Altered frequencies of memory B cells in new-onset systemic lupus erythematosus patients

Association between peripheral activated naive and double negative 2 B-cell subsets and clinical parameters in lupus nephritis patients

Altered composition of B-cell compartments is a known feature in patients with systemic lupus erythematosus (SLE). However, deep characterisation of B-cell subsets and their relation to clinical manifestations and disease activity in patients is limited. In this study, we analysed peripheral B-cell subsets phenotype in SLE (n = 35) and healthy controls (HCs, n = 15) by spectral flow cytometry. Disease activity was stratified as inactive (SLEDAI-2 K score 0, n = 2), mild (SLEDAI-2 K score 1-5, n = 12), moderate (SLEDAI-2 K score 6-10, n = 6) or high (SLEDAI-2 K > 10, n = 15). An elevated proportion of activated naive (aNAV), double negative 2 (DN2) and plasmablasts (PB) was observed in patients with high disease activity, compared to other groups of patients and HCs. An upregulation of BTLA was found on both aNAV and DN2 and shifted to lower levels with increasing disease activity. In lupus nephritis (LN) patients (n = 21), aNAV B-cells were especially expanded and positively correlated with DN2 (r = 0.5, p = 0.019) and PB (r = 0.43, p = 0.048). Also, correlation was observed between DN2 and PB (r = 0.6, p = 0.003). Moreover, aNAV frequencies positively correlated with SLEDAI-2 K score, and negatively with the complement fractions C3 and C4. Further, aNAV, DN2 and PB were more expanded in association with positive anti-dsDNA antibodies, rather than other antibody specificities (anti-Sm). These data suggest roles of extrafollicular B cells as key players in disease development of LN. Their association with presence of anti-dsDNA antibodies may indicate their value as candidate biomarkers of kidney involvement in SLE.

Serum level of IFN-λ is elevated in idiopathic inflammatory myopathies

BACKGROUND

Idiopathic inflammatory myopathies (IIM) are a heterogeneous group of autoimmune disorders with uncertain pathogenesis. Interferon (IFN)-λ has recently been described as an important mediator of immune responses. The main purpose of this study is to find out whether IFN-λ is involved in IIM.

METHODS

The published RNA-seq data of dermatomyositis (DM) muscle and IIM double negative (DN) B cells were analyzed. Serum IFN-λ1, IFN-λ2, and IFN-λ3 levels of 59 IIM patients and 29 healthy persons were determined by enzyme-linked immunosorbent assay (ELISA). The proportion of DN B cells and subsets as well as phosphorylated STAT1 (p-STAT1) levels in peripheral B cells was measured by flow cytometry. Ex vivo induction of double negative 2 (DN2) B cells were performed for validation.

RESULTS

Type III IFN signaling pathway was enriched in muscle tissue from DM patients. Serum IFN-λ1, IFN-λ2, and IFN-λ3 levels were significantly higher in the IIM patients, especially patients with interstitial lung disease (ILD) and skin manifestations. Moreover, serum IFN-λ1 level was positively correlated with the disease activity. In addition, IIM patients with positive anti-melanoma differentiation-associated gene 5 (anti-MDA5) antibodies exhibited higher serum IFN-λ1, IFN-λ2, and IFN-λ3 levels. The frequency of DN2 B cells were elevated in IIM patients' blood. Interestingly, the type III IFN signaling pathway was enriched in circulating DN2 B cells from IIM patients, which could induce T-bet+CD19hi DN2 B cell differentiation ex vivo.

CONCLUSION

IFN-λ may participate in the pathogenesis of IIM by acting on DN2 B cells and serve as a disease biomarker for IIM patients. Key Points • Type III IFN signaling pathway is enriched in the involved muscles of DM patients. • Serum IFN-λ in IIM patients is correlated with disease activity and is higher in patients with ILD, skin lesions, and positive anti-MDA5 antibodies. • DN2 B cells with enriched type III IFN signaling pathway are accumulated in the peripheral blood of IIM patients.

TLR10 expression in unswitched memory B associates with the disease activity of patients with systemic lupus erythematosus

OBJECTIVE

Systemic lupus erythematosus (SLE) is characterized by impaired B-cell function and a distinct B-cell phenotype. Toll-like receptor (TLR) 10 is highly expressed in human B cells and can regulate B-cell activation. Here, we examined the variations in TLR10 expression across B-cell subpopulations and its impact on the disease activity in SLE patients.

