Mechanisms of immune-deposit formation and the mediation of immune renal injury

The fate of immune complexes in membranous nephropathy

The most characteristic feature of membranous nephropathy (MN) is the presence of subepithelial electron dense deposits and the consequential thickening of the glomerular basement membrane. There have been great advances in the understanding of the destiny of immune complexes in MN by the benefit of experimental models represented by Heymann nephritis. Subepithelial immune complexes are formed in situ by autoantibodies targeting native autoantigens or exogenous planted antigens such as the phospholipase A2 receptor (PLA2R) and cationic BSA respectively. The nascent immune complexes would not be pathogenic until they develop into immune deposits. Podocytes are the major source of autoantigens in idiopathic membranous nephropathy. They also participate in the modulation and removal of the immune complexes to a large extent. The balance between deposition and clearance is regulated by a wide range of factors such as the composition and physicochemical properties of the immune complexes and the complement system. Complement components such as C3 and C1q have been reported to be precipitated with the deposits whereas a complement regulatory protein CR1 expressed by podocytes is involved in the phagocytosis of immune complexes by podocytes. Podocytes regulate the dynamic change of immune complexes which is disturbed in membranous nephropathy. To elucidate the precise fate of the immune complexes is essential for developing more rational and novel therapies for membranous nephropathy.

Mitigating the Effects of Persistent Antipolymer Immune Reactions in Nanomedicine: Evaluating Materials-Based Approaches Using Molecular Imaging

Poly(ethylene glycol) (PEG) is a hydrophilic polymer ubiquitously used in both medical and nonmedical goods. Recent debate surrounding the observed stimulation of immune responses against PEG has spurred the development of materials that may be suitable replacements for this common polymeric component. The underlying view is that these alternative materials with comparable physicochemical properties can overcome the unfavorable and unpredictable effects of antibody-mediated clearance by being chemically, and therefore antigenically, distinct from PEG. However, this hypothesis has not been thoroughly tested in any defined manner, and the immune response observed against PEG has not been rigorously investigated within the context of these emerging materials. Consequently, it remains unclear whether immunity-mediated discrimination between polymeric entities even occurs in vivo and, if this is the case, how it may be exploited. In this study, we utilize positron emission tomography-computed tomography molecular imaging in mice immunized to develop specific antibody responses to PEG and an alternative polymer in order to visualize and quantify the influence of antipolymer antibodies on the biodistribution of synthetic polymers in vivo as a function of immunization status. Under the conditions of this experiment, mice could be primed to exhibit both innate and adaptive immunity to all of the polymer systems to which they were exposed. We demonstrate that alternating between chemically disparate polymers is a viable approach to extend their efficacy when antipolymer humoral immune responses arise.

Nonlupus Full House Nephropathy: A Systematic Review

Key Points

Nonlupus full house nephropathy is a rare, complex entity: confusion arises by the low-quality evidence and the lack of consensus on nomenclature. This systematic review supports that systemic lupus erythematosus and nonlupus full house nephropathy are distinct clinical entities, with comparable outcomes. The identification of three pathogenetic categories provides further clues for a shared clinical and diagnostic approach to the disease.

Background

The presence of a full house pattern at immunofluorescence on kidney biopsy in a patient without clinical and laboratory features of systemic lupus erythematosus (SLE) has led to the descriptive term nonlupus full house nephropathy. This systematic review and meta-analysis focus on nonlupus full house nephropathy nomenclature, clinical findings, and outcomes.

Methods

In a reiterative process, all identified terms for nonlupus full house nephropathy and other medical subject headings terms were searched in PubMed. Out of 344 results, 57 records published between 1982 and 2022 were included in the analysis. Clinical data of single patients from different reports were collected. Patients were classified into three pathogenetic categories, which were compared according to baseline characteristics, treatments, and outcomes.

Results

Out of the 57 records, 61% were case reports. Nonlupus full house nephropathy was addressed with 17 different names. We identified 148 patients: 75 (51%) were men; median age 35 (23–58) years. Serum creatinine and proteinuria at onset were 1.4 (0.8–2.5) mg/dl and 5.7 (2.7–8.8) g/d. About half of patients achieved complete response. A causative agent was identified in 51 patients (44%), mainly infectious (41%). Secondary nonlupus full house nephropathy was mostly nonrelapsing with worse kidney function at onset compared with idiopathic disease (P = 0.001). Among the 57 patients (50%) with idiopathic nonlupus full house nephropathy, complete response was comparable between patients treated with immunosuppression and supportive therapy; however, proteinuria and creatinine at onset were higher in patients treated with immunosuppression (P = 0.09 and P = 0.07). The remaining 7 patients (6%) developed SLE after a median follow-up of 5.0 (1.9–9.0) years.

Conclusions

Our data support that SLE and nonlupus full house nephropathy are distinct clinical entities, with comparable outcomes. A small subset of patients develops SLE during follow-up. Nonlupus full house nephropathy is addressed by many different names in the literature. The identification of three pathogenetic categories provides further clues for the management of the disease.

Liver Disease-Associated Glomerulopathies

Hepatitis B virus (HBV) and hepatitis C virus (HCV) infect a significant number of individuals globally and their extra-hepatic manifestations, including glomerular disease, are well established. Additionally, liver disease-associated IgA nephropathy is the leading cause of secondary IgA nephropathy with disease course varying from asymptomatic urinary abnormalities to progressive kidney injury. Herein we provide an updated review on the epidemiology, pathogenesis, clinical manifestations, and treatment of HBV- and HCV-related glomerulonephritis as well as IgA nephropathy in patients with liver disease. The most common HBV-related glomerulonephritis is membranous nephropathy, although membranoproliferative glomerulonephritis and podocytopathies have been described. The best described HCV-related glomerulonephritis is cryoglobulinemic glomerulonephritis occurring in about 30% of patients with mixed cryoglobulinemic vasculitis. The mainstay of treatment for HBV-GN and HCV-GN is antiviral therapy, with significant improvement in outcomes since the emergence of the direct-acting antivirals. However, cases with severe pathology and/or a more aggressive disease trajectory can be offered a course of immunosuppression, commonly anti-CD20 therapy, particularly in the case of cryoglobulinemic glomerulonephritis.

The Role of the Complement in Clear Cell Renal Carcinoma (ccRCC)-What Future Prospects Are There for Its Use in Clinical Practice?

In recent years, the first-line available therapeutic options for metastatic renal cell carcinoma (mRCC) have radically changed with the introduction into clinical practice of new immune checkpoint inhibitor (ICI)-based combinations. Many efforts are focusing on identifying novel prognostic and predictive markers in this setting. The complement system (CS) plays a central role in promoting the growth and progression of mRCC. In particular, mRCC has been defined as an "aggressive complement tumor", which encompasses a group of malignancies with poor prognosie and highly expressed complement components. Several preclinical and retrospective studies have demonstrated the negative prognostic role of the complement in mRCC; however, there is little evidence on its possible role as a predictor of the response to ICIs. The purpose of this review is to explore more deeply the physio-pathological role of the complement in the development of RCC and its possible future use in clinical practice as a prognostic and predictive factor.

