Association between tubulointerstitial CD8+T cells and renal prognosis in lupus nephritis

Immune imbalance in Lupus Nephritis: The intersection of T-Cell and ferroptosis

Ferroptosis is a novel form of cell death characterized by unlimited accumulation of iron-dependent lipid peroxides. It is often accompanied by disease, and the relationship between ferroptosis of immune cells and immune regulation has been attracting increasing attention. Initially, it was found in cancer research that the inhibition of regulatory T cell (Treg) ferroptosis and the promotion of CD8+ T cell ferroptosis jointly promoted the formation of an immune-tolerant environment in tumors. T-cell ferroptosis has subsequently been found to have immunoregulatory effects in other diseases. As an autoimmune disease characterized by immune imbalance, T-cell ferroptosis has attracted attention for its potential in regulating immune balance in lupus nephritis. This article reviews the metabolic processes within different T-cell subsets in lupus nephritis (LN), including T follicular helper (TFH) cells, T helper (Th)17 cells, Th1 cells, Th2 cells, and Treg cells, and reveals that these cellular metabolisms not only facilitate the formation of a T-cell immune imbalance but are also closely associated with the occurrence of ferroptosis. Consequently, we hypothesize that targeting the metabolic pathways of ferroptosis could become a novel research direction for effectively treating the immune imbalance in lupus nephritis by altering T-cell differentiation and the incidence of ferroptosis.

Single-cell transcriptomics reveal potent extrafollicular B cell response linked with granzyme K+ CD8 T cell activation in lupus kidney

OBJECTIVES

B and T cells constitute the majority of infiltrating lymphocytes in the kidney and represent the local perpetrators in lupus nephritis (LN), but the underlying pathogenic mechanisms are not well elucidated. The aim of this study is to explore the kidney-specific adaptive immune landscape in patients with active LN at the single-cell level.

METHODS

We performed single-cell RNA/B cell receptor (BCR)/T cell receptor (TCR) sequencing analysis on sorting-purified B and T cells from the kidney and paired peripheral blood of patients with active LN, and the periphery of matched controls. Flow cytometry, Assay for Transposase Accessible-sequencing, multiplexed immunohistochemistry and functional studies were performed to validate the transcriptomic results.

RESULTS

High infiltrations of intrarenal atypical B cells (ABCs) and antibody-secreting cells (ASCs) were identified in the B cell compartment. The single-cell BCR repertoire analysis revealed strong clonal expansion of intrarenal ASCs dominated by IGHG1 and IGHG3 isotypes, accompanied by lower frequencies of heavy-chain and light-chain somatic mutations, compared with the peripheral ASCs. Notably, a unique expansion of IGHG4-59 and clonal overlap between ABCs and ASCs was found in kidney-specific clonotypes. In the T cell compartment, we identified granzyme K (GZMK)+ CD8 T cells as the dominant kidney-associated T cells which shared inflammation- and stress-related gene pathways with ABCs. Intrarenal GZMK+ CD8 T cells highly expressed IFNG and displayed strong communication with ABCs via the type II interferon (IFN) pathway. Intrarenal GZMK+ CD8 T cells and ABCs were largely co-localised within the tertiary lymphoid structure, and GZMK+ CD8 T cells potentially contributed to the differentiation of ABCs via IFN-γ and interleukin-21.

CONCLUSIONS

Our study revealed a potent extrafollicular B cell response linked with overactivation of GZMK+ CD8 T cells in the kidney of patients with LN, which may lead to innovative treatments for LN.

Discordant Phenotypes of Nephritis in Patients with X-linked Agammaglobulinemia

PURPOSE

To define the clinical and histological characteristics of nephritis in patients with X-linked agammaglobulinemia (XLA) and their immunological profiles.

METHODS

The clinical, immunological, and histological findings of nine patients with XLA and nephritis were retrospectively analyzed.

RESULTS

Based on kidney histological findings, patients with XLA and nephritis could be divided into two groups, viz., chronic glomerulonephritis (CGN) and tubulointerstitial nephritis (TIN). The two groups showed different immunological profiles. Patients in the CGN group exhibited an atypical immunological profile of XLA, with pathogenic leaky B cells producing immunoglobulins that may play a role in forming immune complexes and causing immune-mediated glomerulonephritis. In contrast, patients in the TIN group exhibited a typical immunological profile of XLA, suggesting that antibody-independent/other BTK-dependent mechanisms, or immunoglobulin replacement therapy (IgRT)-related immune/nonimmune-mediated nephrotoxicity causes TIN.

CONCLUSION

Nephritis occurring in patients with XLA could have links between their renal pathology and immunological status. Careful observation is recommended to detect kidney pathology in patients with XLA on IgRT.