METHODS

Thirty-one patients with stable SLE, 30 patients with active SLE, and 28 healthy controls (HCs) were recruited. Flow cytometry was performed to assess the prevalence of B-cell subpopulations and their TLR10 expression. The diagnostic value of unswitched memory B cells (UMB) and double-negative B cells (DNB) in relation to disease activity was determined. The correlations between TLR10 expressions in B-cell subpopulations and disease activity were further evaluated, respectively.

RESULTS

Compared with the HCs, the stable patients exhibited significantly reduced Naive B proportion and elevated switched memory B and DNB proportion, while active patients presented markedly decreased UMB and increased DNB proportion. Furthermore, the receiver operating characteristics analysis revealed that UMB was more reliable than DNB in diagnosing SLE disease activity. Among the B-cell subsets, only the TLR10 expression in UMB was notably diminished in SLE patients, particularly in active patients. Importantly, TLR10 expression in UMB was negatively correlated with the disease activity.

CONCLUSION

UMB could serve as a promising biomarker for SLE disease activity, and the TLR10 expression in UMB was negatively correlated with the activity of SLE patients, suggesting that TLR10 might be involved in the disease progression of SLE by regulating the UMB function. Key Points • Active SLE patients exhibited reduced unswitched memory B cells and increased double-negative B cell proportions in blood. • Unswitched memory B cells are better predictors of disease activity in SLE than double-negative B cells. • TLR10 expression in unswitched memory B cells is markedly diminished in SLE patients. • TLR10 expression in unswitched memory B cells is negatively associated with SLE disease activity.

B cell subsets-related biomarkers and molecular pathways for systemic lupus erythematosus by transcriptomics analyses

BACKGROUND

Systemic lupus erythematosus (SLE), an autoimmune disease, is characterised by B-cell abnormalities and a loss of tolerance that can produce autoantibody. However, the imperative genes and molecular pathways involved in the change of B cell populations remain unclear.

METHODS

The expression of B cell subsets between SLE and healthy controls (HCs) was detected based on micro-array transcriptome data. The Weighted Gene Co-Expression Network Analysis (WGCNA) further revealed the co-expression modules of naïve and memory B cells. Whereafter, we performed the functional enrichment analysis, Protein-protein interaction (PPI) networks construction and feature selection to screen hub genes. Ultimately, we recruited SLE patients and HCs from the Second Hospital of Shanxi Medical University and further verified these genes in transcriptome sequencing samples.

RESULTS

Total of 1087 SLE patients and 86 HCs constituted in the study. Compared to HCs, the levels of peripheral naïve B cells of SLE patients decreased, while memory B cells increased. WGCNA identified two modules with the highest correlation for the subsequent analysis. The purple module was primarily in connection with naïve B cells, and the GO analysis indicated that these genes were mainly abundant in B cell activation. The blue module relevant to memory B cells was most significantly enriched in the "defence response to virus" correlation pathway. Then we screened six hub genes by PPI and feature selection. Finally, four biomarkers (IFI27, IFITM1, MX2, IRF7) were identified by transcriptome sequencing verification.

CONCLUSION

Our study identified hub genes and key pathways associated with the naïve and memory B cells respectively, which may offer novel insights into the behaviours of B cells and the pathogenesis of SLE.

Genetics of SLE: mechanistic insights from monogenic disease and disease-associated variants

The past few years have provided important insights into the genetic architecture of systemic autoimmunity through aggregation of findings from genome-wide association studies (GWAS) and whole-exome or whole-genome sequencing studies. In the prototypic systemic autoimmune disease systemic lupus erythematosus (SLE), monogenic disease accounts for a small fraction of cases but has been instrumental in the elucidation of disease mechanisms. Defects in the clearance or digestion of extracellular or intracellular DNA or RNA lead to increased sensing of nucleic acids, which can break B cell tolerance and induce the production of type I interferons leading to tissue damage. Current data suggest that multiple GWAS SLE risk alleles act in concert with rare functional variants to promote SLE development. Moreover, introduction of orthologous variant alleles into mice has revealed that pathogenic X-linked dominant and recessive SLE can be caused by novel variants in TLR7 and SAT1, respectively. Such bespoke models of disease help to unravel pathogenic pathways and can be used to test targeted therapies. Cell type-specific expression data revealed that most GWAS SLE risk genes are highly expressed in age-associated B cells (ABCs), which supports the view that ABCs produce lupus autoantibodies and contribute to end-organ damage by persisting in inflamed tissues, including the kidneys. ABCs have thus emerged as key targets of promising precision therapeutics.

