Regulatory B cells (B10 cells) have a suppressive role in murine lupus: CD19 and B10 cell deficiency exacerbates systemic autoimmunity

Diversity of regulatory B cells: Markers and functions

Regulatory B cells (Bregs) are a functionally distinct B-cell subset involved in the maintenance of homeostasis and inhibition of inflammation. Studies, from the last two decades, have increased our understanding of cellular and molecular mechanisms involved in their generation, function, and to a certain extent phenotype. Current research endeavours to unravel the causes and consequences of Breg defects in disease, with increasing evidence highlighting the relevance of Bregs in promoting tumorigenic responses. Here we provide historical and emerging findings of the significance of Bregs in autoimmunity and transplantation, and how these insights have translated into the cancer field.

Lymphocytes Change Their Phenotype and Function in Systemic Lupus Erythematosus and Lupus Nephritis

Systemic lupus erythematosus (SLE) is a complex autoimmune disease, characterized by considerable changes in peripheral lymphocyte structure and function, that plays a critical role in commencing and reviving the inflammatory and immune signaling pathways. In healthy individuals, B lymphocytes have a major role in guiding and directing defense mechanisms against pathogens. Certain changes in B lymphocyte phenotype, including alterations in surface and endosomal receptors, occur in the presence of SLE and lead to dysregulation of peripheral B lymphocyte subpopulations. Functional changes are characterized by loss of self-tolerance, intra- and extrafollicular activation, and increased cytokine and autoantibody production. T lymphocytes seem to have a supporting, rather than a leading, role in the disease pathogenesis. Substantial aberrations in peripheral T lymphocyte subsets are evident, and include a reduction of cytotoxic, regulatory, and advanced differentiated subtypes, together with an increase of activated and autoreactive forms and abnormalities in follicular T cells. Up-regulated subpopulations, such as central and effector memory T cells, produce pre-inflammatory cytokines, activate B lymphocytes, and stimulate cell signaling pathways. This review explores the pivotal roles of B and T lymphocytes in the pathogenesis of SLE and Lupus Nephritis, emphasizing the multifaceted mechanisms and interactions and their phenotypic and functional dysregulations.

Current cell therapies for systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease in which multiple organs are damaged by the immune system. Although standard treatment options such as hydroxychloroquine (HCQ), glucocorticoids (GCs), and other immunosuppressive or immune-modulating agents can help to manage symptoms, they do not offer a cure. Hence, there is an urgent need for the development of novel drugs and therapies. In recent decades, cell therapies have been used for the treatment of SLE with encouraging results. Hematopoietic stem cell transplantation, mesenchymal stem cells, regulatory T (Treg) cell, natural killer cells, and chimeric antigen receptor T (CAR T) cells are advanced cell therapies which have been developed and evaluated in clinical trials in humans. In clinical application, each of these approaches has shown advantages and disadvantages. In addition, further studies are necessary to conclusively establish the safety and efficacy of these therapies. This review provides a summary of recent clinical trials investigating cell therapies for SLE treatment, along with a discussion on the potential of other cell-based therapies. The factors influencing the selection of common cell therapies for individual patients are also highlighted.

IL-10+ regulatory B cells mitigate atopic dermatitis by suppressing eosinophil activation

Atopic dermatitis (AD) presents significant therapeutic challenges due to its poorly understood etiology. Eosinophilia, a hallmark of allergic inflammation, is implicated in AD pathogenesis. Interleukin-10 (IL-10)-producing regulatory B (Breg) cells exhibit potent anti-inflammatory effects. However, their role in controlling AD-related eosinophilia is not well understood. To investigate the impact of eosinophils on AD, we employed IL-5Rα-deficient (Il5ra-/-) mice, which lack functional eosinophils. Induction of AD in these mice resulted in attenuated disease symptoms, underscoring the critical role of eosinophils in AD development. Additionally, the adoptive transfer of purified Breg cells into mice with AD significantly alleviated disease severity. Mechanistic studies revealed that IL-10 produced by Breg cells directly inhibits eosinophil activation and infiltration into the skin. In vitro experiments further confirmed that Breg cells inhibited eosinophil peroxidase secretion in an IL-10-dependent manner. Our collective findings demonstrate that IL-10 from Breg cells alleviates AD by suppressing eosinophil activation and tissue infiltration. This study elucidates a novel regulatory mechanism of Breg cells, providing a foundation for future Breg-mediated therapeutic strategies for AD.

The immunological understanding on germinal center B cells in psoriasis

The development of psoriasis is mainly driven by the dysregulation of T cells within the skin, marking a primary involvement of these cells in the pathogenesis. Although B cells are integral components of the immune system, their role in the initiation and progression of psoriasis is not as pivotal as that of T cells. The paradox of B cell suggests that, while it is crucial for adaptive immunity, B cells may contribute to the exacerbation of psoriasis. Numerous ideas proposed that there are potential relationships between psoriasis and B cells especially within germinal centers (GCs). Recent research projected that B cells might be triggered by autoantigens which then induced molecular mimicry to alter B cells activity within GC and generate autoantibodies and pro-inflammatory cytokines, form ectopic GC, and dysregulate the proliferation of keratinocytes. Hence, in this review, we gathered potential evidence indicating the participation of B cells in psoriasis within the context of GC, aiming to enhance our comprehension and advance treatment strategies for psoriasis thus inviting many new researchers to investigate this issue.

Soybean Agglutinin Alters the Gut Microbiota and Promotes Inflammation in Lupus-Prone MRL/lpr Mice

BACKGROUND

Certain foods can trigger flares in patients with systemic lupus erythematosus. Lectins in edible plants have been reported to increase inflammation.

OBJECTIVE

This study aimed to determine the effects of 1-time intake of soybean agglutinin (SBA) on the gut microbiota and immune response in lupus-prone MRL/MpJ (MRL)/lpr mice.

METHODS

MRL/MpJ-Faslpr/J (MRL/lpr) and MRL mice were randomly assigned into 4 groups (8 mice/group): MRL mice + phosphate-buffered saline (PBS) (CON), MRL mice + SBA (CS), MRL/lpr mice + PBS (LPR), and MRL/lpr + SBA (LS). PBS and SBA were orally administered at 16 wk of age, and all mice were killed 24 h after oral challenge. The disease phenotype, levels of proinflammatory cytokines, and composition of the intestinal microbiota were determined.

RESULTS

Interferon-gamma (IFN-γ) in the serum was significantly higher, whereas the level of serum IL-10 was significantly lower in LS mice than in LPR mice [fold change (FC) = 1.31 and FC = 0.36, respectively]. The expression levels of IL-6 and TNF-α in the spleen of LS mice were significantly higher than those in LPR mice (FC = 1.66 and FC = 1.96, respectively). The expression levels of IL-6, TNF-α, and IL-1β in the kidney were also significantly higher in LS mice than in LPR mice (FC = 2.89, FC = 3.78, and FC = 2.02, respectively). The relative abundances of Erysipelotrichaceae and Turicibacter in LS mice were significantly higher than those in LPR mice (FC = 1.73 and FC = 1.74, respectively). The percentage of Breg cells in the mesenteric lymph nodes was significantly lower in LS mice than in LPR mice (FC = 0.53) (P < 0.05). No change was found between SBA treatment or not in the control (MRL) mice.

CONCLUSIONS

One-time intake of SBA can promote the secretion of proinflammatory cytokines, downregulate Breg cells, and alter the intestinal flora in MRL/lpr mice within 24 h of oral challenge, which may contribute to exacerbation of lupus.

Evaluation of transcription factors and cytokine expressions of T-cell subsets in CD19 deficiency and their possible relationship with autoimmune disease

CD19 deficiency is a rare, predominantly antibody deficiency, and there are few studies showing that it can be seen in autoimmune diseases. The aim of study was evaluated to transcription factor and cytokine expressions of helper T (Th)-cell subsets in CD19 deficiency and the possible mechanism role of this factor expression in autoimmune disease. Transcription factor and cytokine expressions of Th1, Th2, Th17, and regulatory T (Treg) cells were investigated by real-time polymerase chain reaction (qPCR) method. In the study, in the patient/control comparison, transcription factor and cytokine expressions of Th1 (T-bet, STAT1, and STAT4) were found to be significantly downregulated, but IFN-γ was significantly upregulated in patients. Th2 factor GATA3, STAT6, IL-4, and IL-5 were significantly downregulated. For Th17, RORγt was downregulated while IL-22 was upregulated. In the heterozygous/control comparison, there was no significant change in gene expressions other than IL-5. T-bet, STAT1, GATA3, IL-4, RORγt, FoxP3, and TGF-β were significantly downregulated in the patient/heterozygous comparison. It was revealed for the first time that the expression of the transcription factors and cytokines in CD19 deficiency. These findings might be showing the predominance of Th1 factors and suppressed Treg factors which could be related with autoimmunity in CD19 deficiency.

