Interferon (IFN)-λ is a potential mediator in lupus nephritis

Longitudinal analysis at pre- and post-flare of T peripheral helper and T follicular helper subsets in patients with systemic lupus erythematosus

OBJECTIVE

We focused to analyze the time-course changes at pre- and post-flare of T peripheral helper (Tph) cells and circulating T follicular helper (Tfh) cells in the blood of patients with systemic lupus erythematosus (SLE) with lupus low disease activity state (LLDAS) before flare.

METHODS

This study included inactive (n = 29) and active (n = 55) patients with SLE. Tph subsets, Tfh subsets, CD11chi B cells, and plasma cells in the blood were determined by flow cytometry. The blood levels of cytokines including interferons (IFNs) were measured by electrochemiluminescence assay or cytokine beads array.

RESULTS

Active SLE patients exhibited the increased frequency of Tph1, Tph2, Tfh1, and Tfh2 subsets when compared to inactive patients, but no clear changes in the other subsets. During the treatment with medications, Tph1, Tph2, and Tfh2 subsets were significantly reduced along with disease activity and Tph1 and Tph2 subsets were positively correlated with SLE disease activity index (SLEDAI). The time course analysis of patients at pre- and post-flare revealed that in the patients at LLDAS before flare, Tph subsets and Tfh subsets were relatively low levels. At the flare, Tph cells, particularly Tph1 and Tph2 subsets, were increased and correlated with SLEDAI. Furthermore, the blood levels of IFN-α2a, IFN-γ, and IFN-λ1 were low in the patients with LLDAS before flare but these IFNs, particularly IFN-λ1, were increased along with flare.

CONCLUSION

Increased frequency of Tph1 and Tph2 subsets and elevated levels of serum IFN-λ1 are presumably critical for triggering of flare in SLE.

Uncoupling interferons and the interferon signature explains clinical and transcriptional subsets in SLE

Systemic lupus erythematosus (SLE) displays a hallmark interferon (IFN) signature. Yet, clinical trials targeting type I IFN (IFN-I) have shown variable efficacy, and blocking IFN-II failed to treat SLE. Here, we show that IFN type levels in SLE vary significantly across clinical and transcriptional endotypes. Whereas skin involvement correlated with IFN-I alone, systemic features like nephritis associated with co-elevation of IFN-I, IFN-II, and IFN-III, indicating additive IFN effects in severe SLE. Notably, while high IFN-II/-III levels without IFN-I had a limited effect on disease activity, IFN-II was linked to IFN-I-independent transcriptional profiles (e.g., OXPHOS and CD8+GZMH+ cells), and IFN-III enhanced IFN-induced gene expression when co-elevated with IFN-I. Moreover, dysregulated IFNs do not explain the IFN signature in 64% of patients or clinical manifestations including cytopenia, serositis, and anti-phospholipid syndrome, implying IFN-independent endotypes in SLE. This study sheds light on mechanisms underlying SLE heterogeneity and the variable response to IFN-targeted therapies in clinical trials.

Biomarkers Associated with Drugs for the Treatment of Lupus Nephritis

The constant updating of lupus drug treatment guidelines has led to a question. How can the efficacy of treatment be more effectively monitored? Systemic lupus erythematosus (SLE) is a complex autoimmune disease that often presents clinically with multi-organ involvement, and approximately 30% of patients with SLE develop lupus nephritis (LN). Therefore, it is important to better track disease progression and drug efficacy. Now, kidney biopsy is still the gold standard for diagnosing and guiding the treatment of LN, but it is invasive and expensive. If simple, non-invasive and effective biomarkers can be found, drug intervention and prognosis can be better monitored and targeted. In this review, we focus on LN and explore biomarkers related to LN therapeutics, providing clinicians with more possibilities to track the therapeutic effect of drugs, improve treatment options and assess patient outcomes.

Uncoupling interferons and the interferon signature explain clinical and transcriptional subsets in SLE

Interferons (IFN) are thought to be key players in systemic lupus erythematosus (SLE). The unique and interactive roles of the different IFN families in SLE pathogenesis, however, remain poorly understood. Using reporter cells engineered to precisely quantify IFN-I, IFN-II and IFN-III activity levels in serum/plasma, we found that while IFNs play essential role in SLE pathogenesis and disease activity, they are only significant in specific subsets of patients. Interestingly, whereas IFN-I is the main IFN that governs disease activity in SLE, clinical subsets are defined by the co-elevation of IFN-II and IFN-III. Thus, increased IFN-I alone was only associated with cutaneous lupus. In contrast, systemic features, such as nephritis, were linked to co-elevation of IFN-I plus IFN-II and IFN-III, implying a synergistic effect of IFNs in severe SLE. Intriguingly, while increased IFN-I levels were strongly associated with IFN-induced gene expression (93.5%), in up to 64% of cases, the IFN signature was not associated with IFN-I. Importantly, neither IFN-II nor IFN-III explained IFN-induced gene expression in patients with normal IFN-I levels, and not every feature in SLE was associated with elevated IFNs, suggesting IFN-independent subsets in SLE. Together, the data suggest that, unlike the IFN signature, direct quantification of bioactive IFNs can identify pathogenic and clinically relevant SLE subsets amenable for precise anti-IFN therapies. Since IFN-I is only elevated in a subset of SLE patients expressing the IFN signature, this study explains the heterogeneous response in clinical trials targeting IFN-I, where patients were selected based on IFN-induced gene expression rather than IFN-I levels.

Pathogenic cellular and molecular mediators in lupus nephritis

Kidney involvement in patients with systemic lupus erythematosus - lupus nephritis (LN) - is one of the most important and common clinical manifestations of this disease and occurs in 40-60% of patients. Current treatment regimens achieve a complete kidney response in only a minority of affected individuals, and 10-15% of patients with LN develop kidney failure, with its attendant morbidity and considerable prognostic implications. Moreover, the medications most often used to treat LN - corticosteroids in combination with immunosuppressive or cytotoxic drugs - are associated with substantial side effects. Advances in proteomics, flow cytometry and RNA sequencing have led to important new insights into immune cells, molecules and mechanistic pathways that are instrumental in the pathogenesis of LN. These insights, together with a renewed focus on the study of human LN kidney tissue, suggest new therapeutic targets that are already being tested in lupus animal models and early-phase clinical trials and, as such, are hoped to eventually lead to meaningful improvements in the care of patients with systemic lupus erythematosus-associated kidney disease.

Autoantibodies associated with systemic sclerosis in three autoimmune diseases imprinted by type I interferon gene dysregulation: a comparison across SLE, primary Sjögren's syndrome and systemic sclerosis

OBJECTIVE

SLE, primary Sjögren's syndrome (pSS) and systemic sclerosis (SSc) are heterogeneous autoimmune diseases with a dysregulated type I interferon (IFN) system. The diseases often show overlapping clinical manifestations, which may result in diagnostic challenges. We asked to which extent SSc-associated autoantibodies are present in SLE and pSS, and whether these link to serum IFN-α, clinical phenotypes and sex. Samples with clinical data from patients with SSc and healthy blood donors (HBDs) served as controls. Finally, the diagnostic performance of SSc-associated autoantibodies was evaluated.