EZH2 inhibition dampens autoantibody production in lupus by restoring B cell immune tolerance

OBJECTIVE

The aim of this study was to elucidate the role of enhancer of zeste homolog 2 (EZH2) in the breakdown of B cell immune tolerance and production of autoantibodies in systemic lupus erythematosus (SLE), and to explore the therapeutic effects of EZH2 inhibition on lupus.

METHODS

Peripheral blood mononuclear cells (PBMCs) were collected from new-onset SLE patients for flow cytometric analysis. Pristane-induced lupus mice were constructed, and the EZH2 inhibitor was administrated by intraperitoneal injection to treat lupus mice. Blood and urine were collected from lupus mice to detect autoantibodies and proteinuria, and renal pathology scores were assessed. Mouse spleen B cells were sorted with magnetic beads and subjected to flow cytometric apoptosis detection, real time quantitative PCR (RT-qPCR), and western blotting (WB).

RESULTS

EZH2 expression was elevated in diverse B-cell subsets in both SLE patients and pristane-induced lupus mice. The EZH2 inhibitor attenuated lupus-like symptoms and dampened autoantibody production in pristane-induced lupus mice. Inhibition of EZH2 also reduced autoantibody secretion by plasma cells from lupus patients. Mechanistically, EZH2 mediated the impaired apoptosis of autoreactive B cells and the differentiation of autoantibody producing plasma cells by inhibiting multiple cyclin-dependent kinase inhibitor (CKI) genes.

CONCLUSION

EZH2 mediated the breakdown of B-cell peripheral immune tolerance by inhibiting CKI genes and participated in the generation of autoantibodies in SLE. EZH2 inhibition could serve as a promising drug intervention for the treatment of SLE.

The rapid inhibition of B-cell activation markers by belimumab was associated with disease control in systemic lupus erythematosus patients

Objective: To examine the kinetics of B cell subsets and activation markers in the early stage of belimumab treatment and their correction with treatment response. Methods: We enrolled 27 systemic lupus erythematosus (SLE) patients receiving 6 months belimumab treatment. Flow cytometry was used to test their B cell subsets and activation markers (including CD40, CD80, CD95, CD21^low, CD22, p-SYK and p-AKT). Results: During belimumab treatment, SLEDAI-2K declined, the proportions of CD19⁺ B cells and naïve B cells decreased, whereas the switched memory B cells and non-switched B cells increased. The larger variations of the B cell subsets and the activation markers were in the first 1 month than the other later time frames. The ratio of p-SYK/p-AKT on non-switched B cell at 1 month was associated with the SLEDAI-2K decline rate in the 6 months of belimumab treatment. Conclusion: B cell hyperactivity was rapidly inhibited in the early stage of belimumab treatment, and the ratio of p-SYK/p-AKT may predict SLEDAI-2K decline. Clinical Trial Registration: https://www.clinicaltrials.gov/ct2/show/NCT04893161?term=NCT04893161&draw=2&rank=1; identifier: NCT04893161.

Autoantibodies in COVID-19 correlate with antiviral humoral responses and distinct immune signatures

BACKGROUND

Several autoimmune features occur during coronavirus disease 2019 (COVID-19), with possible implications for disease course, immunity, and autoimmune pathology. In this study, we longitudinally screened for clinically relevant systemic autoantibodies to assess their prevalence, temporal trajectory, and association with immunity, comorbidities, and severity of COVID-19.

METHODS

We performed highly sensitive indirect immunofluorescence assays to detect antinuclear antibodies (ANA) and antineutrophil cytoplasmic antibodies (ANCA), along with serum proteomics and virome-wide serological profiling in a multicentric cohort of 175 COVID-19 patients followed up to 1 year after infection, eleven vaccinated individuals, and 41 unexposed controls.

