies such as WHIM (warts, hypogammaglobulinemia, infections, and myelokathexis) syndrome to autoimmune diseases such as systemic lupus erythematosus. The potential of CXCR4 as a therapeutic target is discussed, especially through the identification of novel molecules capable of modulating specific pockets of the CXCR4 molecule. These insights provide a basis for innovative therapeutic approaches in the field.

Immune profiling of responses to influenza vaccination in patients with myeloproliferative neoplasms

Myeloproliferative neoplasms (MPNs) are associated with immune dysregulation and increased susceptibility to infection, emphasizing the importance of vaccination for patients. This pilot study evaluated immune responses to influenza vaccination in MPN patients compared with healthy donors using mass cytometry and serology. We observed diminished CXCR5+ B-cell, CXCR3+ T-cell, activated CD127+ memory T-cell subsets, and a trend toward lower hemagglutinin inhibition titer in MPN patients. These results indicate that patients with MPN exhibit distinct responses to influenza vaccination suggestive of impaired migration to lymphoid organs and T-cell maturation which may impact the development of protective immunity.

Examining B-cell dynamics and responsiveness in different inflammatory milieus using an agent-based model

INTRODUCTION

B-cells are essential components of the immune system that neutralize infectious agents through the generation of antigen-specific antibodies and through the phagocytic functions of naïve and memory B-cells. However, the B-cell response can become compromised by a variety of conditions that alter the overall inflammatory milieu, be that due to substantial, acute insults as seen in sepsis, or due to those that produce low-level, smoldering background inflammation such as diabetes, obesity, or advanced age. This B-cell dysfunction, mediated by the inflammatory cytokines Interleukin-6 (IL-6) and Tumor Necrosis Factor-alpha (TNF-α), increases the susceptibility of late-stage sepsis patients to nosocomial infections and increases the incidence or severity of recurrent infections, such as SARS-CoV-2, in those with chronic conditions. We propose that modeling B-cell dynamics can aid the investigation of their responses to different levels and patterns of systemic inflammation.

METHODS

The B-cell Immunity Agent-based Model (BCIABM) was developed by integrating knowledge regarding naïve B-cells, short-lived plasma cells, long-lived plasma cells, memory B-cells, and regulatory B-cells, along with their various differentiation pathways and cytokines/mediators. The BCIABM was calibrated to reflect physiologic behaviors in response to: 1) mild antigen stimuli expected to result in immune sensitization through the generation of effective immune memory, and 2) severe antigen challenges representing the acute substantial inflammation seen during sepsis, previously documented in studies on B-cell behavior in septic patients. Once calibrated, the BCIABM was used to simulate the B-cell response to repeat antigen stimuli during states of low, chronic background inflammation, implemented as low background levels of IL-6 and TNF-α often seen in patients with conditions such as diabetes, obesity, or advanced age. The levels of immune responsiveness were evaluated and validated by comparing to a Veteran's Administration (VA) patient cohort with COVID-19 infection known to have a higher incidence of such comorbidities.

RESULTS

The BCIABM was successfully able to reproduce the expected appropriate development of immune memory to mild antigen exposure, as well as the immunoparalysis seen in septic patients. Simulation experiments then revealed significantly decreased B-cell responsiveness as levels of background chronic inflammation increased, reproducing the different COVID-19 infection data seen in a VA population.

CONCLUSION

The BCIABM proved useful in dynamically representing known mechanisms of B-cell function and reproduced immune memory responses across a range of different antigen exposures and inflammatory statuses. These results elucidate previous studies demonstrating a similar negative correlation between the B-cell response and background inflammation by positing an established and conserved mechanism that explains B-cell dysfunction across a wide range of phenotypic presentations.

Cellular mechanisms associated with sub-optimal immune responses to SARS-CoV-2 bivalent booster vaccination in patients with Multiple Myeloma

BACKGROUND

The real-world impact of bivalent vaccines for wild type (WA.1) and Omicron variant (BA.5) is largely unknown in immunocompromised patients with Multiple Myeloma (MM). We characterize the humoral and cellular immune responses in patients with MM before and after receiving the bivalent booster, including neutralizing assays to identify patterns associated with continuing vulnerability to current variants (XBB1.16, EG5) in the current post-pandemic era.

METHODS

We studied the humoral and cellular immune responses before and after bivalent booster immunization in 48 MM patients. Spike binding IgG antibody levels were measured by SARS-CoV-2 spike binding ELISA and neutralization capacity was assessed by a SARS-CoV-2 multi-cycle microneutralization assays to assess inhibition of live virus. We measured spike specific T-cell function using the QuantiFERON SARS-CoV-2 (Qiagen) assay as well as flow-cytometry based T-cell. In a subset of 38 patients, high-dimensional flow cytometry was performed to identify immune cell subsets associated with lack of humoral antibodies.

FINDINGS

We find that bivalent vaccination provides significant boost in protection to the omicron variant in our MM patients, in a treatment specific manner. MM patients remain vulnerable to newer variants with mutations in the spike portion. Anti-CD38 and anti-BCMA therapies affect the immune machinery needed to produce antibodies.

INTERPRETATION

Our study highlights varying immune responses observed in MM patients after receiving bivalent COVID-19 vaccination. Specifically, a subgroup of MM patients undergoing anti-CD38 and anti-BCMA therapy experience impairment in immune cells such DCs, B cells, NK cells and TFH cells, leading to an inability to generate adequate humoral and cellular responses to vaccination.

FUNDING

National Cancer Institute (National Institutes of Health), National Institute of Allergy and Infectious Diseases (National Institutes of Health), NCI Serological Sciences Network for COVID-19 (SeroNet) and The Icahn School of Medicine at Mount Sinai.

Mass cytometry analysis reveals altered immune profiles in patients with coronary artery disease

Objective

The importance of inflammation in atherosclerosis is well accepted, but the role of the adaptive immune system is not yet fully understood. To further explore this, we assessed the circulating immune cell profile of patients with coronary artery disease (CAD) to identify discriminatory features by mass cytometry.

Methods

Mass cytometry was performed on patient samples from the BioHEART-CT study, gated to detect 82 distinct cell subsets. CT coronary angiograms were analysed to categorise patients as having CAD (CAD+) or having normal coronary arteries (CAD-).

Results

The discovery cohort included 117 patients (mean age 61 ± 12 years, 49% female); 79 patients (68%) were CAD+. Mass cytometry identified changes in 15 T-cell subsets, with higher numbers of proliferating, highly differentiated and cytotoxic cells and decreases in naïve T cells. Five T-regulatory subsets were related to an age and gender-independent increase in the odds of CAD incidence when expressing CCR2 (OR 1.12), CCR4 (OR 1.08), CD38 and CD45RO (OR 1.13), HLA-DR (OR 1.06) and Ki67 (OR 1.22). Markers of proliferation and differentiation were also increased within B cells, while plasmacytoid dendritic cells were decreased. This combination of changes was assessed using SVM models in discovery and validation cohorts (area under the curve = 0.74 for both), confirming the robust nature of the immune signature detected.

Conclusion

We identified differences within immune subpopulations of CAD+ patients which are indicative of a systemic immune response to coronary atherosclerosis. This immune signature needs further study via incorporation into risk scoring tools for the precision diagnosis of CAD.

