The conneXion between sex and immune responses

There are notable sex-based differences in immune responses to pathogens and self-antigens, with female individuals exhibiting increased susceptibility to various autoimmune diseases, and male individuals displaying preferential susceptibility to some viral, bacterial, parasitic and fungal infections. Although sex hormones clearly contribute to sex differences in immune cell composition and function, the presence of two X chromosomes in female individuals suggests that differential gene expression of numerous X chromosome-linked immune-related genes may also influence sex-biased innate and adaptive immune cell function in health and disease. Here, we review the sex differences in immune system composition and function, examining how hormones and genetics influence the immune system. We focus on the genetic and epigenetic contributions responsible for altered X chromosome-linked gene expression, and how this impacts sex-biased immune responses in the context of pathogen infection and systemic autoimmunity.

Therapeutic prime/pull vaccination of HSV-2-infected guinea pigs with the ribonucleotide reductase 2 (RR2) protein and CXCL11 chemokine boosts antiviral local tissue-resident and effector memory CD4+ and CD8+ T cells and protects against recurrent genital herpes

Following acute herpes simplex virus type 2 (HSV-2) infection, the virus undergoes an asymptomatic latent infection of sensory neurons of dorsal root ganglia (DRG). Chemical and physical stress cause intermittent virus reactivation from latently infected DRG and recurrent virus shedding in the genital mucosal epithelium causing genital herpes in symptomatic patients. While T cells appear to play a role in controlling virus reactivation from DRG and reducing the severity of recurrent genital herpes, the mechanisms for recruiting these T cells into DRG and the vaginal mucosa (VM) remain to be fully elucidated. The present study investigates the effect of CXCL9, CXCL10, and CXCL11 T-cell-attracting chemokines on the frequency and function of DRG- and VM-resident CD4+ and CD8+ T cells and its effect on the frequency and severity of recurrent genital herpes in the recurrent herpes guinea pig model. HSV-2 latent-infected guinea pigs were immunized intramuscularly with the HSV-2 ribonucleotide reductase 2 (RR2) protein (Prime) and subsequently treated intravaginally with the neurotropic adeno-associated virus type 8 expressing CXCL9, CXCL10, or CXCL11 chemokines to recruit CD4+ and CD8+ T cells into the infected DRG and VM (Pull). Compared to the RR2 therapeutic vaccine alone, the RR2/CXCL11 prime/pull therapeutic vaccine significantly increased the frequencies of functional tissue-resident and effector memory CD4+ and CD8+ T cells in both DRG and VM tissues. This was associated with less virus in the healed genital mucosal epithelium and reduced frequency and severity of recurrent genital herpes. These findings confirm the role of local DRG- and VM-resident CD4+ and CD8+ T cells in reducing virus shedding at the vaginal site of infection and the severity of recurrent genital herpes and propose the novel prime-pull vaccine strategy to protect against recurrent genital herpes.IMPORTANCEThe present study investigates the novel prime/pull therapeutic vaccine strategy to protect against recurrent genital herpes using the latently infected guinea pig model. In this study, we used the strategy that involves immunization of herpes simplex virus type 2-infected guinea pigs using a recombinantly expressed herpes tegument protein-ribonucleotide reductase 2 (RR2; prime), followed by intravaginal treatment with the neurotropic adeno-associated virus type 8 expressing CXCL9, CXCL10, or CXCL11 T-cell-attracting chemokines to recruit T cells into the infected dorsal root ganglia (DRG) and vaginal mucosa (VM) (pull). We show that the RR2/CXCL11 prime-pull therapeutic vaccine strategy elicited a significant reduction in virus shedding in the vaginal mucosa and decreased the severity and frequency of recurrent genital herpes. This protection was associated with increased frequencies of functional tissue-resident (TRM cells) and effector (TEM cells) memory CD4+ and CD8+ T cells infiltrating latently infected DRG tissues and the healed regions of the vaginal mucosa. These findings shed light on the role of tissue-resident and effector memory CD4+ and CD8+ T cells in DRG tissues and the VM in protection against recurrent genital herpes and propose the prime-pull therapeutic vaccine strategy in combating genital herpes.

Modulation of plasmacytoid dendritic cells response in inflammation and autoimmunity

The discovery of toll-like receptors (TLRs) and the subsequent recognition that endogenous nucleic acids (NAs) could serve as TLR ligands have led to essential insights into mechanisms of healthy immune responses as well as pathogenic mechanisms relevant to systemic autoimmune and inflammatory diseases. In systemic lupus erythematosus, systemic sclerosis, and rheumatoid arthritis, NA-containing immune complexes serve as TLR ligands, with distinct implications depending on the additional immune stimuli available. Plasmacytoid dendritic cells (pDCs), the robust producers of type I interferon (IFN-I), are providing critical insights relevant to TLR-mediated healthy immune responses and tissue repair, as well as generation of inflammation, autoimmunity and fibrosis, processes central to the pathogenesis of many autoimmune diseases. In this review, we describe recent data characterizing the role of platelets and NA-binding chemokines in modulation of TLR signaling in pDCs, as well as implications for how the IFN-I products of pDCs contribute to the generation of inflammation and wound healing responses by monocyte/macrophages. Chemokine modulators of TLR-mediated B cell tolerance mechanisms and interactions between TLR signaling and metabolic pathways are also considered. The modulators of TLR signaling and their contribution to the pathogenesis of systemic autoimmune diseases suggest new opportunities for identification of novel therapeutic targets.

Noninvasive biomarkers for lupus nephritis

Lupus nephritis (LN) is one of the most severe clinical manifestations of systemic lupus erythematosus (SLE). Notably, the clinical manifestations of LN are not always consistent with the histopathological findings. Therefore, the diagnosis and activity monitoring of this disease are challenging and largely depend on invasive renal biopsy. Renal biopsy has side effects and is associated with the risk of bleeding and infection. There is a growing interest in the development of novel noninvasive biomarkers for LN. In this review, we summarize most of the LN biomarkers discovered so far by correlating current knowledge with future perspectives. These biomarkers fundamentally reflect the biological processes of kidney damage and repair during disease. Furthermore, this review highlights the role of urinary cell phenotype detection in the diagnosis, monitoring, and treatment of LN and summarizes the limitations and countermeasures of this test.

MDIC3: Matrix decomposition to infer cell-cell communication

Crosstalk among cells is vital for maintaining the biological function and intactness of systems. Most existing methods for investigating cell-cell communications are based on ligand-receptor (L-R) expression, and they focus on the study between two cells. Thus, the final communication inference results are particularly sensitive to the completeness and accuracy of the prior biological knowledge. Because existing L-R research focuses mainly on humans, most existing methods can only examine cell-cell communication for humans. As far as we know, there is currently no effective method to overcome this species limitation. Here, we propose MDIC3 (matrix decomposition to infer cell-cell communication), an unsupervised tool to investigate cell-cell communication in any species, and the results are not limited by specific L-R pairs or signaling pathways. By comparing it with existing methods for the inference of cell-cell communication, MDIC3 obtained better performance in both humans and mice.

Autoantibodies against the chemokine receptor 3 predict cardiovascular risk

BACKGROUND AND AIMS

Chronic inflammation and autoimmunity contribute to cardiovascular (CV) disease. Recently, autoantibodies (aAbs) against the CXC-motif-chemokine receptor 3 (CXCR3), a G protein-coupled receptor with a key role in atherosclerosis, have been identified. The role of anti-CXCR3 aAbs for CV risk and disease is unclear.

METHODS

Anti-CXCR3 aAbs were quantified by a commercially available enzyme-linked immunosorbent assay in 5000 participants (availability: 97.1%) of the population-based Gutenberg Health Study with extensive clinical phenotyping. Regression analyses were carried out to identify determinants of anti-CXCR3 aAbs and relevance for clinical outcome (i.e. all-cause mortality, cardiac death, heart failure, and major adverse cardiac events comprising incident coronary artery disease, myocardial infarction, and cardiac death). Last, immunization with CXCR3 and passive transfer of aAbs were performed in ApoE(-/-) mice for preclinical validation.

