Kidney-infiltrating T cells in murine lupus nephritis are metabolically and functionally exhausted

Animal models of lupus nephritis: the past, present and a future outlook

Lupus nephritis (LN) is the most severe end-organ pathology in Systemic Lupus Erythematosus (SLE). Research has enhanced our understanding of immune effectors and inflammatory pathways in LN. However, even with the best available therapy, the rate of complete remission for proliferative LN remains below 50%. A deeper understanding of the resistance or susceptibility of renal cells to injury during the progression of SLE is critical for identifying new targets and developing effective long-term therapies. The complex and heterogeneous nature of LN, combined with the limitations of clinical research, make it challenging to investigate the aetiology of this disease directly in patients. Hence, multiple murine models resembling SLE-driven nephritis are utilised to dissect LN's cellular and genetic mechanisms, identify therapeutic targets, and screen novel compounds. This review discusses commonly used spontaneous and inducible mouse models that have provided insights into pathogenic mechanisms and long-term maintenance therapies in LN.

Cordyceps protein alleviates renal injury by inhibiting T cell infiltration and Th1 cell differentiation in lupus nephritis mice

BACKGROUND

T cell infiltration and differentiation play a central part in the development of lupus nephritis (LN). Our prior research has indicated that protein, the primary active component of cordyceps (WCP), a traditional Chinese medicine, possesses properties that can enhance renal fibrosis and provide kidney protection. Nonetheless, the connection between WCP and T cell infiltration and differentiation in LN remains poorly understood.

OBJECTIVE

The objective of this research was to assess the immunomodulatory impacts of WCP in LN mice and elucidate the underlying mechanism through in vivo and in vitro investigations.

METHODS

To investigate the impact and mechanism of WCP in MRL/lpr lupus-prone mice, WCP (1.5 g/kg/d), Bailing capsules (BC, 0.75 g/kg/d), and saline in equivalent quantities were administered to the mice over a period of 8 weeks. The therapeutic effects, T cell infiltration and differentiation of WCP on MRL/lpr mice were verified through ELISA, Hematoxylin-eosin (H&E), Periodic Acid Schiff (PAS) staining, immunofluorescence, Luminex analysis and flow cytometry. The mechanism by which WCP alleviates LN was investigated using tissues of mice, T cells and Mouse Podocyte Clone-5 (MPC-5) cells by transcriptomics, Western blot (WB), and Real-time quantitative polymerase chain reaction (RT-qPCR).

RESULTS

We found that WCP improved LN in MRL/lpr mice by reducing urinary protein, creatinine, and serum auto antibodies, increasing complement 3 (C3) level, improving renal immunopathology and downregulating serum cytokines, including IFN-γ, IL-12, and RANTES. Notably, the infiltration of CD4+ and CD8+ T cells in the kidney was reduced by WCP. Similarly, the cell transwell co-culturation study showed that the WCP treated MPC-5 cells were weaker in inducing T cell migration. Consistent with this finding, our observations revealed that WCP could inhibit T cell-related chemokine expression in kidney and MPC-5 cells, as well as reduce the levels of TLR4, MYD88, phosphorylated-p38, phosphorylated-ERK, and phosphorylated-JNK. On the other hand, WCP was found to greatly inhibit the Th1 cells differentiation in vivo and in vitro. Cytokine-receptor induced Th1 cell differentiation pathway and PI3K-AKT pathway were the most enriched pathways based on differentially expressed genes (DEGs) enrichment analysis among different cell groups. Results from RT-qPCR and WB showed that WCP notably reduced the levels of IL-12, p-STAT4, IFN-γ, p-STAT1, p-PI3K, and p-AKT in T cells.

CONCLUSION

WCP demonstrated positive immunomodulatory effects on LN disease, by decreasing the T cells infiltration through TLR4/MYD88/MAPK signaling pathway and inhibiting Th1 cells differentiation via IL-12-STAT4 and IFN-γ-STAT1 pathways, in addition to the PI3K-AKT pathway.

IFNγ initiates TLR9-dependent autoimmune hepatitis in DNase II deficient mice

Patients with biallelic hypomorphic mutation in DNASE2 develop systemic autoinflammation and early-onset liver fibrosis. Prior studies showed that Dnase2 -/- Ifnar -/- double knockout (DKO) mice develop Type I IFN-independent liver inflammation, but immune mechanisms were unclear. We now show that DKO mice recapitulate many features of human autoimmune hepatitis (AIH), including periportal and interstitial inflammation and fibrosis and elevated ALT. Infiltrating cells include CD8+ tissue resident memory T cells, type I innate lymphoid cells, and inflammatory monocyte/macrophage cells that replace the Kupffer cell pool. Importantly, TLR9 expression by bone marrow-derived cells is required for the the development of AIH. TLR9 is highly expressed by inflammatory myeloid cells but not long-lived Kupffer cells. Furthermore, the initial recruitment of TLR9 expressing monocytes and subsequent activation of lymphocytes requires IFNγ signaling. These findings highlight a critical role of feed forward loop between TLR9 expressing monocyte-lineage cells and IFNg producing lymphocytes in autoimmune hepatitis.

Moesin deficiency leads to lupus-like nephritis with accumulation of CXCL13-producing patrolling monocytes

Moesin is a member of the ezrin-radixin-moesin (ERM) family of proteins that link plasma membrane proteins to the cortical cytoskeleton and thus regulate diverse cellular processes. Mutations in the human moesin gene cause a primary immunodeficiency called X-linked moesin-associated immunodeficiency (X-MAID), which may be complicated by an autoimmune phenotype with kidney involvement. We previously reported that moesin-deficient mice exhibit lymphopenia similar to that of X-MAID and develop a lupus-like autoimmune phenotype with age. However, the mechanism through which moesin defects cause kidney pathology remains obscure. Here, we characterized immune cell infiltration and chemokine expression in the kidney of moesin-deficient mice. We found accumulation of CD4+ T and CD11b+ myeloid cells and high expression of CXCL13, whose upregulation was detected before the onset of overt nephritis. CD4+ T cell population contained IFN-γ-producing effectors and expressed the CXCL13 receptor CXCR5. Among myeloid cells, Ly6Clo patrolling monocytes and MHCIIlo macrophages markedly accumulated in moesin-deficient kidneys and expressed high CXCL13 levels, implicating the CXCL13-CXCR5 axis in nephritis development. Functionally, Ly6Clo monocytes from moesin-deficient mice showed reduced migration toward sphingosine 1-phosphate. These findings suggest that moesin plays a role in regulating patrolling monocyte homeostasis, and that its defects lead to nephritis associated with accumulation of CXCL13-producing monocytes and macrophages.

CD8 T cells induce the peritubular capillary rarefaction during AKI to CKD transition

Acute kidney injury (AKI) transformed to chronic kidney disease (CKD) is a critical clinical issue characterized by tubulointerstitial inflammation (TII) and fibrosis. However, the exact mechanism remains largely unclear. In this study, we used single-cell RNA sequencing (scRNA-seq) to obtain a high-resolution profile of T cells in AKI to CKD transition with a mice model of unilateral ischemia-reperfusion injury (uIRI). We found that T cells accumulated increasingly with the progression of AKI to CKD, which was categorized into 9 clusters. A notably increased proportion of CD8 T cells via self-proliferation occurred in the early stage of AKI was identified. Further study revealed that the CD8 T cells were recruited through CXCL16-CXCR6 pathway mediated by macrophages. Notably, CD8 T cells induced endothelial cell apoptosis via Fas ligand-Fas signaling. Consistently, increased CD8 T cell infiltration accompanied with peritubular capillaries (PTCs) rarefaction was observed in uIRI mice. More impressively, the loss of PTCs and renal fibrosis was remarkably ameliorated after the elimination of CD8 T cells. In summary, our study provides a novel insight into the role of CD8 T cells in the transition from AKI to CKD via induction of PTCs rarefaction, which could suggest a promising therapeutic target for AKI.