Chemokines and chemokine receptors as promising targets in rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease that commonly causes inflammation and bone destruction in multiple joints. Inflammatory cytokines, such as IL-6 and TNF-α, play important roles in RA development and pathogenesis. Biological therapies targeting these cytokines have revolutionized RA therapy. However, approximately 50% of the patients are non-responders to these therapies. Therefore, there is an ongoing need to identify new therapeutic targets and therapies for patients with RA. In this review, we focus on the pathogenic roles of chemokines and their G-protein-coupled receptors (GPCRs) in RA. Inflamed tissues in RA, such as the synovium, highly express various chemokines to promote leukocyte migration, tightly controlled by chemokine ligand-receptor interactions. Because the inhibition of these signaling pathways results in inflammatory response regulation, chemokines and their receptors could be promising targets for RA therapy. The blockade of various chemokines and/or their receptors has yielded prospective results in preclinical trials using animal models of inflammatory arthritis. However, some of these strategies have failed in clinical trials. Nonetheless, some blockades showed promising results in early-phase clinical trials, suggesting that chemokine ligand-receptor interactions remain a promising therapeutic target for RA and other autoimmune diseases.

Cross-platform immunophenotyping of human peripheral blood mononuclear cells with four high-dimensional flow cytometry panels

Immunophenotyping using high dimensional flow cytometry is a central component of human immune system multi-omic studies. We present four high parameter flow cytometry panels for deep immunophenotyping of human peripheral blood mononuclear cells (PBMC). This set of four 25+ color panels include 64 cell surface markers to resolve broad immune compartment populations, as well as activation and memory of specific T, B, natural killer (NK), and myeloid lineages. Common lineage bridging markers are integrated into each panel to allow for inter-panel quality control through major lineage frequency verification. These panels were developed using a five laser BD Symphony A5 conventional cytometer and successfully transferred to a five laser Cytek Aurora spectral cytometer capable of acquiring the panels. Nine representative PBMC samples were stained with the four phenotyping panels and acquired on both instruments to evaluate population frequency and visual staining patterns for gating between the systems. Both instruments produced comparable high quality flow cytometry data and supported our decision to acquire samples on the spectral cytometer moving forward. This modular set of panels and instrument performance metrics provide guidelines for designing flow cytometry experiments suitable for longitudinal or cross-sectional immune profiling.

NCF4 dependent intracellular reactive oxygen species regulate plasma cell formation

Defective reactive oxygen species (ROS) production by genetically determined variants of the NADPH oxidase 2 (NOX2) complex component, NCF4, leads to enhanced production of autoantibodies to collagen type II (COL2) and severe collagen-induced arthritis (CIA) in mice. To further understand this process, we used mice harboring a mutation in the lipid endosomal membrane binding site (R58A) of NCF4 subunit. This mutation did not affect the extracellular ROS responses but showed instead decreased intracellular responses following B cell stimulation. Immunization with COL2 led to severe arthritis with increased antibody levels in Ncf4^58A mutated animals without significant effects on antigen presentation, autoreactive T cell activation and germinal center formation. Instead, plasma cell formation was enhanced and had altered CXCR3/CXCR4 expression. This B cell intrinsic effect was further confirmed with chimeric B cell transfer experiments and in vitro LPS or CD40L with anti-IgM stimulation. We conclude that NCF4 regulates the terminal differentiation of B cells to plasma cells through intracellular ROS.

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Ncf4^R58A selectively affects intracellular ROS production after stimulation.

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Decreased intracellular ROS in B cell promotes plasma cell formation intrinsically.

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BCR stimulation induced NOX2 complex-ROS regulates CXCR3 expression on plasma cell.

CD11c+ T-bet+ CD21hi B Cells Are Negatively Associated With Renal Impairment in Systemic Lupus Erythematosus and Act as a Marker for Nephritis Remission

Lupus nephritis (LN) is one of the most common manifestations of systemic lupus erythematosus (SLE), characterized by abnormal B cell activation and differentiation to memory or plasma effector cells. However, the role of these cells in the pathogenesis of LN is not fully understood, as well as the effect of induction therapy on B cell subsets, possibly associated with this manifestation, like aged-associated B cells (ABCs). Consequently, we analyzed the molecules defining the ABCs subpopulation (CD11c, T-bet, and CD21) through flow cytometry of blood samples from patients with lupus presenting or not LN, following up a small sub-cohort after six months of induction therapy. The frequency of ABCs resulted higher in LN patients compared to healthy subjects. Unexpectedly, we identified a robust reduction of a CD21^hi subset that was almost specific to LN patients. Moreover, several clinical and laboratory lupus features showed strong and significant correlations with this undefined B cell subpopulation. Finally, it was observed that the induction therapy affected not only the frequencies of ABCs and CD21^hi subsets but also the phenotype of the CD21^hi subset that expressed a higher density of CXCR5. Collectively, our results suggest that ABCs, and more importantly the CD21^hi subset, may work to assess therapeutic response since the reduced frequency of CD21^hi cells could be associated with the onset of LN.

B- and Plasma Cell Subsets in Autoimmune Diseases: Translational Perspectives

B lymphocytes play a central role in immunity owing to their unique antibody-producing capacity that provides protection against certain infections and during vaccination. In autoimmune diseases, B cells can gain pathogenic relevance through autoantibody production, antigen presentation, and proinflammatory cytokine secretion. Recent data indicate that B and plasma cells can function as regulators through the production of immunoregulatory cytokines and/or employing checkpoint molecules. In this study, we review the key findings that define subsets of B and plasma cells with pathogenic and protective functions in autoimmunity. In addition to harsh B-cell depletion, we discuss the strategies that have the potential to reinstall the balance of pathogenic and protective B cells with the potential of more specific and personalized therapies.

IL-27-producing B-1a cells suppress neuroinflammation and CNS autoimmune diseases

Regulatory B cells (Breg cells) that secrete IL-10 or IL-35 (i35-Breg) play key roles in regulating immunity in tumor microenvironment or during autoimmune and infectious diseases. Thus, loss of Breg function is implicated in development of autoimmune diseases while aberrant elevation of Breg prevents sterilizing immunity, exacerbates infectious diseases, and promotes cancer metastasis. Breg cells identified thus far are largely antigen-specific and derive mainly from B2-lymphocyte lineage. Here, we describe an innate-like IL-27-producing natural regulatory B-1a cell (i27-Breg) in peritoneal cavity and human umbilical cord blood. i27-Bregs accumulate in CNS and lymphoid tissues during neuroinflammation and confers protection against CNS autoimmune disease. i27-Breg immunotherapy ameliorated encephalomyelitis and uveitis through up-regulation of inhibitory receptors (Lag3, PD-1), suppression of Th17/Th1 responses, and propagating inhibitory signals that convert conventional B cells to regulatory lymphocytes that secrete IL-10 and/or IL-35 in eye, brain, or spinal cord. Furthermore, i27-Breg proliferates in vivo and sustains IL-27 secretion in CNS and lymphoid tissues, a therapeutic advantage over administering biologics (IL-10, IL-35) that are rapidly cleared in vivo. Mutant mice lacking irf4 in B cells exhibit exaggerated increase of i27-Bregs with few i35-Bregs, while mice with loss of irf8 in B cells have abundance of i35-Bregs but defective in generating i27-Bregs, identifying IRF8/BATF and IRF4/BATF axis in skewing B cell differentiation toward i27-Breg and i35-Breg developmental programs, respectively. Consistent with its developmental origin, disease suppression by innate i27-Bregs is neither antigen-specific nor disease-specific, suggesting that i27-Breg would be effective immunotherapy for a wide spectrum of autoimmune diseases.