METHODS

Samples from well-characterised subjects with SLE (n=510), pSS (n=116), SSc (n=57) and HBDs (n=236) were analysed using a commercially available immunoassay (EuroLine Systemic Sclerosis Profile (IgG)). IFN-α was quantified by ELISA. Self-reported data on Raynaud's phenomenon (RP) were available.

RESULTS

With exceptions for anti-Ro52/SSA and anti-Th/To, SSc-associated autoantibodies were more frequent in SSc than in SLE, pSS and HBDs regardless of sex. IFN-α levels correlated with the number of positive SSc-associated autoantibodies (r=0.29, p<0.0001) and associated with Ro52/SSA positivity (p<0.0001). By using data from SLE, SSc and HBDs, RP was significantly associated with topoisomerase I, centromere protein (CENP)-B, RNA polymerase III 11 kDa, RNA polymerase III 155 kDa and PM-Scl100 whereas Ro52/SSA associated inversely with RP. In SLE, CENP-A was associated with immunological disorder, CENP-B with serositis and Ku with lupus nephritis. By combining analysis of ANA (immunofluorescence) with SSc-associated autoantibodies, the diagnostic sensitivity reached 98% and the specificity 33%.

CONCLUSIONS

The 13 specificities included in the EuroLine immunoassay are commonly detected in SSc, but they are also frequent among individuals with other diseases imprinted by type I IFNs. These findings are valuable when interpreting serological data on patients with suspected SSc, especially as patients may present with disease manifestations overlapping different rheumatological diseases. In SLE, we observed associations between manifestations and SSc-associated autoantibodies which have not previously been reported.

Placental damage in pregnancies with systemic lupus erythematosus: A narrative review

Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disease of unknown cause, which mainly affects women of childbearing age, especially between 15 and 55 years of age. During pregnancy, SLE is associated with a high risk of perinatal morbidity and mortality. Among the most frequent complications are spontaneous abortion, fetal death, prematurity, intrauterine Fetal growth restriction (FGR), and preeclampsia (PE). The pathophysiology underlying obstetric mortality and morbidity in SLE is still under investigation, but several studies in recent years have suggested that placental dysfunction may play a crucial role. Understanding this association will contribute to developing therapeutic options and improving patient management thus reducing the occurrence of adverse pregnancy outcomes in this group of women. In this review, we will focus on the relationship between SLE and placental insufficiency leading to adverse pregnancy outcomes.

Jak Inhibitors for Treatment of Autoimmune Diseases: Lessons from Systemic Sclerosis and Systemic Lupus Erythematosus

Systemic sclerosis and systemic lupus erythematosus represent two distinct autoimmune diseases belonging to the group of connective tissue disorders. Despite the great progress in the basic science, this progress has not been translated to the development of novel therapeutic approaches that can radically change the face of these diseases. The discovery of JAK kinases, which are tyrosine kinases coupled with cytokine receptors, may open a new chapter in the treatment of so far untreatable diseases. Small synthetic compounds that can block Janus kinases and interact directly with cytokine signalling may provide therapeutic potential in these diseases. In this review, we discuss the therapeutic potential of Jak kinases in light of the cytokine network that JAK kinases are able to interact with. We also provide the theoretical background for the rationale of blocking cytokines with specific JAK inhibitors.

Role of interferons (IFNs) in the differentiation of T peripheral helper (Tph) cells 2. IFN-α and IFN-λ1 cooperatively contribute to the expansion of Tph cells in systemic lupus erythematosus

Interleukin (IL)-21-producing T peripheral helper (Tph) cells are thought to contribute to extra-follicular B cell activation and play a pathogenic role in autoimmune diseases. In this study, we investigated relationship between Tph cells and interferons (IFNs) in several autoimmune diseases because our previous study demonstrated that type I IFNs promote differentiation of IL-21-producing Tph-like cells. Frequency of Tph cells in the blood as well as serum IFN-α2a and IFN-λ1 were markedly elevated in patients with active systemic lupus erythematosus (SLE) compared to other autoimmune diseases or healthy controls. Notably, frequency of Tph cells were positively correlated with SLE disease activity index, serum IFN-α, and serum IFN-λ1 in SLE patients. Additionally, we found that type III IFNs (IFN-λ1, IFN-λ2, and IFN-λ3) promote differentiation of programmed cell death-1 (PD-1)-positive CXCR5 -CD4 + T cells and enhance secretion of IL-21, IFN-γ, and CXCL13. IFN-λ1, like IFN-α, up-regulated the mRNA expression of IL21, IFNG, CXCL13, CD244, SLAMF7, GZMB, PRF1, CCR5, and PRDM1, whereas down-regulated that of CXCR5 and BCL6, reflecting a Tph-related gene expression pattern. IFN-α in combination with IFN-λ1, IFN-λ2, or IFN-λ3 significantly increased differentiation of PD-1 +CXCR5 - Tph-like cells and secretion of Tph-related cytokines as compared with each IFN alone, suggesting a cooperative interaction. From these findings, it is highly probable that type III IFNs in addition to type I IFNs play a key role in differentiation of Tph cells and that high levels of IFN-α and IFN-λ1 trigger differentiation and expansion of Tph cells in SLE. (242 words).

B cells in systemic lupus erythematosus

PURPOSE OF REVIEW

New insight into altered B cell distribution including newly identified subsets and abnormalities in systemic lupus erythematosus (SLE) as well as their role in immune protection are summarized in this review.

RECENT FINDINGS

SLE carries characteristic B cell abnormalities, which offer new insights into B cell differentiation and their disturbances including discoveries of pathogenic B cell subsets and intrinsic B cell abnormalities. A recent study in SLE found that antigen-experienced B cell subsets lacking expression of CD27 and IgD defined by their lack of CXCR5 and CD19low expression are expanded in SLE and represent plasmablasts likely escaping proper selection. In terms of therapeutic targeting with broader coverage than rituximab, second-generation anti-CD20, anti-CD38 and CD19-CART treatment experiences have advanced our understanding recently. However, the key role of qualitative and quantitative B cell requirements in connection with T cells became apparent during SARS-Cov2 infection and vaccination, especially in patients with gradual B cell impairments by rituximab, mycophenolate mofetil and cyclophosphamide.

SUMMARY

Identification and characterization relevant B cell subsets together with altered regulatory mechanisms in SLE facilitates new approaches in targeting pathogenic B cells but require consideration of preservation of protection.