Alterations in genes associated with cytosolic RNA sensing in whole blood are associated with coronary microvascular disease in SLE

Systemic lupus erythematosus (SLE) patients are 90% women and over three times more likely to die of cardiovascular disease than women in the general population. Chest pain with no obstructive cardiac disease is associated with coronary microvascular disease (CMD), where narrowing of the small blood vessels can lead to ischemia, and frequently reported by SLE patients. Using whole blood RNA samples, we asked whether gene signatures discriminate SLE patients with coronary microvascular dysfunction (CMD) on cardiac MRI (n=4) from those without (n=7) and whether any signaling pathway is linked to the underlying pathobiology of SLE CMD. RNA-seq analysis revealed 143 differentially expressed (DE) genes between the SLE and healthy control (HC) groups, with virus defense and interferon (IFN) signaling being the key pathways identified as enriched in SLE as expected. We next conducted a comparative analysis of genes differentially expressed in SLE-CMD and SLE-non-CMD relative to HC samples. Our analysis highlighted differences in IFN signaling, RNA sensing and ADP-ribosylation pathways between SLE-CMD and SLE-non-CMD. This is the first study to investigate possible gene signatures associating with CMD in SLE, and our data strongly suggests that distinct molecular mechanisms underly vascular changes in CMD and non-CMD involvement in SLE.

Predictive modeling of co-infection in lupus nephritis using multiple machine learning algorithms

This study aimed to analyze peripheral blood lymphocyte subsets in lupus nephritis (LN) patients and use machine learning (ML) methods to establish an effective algorithm for predicting co-infection in LN. This study included 111 non-infected LN patients, 72 infected LN patients, and 206 healthy controls (HCs). Patient information, infection characteristics, medication, and laboratory indexes were recorded. Eight ML methods were compared to establish a model through a training group and verify the results in a test group. We trained the ML models, including Logistic Regression, Decision Tree, K-Nearest Neighbors, Support Vector Machine, Multi-Layer Perceptron, Random Forest, Ada boost, Extreme Gradient Boosting (XGB), and further evaluated potential predictors of infection. Infected LN patients had significantly decreased levels of T, B, helper T, suppressor T, and natural killer cells compared to non-infected LN patients and HCs. The number of regulatory T cells (Tregs) in LN patients was significantly lower than in HCs, with infected patients having the lowest Tregs count. Among the ML algorithms, XGB demonstrated the highest accuracy and precision for predicting LN infections. The innate and adaptive immune systems are disrupted in LN patients, and monitoring lymphocyte subsets can help prevent and treat infections. The XGB algorithm was recommended for predicting co-infection in LN.

T cell expressions of aberrant gene signatures and Co-inhibitory receptors (Co-IRs) as predictors of renal damage and lupus disease activity

BACKGROUND

Systemic lupus erythematosus (SLE) is distinguished by an extensive range of clinical heterogeneity with unpredictable disease flares and organ damage. This research investigates the potential of aberrant signatures on T cell genes, soluble Co-IRs/ligands, and Co-IRs expression on T cells as biomarkers for lupus disease parameters.

METHODS

Comparative transcriptome profiling analysis of non-renal and end-stage renal disease (ESRD) phenotypes of SLE was performed using CD4 + and CD8 + cDNA microarrays of sorted T cells. Comparing the expression of Co-IRs on T cells and serum soluble mediators among healthy and SLE phenotypes.

RESULTS

SLE patients with ESRD were downregulated CD38, PLEK, interferon-γ, CX3CR1, FGFBP2, and SLCO4C1 transcripts on CD4 + and CD8 + T cells simultaneously and NKG7, FCRL6, GZMB/H, FcγRIII, ITGAM, Fas ligand, TBX21, LYN, granulysin, CCL4L1, CMKLR1, HLA-DRβ, KIR2DL3, and KLRD1 in CD8 T cells. Pathway enrichment and PPI network analyses revealed that the overwhelming majority of Differentially Expressed Genes (DEGs) have been affiliated with novel cytotoxic, antigen presentation, and chemokine-cell migration signature pathways. CD8 + GZMK + T cells that are varied in nature, including CD161 + Mucosal-associated invariant T (MAIT) cells and CD161- aged-associated T (Taa) cells and CD161-GZMK + GZMB + T cells might account for a higher level of GZMK in CD8 + T cells associated with ESRD. SLE patients have higher TIGIT + , PD1 + , and lower CD127 + cell percentages on CD4 + T cells, higher TIM3 + , TIGIT + , HLA-DR + cell frequency, and lower MFI expression of CD127, CD160 in CD8 T cells. Co-IRs expression in T cells was correlated with soluble PD-1, PDL-2, and TIM3 levels, as well as SLE disease activity, clinical phenotypes, and immune-therapy responses.

CONCLUSION

The signature of dysfunctional pathways defines a distinct immunity pattern in LN ESRD patients. Expression levels of Co-IRs in peripheral blood T cells and serum levels of soluble PD1/PDL-2/TIM3 can serve as biomarkers for evaluating clinical parameters and therapeutic responses.

Beyond T cell exhaustion: TIM-3 regulation of myeloid cells

T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3) is an important immune checkpoint molecule initially identified as a marker of IFN-γ-producing CD4+ and CD8+ T cells. Since then, our understanding of its role in immune responses has significantly expanded. Here, we review emerging evidence demonstrating unexpected roles for TIM-3 as a key regulator of myeloid cell function, in addition to recent work establishing TIM-3 as a delineator of terminal T cell exhaustion, thereby positioning TIM-3 at the interface between fatigued immune responses and reinvigoration. We share our perspective on the antagonism between TIM-3 and T cell stemness, discussing both cell-intrinsic and cell-extrinsic mechanisms underlying this relationship. Looking forward, we discuss approaches to decipher the underlying mechanisms by which TIM-3 regulates stemness, which has remarkable potential for the treatment of cancer, autoimmunity, and autoinflammation.

PD-1/PD-L1 governed cross-talk of exhausted CD8+ T and memory B cells in systemic lupus erythematosus

BACKGROUND

Indeterminate readout of the quantitative interferon-γ release test (QFT) for Mycobacterium tuberculosis screening is a specific laboratory finding for systemic lupus erythematosus (SLE), which may be due to T-cell exhaustion and abnormal programmed death receptor 1 (PD-1)/programmed death-ligand 1 (PD-L1) signalling.

METHODS

We enrolled 104 patients with SLE and 225 with other rheumatic musculoskeletal diseases (RMDs) who presented to the outpatient clinic between 2020 and 2023. Twenty healthy donors served as the controls. The QFT was performed in all participants, and those with indeterminate results were compared among the groups. Immunophenotyping and functional assays were performed using blood mononuclear cells. Interferon (IFN)-γ was detected in vitro and ex vivo in patients with SLE with indeterminate or negative QFT results, before or after rituximab therapy.

RESULTS

104 patients with SLE had a significantly higher rate of indeterminate QFT results was significantly higher (17.31%) than that of 225 patients with RMD (3.56%). Patients with SLE with indeterminate QFT had more active disease (SLEDAI-2K, mean 10.94 vs 4.02, p<0.0001), including a higher incidence of active nephritis (55.56% vs 29.07%). Indeterminate QFT in SLE is mainly caused by an insufficient IFN-γ response in CD8+T cells with exhausted immunophenotypes. The abnormal interaction between exhausted PD-1 high CD8+ T cells and activated PD-L1 low memory B cells in SLE can be reversed with a PD-1 agonist or increased PD-L1 expression. Rituximab treatment indirectly reversed this IFN-γ response.

CONCLUSION

The PD-1/PD-L1 signalling pathway, which governs the crosstalk between exhausted CD8+ T cells and activated memory B cells, is a mechanistic explanation for insufficient interferon-γ response in patients with SLE.

