Relationship between renal CD68+ infiltrates and the Oxford Classification of IgA nephropathy

THE RELATIONSHIP OF MICROVASCULAR INFLAMMATION WITH ANTIBODY MEDIATED REJECTION IN KIDNEY TRANSPLANTATION

Microvascular inflammation (MVI) is a key diagnostic feature of antibody-mediated rejection (AMR), however recipients without donor specific antibodies (DSA) defy etiological classification using C4dptc and conventional DSA assignment. We evaluated MVI≥2 (Banff g+ptc≥2) using Banff 2019 AMR (independent of MVI≥2 but including C4dptc) with unconventional glomerular capillary (C4dglom) and arterial/endothelial (C4dart) immunoperoxidase detection, shared-eplet and subthreshold DSA (MFI 100-499), and capillary ultrastructure from 3398 kidney transplant samples for evidence of AMR. MVI≥2 (n=202 biopsies) from 149 kidneys (12.4% prevalence) correlated with DSA+, C4dptc+, C4dglom+, Banff cg, i, t, ti scores, serum creatinine, proteinuria, and graft failure compared with 202 propensity score matched normal controls. Laboratory reported DSA- MVI≥2 (MFI≥500) occurred in 34.7%, however subthreshold (28.6%), eplet-directed (51.4%), and/or misclassified anti-HLA DSA (12.9%) were identified in 67.1% by forensic reanalysis, with vascular C4d+ staining in 67.1%, and endothelial abnormalities in 57.1%, totalling 87.1%. Etiological analysis attributed 62.9% to AMR (77.8% for DSA- MVI≥2 with glomerulitis) and pure T cellular rejection is 37.1%. C4dptc-DSA- MVI≥2 was unrecognized AMR in 48.0%. Functional outcomes and graft survival were comparable to normal controls. We concluded that DSA- MVI≥2 frequently signified a mild "borderline" phenotype of AMR which was recognizable using novel serological and pathological techniques.

Cathepsin S (CTSS) in IgA nephropathy: an exploratory study on its role as a potential diagnostic biomarker and therapeutic target

Introduction

IgA nephropathy (IgAN), a prevalent form of glomerulonephritis globally, exhibits complex pathogenesis. Cathepsins, cysteine proteases within lysosomes, are implicated in various physiological and pathological processes, including renal conditions. Prior observational studies have suggested a potential link between cathepsins and IgAN, yet the precise causal relationship remains unclear.

Methods

We conducted a comprehensive bidirectional and multivariable Mendelian randomization (MR) study using publicly available genetic data to explore the causal association between cathepsins and IgAN systematically. Additionally, immunohistochemical (IHC) staining and enzyme-linked immunosorbent assay (ELISA) were employed to evaluate cathepsin expression levels in renal tissues and serum of IgAN patients. We investigated the underlying mechanisms via gene set variation analysis (GSVA), gene set enrichment analysis (GSEA), and immune cell infiltration analysis. Molecular docking and virtual screening were also performed to identify potential drug candidates through drug repositioning.

Results

Univariate MR analyses demonstrated a significant link between increased cathepsin S (CTSS) levels and a heightened risk of IgAN. This was evidenced by an odds ratio (OR) of 1.041 (95% CI=1.009-1.073, P=0.012) as estimated using the inverse variance weighting (IVW) method. In multivariable MR analysis, even after adjusting for other cathepsins, elevated CTSS levels continued to show a strong correlation with an increased risk of IgAN (IVW P=0.020, OR=1.037, 95% CI=1.006-1.069). However, reverse MR analyses did not establish a causal relationship between IgAN and various cathepsins. IHC and ELISA findings revealed significant overexpression of CTSS in both renal tissues and serum of IgAN patients compared to controls, and this high expression was unique to IgAN compared with several other primary kidney diseases such as membranous nephropathy, minimal change disease and focal segmental glomerulosclerosis. Investigations into immune cell infiltration, GSEA, and GSVA highlighted the role of CTSS expression in the immune dysregulation observed in IgAN. Molecular docking and virtual screening pinpointed Camostat mesylate, c-Kit-IN-1, and Mocetinostat as the top drug candidates for targeting CTSS.

Conclusion

Elevated CTSS levels are associated with an increased risk of IgAN, and this enzyme is notably overexpressed in IgAN patients' serum and renal tissues. CTSS could potentially act as a diagnostic biomarker, providing new avenues for diagnosing and treating IgAN.

IgA vasculitis nephritis: insights from kidney biopsies

PURPOSE OF REVIEW

To present findings indicating the value of kidney biopsy in assessing prognosis and guiding clinical approach to patients with IgA vasculitis nephritis (IgAVN), including a recent international study examining the value of the Oxford (MEST-C) classification.

RECENT FINDINGS

Historically, kidney biopsies with IgAVN are scored using the International Society for Kidney Diseases in Children (ISKDC) classification. However, this classification has limited prognostic value, and most biopsies fall into just two of the six ISKDC grades. There are few studies examining the clinical value of the Oxford classification, which is well documented to be predictive of kidney outcomes in IgA nephropathy, in IgAVN. However, a recent study of 361 biopsied patients with IgAVN showed that endocapillary hypercellularity (Oxford E1) predicted a subclass of patients showing initial improvement in kidney function with immunosuppressive treatment, followed by a later decline.

SUMMARY

Kidney outcome in patients with biopsied IgAVN treated with immunosuppression is determined by clinical factors and endocapillary hypercellularity. The latter is not part of the ISKDC classification and supports including MEST-C scores in biopsy reports of IgAVN. Even patients showing a good initial response to immunosuppression require long-term follow-up due to risk of subsequent kidney function decline.

Monocytes and Macrophages in Kidney Disease and Homeostasis

The monocyte-macrophage lineage of inflammatory cells is characterized by significant morphologic and functional plasticity. Macrophages have broad M1 and M2 phenotype subgroups with distinctive functions and dual reno-toxic and reno-protective effects. Macrophages are a major contributor to injury in immune-complex-mediated, as well as pauci-immune, glomerulonephritis. Macrophages are also implicated in tubulointerstitial and vascular disease, though there have not been many human studies. Patrolling monocytes in the intravascular compartment have been reported in auto-immune injury in the renal parenchyma, manifesting as acute kidney injury. Insights into the pathogenetic roles of macrophages in renal disease suggest potentially novel therapeutic and prognostic biomarkers and targeted therapy. This review provides a concise overview of the macrophage-induced pathogenetic mechanism as a background for the latest findings about macrophages' roles in different renal compartments and common renal diseases.