Type I Interferons in Systemic Lupus Erythematosus: A Journey from Bench to Bedside

Dysregulation of type I interferons (IFNs) has been implicated in the pathogenesis of systemic lupus erythematosus (SLE) since the late 1970s. The majority of SLE patients demonstrate evidence of type I IFN pathway activation; however, studies attempting to address the relationship between type I IFN signature and SLE disease activity have yielded conflicting results. In addition to type I IFNs, type II and III IFNs may overlap and also contribute to the IFN signature. Different genetic backgrounds lead to overproduction of type I IFNs in SLE and contribute to the breakdown of peripheral tolerance by activation of antigen-presenting myeloid dendritic cells, thus triggering the expansion and differentiation of autoreactive lymphocytes. The consequence of the continuous stimulation of the immune system is manifested in different organ systems typical of SLE (e.g., mucocutaneous and cardiovascular involvement). After the discovery of the type I IFN signature, a number of different strategies have been developed to downregulate the IFN system in SLE patients, finally leading to the successful trial of anifrolumab, the second biologic to be approved for the treatment of SLE in 10 years. In this review, we will discuss the bench to bedside translation of the type I IFN pathway and put forward some issues that remain unresolved when selecting SLE patients for treatment with biologics targeting type I IFNs.

Type III Interferons: Emerging Roles in Autoimmunity

Type III interferons (IFNs) or the lambda IFNs (IFNLs or IFN-λs) are antimicrobial cytokines that play key roles in immune host defense at endothelial and epithelial barriers. IFNLs signal via their heterodimeric receptor, comprised of two subunits, IFNLR1 and interleukin (IL)10Rβ, which defines the cellular specificity of the responses to the cytokines. Recent studies show that IFNL signaling regulates CD4+ T cell differentiation, favoring Th1 cells, which has led to the identification of IFNL as a putative therapeutic target for autoimmune diseases. Here, we summarize the IFNL signaling pathways during antimicrobial immunity, IFNL-mediated immunomodulation of both innate and adaptive immune cells, and induction of autoimmunity.

Cytokines as Biomarkers in Systemic Lupus Erythematosus: Value for Diagnosis and Drug Therapy

Systemic Lupus Erythematosus (SLE) is a chronic autoimmune disease. The disease is characterized by activation and dysregulation of both the innate and the adaptive immune systems. The autoimmune response targets self-molecules including cell nuclei, double stranded DNA and other intra and extracellular structures. Multiple susceptibility genes within the immune system have been identified, as well as disturbances in different immune pathways. SLE may affect different organs and organ systems, and organ involvement is diverse among individuals. A universal understanding of pathophysiological mechanism of the disease, as well as directed therapies, are still missing. Cytokines are immunomodulating molecules produced by cells of the immune system. Interferons (IFNs) are a broad group of cytokines, primarily produced by the innate immune system. The IFN system has been observed to be dysregulated in SLE, and therefore IFNs have been extensively studied with a hope to understand the disease mechanisms and identify novel targeted therapies. In several autoimmune diseases identification and subsequent blockade of specific cytokines has led to successful therapies, for example tumor necrosis factor-alpha (TNF-α) inhibition in rheumatoid arthritis. Authors of this review have sought corresponding developments in SLE. In the current review, we cover the actual knowledge on IFNs and other studied cytokines as biomarkers and treatment targets in SLE.

Siglec-H-Deficient Mice Show Enhanced Type I IFN Responses, but Do Not Develop Autoimmunity After Influenza or LCMV Infections

Siglec-H is a DAP12-associated receptor on plasmacytoid dendritic cells (pDCs) and microglia. Siglec-H inhibits TLR9-induced IFN-α production by pDCs. Previously, it was found that Siglec-H-deficient mice develop a lupus-like severe autoimmune disease after persistent murine cytomegalovirus (mCMV) infection. This was due to enhanced type I interferon responses, including IFN-α. Here we examined, whether other virus infections can also induce autoimmunity in Siglec-H-deficient mice. To this end we infected Siglec-H-deficient mice with influenza virus or with Lymphocytic Choriomeningitis virus (LCMV) clone 13. With both types of viruses we did not observe induction of autoimmune disease in Siglec-H-deficient mice. This can be explained by the fact that both types of viruses are ssRNA viruses that engage TLR7, rather than TLR9. Also, Influenza causes an acute infection that is rapidly cleared and the chronicity of LCMV clone 13 may not be sufficient and may rather suppress pDC functions. Siglec-H inhibited exclusively TLR-9 driven type I interferon responses, but did not affect type II or type III interferon production by pDCs. Siglec-H-deficient pDCs showed impaired Hck expression, which is a Src-family kinase expressed in myeloid cells, and downmodulation of the chemokine receptor CCR9, that has important functions for pDCs. Accordingly, Siglec-H-deficient pDCs showed impaired migration towards the CCR9 ligand CCL25. Furthermore, autoimmune-related genes such as Klk1 and DNase1l3 are downregulated in Siglec-H-deficient pDCs as well. From these findings we conclude that Siglec-H controls TLR-9-dependent, but not TLR-7 dependent inflammatory responses after virus infections and regulates chemokine responsiveness of pDCs.

Interferon Lambda 3/4 (IFNλ3/4) rs12979860 Polymorphisms Is Not Associated With Susceptibility to Systemic Lupus Erythematosus, Although It Regulates OASL Expression in Patients With SLE

Systemic lupus erythematosus (SLE) is an autoimmune disease with a complex etiology. Various genetic factors are associated with susceptibility to developing SLE and contribute to its onset and progression. Different single-nucleotide polymorphisms (SNPs) have been associated with SLE in several populations. The rs12979860 SNP in interferon lambda 3/4 (IFNλ3/4) is significantly associated with SLE susceptibility in patients negative for nephritis in Taiwanese people, and interferon-stimulated genes (ISGs) are differentially expressed in normal liver by the rs12979860 genotype. This study aimed to investigate whether rs12979860 is associated with the presence of SLE and lupus nephritis in Mexican individuals as well as with the expression of several ISGs in SLE patients. In total, 439 SLE patients and 358 healthy donors were genotyped for rs12979860 using real-time PCR, and allelic discrimination plots were constructed. Additionally, peripheral blood mononuclear cells (PBMCs) were isolated from the venous blood of SLE patients by centrifugation (n = 78). The mRNA levels of 2′-5′-oligoadenylate synthetase like (OASL), myxovirus resistance 1 (MX1), 2′5′-oligoadenylate synthetase 1 (OAS1), interferon-stimulated gene 15 (ISG15) and lymphocyte antigen 6 complex, locus E (LY6E) were determined using real-time PCR. The distributions of rs12979860 genotypes and allele frequencies were compared between SLE patients and healthy donors; case-control analysis revealed that rs12979860 was not associated with SLE susceptibility (OR 1.18, 95% CI 0.97–1.45, p = 0.08) or with the risk for lupus nephritis (OR 0.913, 95% CI 0.590–1.411, p = 0.682). However, OASL expression levels in PBMCs were significantly different between rs12979860 genotypes in SLE patients: median OASL mRNA levels were significantly higher in patients carrying the CC genotype (197.10, IQR 71.10–411.17) than in those with CT/TT genotypes (173.75, IQR 58.80–278.75, p = 0.016). Our results suggest that the SNP rs12979860 does not play a relevant role in susceptibility to SLE in Mexican individuals. However, IFNλ3/4 genotypes appear to be associated with OASL expression in PBMCs from patients with SLE.