RESULTS

Compared with healthy controls, similar prevalence and patterns of ANA were present in patients during acute COVID-19 and recovery. However, the paired analysis revealed a subgroup of patients with transient presence of certain ANA patterns during acute COVID-19. Furthermore, patients with severe COVID-19 exhibited a high prevalence of ANCA during acute disease. These autoantibodies were quantitatively associated with higher SARS-CoV-2-specific antibody titers in COVID-19 patients and in vaccinated individuals, thus linking autoantibody production to increased antigen-specific humoral responses. Notably, the qualitative breadth of antibodies cross-reactive with other coronaviruses was comparable in ANA-positive and ANA-negative individuals during acute COVID-19. In autoantibody-positive patients, multiparametric characterization demonstrated an inflammatory signature during acute COVID-19 and alterations of the B-cell compartment after recovery.

CONCLUSION

Highly sensitive indirect immunofluorescence assays revealed transient autoantibody production during acute SARS-CoV-2 infection, while the presence of autoantibodies in COVID-19 patients correlated with increased antiviral humoral immune responses and inflammatory immune signatures.

Antigen-experienced CXCR5- CD19low B cells are plasmablast precursors expanded in SLE

OBJECTIVES

Altered composition of the B cell compartment in the pathogenesis of systemic lupus erythematosus (SLE) is characterized by expanded plasmablast (PB) and IgD^- CD27^- double negative (DN) B cell populations. Previous studies showed that DN B cells represent a heterogeneous subset and further characterization is needed.

METHODS

Therefore, we analyzed two independent cohorts of healthy donors and SLE patients using a combined approach of flow (HD: n=16; SLE: n=28,) and mass cytometry (HD: n=18; SLE: n=24) and targeted RNA sequencing. To study B cell subsets formation in acute immune response versus autoimmunity we investigated HDs at various time points upon vaccination with BNT162b2 or during acute COVID-19 infection using flow cytometry.

RESULTS

We have found that IgD^- CD27⁺ switched and atypical IgD^- CD27^- memory B cells, which are increased in SLE, represent heterogeneous populations composed of three different subsets each. Populations of CXCR5⁺ CD19^int , CXCR5^- CD19^high and CXCR5^- CD19^low are found in both compartments suggesting their relationship. We characterize a hitherto unknown and antigen-experienced CXCR5^- CD19^low subset enhanced in SLE carrying a PB phenotype with diminished B cell receptor responsiveness and expression of CD38, CD95, CD71, PRDM1, XBP-1, and IRF4. CXCR5^- CD19^low subsets are increased and correlate with PB frequencies in SLE and upon BNT162b2-vaccination of HD suggesting their interrelationship and contribution to plasmacytosis. The demonstration of CXCR5^- CD19^low B cells amongst both CD27+ and CD27- cells questions the role of CD27 as reliable marker for B cell differentiation.

CONCLUSION

Our data suggest that CXCR5^- CD19^low B cells are precursors of plasmablasts, thus co-targeting this subset may have therapeutic value in SLE.

Molecular Mechanisms of Immunosenescene and Inflammaging: Relevance to the Immunopathogenesis and Treatment of Multiple Sclerosis

Aging is characterized, amongst other features, by a complex process of cellular senescence involving both innate and adaptive immunity, called immunosenescence and associated to inflammaging, a low-grade chronic inflammation. Both processes fuel each other and partially explain increasing incidence of cancers, infections, age-related autoimmunity, and vascular disease as well as a reduced response to vaccination. Multiple sclerosis (MS) is a lifelong disease, for which considerable progress in disease-modifying therapies (DMTs) and management has improved long-term survival. However, disability progression, increasing with age and disease duration, remains. Neurologists are now involved in caring for elderly MS patients, with increasing comorbidities. Aging of the immune system therefore has relevant implications for MS pathogenesis, response to DMTs and the risks mediated by these treatments. We propose to review current evidence regarding markers and molecular mechanisms of immunosenescence and their relevance to understanding MS pathogenesis. We will focus on age-related changes in the innate and adaptive immune system in MS and other auto-immune diseases, such as systemic lupus erythematosus and rheumatoid arthritis. The consequences of these immune changes on MS pathology, in interaction with the intrinsic aging process of central nervous system resident cells will be discussed. Finally, the impact of immunosenescence on disease evolution and on the safety and efficacy of current DMTs will be presented.