Endothelial cell activation and glycocalyx shedding - potential as biomarkers in patients with lupus nephritis

Lupus nephritis (LN) is a common and severe manifestation of systemic lupus erythematosus and an important cause of acute and chronic kidney injury. Early diagnosis of LN and preventing relapses are key to preserving renal reserve. However, due to the complexity and heterogeneity of the disease, clinical management remains challenging. Kidney biopsy remains the gold standard for confirming the diagnosis of LN and subsequent assessment of kidney histopathology, but it is invasive and cannot be repeated frequently. Current clinical indicators of kidney function such as proteinuria and serum creatinine level are non-specific and do not accurately reflect histopathological changes, while anti-dsDNA antibody and C3 levels reflect immunological status but not kidney injury. Identification of novel and specific biomarkers for LN is prerequisite to improve management. Renal function deterioration is associated with changes in the endothelial glycocalyx, a delicate gel-like layer located at the interface between the endothelium and bloodstream. Inflammation induces endothelial cell activation and shedding of glycocalyx constituents into the circulation. This review discusses the potential role of soluble glycocalyx components as biomarkers of active LN, especially in patients in whom conventional serological and biochemical markers do not appear helpful.

From systemic lupus erythematosus to lupus nephritis: The evolving road to targeted therapies

Systemic lupus erythematosus is a chronic autoimmune disease characterized by loss of tolerance against nuclear and cytoplasmic self-antigens, induction of immunity and tissue inflammation. Lupus nephritis (LN), the most important predictor of morbidity in SLE, develops in almost 30% of SLE patients at disease onset and in up to 50-60% within the first 10 years. Firstly, in this review, we put the pathogenic mechanisms of the disease into a conceptual frame, giving emphasis to the role of the innate immune system in this loss of self-tolerance and the induction of the adaptive immune response. In this aspect, many mechanisms have been described such as dysregulation and acceleration of cell-death pathways, an aberrant clearance and overload of immunogenic acid-nucleic-containing debris and IC, and the involvement of antigen-presenting cells and other innate immune cells in the induction of this adaptive immune response. This result in a clonal expansion of autoreactive lymphocytes with generation of effector T-cells, memory B-cells and plasma cells that produce autoantibodies that will cause kidney damage. Secondly, we review the immunological pathways of damage in the kidney parenchyma, initiated by autoantibody binding and immune complex deposition, and followed by complement-mediated microvascular injury, activation of kidney stromal cells and the recruitment of leukocytes. Finally, we summarize the rationale for the treatment of LN, from conventional to new targeted therapies, focusing on their systemic immunologic effects and the minimization of podocytary damage.

Contactin-1 links autoimmune neuropathy and membranous glomerulonephritis

Membranous glomerulonephritis (MGN) is a common cause of nephrotic syndrome in adults, mediated by glomerular antibody deposition to an increasing number of newly recognised antigens. Previous case reports have suggested an association between patients with anti-contactin-1 (CNTN1)-mediated neuropathies and MGN. In an observational study we investigated the pathobiology and extent of this potential cause of MGN by examining the association of antibodies against CNTN1 with the clinical features of a cohort of 468 patients with suspected immune-mediated neuropathies, 295 with idiopathic MGN, and 256 controls. Neuronal and glomerular binding of patient IgG, serum CNTN1 antibody and protein levels, as well as immune-complex deposition were determined. We identified 15 patients with immune-mediated neuropathy and concurrent nephrotic syndrome (biopsy proven MGN in 12/12), and 4 patients with isolated MGN from an idiopathic MGN cohort, all seropositive for IgG4 CNTN1 antibodies. CNTN1-containing immune complexes were found in the renal glomeruli of patients with CNTN1 antibodies, but not in control kidneys. CNTN1 peptides were identified in glomeruli by mass spectroscopy. CNTN1 seropositive patients were largely resistant to first-line neuropathy treatments but achieved a good outcome with escalation therapies. Neurological and renal function improved in parallel with suppressed antibody titres. The reason for isolated MGN without clinical neuropathy is unclear. We show that CNTN1, found in peripheral nerves and kidney glomeruli, is a common target for autoantibody-mediated pathology and may account for between 1 and 2% of idiopathic MGN cases. Greater awareness of this cross-system syndrome should facilitate earlier diagnosis and more timely use of effective treatment.

Red blood cells in proliferative kidney disease-rainbow trout (Oncorhynchus mykiss) infected by Tetracapsuloides bryosalmonae harbor IgM+ red blood cells

The myxozoan parasite Tetracapsuloides bryosalmonae is the causative agent of proliferative kidney disease (PKD)-a disease of salmonid fishes, notably of the commercially farmed rainbow trout Oncorhynchus mykiss. Both wild and farmed salmonids are threatened by this virulent/deadly disease, a chronic immunopathology characterized by massive lymphocyte proliferation and hyperplasia, which manifests as swollen kidneys in susceptible hosts. Studying the immune response towards the parasite helps us understand the causes and consequences of PKD. While examining the B cell population during a seasonal outbreak of PKD, we unexpectedly detected the B cell marker immunoglobulin M (IgM) on red blood cells (RBCs) of infected farmed rainbow trout. Here, we studied the nature of this IgM and this IgM⁺ cell population. We verified the presence of surface IgM via parallel approaches: flow cytometry, microscopy, and mass spectrometry. The levels of surface IgM (allowing complete resolution of IgM^- RBCs from IgM⁺ RBCs) and frequency of IgM⁺ RBCs (with up to 99% of RBCs being positive) have not been described before in healthy fishes nor those suffering from disease. To assess the influence of the disease on these cells, we profiled the transcriptomes of teleost RBCs in health and disease. Compared to RBCs originating from healthy fish, PKD fundamentally altered RBCs in their metabolism, adhesion, and innate immune response to inflammation. In summary, RBCs play a larger role in host immunity than previously appreciated. Specifically, our findings indicate that the nucleated RBCs of rainbow trout interact with host IgM and contribute to the immune response in PKD.

Predicting diagnostic gene expression profiles associated with immune infiltration in patients with lupus nephritis

Objective

To identify potential diagnostic markers of lupus nephritis (LN) based on bioinformatics and machine learning and to explore the significance of immune cell infiltration in this pathology.

Methods

Seven LN gene expression datasets were downloaded from the GEO database, and the larger sample size was used as the training group to obtain differential genes (DEGs) between LN and healthy controls, and to perform gene function, disease ontology (DO), and gene set enrichment analyses (GSEA). Two machine learning algorithms, least absolute shrinkage and selection operator (LASSO) and support vector machine-recursive feature elimination (SVM-RFE), were applied to identify candidate biomarkers. The diagnostic value of LN diagnostic gene biomarkers was further evaluated in the area under the ROC curve observed in the validation dataset. CIBERSORT was used to analyze 22 immune cell fractions from LN patients and to analyze their correlation with diagnostic markers.