Interferon lambda in inflammation and autoimmune rheumatic diseases

Interferons are potent antiviral cytokines that modulate immunity in response to infection or other danger signals. In addition to their antiviral functions, type I interferons (IFNα and IFNβ) are important in the pathogenesis of autoimmune diseases. Type III interferons (IFNλs) were initially described as a specialized system that inhibits viral replication at epithelial barrier surfaces while limiting inflammatory damage. However, evidence now suggests that type III interferons have complex effects on both innate and adaptive immune responses and might also be pathogenic in systemic autoimmune diseases. Concentrations of IFNλs are increased in blood and tissues in a number of autoimmune rheumatic diseases, including systemic lupus erythematosus, and are further associated with specific clinical and laboratory parameters. This Review is aimed at providing a critical evaluation of the current literature on IFNλ biology and how type III interferons might contribute to immune dysregulation and tissue damage in autoimmunity. The potential effects of type III interferons on treatment strategies for autoimmune rheumatic diseases, such as interferon blockade, are also considered.

Conventional Type 1 Dendritic Cells (cDC1) in Human Kidney Diseases: Clinico-Pathological Correlations

Background

cDC1 is a subset of conventional DCs, whose most recognized function is cross-presentation to CD8⁺ T cells. We conducted this study to investigate the number and location of cDC1s in various human kidney diseases as well as their correlation with clinico-pathological features and CD8⁺ T cells.

Methods

We analyzed 135 kidney biopsies samples. Kidney diseases included: acute tubular necrosis (ATN), acute interstitial nephritis (AIN), proliferative glomerulonephritis (GN) (IgA nephropathy, lupus nephritis, pauci-immune GN, anti-GBM disease), non-proliferative GN (minimal change disease, membranous nephropathy) and diabetic nephropathy. Indirect immunofluorescence staining was used to quantify cDC1s, CD1c⁺ DCs, and CD8⁺ T cells.

Results

cDC1s were rarely present in normal kidneys. Their number increased significantly in ATN and proliferative GN, proportionally much more than CD1c⁺ DCs. cDC1s were mainly found in the interstitium, except in lupus nephritis, pauci-immune GN and anti-GBM disease, where they were prominent in glomeruli and peri-glomerular regions. The number of cDC1s correlated with disease severity in ATN, number of crescents in pauci-immune GN, interstitial fibrosis in IgA nephropathy and lupus nephritis, as well as prognosis in IgA nephropathy. The number of CD8⁺ T cells also increased significantly in these conditions and cDC1 number correlated with CD8⁺ T cell number in lupus nephritis and pauci-immune GN, with many of them closely co-localized.

Conclusions

cDC1 number correlated with various clinic-pathological features and prognosis reflecting a possible role in these conditions. Their association with CD8⁺ T cells suggests a combined mechanism in keeping with the results in animal models.

Single-Cell Transcriptomic Analyses Define Distinct Peripheral B Cell Subsets and Discrete Development Pathways

Separation of B cells into different subsets has been useful to understand their different functions in various immune scenarios. In some instances, the subsets defined by phenotypic FACS separation are relatively homogeneous and so establishing the functions associated with them is straightforward. Other subsets, such as the “Double negative” (DN, CD19+CD27-IgD-) population, are more complex with reports of differing functionality which could indicate a heterogeneous population. Recent advances in single-cell techniques enable an alternative route to characterize cells based on their transcriptome. To maximize immunological insight, we need to match prior data from phenotype-based studies with the finer granularity of the single-cell transcriptomic signatures. We also need to be able to define meaningful B cell subsets from single cell analyses performed on PBMCs, where the relative paucity of a B cell signature means that defining B cell subsets within the whole is challenging. Here we provide a reference single-cell dataset based on phenotypically sorted B cells and an unbiased procedure to better classify functional B cell subsets in the peripheral blood, particularly useful in establishing a baseline cellular landscape and in extracting significant changes with respect to this baseline from single-cell datasets. We find 10 different clusters of B cells and applied a novel, geometry-inspired, method to RNA velocity estimates in order to evaluate the dynamic transitions between B cell clusters. This indicated the presence of two main developmental branches of memory B cells. A T-independent branch that involves IgM memory cells and two DN subpopulations, culminating in a population thought to be associated with Age related B cells and the extrafollicular response. The other, T-dependent, branch involves a third DN cluster which appears to be a precursor of classical memory cells. In addition, we identify a novel DN4 population, which is IgE rich and closely linked to the classical/precursor memory branch suggesting an IgE specific T-dependent cell population.

Bite of the wolf: innate immune responses propagate autoimmunity in lupus

The etiopathogenesis of systemic lupus erythematosus (SLE), a clinically heterogeneous multisystemic syndrome that derives its name from the initial characterization of facial lesions that resemble the bite of a wolf, is considered a complex, multifactorial interplay between underlying genetic susceptibility factors and the environment. Prominent pathogenic factors include the induction of aberrant cell death pathways coupled with defective cell death clearance mechanisms that promote excessive externalization of modified cellular and nuclear debris with subsequent loss of tolerance to a wide variety of autoantigens and innate and adaptive immune dysregulation. While abnormalities in adaptive immunity are well recognized and are key to the pathogenesis of SLE, recent findings have emphasized fundamental roles of the innate immune system in the initiation and propagation of autoimmunity and the development of organ damage in this disease. This Review focuses on recent discoveries regarding the role of components of the innate immune system, specifically neutrophils and interferons, in promoting various aspects of lupus pathogenesis, with potential implications for novel therapeutic strategies.

Systemic lupus erythematosus (SLE): emerging therapeutic targets

INTRODUCTION

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease with a heterogeneous clinical presentation whose etiologies are multifactorial. A myriad of genetic, hormonal, immunologic, and environmental factors contribute to its pathogenesis, and its diverse biological basis and phenotypic presentations make development of therapeutics difficult. In the past decade, tens of therapeutic targets with hundreds of individual candidate therapeutics have been investigated.

AREAS COVERED

We used a PUBMED database search through April 2020 to review the relevant literature. This review discusses therapeutic targets in the adaptive and innate immune systems, specifically: B cell surface antigens, B cell survival factors, Bruton's tyrosine kinase, costimulators, IL-12/IL-23, the calcineurin pathway, the JAK/STAT pathway, and interferons.

EXPERT OPINION

Our ever-improving understanding of SLE pathophysiology in the past decade has allowed us to identify new therapeutic targets. Multiple new drugs are on the horizon that target different elements of the adaptive and innate immune systems. SLE research remains challenging due to the heterogenous clinical presentation of SLE, confounding from background immunosuppressives being taken by SLE patients, animal models that inadequately recapitulate human disease, and imperfect and complicated outcome measures. Despite these limitations, research is promising and ongoing. The search for new therapies that target specific elements of SLE pathophysiology are discussed as well as key findings, pitfalls, and questions surrounding these targets.

Plasma C4d Correlates With C4d Deposition in Kidneys and With Treatment Response in Lupus Nephritis Patients

Objective

To examine whether C4d plasma levels correlate with treatment response and C4d kidney deposition in systemic lupus erythematosus (SLE) with lupus nephritis (LN).