Effect of BAFF blockade on the B cell receptor repertoire and transcriptome in a mouse model of systemic lupus erythematosus

Introduction

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease. Anti-B-cell-activating factor (BAFF) therapy effectively depletes B cells and reduces SLE disease activity. This research aimed to evaluate the effect of BAFF blockade on B cell receptor (BCR) repertoire and gene expression.

Methods

Through next-generation sequencing, we analyzed gene expression and BCR repertoire in MRL/lpr mice that received long-term anti-BAFF therapy. Based on gene expression profiles, we predicted the relative proportion of immune cells using ImmuCellAI-mouse, validating our predictions via flow cytometry and FluoroSpot.

Results

The loss of BCR repertoire diversity and richness, along with increased clonality and differential frequency distribution of the immunoglobulin heavy chain variable (IGHV) segment gene usage, were observed in BAFF-blockade mice. Meanwhile, the distribution of complementarity-determining region 3 (CDR3) length and CDR3 amino acid usage remained unaffected. BAFF blockade resulted in extensive changes in gene expression, particularly that of genes related to B cells and immunoglobulins. Besides, the tumor necrosis factor (TNF)-α responses and interferon (IFN)-α/γ were downregulated, consistent with the decrease in IFN-γ and TNF-α serum levels following anti-BAFF therapy. In addition, BAFF blockade significantly reduced B cell subpopulations and plasmacytoid dendritic cells, and caused the depletion of antibody-secreting cells.

Discussion

Our comparative BCR repertoire and transcriptome analyses of MRL/lpr mice subjected to BAFF blockade provide innovative insights into the molecular pathophysiology of SLE.

The role of regulatory B cells in immune regulation and childhood allergic asthma

BACKGROUND

As the most common chronic disease in childhood, asthma displays a major public health problem worldwide with the incidence of those affected rising. As there is currently no cure for allergic asthma, it is mandatory to get a better understanding of the underlying molecular mechanism.

MAIN BODY

By producing IgE antibodies upon allergen contact, B cells play a pivotal role in allergic asthma. Besides that, IL-10-secreting B cell subsets, namely regulatory B cells (Bregs), are reported in mice and humans to play a role in allergic asthma. In humans, several Breg subsets with distinct phenotypic and functional properties are identified among B cells at different maturational and differentiation stages that exert anti-inflammatory functions by expressing several suppressor molecules. Emerging research has focused on the role of Bregs in allergic asthma as well as their role for future diagnostic and preventive strategies.

CONCLUSION

Knowledge about the exact function of human Bregs in allergic asthma is still very limited. This review aims to summarize the current knowledge on Bregs. We discuss different human Breg subsets, several ways of Breg induction as well as the mechanisms through which they exert immunoregulatory functions, and their role in (childhood) allergic asthma.

Single-cell RNA sequencing analysis reveals the heterogeneity of IL-10 producing regulatory B cells in lupus-prone mice

Introduction

B cells can have both pathogenic and protective roles in autoimmune diseases, including systemic lupus erythematosus (SLE). Deficiencies in the number or immunosuppressive function of IL-10 producing regulatory B cells (Bregs) can cause exacerbated autoimmune inflammation. However, the exact role of Bregs in lupus pathogenesis has not been elucidated.

Methods

We carried out gene expression analysis by scRNA-seq to characterize differences in splenic Breg subsets and molecular profiles through stages of disease progression in lupus-prone mice. Transcriptome-based changes in Bregs from mice with active disease were confirmed by phenotypic analysis.

Results

We found that a loss of marginal zone (MZ) lineage Bregs, an increase in plasmablast/plasma cell (PB-PC) lineage Bregs, and overall increases in inflammatory gene signatures were characteristic of active disease as compared to Bregs from the pre-disease stage. However, the frequencies of both MZ Bregs and PB-PCs expressing IL-10 were significantly decreased in active-disease mice.

Conclusion

Overall, we have identified changes to the repertoire and transcriptional landscape of Breg subsets associated with active disease that provide insights into the role of Bregs in lupus pathogenesis. These results could inform the design of Breg-targeted therapies and interventions to restore Breg suppressive function in autoimmunity.

Diminished LAG3+ B cells correlate with exacerbated rheumatoid arthritis

BACKGROUND

Lymphocyte activation gene-3 (LAG3) positive B cells have been identified as a novel regulatory B cell subset, while the role of LAG3+ B cells in the pathogenesis of rheumatoid arthritis (RA) remains elusive.

MATERIALS AND METHODS

Peripheral blood mononuclear cells (PBMCs) from RA, osteoarthritis (OA) patients and healthy volunteers were collected for flow cytometry staining of LAG3+ B cells. Their correlation with RA patient clinical and immunological features were analyzed. Moreover, the frequencies of LAG3+ B cells in collagen-induced arthritis (CIA) mice and naive mice were also detected.

RESULTS

A significant decrease of LAG3+ B cells was observed in RA patients as compared with healthy individuals and OA patients. Notably, the frequencies of LAG3+ B cells were negatively correlated with tender joint count (r = -0.4301, p = .0157) and DAS28-ESR (r = -0.4018, p = .025) in RA patients. In CIA mice, LAG3+ B cell frequencies were also decreased and negatively correlated with the CIA arthritis score.

CONCLUSIONS

Impairment of LAG3+ B cells potentially contributes to RA development. Reconstituting LAG3+ B cells might provide novel therapeutic strategies for the persistent disease.Key messagesLAG3+ B cells have been identified as a novel regulatory B cell subset. However, its role in the pathogenesis of RA remains unknown.This study revealed the decreased frequency of LAG3+ B cells in RA patients. Notably, LAG3+ B cells were negatively correlated with RA disease activity including the tender joint count and DAS28-ESR.In CIA mice, LAG3+ B cell frequencies were also decreased and negatively correlated with the CIA arthritis score.Reconstitution of LAG3+ B cells might provide novel therapeutic strategies for disease perpetuation.

Autoimmunity and Carcinogenesis: Their Relationship under the Umbrella of Autophagy

The immune system and autophagy share a functional relationship. Both innate and adaptive immune responses involve autophagy and, depending on the disease’s origin and pathophysiology, it may have a detrimental or positive role on autoimmune disorders. As a “double-edged sword” in tumors, autophagy can either facilitate or impede tumor growth. The autophagy regulatory network that influences tumor progression and treatment resistance is dependent on cell and tissue types and tumor stages. The connection between autoimmunity and carcinogenesis has not been sufficiently explored in past studies. As a crucial mechanism between the two phenomena, autophagy may play a substantial role, though the specifics remain unclear. Several autophagy modifiers have demonstrated beneficial effects in models of autoimmune disease, emphasizing their therapeutic potential as treatments for autoimmune disorders. The function of autophagy in the tumor microenvironment and immune cells is the subject of intensive study. The objective of this review is to investigate the role of autophagy in the simultaneous genesis of autoimmunity and malignancy, shedding light on both sides of the issue. We believe our work will assist in the organization of current understanding in the field and promote additional research on this urgent and crucial topic.