A Selective Neutraligand for CXCL12/SDF-1α With Beneficial Regulatory Functions in MRL/Lpr Lupus Prone Mice

Dysregulation of CXCL12/SDF-1-CXCR4/CD184 signaling is associated with inflammatory diseases and notably with systemic lupus erythematosus. Issued from the lead molecule chalcone-4, the first neutraligand of the CXCL12 chemokine, LIT-927 was recently described as a potent analogue with improved solubility and stability. We aimed to investigate the capacity of LIT-927 to correct immune alterations in lupus-prone MRL/lpr mice and to explore the mechanism of action implemented by this small molecule in this model. We found that in contrast to AMD3100, an antagonist of CXCR4 and agonist of CXCR7, LIT-927 reduces the excessive number of several B/T lymphocyte subsets occurring in the blood of sick MRL/lpr mice (including CD3⁺/CD4^-/CD8^-/B220⁺ double negative T cells). In vitro, LIT-927 downregulated the overexpression of several activation markers on splenic MRL/lpr lymphocytes. It exerted effects on the CXCR4 pathway in MRL/lpr CD4⁺ T spleen cells. The results underline the importance of the CXCL12/CXCR4 axis in lupus pathophysiology. They indicate that neutralizing CXCL12 by the neutraligand LIT-927 can attenuate hyperactive lymphocytes in lupus. This mode of intervention might represent a novel strategy to control a common pathophysiological mechanism occurring in inflammatory diseases.

#CXCR5/CXCL13 pathway, a key driver for migration of regulatory B10 cells, is defective in patients with rheumatoid arthritis

OBJECTIVES

Chemokines (CKs) are key players of immune-cell homing and differentiation. CK receptors (CKRs) can be used to define T-cell functional subsets. We aimed to characterize the CKR profile of the regulatory B-cell subset B10+ cells and investigate the CKs involved in their migration and differentiation in healthy donors (CTLs) and patients with rheumatoid arthritis (RA).

METHODS

RNA sequencing and cytometry were used to compare CKR expression between B10+ and B10neg cells. Migration of B10+ and B10neg cells and interleukin 10 (IL-10) secretion of B cells in response to recombinant CKs or synovial fluid (SF) were assessed.

RESULTS

CXCR5 was expressed at a higher level on the B10+ cell surface as compared with other B cells (referred to as B10neg cells). In line with this, its ligand CXCL13 preferentially attracted B10+ cells over B10neg cells. Interestingly, synovial fluid from RA patients contained high levels of CXCL13 and induced strong and preferential migration of B10+ cells. Besides its role in attracting B10+ cells, CXCL13 also promoted IL-10 secretion by B cells. In RA patients, the level of CXCR5 on B cell surface was reduced. The preferential migration of RA B10+ cells toward CXCL13-rich SF was lost and CXCL13 stimulation triggered less IL-10 secretion than in healthy donors.

CONCLUSION

Our results identify that the CXCR5/CXCL13 axis is essential for B10+ cell biology but is defective in RA. Restoring the preferential migration of B10+ within the affected joints to better control inflammation may be part of therapeutic approach for RA.

Modulation of the chemokine/chemokine receptor axis as a novel approach for glioma therapy

Chemokines are a large subfamily of cytokines known for their ability to facilitate cell migration, most notably leukocytes, throughout the body. Chemokines are necessary for a functioning immune system in both health and disease and have received considerable attention for their roles in orchestrating temporal-spatial regulation of immune cell populations in cancer. Gliomas comprise a group of common central nervous system (CNS) primary tumors that are extremely challenging to treat. Immunotherapy approaches for highly malignant brain tumors offer an exciting new avenue for therapeutic intervention but so far, have seen limited successful clinical outcomes. Herein we focus on important chemokine/chemokine receptor systems in the regulation of pro- and anti-tumor mechanisms, highlighting potential therapeutic advantages of modulating these systems in malignant gliomas and other cancers.

Iguratimod promotes transformation of mononuclear macrophages in elderly patients with rheumatoid arthritis by nuclear factor-κB pathway

BACKGROUND

The role of macrophages in rheumatoid arthritis (RA) and its mechanism have attracted much attention in RA pathogenesis. Macrophages accumulate in the synoviums of RA, and the proportion of M1 type pro-inflammatory macrophages is higher than that of M2 type anti-inflammatory macrophages, leading to the secretion of inflammatory molecules and the aggravation of inflammatory reaction, which has made macrophages a potential target of RA drugs. Iguratimod is a kind of cyclo-oxygenase-2 inhibitor that affects macrophage polarity. It is speculated that its anti-inflammatory and anti-rheumatic effects may be related to the regulation of macrophage M1/M2 ratio.

AIM

To investigate the effects of Iguratimod on the polarity of mononuclear macrophages in elderly patients with RA.

METHODS

Elderly patients with RA and joint effusion were selected, including 10 men and 25 women, with an average age of 66.37 ± 4.42 years. Patients were treated with oral administration of 25 mg Iguratimod (Iremod, State Food and Drug Administration Approval No. H20110084) twice daily for 12 wk. Disease Activity Score 28 and Health Assessment Questionnaire score were collected according to the disease severity before and after treatment. Venous blood and joint effusion fluid were collected, mononuclear macrophages were extracted and expression of cell surface markers CD86, CD64, CD163, and CD206 was analyzed by flow cytometry. The concentration of inflammatory factors interleukin (IL)-6, IL-1β, transforming growth factor-β, and IL-4 in the joint effusion fluid was analyzed by enzyme-linked immunosorbent assay. Expression of mononuclear cells inhibitor of nuclear factor-κB (IκB) and phosphorylated IκB in peripheral blood was analyzed by western blotting.

RESULTS

Disease Activity Score 28 score and Health Assessment Questionnaire score of patients treated with Iguratimod decreased significantly. The percentage of cell surface markers CD86 and CD64 decreased significantly, and the percentage of CD163 and CD206 increased significantly (P < 0.05). The inflammatory factors IL-6 and IL-1β decreased significantly, and transforming growth factor-β and IL-4 increased significantly. Western blot analysis showed that mononuclear cell inhibitor of nuclear factor-κB in peripheral blood was significantly increased after treatment, and its phosphorylation level was significantly decreased (P < 0.05).

CONCLUSION

Iguratimod can promote the transformation of mononuclear macrophages from M1 to M2 in elderly patients with RA by inhibiting the nuclear factor-κB pathway, thus improving symptoms of RA.

Alterations in T and B cell function persist in convalescent COVID-19 patients

Background

Emerging studies indicate that some coronavirus disease 2019 (COVID-19) patients suffer from persistent symptoms, including breathlessness and chronic fatigue; however, the long-term immune response in these patients presently remains ill-defined.

Methods

Here, we describe the phenotypic and functional characteristics of B and T cells in hospitalized COVID-19 patients during acute disease and at 3–6 months of convalescence.