RESULTS

The analysis sample included 4195 individuals (48% female, mean age 55.5 ± 11 years) after exclusion of individuals with autoimmune disease, immunomodulatory medication, acute infection, and history of cancer. Independent of age, sex, renal function, and traditional CV risk factors, increasing concentrations of anti-CXCR3 aAbs translated into higher intima-media thickness, left ventricular mass, and N-terminal pro-B-type natriuretic peptide. Adjusted for age and sex, anti-CXCR3 aAbs above the 75th percentile predicted all-cause death [hazard ratio (HR) (95% confidence interval) 1.25 (1.02, 1.52), P = .029], driven by excess cardiac mortality [HR 2.51 (1.21, 5.22), P = .014]. A trend towards a higher risk for major adverse cardiac events [HR 1.42 (1.0, 2.0), P = .05] along with increased risk of incident heart failure [HR per standard deviation increase of anti-CXCR3 aAbs: 1.26 (1.02, 1.56), P = .03] may contribute to this observation. Targeted proteomics revealed a molecular signature of anti-CXCR3 aAbs reflecting immune cell activation and cytokine-cytokine receptor interactions associated with an ongoing T helper cell 1 response. Finally, ApoE(-/-) mice immunized against CXCR3 displayed increased anti-CXCR3 aAbs and exhibited a higher burden of atherosclerosis compared to non-immunized controls, correlating with concentrations of anti-CXCR3 aAbs in the passive transfer model.

CONCLUSIONS

In individuals free of autoimmune disease, anti-CXCR3 aAbs were abundant, related to CV end-organ damage, and predicted all-cause death as well as cardiac morbidity and mortality in conjunction with the acceleration of experimental atherosclerosis.

Regulatory T cells inhibit autoantigen-specific CD4+ T cell responses in lupus-prone NZB/W F1 mice

Introduction

Progressive loss of regulatory T cell (Treg)-mediated control over autoreactive effector T cells contributes to the development of systemic lupus erythematosus (SLE). Accordingly, we hypothesized that Treg may also have the capacity to suppress the activation of autoreactive CD4+ T cells that are considered to drive autoimmunity.

Methods

To investigate whether Treg are involved in the control of autoreactive CD4+ T cells, we depleted CD25+ Treg cells either in vivo or in vitro, or combined both approaches before antigen-specific stimulation with the SLE-associated autoantigen SmD1(83-119) in the NZB/W F1 mouse model either after immunization against SmD1(83-119) or during spontaneous disease development. Frequencies of autoantigen-specific CD4+ T cells were determined by flow cytometry using the activation marker CD154.

Results

Both in vitro and in vivo depletion of CD25+ Treg, respectively, increased the frequencies of detectable autoantigen-specific CD4+ T cells by approximately 50%. Notably, the combined in vivo and in vitro depletion of CD25+ Treg led almost to a doubling in their frequencies. Frequencies of autoantigen-specific CD4+ T cells were found to be lower in immunized haploidentical non-autoimmune strains and increased frequencies were detectable in unmanipulated NZB/W F1 mice with active disease. In vitro re-addition of CD25+ Treg after Treg depletion restored suppression of autoantigen-specific CD4+ T cell activation.

Discussion

These results suggest that the activation and expansion of autoantigen-specific CD4+ T cells are partly controlled by Treg in murine lupus. Depletion of Treg therefore can be a useful approach to increase the detectability of autoantigen-specific CD4+ T cells allowing their detailed characterization including lineage determination and epitope mapping and their sufficient ex vivo isolation for cell culture.

Addition of formaldehyde releaser imidazolidinyl urea and MOPS buffer to urine samples enables delayed processing for flow cytometric analysis of urinary cells: A simple, two step conservation method of urinary cells for flow cytometry

INTRODUCTION

Kidney diseases are a major health concern worldwide. Currently there is a large unmet need for novel biomarkers to non-invasively diagnose and monitor kidney diseases. Urinary cells are promising biomarkers and their analysis by flow cytometry has demonstrated its utility in diverse clinical settings. However, up to date this methodology depends on fresh samples, as cellular event counts and the signal-to-noise-ratio deter over time. Here we developed an easy-to-use two-step preservation method for conservation of urine samples for subsequent flow cytometry.

METHODS

The protocol utilizes a combination of the formaldehyde releasing agent imidazolidinyl urea (IU) and MOPS buffer, leading to gentle fixation of urinary cells.

RESULTS

The preservation method increases acceptable storing time of urine samples from several hours to up to 6 days. Cellular event counts and staining properties of cells remain comparable to fresh untreated samples.

OUTLOOK

The hereby presented preservation method facilitates future investigations on flow cytometry of urinary cells as potential biomarkers and may enable broad implementation in clinical practice.

Role of the transcription factor Fli-1 on the CXCL10/CXCR3 Axis

The transcription factor Fli-1, a member of the ETS family of transcription factors, is implicated in the pathogenesis of lupus disease. Reduced Fli-1 expression in lupus mice leads to decreased renal Cxcl10 mRNA levels and renal infiltrating CXCR3+ T cells that parallels reduced renal inflammatory cell infiltration and renal damage. Inflammatory chemokine CXCL10 is critical for attracting inflammatory cells expressing the chemokine receptor CXCR3. The CXCL10/CXCR3 axis plays a role in the pathogenesis of various inflammatory diseases including lupus. Our data here demonstrate that renal CXCL10 protein levels are significantly lower in Fli-1 heterozygous MRL/lpr mice compared to wild-type MRL/lpr mice. Knockdown of Fli-1 significantly reduced CXCL10 secretion in mouse and human endothelial cells, and human mesangial cells, upon LPS or TNFα stimulation. The Fli-1 inhibitor, Camptothecin, significantly reduced CXCL10 production in human monocyte cells upon interferon stimulation. Four putative Ets binding sites in the Cxcl10 promoter showed significant enrichment for FLI-1; however, FLI-1 did not directly drive transcription from the human or mouse promoters, suggesting FLI-1 may regulate CXCL10 expression indirectly. Our results also suggest that the DNA binding domain of FLI-1 is necessary for regulation of human hCXCR3 promotor activity in human T cells and interactions with co-activators. Together, these results support a role for FLI-1 in modulating the CXCL10-CXCR3 axis by directly or indirectly regulating the expression of both genes to impact lupus disease development. Signaling pathways or drugs that reduce FLI-1 expression may offer novel approaches to lupus treatment.

Decipher the Immunopathological Mechanisms and Set Up Potential Therapeutic Strategies for Patients with Lupus Nephritis

Lupus nephritis (LN) is one of the most severe complications in patients with systemic lupus erythematosus (SLE). Traditionally, LN is regarded as an immune complex (IC) deposition disease led by dsDNA-anti-dsDNA-complement interactions in the subendothelial and/or subepithelial basement membrane of glomeruli to cause inflammation. The activated complements in the IC act as chemoattractants to chemically attract both innate and adaptive immune cells to the kidney tissues, causing inflammatory reactions. However, recent investigations have unveiled that not only the infiltrating immune-related cells, but resident kidney cells, including glomerular mesangial cells, podocytes, macrophage-like cells, tubular epithelial cells and endothelial cells, may also actively participate in the inflammatory and immunological reactions in the kidney. Furthermore, the adaptive immune cells that are infiltrated are genetically restricted to autoimmune predilection. The autoantibodies commonly found in SLE, including anti-dsDNA, are cross-reacting with not only a broad spectrum of chromatin substances, but also extracellular matrix components, including α-actinin, annexin II, laminin, collagen III and IV, and heparan sulfate proteoglycan. Besides, the glycosylation on the Fab portion of IgG anti-dsDNA antibodies can also affect the pathogenic properties of the autoantibodies in that α-2,6-sialylation alleviates, whereas fucosylation aggravates their nephritogenic activity. Some of the coexisting autoantibodies, including anti-cardiolipin, anti-C1q, anti-ribosomal P autoantibodies, may also enhance the pathogenic role of anti-dsDNA antibodies. In clinical practice, the identification of useful biomarkers for diagnosing, monitoring, and following up on LN is quite important for its treatments. The development of a more specific therapeutic strategy to target the pathogenic factors of LN is also critical. We will discuss these issues in detail in the present article.