Results

Thirty and twenty-one DEGs were screened in kidney tissue and peripheral blood, respectively. Both of which covered macrophages and interferons. The disease enrichment analysis of DEGs in kidney tissues showed that they were mainly involved in immune and renal diseases, and in peripheral blood it was mainly enriched in cardiovascular system, bone marrow, and oral cavity. The machine learning algorithm combined with external dataset validation revealed that C1QA(AUC = 0.741), C1QB(AUC = 0.758), MX1(AUC = 0.865), RORC(AUC = 0.911), CD177(AUC = 0.855), DEFA4(AUC= 0.843)and HERC5(AUC = 0.880) had high diagnostic value and could be used as diagnostic biomarkers of LN. Compared to controls, pathways such as cell adhesion molecule cam, and systemic lupus erythematosus were activated in kidney tissues; cell cycle, cytoplasmic DNA sensing pathways, NOD-like receptor signaling pathways, proteasome, and RIG-1-like receptors were activated in peripheral blood. Immune cell infiltration analysis showed that diagnostic markers in kidney tissue were associated with T cells CD8 and Dendritic cells resting, and in blood were associated with T cells CD4 memory resting, suggesting that CD4 T cells, CD8 T cells and dendritic cells are closely related to the development and progression of LN.

Conclusion

C1QA, C1QB, MX1, RORC, CD177, DEFA4 and HERC5 could be used as new candidate molecular markers for LN. It may provide new insights into the diagnosis and molecular treatment of LN in the future.

Overexpressed angiotensin-converting enzyme in neutrophils suppresses glomerular damage in crescentic glomerulonephritis

While angiotensin-converting enzyme (ACE) regulates blood pressure by producing angiotensin II as part of the renin-angiotensin system, we recently reported that elevated ACE in neutrophils promotes an effective immune response and increases resistance to infection. Here, we investigate if such neutrophils protect against renal injury in immune complex (IC)-mediated crescentic glomerulonephritis (GN) through complement. Nephrotoxic serum nephritis (NTN) was induced in wild-type and NeuACE mice that overexpress ACE in neutrophils. Glomerular injury of NTN in NeuACE mice was attenuated with much less proteinuria, milder histological injury, and reduced IC deposits, but presented with more glomerular neutrophils in the early stage of the disease. There were no significant defects in T and B cell functions in NeuACE mice. NeuACE neutrophils exhibited enhanced IC uptake with elevated surface expression of FcγRII/III and complement receptor CR1/2. IC uptake in neutrophils was enhanced by NeuACE serum containing elevated complement C3b. Given no significant complement activation by ACE, this suggests that neutrophil ACE indirectly preactivates C3 and that the C3b-CR1/2 axis and elevated FcγRII/III play a central role in IC elimination by neutrophils, resulting in reduced glomerular injury. The present study identified a novel renoprotective role of ACE in glomerulonephritis; elevated neutrophilic ACE promotes elimination of locally formed ICs in glomeruli via C3b-CR1/2 and FcγRII/III, ameliorating glomerular injury.NEW & NOTEWORTHY We studied immune complex (IC)-mediated crescentic glomerulonephritis in NeuACE mice that overexpress ACE only in neutrophils. Such mice show no significant defects in humoral immunity but strongly resist nephrotoxic serum nephritis (less proteinuria, milder histological damage, reduced IC deposits, and more glomerular neutrophils). NeuACE neutrophils enhanced IC uptake via increased surface expression of CR1/2 and FcgRII/III, as well as elevated serum complement C3b. These results suggest neutrophil ACE as a novel approach to reducing glomerulonephritis.

Validation of a method to analyze size distribution of crovalimab-complement C5-eculizumab complexes in human serum

Background: Crovalimab is a humanized monoclonal antibody targeting human complement C5. Patients switching from eculizumab to crovalimab are expected to form drug-target-drug complexes (DTDCs), since these antibodies each bind to a different epitope on complement C5. An analytical method to evaluate the size distribution of these DTDCs was developed and validated. Methods: Human serum samples were separated by size-exclusion chromatography (SEC) into eight fractions, and the concentration of crovalimab in each fraction was measured by ELISA. We evaluated SEC, ELISA and the combination of both methods (SEC-ELISA). Results: Predetermined validation acceptance criteria were met. Conclusion: The DTDC assay method was successfully validated. It enables us to evaluate the impact of DTDCs on clinical outcomes.

Establishment and clinical application of an assay for the activity of circulating immune complexes using human O-erythrocytes as an indicator system

OBJECTIVE

To develop a suitable clinical laboratory assay for detecting the activity of circulating immune complexes (CICs) that activate complement (ACIC).

METHODS

CICs measured in serum were initially used to activate complement, and the remaining complement was activated through sensitized human O-erythrocytes. ACIC was quantified by the degree of hemolysis. Each serum sample was tested for ten consecutive days to determine its stability. Reference ranges are suggested. ACIC was measured in both healthy individuals and patients with autoimmune diseases as well.

RESULTS

The OD values of the hemolysis degree index were inversely proportional to ACIC (r=0.986, P=0.002). A pooled serum was used to eliminate interference and optimize the experiment. The hemolysis degree (HD) was used to indicate the detection result. HD = (detection value OD/negative value OD)*100. The inter-batch results showed good stability with a CV of 6.5%. HD differences between males and females were significant (P=0.015) while the normal distribution for both genders was conformed. The HD recommended reference range for men is 56-88 while for women is 51-86. Serum HD of healthy subjects and autoimmune disease patients showed a significant difference (P=0.001). Autoimmune disease patients have higher HD which was a result of having stronger ACIC.

CONCLUSION

The ACIC assay while utilizing human O-erythrocytes as an indicator system is sensitive and accurate, and has potential in clinical applications.

Lupus nephritis correlates with B cell interferon-β, anti-Smith, and anti-DNA: a retrospective study

Background

In systemic lupus erythematosus (SLE), detection of interferon-β (IFNβ) in B cells was found to be most prominent in patients with high anti-Smith (Sm) and renal disease, but a mechanistic connection was not clear. The objective of the present study is to determine the association of IFNβ in peripheral blood naïve B cells with the histopathological features of lupus nephritis (LN).

Methods

The percentage of IFNβ⁺ cells in IgD⁺CD27⁻ naïve CD19⁺ B cells (B cell IFNβ) among peripheral blood mononuclear cells (PBMCs) from 80 SLE patients were analyzed using flow cytometry. Serological and clinical data were collected. The correlations of B cell IFNβ with LN classification and with histopathological findings (light, electron, and immunofluorescence [IF] microscopic analyses for deposition of IgM, IgG, IgA, C1q, and C3) were determined in 23 available biopsy specimens.