Findings

We report that the alterations in B cell subsets observed in acute COVID-19 patients were largely recovered in convalescent patients. In contrast, T cells from convalescent patients displayed continued alterations with persistence of a cytotoxic program evident in CD8⁺ T cells as well as elevated production of type 1 cytokines and interleukin-17 (IL-17). Interestingly, B cells from patients with acute COVID-19 displayed an IL-6/IL-10 cytokine imbalance in response to Toll-like receptor activation, skewed toward a pro-inflammatory phenotype. Whereas the frequency of IL-6⁺ B cells was restored in convalescent patients irrespective of clinical outcome, the recovery of IL-10⁺ B cells was associated with the resolution of lung pathology.

Conclusions

Our data detail lymphocyte alterations in previously hospitalized COVID-19 patients up to 6 months following hospital discharge and identify 3 subgroups of convalescent patients based on distinct lymphocyte phenotypes, with 1 subgroup associated with poorer clinical outcome. We propose that alterations in B and T cell function following hospitalization with COVID-19 could affect longer-term immunity and contribute to some persistent symptoms observed in convalescent COVID-19 patients.

Funding

Provided by UKRI, Lister Institute of Preventative Medicine, the Wellcome Trust, The Kennedy Trust for Rheumatology Research, and 3M Global Giving.

Lymphocytes were examined during COVID-19 and at up to 6 months of convalescence

B cell changes seen during acute COVID-19 were largely restored in convalescence

T cells from convalescent COVID-19 patients displayed persistent changes

Lymphocyte signatures defined 3 convalescent patient groups, one with poorer outcomes

The coronavirus disease 2019 (COVID-19) pandemic, caused by a novel coronavirus strain, has resulted in >100 million infections worldwide. Emerging evidence suggests that some COVID-19 patients suffer persistent symptoms, including fatigue, fibrotic lung disease, and myalgia; however, the long-term immune response in these patients remains ill-defined. Here, we conducted an observational study examining lymphocyte populations in COVID-19 patients during hospitalization and at up to 6 months of convalescence. We identified a number of lymphocyte alterations that persisted in convalescent patients. Moreover, the compilation of lymphocyte parameters in convalescent COVID-19 patients identified 3 distinct patient subgroups, with 1 subgroup associated with poorer clinical outcome. Our study outlines lymphocyte changes in convalescent COVID-19 patients associated with negative effects on subsequent health.

Pathological role of activated mTOR in CXCR3+ memory B cells of rheumatoid arthritis

OBJECTIVES

B cells play an important pathological role in rheumatoid arthritis (RA). In this study, we investigated the role of metabolic regulator mTOR in B cells and its relevance to the pathology of RA.

METHODS

Peripheral blood mononuclear cells were isolated from 31 normal subjects and 86 RA patients and the gated B cells were assessed for mTOR phosphorylation and chemokine receptor expression. In vitro studies on peripheral blood B cells isolated from the control and RA patients investigated the molecular mechanisms.

RESULTS

Higher concentrations of CXCL10 (CXCR3 ligands) and lower percentages of CXCR3+ memory B cells were present in the peripheral blood of RA patients relative to the control. RA patients with high CXCL10 concentrations had smaller percentage of CXCR3+ memory B cells and high disease activity. One-year treatment with TNF inhibitors increased the percentage of CXCR3+ memory B cells and reduced serum CXCL10 concentrations. mTOR phosphorylation in B cells was further enhanced in RA patients, compared to the control, and was selectively enhanced in CXCR3+ memory B cells. mTOR phosphorylation in CXCR3+ memory B cells correlated with disease activity. In vitro, mTOR phosphorylation in B cells enhanced IL-6 production and increased RANKL expression.

CONCLUSION

mTOR activation in CXCR3+ memory B cells of RA patients is associated with disease activity, mediated through IL-6 production and RANKL expression. The obtained results also suggest that TNF inhibitors mediate an impact on the association between CXCL10 and mTOR activated CXCR3+ memory B cells.

Polymorphisms in CXCR3 ligands predict early CXCL9 recovery and severe chronic GVHD

Chronic graft-versus-host disease (cGVHD) is a major cause of mortality and morbidity after allogeneic stem cell transplantation (alloSCT). The individual risk of severe cGVHD remains difficult to predict and may involve CXCR3 ligands. This study investigated the role of single-nucleotide polymorphisms (SNPs) of CXCL4, CXCL9, CXCL10, and CXCL11, and their day +28 serum levels, in cGVHD pathogenesis. Eighteen CXCR3 and CXCL4, CXCL9-11 SNPs as well as peri-transplant CXCL9-11 serum levels were analyzed in 688 patients without (training cohort; n = 287) or with statin-based endothelial protection cohort (n = 401). Clinical outcomes were correlated to serum levels and SNP status. Significant polymorphisms were further analyzed by luciferase reporter assays. Findings were validated in an independent cohort (n = 202). A combined genetic risk comprising four CXCR3 ligand SNPs was significantly associated with increased risk of severe cGVHD in both training cohort (hazard ratio (HR) 2.48, 95% confidence interval (CI) 1.33-4.64, P = 0.004) and validation cohort (HR 2.95, 95% CI 1.56-5.58, P = 0.001). In reporter assays, significantly reduced suppressive effects of calcineurin inhibitors in constructs with variant alleles of rs884304 (P < 0.001) and rs884004 (P < 0.001) were observed. CXCL9 serum levels at day +28 after alloSCT correlated with both genetic risk and risk of severe cGVHD (HR 1.38, 95% CI 1.10-1.73, P = 0.006). This study identifies patients with high genetic risk to develop severe cGVHD.

B Cells with a Senescent-Associated Secretory Phenotype Accumulate in the Adipose Tissue of Individuals with Obesity

Senescent cells accumulate in the adipose tissue (AT) of individuals with obesity and secrete multiple factors that constitute the senescence-associated secretory phenotype (SASP). This paper aimed at the identification of B cells with a SASP phenotype in the AT, as compared to the peripheral blood, of individuals with obesity. Our results show increased expression of SASP markers in AT versus blood B cells, a phenotype associated with a hyper-metabolic profile necessary to support the increased immune activation of AT-derived B cells as compared to blood-derived B cells. This hyper-metabolic profile is needed for the secretion of the pro-inflammatory mediators (cytokines, chemokines, micro-RNAs) that fuel local and systemic inflammation.

Single Cell Transcriptomic Re-analysis of Immune Cells in Bronchoalveolar Lavage Fluids Reveals the Correlation of B Cell Characteristics and Disease Severity of Patients with SARS-CoV-2 Infection

The coronavirus disease 2019 (COVID-19) pandemic (severe acute respiratory syndrome coronavirus 2) is a global infectious disease with rapid spread. Some patients have severe symptoms and clinical signs caused by an excessive inflammatory response, which increases the risk of mortality. In this study, we reanalyzed scRNA-seq data of cells from bronchoalveolar lavage fluids of patients with COVID-19 with mild and severe symptoms, focusing on Ab-producing cells. In patients with severe disease, B cells seemed to be more activated and expressed more immunoglobulin genes compared with cells from patients with mild disease, and macrophages expressed higher levels of the TNF superfamily member B-cell activating factor but not of APRIL (a proliferation-inducing ligand). In addition, macrophages from patients with severe disease had increased pro-inflammatory features and pathways associated with Fc receptor-mediated signaling, compared with patients with mild disease. CCR2-positive plasma cells accumulated in patients with severe disease, probably because of increased CCL2 expression on macrophages from patients with severe disease. Together, these results support the hypothesis that different characteristics of B cells might be associated with the severity of COVID-19 infection.