Identification of proteinase 3 autoreactive CD4+T cells and their T-cell receptor repertoires in antineutrophil cytoplasmic antibody-associated vasculitis

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is an autoimmune disease involving autoreactivity to proteinase 3 (PR3) as demonstrated by presence of ANCAs. While autoantibodies are screened for diagnosis, autoreactive T cells and their features are less well-studied. Here, we investigated PR3-specific CD4+T cell responses and features of autoreactive T cells in patients with PR3-AAV, using a cohort of 72 patients with either active or inactive disease. Autoreactive PR3-specific CD4+T cells producing interferon γ in response to protein stimulation were found to express the G-protein coupled receptor 56 (GPR56), a cell surface marker that distinguishes T cells with cytotoxic capacity. GPR56+CD4+T cells were significantly more prominent in the blood of patients with inactive as compared to active disease, suggesting that these cells were affected by immunosuppression and/or that they migrated from the circulation to sites of organ involvement. Indeed, GPR56+CD4+T cells were identified in T-cell infiltrates of affected kidneys and an association with immunosuppressive therapy was found. Moreover, distinct TCR gene segment usage and shared (public) T cell clones were found for the PR3-reactive TCRs. Shared T cell clones were found in different patients with AAV carrying the disease-associated HLA-DP allele, demonstrating convergence of the autoreactive T cell repertoire. Thus, we identified a CD4+T cell signature in blood and in affected kidneys that display PR3 autoreactivity and associates with T cell cytotoxicity. Our data provide a basis for novel rationales for both immune monitoring and future therapeutic intervention in PR3-AAV.

Glucocorticoids target the CXCL9/CXCL10-CXCR3 axis and confer protection against immune-mediated kidney injury

Glucocorticoids remain a cornerstone of therapeutic regimes for autoimmune and chronic inflammatory diseases - for example, in different forms of crescentic glomerulonephritis - because of their rapid antiinflammatory effects, low cost, and wide availability. Despite their routine use for decades, the underlying cellular mechanisms by which steroids exert their therapeutic effects need to be fully elucidated. Here, we demonstrate that high-dose steroid treatment rapidly reduced the number of proinflammatory CXCR3+CD4+ T cells in the kidney by combining high-dimensional single-cell and morphological analyses of kidney biopsies from patients with antineutrophil cytoplasmic antibody-associated (ANCA-associated) crescentic glomerulonephritis. Using an experimental model of crescentic glomerulonephritis, we show that the steroid-induced decrease in renal CD4+ T cells is a consequence of reduced T cell recruitment, which is associated with an ameliorated disease course. Mechanistic in vivo and in vitro studies revealed that steroids act directly on renal tissue cells, such as tubular epithelial cells, but not on T cells, which resulted in an abolished renal expression of CXCL9 and CXCL10 as well as in the prevention of CXCR3+CD4+ T cell recruitment to the inflamed kidneys. Thus, we identified the CXCL9/CXCL10-CXCR3 axis as a previously unrecognized cellular and molecular target of glucocorticoids providing protection from immune-mediated pathology.

Urinary T Cells Identify Renal ANCA-Associated Vasculitis and Predict Prognosis: a proof of concept study

Introduction

Necrotizing crescentic glomerulonephritis is a major contributor to morbidity and mortality in Antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV). Because therapy relies on immunosuppressive agents with potentially severe adverse effects, a reliable noninvasive biomarker of disease activity is needed to guide treatment.

Methods

We used flow cytometry to quantify T cell subsets in blood and urine samples from 95 patients with AAV and 8 controls to evaluate their biomarker characteristics. These were compared to soluble markers, monocyte chemoattractant protein-1 (MCP-1), soluble CD163 (sCD163), soluble CD25 (sCD25), and complement C5a (C5a), measured using multiplex analysis. Available kidney biopsies (n = 21) were classified according to Berden.

Results

Patients with active renal AAV (rAAV) showed significantly higher urinary cell counts than those in remission, or those with extrarenal manifestation, or healthy controls. Urinary T cells showed robust discrimination of disease activity with superior performance compared to MCP-1 and sCD163. Patients whose kidney biopsies had been classified as "crescentic" according to Berden classification showed higher urinary T cell counts. Discordant regulatory T cells (T_reg) proportions and CD4⁺/CD8⁺ ratio in blood and urine suggested that urinary cells reflect tissue migration rather than mere micro-bleeding. Furthermore, urinary T_reg and T helper cells (T_H17) patterns were associated with clinical response and risk of renal relapse.

Conclusion

Urinary T cells reflect the renal inflammatory milieu in AAV and provide further insights into the pathogenesis of this chronic condition. Their promising potential as noninvasive diagnostic and prognostic biomarkers deserves further exploitation.

Sex bias in lymphocytes: Implications for autoimmune diseases

Autoimmune diseases are characterized by a significant sex dimorphism, with women showing increased susceptibility to disease. This is, at least in part, due to sex-dependent differences in the immune system that are influenced by the complex interplay between sex hormones and sex chromosomes, with contribution from sociological factors, diet and gut microbiota. Sex differences are evident in the number and function of lymphocyte populations. Women mount a stronger pro-inflammatory response than males, with increased lymphocyte proliferation, activation and pro-inflammatory cytokine production, whereas men display expanded regulatory cell subsets. Ageing alters the immune landscape of men and women in differing ways, resulting in changes in autoimmune disease susceptibility. Here we review the current literature on sex differences in lymphocyte function, the factors that influence this, and the implications for autoimmune disease. We propose that improved understanding of sex bias in lymphocyte function can provide sex-specific tailoring of treatment strategies for better management of autoimmune diseases.

Dysregulation and chronicity of pathogenic T cell responses in the pre-diseased stage of lupus

In the normal immune system, T cell activation is tightly regulated and controlled at several levels to ensure that activation occurs in the right context to prevent the development of pathologic conditions such as autoimmunity or other harmful immune responses. CD4+FoxP3+ regulatory T cells (Treg) are crucial for the regulation of T cell responses in the peripheral lymphatic organs and thus for the prevention and control of autoimmunity. In systemic lupus erythematosus (SLE), a prototypic systemic autoimmune disease with complex etiology, a disbalance between Treg and pathogenic effector/memory CD4+ T cells develops during disease progression indicating that gradual loss of control over T cell activation is an important event in the immune pathogenesis. This progressive failure to adequately regulate the activation of autoreactive T cells facilitates chronic activation and effector/memory differentiation of pathogenic T cells, which are considered to contribute significantly to the induction and perpetuation of autoimmune processes and tissue inflammation in SLE. However, in particular in humans, little is known about the factors which drive the escape from immune regulation and the chronicity of pathogenic T cell responses in an early stage of autoimmune disease when clinical symptoms are still unapparent. Here we briefly summarize important findings and discuss current views and models on the mechanisms related to the dysregulation of T cell responses which promotes chronicity and pathogenic memory differentiation with a focus on the early stage of disease in lupus-prone individuals.

Identification and analysis of the predictive urinary exosomal miR-195-5p in lupus nephritis based on renal miRNA-mRNA co-expression network

OBJECTIVE

Lupus nephritis (LN) is the main complication of systemic lupus erythematosus (SLE), causing huge financial burden and poor quality of life. Due to the low compliance of renal biopsy, we aim to find a non-invasive biomarker of LN to optimize its predictive, preventive, and personalized medical service or management.

METHOD

Herein, we provided a bioinformatic screen combined clinical validation strategy for rapidly mining exosomal miRNAs for LN diagnosis and management. We screened out differentially expressed miRNAs (DEMs) and differentially expressed mRNAs (DEGs) in LN database and performed a miRNA-mRNA integrated analysis to select out reliable changed miRNAs in LN tissues by using R and Cytoscape. Urinary exosomes were collected by ultracentrifugation and analyzed by nano-tracking analysis and western blotting. Detection of aquaporin-2 showed the tubular source of urinary exosomes. Urinary exosomal miRNAs were detected by RT-qPCR and the target of miR-195-5p was verified by using bioinformatic, dual-luciferase, and western blotting.

RESULT

15 miRNAs and their 60 target mRNAs were contained in miRNA-mRNA integrated map. Bioinformatic analysis showed these miRNAs were involved in various cellular biological process. Exosomal miR-195-5p, miR-25-3p, miR-429, and miR-218-5p were verified in a small clinical group (n = 47). Urinary exosomal miR-195-5p, miR-25-3p, and miR-429 were downregulated in patients and miR-195-5p could recognize LN patients from SLE with good sensitivity and specificity, showing good potential in LN disease monitoring and diagnosis.