T cell exhaustion dynamics in systemic autoimmune disease

Unlike in infection and cancer, T cell exhaustion in autoimmune disease has not been clearly defined. Here we set out to understand inhibitory protein (PD-1, Tim3, CTLA4, Lag3) expression in CXCR5- and CXCR5+ CD8 and CD4 T cells in systemic lupus erythematosus. CXCR5+ CD8 and CD4 T cells express PD-1 and engage B cells in germinal center reactions, leading to autoantibody formation in autoimmunity. We hypothesized that CXCR5+ CD8 T cells develop an exhausted phenotype as SLE autoimmunity expands from initial to chronic, self-perpetuating disease due to chronic self-antigen exposure. Our results indicate that there is no exhaustion frequency differences between sexes, although disease kinetics vary by sex. CXCR5+ CD8 T cells express primarily IFNγ, known to promote autoimmune disease development, whereas CXCR5-CD8 T cells express TNFα and IFNγ as disease progresses from 2-6 months. Tim3 is the highest expressed inhibitory marker for all CD4 and CD8 T cell populations demonstrating potential for terminally exhausted populations. CTLA4 expression on CD4 T cells suggests potential tolerance induction in these cells. We identified exhaustion phenotypes within autoimmune disease that progress with increasing lupus erythematosus severity and possibly provide a feedback mechanism for immunological tolerance.

Highlights

CXCR5- and CXCR5+ CD8 T cells expand with rate of disease in SLE mouse model.CXCR5+ CD8 T cells are low contributors to TNFα disease progression unlike CXCR5-CD8 T cells but may increase disease mechanisms through high IFNγ production.Inhibitory markers upregulate in frequency with the highest amounts seen in Tim3+ populations. Tim3+Lag3+ expression may be an indicator of terminal differentiation for all populations.Inhibitory marker expression frequency was unrelated to sex.

B cell-intrinsic Myd88 regulates disease progression in murine lupus

Nucleic acid-specific Toll-like receptors (TLRs) have been implicated in promoting disease pathogenesis in systemic lupus erythematosus (SLE). Whether such TLRs mediate disease onset, progression, or both remains undefined; yet the answer to this question has important therapeutic implications. MyD88 is an essential adaptor that acts downstream of IL-1 family receptors and most TLRs. Both global and B cell-specific Myd88 deficiency ameliorated disease in lupus-prone mice when constitutively deleted. To address whether Myd88 was needed to sustain ongoing disease, we induced B cell-specific deletion of Myd88 after disease onset in MRL.Faslpr mice using an inducible Cre recombinase. B cell-specific deletion of Myd88 starting after disease onset resulted in ameliorated glomerulonephritis and interstitial inflammation. Additionally, treated mice had reduced autoantibody formation and an altered B cell compartment with reduced ABC and plasmablast numbers. These experiments demonstrate the role of MyD88 in B cells to sustain disease in murine lupus. Therefore, targeting MyD88 or its upstream activators may be a viable therapeutic option in SLE.

The Role of the Oxidative State and Innate Immunity Mediated by TLR7 and TLR9 in Lupus Nephritis

Lupus nephritis (LN) is a severe complication of systemic lupus erythematosus (SLE) and is considered one of the leading causes of mortality. Multiple immunological pathways are involved in the pathogenesis of SLE, which makes it imperative to deepen our knowledge about this disease's immune-pathological complexity and explore new therapeutic targets. Since an altered redox state contributes to immune system dysregulation, this document briefly addresses the roles of oxidative stress (OS), oxidative DNA damage, antioxidant enzymes, mitochondrial function, and mitophagy in SLE and LN. Although adaptive immunity's participation in the development of autoimmunity is undeniable, increasing data emphasize the importance of innate immunity elements, particularly the Toll-like receptors (TLRs) that recognize nucleic acid ligands, in inflammatory and autoimmune diseases. Here, we discuss the intriguing roles of TLR7 and TLR9 in developing SLE and LN. Also included are the essential characteristics of conventional treatments and some other novel and little-explored alternatives that offer options to improve renal function in LN.

Coordinated Priming of NKG2D Pathway by IL-15 Enhanced Functional Properties of Cytotoxic CD4+CD28- T Cells Expanded in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a systemic autoimmune disorder, and numerous aberrations of T cell responses have been reported and were implicated in its pathophysiology. Recently, CD4-positive T cells with cytotoxic potential were shown to be involved in autoimmune disease progression and tissue damage. However, the effector functions of this cell type and their potential molecular mechanisms in SLE patients remain to be elucidated. In this study, we find that cytotoxic CD4+CD28- T cells are expanded in SLE patients with flow cytometry analysis, and the percentage of CD4+CD28- T cells positively correlates with the Systemic Lupus International Collaborating Clinics/ACR Damage Index (SDI). Furthermore, our study suggests that interleukin-15 (IL-15) promotes the expansion, proliferation, and cytotoxic function of CD4+CD28- T cells in SLE patients through activation of the Janus kinase3-STAT5 pathway. Further study indicates that IL-15 not only mediates the upregulation of NKG2D, but also cooperates with the NKG2D pathway to regulate the activation of the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) pathway. Together, our study demonstrated that proinflammatory and cytolytic CD4+CD28- T cells expand in SLE patients. The pathogenic potential of these CD4+CD28- T cells is driven by the coupling of the IL-15/IL-15R signaling pathway and the NKG2D/DAP10 signaling pathway, which may open new avenues for therapeutic intervention to prevent SLE progression.

The kinetics of mTORC1 activation associates with FOXP3 expression pattern of CD4+ T cells and outcome of steroid-sensitive minimal change disease

Minimal change disease (MCD) usually responds to glucocorticoids (GCs) but relapses in most cases. Relapse pathogenesis after complete remission (CR) remains unclear. We hypothesized that FOXP3+ T regulatory cell (Treg) dysregulation may drive early relapses (ER). In this study, a cohort of 23 MCD patients were treated with a conventional GC regimen for the initial onset of nephrotic syndrome. Upon GC withdrawal, seven patients suffered from ER, while 16 patients sustained remission (SR) during the 12-month follow-up. Patients with ER had reduced FOXP3+ Treg proportions compared with healthy controls. Treg reduction, accompanied by IL-10 impairment, was ascribed to a proportional decline of FOXP3medium rather than FOXP3high cells. GC-induced CR was marked by a rise in the proportions of FOXP3+ and FOXP3medium cells compared to baseline levels. These increases declined in patients with ER. The expression level of phosphorylated ribosomal protein S6 was used to track the dynamic shifts in mTORC1 activity within CD4+ T cells of MCD patients at various stages of treatment. Baseline mTORC1 activity was inversely correlated with FOXP3+ and FOXP3medium Treg proportion. The mTORC1 activity in CD4+ T cells served as a reliable indicator for ER and demonstrated improved performance when paired with FOXP3 expression. Mechanically, targeting mTORC1 intervention by siRNAs sufficiently altered the conversion pattern of CD4+ T cell to FOXP3+ Treg. Taken together, the activity of mTORC1 in CD4+ T cells can act as a credible predictor for ER in MCD, especially when combined with FOXP3 expression, and may offer a potential therapeutic avenue for the treatment of podocytopathies.

LAG-3 as the third checkpoint inhibitor

Lymphocyte activation gene 3 (LAG-3) is an inhibitory receptor that is highly expressed by exhausted T cells. LAG-3 is a promising immunotherapeutic target, with more than 20 LAG-3-targeting therapeutics in clinical trials and a fixed-dose combination of anti-LAG-3 and anti-PD-1 now approved to treat unresectable or metastatic melanoma. Although LAG-3 is widely recognized as a potent inhibitory receptor, important questions regarding its biology and mechanism of action remain. In this Perspective, we focus on gaps in the understanding of LAG-3 biology and discuss the five biggest topics of current debate and focus regarding LAG-3, including its ligands, signaling and mechanism of action, its cell-specific functions, its importance in different disease settings, and the development of novel therapeutics.