Contributions of Immune Cells and Stromal Cells to the Pathogenesis of Systemic Sclerosis: Recent Insights

Systemic sclerosis (SSc) is a multisystem rheumatic disease characterized by vascular dysfunction, autoimmune abnormalities, and progressive organ fibrosis. A series of studies in SSc patients and fibrotic models suggest that immune cells, fibroblasts, and endothelial cells participate in inflammation and aberrant tissue repair. Furthermore, the growing number of studies on single-cell RNA sequencing (scRNA-seq) technology in SSc elaborate on the transcriptomics and heterogeneities of these cell subsets significantly. In this review, we summarize the current knowledge regarding immune cells and stromal cells in SSc patients and discuss their potential roles in SSc pathogenesis, focusing on recent advances in the new subtypes by scRNA-seq.

Proportion of B cell subsets and Nrf2 mediated redox regulation in systemic lupus erythematosus patients

Systemic lupus erythematosus (SLE) is characterized by expansion of autoreactive lymphocytes and impaired management of oxidative stress. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) plays a significant role in maintaining the redox homeostasis of cell. The present study aims to investigate the frequency of peripheral B cell subsets and the redox regulation by Nrf2 in SLE patients with variable disease activity. For this, a total of forty (40) SLE patients and twenty (20) age and gender-matched healthy controls (HCs) were recruited where patients with SLEDAI < 6 were grouped as Inactive SLE (n = 20) and patients with SLEDAI ≥ 6 were grouped as Active SLE (n = 20). A proportion of peripheral B cell subsets, level of ROS and expression of Nrf2 and Keap1 were studied with the help of flow cytometry and multiplex cytokine bead assay was exploited to estimate the serological concentration of cytokines. The frequency of B cell subsets was significantly altered and correlated with SLEDAI score. Concentration of IFNα2, IFN-β, BAFF, APRIL and IL-6 was also raised in active SLE patients. Moreover, the level of cytosolic ROS was universally decreased while mitochondrial ROS was increased in B cell subsets. The expression of Nrf2 and Keap1 (a negative regulator of Nrf2) was significantly increased in B cell subsets of SLE patients. Here, it has been demonstrated that the frequency of peripheral B cell subsets varies with modification in the SLE disease activity. The given data also demonstrated that the expression of Nrf2 is significantly heightened in B cell subsets to deal with free radical stress.

Small RNAs encoded by human endogenous retrovirus K overexpressed in PBMCs may contribute to the diagnosis and evaluation of systemic lupus erythematosus as novel biomarkers

This study aimed to identify the genes and small RNAs (sRNAs) expressed by the human endogenous retrovirus K (HERV-K) HML2 and their associations with the immune process of systemic lupus erythematosus (SLE). RNA-Seq data including 99 SLE patients and 18 controls (GSE72420) was obtained from the Gene Expression Omnibus. Differentially expressed genes (DEGs) as well as HML2-DEGs between SLE patients and normal controls were identified. Five HML2-DEGs involved in immune-regulating function were identified using weighted gene co-expression network analysis (WGCNA). The associations between these genes and the proportions of immune cells were determined by CIBERSORT. Ten candidate HML2-encoded sRNAs were identified based on specific criteria, and three of them were further validated in SLE patients by qRT-PCR. The diagnostic values of these three sRNAs were evaluated in SLE and lupus nephritis (LN). This study suggested that HML2 genes and their encoded sRNAs might be involved in the immune regulation and progress of SLE. These potential sRNAs might function as regulatory molecules and diagnostic biomarkers of SLE and LN.

Double-negative (DN) B cells: an under-recognized effector memory B cell subset in autoimmunity

Human B cells could be divided into four classical subsets based on CD27 and immunoglobulin (Ig)D expression. Distinct from the other three well-studied subsets, CD27^- IgD^- B cells, also termed as double-negative (DN) B cells, have long been neglected. However, in recent years emerging evidence shows that DN B cells are unique memory B cells with important functions. They are expanded in a variety of diseases, especially in autoimmune diseases, contributing to the disease pathogenesis. Here, we briefly review the studies on DN B cells, including their origins, characteristics, subsets and roles in diseases, to try to bring new insights into this under-recognized B cell subset.