TLR9 Signaling Is Required for the Porphyromonas gingivalis-Induced Activation of IL-10-Expressing B Cells

Immune cell pattern-recognition receptors such as Toll-like receptors (TLRs) play important roles in the regulation of host responses to periodontal pathogens. Our previous studies have demonstrated that immune regulatory B cells were activated by TLRs and alleviated periodontitis inflammation and bone loss. The purpose of this study is to determine the role of TLR9 signaling in the activation and IL-10 production of the primed-immune B cells in vitro. Wild-type (WT) and TLR9 knockout (TLR9KO) mice (C57BL/6 background, n = 5) were pre-immunized intraperitoneally with 1 × 108 formalin-fixed P. gingivalis and boosted once with 1 × 107 formalin-fixed P. gingivalis. Isolated splenocytes and purified B cells from each mouse were cultured with 1 × 108 formalin-fixed P. gingivalis for 48 h. Immunocytochemistry was performed to detect CD45+ IL-10+ cells. Levels of IL-10 expression and secretion in splenocytes and B cells were detected using qRT-PCR and ELISA, respectively. After stimulation with fixed P. gingivalis, the percentage of CD45+ IL-10+ B cells and the level of IL-10 expression were significantly increased (p < 0.01) in splenocytes and purified B cells isolated from WT mice. However, these changes were not observed in splenocytes and purified B cells from TLR9KO mice when the cells were treated with fixed P. gingivalis. The percentage of CD45+ IL-10+ B cells was significantly reduced in splenocytes and purified B cells from TLR9KO mice compared to those from WT mice when challenged with P. gingivalis. IL-10 expression in B cells from TLR9KO mice was significantly decreased compared to those from WT mice at both the mRNA and protein levels. Additionally, P. gingivalis-induced up-regulation of TNF-α mRNA expressions were consistently observed in B cells from both WT and TLR9KO mice. P. gingivalis-induced B10 activation and IL-10 production during adaptive responses by primed B cells requires TLR9 signaling and can be achieved independent of T-cell help.

Role of CD19+ CD5+ CD1d+ Bregs in maintaining the Th17/Treg balance in mice with systemic lupus erythematosus complicated with atherosclerosis

OBJECTIVE

In this study, we aimed to investigate Bregs, their regulatory effects on Th17/Treg cell balance, and the release of downstream inflammatory factors in a mouse model of low-density lipoprotein receptor (LDLr)^-/-  + Pristane.

METHODS

After the establishment of the mouse model of systemic lupus erythematosus (SLE) complicated with atherosclerosis (AS), 8-week-old LDLr^-/-  + Pristane mice (n = 10) were included in the SLE + AS group. Furthermore, 8-week-old MRL/lpr and C57 mice were used as the SLE and normal control groups, respectively (n = 10 per group). After feeding the mice a high-fat diet for 14 weeks, peripheral blood and spleen of mice were collected, and Bregs, Th17, and Treg cells and related inflammatory factors were detected by flow cytometry, enzyme-linked immunosorbent assay, and reverse-transcription polymerase chain reaction.

RESULTS

The number of Bregs and Tregs in spleen lymphocytes of SLE + AS mice significantly decreased compared with the C57 group (p < .05), whereas the number of Th17 cells significantly increased (p = .000). Furthermore, the proportion of Bregs showed a negative correlation with the Th17/Treg ratio (p = .03). Mice in the SLE + AS group showed higher serum interleukin (IL)-10, IL-17, and tumor necrosis factor-α levels than those in the SLE and C57 groups (p < .05). Furthermore, IL-35 and transforming growth factor (TGF)-β expression was reduced in the SLE + AS group compared with the C57 group (p < .05).

CONCLUSIONS

The proportion of Breg decreases was negatively associated with increased Th17/Treg which was increased in SLE + AS mice, indicating that Bregs may regulate Th17/Treg cell homeostasis and cytokine release via IL-35 and TGF-β production.

Vitamin D Presented In Vitro Immunomodulatory Property on T Lymphocyte-Related Cytokines in Systemic Lupus Erythematosus

Inflammatory T lymphocyte cytokines contribute to tissue damage in SLE patients. Vitamin D (Vit D) has a well-established immunomodulatory action, but few studies have addressed the effect of 1,25 dihydroxyvitamin D3 (1,25 (OH)2D3) on peripheral blood mononuclear cells (PBMCs) in SLE patients. The aim of this study was to evaluate the immnunomodulatory effect of 1,25 (OH)2D3 on T lymphocyte-related cytokines. Blood from 27 female SLE patients was collected for PBMC isolation and anti-DNA, complement, and serum 25 (OH)D3 level measurements. PBMCs were stimulated with anti-CD3/anti-CD28 in the presence or absence of dexamethasone or various concentrations of 1,25 (OH)2D3 for 48 h. We assessed IL-17A, IL-22, IL-21, IL-9, IFN-γ, IL-4, IL-10, IL-2, IL-6, and TNF by cytometric bead assay (CBA) and enzyme immune assay (ELISA) on culture supernatant. The mean age of patients was 36.2 (± 10.5 years) and the median Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) was 4 (0-6). The addition of 1,25 (OH)2D3 in PBMC culture reduced IL-17 A, IL-22, IL-9, and IFN-γ levels at 100 nM (p ≤ 0.0001). Furthermore, the addition of 1,25 (OH)2D3 at all concentrations increased IL-4 (p ≤ 0.0006), and 0.1 and 1 nM increased IL-10 (p ≤ 0.0004) and 0.1 nM increased IL-2 levels (p ≤ 0.0001). There was no difference regarding IL-21 and TNF levels. The addition of 1,25 (OH)2D3 in PBMC culture presented an inhibitory effect on proinflammatory cytokines and increased immunoregulatory cytokines in SLE patients, suggesting the beneficial effect of this vitamin.

Impact of dietary vitamin D on immunoregulation and disease pathology in lupus-prone NZB/W F1 mice

Vitamin D (VD) deficiency is a highly prevalent worldwide phenomenon and is extensively discussed as a risk factor for the development of systemic lupus erythematosus (SLE) and other immune-mediated diseases. In addition, it is now appreciated that VD possesses multiple immunomodulatory effects. This study aims to explore the impact of dietary VD intake on lupus manifestation and pathology in lupus-prone NZB/W F1 mice and identify the underlying immunological mechanisms modulated by VD. Here, we show that low VD intake accelerates lupus progression, reflected in reduced overall survival and an earlier onset of proteinuria, as well higher concentrations of anti-double-stranded DNA autoantibodies. This unfavorable effect gained statistical significance with additional low maternal VD intake during the prenatal period. Among examined immunological effects, we found that low VD intake consistently hampered the adoption of a regulatory phenotype in lymphocytes, significantly reducing both IL-10-expressing and regulatory CD4+ T cells. This goes along with a mildly decreased frequency of IL-10-expressing B cells. We did not observe consistent effects on the phenotype and function of innate immune cells, including cytokine production, costimulatory molecule expression, and phagocytic capacity. Hence, our study reveals that low VD intake promotes lupus pathology, likely via the deviation of adaptive immunity, and suggests that the correction of VD deficiency might not only exert beneficial functions by preventing osteoporosis but also serve as an important module in prophylaxis and as an add-on in the treatment of lupus and possibly other immune-mediated diseases. Further research is required to determine the most appropriate dosage, as too-high VD serum levels may also induce adverse effects, possibly also on lupus pathology.

B cell phenotype, activity, and function in idiopathic nephrotic syndrome

Idiopathic nephrotic syndrome (INS) is the most frequent glomerular disease in childhood. However, its underlying etiology mechanism lacks thorough understanding. Previous studies have described INS as a T cell functional disorder resulting in increased plasma lymphocyte-derived permeability factors. In children with frequent relapses of nephrotic syndrome, the mechanism underlying the therapeutic efficacy of CD20 monoclonal antibodies in depleting B cells may provide additional evidence in exploring the critical role of B lymphocytes in INS pathogenesis. Previous studies have proposed that RTX bound to CD20 through antibody-dependent and complement-dependent cytotoxicity and led to lytic clearance of B cells. Additionally, RTX exerted an effect by blocking the interaction between B and T cells or regulating homeostasis and functions of T cell subsets. Recent studies on the development, differentiation, and activation of B-lymphocytes in glomerular diseases have suggested that the B-lymphocytes participate in the INS pathogenesis through interaction with T cells, secretion of antibodies, or production of cytokines. In this study, we aimed to provide a detailed description of the current knowledge on the development, differentiation, activity, functions, and related regulating factors of B cells involved in INS. Thus, further understanding of the immunopathogenesis of INS may offer some opportunities in precisely targeting B cells during therapeutic interventions. IMPACT: The topic "B cells play a role in glomerular disease" is a novel point, which is not completely described previously. We described interactions between T and B cells and immunoglobulin, IgG, IgM, IgE, etc. as well in glomerular disease. The research of regulatory factors associated with B cell's function, like BAFF, is a hot topic in other diseases; however, it is rare in glomerular disease.