B cell-intrinsic TLR7 expression drives severe lupus in TLR9-deficient mice

The endosomal Toll-like receptor 7 (TLR7) is a major driver of murine and human systemic lupus erythematosus (SLE). The role of TLR7 in lupus pathogenesis is enhanced when the regulatory role of TLR9 is absent. TLR7 signaling in plasmacytoid DCs (pDC) is generally thought to be a major driver of the IFN response and disease pathology; however, the cell types in which TLR7 acts to mediate disease have not been distinguished. To address this, we selectively deleted TLR7 in either CD11c+ cells or CD19+ cells; using a TLR7-floxed allele, we created on the lupus-prone MRL/lpr background, along with a BM chimera strategy. Unexpectedly, TLR7 deficiency in CD11c+ cells had no impact on disease, while TLR7 deficiency in CD19+ B cells yielded mild suppression of proteinuria and a trend toward reduced glomerular disease. However, in TLR9-deficient MRL/lpr mice with accelerated SLE, B cell-specific TLR7 deficiency greatly improved disease. These results support revision of the mechanism by which TLR7 drives lupus and highlight a cis regulatory interaction between the protective TLR9 and the pathogenic TLR7 within the B cell compartment. They suggest B cell-directed, dual TLR7 antagonism/TLR9 agonism or dual TLR7/9 antagonism as a potential future therapeutic strategy to treat SLE.

Cordyceps proteins alleviate lupus nephritis through modulation of the STAT3/mTOR/NF-кB signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Cordyceps is a parasitic edible fungus, which is a unique Chinese medicinal material. It has been reported to have immunomodulatory effects and use in kidney disease. Especially, Cordyceps has been used in the treatment of lupus nephritis (LN).

AIM OF STUDY

Cordyceps proteins (CP) have a favorable bidirectional immunomodulatory functions and may have therapeutic potential for LN. However, the underlying molecular mechanism remains unknown. So this study aimed to examine the activities of CP in LN and possible mechanism.

MATERIALS AND METHODS

So proteomics was performed to detect proteins components of Cordyceps, and analysis it. In addition, MRL/lpr mice were used to study the progression of LN. The MRL/lpr mice were fed either CP (i.g, 0.5, 1.0, 1.5 g/kg/d), prednisolone acetate (PA, i.g, 6 mg/kg/d), or Bailing capsule (BC, i.g, 0.75 g/kg/d) for 8 weeks. Hematoxylin-eosin (H&E), Periodic Acid Schif (PAS) and Masson's stainings, Immunofluorescence, and Immunohistochemistry were performed to verify the therapeutic effect of CP on MRL/lpr mice. The mechanism by CP alimerated LN was uncovered by Western blotting (WB) and Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) methods.

RESULTS

Our results revealed that CP blocked proteinuria production and renal inflammatory infiltratation in MRL/lpr mice to reduce the renal fibrosis. In addition, CP worked better than BC which is artificial Cordyceps fungus powder in regulating proteinuria to urine creatinine ratio and interleukin-4(IL-4) protein amount. Especially, CP modulated the STAT3/mTOR/NF-кB signaling pathway in LN mice and brought a more pronounced lowering effect on the contents of IL-6 and IL-1β than the PA.

CONCLUSION

CP could be a potential anti-inflammatory immune product with strong regulatory effects and potency than BC and PA in nephritis therapeutics.

The Role of Pyruvate Metabolism in Mitochondrial Quality Control and Inflammation

Pyruvate metabolism, a key pathway in glycolysis and oxidative phosphorylation, is crucial for energy homeostasis and mitochondrial quality control (MQC), including fusion/fission dynamics and mitophagy. Alterations in pyruvate flux and MQC are associated with reactive oxygen species accumulation and Ca2+ flux into the mitochondria, which can induce mitochondrial ultrastructural changes, mitochondrial dysfunction and metabolic dysregulation. Perturbations in MQC are emerging as a central mechanism for the pathogenesis of various metabolic diseases, such as neurodegenerative diseases, diabetes and insulin resistance-related diseases. Mitochondrial Ca2+ regulates the pyruvate dehydrogenase complex (PDC), which is central to pyruvate metabolism, by promoting its dephosphorylation. Increase of pyruvate dehydrogenase kinase (PDK) is associated with perturbation of mitochondria-associated membranes (MAMs) function and Ca2+ flux. Pyruvate metabolism also plays an important role in immune cell activation and function, dysregulation of which also leads to insulin resistance and inflammatory disease. Pyruvate metabolism affects macrophage polarization, mitochondrial dynamics and MAM formation, which are critical in determining macrophage function and immune response. MAMs and MQCs have also been intensively studied in macrophage and T cell immunity. Metabolic reprogramming connected with pyruvate metabolism, mitochondrial dynamics and MAM formation are important to macrophages polarization (M1/M2) and function. T cell differentiation is also directly linked to pyruvate metabolism, with inhibition of pyruvate oxidation by PDKs promoting proinflammatory T cell polarization. This article provides a brief review on the emerging role of pyruvate metabolism in MQC and MAM function, and how dysfunction in these processes leads to metabolic and inflammatory diseases.

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.

Targeted Therapy for SLE-What Works, What Doesn't, What's Next

For many years, the failure of randomized controlled trials (RCTs) has prevented patients with systemic lupus erythematosus (SLE) from benefiting from biological drugs that have proved to be effective in other rheumatological diseases. Only two biologics are approved for SLE, however they can only be administered to a restricted proportion of patients. Recently, several phase II RCTs have evaluated the efficacy and safety of new biologics in extra-renal SLE and lupus nephritis. Six drug trials have reported encouraging results, with an improvement in multiple clinical and serological outcome measures. The possibility of combining B-cell depletion and anti-BLyS treatment has also been successfully explored.

Regulation and Immunotherapeutic Targeting of the Epigenome in Exhausted CD8 T Cell Responses

Exhaustion is a state of CD8 T cell differentiation that occurs in settings of chronic Ag such as tumors, chronic viral infection, and autoimmunity. Cellular differentiation is driven by a series of environmental signals that promote epigenetic landscapes that set transcriptomes needed for function. For CD8 T cells, the epigenome that underlies exhaustion is distinct from effector and memory cell differentiation, suggesting that signals early on set in motion a process where the epigenome is modified to promote a trajectory toward a dysfunctional state. Although we know many signals that promote exhaustion, putting this in the context of the epigenetic changes that occur during differentiation has been less clear. In this review, we aim to summarize the epigenetic changes associated with exhaustion in the context of signals that promote it, highlighting immunotherapeutic studies that support these observations or areas for future therapeutic opportunities.

Graft-versus-host disease is locally maintained in target tissues by resident progenitor-like T cells

In allogeneic hematopoietic stem cell transplantation, donor αβ T cells attack recipient tissues, causing graft-versus-host disease (GVHD), a major cause of morbidity and mortality. A central question has been how GVHD is sustained despite T cell exhaustion from chronic antigen stimulation. The current model for GVHD holds that disease is maintained through the continued recruitment of alloreactive effectors from blood into affected tissues. Here, we show, using multiple approaches including parabiosis of mice with GVHD, that GVHD is instead primarily maintained locally within diseased tissues. By tracking 1,203 alloreactive T cell clones, we fitted a mathematical model predicting that within each tissue a small number of progenitor T cells maintain a larger effector pool. Consistent with this, we identified a tissue-resident TCF-1+ subpopulation that preferentially engrafted, expanded, and differentiated into effectors upon adoptive transfer. These results suggest that therapies targeting affected tissues and progenitor T cells within them would be effective.