Results

B cell IFNβ is positively associated with anti-Sm (p = 0.001), anti-DNA (p = 0.013), and LN (p < 0.001) but was negatively associated with oral/nasal ulcer (p = 0.003) and photosensitivity (p = 0.045). B cell IFNβ positively correlated with immune complex (IC) deposit in the glomerular basement membrane (GBM) (p = 0.002) but not in the mesangial (p = 0.107) or tubular region (p = 0.313). Patients with high B cell IFNβ had statistically increased development of the proliferative LN (Classes III, IV and/or V), compared to patients with low B cell IFNβ (p < 0.0001). Histopathological features positively associated with increased B cell IFNβ included active glomerular lesions as determined by fibrocellular crescents (p = 0.023), chronic glomerular lesions indicated by segmental sclerosis (p = 0.033), and a membranous pattern of renal damage indicated by spike/holes (p = 0.015).

Conclusion

B cell IFNβ correlates with history of severe LN, glomerular basement membrane (GBM) IC deposition, and anatomical features of both active and chronic glomerular lesions.

The spectrum of renal diseases with lupus-like features: a single-center study

Background

A subset of patients without overt systemic lupus erythematosus (SLE) present with biopsy findings typically seen in lupus nephritis (LN). Although a minority eventually develops SLE, many do not. It remains unclear how to classify or treat these patients. Our study attempted to further understand the clinical and pathological characteristics of cases with lupus-like nephritis (LLN).

Methods

Among 2700 native kidney biopsies interpreted at University of Rochester Medical Center (URMC) from 2010 to 2019, we identified 27 patients with biopsies showing lupus-like features (LL-fx) and 96 with LN. Of those with LL-fx, 17 were idiopathic LLN and 10 were associated with a secondary etiology (e.g., infection/drugs).

Results

At the time of biopsy, the LLN-group tended to be slightly older (44 vs. 35), male (58.8 vs. 17.7%, p = .041), and Caucasian (47.0 vs. 28.1%, p = .005). Chronic kidney disease was the most common biopsy indication in LLN (21.4 vs. 2.8%, p = .001). Both LN and LLN presented with nephrotic-range proteinuria (mean 5.73 vs. 4.40 g/d), and elevated serum creatinine (mean 1.66 vs. 1.47 mg/dL). Tubuloreticular inclusions (TRIs; p < .001) and fibrous crescents (p = .04) were more often seen in LN, while more tubulointerstitial scarring was seen in LLN (p = .011). At mean follow-up of 1684 d (range: 31–4323), none of the LLN patients developed ESRD. A subset of both LN and cases with LL-fx overlapped with other autoimmune diseases.

Conclusions

Lupus-like pathologic features are seen in a wide array of disease processes. The findings suggest that LLN may be a manifestation of an autoimmune process that overlaps with SLE.

Positron emission tomography and single photon emission computed tomography imaging of tertiary lymphoid structures during the development of lupus nephritis

Lymphoid neogenesis occurs in tissues targeted by chronic inflammatory processes, such as infection and autoimmunity. In systemic lupus erythematosus (SLE), such structures develop within the kidneys of lupus-prone mice ((NZBXNZW)F1) and are observed in kidney biopsies taken from SLE patients with lupus nephritis (LN). The purpose of this prospective longitudinal animal study was to detect early kidney changes and tertiary lymphoid structures (TLS) using in vivo imaging. Positron emission tomography (PET) by tail vein injection of 18-F-fluoro-2-deoxy-D-glucose (¹⁸F-FDG)(PET/FDG) combined with computed tomography (CT) for anatomical localization and single photon emission computed tomography (SPECT) by intraperitoneal injection of ^99mTC labeled Albumin Nanocoll (^99mTC-Nanocoll) were performed on different disease stages of NZB/W mice (n = 40) and on aged matched control mice (BALB/c) (n = 20). By using one-way ANOVA analyses, we compared two different compartmental models for the quantitative measure of ¹⁸F-FDG uptake within the kidneys. Using a new five-compartment model, we observed that glomerular filtration of ^18FFDG in lupus-prone mice decreased significantly by disease progression measured by anti-dsDNA Ab production and before onset of proteinuria. We could not visualize TLS within the kidneys, but we were able to visualize pancreatic TLS using ^99mTC Nanocoll SPECT. Based on our findings, we conclude that the five-compartment model can be used to measure changes of FDG uptake within the kidney. However, new optimal PET/SPECT tracer administration sites together with more specific tracers in combination with magnetic resonance imaging (MRI) may make it possible to detect formation of TLS and LN before clinical manifestations.

A link between IL-23 and anti-CD4 autoantibody production in antiretroviral-treated HIV-infected individuals

Potential mechanisms of poor CD4+ T cell reconstitution after viral suppression with antiretroviral therapy (ART) in HIV disease have been extensively investigated. We recently discovered that anti-CD4 autoantibody plays a role in impaired CD4+ T cell recovery from ART in HIV-infected individuals with viral suppression, which accounts for a mechanism specific for CD4+ T cell depletion. However, the mechanism of pathologic anti-CD4 autoantibody production in treated HIV disease remains unknown. Here we report that seasonal influenza vaccination induced IgG anti-CD4 autoantibodies, predominant IgG3 subclass, in some viral-suppressed ART-treated HIV+ subjects. To explore the mechanism of anti-CD4 antibody production in this population, we performed and analyzed gene profiles in isolated B cells using a gene microarray and plasma 32 cytokines. Notably, both gene expression and multiple cytokine analyses showed pre-vaccination plasma level of IL-23 was the key cytokine linked to IgG anti-CD4 antibody production in response to immunization in vivo Exogenous rIL-23 increased autoreactive IgG binding on CD4+ T cells from HIV+ subjects in vitro Results from this study may reveal a role of IL-23 in anti-CD4 autoantibody production in treated HIV.IMPORTANCEIn our published studies, we determine that pathological anti-CD4 IgGs from immunologic non-responders on virally-suppressive ART (CD4 cell counts < 350 cells/μL) mediated CD4+ T cell death via antibody-mediated cytotoxicity (ADCC), which play a role in poor CD4+ T cell recovery from ART. Up to 25% of HIV-infected individuals are non-responders and demonstrate increased morbidity and mortality. However, the mechanism of anti-CD4 autoantibody production in treated HIV remains unknown. In this study, we report that IL-23 may be the key cytokine to promote anti-CD4 autoantibody production after immunization in ART-treated HIV-infected individuals.

IFN-I Mediates Lupus Nephritis From the Beginning to Renal Fibrosis

Lupus nephritis (LN) is a common complication of systemic lupus erythematosus (SLE) and a major risk factor for morbidity and mortality. The abundant cell-free nucleic (DNA/RNA) in SLE patients, especially dsDNA, is a key substance in the pathogenesis of SLE and LN. The deposition of DNA/RNA-immune complexes (DNA/RNA-ICs) in the glomerulus causes a series of inflammatory reactions that lead to resident renal cell disturbance and eventually renal fibrosis. Cell-free DNA/RNA is the most effective inducer of type I interferons (IFN-I). Resident renal cells (rather than infiltrating immune cells) are the main source of IFN-I in the kidney. IFN-I in turn damages resident renal cells. Not only are resident renal cells victims, but also participants in this immunity war. However, the mechanism for generation of IFN-I in resident renal cells and the pathological mechanism of IFN-I promoting renal fibrosis have not been fully elucidated. This paper reviews the latest epidemiology of LN and its development process, discusses the mechanism for generation of IFN-I in resident renal cells and the role of IFN-I in the pathogenesis of LN, and may open a new perspective for the treatment of LN.