Inhibition of glutaminolysis ameliorates lupus by regulating T and B cell subsets and downregulating the mTOR/P70S6K/4EBP1 and NLRP3/caspase-1/IL-1β pathways in MRL/lpr mice

BACKGROUND AND AIM OF THE STUDY

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by lymphocyte imbalance. The differentiation and function of T and B cells receive regulation from intracellular energy metabolism. Herein, we aimed to investigate glutamine metabolism levels in SLE and explore the effects of modulating glutamine metabolism on T and B cell subsets and related signaling pathways in MRL/lpr lupus mice.

METHODS

We assessed intracellular glutamine metabolism in SLE patients and MRL/lpr mice by measuring intracellular glutamate and Glutaminase 1 (GLS1) protein levels. Intraperitoneal injection of the GLS1 inhibitor CB839 was performed to reduce glutamine metabolism and lupus-like manifestations in MRL/lpr mice were evaluated. The proportions and numbers of T and B cell subsets were determinedvia flow cytometry. Pathway-related proteins were detected using western blotting.

RESULTS

In this study, we reported that glutamine metabolism levels were aberrantly elevated in splenic mononuclear cells from MRL/lpr lupus mice, as well as in peripheral blood mononuclear cells (PBMCs) of SLE patients. Inhibition of glutamine metabolism by CB839 treatment for 8 weeks alleviated the lupus-like manifestations in MRL/lpr mice, including the kidney lesions, urinary protein/creatinine ratio, spleen index, and serum IgG1. Meanwhile, CB839 treatment ameliorated the depletion of IL-10 producing B cells (B10) and adjusted the Th1/TH2 and TH17/Treg imbalance. The inhibition of GLS1 by CB839 reduced the numbers of follicular helper T (TfH) cells and activated B cells in lupus mice. The proportions of mature B cells and plasma cells were not affected. Furthermore, the hyperactivated mTOR/P70S6K/4EBP1 and NLRP3/caspase-1/IL-1β pathways in MRL/lpr mice were reversed by CB839 treatment.

CONCLUSION

Our study confirmed the presence of abnormal intracellular glutamine metabolism in SLE and revealed potential therapeutic targets for this disease.

B cell-targeted therapies in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease of unknown etiology that primarily affects women of childbearing age. There is no disease more heterogeneous than SLE as patients experience a myriad of manifestations and unpredictable periods of heightened disease activity. This heterogeneity not only makes it difficult for treatment decisions and prognostication, but has made drug development quite challenging. Despite these challenges, belimumab, voclosporin, and anifromulab, approved by the United States Food and Drug Administration (FDA) to treat SLE or lupus nephritis (LN), enhanced our armamentarium of traditional therapies, such as hydroxychloroquine, corticosteroids, and immunosuppressives. However, there remains a dire need to develop therapies that offer greater efficacy and safety. Patients with SLE produce excessive amounts of autoantibodies and cytokines that result in inflammation and organ damage. While a considerable number of potential drug development targets exist, there has been much attention focused on B cells. Strategies have included direct B cell killing, modulation of B cell function, inhibition of molecules essential to B cell growth and survival, and acceleration of autoantibody clearance, to name just a few. In this article, we review SLE clinical trials evaluating experimental agents that target B cells or plasma cells.

Oxidative Phosphorylation Regulates Interleukin-10 Production in Regulatory B Cells via the Extracellular Signal-related Kinase Pathway

Regulatory B cells (Bregs) are immune cells that constrain autoimmune response and restrict inflammation via their expression of interleukin (IL)-10. However, the molecular mechanisms underlying Breg differentiation and IL-10 secretion remain unclear. Previous data suggest that cellular metabolism determines both the fate and function of these cells. Here, we suggest an essential role for mitochondrial oxidative phosphorylation (OXPHOS) in the regulation of IL-10 in these Bregs. We found that IL-10⁺ B cells from IL-10-green fluorescent protein-expressing mice had higher oxygen consumption rate than IL-10^- B cells. In addition, inhibition of OXPHOS decreased the expression of IL-10 in B cells. Further, suppression of OXPHOS diminished the expression of surface markers for Bregs and impaired their therapeutic effects in dextran sulfate sodium (DSS)-induced colitis. Mechanistically, mitochondrial OXPHOS was found to regulate the transcription factor HIF-1α through the extracellular signal-related kinase pathway. Taken together, this study reveals a strong correlation between mitochondrial OXPHOS and Breg phenotype/function, indicating OXPHOS as a therapeutic target in autoimmune diseases driven by Breg dysfunction.

Ex vivo-expanded human CD19+TIM-1+ regulatory B cells suppress immune responses in vivo and are dependent upon the TIM-1/STAT3 axis

Regulatory B cells (Breg) are a heterogenous population with immune-modulating functions. The rarity of human IL-10⁺ Breg makes translational studies difficult. Here we report ex vivo expansion of human B cells with in vivo regulatory function (expBreg). CD154-stimulation of human CD19⁺ B cells drives >900-fold expansion of IL-10⁺ B cells that is maintained in culture for 14 days. Whilst expBreg-mediated suppressive function is partially dependent on IL-10 expression, CRISPR-mediated gene deletions demonstrate predominant roles for TIM-1 and CD154. TIM-1 regulates STAT3 signalling and modulates downstream suppressive function. In a clinically relevant humanised mouse model of skin transplantation, expBreg prolongs human allograft survival. Meanwhile, CD19⁺CD73^-CD25⁺CD71⁺TIM-1⁺CD154⁺ Breg cells are enriched in the peripheral blood of human donors with cutaneous squamous cell carcinoma (SCC). TIM-1⁺ and pSTAT3⁺ B cells are also identified in B cell clusters within histological sections of human cutaneous SCC tumours. Our findings thus provide insights on Breg homoeostasis and present possible targets for Breg-related therapies.

Autoimmunity and Cancer-Two Sides of the Same Coin

Autoimmune disease results from the immune response against self-antigens, while cancer develops when the immune system does not respond to malignant cells. Thus, for years, autoimmunity and cancer have been considered as two separate fields of research that do not have a lot in common. However, the discovery of immune checkpoints and the development of anti-cancer drugs targeting PD-1 (programmed cell death receptor 1) and CTLA-4 (cytotoxic T lymphocyte antigen 4) pathways proved that studying autoimmune diseases can be extremely helpful in the development of novel anti-cancer drugs. Therefore, autoimmunity and cancer seem to be just two sides of the same coin. In the current review, we broadly discuss how various regulatory cell populations, effector molecules, genetic predisposition, and environmental factors contribute to the loss of self-tolerance in autoimmunity or tolerance induction to cancer. With the current paper, we also aim to convince the readers that the pathways involved in cancer and autoimmune disease development consist of similar molecular players working in opposite directions. Therefore, a deep understanding of the two sides of immune tolerance is crucial for the proper designing of novel and selective immunotherapies.

Serum cytokines to predict systemic lupus erythematosus clinical and serological activity

We aimed to explore the role of interleukin (IL)-6, interferon-gamma (IFNγ), IL-10, and tumor necrosis factor (TNF) as predictors of systemic lupus erythematosus (SLE) clinical and serological activity, and their correlation with the treatment received. We performed a retrospective analysis of 77 patients with SLE according to the 2012 Systemic Lupus International Collaborative Clinics (SLICC) criteria. The outcomes were serological activity (SA), active disease (AD), complete remission (CR), the low-disease activity state (LDAS), and immunosuppressive treatment. SA was present in 17.1%, AD in 17.3%, CR in 13%, and LDAS in 64.9% of patients. IL-6 values were higher in patients in SA, in AD, in those receiving steroids alone, and in patients without CR or LDAS (p < 0.05). IFNγ was associated with anti-double stranded DNA (dsDNA) antibodies positivity and immunosuppression, whereas IL-10 values were higher in patients with CR (p < 0.05). The IL6-IFN product was able to predict anti-double stranded DNA (anti-dsDNA) antibodies positivity (area under the receiver operating characteristic curve [AUC-ROC] = 0.705, 95% confidence interval [CI] 0.563-0.847), SA (AUC-ROC = 0.720, 95% CI 0.542-0.899), AD (AUC-ROC = 0.701, 95% CI 0.520-0.882), steroid treatment (AUC-ROC = 0.751, 95% CI 0.622-0.879), and the absence of LDAS (AUC-ROC = 0.700, 95% CI 0.558-0.834). The IL6-IFN/IL10 ratio predicted AD (AUC-ROC = 0.742, 955 CI 0.540-0.944), steroid treatment (AUC-ROC = 0.721, 95% CI 0.572-0.870), and the absence of LDAS (AUC-ROC = 0.694, 95% CI 0.536-0.853). In conclusion, IL-6, IL-10, and IFNγ might help to assess SLE serological and clinical activity. Their combination in the IL-6-IFN product and the IL-6xIFN to IL-10 ratio results in novel tools to determine and predict SA, AD, and LDAS. Prompt detection of SLE activity might allow a rapid intervention to avoid established or chronic damage.