Tissue-resident memory T cells in renal autoimmune diseases

The discovery of tissue-resident memory T cells (T_RM cells) reinterpreted the potential of human tissue-specific immunity. Following T cell receptor (TCR) activation and clonal expansion, effector T cells migrate to peripheral tissues where they remain long-term and differentiate to T_RM cells after antigen clearance. This allows for prompt immunological responses upon antigen re-encounter. In addition to their protective properties in acute infections, recent studies have revealed that T_RM cells might lead to aggravation of autoimmune diseases, such as lupus nephritis (LN) and anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis (GN). These diseases present as proliferative and crescentic glomerulonephritis (cGN), which is a life-threatening condition leading to end-stage renal disease (ESRD) if left untreated. A better understanding of renal T_RM cells might lead to identifying new therapeutic targets for relapsing autoimmune diseases of the kidney. In this review, we summarize the current knowledge of renal T_RM cells and discuss their potential pathophysiological roles in renal autoimmune diseases.

Low dose interleukin-2 selectively expands circulating regulatory T cells but fails to promote liver allograft tolerance in humans

BACKGROUND & AIMS

CD4+CD25+Foxp3+ regulatory T cells (Tregs) are essential to maintain immunological tolerance and have been shown to promote liver allograft tolerance in both rodents and humans. Low-dose IL-2 (LDIL-2) can expand human endogenous circulating Tregs in vivo, but its role in suppressing antigen-specific responses and promoting Treg trafficking to the sites of inflammation is unknown. Likewise, whether LDIL-2 facilitates the induction of allograft tolerance has not been investigated in humans.

METHODS

We conducted a clinical trial in stable liver transplant recipients 2-6 years post-transplant to determine the capacity of LDIL-2 to suppress allospecific immune responses and allow for the complete discontinuation of maintenance immunosuppression (ClinicalTrials.gov NCT02949492). One month after LDIL-2 was initiated, those exhibiting at least a 2-fold increase in circulating Tregs gradually discontinued immunosuppression over a 4-month period while continuing LDIL-2 for a total treatment duration of 6 months.

RESULTS

All participants achieved a marked and sustained increase in circulating Tregs. However, this was not associated with the preferential expansion of donor-reactive Tregs and did not promote the accumulation of intrahepatic Tregs. Furthermore, LDIL-2 induced a marked IFNγ-orchestrated transcriptional response in the liver even before immunosuppression weaning was initiated. The trial was terminated after the first 6 participants failed to reach the primary endpoint owing to rejection requiring reinstitution of immunosuppression.

CONCLUSIONS

The expansion of circulating Tregs in response to LDIL-2 is not sufficient to control alloimmunity and to promote liver allograft tolerance, due, at least in part, to off-target effects that increase liver immunogenicity. Our trial provides unique insight into the mechanisms of action of immunomodulatory therapies such as LDIL-2 and their limitations in promoting alloantigen-specific effects and immunological tolerance.

CLINICAL TRIALS REGISTRATION

The study is registered at ClinicalTrials.gov (NCT02949492).

IMPACT AND IMPLICATIONS

The administration of low-dose IL-2 is an effective way of increasing the number of circulating regulatory T cells (Tregs), an immunosuppressive lymphocyte subset that is key for the establishment of immunological tolerance, but its use to promote allograft tolerance in the setting of clinical liver transplantation had not been explored before. In liver transplant recipients on tacrolimus monotherapy, low-dose IL-2 effectively expanded circulating Tregs but did not increase the number of Tregs with donor specificity, nor did it promote their trafficking to the transplanted liver. Low-dose IL-2 did not facilitate the discontinuation of tacrolimus and elicited, as an off-target effect, an IFNγ-orchestrated inflammatory response in the liver that resembled T cell-mediated rejection. These results, supporting an unexpected role for IL-2 in regulating the immunogenicity of the liver, highlight the need to carefully evaluate systemic immunoregulatory strategies with investigations that are not restricted to the blood compartment and involve target tissues such as the liver.

CXCR5+CD8 T cells: Potential immunotherapy targets or drivers of immune-mediated adverse events?

CXCR5⁺CD8 T cells have attracted significant interest within multiple areas of immunology, cancer, and infection. This is in part due to their apparent dual functionality. These cells perform as cytotoxic cells in a variety of infection states including LCMV, HBV, HIV and SIV. However, CXCR5⁺CD8 T cells also associate with B cells in peripheral organs and function to stimulate B cell proliferation, antibody/B cell receptor class-switch, and antibody production. CXCR5⁺CD8 T cells are similar to CXCR5⁺CD4 T follicular helpers in their genetic make-up, B cell interactions, and functionality despite possessing elevated programmed cell death 1 and cytotoxic proteins. Within cancer CXCR5⁺CD8 T cells have risen as potential prognostic markers for overall survival and are functionally cytotoxic within tumor microenvironments. In inflammatory disease and autoimmunity, CXCR5⁺CD8 T cells are implicated in disease progression. During viral infection and cancer, CXCR5 expression on CD8 T cells generally is indicative of progenitor memory stem-like exhausted cells, which are more responsive to immune checkpoint blockade therapy. The use of immune checkpoint inhibitors to overcome immune exhaustion in cancer, and subsequent consequence of immune adverse events, highlights the dual nature of the cellular immune response. This review will detail the functionality of CXCR5⁺CD8 T cells in cancer and autoimmunity with potential repercussions during immune checkpoint blockade therapy discussed.

T-cell exhaustion in immune-mediated inflammatory diseases: New implications for immunotherapy

Immune-mediated inflammatory diseases(IMIDs) are referred to as highly disabling chronic diseases affecting different organs and systems. Inappropriate or excessive immune responses with chronic inflammation are typical manifestations. Usually in patients with chronic infection and cancer, due to long-term exposure to persistent antigens and inflammation microenvironment, T-cells are continuously stimulated and gradually differentiate into an exhausted state. Exhausted T-cells gradually lose effector function and characteristics of memory T-cells. However, existing studies have found that exhausted T-cells are not only present in the infection and tumor environment, but also in autoimmunity, and are associated with better prognosis of IMIDs. This suggests new prospects for the application of this reversible process of T-cell exhaustion in the treatment of IMID. This review will focus on the research progress of T-cell exhaustion in several IMIDs and its potential application for diagnosis and treatment in IMIDs.

Short and long-term immune changes in different severity groups of COVID-19 disease

BACKGROUND

There are limited data on short- versus long-term changes in adaptive immune response across different COVID-19 disease severity groups.

METHODS

A multicenter prospective study of 140 adult patients with COVID-19 (a total of 325 samples) were analyzed for inflammatory markers and lymphocyte subsets at presentation, week 2, and week 24.

RESULTS

Inflammatory markers at presentation were higher in the critical/severe than in moderate and mild groups. A predominance of memory B cell response in the mild and moderate group was noted by week 2. In contrast, the immune system in the severe/critical group was dysfunctional, with expansion of exhausted CD8+ T cells and atypical memory B cells. By 24 weeks, there was a possible trend of normalization.

CONCLUSION

There was substantial difference in the degree of inflammation and distribution of different B and T cell subsets in the different disease severity groups. Despite the initial dysfunctional immune response in the severe/critical group, a comparable memory B and CD8+ T cell responses to the mild group was achieved at 24 weeks.

Apoptotic vesicles ameliorate lupus and arthritis via phosphatidylserine-mediated modulation of T cell receptor signaling

Mesenchymal stem cells (MSCs) influence T cells in health, disease and therapy through messengers of intercellular communication including extracellular vesicles (EVs). Apoptosis is a mode of cell death that tends to promote immune tolerance, and a large number of apoptotic vesicles (apoVs) are generated from MSCs during apoptosis. In an effort to characterize these apoVs and explore their immunomodulatory potential, here we show that after replenishing them systemically, the apoV deficiency in Fas mutant mice and pathological lymphoproliferation were rescued, leading to the amelioration of inflammation and lupus activity. ApoVs directly interacted with CD4⁺ T cells and inhibited CD25 expression and IL-2 production in a dose-dependent manner. A broad range of Th1/2/17 subsets and cytokines including IFNγ, IL17A and IL-10 were suppressed while Foxp3⁺ cells were maintained. Mechanistically, exposed phosphatidylserine (PtdSer/PS) on apoVs mediated the interaction with T cells to disrupt proximal T cell receptor signaling transduction. Remarkably, administration of apoVs prevented Th17 differentiation and memory formation, and ameliorated inflammation and joint erosion in murine arthritis. Collectively, our findings unveil a previously unrecognized crosstalk between MSC apoVs and CD4⁺ T cells and suggest a promising therapeutic use of apoVs for autoimmune diseases.