CONCLUSION

We analyzed and obtained a series of differential miRNAs in LN kidney tissues and suggested that urinary exosomal miR-195-5p could serve as a novel biomarker in LN. Further, miR-195-5p-CXCL10 axis could be a therapeutic target of LN.

Evolution, Expression and Functional Analysis of CXCR3 in Neuronal and Cardiovascular Diseases: A Narrative Review

Chemokines form a sophisticated communication network wherein they maneuver the spatiotemporal migration of immune cells across a system. These chemical messengers are recognized by chemokine receptors, which can trigger a cascade of reactions upon binding to its respective ligand. CXC chemokine receptor 3 (CXCR3) is a transmembrane G protein-coupled receptor, which can selectively bind to CXCL9, CXCL10, and CXCL11. CXCR3 is predominantly expressed on immune cells, including activated T lymphocytes and natural killer cells. It thus plays a crucial role in immunological processes like homing of effector cells to infection sites and for pathogen clearance. Additionally, it is expressed on several cell types of the central nervous system and cardiovascular system, due to which it has been implicated in several central nervous system disorders, including Alzheimer's disease, multiple sclerosis, dengue viral disease, and glioblastoma, as well as cardiovascular diseases like atherosclerosis, Chronic Chagas cardiomyopathy, and hypertension. This review provides a narrative description of the evolution, structure, function, and expression of CXCR3 and its corresponding ligands in mammals and zebrafish and the association of CXCR3 receptors with cardiovascular and neuronal disorders. Unraveling the mechanisms underlying the connection of CXCR3 and disease could help researchers investigate the potential of CXCR3 as a biomarker for early diagnosis and as a therapeutic target for pharmacological intervention, along with developing robust zebrafish disease models.

Th17 and Th1 cells in systemic lupus erythematosus with focus on lupus nephritis

Systemic lupus erythematosus (SLE) is a complex autoimmune disease characterized by T cells imbalance. Indeed, a correlation between levels of Th17 cells and disease activity has been reported. Our work aimed to study the functional association of subpopulations of Th cells and SLE with (lupus nephritis, LN) or without (lupus erythematosus, LE) renal involvement in Tunisian patients through the detection of intracellular cytokines and surface marker expression. The IL23R and RORC mRNA expression levels were evaluated. The level of Th17 and Th1 cells was higher in LE and LN patients compared to healthy controls (HC) (p = 0.007 and p = 0.018, respectively), while Th1/17 cells were increased only in LN patients compared to HC (p = 0.011). However, no significant difference was described in the mRNA expression levels of RORC and IL-23R between SLE and HC. Our findings suggest that the Th1/Th17 differentiation mechanisms are altered in SLE and that this imbalance should have an important influence on the development and severity of the disease.

The X in seX-biased immunity and autoimmune rheumatic disease

Sexual dimorphism in the composition and function of the human immune system has important clinical implications, as males and females differ in their susceptibility to infectious diseases, cancers, and especially systemic autoimmune rheumatic diseases. Both sex hormones and the X chromosome, which bears a number of immune-related genes, play critical roles in establishing the molecular basis for the observed sex differences in immune function and dysfunction. Here, we review our current understanding of sex differences in immune composition and function in health and disease, with a specific focus on the contribution of the X chromosome to the striking female bias of three autoimmune rheumatic diseases.

Gut dysbiosis is associated with acceleration of lupus nephritis

The gut microbiota (GM) exerts a strong influence over the host immune system and dysbiosis of this microbial community can affect the clinical phenotype in chronic inflammatory conditions. To explore the role of the GM in lupus nephritis, we colonized NZM2410 mice with Segmented Filamentous Bacteria (SFB). Gut colonization with SFB was associated with worsening glomerulonephritis, glomerular and tubular immune complex deposition and interstitial inflammation compared to NZM2410 mice free of SFB. With SFB colonization mice experienced an increase in small intestinal lamina propria Th17 cells and group 3 innate lymphoid cells (ILC3s). However, although serum IL-17A expression was elevated in these mice, Th17 cells and ILC3s were not detected in the inflammatory infiltrate in the kidney. In contrast, serum and kidney tissue expression of the macrophage chemoattractants MCP-1 and CXCL1 were significantly elevated in SFB colonized mice. Furthermore, kidney infiltrating F4/80+CD206+M2-like macrophages were significantly increased in these mice. Evidence of increased gut permeability or "leakiness" was also detected in SFB colonized mice. Finally, the intestinal microbiome of SFB colonized mice at 15 and 30 weeks of age exhibited dysbiosis when compared to uncolonized mice at the same time points. Both microbial relative abundance as well as biodiversity of colonized mice was found to be altered. Collectively, SFB gut colonization in the NZM2410 mouse exacerbates kidney disease, promotes kidney M2-like macrophage infiltration and overall intestinal microbiota dysbiosis.

What can we learn from DNA methylation studies in lupus?

During the past twenty years, a wide range of studies have established the existence of epigenetic alterations, particularly DNA methylation changes, in lupus. Epigenetic changes might have different contributions in children-onset versus adult-onset lupus. DNA methylation alterations have been identified and characterized in relation to disease activity and damage, different lupus subtypes and responses to drugs. However, to date there has been no practical application of these findings in the clinical milieu. In this article, we provide a review of key studies showing the relationship between DNA methylation and the many clinical aspects related to lupus. We also propose several options, in relation to the range of methodological developments and experimental design, that could optimize these findings and make them amenable for use in clinical practice.

Urinary Cellular Profile as a Biomarker for Lupus Nephritis

BACKGROUND/OBJECTIVE

A search for the ideal biomarker for lupus nephritis (LN) is still underway, one that can be used for early detection and correlate with the class and activity of LN. Urine is normally devoid of leukocytes; however, it has been observed that macrophages and T lymphocytes are routinely present in the urine of LN patients and those with other proliferative renal diseases. This provides the idea for their potential use as biomarkers for proliferative LN. Here, we measured the urinary CD4+, CD8+ T lymphocytes, and CD14+ monocytes in patients with systemic lupus erythematosus (SLE) as potential biomarkers for LN.

METHODS

A longitudinal case-control study included 30 SLE patients with LN, 30 SLE patients without past or current LN, and 20 healthy subjects as a control group. The flow cytometric analysis was done using BD FACS Calibur multiparameter flow cytometer equipped with BD CellQuest Pro software for data analysis.

RESULTS

CD14+ cells were the most abundant cells in the urine of LN patients. The mean numbers of urinary CD8+, CD4+, and CD14+ cells/mL were significantly higher in patients with LN than in those without. The cell counts correlated significantly with proteinuria. Urinary CD14+ cells seem to occur in much higher counts in class IV than class III LN.

CONCLUSIONS

Urinary CD8+, CD4+, and CD14+ cells are highly sensitive and specific markers for detecting proliferative LN. A low CD4:CD8 ratio provides a further clue. Urinary CD14 cell counts may be a potential biomarker to differentiate between the different classes of proliferative LN.

C-X-C Motif Chemokine Ligand 9 and Its CXCR3 Receptor Are the Salt and Pepper for T Cells Trafficking in a Mouse Model of Gaucher Disease

Gaucher disease is a lysosomal storage disease, which happens due to mutations in GBA1/Gba1 that encodes the enzyme termed as lysosomal acid β-glucosidase. The major function of this enzyme is to catalyze glucosylceramide (GC) into glucose and ceramide. The deficiency of this enzyme and resultant abnormal accumulation of GC cause altered function of several of the innate and adaptive immune cells. For example, augmented infiltration of T cells contributes to the increased production of pro-inflammatory cytokines, (e.g., IFNγ, TNFα, IL6, IL12p40, IL12p70, IL23, and IL17A/F). This leads to tissue damage in a genetic mouse model (Gba1^9V/-) of Gaucher disease. The cellular mechanism(s) by which increased tissue infiltration of T cells occurs in this disease is not fully understood. Here, we delineate role of the CXCR3 receptor and its exogenous C-X-C motif chemokine ligand 9 (CXCL9) in induction of increased tissue recruitment of CD4⁺ T and CD8⁺ T cells in Gaucher disease. Intracellular FACS staining of macrophages (Mϕs) and dendritic cells (DCs) from Gba1^9V/- mice showed elevated production of CXCL9. Purified CD4⁺ T cells and the CD8⁺ T cells from Gba1^9V/- mice showed increased expression of CXCR3. Ex vivo and in vivo chemotaxis experiments showed CXCL9 involvement in the recruitment of Gba1^9V/- T cells. Furthermore, antibody blockade of the CXCL9 receptor (CXCR3) on T cells caused marked reduction in CXCL9- mediated chemotaxis of T cells in Gba1^9V/- mice. These data implicate abnormalities of the CXCL9-CXCR3 axis leading to enhanced tissue recruitment of T cells in Gaucher disease. Such results provide a rationale for blockade of the CXCL9/CXCR3 axis as potential new therapeutic targets for the treatment of inflammation in Gaucher disease.