Human marginal zone B cell development from early T2 progenitors

B cells emerge from the bone marrow as transitional (TS) B cells that differentiate through T1, T2, and T3 stages to become naive B cells. We have identified a bifurcation of human B cell maturation from the T1 stage forming IgMhi and IgMlo developmental trajectories. IgMhi T2 cells have higher expression of α4β7 integrin and lower expression of IL-4 receptor (IL4R) compared with the IgMlo branch and are selectively recruited into gut-associated lymphoid tissue. IgMhi T2 cells also share transcriptomic features with marginal zone B cells (MZBs). Lineage progression from T1 cells to MZBs via an IgMhi trajectory is identified by pseudotime analysis of scRNA-sequencing data. Reduced frequency of IgMhi gut-homing T2 cells is observed in severe SLE and is associated with reduction of MZBs and their putative IgMhi precursors. The collapse of the gut-associated MZB maturational axis in severe SLE affirms its existence in health.

Utility of lymphocyte phenotype profile to differentiate primary Sjögren syndrome from Sicca syndrome

BACKGROUND

blood B cell profile has been proposed to have diagnostic utility in primary Sjögren syndrome (pSS), but the potential utility of advanced lymphocyte profiling to differentiate between pSS and Sicca syndrome has not been fully investigated.

METHODS

distribution of peripheral lymphocyte subpopulations was analysed by flow cytometry in 68 patients with pSS, 26 patients with Sicca syndrome and 23 healthy controls. The ability to discriminate between pSS and Sicca syndrome was analysed using the area under the curve (AUC) of the receiver operating characteristic curve of the different lymphocyte subsets.

RESULTS

the ratio between naïve/memory B cell proportions showed an AUC of 0.742 to differentiate pSS and Sicca syndrome, with a sensitivity of 76.6% and a specificity of 72% for a cut-off value of 3.4. The ratio of non-switched memory B cells to activated CD4+ T cells percentage (BNSM/CD4ACT) presented the highest AUC (0.840) with a sensitivity of 83.3% and specificity of 81.7% for a cut-off value < 4.1. To differentiate seronegative pSS patients from Sicca patients the BNSM/CD4ACT ratio exhibited an AUC of 0.742 (sensitivity 75%, specificity 66.7%, cut-off value < 4.4), and the number of naïve CD4 T cells had an AUC of 0.821 (sensitivity 76.9%, specificity 88.9%, cut-off value < 312/mm3).

CONCLUSION

patients with pSS show a profound imbalance in the distribution of circulating T and B lymphocytes subsets. The ratio BNSM/CD4ACT is useful to discriminate between pSS and Sicca syndrome.

CD52 Is Elevated on B cells of SLE Patients and Regulates B Cell Function

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by B cell dysregulation and breaks in tolerance that lead to the production of pathogenic autoantibodies. We performed single-cell RNA sequencing of B cells from healthy donors and individuals with SLE which revealed upregulated CD52 expression in SLE patients. We further demonstrate that SLE patients exhibit significantly increased levels of B cell surface CD52 expression and plasma soluble CD52, and levels of soluble CD52 positively correlate with measures of lupus disease activity. Using CD52-deficient JeKo-1 cells, we show that cells lacking surface CD52 expression are hyperresponsive to B cell receptor (BCR) signaling, suggesting an inhibitory role for the surface-bound protein. In healthy donor B cells, antigen-specific BCR-activation initiated CD52 cleavage in a phospholipase C dependent manner, significantly reducing cell surface levels. Experiments with recombinant CD52-Fc showed that soluble CD52 inhibits BCR signaling in a manner partially-dependent on Siglec-10. Moreover, incubation of unstimulated B cells with CD52-Fc resulted in the reduction of surface immunoglobulin and CXCR5. Prolonged incubation of B cells with CD52 resulted in the expansion of IgD+IgMlo anergic B cells. In summary, our findings suggest that CD52 functions as a homeostatic protein on B cells, by inhibiting responses to BCR signaling. Further, our data demonstrate that CD52 is cleaved from the B cell surface upon antigen engagement, and can suppress B cell function in an autocrine and paracrine manner. We propose that increased expression of CD52 by B cells in SLE represents a homeostatic mechanism to suppress B cell hyperactivity.