Macrophage subpopulations in pediatric patients with lupus nephritis and other inflammatory diseases affecting the kidney

BACKGROUND

Macrophages play an important role in the pathogenesis of lupus nephritis (LN), but less is known about macrophage subtypes in pediatric LN. Here we compared renal inflammation in LN with other inflammatory pediatric kidney diseases and assessed whether inflammation correlates with clinical parameters.

METHODS

Using immunofluorescence microscopy, we analyzed renal biopsies from 20 pediatric patients with lupus nephritis (ISN/RPS classes II-V) and pediatric controls with other inflammatory kidney diseases for infiltration with M1-like (CD68 + /CD206 - , CD68 + /CD163 -), M2a-like (CD206 + /CD68 +), and M2c-like macrophages (CD163 + /CD68 +) as well as CD3 + T-cells, CD20 + B-cells, and MPO + neutrophilic granulocytes. In addition, the correlation of macrophage infiltration with clinical parameters at the time of renal biopsy, e.g., eGFR and serum urea, was investigated. Macrophage subpopulations were compared with data from a former study of adult LN patients.

RESULTS

The frequency of different macrophage subtypes in biopsies of pediatric LN was dependent on ISN/RPS class and showed the most pronounced M1-like macrophage infiltration in patients with LN class IV, whereas M2c-like macrophages were most abundant in class III and IV. Interestingly, on average, only half as many macrophages were found in renal biopsies of pediatric LN compared to adult patients with LN. The distribution of frequencies of macrophage subpopulations, however, was different for CD68 + CD206 + (M2a-like) but comparable for CD68 + CD163 - (M1-like) CD68 + CD163 + (M2c-like) cells in pediatric and adult patients. Compared to other inflammatory kidney diseases in children, fewer macrophages and other inflammatory cells were found in kidney biopsies of LN. Depending on the disease, the frequency of individual immune cell types varied, but we were unable to confirm disease-specific inflammatory signatures in our study due to the small number of pediatric cases. Worsened renal function, measured as elevated serum urea and decreased eGFR, correlated particularly strongly with the number of CD68 + /CD163 - M1-like macrophages and CD20 + B cells in pediatric inflammatory kidney disease.

CONCLUSION

Although M1-like macrophages play a greater role in pediatric LN patients than in adult LN patients, M2-like macrophages appear to be key players and are more abundant in other pediatric inflammatory kidney diseases compared to LN.

Association of regulatory T cells with renal outcomes in patients with proliferative lupus nephritis

BACKGROUND

Despite progress in the diagnosis and treatment of proliferative lupus nephritis (PLN), the prognosis remains unfavorable. Previous investigations have suggested that the deficiency of regulatory T cells (Tregs) is involved in the pathogenesis of systemic lupus erythematosus (SLE) and lupus nephritis (LN). But the prognostic value of Tregs in PLN remains controversial. This study aimed to investigate the association of Tregs with renal outcomes in patients with PLN.

METHODS

The baseline and follow-up data of patients with biopsy-proven PLN were collected in this study. All patients were divided into two groups according to whether the renal endpoint event occurred. Clinicopathologic features and therapeutic responses were compared between the two groups. Cox regression analyses curve fitting and threshold effect analysis were implemented to investigate the relationship between Tregs level and the long-term renal outcomes. The renal endpoint was defined as end-stage kidney disease (ESKD) or doubling the SCr value.

RESULTS

A total of 405 PLN patients were included. After a follow-up of 71.53 (53.13-97.47) months, 42 (10.4%) patients reached the renal endpoint. The Treg cell counts (16/μL) in the renal endpoint group were significantly decreased than that in the non-renal endpoint group (p < 0.001). Univariate and multivariate Cox regression analyses showed that the high level of Tregs was an independent protective factor for the long-term renal prognosis of PLN. Smooth curve fitting of the generalized additive mixed model analysis indicated that the risk of renal endpoint first decreased with Tregs and then slightly increased along with Treg cell levels. The segmented linear model revealed that when Treg cell counts <46/μL, the risk of renal endpoint decreased by 6.8% for every 1 μL increase in Treg levels (p = 0.0029).

CONCLUSION

Treg cell counts are closely related to the long-term renal outcomes of patients with PLN, and increasing Treg cell levels may play an important role in improving the prognosis of the kidney, but there may be a turning point (i.e., threshold effect) at the Treg cell counts that leads to directional changes in the renal outcomes.