Methods

C4d plasma levels were analyzed by a unique assay specifically detecting C4d arising from complement activation and C4 plasma levels were quantified with competitive ELISA. SLE patients with LN (71) and active SLE patients without LN (22) plus 145 controls were included. For 52 LN patients samples were available both at baseline and after immunosuppressive treatment. C4d kidney deposition was detected using immunohistochemistry in two matching kidney biopsies of 12 LN patients.

Results

In comparison to population-based controls, plasma C4d levels were significantly increased in SLE patients (0.33 mg/L versus 0.94 mg/ml, p < 0.0001) with significantly higher levels in LN patients (1.02 mg/L) than in non-renal SLE patients (0.57 mg/L, p = 0.004). The C4d/C4 ratio was also significantly higher in LN (11.2) than in non-renal SLE patients (2.5, p = 0.0002). According to ROC curve analysis, C4d was found to be an accurate marker to discriminate LN from non-renal SLE patients (p = 0.004). The C4d/C4 ratio displayed even higher specificity, sensitivity and overall accuracy as marker for LN than C4d and C4 alone. At baseline, C4d levels correlated significantly with urine-albumin to creatinine ratio (r _s = 0.43, p = 0.011) and with renal activity index (r _s = 0.37, p = 0.002). Immunohistochemical staining showed glomerular deposits of C4d in kidney biopsies, which strikingly correlated with plasma C4d levels (r _s = 0.7, p = 0.0002). Plasma C4d declined significantly after treatment in patients that experienced favorable clinical and histopathological response (p < 0.0001), while levels remained mainly unchanged in non-responders.

Conclusion

Plasma C4d discriminates LN from active non-renal SLE, correlates with C4d kidney deposits and appears valuable in monitoring responsiveness to various treatments. The C4d/C4 ratio might be superior to C4d alone.

Impact of IL-34, IFN-α and IFN-λ1 on activity of systemic lupus erythematosus in Egyptian patients

Background

Systemic lupus erythematosus (SLE) is an autoimmune, multi-system inflammatory disease. Among cytokines involved in SLE pathogenesis, interferons (particularly IFN-α) and interleukin 34 play a pivotal role. Interestingly, the gene signatures of type III (IFN-λ1) and type I IFNs may overlap. Increased levels of IFN-λ also have been reported in SLE.

Objectives: The aim of this study was to assess serum levels of IL-34, IFN-λ1, IFN-α and the relationship between these cytokines and clinical and laboratory parameters and response to treatment in a cohort of Egyptian SLE patients.

Material and methods

The study included 82 newly diagnosed SLE patients: male 17.1% (n = 14), female 82.9% (n = 68), mean age ±SD: 48.6 ±8.2 and 60 healthy subjects matched by age and gender as a control group. Medical history, physical examination and laboratory tests for confirming SLE diagnosis and assessment of disease activity were collected. The assessment of serum levels of studied cytokines were performed using the ELISA method.

All studied patients after first cytokine evaluation were treated with a combination of antimalarial drugs, glucocorticosteroids and/or immunosuppressive drugs with follow-up after six months of treatment.

Results

In the SLE group the mean serum levels of IL-34, IFN-α and IFN-λ1 were 175.9 ±125.9 pg/ml, 109.3 ±32.5 pg/ml and 227.9 ±144.8 pg/ml respectively. These cytokine levels were significantly higher in the SLE group than in healthy controls. 39% of SLE patients (n = 32) had SLAM > 6 and 26.8% (n = 22) had SLEDAI >6. There were 21 SLE patients (25.6%) with lupus nephritis.

IL-34 and IFN-λ1 were positively correlated with anti-dsDNA antibodies but negatively correlated with C3 complement component (p ≤ 0.05). IL-34, INF-α and IFN-λ1 were significantly higher in lupus nephritis patients, and correlated with poorest response to treatment.

IL-34 and IFN-λ1 were correlated with higher SLAM > 6 and SLEDAI > 6 results; there was no such correlation between IFN-α and disease activity.

Accumulation of three or more clinical features during follow-up was significantly associated with high levels of studied cytokines. Triple high positivity was found in 17 patients (20.7%) and correlated with presence of anti-dsDNA antibodies, low levels of C3 component of complement and lupus nephritis.

Conclusions

SLE patients with high serum levels of IL-34, IFN-α and IFN-λ1 more often had lupus nephritis and poor response to immunosuppressive treatment.

The triple cytokine elevation was strongly associated with higher disease activity. These results may indicate the need to distinguish this group of patients with such aggressive phenotype and consider targeted multi-therapy.

The regulation and pharmacological modulation of immune complex induced type III IFN production by plasmacytoid dendritic cells

OBJECTIVE

Patients with systemic lupus erythematosus (SLE) have an ongoing interferon (IFN) production due to an activation of plasmacytoid dendritic cells (pDCs), which can be triggered to type I IFN synthesis by RNA containing immune complexes (RNA-IC). Considering emerging data suggesting a role of type III IFN in the SLE disease process, we asked if RNA-IC can induce type III IFN production in pDC and how this production can be regulated.

METHODS

Peripheral blood mononuclear cells (PBMCs) or immune cell subsets were isolated from healthy blood donors or SLE patients and stimulated with IC containing U1 snRNP and SLE-IgG (RNA-IC). Hydroxychloroquine (HCQ) and an interleukin receptor 1-associated kinase 4 inhibitor (IRAK4i) were added to cell cultures. Cytokine mRNA levels were determined with a microarray and protein levels with immunoassays. Single-cell RNA sequencing of pDCs using ddSEQ technology was performed.

RESULTS

Type III IFN mRNA and protein was induced in RNA-IC-stimulated pDC-NK and pDC-B cell co-cultures. A subset of activated pDCs (3%) expressed both type III and type I IFN mRNA. IFN-λ2, IFN-α2b, interleukin (IL)-3, IL-6, or granulocyte-macrophage colony-stimulating factor (GM-CSF) enhanced IFN-λ1/3 production 2-5-fold. HCQ and an IRAK4i blocked the RNA-IC-triggered IFN-λ1/3 production (p < 0.01). IFN-α2b and GM-CSF increased the proportion of SLE patients producing IFN-λ1/3 in response to RNA-IC from 11 to 33%.

CONCLUSIONS

Type III IFN production is triggered by RNA-IC in pDCs in a TLR-MyD88-dependent manner, enhanced by NK and B cells as well as several pro-inflammatory cytokines. These results support a contributing role for both type I and type III IFNs in SLE, which needs to be considered when targeting the IFN system in this disease.