Role of Circulating Immune Complexes in the Pathogenesis of Canine Leishmaniasis: New Players in Vaccine Development

During canine visceral leishmaniasis (CanL), due to Leishmania infantum (L. infantum), uncontrolled infection leads to a strong humoral immune response. As a consequence of the production of high antibody levels and the prolonged presence of parasite antigens, circulating immune complexes (CIC) are formed, which can be deposited in certain organs and tissues, inducing vasculitis, uveitis, dermatitis and especially glomerulonephritis and renal failure. A method to detect CIC and quantify their levels in serum samples from dogs infected with L. infantum has been recently described. It allowed demonstration of a correlation between CIC levels and disease severity. Thus, CIC measurement may be useful for diagnosis, assessment of disease progression and monitoring response to treatment. This is an interesting finding, considering that there remains an urgent need for identification of novel biomarkers to achieve a correct diagnosis and for optimal disease staging of dogs suffering from Leishmania infection. The objective of the present review is to shed light on the role of CIC in CanL, as well as to highlight their potential use not only as diagnostic and prognostic biomarkers but also as a valuable tool in vaccine development and new immunotherapy strategies to prevent or control disease outcome.

Monoclonal and polyclonal immunoglobulin G deposits on tubular basement membranes of native and pretransplant kidneys: A retrospective study

Monoclonal tubular basement membrane immune deposits (TBMID) are associated with progression of interstitial injury in renal allograft. However, the significance of monoclonal and polyclonal TBMID in the native kidney remains unclear. We retrospectively analyzed 1894 native kidney biopsies and 1724 zero-hour biopsies performed between 2008 and 2018 in our institution. The rate of immunoglobulin G (IgG) TBMID was found to be 8.4% among native kidney biopsies and 0.4% among zero-hour biopsies. Polyclonal TBMID is common in IgG4-related tubulointerstitial nephritis (37.5%), diabetic nephropathy (31.3%) and lupus nephritis (25.5%). Monoclonal IgG TBMID was identified in seven cases, including three zero-hour biopsies. The combination of IgG1κ was observed in two cases, IgG1λ in three, and IgG2κ in two. Electron microscopy revealed powdery electron-dense deposits in all cases. Monoclonal gammopathy of undetermined significance was diagnosed in one case. Although one patient with focal segmental glomerulosclerosis developed renal failure, all others exhibited stable renal function. Monoclonal IgG TBMID in the native kidney is not associated with renal prognosis. However, this may be an interesting immunopathological finding that would help clarify the pathogenesis of TBM immune deposits. Further study for both monoclonal and polyclonal TBMID is required in the future.

Searching for Potential Markers of Glomerulopathy in Urine by HS-SPME-GC×GC TOFMS

Volatile organic compounds (VOCs) exiting in urine are potential biomarkers of chronic kidney diseases. Headspace solid phase microextraction (HS-SPME) was applied for extraction VOCs over the urine samples. Volatile metabolites were separated and identified by means of two-dimensional gas chromatography and time of flight mass spectrometry (GC × GC TOF MS). Patients with glomerular diseases (n = 27) and healthy controls (n = 20) were recruited in the study. Different VOCs profiles were obtained from patients and control. Developed methodology offers the opportunity to examine the metabolic profile associated with glomerulopathy. Four compounds found in elevated amounts in the patients group, i.e., methyl hexadecanoate; 9-hexadecen-1-ol; 6,10-dimethyl-5,9-undecadien-2-one and 2-pentanone were proposed as markers of glomerular diseases.

Investigation of immune complexes formed by mitochondrial antigens containing a new lipoylated site in sera of primary biliary cholangitis patients

Primary biliary cholangitis (PBC) is characterized by the presence of serum anti-mitochondrial autoantibodies (AMAs). To date, four antigens among the 2-oxo-acid dehydrogenase complex family, which commonly have lipoyl domains as an epitope, have been identified as AMA-corresponding antigens (AMA-antigens). It has recently been reported that AMAs react more strongly with certain chemically modified mimics than with the native lipoyl domains in AMA-antigens. Moreover, high concentrations of circulating immune complexes (ICs) in PBC patients have been reported. However, the existence of ICs formed by AMAs and their antigens has not been reported to date. We hypothesized that AMAs and their antigens formed ICs in PBC sera, and analyzed sera of PBC and four autoimmune diseases (Sjögren's syndrome, systemic lupus erythematosus, systemic scleroderma, and rheumatoid arthritis) using immune complexome analysis, in which ICs are separated from serum and are identified by nano-liquid chromatography-tandem mass spectrometry. To correctly assign MS/MS spectra to peptide sequences, we used a protein-search algorithm that including lipoylation and certain xenobiotic modifications. We found three AMA-antigens, the E2 subunit of the pyruvate dehydrogenase complex (PDC-E2), the E2 subunit of the 2-oxo-glutarate dehydrogenase complex (OGDC-E2) and dihydrolipoamide dehydrogenase binding protein (E3BP), by detecting peptides containing lipoylation and xenobiotic modifications from PBC sera. Although the lipoylated sites of these peptides were different from the well-known sites, abnormal lipoylation and xenobiotic modification may lead to production of AMAs and the formation ICs. Further investigation of the lipoylated sites, xenobiotic modifications, and IC formation will lead to deepen our understanding of PBC pathogenesis.

Lupus Membranous Nephropathy

Background

Lupus membranous nephropathy (LMN) is a rare disease, usually associated with nephrotic syndrome.

Methods

We reviewed the literature by searching for the following terms on Pubmed.gov: lupus nephritis, membranous nephropathy (MN), lupus membranous nephropathy, nephrotic syndrome, and Class V lupus nephritis.

Results

The histology of LMN at light microscopy is similar to that of primary MN. Cases of MN associated with focal or diffuse proliferation are not considered LMN by the International Society of Nephrology/Renal Pathology Society classification. Immunofluorescence study of LMN shows deposits of all immunoglobulins and complement. Tubulo-reticular structures, extraglomerular deposits, subepithelial, and scanty subendothelial deposits can be seen on electron microscopy. Phospholipase A2 receptor deposits are usually but not necessarily absent in LMN. The pathogenesis is still not completely understood. The inflammatory milieu of lupus may favor the development of autoantigens and intraglomerular assembly of immune complexes. These are more often associated with mesangial or endocapillary hypercellular lesions. Alternatively, autoantibodies may bind autoantigens in the glomerular subepithelium, triggering a signaling cascade leading to LMN. A central role in the development of podocyte injury and proteinuria is played by the components of complement C5b-C9. CKD progression in LMN is slow but may be accelerated by the frequency of renal flares. Persistent nephrotic syndrome and/or the frequent use of corticosteroids may lead to a series of life-threatening complications.