Molecular architecture of proliferative lupus nephritis as elucidated using 50-plex imaging mass cytometry proteomics

Due to unique advantages that allow high-dimensional tissue profiling, we postulated imaging mass cytometry (IMC) may shed novel insights on the molecular makeup of proliferative lupus nephritis (LN). This study interrogates the spatial expression profiles of 50 target proteins in LN and control kidneys. Proliferative LN glomeruli are marked by podocyte loss with immune infiltration dominated by CD45RO+, HLA-DR+ memory CD4 and CD8 T-cells, and CD163+ macrophages, with similar changes in tubulointerstitial regions. Macrophages are the predominant HLA-DR expressing antigen presenting cells with little expression elsewhere, while macrophages and T-cells predominate cellular crescents. End-stage sclerotic glomeruli are encircled by an acellular fibro-epithelial Bowman's space surrounded by immune infiltrates, all enmeshed in fibronectin. Proliferative LN also shows signs indicative of epithelial to mesenchymal plasticity of tubular cells and parietal epithelial cells. IMC enabled proteomics is a powerful tool to delineate the spatial architecture of LN at the protein level.

Spatial proteomics landscape and immune signature analysis of renal sample of lupus nephritis based on laser-captured microsection

OBJECTIVE

We aimed to reveal a spatial proteomic and immune signature of kidney function regions in lupus nephritis (LN).

MATERIAL AND METHODS

The laser capture microdissection (LCM) was used to isolate the glomerulus, tubules, and interstitial of the kidney from paraffin samples. The data-independent acquisition (DIA) method was used to collect proteomics data. The bioinformatic analysis was performed.

RESULTS

A total of 49,658 peptides and 4056 proteins were quantitated. Our results first showed that a high proportion of activated NK cells, naive B cells, and neutrophils in the glomerulus, activated NK cells in interstitial, and resting NK cells were accumulated in tubules in LN. The immune-related function analysis of differential expression proteins in different regions indicated that the glomerulus and interstitial were major sites of immune disturbance and regulation connected with immune response activation. Furthermore, we identified 7, 8, and 9 hub genes in LN's glomerulus, renal interstitial, and tubules. These hub genes were significantly correlated with the infiltration of immune cell subsets. We screened out ALB, CTSB, LCN2, A2M, CDC42, VIM, LTF, and CD14, which show higher performance as candidate biomarkers after correlation analysis with clinical indexes. The function within three regions of the kidney was analyzed. The differential expression proteins (DEGs) between interstitial and glomerulus were significantly enriched in the immune-related biological processes, and myeloid leukocyte-mediated immunity and cellular response to hormone stimulus. The DEGs between tubules and glomerulus were significantly enriched in cell activation and leukocyte-mediated immunity. While the DEGs between tubules and interstitial were enriched in response to lipid, antigen processing, and presentation of peptide antigen response to oxygen-containing compound, the results indicated a different function within kidney regions.

CONCLUSIONS

Collectively, we revealed spatial proteomics and immune signature of LN kidney regions by combined using LCM and DIA.

Immune and Non-Immune Inflammatory Cells Involved in Autoimmune Fibrosis: New Discoveries

Fibrosis is an important health problem and its pathogenetic activation is still largely unknown. It can develop either spontaneously or, more frequently, as a consequence of various underlying diseases, such as chronic inflammatory autoimmune diseases. Fibrotic tissue is always characterized by mononuclear immune cells infiltration. The cytokine profile of these cells shows clear proinflammatory and profibrotic characteristics. Furthermore, the production of inflammatory mediators by non-immune cells, in response to several stimuli, can be involved in the fibrotic process. It is now established that defects in the abilities of non-immune cells to mediate immune regulation may be involved in the pathogenicity of a series of inflammatory diseases. The convergence of several, not yet well identified, factors results in the aberrant activation of non-immune cells, such as epithelial cells, endothelial cells, and fibroblasts, that, by producing pro-inflammatory molecules, exacerbate the inflammatory condition leading to the excessive and chaotic secretion of extracellular matrix proteins. However, the precise cellular mechanisms involved in this process have not yet been fully elucidated. In this review, we explore the latest discoveries on the mechanisms that initiate and perpetuate the vicious circle of abnormal communications between immune and non-immune cells, responsible for fibrotic evolution of inflammatory autoimmune 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.

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.

Excessive IL-15 promotes cytotoxic CD4 + CD28- T cell-mediated renal injury in lupus nephritis

BACKGROUND

Patients with systemic lupus erythematosus (SLE) are highly susceptible to infection and cardiovascular events, suggesting that chronic antigenic stimulation may accelerate premature aging in SLE patients. Premature aging in SLE is often accompanied with the expansion of cytotoxic CD4 + CD28-T cells. Damage caused by CD4 + CD28- T cells enhances the progressive aging of the tissue function and loss of organism's fitness. The high serum level of IL-15 has been implicated in the pathogenesis of SLE, but its role in CD4 + CD28-T cell-mediated cytotoxicity in nephritic SLE remains unclear. The aim of this study was to investigate the effect of IL-15 on functional properties and associated renal damage of cytotoxic CD4 + CD28- T cell in lupus nephritis (LN).