B cells in pancreatic cancer stroma

Pancreatic cancer is a disease with high unmet clinical need. Pancreatic cancer is also characterised by an intense fibrotic stroma, which harbours many immune cells. Studies in both human and animal models have demonstrated that the immune system plays a crucial role in modulating tumour onset and progression. In human pancreatic ductal adenocarcinoma, high B-cell infiltration correlates with better patient survival. Hence, B cells have received recent interest in pancreatic cancer as potential therapeutic targets. However, the data on the role of B cells in murine models is unclear as it is dependent on the pancreatic cancer model used to study. Nevertheless, it appears that B cells do organise along with other immune cells such as a network of follicular dendritic cells (DCs), surrounded by T cells and DCs to form tertiary lymphoid structures (TLS). TLS are increasingly recognised as sites for antigen presentation, T-cell activation, B-cell maturation and differentiation in plasma cells. In this review we dissect the role of B cells and provide directions for future studies to harness the role of B cells in treatment of human pancreatic cancer.

Role of the innate and adaptive immune responses in the pathogenesis of systemic lupus erythematosus

OBJECTIVE

Systemic lupus erythematosus (SLE), the most common form of lupus, is a multisystemic rheumatic disease with different clinical features that generally affect women of childbearing age. The common symptoms of SLE are very similar to other autoimmune and non-autoimmune disorders, thereby it is known as a thousand faces disease. In this article, we are going to discuss some of the most updated information about immune system-related factors, cells, and cytokines involved in SLE pathogenesis.

METHODS

Different electronic databases, especially PubMed/MEDLINE, Scopus, and Google Scholar, were searched to review and analyze relevant literature on the role of innate and adaptive immune cells and cytokines in the pathogenesis of SLE. A search for relevant literature was accomplished using various keywords including systemic lupus erythematosus, apoptosis, autoantibodies, immunopathogenesis of SLE, adaptive and innate immune cells, inflammatory cytokines, hormones, etc. RESULTS AND CONCLUSION: The most important characteristic of SLE is the production of antibodies against different nuclear autoantigens like double-strand DNA and RNA. The depositions of the immune complexes (ICs) that are generated between autoantibodies and autoantigens, along with aberrant clearance of them, can lead to permanent inflammation and contribute to tissue or organ damage. Related mechanisms underlying the initiation and development of SLE have not been clarified yet. Although, defects in immune tolerance, enhanced antigenic load, hyperactivity of T cells, and inappropriate regulation of B cells contribute to the pathogenic autoantibodies generation. Besides, sex hormones that influence the immune system seem to act as triggers or protectors of SLE development.

Altered Phenotype and Enhanced Antibody-Producing Ability of Peripheral B Cells in Mice with Cd19-Driven Cre Expression

Given the importance of B lymphocytes in inflammation and immune defense against pathogens, mice transgenic for Cre under the control of Cd19 promoter (Cd19^Cre/+ mice) have been widely used to specifically investigate the role of loxP-flanked genes in B cell development/function. However, impacts of expression/insertion of the Cre transgene on the phenotype and function of B cells have not been carefully studied. Here, we show that the number of marginal zone B and B1a cells was selectively reduced in Cd19^Cre/+ mice, while B cell development in the bone marrow and total numbers of peripheral B cells were comparable between Cd19^Cre/+ and wild type C57BL/6 mice. Notably, humoral responses to both T cell-dependent and independent antigens were significantly increased in Cd19^Cre/+ mice. We speculate that these differences are mainly attributable to reduced surface CD19 levels caused by integration of the Cre-expressing cassette that inactivates one Cd19 allele. Moreover, our literature survey showed that expression of Cd19^Cre/+ alone may affect the development/progression of inflammatory and anti-infectious responses. Thus, our results have important implications for the design and interpretation of results on gene functions specifically targeted in B cells in the Cd19^Cre/+ mouse strain, for instance, in the context of (auto) inflammatory/infectious diseases.

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.

Endogenously produced catecholamines improve the regulatory function of TLR9-activated B cells

The sympathetic nervous system (SNS) contributes to immune balance by promoting anti-inflammatory B cells. However, whether B cells possess a self-regulating mechanism by which they modulate regulatory B cell (Breg) function is not well understood. In this study, we investigated the ability of B cells to synthesize their own catecholamines upon stimulation with different B cell activators and found that expression of the enzyme tyrosine hydroxylase (TH), required to generate catecholamines, is up-regulated by Toll-like receptor (TLR)9. This TLR9-dependent expression of TH correlated with up-regulation of adrenergic receptors (ADRs), enhanced interleukin (IL)-10 production, and overexpression of the co-inhibitory ligands programmed death ligand 1 (PD-L1) and Fas ligand (FasL). Moreover, concomitant stimulation of ß1-3-ADRs together with a B cell receptor (BCR)/TLR9 stimulus clearly enhances the anti-inflammatory potential of Bregs to suppress CD4 T cells, a crucial population in the pathogenesis of autoimmune diseases, like rheumatoid arthritis (RA). Furthermore, TH up-regulation was also demonstrated in B cells during the course of collagen-induced arthritis (CIA), a mouse model for the investigation of RA. In conclusion, our data show that B cells possess an autonomous mechanism to modulate their regulatory function in an autocrine and/or paracrine manner. These findings help to better understand the function of B cells in the regulation of autoimmune diseases and the interplay of SNS.

The sympathetic nervous system produces neurotransmitters such as catecholamines which contribute to immune balance by promoting anti-inflammatory B cells. This study shows that mouse B cells can themselves synthesize, sense, and transport catecholamines, which in turn modulate regulatory B cell function in an autocrine and/or paracrine manner to suppress T cell proliferation.

Indoleamine 2, 3-Dioxygenase Promotes Aryl Hydrocarbon Receptor-Dependent Differentiation Of Regulatory B Cells in Lung Cancer

Regulatory B cells (Breg) are IL-10 producing subsets of B cells that contribute to immunosuppression in the tumor microenvironment (TME). Breg are elevated in patients with lung cancer; however, the mechanisms underlying Breg development and their function in lung cancer have not been adequately elucidated. Herein, we report a novel role for Indoleamine 2, 3- dioxygenase (IDO), a metabolic enzyme that degrades tryptophan (Trp) and the Trp metabolite L-kynurenine (L-Kyn) in the regulation of Breg differentiation in the lung TME. Using a syngeneic mouse model of lung cancer, we report that Breg frequencies significantly increased during tumor progression in the lung TME and secondary lymphoid organs, while Breg were reduced in tumor-bearing IDO deficient mice (IDO^-/-). Trp metabolite L-Kyn promoted Breg differentiation in-vitro in an aryl hydrocarbon receptor (AhR), toll-like receptor-4-myeloid differentiation primary response 88, (TLR4-MyD88) dependent manner. Importantly, using mouse models with conditional deletion of IDO in myeloid-lineage cells, we identified a significant role for immunosuppressive myeloid-derived suppressor cell (MDSC)-associated IDO in modulating in-vivo and ex-vivo differentiation of Breg. Our studies thus identify Trp metabolism as a therapeutic target to modulate regulatory B cell function during lung cancer progression.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (third edition)

The third edition of Flow Cytometry Guidelines provides the key aspects to consider when performing flow cytometry experiments and includes comprehensive sections describing phenotypes and functional assays of all major human and murine immune cell subsets. Notably, the Guidelines contain helpful tables highlighting phenotypes and key differences between human and murine cells. Another useful feature of this edition is the flow cytometry analysis of clinical samples with examples of flow cytometry applications in the context of autoimmune diseases, cancers as well as acute and chronic infectious diseases. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid. All sections are written and peer-reviewed by leading flow cytometry experts and immunologists, making this edition an essential and state-of-the-art handbook for basic and clinical researchers.