Prediction of treatment response in lupus nephritis using density of tubulointerstitial macrophage infiltration

Background

Lupus nephritis (LN) is a common disease with diverse clinical and pathological manifestations. A major challenge in the management of LN is the inability to predict its treatment response at an early stage. The objective of this study was to determine whether the density of tubulointerstitial macrophage infiltration can be used to predict treatment response in LN and whether its addition to clinicopathological data at the time of biopsy would improve risk prediction.

Methods

In this retrospective cohort study, 430 patients with LN in our hospital from January 2010 to December 2017 were included. We used immunohistochemistry to show macrophage and lymphocyte infiltration in their biopsy specimens, followed by quantification of the infiltration density. The outcome was the treatment response, defined as complete or partial remission at 12 months of immunosuppression.

Results

The infiltration of CD68+ macrophages in the interstitium increased in patients with LN. High levels of CD68+ macrophage infiltration in the interstitium were associated with a low probability of treatment response in the adjusted analysis, and verse vice. The density of CD68+ macrophage infiltration in the interstitium alone predicted the response to immunosuppression (area under the curve [AUC], 0.70; 95% CI, 0.63 to 0.76). The addition of CD68+cells/interstitial field to the pathological and clinical data at biopsy in the prediction model resulted in an increased AUC of 0.78 (95% CI, 0.73 to 0.84).

Conclusion

The density of tubulointerstitial macrophage infiltration is an independent predictor for treatment response in LN. Adding tubulointerstitial macrophage infiltration density to clinicopathological data at the time of biopsy significantly improves risk prediction of treatment response in LN patients.

Automated evaluation with deep learning of total interstitial inflammation and peritubular capillaritis on kidney biopsies

BACKGROUND

Interstitial inflammation and peritubular capillaritis are observed in many diseases on native and transplant kidney biopsies. A precise and automated evaluation of these histological criteria could help stratify patients' kidney prognoses and facilitate therapeutic management.

METHODS

We used a convolutional neural network to evaluate those criteria on kidney biopsies. A total of 423 kidney samples from various diseases were included; 83 kidney samples were used for the neural network training, 106 for comparing manual annotations on limited areas to automated predictions, and 234 to compare automated and visual gradings.

RESULTS

The precision, recall and F-score for leukocyte detection were, respectively, 81%, 71% and 76%. Regarding peritubular capillaries detection the precision, recall and F-score were, respectively, 82%, 83% and 82%. There was a strong correlation between the predicted and observed grading of total inflammation, as for the grading of capillaritis (r = 0.89 and r = 0.82, respectively, all P < .0001). The areas under the receiver operating characteristics curves for the prediction of pathologists' Banff total inflammation (ti) and peritubular capillaritis (ptc) scores were respectively all above 0.94 and 0.86. The kappa coefficients between the visual and the neural networks' scores were respectively 0.74, 0.78 and 0.68 for ti ≥1, ti ≥2 and ti ≥3, and 0.62, 0.64 and 0.79 for ptc ≥1, ptc ≥2 and ptc ≥3. In a subgroup of patients with immunoglobulin A nephropathy, the inflammation severity was highly correlated to kidney function at biopsy on univariate and multivariate analyses.

CONCLUSION

We developed a tool using deep learning that scores the total inflammation and capillaritis, demonstrating the potential of artificial intelligence in kidney pathology.

Key pathological features characterize minimal change disease-like IgA nephropathy

AIMS

A subset of IgA nephropathy (IgAN) patients exhibiting minimal change disease (MCD) like features present with nephrotic-range proteinuria and warrants immunosuppressive therapy (IST). However, the diagnosis of MCD-like IgAN varied by reports. We aimed to identify the key pathological features of MCD-like IgAN.

METHODS

In this cohort, 228 patients had biopsy-proven IgAN from 2009 to 2021, of which 44 without segmental sclerosis were enrolled. Patients were classified into segmental (< 50% glomerular capillary loop involvement) or global (> 50%) foot process effacement (FPE) groups. We further stratified them according to the usage of immunosuppressant therapy after biopsy. Clinical manifestations, treatment response, and renal outcome were compared.

RESULTS

26 cases (59.1%) were classified as segmental FPE group and 18 cases (40.9%) as global FPE group. The global FPE group had more severe proteinuria (11.48 [2.60, 15.29] vs. 0.97 [0.14, 1.67] g/g, p = 0.001) and had a higher proportion of complete remission (81.8% vs. 20%, p = 0.018). In the global FPE group, patients without IST experienced more rapid downward eGFR change than the IST-treated population (-0.38 [-1.24, 0.06] vs. 1.26 [-0.17, 3.20]mL/min/1.73 m2/month, p = 0.004).

CONCLUSIONS

The absence of segmental sclerosis and the presence of global FPE are valuable pathological features that assist in identifying MCD-like IgAN.

The role of mononuclear phagocyte system in IgA nephropathy: pathogenesis and prognosis

Although the "multiple hits" theory is a widely accepted pathogenesis in IgA nephropathy (IgAN), increasing evidence suggests that the mononuclear/macrophage system plays important roles in the progression of IgAN; however, the exact mechanism is unclear. In the present study, we explored 1,067 patients in 15 studies and found that the number of macrophages per glomerulus was positively related with the degree of hematuria, and the macrophages in the glomeruli were mainly related to mesangial proliferation (M) in renal biopsy. In the tubulointerstitium, macrophages were significantly paralleled to tubulointerstitial α-SMA and NF-kB expression, tubulointerstitial lesion, tubule atrophy/interstitial fibrosis (T), and segmental glomerulosclerosis (S). In the glomeruli and tubulointerstitium, M1 accounted for 85.41% in the M classification according to the Oxford MEST-C, while in the blood, M1 accounted for 100%, and the patients with low CD89⁺ monocyte mean fluorescence intensity displayed more severe pathological characteristics (S1 and T1-2) and clinical symptoms. M1 (CD80⁺) macrophages were associated with proinflammation in the acute phase; however, M2 (CD163⁺) macrophages participated in tissue repair and remodeling, which correlated with chronic inflammation. In the glomeruli, M2 macrophages activated glomerular matrix expansion by secreting cytokines such as IL-10 and tumor necrosis factor-β (TGF-β), and M0 (CD68⁺) macrophages stimulated glomerular hypercellularity. In the tubulointerstitium, M2 macrophages played pivotal roles in renal fibrosis and sclerosis. It is assumed that macrophages acted as antigen-presenting cells to activate T cells and released diverse cytokines to stimulate an inflammatory response. Macrophages infiltrating glomeruli destroy the integrity of podocytes through the mesangio-podocytic-tubular crosstalk as well as the injury of the tubule.