Specific and selective induction of miR-124 in immune cells by the quinoline ABX464: a transformative therapy for inflammatory diseases

Inflammatory diseases are believed to develop as a result of dysregulated inflammatory responses to environmental factors on susceptible genetic backgrounds. Operating at the level of post-transcriptional gene regulation, miRNAs are a class of endogenous, small noncoding RNAs that can promote downregulation of protein expression by translational repression and/or mRNA degradation of target mRNAs involved in inflammation. MiR-124 is a crucial modulator of inflammation and innate immunity that could provide therapeutic restitution of physiological pathways lost in inflammatory diseases. A recently discovered small quinoline, ABX464, was shown to upregulate miR-124 in human immune cells. In vivo, in a proof-of-concept clinical study, ABX464 showed robust and consistent efficacy in ulcerative colitis (UC). In this review, we examine the current therapeutic options proposed for UC and discuss the drug candidate ABX464 in this context.

The biomarkers related to immune related adverse events caused by immune checkpoint inhibitors

The enthusiasm for immune checkpoint inhibitors (ICIs), an efficient tumor treatment model different from traditional treatment, is based on their unprecedented antitumor effect, but the occurrence of immune-related adverse events (irAEs) is an obstacle to the prospect of ICI treatment. IrAEs are a discrete toxicity caused by the nonspecific activation of the immune system and can affect almost all tissues and organs. Currently, research on biomarkers mainly focuses on the gastrointestinal tract, endocrine system, skin and lung. Several potential hypotheses concentrate on the overactivation of the immune system, excessive release of inflammatory cytokines, elevated levels of pre-existing autoantibodies, and presence of common antigens between tumors and normal tissues. This review lists the current biomarkers that might predict irAEs and their possible mechanisms for both nonspecific and organ-specific biomarkers. However, the prediction of irAEs remains a major clinical challenge to screen and identify patients who are susceptible to irAEs and likely to benefit from ICIs.

Multi-Omics Resolves a Sharp Disease-State Shift between Mild and Moderate COVID-19

We present an integrated analysis of the clinical measurements, immune cells, and plasma multi-omics of 139 COVID-19 patients representing all levels of disease severity, from serial blood draws collected during the first week of infection following diagnosis. We identify a major shift between mild and moderate disease, at which point elevated inflammatory signaling is accompanied by the loss of specific classes of metabolites and metabolic processes. Within this stressed plasma environment at moderate disease, multiple unusual immune cell phenotypes emerge and amplify with increasing disease severity. We condensed over 120,000 immune features into a single axis to capture how different immune cell classes coordinate in response to SARS-CoV-2. This immune-response axis independently aligns with the major plasma composition changes, with clinical metrics of blood clotting, and with the sharp transition between mild and moderate disease. This study suggests that moderate disease may provide the most effective setting for therapeutic intervention.

Altered Expression of CXCL13 and Its Chemokine Receptor CXCR5 on B Lymphocytes during Active Graves' Orbitopathy

PURPOSE

To characterize the phenotypic abnormalities of peripheral B cells in patients with Graves' orbitopathy (GO) and explore the role of chemokine CXC ligand 13 and its receptor type 5 (CXCL13/CXCR5) in relation to B-cell homeostasis using specific neutralizing antibodies.

METHODS

Adults with active GO (n = 22), inactive GO (n = 28), and healthy control subjects (n = 28) were included in the study. Peripheral B cells and B-cell subsets were quantified and analyzed for CXCR5 expression by flow cytometry. The serum CXCL13 concentration was measured by enzyme-linked immunosorbent assays. For chemotactic experiments, Transwell plates were used, and migrating B cells were further analyzed by flow cytometry.

RESULTS

Compared to healthy subjects, patients with active GO had a significantly higher number of CD19⁺ B cells and the CD19⁺CD27⁺ memory B-cell subset (P = .041 and P = .019, respectively), whereas a marginal increase in the number of these cells was found in patients with inactive GO (P = .062 and P = .087, respectively). Serum CXCL13 levels were significantly higher in patients with active GO (86.9 ± 30.4 pg/mL) than in those with inactive GO (41.7 ± 18.1 pg/mL; P < .001) and in healthy subjects (36.2 ± 7.8 pg/mL; P < .001). The increased CXCL13 concentration was positively and significantly correlated with the clinical activity score (r = 0.757, P < .001). Finally, serum from patients with active GO exerted a stronger chemotactic activity towards B cells and the CD19⁺CD27⁺ memory B-cell subset. Blocking CXCL13 or CXCR5 with neutralizing antibodies reduced B-cell migration by a mean of 20%.

CONCLUSIONS

Our data suggest that aberrant CXCL13/CXCR5 expression may contribute to the deficits in B-lymphocyte homeostasis observed in active GO.

Analysis of gene expression from systemic lupus erythematosus synovium reveals myeloid cell-driven pathogenesis of lupus arthritis

Arthritis is a common manifestation of systemic lupus erythematosus (SLE) yet understanding of the underlying pathogenic mechanisms remains incomplete. We, therefore, interrogated gene expression profiles of SLE synovium to gain insight into the nature of lupus arthritis (LA), using osteoarthritis (OA) and rheumatoid arthritis (RA) as comparators. Knee synovia from SLE, OA, and RA patients were analyzed for differentially expressed genes (DEGs) and also by Weighted Gene Co-expression Network Analysis (WGCNA) to identify modules of highly co-expressed genes. Genes upregulated and/or co-expressed in LA revealed numerous immune/inflammatory cells dominated by a myeloid phenotype, in which pathogenic macrophages, myeloid-lineage cells, and their secreted products perpetuate inflammation, whereas OA was characterized by fibroblasts and RA of lymphocytes. Genes governing trafficking of immune cells into the synovium by chemokines were identified, but not in situ generation of germinal centers (GCs). Gene Set Variation Analysis (GSVA) confirmed activation of specific immune cell types in LA. Numerous therapies were predicted to target LA, including TNF, NFκB, MAPK, and CDK inhibitors. Detailed gene expression analysis identified a unique pattern of cellular components and physiologic pathways operative in LA, as well as drugs potentially able to target this common manifestation of SLE.