Autoantibody and Cytokine Profiles during Treatment with Belimumab in Patients with Systemic Lupus Erythematosus

We investigated whether belimumab treatment impacts on levels of autoantibodies and cytokines of interest in systemic lupus erythematosus (SLE). Longitudinally collected serum samples from 78 belimumab-treated Swedish SLE patients were analysed. Serum cytokine levels were determined using Luminex xMAP technology, and nuclear antigen autoantibody specificities using addressable laser bead immunoassay. In patients with detectable levels at baseline, interferon (IFN)-α2 levels were lower at month 6 (median; interquartile range (IQR): 8.9; 1.5-54.9 pg/mL) versus baseline (28.4; 20.9-100.3 pg/mL; p = 0.043). Interleukin (IL)-6 (baseline: 7.1; 2.9-16.1 pg/mL) decreased from month 6 (0.5; 0.5-6.3 pg/mL; p = 0.018) and throughout a 24 month follow-up. IL-10 (baseline: 12.6; 2.8-29.7 pg/mL) showed more rapid decreases from month 3 (1.8; 0.6-9.1 pg/mL; p = 0.003). Levels of anti-dsDNA (p < 0.001), anti-Smith antigen (Sm) (p = 0.002), anti-U1 small nuclear ribonucleoprotein (U1RNP) (p < 0.001), anti-Sm-U1RNP complex (p = 0.028), and anti-ribosomal P (p = 0.012) antibodies decreased from month 3 and remained decreased. Anti-Sm positivity at baseline was associated with higher probability and/or shorter time to achieve sustained SLE responder index-4 response (hazard ratio (HR): 2.52; 95% CI: 1.20-5.29; p = 0.015), independently of other factors. Decline of IL-6 levels through month 3 was greater in responders. In summary, belimumab treatment lowered IFN-α2, IL-6, and IL-10 levels, as well as levels of multiple autoantibodies, however after different time spans. Notably, anti-Sm positivity and early decline in IL-6 levels were associated with favorable treatment outcome.

Interferon lambda promotes immune dysregulation and tissue inflammation in TLR7-induced lupus

Type III IFN lambdas (IFN-λ) have recently been described as important mediators of immune responses at barrier surfaces. However, their role in autoimmune diseases such as systemic lupus erythematosus (SLE), a condition characterized by aberrant type I IFN signaling, has not been determined. Here, we identify a nonredundant role for IFN-λ in immune dysregulation and tissue inflammation in a model of TLR7-induced lupus. IFN-λ protein is increased in murine lupus and IFN-λ receptor (Ifnlr1) deficiency significantly reduces immune cell activation and associated organ damage in the skin and kidneys without effects on autoantibody production. Single-cell RNA sequencing in mouse spleen and human peripheral blood revealed that only mouse neutrophils and human B cells are directly responsive to this cytokine. Rather, IFN-λ activates keratinocytes and mesangial cells to produce chemokines that induce immune cell recruitment and promote tissue inflammation. These data provide insights into the immunobiology of SLE and identify type III IFNs as important factors for tissue-specific pathology in this disease.

Prediction of prognosis and renal outcome in lupus nephritis

Lupus nephritis (LN) is a severe manifestation of SLE, characterised by subendothelial and/or subepithelial immune complex depositions in the afflicted kidney, resulting in extensive injury and nephron loss during the acute phase and eventually chronic irreversible damage and renal function impairment if not treated effectively. The therapeutic management of LN has improved during the last decades, but the imperative need for consensual outcome measures remains. In order to design trials with success potentiality, it is important to define clinically important short-term and long-term targets of therapeutic and non-therapeutic intervention. While it is known that early response to treatment is coupled with favourable renal outcomes, early predictors of renal function impairment are lacking. The information gleaned from kidney biopsies may provide important insights in this direction. Alas, baseline clinical and histopathological information has not been shown to be informative. By contrast, accumulating evidence of pronounced discrepancies between clinical and histopathological outcomes after the initial phase of immunosuppression has prompted investigations of the potential usefulness of per-protocol repeat kidney biopsies as an integral part of treatment evaluation, including patients showing adequate clinical response. This approach appears to have merit. Hopefully, clinical, molecular or genetic markers that reliably reflect kidney histopathology and portend the long-term prognosis will be identified. Novel non-invasive imaging methods and employment of the evolving artificial intelligence in pattern recognition may also be helpful towards these goals. The molecular and cellular characterisation of SLE and LN will hopefully result in novel therapeutic modalities, maybe new taxonomy perspectives, and ultimately personalised management.

Type III Interferons (Lambda Interferons) in Rheumatic Autoimmune Diseases

The last 2 decades have witnessed the discovery and characterization of a new family of cytokines with immunological characteristics similar to those described for type I interferons, type III or lambda interferons. Unraveling the molecular mechanisms underlying each type of interferon has allowed us to understand how some autoimmune diseases can be considered as interferonopathies. Under normal conditions, type III interferons play a key role in the defense against viruses by modulating the functioning of several types of innate and adaptive immune cells. These effects include upregulation of major histocompatibility complex molecules by myeloid dendritic cells, increased functioning of pattern recognition receptors by plasmacytoid dendritic cells, decreased activity of regulatory T cells, enhanced production of antibodies by plasmatic cells and increased expression of chemokines and adhesion molecules by leukocytes and endothelial cells. Notably, all these mechanisms have been described to boost autoimmunity, and type III interferons pathway activation has been related to the pathogenesis of autoimmune conditions such as systemic lupus erythematosus, systemic sclerosis and Sjögren's syndrome. This review provides an overview of the current evidence on the contribution of type III interferons in the pathogenesis of rheumatic autoimmune diseases in humans.

Dysregulated Fcγ receptor IIa-induced cytokine production in dendritic cells of lupus nephritis patients

Systemic lupus erythematosus (SLE) is an autoimmune disease of unknown etiology. One of the key factors associated with SLE pathogenesis is excessive production of type I interferons (IFNs). This could result from increased activation of type I IFN-stimulating pathways, but also from decreased activation of type I IFN-inhibitory pathways. Recently, we have identified that immunoglobulin (Ig)G immune complexes strongly inhibit type I IFN production in healthy individuals by inhibitory signaling through Fcγ receptor IIa (FcγRIIa) on dendritic cells (DCs). Because, in SLE patients, immune complexes are characteristically present, we assessed whether FcγR-induced suppression of type I IFN is functional in DCs of SLE patients. We divided the SLE patients into one group without, and one group with, previous major organ involvement, for which we chose nephritis as a prototypical example. We show that DCs of lupus nephritis patients displayed impaired FcγR-mediated type I IFN inhibition compared to SLE patients without major organ involvement or healthy controls. We verified that this impaired type I IFN inhibition was not related to differences in disease activity, medication, FcγRIIa expression or expression of IFN regulatory transcription factors (IRF)1 and IRF5. In addition, we identified that DCs of lupus nephritis patients show increased FcγR-induced interleukin (IL)-1β production, which is another important cytokine that promotes kidney inflammation. Taken together, these data indicate that DCs of lupus nephritis patients display altered FcγR-mediated regulation of cytokine production, resulting in elevated levels of type I IFN and IL-1β. This dysregulation may contribute to the development of nephritis in SLE patients.

Role of Interferon-γ-Producing Th1 Cells in a Murine Model of Type I Interferon-Independent Autoinflammation Resulting From DNase II Deficiency

OBJECTIVE

Patients with hypomorphic mutations in DNase II develop a severe and debilitating autoinflammatory disease. This study was undertaken to compare the disease parameters in these patients to those in a murine model of DNase II deficiency, and to evaluate the role of specific nucleic acid sensors and identify the cell types responsible for driving the autoinflammatory response.