Urinary miR-16-5p can be used as a potential marker of endocapillary hypercellularity in IgA nephropathy

The most prevalent primary glomerulonephritis and leading cause of end-stage renal disease worldwide is IgA nephropathy (IgAN). More and more studies are describing urinary microRNA (miRNA) as a non-invasive marker for a variety of renal diseases. We screened candidate miRNAs based on data from three published IgAN urinary sediment miRNAs chips. In separate confirmation and validation cohorts, we included 174 IgAN patients, 100 patients with other nephropathies as disease controls (DC), and 97 normal controls (NC) for quantitative real-time PCR. A total of three candidate miRNAs, miR-16-5p, Let-7g-5p, miR-15a-5p were obtained. In both the confirmation and validation cohorts, these miRNAs levels were considerably higher in the IgAN than in NC, with miR-16-5p significantly higher than in DC. The area under the ROC curve for urinary miR-16-5p levels was 0.73. Correlation analysis suggested that miR-16-5p was positively correlated with endocapillary hypercellularity (r = 0.164 p = 0.031). When miR-16-5p was combined with eGFR, proteinuria and C4, the AUC value for predicting endocapillary hypercellularity was 0.726. By following the renal function of patients with IgAN, the levels of miR-16-5p were noticeably higher in the IgAN progressors than in the non- progressors (p = 0.036). Urinary sediment miR-16-5p can be used as noninvasive biomarkers for the assessment of endocapillary hypercellularity and diagnosis of IgA nephropathy. Furthermore, urinary miR-16-5p may be predictors of renal progression.

Identifying potential biomarkers for the diagnosis and treatment of IgA nephropathy based on bioinformatics analysis

BACKGROUND

IgA nephropathy (IgAN) has become the leading cause of end-stage renal disease in young adults. Nevertheless, the current diagnosis exclusively relies on invasive renal biopsy, and specific treatment is deficient. Thus, our study aims to identify potential crucial genes, thereby providing novel biomarkers for the diagnosis and therapy of IgAN.

METHODS

Three microarray datasets were downloaded from GEO official website. Differentially expressed genes (DEGs) were identified by limma package. GO and KEGG analysis were conducted. Tissue/organ-specific DEGs were distinguished via BioGPS. GSEA was utilized to elucidate the predominant enrichment pathways. The PPI network of DEGs was established, and hub genes were mined through Cytoscape. The CTD database was employed to determine the association between hub genes and IgAN. Infiltrating immune cells and their relationship to hub genes were evaluated based on CIBERSORT. Furthermore, the diagnostic effectiveness of hub markers was subsequently predicted using the ROC curves. The CMap database was applied to investigate potential therapeutic drugs. The expression level and diagnostic accuracy of TYROBP was validated in the cell model of IgAN and different renal pathologies.

RESULTS

A total of 113 DEGs were screened, which were mostly enriched in peptidase regulator activity, regulation of cytokine production, and collagen-containing extracellular matrix. Among these DEGs, 67 genes manifested pronounced tissue and organ specificity. GSEA analysis revealed that the most significant enriched gene sets were involved in proteasome pathway. Ten hub genes (KNG1, FN1, ALB, PLG, IGF1, EGF, HRG, TYROBP, CSF1R, and ITGB2) were recognized. CTD showed a close connection between ALB, IGF, FN1 and IgAN. Immune infiltration analysis elucidated that IGF1, EGF, HRG, FN1, ITGB2, and TYROBP were closely associated with infiltrating immune cells. ROC curves reflected that all hub genes, especially TYROBP, exhibited a good diagnostic value for IgAN. Verteporfin, moxonidine, and procaine were the most significant three therapeutic drugs. Further exploration proved that TYROBP was not only highly expressed in IgAN, but exhibited high specificity for the diagnosis of IgAN.

CONCLUSIONS

This study may offer novel insights into the mechanisms involved in IgAN occurrence and progression and the selection of diagnostic markers and therapeutic targets for IgAN.

High Macrophage Densities in Native Kidney Biopsies Correlate With Renal Dysfunction and Promote ESRD

Introduction

Macrophages and monocytes are main players in innate immunity. The relevance of mononuclear phagocyte infiltrates on clinical outcomes remains to be determined in native kidney diseases.

Methods

Our cross-sectional study included 324 patients with diagnostic renal biopsies comprising 17 disease entities and normal renal tissues for comparison. All samples were stained for CD68⁺ macrophages. Selected groups were further subtyped for CD14⁺ monocytes and CD163⁺ alternatively activated macrophages. Using precise pixel-based digital measurements, we quantified cell densities as positively stained areas in renal cortex and medulla as well as whole renal tissue. Laboratory and clinical data of all cases at the time of biopsy and additional follow-up data in 158 cases were accessible.

Results

Biopsies with renal disease consistently revealed higher CD68⁺-macrophage densities and CD163⁺-macrophage densities in cortex and medulla compared to controls. High macrophage densities correlated with impaired renal function at biopsy and at follow-up in all diseases and in diseases analyzed separately. High cortical CD68⁺-macrophage densities preceded shorter renal survival, defined as requirement of permanent dialysis. CD14⁺ monocyte densities showed no difference compared to controls and did not correlate with renal function.

Conclusion

Precise quantification of macrophage densities in renal biopsies may contribute to risk stratification to identify patients with high risk for end-stage renal disease (ESRD) and might be a promising therapeutic target in renal disease.

Mizoribine halts kidney fibrosis in childhood IgA nephropathy: association with modulation of M2-type macrophages

BACKGROUND

The immunosuppressant mizoribine (Miz) can reduce progression of childhood IgA nephropathy (IgAN). This study examined whether Miz affects CD163⁺ M2-type macrophages which are associated with kidney fibrosis in childhood IgAN.