OMIP-069: Forty-Color Full Spectrum Flow Cytometry Panel for Deep Immunophenotyping of Major Cell Subsets in Human Peripheral Blood

This 40-color flow cytometry-based panel was developed for in-depth immunophenotyping of the major cell subsets present in human peripheral blood. Sample availability can often be limited, especially in cases of clinical trial material, when multiple types of testing are required from a single sample or timepoint. Maximizing the amount of information that can be obtained from a single sample not only provides more in-depth characterization of the immune system but also serves to address the issue of limited sample availability. The panel presented here identifies CD4 T cells, CD8 T cells, regulatory T cells, γδ T cells, NKT-like cells, B cells, NK cells, monocytes and dendritic cells. For each specific cell type, the panel includes markers for further characterization by including a selection of activation and differentiation markers, as well as chemokine receptors. Moreover, the combination of multiple markers in one tube might lead to the discovery of new immune phenotypes and their relevance in certain diseases. Of note, this panel was designed to include only surface markers to avoid the need for fixation and permeabilization steps. The panel can be used for studies aimed at characterizing the immune response in the context of infectious or autoimmune diseases, monitoring cancer patients on immuno- or chemotherapy, and discovery of unique and targetable biomarkers. Different from all previously published OMIPs, this panel was developed using a full spectrum flow cytometer, a technology that has allowed the effective use of 40 fluorescent markers in a single panel. The panel was developed using cryopreserved human peripheral blood mononuclear cells (PBMC) from healthy adults (Table 1). Although we have not tested the panel on fresh PBMCs or whole blood, it is anticipated that the panel could be used in those sample preparations without further optimization. @ 2020 Cytek Biosciences, Inc. Cytometry Part A published by Wiley Periodicals LLC on behalf of International Society for Advancement of Cytometry.

Therapeutic Cytokine Inhibition Modulates Activation and Homing Receptors of Peripheral Memory B Cell Subsets in Rheumatoid Arthritis Patients

Memory B cells have known to play an important role in the pathogenesis of rheumatoid arthritis (RA). With the emergence of B cell-targeted therapies, the modulation of memory B cells appears to be a key therapeutic target. Human peripheral memory B cells can be distinguished based on the phenotypic expression of CD27 and IgD, characterizing the three major B cell subpopulations: CD27+IgD+ pre-switch, CD27+IgD- post-switch, and CD27-IgD- double-negative memory B cells. We evaluated different memory cell populations for activation markers (CD95 and Ki-67) and chemokine receptors (CXCR3 and 4) expressing B cells in active RA, as well as under IL6-R blockade by tocilizumab (TCZ) and TNF-α blockade by adalimumab (ADA). Memory B cells were phenotypically analyzed from RA patients at baseline, week 12, and week 24 under TCZ or ADA treatment, respectively. Using flow cytometry, surface expression of CD95, intracellular Ki-67, and surface expressions of CXCR3 and CXCR4 were determined. Compared with healthy donors (n = 40), the phenotypic analysis of RA patients (n = 80) demonstrated that all three types of memory B cells were activated in RA patients. Surface and intracellular staining of B cells showed a significantly higher percentage of CD95+ (p < 0.0001) and Ki-67+ (p < 0.0001) cells, with numerically altered CXCR3+ and CXCR4+ cells in RA. CD95 and Ki-67 expressions were highest in post-switch memory B cells, whereas CD19+CXCR3+ and CD19+CXCR4+ expressing cells were substantially higher in the pre-switch compartment. In all subsets of the memory B cells, in vivo IL-6R, and TNF-α blockade significantly reduced the enhanced expressions of CD95 and Ki-67. Based on our findings, we conclude that the three major peripheral memory B cell populations, pre-, post-switch, and double-negative B cells, are activated in RA, demonstrating enhanced CD95 and Ki-67 expressions, and varied expression of CXCR3 and CXCR4 chemokine receptors when compared with healthy individuals. This activation can be efficaciously modulated under cytokine inhibition in vivo.

Accumulation of synovial fluid CD19+CD24hiCD27+ B cells was associated with bone destruction in rheumatoid arthritis

Regulatory CD19⁺CD24^hiCD27⁺ B cells were proved to be numerically decreased and functionally impaired in the peripheral blood (PB) from rheumatoid arthritis (RA), with the potential of converting into osteoclast-priming cells. However, the distribution and function of CD19⁺CD24^hiCD27⁺ B cells in RA synovial fluid (SF) were unclear. In this study, we investigated whether RA SF CD19⁺CD24^hiCD27⁺ B cells were increased and associated with bone destruction. We found that the proportion of RA SF CD19⁺CD24^hiCD27⁺ B cells was increased significantly, and was positively correlated with swollen joint counts, tender joint counts and disease activity. CXCL12, CXCL13, CCL19 contributed to the recruitment of CD19⁺CD24^hiCD27⁺ B cells in RA SF. Notably, CD19⁺CD24^hiCD27⁺ B cells in the SF from RA expressed significantly more RANKL compared to OA and that in the PB from RA. Critically, RA CD19⁺CD24^hiCD27⁺ B cells promoted osteoclast (OC) differentiation in vitro, and the number of OCs was higher in cultures with RA SF CD19⁺CD24^hiCD27⁺ B cells than in those derived from RA PB. Collectively, these findings revealed the accumulation of CD19⁺CD24^hiCD27⁺ B cells in SF and their likely contribution to joint destruction in RA. Modulating the status of CD19⁺CD24^hiCD27⁺ B cells might provide novel therapeutic strategies for RA.

CC chemokine receptor 6 (CCR6) in the pathogenesis of systemic lupus erythematosus

The CC chemokine receptor 6 (CCR6) and its sole chemokine ligand, CCL20, are an intriguing pair that have been implicated in a growing number of inflammatory, autoimmune and malignant disease processes. Recent observations have also highlighted this chemokine axis in the regulation of humoral immune responses. Through this review article, we explore the emerging links of CCR6-CCL20 with an archetypal autoimmune disease of humoral dysregulation: systemic lupus erythematosus (SLE). CCR6 is expressed prominently on several immune cells involved in the pathogenesis of SLE, such as dendritic cells and T-helper 17 cells. CCR6's expression is correlated with disease activity and serological markers of disease severity, suggesting a possible role in disease pathogenesis. However, there are numerous holes in our understanding of the functions of CCR6 and CCL20, and future studies are required to determine if there are any diagnostic, prognostic or monitoring roles for these important molecules.

Autoantibodies against specific nuclear antigens are present in psoriatic disease and are diminished by secukinumab

Anti-nuclear antibodies (ANA) are frequently detected in patients with psoriasis (Ps) and psoriatic arthritis (PsA), but their target autoantigens remain unknown. We assessed antibody (ab) reactivity against 23 known nuclear antigens in patients with Ps and PsA and assess the effects of secukinumab (anti-IL17A) treatment on ANA levels. A total of 201 patients, 101 with Ps and 100 with PsA, and 50 ANA-negative healthy controls (HCs) were tested for ANAs by a line immunoassay testing reactivity to 23 nuclear antigens. Ab reactivity to at least 1 antigen was found in 20.4% psoriatic disease patients (25.7% Ps and 15% PsA) compared to 8% HCs (p = ns), the most frequent being against dense fine speckled 70 (DFS70) (6.5%). In Ps and PsA patients with secukinumab-induced remission, anti-DFS70 and other antigen-specific autoantibodies were diminished over time. No decline was noted for IgG abs against antigens from pathogens such as cytomegalovirus, Epstein-Barr virus and Helicobacter pylori. Autoantibody decrease was associated with significant reduction of plasmablasts, follicular B and follicular T cells. In conclusion, one third of antigen-specific ANA patients with psoriatic disease recognize DFS70. Secukinumab decreases nuclear antigen autoreactivity, plasmablasts, follicular B and follicular T cells, highlighting a new mechanism of its action.