METHODS

To avoid embryonic death, Dnase2^-/- mice were intercrossed with mice that lacked the type I interferon (IFN) receptor (Ifnar^-/- ). The hematologic changes and immune status of these mice were evaluated using complete blood cell counts, flow cytometry, serum cytokine enzyme-linked immunosorbent assays, and liver histology. Effector cell activity was determined by transferring T cells from Dnase2^-/- × Ifnar^-/- double-knockout (DKO) mice into Rag1^-/- mice, and 4 weeks after cell transfer, induced changes were assessed in the recipient mice.

RESULTS

In Dnase2^-/- × Ifnar^-/- DKO mice, many of the disease features found in DNase II-deficient patients were recapitulated, including cytopenia, extramedullary hematopoiesis, and liver fibrosis. Dnase2^+/+ × Rag1^-/- mice (n > 22) developed a hematologic disorder that was attributed to the transfer of an unusual IFNγ-producing T cell subset from the spleens of donor Dnase2^-/- × Ifnar^-/- DKO mice. Autoinflammation in this murine model did not depend on the stimulator of IFN genes (STING) pathway but was highly dependent on the chaperone protein Unc93B1.

CONCLUSION

Dnase2^-/- × Ifnar^-/- DKO mice may be a valid model for exploring the innate and adaptive immune mechanisms responsible for the autoinflammation similar to that seen in DNASE2-hypomorphic patients. In this murine model, IFNγ is required for T cell activation and the development of clinical manifestations. The role of IFNγ in DNASE2-deficient patient populations remains to be determined, but the ability of Dnase2^-/- mouse T cells to transfer disease to Rag1^-/- mice suggests that T cells may be a relevant therapeutic target in patients with IFN-related systemic autoinflammatory diseases.

Lymphopenia and neutropenia are associated with subsequent incident proteinuria in Danish patients with systemic lupus erythematosus

Objective: The aim of this study was to investigate whether incident proteinuria in patients with systemic lupus erythematosus (SLE) was preceded by changes in blood lymphocytes and neutrophil counts and/or neutrophil-lymphocyte ratio (NLR).Method: SLE patients with no proteinuria before or at the time of classification were included. Longitudinal data on SLE manifestations, vital status, and SLE-associated medications were collected during clinical visits and chart review. Laboratory data were collected through a nationwide database. Lymphopenia, severe lymphopenia, and neutropenia were defined as values below 0.8 × 10⁹, 0.5 × 10⁹, and 2.0 × 10⁹ cells/L, respectively. High NLR was defined as values above the median. Proteinuria was defined by at least two measurements of elevated urine protein excretion (> 0.5 g/day). Hazard ratios (HRs) were calculated by Cox modelling using time-dependent continuous and binary covariates based on multiple laboratory measurements adjusted for use of immunosuppressants.Results: In total, 260 SLE patients were available for the analysis, of whom 30 (12%) developed incident proteinuria following the diagnosis of SLE. Median follow-up time was 73.5 months. Lymphocyte and neutrophil counts, but not NLR, were associated with incident proteinuria. HRs for incident proteinuria were 2.71 for lymphopenia [95% confidence interval (CI) 1.20-6.11], 4.73 for severe lymphopenia (95% CI 1.93-11.59), and 2.54 for neutropenia (95% CI 1.14-5.65).Conclusion: Lymphopenia and neutropenia predicted the risk of first-time proteinuria independently of immunosuppressants.

Interferon Lambda and Liver Fibrosis

Fibrosis is a highly conserved and coordinated wound healing response to injury. In the liver, injury is promoted by immune effector mechanisms that are common across various disease etiologies and even between organs such as lungs, kidneys, heart, and other organs. Thus, the liver represents a useful model to study inflammation and repair, particularly as it is frequently biopsied in clinical contexts. Currently, strong evidence implicates IFNL3/4 polymorphisms and interferon (IFN)-λ3 levels as determinants of the extent of hepatic inflammation and fibrosis in viral and nonviral liver diseases, as well as in governing the severity of nonhepatotropic viral diseases. Interestingly, IFNL3/4 polymorphisms and IFN-λ3 levels correlate with fibrosis extent in other organs such as the lung and kidney. In this review, we discuss the association between IFN-λ and tissue inflammation and fibrosis in human disease and the potential clinical utility of the findings.

The role of nucleic acid sensors and type I IFNs in patient populations and animal models of autoinflammation

A spectrum of human autoinflammatory conditions result from defects in cytosolic nucleic acid clearance or overexpression of the nucleic acid sensor STING. These patients often develop severely debilitating lesions and invariably show robust IFN signatures that have been attributed to the cGAS/STING signaling cascade and type I IFN. However, murine models that recapitulate major features of these syndromes have now shown that autoinflammation is more likely to depend on type II IFN/IFNgamma or type III IFN/IFNlambda, and further revealed a critical role for Th1 cells in tissue damage and the persistence of inflammation. These studies provide important insights about the types of IFNs, and the interplay of the innate and adaptive immune systems mediated by these IFNs, that can initiate and maintain the corresponding human diseases. They further point to type II/III IFNs and effector T cells as targets for more effective therapeutic strategies in the treatment of these patient populations.

Signaling Pathways of Type I and Type III Interferons and Targeted Therapies in Systemic Lupus Erythematosus

Type I and type III interferons (IFNs) share several properties in common, including the induction of signaling pathways, the activation of gene transcripts, and immune responses, against viral infection. Recent advances in the understanding of the molecular basis of innate and adaptive immunity have led to the re-examination of the role of these IFNs in autoimmune diseases. To date, a variety of IFN-regulated genes, termed IFN signature genes, have been identified. The expressions of these genes significantly increase in systemic lupus erythematosus (SLE), highlighting the role of type I and type III IFNs in the pathogenesis of SLE. In this review, we first discussed the signaling pathways and the immunoregulatory roles of type I and type III IFNs. Next, we discussed the roles of these IFNs in the pathogenesis of autoimmune diseases, including SLE. In SLE, IFN-stimulated genes induced by IFN signaling contribute to a positive feedback loop of autoimmunity, resulting in perpetual autoimmune inflammation. Based on this, we discussed the use of several specific IFN blocking strategies using anti-IFN-α antibodies, anti-IFN-α receptor antibodies, and IFN-α-kinoid or downstream small molecules, which intervene in Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathways, in clinical trials for SLE patients. Hopefully, the development of novel regimens targeting IFN signaling pathways will shed light on promising future therapeutic applications for SLE patients.