Discussion

Treatment of arterial hypertension, dyslipidemia, and diabetes are of paramount importance. Besides specific therapies of these complications, hydroxychloroquine and vitamin D supplementation are recommended. Immunosuppression should be limited to patients with nephrotic proteinuria. The most frequently used drugs are corticosteroids, calcineurin inhibitors, cyclophosphamide, mycophenolate, and rituximab, alone or combined. Early detection and treatment of renal flares is of paramount importance to prevent CKD progression.

The Crucial Role of PPARγ-Egr-1-Pro-Inflammatory Mediators Axis in IgG Immune Complex-Induced Acute Lung Injury

Background

The ligand-activated transcription factor peroxisome proliferator-activated receptor (PPAR) γ plays crucial roles in diverse biological processes including cellular metabolism, differentiation, development, and immune response. However, during IgG immune complex (IgG-IC)-induced acute lung inflammation, its expression and function in the pulmonary tissue remains unknown.

Objectives

The study is designed to determine the effect of PPARγ on IgG-IC-triggered acute lung inflammation, and the underlying mechanisms, which might provide theoretical basis for therapy of acute lung inflammation.

Setting

Department of Pathogenic Biology and Immunology, Medical School of Southeast University

Subjects

Mice with down-regulated/up-regulated PPARγ activity or down-regulation of Early growth response protein 1 (Egr-1) expression, and the corresponding controls.

Interventions

Acute lung inflammation is induced in the mice by airway deposition of IgG-IC. Activation of PPARγ is achieved by using its agonist Rosiglitazone or adenoviral vectors that could mediate overexpression of PPARγ. PPARγ activity is suppressed by application of its antagonist GW9662 or shRNA. Egr-1 expression is down-regulated by using the gene specific shRNA.

Measures and Main Results

We find that during IgG-IC-induced acute lung inflammation, PPARγ expression at both RNA and protein levels is repressed, which is consistent with the results obtained from macrophages treated with IgG-IC. Furthermore, both in vivo and in vitro data show that PPARγ activation reduces IgG-IC-mediated pro-inflammatory mediators’ production, thereby alleviating lung injury. In terms of mechanism, we observe that the generation of Egr-1 elicited by IgG-IC is inhibited by PPARγ. As an important transcription factor, Egr-1 transcription is substantially increased by IgG-IC in both in vivo and in vitro studies, leading to augmented protein expression, thus amplifying IgG-IC-triggered expressions of inflammatory factors via association with their promoters.

Conclusion

During IgG-IC-stimulated acute lung inflammation, PPARγ activation can relieve the inflammatory response by suppressing the expression of its downstream target Egr-1 that directly binds to the promoter regions of several inflammation-associated genes. Therefore, regulation of PPARγ-Egr-1-pro-inflammatory mediators axis by PPARγ agonist Rosiglitazone may represent a novel strategy for blockade of acute lung injury.

Rituximab for the management of idiopathic membranous nephropathy: a meta-analysis

PURPOSE

The aim of this study was to evaluate the efficacy of rituximab therapy in the management of idiopathic membranous nephropathy (IMN).

METHODS

After literature search, data from eligible studies were used to perform random-effects meta-analyses to estimate remission rates and changes in proteinuria at the latest follow-up after rituximab therapy. The outcomes were used for metaregression to identify the factors affecting the efficacy of rituximab.

RESULTS

Twenty-one studies were included in the analysis (602 patients; age 50 years [95% CI 46.8, 53.3]; 30% females [95% CI 23, 31]). Follow-up duration was 20.3 months [95% CI 17.1, 23.5]. Remission rate (67% [95% CI 61, 73]) was higher in studies with below average baseline proteinuria (76% [95% CI 61, 88]) than in studies with above average baseline proteinuria (61% [95% CI 54, 68]). The complete and partial remission rates were 26% [95% CI 20, 33] and 37% [95% CI 31, 43], respectively. Rituximab therapy significantly reduced proteinuria (mean difference between final and baseline values: - 4.90 g/day [95% CI - 6.18, - 3.63]; p < 0.00001; % reduction: 62% [95% CI 57, 68]). The reduction in proteinuria was inversely associated with baseline serum albumin levels (p = 0.021) and the estimated glomerular filtration rate (p < 0.00001) and was positively associated with baseline proteinuria (p < 0.00001). The remission rate or decrease in proteinuria was not significantly related to the anti-PLA₂R antibody status or previous immunosuppressant therapy.

CONCLUSION

Rituximab therapy in IMN patients can provide approximately 67% remission rate. The reduction in proteinuria was greater in patients who had higher baseline proteinuria.

Progress in Pathogenesis of Immunoglobin A Nephropathy

The understanding of the pathogenesis of any disease is the key to effective and specific treatment of the disease. immunoglobulin A (IgA) nephropathy is an autoimmune disease of the kidney. Oxford MEST classification is commonly used to stratify patients according to the severity of the disease. Patients with IgA nephropathy seem to produce anti-GalNAc antibodies against a particularly defective IgA1. This immune complex deposits in the kidneys, leading to a type 3 hypersensitivity reaction which ultimately damages the kidneys. People of a certain genetic background and who experience upregulation of certain defective receptors seem to develop primary IgA nephropathy. Secondary IgA nephropathy could be due to dysbiosis of the microbiota in the gut, compromised gut immunity or other gut pathologies, pulmonary function abnormalities, or amyloidosis. Overproduction of IgA due to plasma cell dyscrasia or reduced clearance of IgA due to liver abnormalities could also be potential causes. Genes that predispose individuals to IgA nephropathy and intestinal abnormalities, such as Celiac disease, seem to overlap and these people tend to have a poorer prognosis and need to be placed on more intensive treatment regimens. IgA Vasculitis seems to be a systemic form of IgA nephropathy, whereby IgA deposits systemically and leads to multiple disease manifestations. Patients in high-risk groups could also be prophylactically screened for the disease and closely monitored by immunohistochemical methods such as an enzyme-linked immunosorbent assay (ELISA) or identified by genetic testing. Currently, the major treatment regimens involve supportive therapy or immunosuppressive therapy which has major side effects. More specific treatment methods such as monoclonal antibodies, immunoglobulin replacement therapy, or low-antigen-content diet could also be looked into as potential treatment options. Stem cell replacement, by way of bone marrow transplant and tonsillectomy, has been suggested as a treatment option in patients with indications.

Monoclonal immunoglobulin G deposits on tubular basement membrane in renal allograft: is this significant for chronic allograft injury?

Background

Tubular basement membrane immune deposits (TBMID) has rarely been observed in renal allografts. It is usually found in BK virus nephropathy and immune complex glomerulonephritis; however, its significance is not well understood. We conducted a retrospective clinicopathological study on monoclonal immunoglobulin G (IgG) TBMID.

Methods

We studied 7177 renal allograft biopsy specimens obtained from Tokyo Women’s Medical University from 2007 to 2015 and performed light microscopic, electron microscopic and immunofluorescence studies.