METHODS

A retrospective cohort of 90 children with IgAN were divided into groups treated with prednisolone (PSL) alone (P group; n = 42) or PSL plus Miz (PM group; n = 48) for a 2-year period. Normal human monocyte-derived macrophages were stimulated with dexamethasone (Dex), or Dex plus Miz, and analyzed by DNA microarray.

RESULTS

Clinical and histological findings at first biopsy were equivalent between patients entering the P and PM groups. Both treatments improved proteinuria and haematuria, and maintained normal kidney function over the 2-year course. The P group exhibited increased mesangial matrix expansion, increased glomerular segmental or global sclerosis, and increased interstitial fibrosis at 2-year biopsy; however, the PM group showed no progression of kidney fibrosis. These protective effects were associated with reduced numbers of glomerular and interstitial CD163⁺ macrophages in the PM versus P group. In cultured human macrophages, Dex induced upregulation of cytokines and growth factors, which was prevented by Miz. Miz also inhibited Dex-induced expression of CD300E, an activating receptor which can prevent monocyte apoptosis. CD300e expression by CD163⁺ macrophages was evident in the P group, which was reduced by Miz treatment.

CONCLUSION

Miz halted the progression of kidney fibrosis in PSL-treated pediatric IgAN. This was associated with reduced CD163⁺ and CD163⁺CD300e⁺ macrophage populations, plus in vitro findings that Miz can suppress steroid-induced macrophage expression of pro-fibrotic molecules. A higher resolution version of the Graphical abstract is available as Supplementary information.

Crescents and IgA Nephropathy: A Delicate Marriage

IgA nephropathy (IgAN) is a progressive disease with great variability in the clinical course. Among the clinical and pathologic features contributing to variable outcomes, the presence of crescents has attracted particular interest as a distinct pathological feature associated with severity. Several uncontrolled observations have led to the general thought that the presence and extent of crescents was a prognostic indicator associated with poor outcomes. However, KDIGO 2021 guidelines concluded that either the presence or the relative number of crescents should not be used to determine the progression of IgAN nor should they suggest the choice of immunosuppression. Our aim is to report and discuss recent data on the debated issue of the value of active (cellular and fibrocellular) crescents in the pathogenesis and clinical progression of IgAN, their predictive value, and the impact of immunosuppression on renal function. We conclude that the value of crescents should not be disregarded, although this feature does not have an independent predictive value for progression in IgAN, particularly when considering immunosuppressed patients. An integrated overall evaluation of crescents with other active MEST scores, clinical data, and novel biomarkers must be considered in achieving a personalized therapeutic approach to IgAN patients.

Computational Analysis Reveals the Characteristics of Immune Cells in Glomerular and Tubulointerstitial Compartments in IgA Nephropathy Patients

Objective: The commonalities and differences regarding immune states between glomerular and tubulointerstitial compartments of IgA nephropathy (IgAN) remains largely undetermined. We aim to perform bioinformatic analysis for providing a comprehensive insight into the characteristics of immune cells and associated molecular mechanisms in IgAN.

Materials and Methods: We performed integrated bioinformatic analyses by using IgAN-related datasets from the Gene Expression Omnibus database. First, the differentially expressed genes (DEGs) were identified and subjected to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. Then, CIBERSORT was employed to determine the landscape of infiltrating immune cells in both glomerular and tubulointerstitial compartments of IgAN patients, followed by Pearson’s correlation analysis and principal component analysis (PCA). Finally, commonly shared DEGs between glomerular and tubulointerstitial entities were recognized, followed by correlation analyses to identify the dominant commonly shared DEGs associated with immune cell infiltration in IgAN.

Results: GO and KEGG enrichment analyses showed apparently distinct biological processes in the glomerular and tubulointerstitial compartments of IgAN. In addition, CIBERSORT analyses revealed a clear trend of increasing proportions of M1 macrophage and M2 macrophage in the glomerular compartment while noticeably higher proportions of resting CD4⁺ memory T cells and M2 macrophages in the tubulointerstitial compartments. The PCA analyses showed that the varying composition of immune cells in both glomerular and tubulointerstitial entities was compelling to distinguish IgAN patients from healthy living controls. In addition, 21 commonly shared DEGs between glomerular and tubulointerstitial entities were recognized as key regulators in the pathogenesis of IgAN, among which the enhanced hemoglobin subunit beta (HBB) gene expression was found to be positively associated with M2 macrophage in the glomerular compartment and resting CD4⁺ memory T cells in the tubulointerstitial compartment. Most importantly, FBJ murine osteosarcoma viral oncogene homolog B (FOSB) gene deficiency was recognized as the dominant alteration in promoting M2 macrophage infiltration in the glomerular compartment of IgAN.

Conclusion: The findings from our current study for the first time reveal commonalities and differences regarding immune states between glomerular and tubulointerstitial compartments, as well as decode the essential role of M2 macrophages and associated molecular patterns within the microenvironments of IgAN.

Utilizing the MEST score for prognostic staging in IgA nephropathy

Background

The Oxford classification/MEST score is an established histopathologic scoring system for patients with IgA nephropathy (IgAN). The objective of this study was to derive a prognostic model for IgAN based on the MEST score and histopathologic features.

Methods

A total of 306 patients with biopsy-proven primary IgAN were included. Histopathologic samples were retrieved from the Norwegian Kidney Biopsy Registry and reclassified according to the Oxford classification. The study endpoint was end-stage renal disease (ESRD). Patients were subclassified into three risk models based on histologic features (Model A), a composite score calculated from the adjusted hazard ratio values (Model B), and on quartiles (Model C).

Results

The mean follow-up time was 16.5 years (range 0.2–28.1). In total, 61 (20%) patients reached ESRD during the study period. Univariate analysis of M, E, S, T and C lesions demonstrated that all types were associated with an increased risk of ESRD; however, a multivariate analysis revealed that only S, T and C lesions were associated with poor outcomes. Statistical analysis of 15-year data demonstrated that Models A and B were as predictive as the MEST score, with an area-under-the-curve at 0.85. The Harrel c index values were 0.81 and 0.80 for the MEST score and Models A and B, respectively. In the present cohort, adding C lesions to the MEST score did not improve the models prognostic value.

Conclusions

Patients can be divided into risk classes based on their MEST scores. Histopathologic data provide valuable prognostic information at the time of diagnosis. Model B was the most suitable for clinical practice because it was the most user-friendly.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-021-02653-y.