FKN Facilitates HK-2 Cell EMT and Tubulointerstitial Lesions via the Wnt/β-Catenin Pathway in a Murine Model of Lupus Nephritis

Fractalkine (FKN), also known as chemokine (C-X3-C motif) ligand 1, constitutes an intriguing chemokine with a documented role in the development of numerous inflammatory diseases including autoimmune disease. Specifically, it has been reported that FKN is involved in the disease progression of lupus nephritis (LN). The epithelial-mesenchymal transition (EMT) plays a significant role in the formation of tubulointerstitial lesions (TIL), which are increasingly recognized as a hallmark of tissue fibrogenesis after injury. However, the correlation between FKN and EMT or TIL in LN has not been determined. To investigate the potential role of FKN in EMT and TIL, MRL lymphoproliferation (MRL/lpr) strain mice were treated with an anti-FKN antibody, recombinant-FKN chemokine domain, or isotype antibody. Our results revealed that treatment with the anti-FKN antibody improved EMT, TIL, and renal function in MRL/lpr mice, along with inhibiting activation of the Wnt/β-catenin signaling pathway. In contrast, administration of the recombinant-FKN chemokine domain had the opposite effect. Furthermore, to further explore the roles of FKN in EMT, we assessed the levels of EMT markers in FKN-depleted or overexpressing human proximal tubule epithelial HK-2 cells. Our results provide the first evidence that the E-cadherin level was upregulated, whereas α-SMA and vimentin expression was downregulated in FKN-depleted HK-2 cells. In contrast, overexpression of FKN in HK-2 cells enhanced EMT. In addition, inhibition of the Wnt/β-catenin pathway by XAV939 negated the effect of FKN overexpression, whereas activation of the Wnt/β-catenin pathway by Ang II impaired the effect of the FKN knockout on EMT in HK-2 cells. Together, our data indicate that FKN plays essential roles in the EMT progression and development of TIL in MRL/lpr mice, most likely through activation of the Wnt/β-catenin signaling pathway.

Distinct Effector B Cells Induced by Unregulated Toll-like Receptor 7 Contribute to Pathogenic Responses in Systemic Lupus Erythematosus

Systemic Lupus Erythematosus (SLE) is characterized by B cells lacking IgD and CD27 (double negative; DN). We show that DN cell expansions reflected a subset of CXCR5- CD11c+ cells (DN2) representing pre-plasma cells (PC). DN2 cells predominated in African-American patients with active disease and nephritis, anti-Smith and anti-RNA autoantibodies. They expressed a T-bet transcriptional network; increased Toll-like receptor-7 (TLR7); lacked the negative TLR regulator TRAF5; and were hyper-responsive to TLR7. DN2 cells shared with activated naive cells (aNAV), phenotypic and functional features, and similar transcriptomes. Their PC differentiation and autoantibody production was driven by TLR7 in an interleukin-21 (IL-21)-mediated fashion. An in vivo developmental link between aNAV, DN2 cells, and PC was demonstrated by clonal sharing. This study defines a distinct differentiation fate of autoreactive naive B cells into PC precursors with hyper-responsiveness to innate stimuli, as well as establishes prominence of extra-follicular B cell activation in SLE, and identifies therapeutic targets.

Targeting interferons and their pathways in systemic lupus erythematosus

Significant advances in the understanding of the molecular basis of innate immunity have led to the identification of interferons (IFNs), particularly IFN-α, as central mediators in the pathogenesis of Systemic Lupus Erythematosus. Therefore, targeting of IFNs and of their downstream pathways has emerged as important developments for novel drug research in SLE. Based on this, several specific interferon blocking strategies using anti-IFN-α antibodies, anti-type I interferon receptor antibodies, Interferon-α-kinoid, or anti-IFN-γ antibodies have all been assessed in recent clinical trials. Alternative strategies targeting the plasmacytoid dendritic cells (pDCs), Toll-Like Receptors (TLRs)-7/9 or their downstream pathways such as the myeloid differentiation primary-response protein 88 (MYD88), spleen tyrosine kinase (Syk), Janus-kinases (JAKs), interleukin-1 receptor-associated kinase 4 (IRAK4), or the Tyrosine Kinase 2 (TYK2) are also investigated actively in SLE, at more preliminary clinical development stages, except for JAK inhibitors which have reached phase 2 studies. In a near future, in-depth and personalized functional characterization of IFN pathways may provide further guidance for the selection of the most relevant therapeutic strategy in SLE, tailored at the patient-level.

Targeting interferons as a strategy for systemic sclerosis treatment

Systemic Sclerosis (SSc) is an autoimmune disease characterised by vasculopathy, uncontrolled inflammation and enhanced fibrosis which can subsequently lead to the loss of organ function or even premature death. Interferons (IFNs) are pleiotropic cytokines that are critical not only in mounting an effective immune response against viral and bacterial infections but also strongly contribute to the pathogenesis of SSc. Furthermore, elevated levels of IFNs are found in SSc patients and correlate with skin thickness and disease activity suggesting potential role of IFNs as biomarkers. In this review, we summarise existing knowledge regarding all types of IFNs and IFN-inducible genes in the pathogenesis of SSc. We then argue why IFN-blocking strategies are promising therapeutic targets in SSc and other autoimmune diseases.

[Expression of interferon-λ1 in respiratory epithelial cells of children with RSV infection and its relationship with RSV load]

OBJECTIVE

To investigate the expression of IFN-λ1 in respiratory epithelial cells of children with respiratory syncytial virus (RSV) infection and its relationship with RSV load.

METHODS

The nasopharyngeal swabs were collected from the children who were hospitalized with respiratory tract infection from June 2015 to June 2016. A direct immunofluorescence assay was used to detect the antigens of seven common respiratory viruses (including RSV) in the nasopharyngeal swabs. A total of 120 children who were only RSV positive were selected as the RSV infection group. A total of 50 children who had negative results in the detection of all viral antigens were selected as the healthy control group. Fluorescence quantitative real-time PCR was used to determine the RSV load and the expression of IFN-λ1 mRNA in the nasopharyngeal swabs of children in the two groups.

RESULTS

The expression of IFN-λ1 in the RSV infection group was significantly higher than that in the healthy control group (P<0.05). The expression of IFN-λ1 was positively correlated with RSV load (r=0.56, P<0.05).

CONCLUSIONS

RSV can induce the expression of IFN-λ1 in respiratory epithelial cells, suggesting that IFN-λ1 may play an important role in anti-RSV infection.

[Expression of interferon-λ1 in respiratory epithelial cells of children with RSV infection and its relationship with RSV load]

OBJECTIVE

To investigate the expression of IFN-λ1 in respiratory epithelial cells of children with respiratory syncytial virus (RSV) infection and its relationship with RSV load.

METHODS

The nasopharyngeal swabs were collected from the children who were hospitalized with respiratory tract infection from June 2015 to June 2016. A direct immunofluorescence assay was used to detect the antigens of seven common respiratory viruses (including RSV) in the nasopharyngeal swabs. A total of 120 children who were only RSV positive were selected as the RSV infection group. A total of 50 children who had negative results in the detection of all viral antigens were selected as the healthy control group. Fluorescence quantitative real-time PCR was used to determine the RSV load and the expression of IFN-λ1 mRNA in the nasopharyngeal swabs of children in the two groups.

RESULTS

The expression of IFN-λ1 in the RSV infection group was significantly higher than that in the healthy control group (P<0.05). The expression of IFN-λ1 was positively correlated with RSV load (r=0.56, P<0.05).

CONCLUSIONS

RSV can induce the expression of IFN-λ1 in respiratory epithelial cells, suggesting that IFN-λ1 may play an important role in anti-RSV infection.