A Novel Long Noncoding RNA lincRNA00892 Activates CD4+ T Cells in Systemic Lupus Erythematosus by Regulating CD40L

Objective: The mechanism of CD4⁺ T-cell dysfunction in systemic lupus erythematosus (SLE) has not been fully understood. Increasing evidence show that long noncoding RNAs (lncRNAs) can regulate immune responses and take part in some autoimmune diseases, while little is known about the lncRNA expression and function in CD4⁺ T of SLE. Here, we aimed to detect the expression profile of lncRNAs in lupus CD4⁺ T cells and explore the mechanism that how lincRNA00892 in CD4⁺ T cells is involved in the pathogenesis of SLE. Methods: The expression profiles of lncRNAs and mRNAs in CD4⁺ T cells from SLE patients and healthy controls were detected by microarray. LincRNA00892 and CD40L were chosen for validation by quantitative real-time PCR (qRT-PCR). Coexpression network was conducted to predict the potential target genes of lincRNA00892. Then lincRNA00892 was overexpressed in normal CD4⁺ T cells via lentivirus transfection. The expression of lincRNA00892 was detected by qRT-PCR. The expression of CD40L was detected by qRT-PCR, western blotting, and flow cytometry, respectively. The expression of CD69 and CD23 was measured by flow cytometry. The secretion of IgG was determined by enzyme-linked immunosorbent assay (ELISA). The proteins targeted by lincRNA00892 were measured by RNA pulldown and subsequent mass spectrometry (MS). The interaction between heterogeneous nuclear ribonucleoprotein K (hnRNP K) and lincRNA00892 or CD40L was detected by RNA immunoprecipitation (RIP) assay. Results: A total of 1887 lncRNAs and 3375 mRNAs were found to be aberrantly expressed in CD4⁺ T cells of SLE patients compared to healthy controls. LincRNA00892 and CD40L were confirmed to be upregulated in CD4⁺ T cells of SLE patients by qRT-PCR. The lncRNA-mRNA coexpression network analysis indicated that CD40L was a potential target of lincRNA00892. Overexpression of lincRNA00892 enhanced CD40L protein levels while exerting little influence on CD40L mRNA levels in CD4⁺ T cells. In addition, lincRNA00892 could induce the activation of CD4⁺ T cells. Furthermore, lincRNA00892 led to the activation of B cells and subsequent secretion of IgG in a CD4⁺ T-cell-dependent manner. Finally, hnRNP K was found to be among the proteins pulled down by lincRNA00892, and hnRNP K could bind to lincRNA00892 or CD40L directly. Conclusion: Our results showed that the lncRNA expression profile was altered in CD4⁺ T cells of SLE. LincRNA00892 possibly contributed to the pathogenesis of SLE by targeting hnRNP K and subsequently upregulating CD40L expression to activate CD4⁺ T and B cells. These provided us a potential target for further mechanistic studies of SLE pathogenesis.

The lupus nephritis management renaissance

Over the past year, and for the first time ever, the US Food and Drug Administration approved 2 drugs specifically for the treatment of lupus nephritis (LN). As the lupus community works toward understanding how to best use these new therapies, it is also an ideal time to begin to rethink the overall management strategy of LN. In addition to new drugs, this must include how to use kidney biopsies for management and not just diagnosis, how molecular technologies can be applied to interrogate biopsies and how such data can impact management, and how to incorporate LN biomarkers into management paradigms. Herein, we will review new developments in these areas of LN and put them into perspective for disease management now and in the future.

The Power of Systems Biology: Insights on Lupus Nephritis from the Accelerating Medicines Partnership

The Accelerating Medicines Partnership (AMP) SLE Network united resources from academic centers, government, nonprofit, and industry to accelerate discovery in lupus nephritis (LN). The AMP SLE Network developed a set of protocols for high-throughput analyses to systematically study kidney tissue, urine, and blood in LN. This article summarizes approaches and results from phase 1 of AMP SLE Network effort, including single cell RNA-seq analysis of LN kidney biopsies, cellular and proteomic studies of LN urine, and mass cytometry immunophenotyping of blood cells. This work provides a framework to guide studies of the clinical implications of active cellular/molecular pathways in LN.

An Enhanced Expression Level of CXCR3 on Tfh-like Cells from Lupus Skin Lesions Rather Than Lupus Peripheral Blood

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease, and the etiopathogenesis is unclear. Follicular helper T (Tfh) cells have been reported as an important pathogenic cell type in SLE. CXCR3 was reported to be decreased on lupus peripheral CD4⁺T cells. However, the expression level of CCR4, CCR6 and CXCR3 on Tfh-like cells in SLE peripheral blood and skin lesions is unknown. In this study, we detected CCR4, CCR6 and CXCR3 expression level on Tfh-like cells in the peripheral blood and skin lesions from SLE patients and normal controls (NCs). A decreased expression level of CXCR3 on Tfh-like cells was found in lupus peripheral blood. However, an increased CXCR3 expression was observed on total CD4⁺T and Tfh-like cells from lupus skin lesions. Moreover, we observed a higher expression level of CXCR3 in Tfh cells from human tonsils. These findings indicate that CXCR3 might help Tfh-like cells to migrate into the inflammatory sites.

PD-1 immunobiology in glomerulonephritis and renal cell carcinoma

BACKGROUND

Programmed cell death protein (PD)-1 receptors and ligands on immune cells and kidney parenchymal cells help maintain immunological homeostasis in the kidney. Dysregulated PD-1:PD-L1 binding interactions occur during the pathogenesis of glomerulopathies and renal cell carcinoma (RCC). The regulation of these molecules in the kidney is important to PD-1/PD-L1 immunotherapies that treat RCC and may induce glomerulopathies as an adverse event.

METHODS

The expression and function of PD-1 molecules on immune and kidney parenchymal cells were reviewed in the healthy kidney, PD-1 immunotherapy-induced nephrotoxicity, glomerulopathies and RCC.

RESULTS

PD-1 and/or its ligands are expressed on kidney macrophages, dendritic cells, lymphocytes, and renal proximal tubule epithelial cells. Vitamin D3, glutathione and AMP-activated protein kinase (AMPK) regulate hypoxic cell signals involved in the expression and function of PD-1 molecules. These pathways are altered in kidney disease and are linked to the production of vascular endothelial growth factor, erythropoietin, adiponectin, interleukin (IL)-18, IL-23, and chemokines that bind CXCR3, CXCR4, and/or CXCR7. These factors are differentially produced in glomerulonephritis and RCC and may be important biomarkers in patients that receive PD-1 therapies and/or develop glomerulonephritis as an adverse event CONCLUSION: By comparing the functions of the PD-1 axis in glomerulopathies and RCC, we identified similar chemokines involved in the recruitment of immune cells and distinct mediators in T cell differentiation. The expression and function of PD-1 and PD-1 ligands in diseased tissue and particularly on double-negative T cells and parenchymal kidney cells needs continued exploration. The possible regulation of the PD-1 axis by vitamin D3, glutathione and/or AMPK cell signals may be important to kidney disease and the PD-1 immunotherapeutic response.