The Role of B Cells in Head and Neck Cancer

Simple Summary

Host immunity has established its role in deciding the course of cancer evolution. As cellular and molecular components in the tumor microenvironment peripherally appear to be at a constant interplay, favoring either tumor control or progression, it is vital to decrypt the immunity elements, which demonstrate the potential to be harnessed towards cancer elimination. Head and neck cancer has been characterized as densely immune infiltrated but at the same time a highly immunosuppressive malignancy due to a negative equilibrium between active and dysfunctional immune cell populations. B-cells constitute the cornerstone of humoral immunity; however, their role in cancer has been vastly overlooked in comparison to other immune subtypes and reports from multiple studies fail to show agreement on their prognostic impact. This review focuses on the role of B-cells on head and neck cancer with the aim to highlight their effect on anti-cancer immunity, as well as their possible impact on immunotherapy outcomes.

Abstract

Head and neck cancer comprises a heterogenous, highly immune infiltrated malignancy, defined by a predominantly immunosuppressive tumor microenvironment (TME). In recent years, PD-1/PD-L1 immune checkpoint inhibitors have become the standard of care treatment, either as monotherapy or in combination with chemotherapy agents, thus revolutionizing the therapeutic landscape of recurrent/metastatic disease. As a result, preclinical research is increasingly focusing on TME composition and pathophysiology, aiming to comprehensively characterize the specific elements and interactions affecting anti-tumor immunity, as well as to unveil novel predictive biomarkers of immunotherapy outcomes. While T lymphocytic populations have been vastly explored regarding their effect on cancer development, B-cells constitute a far less investigated, yet possibly equally important, aspect of cancer immunity. B-cell presence, either as single cells or as part of tertiary lymphoid structures within the TME, has been associated with several anti-tumor defense mechanisms, such as antigen presentation, antibody production and participation in antibody-dependent cellular cytotoxicity, and has demonstrated prognostic significance for multiple types of malignancies. However, immunoregulatory B-cell phenotypes have also been identified both peripherally and within malignant tissue, bearing inhibitory effects on numerous immune response processes. Consequently, B-cells and their subsets demonstrate the potential to become valuable cancer biomarkers and acquire a leading role in future therapeutic strategies.

Maternal B Cell-Intrinsic MyD88 Signaling Mediates LPS-Driven Intrauterine Fetal Death

Immunological networks balance tolerance towards paternal alloantigens during pregnancy with normal immune response to pathogens. Subclinical infections can impact this balance and lead to preterm birth or even intrauterine fetal death (IUFD). We recently showed that loss of maternal B cells renders murine fetuses susceptible to IUFD after LPS exposure. Since the signaling pathway involved in this B-cell mediated response remains unclear, we aimed to understand the participation of MyD88 in this response using B-cell-specific MyD88-deficient (BMyD88-/-) mice. B cells isolated from wild-type (WT), BMyD88-/-, CD19-/- and MyD88-/- dams on gestational day (gd) 10 responded differently to LPS concerning cytokine secretion. In vivo LPS challenge on gd 10 provoked IUFD in CD19-/- mothers with functional MyD88, while fetuses from BMyD88-/- and MyD88-/- mice were protected. These outcomes were associated with altered cytokine levels in the maternal serum and changes in CD4+ T-cell responses. Overall, the loss of MyD88 signaling in maternal B cells prevents the activation of cytokine release that leads to IUFD. Thus, while MyD88 signaling in maternal B cells protects the mother from infection, it ultimately kills the fetus. Understanding the cellular mechanisms underlying infection-driven pregnancy complications is the first step to designing powerful therapeutic strategies in the future.

Characterization of Organ-Specific Regulatory B Cells Using Single-Cell RNA Sequencing

Regulatory B cells (Breg) are considered as immunosuppressive cells. Different subsets of Breg cells have been identified both in human beings and in mice. However, there is a lack of unique markers to identify Breg cells, and the heterogeneity of Breg cells in different organs needs to be further illuminated. In this study, we performed high-throughput single-cell RNA sequencing (scRNA-seq) and single-cell B-cell receptor sequencing (scBCR-seq) of B cells from the murine spleen, liver, mesenteric lymph nodes, bone marrow, and peritoneal cavity to better define the phenotype of these cells. Breg cells were identified based on the expression of immunosuppressive genes and IL-10-producing B (B10) cell-related genes, to define B10 and non-B10 subsets in Breg cells based on the score of the B10 gene signatures. Moreover, we characterized 19 common genes significantly expressed in Breg cells, including Fcrl5, Zbtb20, Ccdc28b, Cd9, and Ptpn22, and further analyzed the transcription factor activity in defined Breg cells. Last, a BCR analysis was used to determine the clonally expanded clusters and the relationship of Breg cells across different organs. We demonstrated that Atf3 may potentially modulate the function of Breg cells as a transcription factor and that seven organ-specific subsets of Breg cells are found. Depending on gene expression and functional modules, non-B10 Breg cells exhibited activated the TGF-β pathway, thus suggesting that non-B10 Breg cells have specific immunosuppressive properties different from conventional B10 cells. In conclusion, our work provides new insights into Breg cells and illustrates their transcriptional profiles and BCR repertoire in different organs under physiological conditions.

Transplantation of mesenchymal stem cells ameliorates systemic lupus erythematosus and upregulates B10 cells through TGF-β1

BACKGROUND

Considerable experimental and clinical evidences have proved that human umbilical cord mesenchymal stem cells (UC-MSCs) transplantation was powerful in systemic lupus erythematosus (SLE) treatment. MSCs could upregulate regulatory B cells (Bregs) in the mice model of the other immune disease. However, the regulation of MSCs on Bregs in SLE environment remains unclear.

METHODS

To assess the abilities of UC-MSCs to treat SLE, MSCs were transferred intravenously to 17- to 18-week-old MRL/lpr mice. Four weeks later, mice were sacrificed. Survival rates, anti-dsDNA antibodies and renal histology were evaluated. CD4+ T helper (Th) cell subgroups and interleukin (IL)-10+ Bregs (B10) in the spleen were quantitated by flow cytometry. The changes of transforming growth factor (TGF)-β1, IL-6 and indoleamine 2,3-dioxyenase (IDO) mRNAs expressed by MSCs after co-cultured with B cells were detected using real-time polymerase chain reaction (RT-PCR). MSCs were infected by lentivirus carrying TGF-β1 shRNAs, then MSCs with low expression of TGF-β1 were conducted for co-culture in vitro and transplantation experiments in vivo.

RESULTS

UC-MSCs transplantation could efficiently downregulate 24 h proteinuria and anti-dsDNA antibodies, correct Treg/Th17/Th1 imbalances and increase the frequency of B10 cells. The expression of TGF-β1 in MSCs was significantly increased after co-culture with B cells. Downregulation of TGF-β1 in MSCs could significantly attenuate the upregulation of B10 by MSCs in vitro and in vivo. Downregulation of TGF-β1 also compromised the immunomodulation effects of MSCs on Th17 and Treg cells and the therapeutic effects of MSC transplantation.

CONCLUSIONS

UC-MSCs could protect against SLE in mice and upregulate IL-10+ Bregs via TGF-β1.

B Cells and Autoantibodies in AIRE Deficiency

Autoimmune polyendocrine syndrome type 1 (APS-1) is a rare but severe monogenetic autoimmune endocrine disease caused by failure of the Autoimmune Regulator (AIRE). AIRE regulates the negative selection of T cells in the thymus, and the main pathogenic mechanisms are believed to be T cell-mediated, but little is known about the role of B cells. Here, we give an overview of the role of B cells in thymic and peripheral tolerance in APS-1 patients and different AIRE-deficient mouse models. We also look closely into which autoantibodies have been described for this disorder, and their implications. Based on what is known about B cell therapy in other autoimmune disorders, we outline the potential of B cell therapies in APS-1 and highlight the unresolved research questions to be answered.