Use of Glomerular CD68+ Cells as a Surrogate Marker for Endocapillary Hypercellularity in Lupus Nephritis

Introduction

Lupus nephritis (LN) class III or IV is strongly related to patient mortality and morbidity. The interobserver agreement of endocapillary hypercellularity by routine light microscopy, one of the most important lesions determining whether class III or IV is present, is moderate. In IgA nephropathy (IgAN), the presence of glomerular CD68+ cells was found to be a good surrogate marker for endocapillary hypercellularity. We investigated whether the presence of glomerular CD68+ cells could serve as a surrogate marker for endocapillary hypercellularity as well in LN.

Methods

A total of 92 LN biopsies were scored for the number of glomerular CD68+ cells using CD68 staining, including endocapillary hypercellularity and the activity index (AI). A new AI was calculated in which CD68+ cells replaced endocapillary hypercellularity. Clinical parameters were obtained from time of biopsy, 1 year after, and 2 years after.

Results

The number of glomerular CD68+ cells significantly correlated with endocapillary hypercellularity. A cutoff value of 7 for the maximum number of CD68+ cells within 1 glomerulus in a biopsy yielded a sensitivity of 88% and a specificity of 67% for the presence of endocapillary hypercellularity. Both endocapillary hypercellularity and CD68+ cells correlated with renal function during follow-up. The current and the new AI correlated equally well with the clinical outcome.

Conclusion

In LN, CD68+ cells can be used as a surrogate marker for endocapillary hypercellularity.

Intensity of Macrophage Infiltration in Glomeruli Predicts Response to Immunosuppressive Therapy in Patients with IgA Nephropathy

BACKGROUND

The lack of a tool for predicting the response to immunosuppressive therapy in IgA nephropathy (IgAN) limits patient-specific risk stratification and early treatment decision making. Models for predicting response to immunosuppression in IgAN that can be applied at the time of kidney biopsy are needed.

METHODS

This prospective cohort study involved 621 Chinese patients with IgAN who were at high risk for disease progression and had persistent proteinuria ≥1 g/d, despite 3 months of optimized supportive care with renin-angiotensin system inhibitors. Participants received immunosuppressive therapy for a median of 18 months. We used immunochemistry to identify macrophage and lymphocyte infiltrates in biopsy specimens and digital image analysis to quantify them. The outcome was response to immunosuppression, defined as complete or partial remission within 12 months of immunosuppression.

RESULTS

Kidney infiltration of CD68 + and CD206 + macrophages increased in patients with IgAN. Having higher levels of glomerular CD206 + macrophage infiltration was associated with a 40-fold increased probability of response to immunosuppression in adjusted analysis compared with having lower levels. Patients with a higher intensity of glomerular CD68 + infiltrates had a 13-fold increase in probability of responding to immunosuppression. Intensity of glomerular CD206 + and CD68 + macrophage infiltration predicted the response to immunosuppression (area under the curve [AUC], 0.84; 95% CI, 0.81 to 0.88). The AUC increased to 0.87 (95% CI, 0.84 to 0.91) in a model combining the infiltration score of CD206 + and CD68 + infiltrates with the MEST-C score and clinical data at biopsy.

CONCLUSIONS

Intensity of glomerular macrophage infiltration predicted response to immunosuppressive therapy in patients with IgAN who were at high risk of progression, and may help physicians identify patients who will benefit from such treatment.

Identification of miRNA-mRNA network and immune-related gene signatures in IgA nephropathy by integrated bioinformatics analysis

BACKGROUND

IgA nephropathy (IgAN) is the most common form of primary glomerulonephritis worldwide, and its diagnosis depends mainly on renal biopsy. However, there is no specific treatment for IgAN. Moreover, its causes and underlying molecular events require further exploration.

METHODS

The expression profiles of GSE64306 and GSE93798 were downloaded from the Gene Expression Omnibus (GEO) database and used to identify the differential expression of miRNAs and genes, respectively. The StarBase and TransmiR databases were employed to predict target genes and transcription factors of the differentially expressed miRNAs (DE-miRNAs). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were conducted to predict biological functions. A comprehensive analysis of the miRNA-mRNA regulatory network was constructed, and protein-protein interaction (PPI) networks and hub genes were identified. CIBERSORT was used to examine the immune cells in IgAN, and correlation analyses were performed between the hub genes and infiltrating immune cells.

RESULTS

Four downregulated miRNAs and 16 upregulated miRNAs were identified. Forty-five and twelve target genes were identified for the upregulated and downregulated DE-miRNAs, respectively. CDKN1A, CDC23, EGR1, HIF1A, and TRIM28 were the hub genes with the highest degrees of connectivity. CIBERSORT revealed increases in the numbers of activated NK cells, M1 and M2 macrophages, CD4 naive T cells, and regulatory T cells in IgAN. Additionally, HIF1A, CDC23, TRIM28, and CDKN1A in IgAN patients were associated with immune cell infiltration.

CONCLUSIONS

A potential miRNA-mRNA regulatory network contributing to IgAN onset and progression was successfully established. The results of the present study may facilitate the diagnosis and treatment of IgAN by targeting established miRNA-mRNA interaction networks. Infiltrating immune cells may play significant roles in IgAN pathogenesis. Future studies on these immune cells may help guide immunotherapy for IgAN patients.

Oxidative stress and macrophage infiltration in IgA nephropathy

BACKGROUND

The aim of this study was to evaluate the interactions among serum levels of galactose-deficient IgA1 (Gd-IgA1), oxidative stress and macrophage infiltration and their clinical correlates in patients with IgA Nephropathy (IgAN).

METHODS

A total of 47 patients with biopsy-proven primary IgAN, aged between 16 and 79 years, with a follow-up period ≥ 1 year or who showed progression to end stage kidney disease (ESKD) regardless the duration of follow-up were included. Study endpoint was the progression to ESKD. Serum Gd-IgA1 and advanced oxidation protein product (AOPP) levels were measured using ELISA assays. Kidney biopsies were evaluated according to the Oxford MEST-C scoring, with C4d and CD68 staining.