Mechanisms of Dysregulated Humoral and Cellular Immunity by SARS-CoV-2

The current coronavirus disease 2019 (COVID-19) pandemic, a disease caused by severe acute respiratory syndrome corona virus 2 (SARS-CoV-2), was first identified in December 2019 in China, and has led to thousands of mortalities globally each day. While the innate immune response serves as the first line of defense, viral clearance requires activation of adaptive immunity, which employs B and T cells to provide sanitizing immunity. SARS-CoV-2 has a potent arsenal of mechanisms used to counter this adaptive immune response through processes, such as T cells depletion and T cell exhaustion. These phenomena are most often observed in severe SARS-CoV-2 patients, pointing towards a link between T cell function and disease severity. Moreover, neutralizing antibody titers and memory B cell responses may be short lived in many SARS-CoV-2 patients, potentially exposing these patients to re-infection. In this review, we discuss our current understanding of B and T cells immune responses and activity in SARS-CoV-2 pathogenesis.

B Cell Subsets and Cellular Signatures and Disease Relapse in Lupus Nephritis

Introduction

Renal relapses adversely affect the long-term outcomes of patients with lupus nephritis (LN), but the pathogenic mechanisms remain elusive. B cell signatures of miR-148a, BACH1, BACH2, and PAX5 expression are relevant to the regulation of B lymphocyte homeostasis. It is unknown whether B cell signature is related to the relapse of LN.

Methods

We compared B lymphocyte subsets and cellular signatures during disease quiescence between LN patients with multiple relapses (MR, ≥3 LN relapses within 36 months) and those with no relapse (NR). Also, circulating B lymphocytes were isolated from treatment-naïve patients with active LN and treated with antagomir-148a in vitro to investigate the relationship between miR-148a, BACH1, BACH2, and PAX5.

Results

MR patients (n = 19), when compared with NR (n = 14), showed significantly lower percentage of circulating naïve B cells and higher memory B cell-to-naïve B cell ratio. MR patients also showed higher miR-148a levels in sera and B cells, and lower BACH1, BACH2, and PAX5 expression in naïve and memory B cells. Antagomir-148a upregulated BACH1, BACH2, and PAX5 expression, and reduced B cell proliferation upon stimulation, in naïve and memory B cells isolated from treatment-naïve active LN patients.

Conclusion

Altered B cell subsets and cellular signatures of miR-148a, BACH1, BACH2, and PAX5 may be associated with distinct patient phenotypes related to the risk of LN relapse.

Double Negative B Cell Is Associated With Renal Impairment in Systemic Lupus Erythematosus and Acts as a Marker for Nephritis Remission

Objective: Recent studies on double negative B cells (DN B cells) suggested that they have potential pathogenic roles in systemic lupus erythematosus (SLE). This study aimed to determine the circulating DN B cells in SLE patients and analyzed the clinical significance of this cell subset. Methods: Fifty-seven SLE patients and fifty healthy controls (HCs) were recruited in this study. Among the 57 SLE patients, 25 had lupus nephritis (LN). All patients were followed up for 24 weeks. Peripheral B cell subsets were analyzed by flow cytometry. Results: DN B cells were significantly elevated in the SLE patients, especially in the patients with LN (p < 0.01). DN B showed a positive correlation with 24-h urine protein excretion (24 h-UPE) levels (r = 0.444, p = 0.034) in LN patients, and inversely correlated with evaluated glomerular filtration rate (eGFR) (r = -0.351, p = 0.011). DN B cells had a positive correlation with plasma cells (r = 0.484, p < 0.001) and memory B cells (r = 0.703, p < 0.001). After treatment, decreased DN B cells were associated with LN alleviation (p = 0.002). In the follow-up, the remission rate of LN patients with decreased DN B cells was significantly higher than LN patients with increased DN B cells (83.33 vs. 25.00%, p = 0.030) at week 24. Conclusions: This study suggests that the peripheral DN B cells are positively correlated with the severity of renal damage in LN patients and may potentially be used as a prognostic marker in LN.