Lymphocytes in the neighborhood: good or bad for the kidney?

Lupus nephritis (LN) is common in people with systemic lupus erythematosus (SLE) and advances, almost invariably, to end-stage renal disease (ESRD). In this issue of the JCI, Abraham, Durkee, et al. presented a large-scale immune cell landscape of kidney biopsies from patients with LN by combining multiplexed confocal microscopy imaging with customized computer vision and quantification. The presence of diverse CD4^– T cells in small neighborhoods, but not of B cells or CD4⁺ T cells in large neighborhoods, is linked to the development of ESRD. Unexpectedly, B cells in the kidney heralded a good prognosis. The precise location of different types of immune cells allows inference on possible interactions between different immune cells and also between immune and kidney-resident cells. The data have important implications on the development of prognostic tools and effective targeted therapies in patients with LN.

Autoreactive CD8+ T cells are restrained by an exhaustion-like program that is maintained by LAG3

Impaired chronic viral and tumor clearance has been attributed to CD8⁺ T cell exhaustion, a differentiation state in which T cells have reduced and altered effector function that can be partially reversed upon blockade of inhibitory receptors. The role of the exhaustion program and transcriptional networks that control CD8⁺ T cell function and fate in autoimmunity is not clear. Here we show that intra-islet CD8⁺ T cells phenotypically, transcriptionally, epigenetically and metabolically possess features of canonically exhausted T cells, yet maintain important differences. This 'restrained' phenotype can be perturbed and disease accelerated by CD8⁺ T cell-restricted deletion of the inhibitory receptor lymphocyte activating gene 3 (LAG3). Mechanistically, LAG3-deficient CD8⁺ T cells have enhanced effector-like functions, trafficking to the islets, and have a diminished exhausted phenotype, highlighting a physiological role for an exhaustion program in limiting autoimmunity and implicating LAG3 as a target for autoimmune therapy.

Specific in situ inflammatory states associate with progression to renal failure in lupus nephritis

BACKGROUND

In human lupus nephritis (LN), tubulointerstitial inflammation (TII) on biopsy predicts progression to end-stage renal disease (ESRD). However, only about half of patients with moderate-to-severe TII develop ESRD. We hypothesized that this heterogeneity in outcome reflects different underlying inflammatory states. Therefore, we interrogated renal biopsies from LN longitudinal and cross-sectional cohorts.

METHODS

Data were acquired using conventional and highly multiplexed confocal microscopy. To accurately segment cells across whole biopsies, and to understand their spatial relationships, we developed computational pipelines by training and implementing several deep-learning models and other computer vision techniques.

RESULTS

High B cell densities were associated with protection from ESRD. In contrast, high densities of CD8⁺, γδ, and other CD4^–CD8^– T cells were associated with both acute renal failure and progression to ESRD. B cells were often organized into large periglomerular neighborhoods with Tfh cells, while CD4^– T cells formed small neighborhoods in the tubulointerstitium, with frequency that predicted progression to ESRD.

CONCLUSION

These data reveal that specific in situ inflammatory states are associated with refractory and progressive renal disease.

FUNDING

This study was funded by the NIH Autoimmunity Centers of Excellence (AI082724), Department of Defense (LRI180083), Alliance for Lupus Research, and NIH awards (S10-OD025081, S10-RR021039, and P30-CA14599).

T Cell Help in the Autoreactive Germinal Center

The germinal center serves as a site of B cell selection and affinity maturation, critical processes for productive adaptive immunity. In autoimmune disease tolerance is broken in the germinal center reaction, leading to production of autoreactive B cells that may propagate disease. Follicular T cells are crucial regulators of this process, providing signals necessary for B cell survival in the germinal center. Here we review the emerging roles of follicular T cells in the autoreactive germinal center. Recent advances in immunological techniques have allowed study of the gene expression profiles and repertoire of follicular T cells at unprecedented resolution. These studies provide insight into the potential role follicular T cells play in preventing or facilitating germinal center loss of tolerance. Improved understanding of the mechanisms of T cell help in autoreactive germinal centers provides novel therapeutic targets for diseases of germinal center dysfunction.

Lupus Susceptibility Loci Predispose Mice to Clonal Lymphocytic Responses and Myeloid Expansion

Lupus susceptibility results from the combined effects of numerous genetic loci, but the contribution of these loci to disease pathogenesis has been difficult to study due to the large cellular heterogeneity of the autoimmune immune response. We performed single-cell RNA, BCR, and TCR sequencing of splenocytes from mice with multiple polymorphic lupus susceptibility loci. We not only observed lymphocyte and myeloid expansion, but we also characterized changes in subset frequencies and gene expression, such as decreased CD8 and marginal zone B cells and increased Fcrl5- and Cd5l-expressing macrophages. Clonotypic analyses revealed expansion of B and CD4 clones, and TCR repertoires from lupus-prone mice were distinguishable by algorithmic specificity prediction and unsupervised machine learning classification. Myeloid differential gene expression, metabolism, and altered ligand-receptor interaction were associated with decreased Ag presentation. This dataset provides novel mechanistic insight into the pathophysiology of a spontaneous model of lupus, highlighting potential therapeutic targets for autoantibody-mediated disease.

Pathogenic T-Cell Responses in Immune-Mediated Glomerulonephritis

Glomerulonephritis (GN) comprises a group of immune-mediated kidney diseases affecting glomeruli and the tubulointerstitium. Glomerular crescent formation is a histopathological characteristic of severe forms of GN, also referred to as crescentic GN (cGN). Based on histological findings, cGN includes anti-neutrophil cytoplasmic antibody (ANCA)-associated GN, a severe form of ANCA-associated vasculitis, lupus nephritis associated with systemic lupus erythematosus, Goodpasture’s disease, and IgA nephropathy. The immunopathogenesis of cGN is associated with activation of CD4+ and CD8+ T cells, which particularly accumulate in the periglomerular and tubulointerstitial space but also infiltrate glomeruli. Clinical observations and functional studies in pre-clinical animal models provide evidence for a pathogenic role of Th1 and Th17 cell-mediated immune responses in cGN. Emerging evidence further argues that CD8+ T cells have a role in disease pathology and the mechanisms of activation and function of recently identified tissue-resident CD4+ and CD8+ T cells in cGN are currently under investigation. This review summarizes the mechanisms of pathogenic T-cell responses leading to glomerular damage and renal inflammation in cGN. Advanced knowledge of the underlying immune mechanisms involved with cGN will enable the identification of novel therapeutic targets for the replacement or reduction in standard immunosuppressive therapy or the treatment of refractory disease.

Glucocorticoid prevents CD138 expression in T cells of autoimmune MRL/lpr mice

CD138⁺ T cells, the majority of which are CD4 and CD8 double-negative (DN) T cells, contribute to the production of anti-dsDNA antibodies in a CD4 receptor-dependent way to promote the development of systemic lupus erythematosus (SLE). Accumulation of CD138⁺ T cells in the spleen of MRL/lpr mice was significantly reduced by prednisone. Reduced expression of CD138 in DN T cells induced by prednisone treatment alleviated the accumulation of DN T cells in MRL/lpr mice. The frequency of CD138⁺ cells in CD4⁺ T cells of prednisone-treated MRL/lpr mice was also significantly reduced, which subsequently contributed to reduced production of anti-dsDNA antibody in the prednisone-treated MRL/lpr mice. Additionally, prednisone significantly reduced serum IgG and IgG subsets and simultaneously increased IgM secretion in serum. This suggested that glucocorticoids played a protective role during SLE treatment in MRL/lpr mice by promoting the production of IgM. The present study provides new insights into the mechanism of glucocorticoid for the treatment of SLE.