T helper cell trafficking in autoimmune kidney diseases

CD4⁺ T cells are key drivers of autoimmune diseases, including crescentic GN. Many effector mechanisms employed by T cells to mediate renal damage and repair, such as local cytokine production, depend on their presence at the site of inflammation. Therefore, the mechanisms regulating the renal CD4⁺ T cell infiltrate are of central importance. From a conceptual point of view, there are four distinct factors that can regulate the abundance of T cells in the kidney: (1) T cell infiltration, (2) T cell proliferation, (3) T cell death and (4) T cell retention/egress. While a substantial amount of data on the recruitment of T cells to the kidneys in crescentic GN have accumulated over the last decade, the roles of T cell proliferation and death in the kidney in crescentic GN is less well characterized. However, the findings from the data available so far do not indicate a major role of these processes. More importantly, the molecular mechanisms underlying both egress and retention of T cells from/in peripheral tissues, such as the kidney, are unknown. Here, we review the current knowledge of mechanisms and functions of T cell migration in renal autoimmune diseases with a special focus on chemokines and their receptors.

T Cell Abnormalities in the Pathogenesis of Systemic Lupus Erythematosus: an Update

PURPOSE OF REVIEW

Systemic lupus erythematosus is a complex disease with broad spectrum of clinical manifestations. In addition to abnormal B cell responsive leading to autoantibody production, various T cells also play different roles in promoting systemic autoimmunity and end organ damage. We aim to provide a review on recent developments in how abnormalities in different T cells subsets contribute to systemic lupus erythematosus pathogenesis and how they inform the consideration of new promising therapeutics.

RECENT FINDINGS

Distinct subsets of T cells known as T follicular helper cells enable the production of pathogenic autoantibodies. Detailed understanding of the B cell helping T cell subsets should improve the performance of clinical trials targeting the cognate T:B cell interaction. CD8⁺ T cells play a role in peripheral tolerance and reversal of its exhausted phenotype could potentially alleviate both systemic autoimmunity and the risk of infection. Research on the abnormal lupus T cell signaling also leads to putative therapeutic targets able to restore interleukin-2 production and suppress the production of the pathogenic IL-17 cytokine. Recently, several studies have focused on dissecting T cell populations located in the damaged organs, aiming to target the pathogenic processes specific to each organ. Numerous T cell subsets play distinct roles in SLE pathogenesis and recent research in understanding abnormal signaling pathways, cellular metabolism, and environmental cues pave the way for the development of novel therapeutics.

Identification and characterization of antigen-specific CD4+ T cells targeting renally expressed antigens in human lupus nephritis with two independent methods

In the search for anti-renal autoreactivity in human lupus nephritis, we stimulated blood-derived CD4⁺ T cells from patients with systemic lupus erythematosus with various kidney lysates. Although only minor responses were detectable, these experiments led to the development of a search algorithm that combined autoantibody association with human lupus nephritis and target gene expression in inflamed kidneys. Applying this algorithm, five potential T cell antigens were identified. Blood-derived CD4⁺ T cells were then stimulated with these antigens. The cells were magnetically enriched prior to measurement with flow cytometry to facilitate the detection of very rare autoantigen-specific cells. The detected responses were dominated by IFN-γ-producing CD4⁺ T cells. Additionally, IL-10-producing CD4⁺ T cells were found. In a next step, T cell reactivity to each single antigen was independently evaluated with T cell libraries and [³H]-thymidine incorporation assays. Here, Vimentin and Annexin A2 were identified as the main T cell targets. Finally, Vimentin reactive T cells were also found in the urine of three patients with active disease. Overall, our experiments show that antigen-specific CD4⁺ T cells targeting renally expressed antigens arise in human lupus nephritis and correlate with disease activity and are mainly of the Th1 subset.

Clinical and histological significance of urinary CD11c+ macrophages in lupus nephritis

Background

Infiltration of immune cells into the kidney is one of the key features of lupus nephritis (LN). The presence of immune cells in the urine may be used as a non-invasive biomarker of LN. Here, we aimed to analyze the clinicopathologic significance of urinary CD11c⁺ macrophages in patients with LN.

Methods

The numbers and proportions of CD11c⁺ macrophages in the urine samples of patients with LN at the time of kidney biopsy were examined using flow cytometry. We also examined the association between the levels of urinary CD11c⁺ macrophages and the clinical and pathologic features of patients with LN.

Results

Compared with patients without LN or those with non-proliferative LN, patients with proliferative LN had significantly higher numbers and proportions of urinary CD11c⁺ macrophages, which were strongly correlated with the serum anti-dsDNA antibody titer. The numbers and proportions of urinary CD11c⁺ macrophages were significantly associated with the values of chronicity indices such as tubular atrophy and interstitial fibrosis. No significant relationships were found between the levels of urinary CD11c⁺ macrophages and the activity scores, degree of proteinuria, or lupus disease activity. Urinary CD11c⁺ macrophages were more abundant in patients who did not achieve renal response to induction treatment with immunosuppressants than in those who achieved complete or partial response. The receiver operating characteristic (ROC) curve analysis showed that the number of urinary CD11c⁺ macrophages was the most powerful predictor of renal response at 6 months (ROC-AUC = 1.00, p = 0.0004).

Conclusion

The urinary levels of CD11c⁺ macrophages were closely associated with the chronic pathologic changes of LN and renal response and may thus be used as a novel biomarker in LN.

Nuclear antigen-reactive CD4+ T cells expand in active systemic lupus erythematosus, produce effector cytokines, and invade the kidneys

Systemic lupus erythematosus is a systemic and chronic autoimmune disease characterized by loss of tolerance towards nuclear antigens with autoreactive CD4⁺ T cells implicated in disease pathogenesis. However, very little is known about their receptor specificity since the detection of human autoantigen specific CD4⁺ T cells has been extremely challenging. Here we present an analysis of CD4⁺ T cells reactive to nuclear antigens using two complementary methods: T cell libraries and antigen-reactive T cell enrichment. The frequencies of nuclear antigen specific CD4⁺ T cells correlated with disease severity. These autoreactive T cells produce effector cytokines such as interferon-γ, interleukin-17, and interleukin-10. Compared to blood, these cells were enriched in the urine of patients with active lupus nephritis, suggesting an infiltration of the inflamed kidneys. Thus, these previously unrecognized characteristics support a role for nuclear antigen-specific CD4⁺ T cells in systemic lupus erythematosus.

Role of chemokines, innate and adaptive immunity

Polycystic Kidney Disease (PKD) triggers a robust immune system response including changes in both innate and adaptive immunity. These changes involve immune cells (e.g., macrophages and T cells) as well as cytokines and chemokines (e.g., MCP-1) that regulate the production, differentiation, homing, and various functions of these cells. This review is focused on the role of the immune system and its associated factors in the pathogenesis of PKDs as evidenced by data from cell-based systems, animal models, and PKD patients. It also highlights relevant pre-clinical and clinical studies that point to specific immune system components as promising candidates for the development of prognostic biomarkers and therapeutic strategies to improve PKD outcomes.

Deep Phenotyping of Urinary Leukocytes by Mass Cytometry Reveals a Leukocyte Signature for Early and Non-Invasive Prediction of Response to Treatment in Active Lupus Nephritis

Non-invasive biomarkers are necessary for diagnosis and monitoring disease activity in lupus nephritis (LN) to circumvent risks and limitations of renal biopsies. To identify new non-invasive cellular biomarkers in the urine sediment of LN patients, which may reflect kidney inflammation and can be used to predict treatment outcome, we performed in-depth urinary immune cell profiling by mass cytometry. We established a mass cytometric workflow to comparatively analyze the cellular composition of urine and peripheral blood (PB) in 13 patients with systemic lupus erythematosus (SLE) with active, biopsy-proven proliferative LN. Clinical and laboratory data were collected at the time of sampling and 6 months after induction of therapy in order to evaluate the clinical response of each patient. Six patients with different acute inflammatory renal diseases were included as comparison group. Leukocyte phenotypes and composition differed significantly between urine and paired PB samples. In urine, neutrophils and monocytes/macrophages were identified as the most prominent cell populations comprising together about 30%–83% of nucleated cells, while T and B lymphocytes, eosinophils, and natural killer (NK) cells were detectable at frequencies of <10% each. The majority of urinary T cells showed phenotypical characteristics of activated effector memory T cells (EM) as indicated by the co-expression of CD38 and CD69 – a phenotype that was not detectable in PB. Kidney inflammation was also reflected by tissue-imprinted macrophages, which phenotypically differed from PB monocytes by an increased expression of HLA-DR and CD11c. The presence of activated urinary T cells and macrophages could be used for differential diagnosis of proliferative LN forms and other renal pathologies. Most interestingly, the amount of EM in the urine sediment could be used as a biomarker to stratify LN patients in terms of response to induction therapy. Deep immunophenotypic profiling of urinary cells in LN allowed us to identify a signature of activated T cells and macrophages, which appear to reflect leukocytic infiltrates in the kidney. This explorative study has not only confirmed but also extended the knowledge about urinary cells as a future non-invasive biomarker platform for diagnosis and precision medicine in inflammatory renal diseases.