Alterations in peripheral blood B cells in systemic lupus erythematosus patients with renal insufficiency

OBJECTIVE

Systemic lupus erythematosus (SLE) is one of the autoimmune diseases, believed to be closely related to hyperactivity of B cells, overproduction of autoantibodies and immune complex formation and deposition in affected tissue. The autoreactive inflammation leads to multiorgan damage with kidney dysfunction in the forefront. Studies on lupus nephritis (LN), affecting the majority of SLE patients, are mainly focused on cells causing local inflammation. The aim of our work was to detect alterations in more accessible peripheral blood B cells in the course of SLE focusing on the influence of renal insufficiency (RI) on those parameters.

METHODS

We performed a comprehensive flow cytometry analysis of B cell subpopulations, analyzed gene expression patterns with qPCR, and examined serum cytokine levels with multiplex cytokine/chemokine assay.

RESULTS

We discovered distribution of specific B cell subsets, especially CD38⁺ cells, plasmablasts, associated with the presence and severity of the disease. Changes in expression of MBD2, DNMT1 and APRIL genes were not only associated with activity of SLE but also were significantly changed in patients with RI.

CONCLUSIONS

All these results shed new light on the role of circulating B cells, their subpopulations, function, and activity in the SLE with kidney manifestation.

Increased Non-switched Memory B Cells are Associated with Plasmablasts, Serum IL-6 Levels and Renal Functional Impairments in IgAN Patients

Background: Circulating B cells are crucial for the pathogenesis of IgA nephropathy (IgAN). This study aimed at investigating the relationship between frequency of different subsets of circulating B cells and clinical measures in IgAN patients.Methods: The percentages of different subsets of circulating B cells in 23 IgAN patients and 14 healthy controls (HC) were determined by flow cytometry. Their serum IL-6 levels were measured by Cytometric Bead Array (CBA). Clinical parameters in five patients were measured before and after treatment for 8-12 weeks. The potential relationship between variants was analyzed.Results: In comparison with the HC, the frequency of CD3-CD19+ CD27+ IgD+IgM+ non-switched memory B cells (P = .0038) and CD3-CD19+ CD27hiCD38hi plasmablasts (P = .0467) and serum IL-6 (P = .0392) levels significantly increased in IgAN patients. The percentages of non-switched memory B cells were positively correlated with plasmablasts (R = 0.5781, P = .0039) and serum IL-6 levels (R = 0.6663, P = .0005) in the patients. The percentages of non-switched memory B cells (R = 0.8399, P < .0001), plasmablasts (R = 0.4486, P = .0318) and the levels of serum IL-6 (R = 0.5461, P = .0070) were positively correlated with the values of 24-h urine proteins in IgAN patients. The serum levels of IL-6 were negatively correlated with the eGFR values. Following standard treatment, the frequency of non-switched memory B cells and plasmablasts and the levels of 24-h urine proteins (P = .0317, P = .0079, P < .05) significantly decreased in IgAN patients.Conclusions: Abnormally higher frequency of non-switched memory B cells and plasmablasts may contribute to the pathogenesis of IgAN and be potential biomarkers for IgAN.

Immunomodulatory receptors are differentially expressed in B and T cell subsets relevant to autoimmune disease

Inhibitory cell-surface receptors on lymphocytes, often called immune checkpoints, are powerful targets for cancer therapy. Despite their direct involvement in autoimmune pathology, they are currently not exploited therapeutically for autoimmune diseases. Understanding the expression pattern of these receptors in health and disease is essential for targeted drug design. Here, we designed three 23-colour flow cytometry panels for peripheral-blood T cells, including 15 lineage-defining markers and 21 immunomodulatory cell-surface receptors, and a 22-marker panel for B cells. Blood samples from healthy individuals, multiple sclerosis (MS), and lupus (SLE) patients were included in the study. Several receptors show differential expression on regulatory T cells (Treg) compared to T helper (Th) 1 and Th17 cells, and functional relevance of this difference could be shown for BTLA and CD5. Unbiased multiparametric analysis revealed a subset of activated CD8⁺ T cells and a subset of unswitched memory B cells that are diminished in MS and SLE, respectively.