Heterogeneity and clonality of kidney-infiltrating T cells in murine lupus nephritis

We previously found that kidney-infiltrating T cells (KITs) in murine lupus nephritis (LN) resembled dysfunctional T cells that infiltrate tumors. This unexpected finding raised the question of how to reconcile the "exhausted" phenotype of KITs with ongoing tissue destruction in LN. To address this, we performed single-cell RNA-Seq and TCR-Seq of KITs in murine lupus models. We found that CD8+ KITs existed first in a transitional state, before clonally expanding and evolving toward exhaustion. On the other hand, CD4+ KITs did not fit into current differentiation paradigms but included both hypoxic and cytotoxic subsets with a pervasive exhaustion signature. Thus, autoimmune nephritis is unlike acute pathogen immunity; rather, the kidney microenvironment suppresses T cells by progressively inducing exhausted states. Our findings suggest that LN, a chronic condition, results from slow evolution of damage caused by dysfunctional T cells and their precursors on the way to exhaustion. These findings have implications for both autoimmunity and tumor immunology.

Immunomodulatory Activity of Mesenchymal Stem Cells in Lupus Nephritis: Advances and Applications

Lupus nephritis (LN) is a significant cause of various acute and chronic renal diseases, which can eventually lead to end-stage renal disease. The pathogenic mechanisms of LN are characterized by abnormal activation of the immune responses, increased cytokine production, and dysregulation of inflammatory signaling pathways. LN treatment is an important issue in the prevention and treatment of systemic lupus erythematosus. Mesenchymal stem cells (MSCs) have the advantages of immunomodulation, anti-inflammation, and anti-proliferation. These unique properties make MSCs a strong candidate for cell therapy of autoimmune diseases. MSCs can suppress the proliferation of innate and adaptive immune cells, such as natural killer cells (NKs), dendritic cells (DCs), T cells, and B cells. Furthermore, MSCs suppress the functions of various immune cells, such as the cytotoxicity of T cells and NKs, maturation and antibody secretion of B cells, maturation and antigen presentation of DCs, and inhibition of cytokine secretion, such as interleukins (ILs), tumor necrosis factor (TNF), and interferons (IFNs) by a variety of immune cells. MSCs can exert immunomodulatory effects in LN through these immune functions to suppress autoimmunity, improve renal pathology, and restore kidney function in lupus mice and LN patients. Herein, we review the role of immune cells and cytokines in the pathogenesis of LN and the mechanisms involved, as well as the progress of research on the immunomodulatory role of MSCs in LN.

Tissue-resident memory T cells in the urogenital tract

Our understanding of T cell memory responses changed drastically with the discovery that specialized T cell memory populations reside within peripheral tissues at key pathogen entry sites. These tissue-resident memory T (T_RM) cells can respond promptly to an infection without the need for migration, proliferation or differentiation. This rapid and local deployment of effector functions maximizes the ability of T_RM cells to eliminate pathogens. T_RM cells do not circulate through peripheral tissues but instead form isolated populations in the skin, gut, liver, kidneys, the reproductive tract and other organs. This long-term retention in the periphery might allow T_RM cells to fully adapt to the local conditions of their environment and mount customized responses to counter infection and tumour growth in a tissue-specific manner. In the urogenital tract, T_RM cells must adapt to a unique microenvironment to confer protection against potential threats, including cancer and infection, while preventing the onset of auto-inflammatory disease. In this Review, we discuss insights into the diversification of T_RM cells from other memory T cell lineages, the adaptations of T_RM cells to their local environment, and their enhanced capacity to counter infection and tumour growth compared with other memory T cell populations, especially in the urogenital tract.

Regulation of activated T cell survival in rheumatic autoimmune diseases

Adaptive immune responses rely on the proliferation of T lymphocytes able to recognize and eliminate pathogens. The magnitude and duration of the expansion of activated T cell clones are finely regulated to minimize immunopathology and avoid autoimmunity. In patients with rheumatic autoimmune diseases, such as systemic lupus erythematosus and rheumatoid arthritis, activated lymphocytes survive and exert effector functions for prolonged periods, defying the mechanisms that normally curb their capacities during acute and chronic infections. Here, we review the molecular mechanisms that limit the duration of immune responses in health and discuss the factors that alter such regulation in the setting of systemic lupus erythematosus and rheumatoid arthritis. We highlight defects that could contribute to the development and progression of autoimmune disease and describe how chronic inflammation can alter the regulation of activated lymphocyte survival, promoting its perpetuation. These concepts might contribute to the understanding of the mechanisms that underlie the chronicity of inflammation in the context of autoimmunity.

T Cell Homeostatic Proliferation Promotes a Redox State That Drives Metabolic and Epigenetic Upregulation of Inflammatory Pathways in Lupus

Significance: Numerous abnormalities in T cells have been described in patients with systemic lupus erythematosus (SLE), including lymphopenia, DNA demethylation, expression of endogenous retroviruses (ERVs), increased cell death, enlarged mitochondria, production of reactive oxygen species (ROS), and the appearance of unusual CD4^-CD8^- T cells. Our studies propose a model in which accelerated homeostatic proliferation of T cells promotes an epigenetic and metabolic program, leading to this cluster of abnormalities. Recent Advances: Growing knowledge of the innate immune disorders in SLE has included increased mitochondrial size and ROS production that induces oligomerization of the mitochondrial antiviral signaling (MAVS) protein and type I interferon production, as well as DNA demethylation, upregulation of inflammatory genes, and expression of certain ERVs in SLE peripheral blood mononuclear cells. All these events are part of the cellular program that occurs during homeostatic proliferation of T cells. Evidence from a murine model of SLE as well as in human SLE reveals that increased T cell homeostatic proliferation may be a driving factor in these processes. Critical Issues: Despite extensive knowledge of the myriad autoantibodies in SLE and other immune abnormalities, a cogent model has been lacking to link the numerous and seemingly disparate immune aberrations. This may partly explain the general lack of new drugs specifically for SLE in over 50 years. A more coherent model of SLE would not only unify the variety of immune abnormalities is SLE but would also suggest new therapies. Future Directions: The model of augmented homeostatic proliferation leading to increased mitochondrial mass, ROS, DNA demethylation, and upregulation of inflammatory genes suggests strategic new targets for SLE, including antioxidants and certain inhibitors of metabolism. Antioxid. Redox Signal. 36, 410-422.

Advances in understanding and examining lymphatic function: relevance for understanding autoimmunity

PURPOSE OF REVIEW

The aim of this review is to give insights into how novel lymphatics functions may influence autoimmunity.

RECENT FINDINGS

The lymphatic system connects peripheral tissues to draining lymph nodes to regulate adaptive immunity and directly interfaces with leukocytes in lymph vessels and in the lymph node. Here, we discuss recent findings showing evidence of dysfunctional lymphatics in autoimmune disease, new understanding of how afferent lymphatic regulation can modulate immunity, lymph node lymphatic heterogeneity and how these lymphatics can directly modulate lymphocyte function, how this understanding can be harnessed for new therapeutics, and new tools for the investigation of lymphatic and immune biology.

SUMMARY

Lymphatics have an active role in the regulation of inflammation and the adaptive immune response. Here, we review recent findings in lymphatics biology in peripheral tissues and lymph nodes and emphasize the relevance for better understanding autoimmune diseases.