Results

Tubular basement membrane (TBM) deposits of IgG were found in 73 biopsies from 61 patients and the IgG subclass was obtained in 31 biopsies. There were no cases of monoclonal IgA or IgM TBMID. In total, 13 biopsies from 10 patients showed monoclonal IgG TBMID. Of these, seven showed monoclonal IgG1κ TBMID and one each showed monoclonal IgG2κ, IgG2λ and IgG3κ TBMID. Conversely, eight patients showed polyclonal IgG TBMID. In electron microscopy, large granular electron-dense deposits (EDDs) in the TBM were detected in all patients with monoclonal IgG1κ TBMID. EDDs were absent in TBM in patients with monoclonal IgG2κ, IgG2λ or IgG3κ TBMID. Progression of interstitial fibrosis and tubular atrophy (IFTA) was significantly higher in patients with monoclonal IgG1κ TBMID than in those with polyclonal IgG TBMID (P < 0.05). There were no significant differences in the other clinical parameters between monoclonal IgG1κ and polyclonal IgG TBMID.

Conclusions

This is the first study of patients with monoclonal IgG TBMID in renal allografts. We found that monoclonal IgG1κ TBMID was associated with EDD formation in TBM and IFTA progression.

Revisiting immune complexes: Key to understanding immune-related diseases

Immune complexes (ICs) formed by foreign or self-antigens and antibodies in biological fluids affect various tissues and are thought to cause several diseases. Biological and physical properties of IC, abnormal IC amounts, IC deposition and their relationships with disease pathogenesis had been studied. However, the relationship between ICs and each disease is not well understood and little is known of what determined ICs deposition in particular organ and why different organs are affected in different diseases. Recent technological advance enables identification of ICs in particular its antigens in tissues and body fluids, which may provide a key to discover an important trigger for immunological abnormality occurrence. Further identification of their epitopes, that are the exact origin of antigenicity, is developing and may be useful for diagnosis, elucidation of pathogenesis and treatment against IC-induced diseases. Here, we first make an overview of clearance of ICs, IC-induced pathogenesis and biological properties of ICs. Then, we introduce various methods developed to recover ICs from biological fluids or to identify antigens incorporated into ICs. Furthermore, several methods that can be used in epitope mapping for IC antigens are also documented.

Circulating immune complexes levels correlate with the progression of canine leishmaniosis in naturally infected dogs

Dogs are the main domestic reservoir of Leishmania infantum, and in cases of uncontrolled infection, a strong humoral immune response is elicited, which is inefficient against the parasites. Previous studies have suggested that an adequate antigen/antibody ratio, with a moderate prevalence of antigens with respect to the antibodies, could result in the formation of circulating immune complexes (CIC) in canine leishmaniosis (CanL). Deposition of these complexes in tissues has been associated with vasculitis, uveitis, arthritis, dermatitis and especially glomerulonephritis and renal failure. However, little is known about the relationship between the presence of CIC and disease progression. The aim of this study was to evaluate serum CIC level and its correlation with disease severity in infected dogs with different stages of disease and non-infected animals as a control. A total of 60 dogs were included in the study, classified according to the proposed LeishVet classification criteria: healthy non-infected (n = 13); healthy infected (n = 12); sick stage I (n = 9); sick stage II (n = 17); sick stage III (n = 8); and sick stage IV (n = 1). CIC were isolated from serum samples using a modified polyethylene glycol precipitation method, and their levels measured by ELISA and bicinchoninic acid protein assay. A nanoparticle tracking analysis was performed to investigate the relationship between the molecular size distribution of the CIC and disease progression. In conclusion, the results confirmed a positive association between CIC levels, their molecular size and disease progression that suggests a potential use of CIC as biomarkers of CanL.

Plasma sMer, sAxl and GAS6 levels correlate with disease activity and severity in lupus nephritis

OBJECTIVE

The purpose of this study is to determine whether TAM receptors and ligands associated with the activity and severity of lupus nephritis.

METHODS

Clinical data were statistically analysed and studied in 122 SLE patients, diagnosed from 2013 to 2016 in First Hospital Affiliated to Harbin Medical University. Levels of TAM receptors and ligands in the plasma of 122 SLE patients were measured by ELISA. Renal biopsies were performed to confirm lupus nephritis (LN) by histopathology in 68 patients. The associations of TAM receptors and ligands with clinical and serological parameters were analysed in 68 LN patients.

RESULTS

Amongst patients with SLE, those with LN had significantly higher plasma sMer, sAxl and GAS6 levels than those without renal involvement (P < 0.01 for all comparisons). Additional comparisons on the renal function-associated clinical parameters confirmed an indicative role of the sMer, sAXL and GAS6 levels in the cohort of patients with more severe nephritis. Patients with higher sMer, sAXL and GAS6 levels of LN patients tended to suffer from proliferative glomerulonephritis. The sAXL and GAS6 levels had a strong positive correlation with activity index (AI) in LN patients. Furthermore, there was a significant drop of the sMer, sAXL and GAS6 concentrations from the time of the biopsy to month t6, but no further decrease from months t6 to t12.

CONCLUSIONS

These results suggest that plasma sMer, sAxl and GAS6 can be an additional clinical marker related to the disease activity and severity in LN.

Systemic translocation of Staphylococcus drives autoantibody production in HIV disease

BACKGROUND

Increased autoreactive antibodies have been reported in HIV disease; however, the mechanism accounting for autoantibody induction in HIV remains unknown.

RESULTS

Herein, we show that seasonal influenza vaccination induces autoantibody production (e.g., IgG anti-nuclear antibody (ANA) and anti-double-stranded DNA antibody (anti-dsDNA)) in some viral-suppressed antiretroviral therapy (ART)-treated HIV+ subjects, but not in healthy controls. These autoantibodies were not derived from antigen-specific B cells but from activated "bystander" B cells analyzed by single-cell assay and by study of purified polyclonal ANAs from plasma. To explore the mechanism of autoantibody generation in HIV+ subjects, plasma level of microbial products, gene expression profile of B cells, and B cell receptor (BCR) repertoires were analyzed. We found that autoantibody production was associated with increased plasma level of microbial translocation; the patients with high autoantibodies had skewed B cell repertoires and upregulation of genes related to innate immune activation in response to microbial translocation. By analyzing circulating microbial 16S rDNA in plasma, the relative abundance of Staphylococcus was found to be associated with autoantibody production in HIV+ subjects. Finally, we found that injection of heat-killed Staphylococcus aureus promoted germinal center B cell responses and autoantibody production in mice, consistent with the notion that autoantibody production in HIV+ patients is triggered by microbial products.

CONCLUSIONS

Our results showed that translocation of Staphylococcus can promote B cell activation through enhancing germinal center response and induces autoantibody production. It uncovers a potential mechanism linking microbial translocation and autoimmunity in HIV+ disease and provides a strong rationale for targeting Staphylococcus to prevent autoantibody production.