Ets Family Transcription Factor Fli-1 Promotes Leukocyte Recruitment and Production of IL-17A in the MRL/Lpr Mouse Model of Lupus Nephritis

The transcription factor Friend leukemia integration 1 (Fli-1) regulates the expression of numerous cytokines and chemokines and alters the progression of lupus nephritis in humans and in the MRL/MpJ-Fas^lpr (MRL/lpr) mouse model. Th17-mediated immune responses are notably important as they promote ongoing inflammation. The purpose of this study is to determine the impact of Fli-1 on expression of interleukin-17A (IL-17A) and the infiltration of immune cells into the kidney. IL-17A concentrations were measured by ELISA in sera collected from MRL/lpr Fli-1-heterozygotes (Fli-1^+/−) and MRL/lpr Fli-1^+/+ control littermates. Expression of IL-17A and related proinflammatory mediators was measured by real-time polymerase chain reaction (RT-PCR). Immunofluorescence staining was performed on renal tissue from MRL/lpr Fli-1^+/− and control littermates using anti-CD3, anti-CD4, and anti-IL-17A antibodies to detect Th17 cells and anti-CCL20 and anti-CD11b antibodies to identify CCL20⁺ monocytes. The expression of IL-17A in renal tissue was significantly reduced; this was accompanied by decreases in expression of IL-6, signal transducer and activator of transcription 3 (STAT3), and IL-1β. Likewise, we detected fewer CD3⁺IL-17⁺ and CD4⁺IL-17⁺ cells in renal tissue of MLR/lpr Fli-1^+/− mice and significantly fewer CCL20⁺CD11b⁺ monocytes. In conclusion, partial deletion of Fli-1 has a profound impact on IL-17A expression and on renal histopathology in the MRL/lpr mouse.

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.

Modulation of iron homeostasis with hepcidin ameliorates spontaneous murine lupus nephritis

Lupus nephritis is the end organ manifestation of systemic lupus erythematosus. Iron metabolism and its master regulator, hepcidin, are known to regulate cell proliferation and inflammation, but their direct role in the pathophysiology of lupus nephritis remains under-investigated. Exogenous hepcidin reduced the severity of lupus nephritis in MRL/lpr mice, a preclinical model of spontaneous systemic lupus erythematosus without worsening anemia of inflammation. Hepcidin treatment reduced renal iron accumulation, systemic and intrarenal cytokines, and renal immune cell infiltration, independent of glomerular immune complex deposits and circulating autoantibodies. Hepcidin increased renal H-ferritin (a ferroxidase), reduced expression of free iron dependent DNA synthesis enzymes, Ribonucleotide Reductase 1 and 2, and intra-renal macrophage proliferation. These findings were recapitulated in vitro upon treatment of macrophages with hepcidin and murine colony stimulation factor-1. Furthermore, hepcidin-treated macrophages secreted less IL-1β and IL-6 upon stimulation with the TLR3 agonist polyinosine-polycytidylic acid. Of clinical relevance, hepcidin reduced progression and severity of nephritis in old mice with established systemic autoimmunity and overt proteinuria, highlighting its therapeutic potential. Thus, our findings provide a proof-of-concept that targeting cellular iron metabolism with hepcidin represents a promising therapeutic strategy in lupus nephritis.

Urinary biomarkers in lupus nephritis

Systemic lupus erythematosus (SLE) is the prototypical autoimmune disease that can affect any organ of the body. Multiple mechanisms may contribute to the pathophysiology of systemic lupus, including failure to remove apoptotic bodies, hyperactivity of self-reactive B and T lymphocytes, abnormal exposure to autoantigens, and increased levels of B-cell stimulatory cytokines. The involvement of the kidney, called lupus nephritis (LN), during the course of the disease affects between 30% and 60% of adult SLE patients, and up to 70% of children. LN is an immune-mediated glomerulonephritis that is a common and serious finding in patients with SLE. Nowadays, renal biopsy is considered the gold standard for classifying LN, besides its degree of activity or chronicity. Nevertheless, renal biopsy lacks the ability to predict which patients will respond to immunosuppressive therapy and is a costly and risky procedure that is not practical in the monitoring of LN because serial repetitions would be necessary. Consequently, many serum and urinary biomarkers have been studied in SLE patients for the complementary study of LN, existing conventional biomarkers like proteinuria, protein/creatinine ratio in spot urine, 24 ​h urine proteinuria, creatinine clearance, among others and non-conventional biomarkers, like Monocyte chemoattractant protein-1 (MCP-1), have been correlated with the histological findings of the different types of LN. In this article, we review the advances in lupus nephritis urinary biomarkers. Such markers ideally should be capable of predicting early sub-clinical flares and could be used to follow response to therapy. In addition, some of these markers have been found to be involved in the pathogenesis of lupus nephritis.

Role of Chemokine (C-X-C Motif) Ligand 10 (CXCL10) in Renal Diseases

Chemokine C-X-C ligand 10 (CXCL10), also known as interferon-γ-inducible protein 10 (IP-10), exerts biological function mainly through binding to its specific receptor, CXCR3. Studies have shown that renal resident mesangial cells, renal tubular epithelial cells, podocytes, endothelial cells, and infiltrating inflammatory cells express CXCL10 and CXCR3 under inflammatory conditions. In the last few years, strong experimental and clinical evidence has indicated that CXCL10 is involved in the development of renal diseases through the chemoattraction of inflammatory cells and facilitation of cell growth and angiostatic effects. In addition, CXCL10 has been shown to be a significant biomarker of disease severity, and it can be used as a prognostic indicator for a variety of renal diseases, such as renal allograft dysfunction and lupus nephritis. In this review, we summarize the structures and biological functions of CXCL10 and CXCR3, focusing on the important role of CXCL10 in the pathogenesis of kidney disease, and provide a theoretical basis for CXCL10 as a potential biomarker and therapeutic target in human kidney disease.

Kidney transplant monitoring by urinary flow cytometry: Biomarker combination of T cells, renal tubular epithelial cells, and podocalyxin-positive cells detects rejection

Creatinine and proteinuria are used to monitor kidney transplant patients. However, renal biopsies are needed to diagnose renal graft rejection. Here, we assessed whether the quantification of different urinary cells would allow non-invasive detection of rejection. Urinary cell numbers of CD4⁺ and CD8⁺ T cells, monocytes/macrophages, tubular epithelial cells (TEC), and podocalyxin(PDX)-positive cells were determined using flow cytometry and were compared to biopsy results. Urine samples of 63 renal transplant patients were analyzed. Patients with transplant rejection had higher amounts of urinary T cells than controls; however, patients who showed worsening graft function without rejection had similar numbers of T cells. T cells correlated with histological findings (interstitial inflammation p = 0.0005, r = 0.70; tubulitis p = 0.006, r = 0.58). Combining the amount of urinary T cells and TEC, or T cells and PDX⁺ cells, yielded a significant segregation of patients with rejection from patients without rejection (all p < 0.01, area under the curve 0.89–0.91). Urinary cell populations analyzed by flow cytometry have the potential to introduce new monitoring methods for kidney transplant patients. The combination of urinary T cells, TEC, and PDX-positive cells may allow non-invasive detection of transplant rejection.