Exploration of Potential Integrated Models of N6-Methyladenosine Immunity in Systemic Lupus Erythematosus by Bioinformatic Analyses

Systemic lupus erythematosus (SLE) is a prototypical systemic autoimmune disease of unknown etiology. The epigenetic regulation of N6-methyladenosine (m6A) modification in immunity is emerging. However, few studies have focused on SLE and m6A immune regulation. In this study, we aimed to explore a potential integrated model of m6A immunity in SLE. The models were constructed based on RNA-seq data of SLE. A consensus clustering algorithm was applied to reveal the m6A-immune signature using principal component analysis (PCA). Univariate and multivariate Cox regression analyses and Kaplan–Meier analysis were used to evaluate diagnostic differences between groups. The effects of m6A immune-related characteristics were investigated, including risk evaluation of m6A immune phenotype-related characteristics, immune cell infiltration profiles, diagnostic value, and enrichment pathways. CIBERSORT, ESTIMATE, and single-sample gene set enrichment analysis (ssGSEA) were used to evaluate the relative immune cell infiltrations (ICIs) of the samples. Conventional bioinformatics methods were used to identify key m6A regulators, pathways, gene modules, and the coexpression network of SLE. In summary, our study revealed that IGFBP3 (as a key m6A regulator) and two pivotal immune genes (CD14 and IDO1) may aid in the diagnosis and treatment of SLE. The potential integrated models of m6A immunity that we developed could guide clinical management and may contribute to the development of personalized immunotherapy strategies.

Spontaneous CD4+ T Cell Activation and Differentiation in Lupus-Prone B6.Nba2 Mice Is IFNAR-Independent

Systemic lupus erythematosus (SLE) is an autoimmune disorder characterized by dysregulated T and B lymphocytes. Type I interferons (IFN-I) have been shown to play important pathogenic roles in both SLE patients and mouse models of lupus. Recent studies have shown that B cell intrinsic responses to IFN-I are enough to drive B cell differentiation into autoantibody-secreting memory B cells and plasma cells, although lower levels of residual auto-reactive cells remain present. We speculated that IFN-I stimulation of T cells would similarly drive specific T-cell associated lupus phenotypes including the upregulation of T follicular helper cells and Th17, thereby affecting autoantibody production and the development of glomerulonephritis. Using the B6.Nba2 mouse model of lupus, we evaluated disease parameters in T cell specific IFN-I receptor (IFNAR)-deficient mice (cKO). Surprisingly, all measured CD4+ T cell abnormalities and associated intra-splenic cytokine levels (IFNγ, IL-6, IL-10, IL-17, IL-21) were unchanged and thus independent of IFN-I. In contrast B6.Nba2 cKO mice displayed reduced levels of effector CD8+ T cells and increased levels of Foxp3+ CD8+ regulatory T cells, suggesting that IFN-I induced signaling specifically affecting CD8+ T cells. These data suggest a role for both pathogenic and immunosuppressive CD8+ T cells in Nba2-driven autoimmunity, providing a model to further evaluate the role of these cell subsets during lupus-like disease development in vivo.

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.

The CD6/ALCAM pathway promotes lupus nephritis via T cell-mediated responses

T cells are central to the pathogenesis of lupus nephritis (LN), a common complication of systemic lupus erythematosus (SLE). CD6 and its ligand, activated leukocyte cell adhesion molecule (ALCAM), are involved in T cell activation and trafficking. Previously, we showed that soluble ALCAM is increased in urine (uALCAM) of patients with LN, suggesting that this pathway contributes to disease. To investigate, uALCAM was examined in 1038 patients with SLE and LN from 5 ethnically diverse cohorts; CD6 and ALCAM expression was assessed in LN kidney cells; and disease contribution was tested via antibody blockade of CD6 in murine models of SLE and acute glomerulonephritis. Extended cohort analysis offered resounding validation of uALCAM as a biomarker that distinguishes active renal involvement in SLE, irrespective of ethnicity. ALCAM was expressed by renal structural cells whereas CD6 expression was exclusive to T cells, with elevated numbers of CD6+ and ALCAM+ cells in patients with LN. CD6 blockade in models of spontaneous lupus and immune-complex glomerulonephritis revealed significant decreases in immune cells, inflammatory markers, and disease measures. Our data demonstrate the contribution of the CD6/ALCAM pathway to LN and SLE, supporting its use as a disease biomarker and therapeutic target.

Axl regulated survival/proliferation network and its therapeutic intervention in mouse models of glomerulonephritis

BACKGROUND

Lupus nephritis (LN) is the most common and serious complication of systemic lupus erythematosus (SLE). LN pathogenesis is not fully understood. Axl receptor tyrosine kinase is upregulated and contributes to the pathogenic progress in LN. We have reported that Axl disruption attenuates nephritis development in mice.

METHODS

In this study, we analyzed the gene expression profiles with RNA-seq using renal cortical samples from nephritic mice. Axl-KO mice were bred onto a B6.lpr spontaneous lupus background, and renal disease development was followed and compared to the Axl-sufficient B6.lpr mice. Finally, anti-glomerular basement membrane (anti-GBM) Ab-induced nephritic mice were treated with Axl small molecule inhibitor, R428, at different stages of nephritis development. Blood urine nitrogen levels and renal pathologies were evaluated.

RESULTS

Transcriptome analysis revealed that renal Axl activation contributed to cell proliferation, survival, and motility through regulation of the Akt, c-Jun, and actin pathways. Spontaneous lupus-prone B6.lpr mice with Axl deficiency showed significantly reduced kidney damages and decreased T cell infiltration compared to the renal damage and T cell infiltration in Axl-sufficient B6.lpr mice. The improved kidney function was independent of autoAb production. Moreover, R428 significantly reduced anti-GBM glomerulonephritis at different stages of GN development compared to the untreated nephritic control mice. R428 administration reduced inflammatory cytokine (IL-6) production, T cell infiltration, and nephritis disease activity.

CONCLUSIONS

Results from this study emphasize the important role of Axl signaling in LN and highlight Axl as an attractive target in LN.

Immunosenescence: an unexplored role in glomerulonephritis

Immunosenescence is a natural ageing phenomenon with alterations in innate and especially adaptive immunity and contributes to reduced antimicrobial defence and chronic low‐grade inflammation. This is mostly reflected by an increase in organ‐directed and/or circulating reactive and cytolytic terminally differentiated T cells that have lost their expression of the costimulatory receptor CD28. Apart from being induced by a genetic predisposition, ageing or viral infections (particularly cytomegalovirus infection), immunosenescence is accelerated in many inflammatory diseases and uraemia. This translates into an enhancement of vascular inflammation and cardiovascular disease varying from endothelial dysfunction to plaque rupture. Emerging data point to a mechanistic role of CD28^null T cells in glomerulonephritis, where they initiate and propagate local inflammation in concordance with dendritic cells and macrophages. They are suitably equipped to escape immunological dampening by the absence of homing to lymph nodes, anti‐apoptotic properties and resistance to suppression by regulatory T cells. Early accumulation of senescent CD28^null T cells precedes glomerular or vascular injury, and targeting these cells could open avenues for early treatment interventions that aim at abrogating a detrimental vicious cycle.

Tissue-resident memory T cells in the kidney

The identification of tissue-resident memory T cells (T_RM cells) has significantly improved our understanding of immunity. In the last decade, studies have demonstrated that T_RM cells are induced after an acute T-cell response, remain in peripheral organs for several years, and contribute to both an efficient host defense and autoimmune disease. T_RM cells are found in the kidneys of healthy individuals and patients with various kidney diseases. A better understanding of these cells and their therapeutic targeting might provide new treatment options for infections, autoimmune diseases, graft rejection, and cancer. In this review, we address the definition, phenotype, and developmental mechanisms of T_RM cells. Then, we further discuss the current understanding of T_RM cells in kidney diseases, such as infection, autoimmune disease, cancer, and graft rejection after transplantation.