CXC chemokine receptor 3 antagonist AMG487 shows potent anti-arthritic effects on collagen-induced arthritis by modifying B cell inflammatory profile

Several studies have suggested that chemokine receptors are important mediators of inflammatory response in rheumatoid arthritis (RA). B cells are also known to play an important role in RA pathology. C-X-C chemokine receptor type 3 (CXCR3) is considered a potential therapeutic target in different inflammatory diseases; however, the mechanism remains unclear. Here, we evaluated the potentially protective effect of AMG487, a selective CXCR3 antagonist, in collagen-induced arthritis (CIA) mouse model. CIA mice were treated with AMG487 (5 mg/kg) every 48 h, from day 21 until day 41. We then investigated the effect of AMG487 on NF-κB p65-, NOS2-, MCP-1-, TNF-α-, IFN-γ, IL-4-, and IL-27-producing CD19⁺ B cells in the spleen through flow cytometry. We also evaluated the mRNA and protein expression levels of these molecules using RT-PCR and western blotting in the knee tissues. Our results revealed that AMG487-treated mice showed decreased NF-κB p65-, NOS2-, MCP-1-, and TNF-α-, and increased IL-4-, and IL-27-producing CD19⁺ B cells compared with the control mice. Additionally, AMG487 treatment significantly down regulated NF-κB p65, NOS2, TNF-α, and IFN-γ, and upregulated IL-4 and IL-27 mRNA and protein expression levels compared with the control. Thus, our study shows that AMG487 exerts its anti-arthritic effect by potently downregulating inflammatory B cell signaling. Based on our observations, we propose that AMG487 could serve as a potential novel therapeutic agent for inflammatory and autoimmune diseases, including RA.

Resident Memory B Cells

In mammals, adaptive immunity is mediated by a broadly diverse repertoire of naive B and T lymphocytes that recirculate between secondary lymphoid organs. Initial antigen exposure promotes lymphocyte clonal expansion and differentiation, including the formation of memory cells. Antigen-specific memory cells are maintained at higher frequencies than their naive counterparts and have different functional and homing abilities. Importantly, a subset of memory cells, known as tissue-resident memory cells, is maintained without recirculating in nonlymphoid tissues, often at barrier surfaces, where they can be reactivated by antigen and rapidly perform effector functions that help protect the tissue in which they reside. Although antigen-experienced B cells are abundant at many barrier surfaces, their characterization as tissue-resident memory B (BRM) cells is not well developed. In this study, we describe the characteristics of memory B cells in various locations and discuss their possible contributions to immunity and homeostasis as bona fide BRM cells.

Peripheral B Cell Subsets in Autoimmune Diseases: Clinical Implications and Effects of B Cell-Targeted Therapies

Antibody-secreting cells (ASCs) play a fundamental role in humoral immunity. The aberrant function of ASCs is related to a number of disease states, including autoimmune diseases and cancer. Recent insights into activated B cell subsets, including naïve B cell to ASC stages and their resultant cellular disturbances, suggest that aberrant ASC differentiation occurs during autoimmune diseases and is closely related to disease severity. However, the mechanisms underlying highly active ASC differentiation and the B cell subsets in autoimmune patients remain undefined. Here, we first review the processes of ASC generation. From the perspective of novel therapeutic target discovery, prediction of disease progression, and current clinical challenges, we further summarize the aberrant activity of B cell subsets including specialized memory CD11c^hiT-bet⁺ B cells that participate in the maintenance of autoreactive ASC populations. An improved understanding of subgroups may also enhance the knowledge of antigen-specific B cell differentiation. We further discuss the influence of current B cell therapies on B cell subsets, specifically focusing on systemic lupus erythematosus, rheumatoid arthritis, and myasthenia gravis.

In Human Autoimmunity, a Substantial Component of the B Cell Repertoire Consists of Polyclonal, Barely Mutated IgG+ve B Cells

B cells are critical for promoting autoimmunity and the success of B cell depletion therapy in rheumatoid arthritis (RA) confirms their importance in driving chronic inflammation. Whilst disease specific autoantibodies are useful diagnostically, our understanding of the pathogenic B cell repertoire remains unclear. Defining it would lead to novel insights and curative treatments. To address this, we have undertaken the largest study to date of over 150 RA patients, utilizing next generation sequencing (NGS) to analyze up to 200,000 BCR sequences per patient. The full-length antigen-binding variable region of the heavy chain (IgGHV) of the IgG B cell receptor (BCR) were sequenced. Surprisingly, RA patients do not express particular clonal expansions of B cells at diagnosis. Rather they express a polyclonal IgG repertoire with a significant increase in BCRs that have barely mutated away from the germline sequence. This pattern remains even after commencing disease modifying therapy. These hypomutated BCRs are expressed by TNF-alpha secreting IgG^+veCD27^-ve B cells, that are expanded in RA peripheral blood and enriched in the rheumatoid synovium. A similar B cell repertoire is expressed by patients with Sjögren's syndrome. A rate limiting step in the initiation of autoimmunity is the activation of B cells and this data reveals that a sizeable component of the human autoimmune B cell repertoire consists of polyclonal, hypomutated IgG^+ve B cells, that may play a critical role in driving chronic inflammation.

Post-rituximab immunoglobulin M (IgM) hypogammaglobulinemia

Rituximab is a B cell depleting monoclonal antibody that targets the B cell-specific cell surface antigen CD20 and is currently used to treat several autoimmune diseases. The elimination of mature CD20-positive B lymphocytes committed to differentiate into autoantibody-producing plasma cells is considered to be the major effect of rituximab, that makes it a beneficial biological agent in treating autoimmune diseases. Hypogammaglobulinemia has been reported after rituximab therapy in patients with lymphoma and rheumatoid arthritis. Similar data are scarce for other autoimmune diseases. Low immunoglobulin G (IgG) or hypogammaglobulinemia has attracted the most attention because of its significant role in protective immunity. However, the incidence and clinical implications of low immunoglobulin M (IgM) or hypogammaglobulinemia have not been studied in detail. This review will focus on the frequency and the clinical concerns of low IgM levels that result as a consequence of the administration of rituximab. The etiopathogenic mechanisms underlying post-rituximab IgM hypogammaglobulinemia and its implications are presented. The long-term consequences, if any, are not known or documented. Multiple factors may be involved in whether IgG or IgM decreases secondary to rituximab therapy. It is possible that the autoimmune disease itself may be one of the important factors. The dose, frequency and number of infusions appear to be important variables. Post-rituximab therapy immunoglobulin levels return to normal. During this process. IgM levels take a longer time to return to normal levels when compared to IgG or other immunoglobulins. IgM deficiency persists after B cell repopulation to normal levels has occurred. Laboratory animals and humans deficient in IgM can have multiple infections. Specific pharmacologic agents or biologic therapy that address and resolve IgM deficiency are currently unavailable. If the clinical situation so warrants, then prophylactic antibiotics may be indicated and perhaps helpful. Research in this iatrogenic phenomenon will provide a better understanding of not only the biology of IgM, but also the factor(s) that control its production and regulation, besides its influence if any, on rituximab therapy.