Regulatory B cells, A to Z

B cells play a central role in the immune system through the production of antibodies. During the past two decades, it has become increasingly clear that B cells also have the capacity to regulate immune responses through mechanisms that extend beyond antibody production. Several types of human and murine regulatory B cells have been reported that suppress inflammatory responses in autoimmune disease, allergy, infection, transplantation, and cancer. Key suppressive molecules associated with regulatory B-cell function include the cytokines IL-10, IL-35, and TGF-β as well as cell membrane-bound molecules such as programmed death-ligand 1, CD39, CD73, and aryl hydrocarbon receptor. Regulatory B cells can be induced by a range of different stimuli, including microbial products such as TLR4 or TLR9 ligands, inflammatory cytokines such as IL-6, IL-1β, and IFN-α, as well as CD40 ligation. This review provides an overview of our current knowledge on regulatory B cells. We discuss different types of regulatory B cells, the mechanisms through which they exert their regulatory functions, factors that lead to induction of regulatory B cells and their role in the alteration of inflammatory responses in different diseases.

Regulatory B Cells in Autoimmune Diabetes

Since they were discovered almost three decades ago, a subset of B cells denoted as regulatory B cells (Bregs) have elicited interest throughout the immunology community. Many investigators have sought to characterize their phenotype and to understand their function and immunosuppressive mechanisms. Indeed, studies in murine models have demonstrated that Bregs possess varied phenotypic markers and could be classified into different subsets whose action and pivotal role depend on the pathological condition or stimuli. Similar conclusions were drawn in clinical settings delineating an analogous Breg population phenotypically resembling the murine Bregs that ultimately may be associated with a state of tolerance. Recent studies suggested that Bregs may play a role in the onset of autoimmune diabetes. This review will focus on deciphering the different subclasses of Bregs, their emerging role in autoimmune diabetes, and their potential use as a cell-based therapeutic.

Targeting immunosuppressor cells with nanoparticles in autoimmunity: How far have we come to?

Autoimmunity is the assault of immune response towards self-antigens, resulting to inflammation and tissue injury. It is staged into three phases and caused by malfunction of immune tolerance. In our body, immune tolerance is synchronized by several immunosuppressor cells such as regulatory T cells and B cells as well as myeloid-derived suppressor cells, which are prominently dysregulated in autoimmunity. Hence, targeting these cell populations serve as a significant potential in the therapy of autoimmunity. Nanotechnology with its advantageous properties is shown to be a remarkable tool as drug delivery system in this field. This review focused on the development of therapeutics in autoimmune diseases utilizing various nanoparticles formulation based on two targeting approaches in autoimmunity, passive and active targeting. Lastly, this review outlined the approved present nanomedicines as well as in clinical evaluations and issues regarding the lack of translation of these nanomedicines into the market, despite the abundant of positive experimental observations.

Regulatory B Cells (Bregs) Inhibit Osteoclastogenesis and Play a Potential Role in Ameliorating Ovariectomy-Induced Bone Loss

Increasing evidence in recent years has suggested that regulatory B cells (Bregs) are one of the crucial modulators in various inflammatory disease conditions. However, no study to date has investigated the significance of Bregs in modulating osteoclastogenesis. To the best of our knowledge, in the present study, we for the first time examined the anti-osteoclastogenic potential of Bregs under in vitro conditions and observed that Bregs suppress RANKL-induced osteoclastogenesis in a dose-dependent manner. We further elucidated the mechanism behind the observed suppression of osteoclasts differentiation via Bregs. Our results clearly suggested that the observed anti-osteoclastogenic property of Bregs is mediated via the production of IL-10 cytokine. Next, we explored whether Bregs have any role in mediating inflammatory bone loss under post-menopausal osteoporotic conditions in ovx mice. Remarkably, our in vivo data clearly suggest that the frequencies of both CD19+IL-10+ Bregs and CD19+CD1dhiCD5+IL-10+ "B10" Bregs were significantly reduced in case of osteoporotic mice model. Moreover, we also found a significant reduction in serum IL-10 cytokine levels in osteoporotic mice, thereby further supporting our observations. Taken together, the present study for the first time establishes the direct role of regulatory B cells in modulating osteoclastogenesis in vitro. Further, our in vivo data suggest that modulations in the percentage of Bregs population along with its reduced potential to produce IL-10 might further exacerbate the observed bone loss in ovx mice.

The Multiple Roles of B Cells in the Pathogenesis of Sjögren's Syndrome

Primary Sjögren’s syndrome (pSS) is a chronic autoimmune disease characterized by lymphocytic infiltration and tissue destruction of exocrine glands such as salivary glands. Although the formation of ectopic lymphoid tissue in exocrine glands and overproduction of autoantibodies by autoreactive B cells highlight the critical involvement of B cells in disease development, the precise roles of various B cell subsets in pSS pathogenesis remain partially understood. Current studies have identified several novel B cell subsets with multiple functions in pSS, among which autoreactive age-associated B cells, and plasma cells with augmented autoantibody production contribute to the disease progression. In addition, tissue-resident Fc Receptor-Like 4 (FcRL4)⁺ B cell subset with enhanced pro-inflammatory cytokine production serves as a key driver in pSS patients with mucosa-associated lymphoid tissue (MALT)-lymphomas. Recently, regulatory B (Breg) cells with impaired immunosuppressive functions are found negatively correlated with T follicular helper (Tfh) cells in pSS patients. Further studies have revealed a pivotal role of Breg cells in constraining Tfh response in autoimmune pathogenesis. This review provides an overview of recent advances in the identification of pathogenic B cell subsets and Breg cells, as well as new development of B-cell targeted therapies in pSS patients.

B10 cells decrease fibrosis progression following cardiac injury partially by IL-10 production and regulating hyaluronan secretion

B10 cells play negative roles in inflammatory disorders by producing IL-10. However, their effects on fibrosis have not been elucidated. Therefore, this study was conducted to examine the dynamic changes of B10 cell frequency and their potential role in cardiac fibrosis. We found that the frequency of B10 cells was significantly increased, and they participated in the regression of fibrosis via IL-10, particularly by accelerating hyaluronan secretion and inhibiting collagen deposition. In vivo, hyaluronan ablation or treatment significantly restricted cardiac fibrosis development. hyaluronan-induced conversion of M1/M2 Mc was dependent on the size of hyaluronan. Low molecular weight hyaluronan promoted the conversion to M1 Mϕ, whereas medium and high molecular weight hyaluronan accelerated Mϕ transdifferentiation into the M2 phenotype. Adoptive transfer of B10 cells significantly attenuated collagen deposition whereas CD19^-/- mice with reduced B10 cells exacerbated fibrosis following cardiac injury. Our results provide new evidence suggesting that B10 cells exert antifibrotic effects by regulating the extracellular matrix composition during cardiac injury, and also highlight that B10 cells may serve as a promising therapeutic candidate for managing cardiac fibrosis-associated disorders.

Immunosuppressive Mechanisms of Regulatory B Cells

Regulatory B cells (Bregs) is a term that encompasses all B cells that act to suppress immune responses. Bregs contribute to the maintenance of tolerance, limiting ongoing immune responses and reestablishing immune homeostasis. The important role of Bregs in restraining the pathology associated with exacerbated inflammatory responses in autoimmunity and graft rejection has been consistently demonstrated, while more recent studies have suggested a role for this population in other immune-related conditions, such as infections, allergy, cancer, and chronic metabolic diseases. Initial studies identified IL-10 as the hallmark of Breg function; nevertheless, the past decade has seen the discovery of other molecules utilized by human and murine B cells to regulate immune responses. This new arsenal includes other anti-inflammatory cytokines such IL-35 and TGF-β, as well as cell surface proteins like CD1d and PD-L1. In this review, we examine the main suppressive mechanisms employed by these novel Breg populations. We also discuss recent evidence that helps to unravel previously unknown aspects of the phenotype, development, activation, and function of IL-10-producing Bregs, incorporating an overview on those questions that remain obscure.