RESULTS

Seventeen patients (36%) experienced ESKD during a median follow-up time of 6 years (IQR 3.7-7.5). Serum AOPP levels were correlated with the intensity of glomerular C3 deposition (r = 0.325, p = 0.026), glomerular (r = 0.423, p = 0.003) and interstitial CD68 + cell count (r = 0.298, p = 0.042) and Gd-IgA1 levels (r = 0.289, p = 0.049). Serum Gd-IgA1 levels were correlated with the intensity of C3 deposition (r = 0.447, p = 0.002). eGFR at biopsy (adjusted HR (aHR) 0.979 p = 0.011), and E score (aHR, 8.305, p = 0.001) were associated with progression to ESKD in multivariate analysis. 5-year ESKD-free survival rate was significantly lower in patients with higher E score compared to patients with E score 0 [p = 0.021].

CONCLUSIONS

An increased number of macrophages in the glomerular and tubulointerstitial area may play a role in oxidative stress and complement system activation. Endocapillary hypercellularity is a predictive factor for poor prognosis in IgAN.

LncRNA CRNDE Exacerbates IgA Nephropathy Progression by Promoting NLRP3 Inflammasome Activation in Macrophages

BACKGROUND

Activation of NLRP3 inflammasome in macrophages contributes greatly to IgA nephropathy (IgAN) progression. This study intended to investigate the underlying mechanism of NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome activation in the development of IgAN.

METHODS

We examined the expression levels of colorectal neoplasia differentially expressed (CRNDE), NLRP3 inflammasome-related proteins in peripheral blood mononuclear cells (PBMCs) and J774A.1 cells and detected inflammatory cytokine levels in the serum of IgAN patients and cell supernatants of in vitro IgAN model. RNA pull-down and RNA immunoprecipitation (RIP) experiments were conducted to evaluate the interaction between CRNDE and NLRP3. Then, the ubiquitin level of NLRP3 and its binding ability to TRIM family member 31 (TRIM31) were determined.

RESULTS

Compared with the control group, the expressions of CRNDE and NLRP3 inflammasome-related proteins in PBMCs and J774A.1 cells and levels of IL-1β, TNF-α and IL-12 in serum of IgAN patients and cell supernatants of IgA-IC-induced J774A.1 cells were all increased. CRNDE silencing down-regulated NLRP3 inflammasome-related proteins and the levels of IL-1β, TNF-α and IL-12 in cell supernatants, while NLRP3 overexpression reversed these effects. Additionally, CRNDE could interact with NLRP3 and promote NLRP3 expression. Furthermore, inhibition of CRNDE reduced NLRP3 protein level and promoted TRIM31-mediated NLRP3 ubiquitination and degradation.

CONCLUSION

CRNDE exacerbates IgA nephropathy progression through restraining ubiquitination and degradation of NLRP3 and facilitating NLRP3 inflammasome activation in macrophages.

Increased Tim-3+ monocytes/macrophages are associated with disease severity in patients with IgA nephropathy

T-cell immunoglobulin and mucin-domain-containing protein-3 (Tim-3) plays multiple important roles in immune response and participates in the pathogenesis of various inflammatory diseases by regulating macrophage polarization. However, its functions in the development of IgA nephropathy (IgAN) are still unclear. In this study, changes in the relative levels of Tim-3⁺ monocytes/macrophages in peripheral blood and renal tissue, and their clinical significance in patients with IgAN were investigated. The expression of CD68 and Tim-3 in macrophages from patients with IgAN was determined via immunohistochemistry and immunofluorescence staining assays. Peripheral blood of 48 patients with biopsy-proven IgAN and 18 healthy controls (HCs) was collected to determine the frequency of circulating CD14⁺Tim-3⁺ cells using flow cytometry, before and after 24 weeks of prednisolone treatment. Serum interleukin (IL)-10 and tumor necrosis factor α (TNF-α) levels were measured using enzyme-linked immunosorbent assays. The potential association between clinical signs and Tim-3⁺ monocytes/macrophages was analyzed. The percentages of circulating CD14⁺Tim-3⁺ monocytes were higher in samples from patients with IgAN than in those from HCs and were positively associated with the pathological features (segmental glomerulosclerosis and tubular atrophy/interstitial fibrosis) of IgAN, according to the Oxford classification. Tissue staining assays revealed cells positive for both CD68 and Tim-3 in tubulointerstitial lesions of IgAN patients. In addition, elevated levels of serum IL-10 and TNF-α were detected in these patients in comparison to HCs. Furthermore, the frequency of circulating CD14⁺Tim-3⁺ monocytes had a positive correlation with levels of 24-h urinary protein and serum IL-10, and was negatively associated with renal function. After 24 weeks of treatment with prednisolone, the percentages of CD14⁺Tim-3⁺ cells were significantly reduced. In summary, our findings indicate that Tim-3⁺ monocytes/macrophages might be involved in the pathogenesisof IgAN and could be used as a potential indicator to evaluate disease severity.

Streptococcus mutans induces IgA nephropathy-like glomerulonephritis in rats with severe dental caries

The mechanisms underlying immunoglobulin A nephropathy (IgAN), the most common chronic form of primary glomerulonephritis, remain poorly understood. Streptococcus mutans, a Gram-positive facultatively anaerobic oral bacterium, is a common cause of dental caries. In previous studies, S. mutans isolates that express Cnm protein on their cell surface were frequently detected in IgAN patients. In the present study, inoculation of Cnm-positive S. mutans in the oral cavities of 2-week-old specific-pathogen free Sprague-Dawley rats fed a high-sucrose diet for 32 weeks produced severe dental caries in all rats. Immunohistochemical analyses of the kidneys using IgA- and complement C3-specific antibodies revealed positive staining in the mesangial region. Scanning electron microscopy revealed a wide distribution of electron dense deposits in the mesangial region and periodic acid-Schiff staining demonstrated prominent proliferation of mesangial cells and mesangial matrix. These results suggest that IgAN-like glomerulonephritis was induced in rats with severe dental caries by Cnm-positive S. mutans.

Macrophage interactions with collecting duct epithelial cells are capable of driving tubulointerstitial inflammation and fibrosis in immunoglobulin A nephropathy

BACKGROUND

Tubulointerstitial fibrosis is a powerful predictor of future progression inimmunoglobulin A (IgA) nephropathy (IgAN). Proximal tubular epithelial cells (PTECs), in concert with infiltrating macrophages, are regarded as the agents provocateurs for driving this fibrotic process. However, evidence is now emerging for a contributory role of the distal nephron. The aim of this study was to examine the potential influence of macrophages on collecting duct epithelial cells (CDECs) and their combined role in the progression of IgAN.