RESULTS

Flow cytometry showed that the number of circulating innate-like CD4 + CD28- T cells was increased in patients with nephritic SLE. Immunofluorescence showed CD4 + CD28- T cell infiltration in the kidney of LN patients, which was correlated with multiple clinicopathological features including estimated glomerular filtration rate (eGFR), proteinuria, the proportion of glomerulosclerosis and the degree of renal chronicity. In addition, a high level of IL-15 and IL15-expressing macrophage infiltration was detected in the periglomerular and intraglomerular tissues of LN patients, which enhanced the innate features, cytokine secretion and migratory capability of CD4 + CD28- T cells, and finally exerted direct TCR-independent cytotoxicity on glomerular endothelial cells in an IL-15-dependent manner in vitro.

CONCLUSION

Our study demonstrated that excessive IL-15 potentially promoted cytotoxic CD4 + CD28- T cell-mediated renal damage in LN. This finding may provide new insights into the potential association of premature aging and tissue damage in LN.

CD8+ T Cell Phenotype and Function in Childhood and Adult-Onset Connective Tissue Disease

CD8+ T cells are cytotoxic lymphocytes that destroy pathogen infected and malignant cells through release of cytolytic molecules and proinflammatory cytokines. Although the role of CD8+ T cells in connective tissue diseases (CTDs) has not been explored as thoroughly as that of other immune cells, research focusing on this key component of the immune system has recently gained momentum. Aberrations in cytotoxic cell function may have implications in triggering autoimmunity and may promote tissue damage leading to exacerbation of disease. In this comprehensive review of current literature, we examine the role of CD8+ T cells in systemic lupus erythematosus, Sjögren's syndrome, systemic sclerosis, polymyositis, and dermatomyositis with specific focus on comparing what is known about CD8+ T cell peripheral blood phenotypes, CD8+ T cell function, and CD8+ T cell organ-specific profiles in adult and juvenile forms of these disorders. Although, the precise role of CD8+ T cells in the initiation of autoimmunity and disease progression remains to be elucidated, increasing evidence indicates that CD8+ T cells are emerging as an attractive target for therapy in CTDs.

Clinicopathological significance of tubulointerstitial CD68 macrophages in proliferative lupus nephritis

OBJECTIVES

Tubulointerstitial macrophage plays a pathogenic role in renal damage of lupus nephritis (LN). However, the clinical and pathological role of these CD68 macrophages has not been fully described. The aim of the present study is to decipher the correlation between clinicopathological features and tubulointerstitial CD68 macrophages in 76 proliferative LN patients and further evaluate the prognostic significance of tubulointerstitial CD68 macrophages.

METHODS

Tubulointerstitial CD68 macrophages were quantitated by standard histochemical staining. The correlation between the number of tubulointerstitial CD68 macrophages and clinicopathological features was analyzed by Spearman's correlation analysis. Factors potentially affecting renal prognosis were further evaluated by Cox regression analysis.

RESULTS

Among the 76 proliferative LN cases, the number of CD68 macrophage infiltrates was positively correlated with serum creatinine (SCr) level, the proportion of glomeruli sclerosis and focal segmental sclerosis, tubulointerstitial inflammation, and chronicity indices, while negatively correlated with the glomerular filtration rate. During a mean follow-up period of 45 months, 5 patients (6.6%) progressed to dialysis, and 3 patents (3.9%) had a twofold increase in SCr. Multivariate Cox regression analysis showed that the number of tubulointerstitial CD68 macrophages was an independent variable associated with poor renal outcomes (HR = 1.002, P = 0.012). The optimal cutoff value of tubulointerstitial CD68 macrophages was 340/mm² in our study with 87.5% sensitivity and 61.8% specificity to predict end-stage renal disease within 4 years.

CONCLUSION

The number of tubulointerstitial CD68 macrophages was positively linked to poor prognosis of LN. Urgent immunosuppression should be considered in LN patients with abundant tubulointerstitial CD68 macrophages. Key Points • Tubulointerstitial CD68 macrophage infiltrates are positively correlated with clinicohistologic impairment in proliferative lupus nephritis. • The positive association between the number of tubulointerstitial CD68 macrophages and poor renal outcome of lupus nephritis patients were observed. • Urgent immunosuppression and monitor are required when abundant tubulointerstitial CD68 macrophage infiltrates are detected.