Regulatory and IgE+ B Cells in Allergic Asthma

Allergic asthma is triggered by inhalation of environmental allergens resulting in bronchial constriction and inflammation, which leads to clinical symptoms such as wheezing, coughing, and difficulty breathing. Asthmatic airway inflammation is initiated by inflammatory mediators released by granulocytic cells. However, the immunoglobulin E (IgE) antibody is necessary for the initiation of the allergic cascade, and IgE is produced and released exclusively by memory B cells and plasma cells. Acute allergen exposure has also been shown to increase IgE levels in the airways of patients diagnosed with allergic asthma; however, more studies are needed to understand local airway inflammation. Additionally, regulatory B cells (B_regs) have been shown to modulate IgE-mediated inflammatory processes in allergic asthma pathogenesis, particularly in mouse models of allergic airway disease. However, the levels and function of these IgE⁺ B cells and B_regs remain to be elucidated in human models of asthma. The overall objective for this chapter is to provide detailed methodological, and insightful technological advances to study the biology of B cells in allergic asthma pathogenesis. Specifically, we will describe how to investigate the frequency and function of IgE⁺ B cells and B_regs in allergic asthma, and the kinetics of these cells after allergen exposure in a human asthma model.

The double-edged sword of Tregs in M tuberculosis, M avium, and M absessus infection

Immunity against different Mycobacteria species targeting the lung requires distinctly different pulmonary immune responses for bacterial clearance. Many parameters of acquired and regulatory immune responses differ quantitatively and qualitatively from immunity during infection with Mycobacteria species. Nontuberculosis Mycobacteria species (NTM) Mycobacterium avium- (M avium), Mycobacterium abscessus-(M abscessus), and the Mycobacteria species Mycobacterium tuberculosis-(Mtb). Herein, we discuss the potential implications of acquired and regulatory immune responses in the context of animal and human studies, as well as future directions for efforts to treat Mycobacteria diseases.

Artemisinin attenuates IgM xenoantibody production via inhibition of T cell-independent marginal zone B cell proliferation

Artemisinin (ART) has been shown to suppress B cell activation and plasma cell formation. However, its effect on splenic marginal zone (MZ) B cells is unknown. Splenic MZ B cells play a critical role in rapidly induced Ab production against blood-borne foreign Ags. Dysfunction of MZ B cells, due to inhibition of its proliferation or displacement of its homing, results in an attenuated adaptive humoral response. Here, we investigate the effect of ART on splenic MZ B (CD19+ CD21high CD23low ) and B10 (CD19+ CD1dhigh CD5+ ) B cells to explore the mechanisms of ART-induced immunosuppression in T cell-deficient nude mice challenged with hamster xenoantigens. In this study, we demonstrate that ART decreases T cell-independent xenogeneic IgM Ab production and, this is associated with a strong suppression of MZ B cell proliferation and a relative increase of CD21low CD23+ follicular and B10 B cells. In addition, this suppression impairs IL-10 production. Taken together, our data indicate that ART suppresses B cell immune responses through a distinctive effect on splenic MZ B and other B cells. This represents a new mechanism of ART-induced immunosuppression.

Suppression of IL-23-mediated psoriasis-like inflammation by regulatory B cells

Psoriasis is an inflammatory cutaneous disease mediated by T-cell dependent immune responses; however, B cells are also considered to play an important role its development. Regulatory B cells (Bregs) regulate immune responses negatively through interleukin-10 (IL-10) production. This study aimed to investigate the role of Bregs in IL-23-mediated psoriasis-like inflammation in mice. Psoriasis-like inflammation was induced in B cell-specific phosphatase and tensin homolog (PTEN)-deficient mice, in which Bregs were significantly expanded, and in their controls, by intradermal injection of 20 μL phosphate-buffered saline (PBS) containing 0.5 μg rmIL-23 into one ear, every other day for 16 days. IL-23-mediated psoriasis-like inflammation was suppressed in B cell-specific PTEN-deficient mice along with decreased ear thickness and epidermal thickness on day 15. Moreover, adoptive transfer of B1 B cells suppressed IL-23-mediated psoriasis-like inflammation. rmIL-23-injected B cell-specific PTEN-deficient mice showed expanded regulatory T cells (Tregs) in the spleen and draining lymph nodes along with increased Bregs. Further, T helper (Th) 17 differentiation in the rmIL-23-injected ear was suppressed in B cell-specific PTEN-deficient mice. Overall, these results indicate that increased Bregs suppress IL-23-mediated psoriasis-like inflammation through Treg expansion and inhibition of Th17 differentiation. Thus, targeting Bregs may be a feasible treatment strategy for psoriasis.

Regulatory B cells in respiratory health and diseases

B cells are critical mediators of humoral immune responses in the airways through antibody production, antigen presentation, and cytokine secretion. In addition, a subset of B cells, known as regulatory B cells (Bregs), exhibit immunosuppressive functions via diverse regulatory mechanisms. Bregs modulate immune responses via the secretion of IL‐10, IL‐35, and tumor growth factor‐β (TGF‐β), and by direct cell contact. The balance between effector and regulatory B cell functions is critical in the maintenance of immune homeostasis. The importance of Bregs in airway immune responses is emphasized by the different respiratory disorders associated with abnormalities in Breg numbers and function. In this review, we summarize the role of immunosuppressive Bregs in airway inflammatory diseases and highlight the importance of this subset in the maintenance of respiratory health. We propose that improved understanding of signals in the lung microenvironment that drive Breg differentiation can provide novel therapeutic avenues for improved management of respiratory diseases.

Increased risk of inflammatory bowel disease among patients treated with rituximab in Iceland from 2001 to 2018

OBJECTIVE

Immune-mediated diseases are on the rise after the introduction of powerful immunomodulating drugs. The objective of this study was to determine the population-based incidence rate of inflammatory bowel disease (IBD) among patients treated with the monoclonal antibody rituximab in Iceland and compare it to the baseline incidence rate of IBD in the general population.

METHODS

We identified all patients treated with rituximab in Iceland from 2001 to 2018 through a central medicine database. IBD cases were indexed from medical records and ICD-10 codes and further confirmed by colonoscopy- and pathology reports. An experienced pathologist compared the pathology of IBD cases with matched controls of IBD patients.

RESULTS

Lymphomas and related neoplasms were the most frequent indication for treatment with rituximab (n = 367) among the 651 patients included in the analysis. Following treatment, seven patients developed IBD: two cases of Crohn's disease, three with ulcerative colitis, and two with indeterminate IBD. The incidence rate of IBD among rituximab treated patients was 202 cases per 100,000 person-years. Comparing our data to IBD incidence in Iceland, rituximab treated patients have an age-adjusted hazard ratio of 6.6 for developing IBD. The risk did not correlate with dose or treatment duration. Prior diagnosis of an autoimmune illness did not increase the risk of IBD in rituximab treated patients.

CONCLUSIONS

Patients on rituximab have a sixfold increased risk of developing IBD compared to the general population. This risk was not affected by the indication for treatment and was not associated with concurrent immune-mediated diseases. Summary This population-based retrospective cohort study included all patients receiving treatment with rituximab between 2001 and 2018 in Iceland and identified a sixfold increased risk of developing IBD when compared to the general population.

B regulatory cells in allergy

B cells have classically been recognized for their unique and indispensable role in the production of antibodies. Their potential as immunoregulatory cells with anti-inflammatory functions has received increasing attention during the last two decades. Herein, we highlight pioneering studies in the field of regulatory B cell (Breg) research. We will review the literature on Bregs with a particular focus on their role in the regulation of allergic inflammation.

Assessing the expression of immunosuppressive cytokines in the newly diagnosed systemic lupus Erythematosus patients: a focus on B cells

BACKGROUND

The immunosuppressive effects of regulatory B-cells (Bregs) and their immunosuppressive cytokines on immune responses in autoimmune disorders, mainly systemic lupus erythematosus (SLE), have been recently established. Therefore, the purpose of this article has been the exploration of the expressions of cytokines produced by B cells in newly diagnosed SLE patients.

RESULTS

The findings demonstrated that the gene expression of IL-10, TGF-β, IL-35, PD-L1, and FasL was significantly up-regulated in SLE patients compared to healthy subjects (P < 0.05). Additionally, the results revealed that serum levels of IL-10, TGF-β, IL-35, PD-L1 were remarkably increased in patients with SLE compared to healthy subjects (P < 0.0001). However, serum levels of IL-10 and TGF-β decreased significantly with increasing SLEDAI score in studied patients (P < 0.05).

CONCLUSION

It was concluded that the release of anti-inflammatory cytokines, particularly IL-10 and TGF-β, might inhibit immune responses and autoreactive immune cells in a compensatory manner in SLE patients with mild to moderate disease activity.