METHODS

CDECs were cultured with macrophage-conditioned media (MCM) generated from human monocyte cell lines U937 and THP-1 stimulated with or without 100 μg/mL galactose-deficient IgA1. CDECs were analysed for evidence of inflammation and fibrosis.

RESULTS

Staining of IgAN biopsies for CD68+ macrophages revealed the presence of macrophages juxtaposed to collecting ducts and within their lumina. CDEC exposed to MCM from IgA1-stimulated THP-1 cells (THP-1-IgA-MCM) exhibited markedly increased expression of neutrophil-associated gelatinase (NGAL) and proinflammatory cytokinesinterleukin (IL)-1β, tumour necrosis factor-α, IL-6 and IL-8 compared with MCM from non-IgA-stimulated THP-1 cells (THP-1-MCM). U937-IgA-MCM increased fibronectin levels and reduced E-cadherinmRNA expression. THP-1-IgA-MCM-derived exosomes induced similar increases in NGAL and cytokine expression while in cross-over experiments exosomes extracted from IL-1β-exposed CDEC induced IL-1β and IL-6 mRNA expression in both sets of macrophages. MiRnome analysis revealed that microRNA (miR)-146a, -155 and -200b exhibited a >2-fold increase in expression in CDEC treated with THP-1-IgA-MCM compared with THP-1-MCM. Enforced miR-146a suppression further enhanced NGAL expression, while ectopic miR-146a over-expression downregulated it. NGAL mRNA and miR-146a were upregulated in the biopsies of patients with progressive IgAN compared with non-progressive IgAN.

CONCLUSIONS

Taken together, these data suggest that CDEC-macrophage interactions potentially contribute to the tubulointerstitial fibrosis characteristic of progressive IgAN.

The Utility of Assessing CD68+ Glomerular Macrophages in Assessing Endocapillary Hypercellularity in IgA Nephropathy

Introduction:

IgA nephropathy (IgAN) is the most common form of glomerulonephritis across the world. Oxford classification defines criteria and effects of endocapillary hypercellularity on E score but the reproducibility of the same is debatable. Hence, there is a need for an objective marker that could establish a gold standard in assessing endocapillary hypercellularity.

Methods:

Forty biopsies of proven IgAN were taken and grouped into two groups based on the presence or absence of endocapillary hypercellularity (n = 20 each). These biopsies were then stained by CD68 immune stain and the glomerular macrophages were quantified. Mean serum creatinine, presence of hypertension, degree of proteinuria and haematuria at the time of biopsy were also recorded and the correlation between these parameters and endocapillary hypercellularity was also studied.

Results:

Mean glomerular CD 68+ cell count was significantly higher in glomeruli showing endocapillary hypercellularity. Utilising the objective cutoff values of 0.6 CD68+ per glomerulus, more than 8 glomerular CD68+ cells in the entire biopsy and/or around 4 CD68+ cells in the most inflamed glomerulus, endocapillary hypercellularity can be predicted with a sensitivity of 70–80% and specificity of 70%. After regrouping the biopsies based on the cutoff values obtained from the receiver operating curve analysis the mean urine RBC count per high power field showed a significant correlation with endocapillary hypercellularity.

Conclusion:

Glomerular CD68+ macrophage count seems to be a promising approach in assessing endocapillary hypercellularity. Further studies with emphasis on correlation with the clinical outcome are needed to validate its utility as an objective tool.

Evidences of histologic thrombotic microangiopathy and the impact in renal outcomes of patients with IgA nephropathy

INTRODUCTION

IgA nephropathy (IgAN) is the most common primary glomerulopathy worldwide. According to the Oxford Classification, changes in the kidney vascular compartment are not related with worse outcomes. This paper aims to assess the impact of thrombotic microangiopathy (TMA) in the outcomes of Brazilian patients with IgAN.

MATERIALS AND METHODS

Analysis of clinical data and kidney biopsy findings from patients with IgAN to assess the impact of TMA on renal outcomes.

RESULTS

The majority of the 118 patients included were females (54.3%); mean age of 33 years (25;43); hypertension and hematuria were observed in 67.8% and 89.8%, respectively. Median creatinine: 1.45mg/dL; eGFR: 48.8ml/min/1.73m2; 24-hour proteinuria: 2.01g; low serum C3: 12.5%. Regarding to Oxford Classification: M1: 76.3%; E1: 35.6%; S1: 70.3%; T1/T2: 38.3%; C1/C2: 28.8%. Average follow-up: 65 months. Histologic evidence of TMA were detected in 21 (17.8%) patients and those ones presented more frequently hypertension (100% vs. 61%, p <0.0001), hematuria (100% vs 87.6%, p = 0.0001), worse creatinine levels (3.8 vs. 1.38 mg/dL, p = 0.0001), eGFR (18 vs. 60 ml/min/1.73m2), p = 0.0001), low serum C3 (28.5% vs. 10.4%, p = 0.003), lower hemoglobin levels (10.6 vs. 12.7g/dL, p<0.001) and platelet counts (207,000 vs. 267,000, p = 0.001). Biopsy findings of individuals with TMA revealed only greater proportions of E1 (68% vs. 32%, p = 0.002). Individuals with TMA were followed for less time (7 vs. 65 months, p<0.0001) since they progressed more frequently to chronic kidney disease (CKD) requiring kidney replacement therapy (KRT) (71.4% vs. 21,6%, p<0.0001). Male sex, T1/T2, and TMA were independently associated with progression to CKD-KRT.

CONCLUSIONS

In this study patients with TMA had worse clinical manifestations and outcomes. In terms of histologic evidence, E1 distinguished patients with TMA from other patients. Further studies are necessary to analyze the impact of vascular lesions on IgAN prognosis.