Design and application of single-cell RNA sequencing to study kidney immune cells in lupus nephritis

The immune mechanisms that cause tissue injury in lupus nephritis have been challenging to define. The advent of high-dimensional cellular analyses, such as single-cell RNA sequencing, has enabled detailed characterization of the cell populations present in small biopsy samples of kidney tissue. In parallel, the development of methods that cryopreserve kidney biopsy specimens in a manner that preserves intact, viable cells, has enabled the uniform analysis of tissue samples collected at multiple sites and across many geographic areas and demographic cohorts with high-dimensional platforms. The application of these methods to kidney biopsy samples from patients with lupus nephritis has begun to define the phenotypes of both infiltrating and resident immune cells, as well as parenchymal cells, present in nephritic kidneys. The detection of similar immune cell populations in urine suggests that it might be possible to non-invasively monitor immune activation in kidneys. Once applied to large patient cohorts, these high-dimensional studies might enable patient stratification according to patterns of immune cell activation in the kidney or identify disease features that can be used as surrogate measures of efficacy in clinical trials. Applied broadly across multiple inflammatory kidney diseases, these studies promise to enormously expand our understanding of renal inflammation in the next decade.

IL-2 Therapy Diminishes Renal Inflammation and the Activity of Kidney-Infiltrating CD4+ T Cells in Murine Lupus Nephritis

An acquired deficiency of interleukin-2 (IL-2) and related disturbances in regulatory T cell (Treg) homeostasis play an important role in the pathogenesis of systemic lupus erythematosus (SLE). Low-dose IL-2 therapy was shown to restore Treg homeostasis in patients with active SLE and its clinical efficacy is currently evaluated in clinical trials. Lupus nephritis (LN), a challenging organ manifestation in SLE, is characterized by the infiltration of pathogenic CD4+ T cells into the inflamed kidney. However, the role of the Treg-IL-2 axis in the pathogenesis of LN and the mode of action of IL-2 therapy in the inflamed kidneys are still poorly understood. Using the (NZB × NZW) F1 mouse model of SLE we studied whether intrarenal Treg are affected by a shortage of IL-2 in comparison with lymphatic organs and whether and how intrarenal T cells and renal inflammation can be influenced by IL-2 therapy. We found that intrarenal Treg show phenotypic signs that are reminiscent of IL-2 deprivation in parallel to a progressive hyperactivity of intrarenal conventional CD4+ T cells (Tcon). Short-term IL-2 treatment of mice with active LN induced an expansion the intrarenal Treg population whereas long-term IL-2 treatment reduced the activity and proliferation of intrarenal Tcon, which was accompanied by a clinical and histological amelioration of LN. The association of these immune pathologies with IL-2 deficiency and their reversibility by IL-2 therapy provides important rationales for an IL-2-based immunotherapy of LN.

When the balance is broken: X-linked gene dosage from two X chromosomes and female-biased autoimmunity

Women and men exhibit differences in innate and adaptive immunity, and women are more susceptible to numerous autoimmune disorders. Two or more X chromosomes increases the risk for some autoimmune diseases, and increased expression of some X-linked immune genes is frequently observed in female lymphocytes from autoimmune patients. Evidence from mouse models of autoimmunity also supports the idea that increased expression of X-linked genes is a feature of female-biased autoimmunity. Recent studies have begun to elucidate the correlation between abnormal X-chromosome inactivation (XCI), an essential mechanism female somatic cells use to equalize X-linked gene dosage between the sexes, and autoimmunity in lymphocytes. In this review, we highlight research describing overexpression of X-linked immunity-related genes and female-biased autoimmunity in both humans and mouse models, and make connections with our recent work elucidating lymphocyte-specific mechanisms of XCI maintenance that become altered in lupus patients.

The function of ncRNAs in rheumatic diseases

Rheumatic diseases are a group of chronic heterogeneous autoimmune disorders characterized by abnormal regulation of the innate and adaptive immune systems. Despite extensive efforts, the full spectrum of molecular factors that contribute to the pathogenesis of rheumatic diseases remains unclear. ncRNAs can govern gene expression at the transcriptional and post-transcriptional levels in multiple diseases. Recent studies have demonstrated an important role for ncRNAs, such as miRNAs and lncRNAs, in the development of immune cells and rheumatic diseases. Here, we focus on the epigenetic regulatory roles of ncRNAs in the pathogenesis of rheumatic diseases and as biomarkers of disease state.

Urinary biomarkers for lupus nephritis: the role of the vascular cell adhesion molecule-1

Renal involvement is one of the main complications of systemic lupus erythematosus, causing a significant impact on patients' morbidity and mortality. Renal biopsy is still the gold standard of diagnosis, but it has many limitations. In this sense, several recent studies aim to identify biomarkers that not only predict disease activity and renal histology, but also lead to earlier treatment. In previous studies, the soluble vascular cell adhesion molecule-1 measured in urine showed a strong association with the presence of lupus nephritis, with clinical and histological activity indexes of the disease and with more severe renal lesions. This paper reviews the main urinary biomarkers of lupus nephritis that have been studied, with special emphasis on vascular cell adhesion molecule-1 results.

HMGB1+ microparticles present in urine are hallmarks of nephritis in patients with systemic lupus erythematosus

Non-classical monocytes infiltrate the kidney parenchyma and participate in tissue damage in patients with lupus nephritis (LN). Circulating microparticles (MPs) seem to play critical roles in the activation of monocytes in systemic lupus erythematosus (SLE) patients. This study aims to characterize the phenotypes of MPs and monocyte subsets in LN patients and to determine their potential to discriminate between SLE patients with and without LN. Blood and urine samples from SLE patients were collected. In monocyte subsets from whole blood samples several phenotypic markers were evaluated. MPs were isolated from platelet-poor plasma and urine by centrifugation. This phenotypic marker characterization was performed using multiparametric flow cytometry. We observed that patients with active LN have lower counts of non-classical monocytes than do those without renal involvement. All monocyte subsets exhibited lower expression of CX3CR1 and ICAM-1 in LN than in patients without LN. High frequencies of MP-HMGB1⁺ and MP-HLA-DR⁺ were detected in circulation and urine of LN patients. Although MP-HMGB1⁺ , MP-HLA-DR⁺ , and MP-CX3CR1⁺ from urine were able to discriminate between patients with and without LN, only urinary MP-HMGB1⁺ were different between patients with active and inactive LN. Therefore, these vesicles may be useful as biomarkers of LN.

Urinary T cells correlate with rate of renal function loss in autosomal dominant polycystic kidney disease

Several innate immune response components were recognized as outcome predictors in autosomal dominant polycystic kidney disease (ADPKD) and their causative role in disease pathogenesis was confirmed in animal models. In contrast, the role of adaptive immunity in ADPKD remains relatively unexplored. Therefore, we evaluated T cell populations in kidney and urine of ADPKD patients using flow cytometry and confocal immunofluorescence microscopy approaches. These analyses revealed ADPKD-associated overall increases in the number of intrarenal CD4 and CD8 T cells that were associated with a loss of polarity in distribution between the cortex and medulla (higher in medulla vs. cortex in controls). Also, the urinary T cell-based index correlated moderately with renal function decline in a small cohort of ADPKD patients. Together, these data suggest that similar to innate immune responses, T cells participate in ADPKD pathogenesis. They also point to urinary T cells as a novel candidate marker of the disease activity in ADPKD.

Treatment with Methotrexate and Intravenous Cyclophosphamide Pulse Therapy Regulates the P-gp+CD4+ Cell-related Pathogenesis in a Representative Patient with Refractory Proliferative Lupus Nephritis

Diffuse proliferative lupus nephritis (DPLN) is a serious organ complication. Drug resistance correlates with P-glycoprotein (P-gp) expression on activated lymphocytes. We encountered a refractory DPLN patient with expansion of peripheral CD69/CXCR3-co-expressing P-gp⁺CD4⁺ cells producing IL-2 and IL-6. Treatment with high-dose corticosteroid combined with biweekly intravenous cyclophosphamide pulse therapy (IVCY) failed to reduce the population of activated P-gp⁺CD4⁺ cells or control the disease activity. Methotrexate (MTX) with monthly IVCY reduced activated P-gp⁺CD4⁺ cells and improved the clinical symptoms, resulting in long-term remission and tapering of corticosteroids. MTX-IVCY combination therapy, which down-regulates the activated P-gp⁺CD4⁺ cell-mediated disease activity, may be useful for the treatment of refractory DPLN.