Acute-onset Autoimmune Hepatitis in a Patient with Selective Immunoglobulin M Deficiency

Selective immunoglobulin M deficiency (SIGMD) is an uncommon primary immunodeficiency disorder. We herein report an SIGMD patient with autoimmune hepatitis. A 21-year-old Japanese man was transferred to our hospital because of acute liver dysfunction. His serum IgM level was low, whereas those of IgG and IgA were normal, indicating that he had SIGMD. We diagnosed him with acute-onset autoimmune hepatitis, and his liver function test findings gradually recovered with corticosteroid administration. Although SIGMD with autoimmune diseases has been reported, the clinical features and pathogenesis have not yet been clarified. We have summarized previous reports on SIGMD patients with autoimmune diseases.

Type I and II interferons commit to abnormal expression of chemokine receptor on B cells in patients with systemic lupus erythematosus

Memory B cells are increased in systemic lupus erythematosus (SLE) cases, but the qualitative abnormalities and induction mechanism of these cells are unclear. Here, we subclassified B cells by their chemokine receptor expression and investigated their induction mechanism. The peripheral blood of patients with SLE showed higher levels of CXCR5^- and CXCR3⁺ B cells. CXCR5^-CXCR3⁺ B cell levels were elevated in patients with active SLE, which decreased with improving disease conditions. Interferon (IFN)-γ stimulation increased CXCR3 expression, whereas IFN-β stimulation reduced CXCR5 expression in B cells. Furthermore, CXCR5^-CXCR3⁺ B cells were induced by a combination of IFN-β and IFN-γ stimulation. Renal tissue examination of patients with active lupus nephritis confirmed the presence of CD19⁺CXCR3⁺ B cells. Collectively, the results revealed qualitative abnormalities accompanying reduced CXCR5 expression via type I IFN and enhanced CXCR3 expression via type II IFN in SLE, suggesting their involvement in B cell infiltration into tissues and inflammatory pathogenesis.

Immune dysregulation in cancer patients developing immune-related adverse events

BACKGROUND

Up to 40% of cancer patients on immune checkpoint inhibitors develop clinically significant immune-related adverse events (irAEs). The role of host immune status and function in predisposing patients to the development of irAEs remains unknown.

METHODS

Sera from 65 patients receiving immune checkpoint inhibitors and 13 healthy controls were evaluated for 40 cytokines at pre-treatment, after 2-3 weeks and after 6 weeks and analysed for correlation with the development of irAEs.

RESULTS

Of the 65 cancer patients enrolled, 55% were women; the mean age was 65 years and 98% received anti-PD1/PDL1 therapy. irAEs occurred in 35% of cases. Among healthy controls, cytokine levels were stable over time and lower than those in cancer patients at baseline. Significant increases in CXCL9, CXCL10, CXCL11 and CXCL13 occurred 2 weeks post treatment, and in CXCL9, CXCL10, CXCL11, CXCL13, IL-10 and CCL26 at 6 weeks post treatment. Patients who developed irAEs had lower levels of CXCL9, CXCL10, CXCL11 and CXCL19 at baseline and exhibited greater increases in CXCL9 and CXCL10 levels at post treatment compared to patients without irAEs.

CONCLUSIONS

Patients who developed irAEs have lower baseline levels and greater post-treatment increases in multiple cytokine levels, suggesting that underlying immune dysregulation may be associated with heightened risk for irAEs.

Pathological roles of the homeostatic chemokine CXCL12

CXCL12 is a CXC chemokine that traditionally has been classified as a homeostatic chemokine. It contributes to physiological processes such as embryogenesis, hematopoiesis and angiogenesis. In contrast to these homeostatic functions, increased expression of CXCL12 in general, or of a specific CXCL12 splicing variant has been demonstrated in various pathologies. In addition to this increased or differential transcription of CXCL12, also upregulation of its receptors CXC chemokine receptor 4 (CXCR4) and atypical chemokine receptor 3 (ACKR3) contributes to the onset or progression of diseases. Moreover, posttranslational modification of CXCL12 during disease progression, through interaction with locally produced molecules or enzymes, also affects CXCL12 activity, adding further complexity. As CXCL12, CXCR4 and ACKR3 are broadly expressed, the number of pathologies wherein CXCL12 is involved is growing. In this review, the role of the CXCL12/CXCR4/ACKR3 axis will be discussed for the most prevalent pathologies. Administration of CXCL12-neutralizing antibodies or small-molecule antagonists of CXCR4 or ACKR3 delays disease onset or prevents disease progression in cancer, viral infections, inflammatory bowel diseases, rheumatoid arthritis and osteoarthritis, asthma and acute lung injury, amyotrophic lateral sclerosis and WHIM syndrome. On the other hand, CXCL12 has protective properties in Alzheimer's disease and multiple sclerosis, has a beneficial role in wound healing and has crucial homeostatic properties in general.

Loss of CXCR3 expression on memory B cells in individuals with long-standing type 1 diabetes

AIMS/HYPOTHESIS

Islet-specific autoantibodies can predict the development of type 1 diabetes. However, it remains unclear if B cells, per se, contribute to the causal pancreatic immunopathology. We aimed to identify phenotypic signatures of disease progression among naive and memory B cell subsets in the peripheral blood of individuals with type 1 diabetes.

METHODS

A total of 69 participants were recruited across two separate cohorts, one for discovery purposes and the other for validation purposes. Each cohort comprised two groups of individuals with type 1 diabetes (one with newly diagnosed type 1 diabetes and the other with long-standing type 1 diabetes) and one group of age- and sex-matched healthy donors. The phenotypic characteristics of circulating naive and memory B cells were investigated using polychromatic flow cytometry, and serum concentrations of various chemokines and cytokines were measured using immunoassays.

RESULTS

A disease-linked phenotype was detected in individuals with long-standing type 1 diabetes, characterised by reduced C-X-C motif chemokine receptor 3 (CXCR3) expression on switched (CD27⁺IgD^-) and unswitched (CD27^intermediateIgD⁺) memory B cells. These changes were associated with raised serum concentrations of B cell activating factor and of the CXCR3 ligands, chemokine (C-X-C motif) ligand (CXCL)10 and CXCL11. A concomitant reduction in CXCR3 expression was also identified on T cells.

CONCLUSIONS/INTERPRETATION

Our data reveal a statistically robust set of abnormalities that indicate an association between type 1 diabetes and long-term dysregulation of a chemokine ligand/receptor system that controls B cell migration.

Upregulation of chemokine CXCL10 enhances chronic pulmonary inflammation in tree shrew collagen-induced arthritis

Chronic pulmonary inflammation (CPI) gives rise to serious lung injuries in rheumatoid arthritis (RA) patients. However, the molecular mechanism underlying the pathogenesis of RA-associated CPI remains little understood. Here we established a novel tree shrew-based collagen-induced arthritis (TsCIA) model to study RA-associated CPI. Our results showed that typical CPI but not fibrosis developed pathologically in the TsCIA model. Furthermore, abnormal up-regulation of pulmonary chemokine CXCL10 was directly associated with lung damage. Specific blockage of CXCR3 (a CXCL10 receptor) significantly decreased the severity of CPI by decreasing the recruitment of inflammatory cells. Therefore, CXCL10 is proposed as a key player responsible for the development of TsCIA-associated CPI. Our findings also suggest that CXCR3 could be developed as a potential diagnosis biomarker for RA-associated CPI.