Differentiating Staphylococcus infection-associated glomerulonephritis and primary IgA nephropathy: a mass spectrometry-based exploratory study

Staphylococcus infection-associated glomerulonephritis (SAGN) and primary IgA nephropathy (IgAN) are separate disease entities requiring different treatment approaches. However, overlapping histologic features may cause a diagnostic dilemma. An exploratory proteomic study to identify potential distinguishing biomarkers was performed on formalin fixed paraffin embedded kidney biopsy tissue, using mass spectrometry (HPLC–MS/MS) (n = 27) and immunohistochemistry (IHC) (n = 64), on four main diagnostic groups—SAGN, primary IgAN, acute tubular necrosis (ATN) and normal kidney (baseline transplant biopsies). Spectral counts modeled as a negative binomial distribution were used for statistical comparisons and in silico pathway analysis. Analysis of variance techniques were used to compare groups and the ROC curve to evaluate classification algorithms. The glomerular proteomes of SAGN and IgAN showed remarkable similarities, except for significantly higher levels of monocyte/macrophage proteins in SAGN—mainly lysozyme and S100A9. This finding was confirmed by IHC. In contrast, the tubulointerstitial proteomes were markedly different in IgAN and SAGN, with a lower abundance of metabolic pathway proteins and a higher abundance of extracellular matrix proteins in SAGN. The stress protein transglutaminase-2 (TGM2) was also significantly higher in SAGN. IHC of differentially-expressed glomerular and tubulointerstitial proteins can be used to help discriminate between SAGN and IgAN in ambiguous cases.

Severity of foot process effacement is associated with proteinuria in patients with IgA nephropathy

Background

Proteinuria is a significant risk factor for progression of IgA nephropathy (IgAN) and has a positive correlation with severity of foot process effacement (FPE). We evaluated the relationship of FPE with proteinuria and histologic characteristics, including the Oxford classification.

Methods

Patients who underwent renal biopsy and were diagnosed with IgAN at a single center were retrospectively reviewed. Patients aged less than 18 years and those with the possibility of secondary causes were excluded from the study. Subsequently, we evaluated the association between degree of proteinuria, severity of FPE, and histologic characteristics, including the Oxford classification and other immunofluorescence stains.

Results

A total of 805 cases of renal biopsy was performed at our institution, and 327 patients were diagnosed with IgAN. Among them, 82 patients were excluded. Severity of FPE had an impact on the degree of proteinuria. Notably, the group with diffuse FPE had more than about 1.3 g/day of urine protein compared to those with rare FPE. Among the histologic characteristics, M1 score and immune deposition of IgG affected severity of FPE (hazard ratios [95% confidence interval], 1.90 [1.10 to 3.26], and 3.77 [1.66 to 8.54], respectively).

Conclusion

Severity of FPE had an impact on the degree of proteinuria and may be associated with the pathogenesis of IgAN.

Live Imaging of Monocyte Subsets in Immune Complex-Mediated Glomerulonephritis Reveals Distinct Phenotypes and Effector Functions

BACKGROUND

Immune complexes within glomerular capillary walls cause crescentic GN (CrGN). Monocytes and macrophages are important in mediating CrGN, but little work has been done to phenotype the subpopulations involved and determine their respective contributions to glomerular inflammation.

METHODS

Live glomerular imaging using confocal microscopy monitored intravascular monocyte subset behavior during nephrotoxic nephritis (NTN) in a novel WKY-hCD68-GFP monocyte/macrophage reporter rat strain. Flow cytometry and qPCR further analyzed ex vivo the glomerular leukocyte infiltrate during NTN.

RESULTS

Non-classical monocytes surveyed the glomerular endothelium via lymphocyte function-associated antigen 1 (LFA-1) in the steady state. During NTN, non-classical monocytes were recruited first, but subsequent recruitment and retention of classical monocytes was associated with glomerular damage. Monocytes recruited to the glomerular vasculature did not undergo transendothelial migration. This finding suggests that inflammation in immune complex-mediated CrGN is predominantly intravascular, driven by dynamic interactions between intravascular blood monocytes and the endothelium. Glomerular endothelium and non-classical monocytes overexpressed a distinct chemokine axis, which may orchestrate inflammatory myeloid cell recruitment and expression of damage mediators. Reduced classical monocyte recruitment in Lewis rats during NTN confirmed a role for CD16 in mediating glomerular damage.

CONCLUSIONS

Monocyte subsets with distinct phenotypes and effector functions may be important in driving inflammation in experimental CrGN resulting from immune complexes formed within the glomerular capillary wall. LFA-1-dependent endothelial surveillance by non-classical monocytes may detect immune complexes through CD16, orchestrating the inflammatory response through intravascular retention of classical monocytes, which results in glomerular damage and proteinuria.

Artificial intelligence and machine learning in nephropathology

Artificial intelligence (AI) for the purpose of this review is an umbrella term for technologies emulating a nephropathologist's ability to extract information on diagnosis, prognosis, and therapy responsiveness from native or transplant kidney biopsies. Although AI can be used to analyze a wide variety of biopsy-related data, this review focuses on whole slide images traditionally used in nephropathology. AI applications in nephropathology have recently become available through several advancing technologies, including (i) widespread introduction of glass slide scanners, (ii) data servers in pathology departments worldwide, and (iii) through greatly improved computer hardware to enable AI training. In this review, we explain how AI can enhance the reproducibility of nephropathology results for certain parameters in the context of precision medicine using advanced architectures, such as convolutional neural networks, that are currently the state of the art in machine learning software for this task. Because AI applications in nephropathology are still in their infancy, we show the power and potential of AI applications mostly in the example of oncopathology. Moreover, we discuss the technological obstacles as well as the current stakeholder and regulatory concerns about developing AI applications in nephropathology from the perspective of nephropathologists and the wider nephrology community. We expect the gradual introduction of these technologies into routine diagnostics and research for selective tasks, suggesting that this technology will enhance the performance of nephropathologists rather than making them redundant.

M2a and M2b macrophages predominate in kidney tissues and M2 subpopulations were associated with the severity of disease of IgAN patients

M2 macrophages play important roles during the injury and repair phases in kidney. Our aims are to investigate the distribution of M2 subpopulations and the correlation with clinicopathological features of IgA nephropathy (IgAN) patients. In this study, renal samples from 49 IgAN patients were detected by immunofluorescence. The markers of M2 macrophages, including M2a (CD206+/CD68+), M2b (CD86+/CD68+) and M2c (CD163+/CD68+) were identified. We found M2a and M2b macrophages were the predominant subpopulations in kidney tissues of IgAN. M2a macrophages were mainly distributed in tubulointerstitium with renal lesions like segmental glomerulosclerosis and tubular atrophy/interstitial fibrosis. However, there were larger numbers of M2c in glomeruli with minor lesions. Moreover, M2a and M2c macrophages were inversely correlated with the clinical and pathologic features, respectively. These results suggest M2 subpopulations were involved in the progression of IgAN, and M2a and M2c macrophages might show different properties to participate in the pathogenesis of IgAN.