Similarity of autoimmune diseases based on the profile of immune complex antigens

Since immune complexes (IC) are a direct product of immune response through the binding between antigen and antibody, the profile of antigen-associated ICs may depend on each autoimmune disease. In this report, we examined the similarity of four neurological autoimmune diseases, Alzheimer's disease and healthy donors, and seven connective tissue diseases based on the profiling of IC-associated antigens which were previously or recently identified by immune complexome analysis of cerebrospinal fluid (CSF) or serum samples. The similarity between each pair of two diseases was assessed by correlation coefficients as distance matrix with the use of detection frequency (i.e., the percentage of patients who were positive for a certain antigen in each disease) of each IC-associated antigen in a certain disease. Among 15 pairs of five diseases and healthy control examined by the analysis of CSF samples, only 1 pair of neuropsychiatric systemic lupus erythematosus and multiple sclerosis corresponds to the higher correlation value (r = 0.73) than 0.7. On the other hand, among seven connective tissue diseases examined by the analysis of serum samples, 12 of 21 pairs show high correlation value (r > 0.70). Our finding suggested that the profile of IC-associated antigens identified by immune complexome analysis of CSF samples can be useful for evaluating the similarity of neurological autoimmune diseases; however, not by that of serum samples.

Glomerulonephritis in Animal Models and Human Medicine: Discovery, Pathogenesis, and Diagnostics

Glomerulonephritis (GN) is inflammation of glomeruli. The four major categories that cause human GN are mediated by immunoglobulin or complement or both, and they include (1) immune complex-mediated GN, (2) anti-glomerular basement membrane-mediated GN, (3) antineutrophil cytoplasmic autoantibody-mediated GN, and (4) complement factor 3 glomerulopathy mediated by complement dysregulation. Initiating processes include infection, autoimmunity, exogenous antigens, and neoplasia. Often there are predisposing and modulating genetic, epigenetic, and/or environmental factors. Animal models facilitated the recognition and elucidation of the pathogeneses of all four categories of GN, and they continue to be used in preclinical studies to identify and validate therapies for all four types of GN. Advanced diagnostic modalities (e.g., transmission electron microscopy and immunofluorescence) are helpful and sometimes required for the correct categorization of GN in humans and animals. This review provides historical background on the discovery of the different GN pathogeneses, describes some of the animal models used to discover and understand each GN pathogenic category, reviews the diagnostic classification of each category of GN, and compares human GN to spontaneous forms of nonhuman GN.

Drug-induced Glomerulonephritis: The Spectre of Biotherapeutic and Antisense Oligonucleotide Immune Activation in the Kidney

Prevalence of immune-mediated glomerulonephritis has increased in preclinical toxicity studies, with more frequent use of biotherapeutic agents (especially antigenic humanized molecules) and antisense oligonucleotide (ASO) therapies. Immune complex disease affects a small number of study monkeys, often correlates with antidrug antibody (ADA) titers, and occurs at a dose that favors immune complex formation or impedes clearance. While preclinical glomerulonephritis often fails to correlate with evidence of glomerular or vascular injury in human clinical trials and is not considered predictive, additional animal investigative immunohistochemical work may be performed to substantiate evidence for immune complex pathogenesis. While ADA is most commonly encountered as a predisposing factor with biotherapeutic agents, complement activation may occur without circulating complexes, and other mechanisms of non-ADA immune-mediated glomerulonephritis have been observed including nonendogenous immune aggregates and immunoregulatory pharmacology. Although glomerulonephritis associated with oligonucleotide therapies has been noted occasionally in preclinical studies and more rarely with human patients, pathophysiologic mechanisms involved appear to be different between species and preclinical cases are not considered predictive for humans. ADA is not involved in oligonucleotide-associated cases, and complement fixation plays a more important role in monkeys. Recent screening of ASOs for proinflammatory activity appears to have decreased glomerulonephritis incidence preclinically.

Predominant but silent C1q deposits in mesangium on transplanted kidneys - long-term observational study

Background

C1q nephropathy (C1qN) was first described as glomerular disease characterized by predominant meangial C1q deposits in patients with proteinuria and no evidence of systemic lupus erythematosus. Several studies, however, revealed the clinical heterogeneity of C1qN, showing some cases with normal urinalysis. To confirm the existence of cases with predominant mesangial C1q deposits and negative or mild proteinuria and/or hematuria, we investigated renal graft biopsy specimens showing negative to mild proteinuria (less than or equal to 1+ by dip stick test) and/or hematuria.

Methods

Eligible participants were kidney transplant cases who corresponded to the criteria for C1qN and were followed more than 10 years. Their medical records were reviewed to determine the age at detection of predominant mesangial C1q deposits, gender, original renal disease and reason for renal graft biopsy, blood pressure, degree of proteinuria and hematuria, and serum creatinine levels.

Results

From 414 cases in adults and children, five pediatric patients (the male to female ratio, 1:1.5) were eligible. At the time when predominant mesangial C1q deposits were detected, 2 cases presented with mild proteinuria without hematuria, but the other 3 cases showed normal urinalysis. Light microscopy revealed minor glomerular abnormality in all the cases. Immunofluorescent study showed predominant mesangial C1q deposits with IgG, IgM and C3 in all cases. All selected specimens presented electron dense-depos in the mesangium. Ten years later from the detection, 2 cases continued to be normal urinalysis and 3 cases had mild proteinuria without hematuria. During this follow-up period, no cases presented with persistent proteinuria and/or hematuria greater than or equal to 2+ by dip stick test. And no cases developed systemic lupus erythematosus. Follow-up renal graft biopsies were performed once in 2 cases 8 years later from the detection. They showed minor glomerular abnormalities. C1q deposit disappeared in one case. In another case, immunofluorescent study was not examined.

Conclusions

This long-term observational study on transplanted kidneys confirms the existence of cases with predominant but silent C1q deposits in the mesangium who have negative or mild proteinuria.

Electronic supplementary material

The online version of this article (10.1186/s12882-018-0874-9) contains supplementary material, which is available to authorized users.

The role of the immune system in kidney disease

The immune system and the kidneys are closely linked. In health the kidneys contribute to immune homeostasis, while components of the immune system mediate many acute forms of renal disease and play a central role in progression of chronic kidney disease. A dysregulated immune system can have either direct or indirect renal effects. Direct immune-mediated kidney diseases are usually a consequence of autoantibodies directed against a constituent renal antigen, such as collagen IV in anti-glomerular basement membrane disease. Indirect immune-mediated renal disease often follows systemic autoimmunity with immune complex formation, but can also be due to uncontrolled activation of the complement pathways. Although the range of mechanisms of immune dysregulation leading to renal disease is broad, the pathways leading to injury are similar. Loss of immune homeostasis in renal disease results in perpetual immune cell recruitment and worsening damage to the kidney. Uncoordinated attempts at tissue repair, after immune-mediated disease or non-immune mediated injury, result in fibrosis of structures important for renal function, leading eventually to kidney failure. As renal disease often manifests clinically only when substantial damage has already occurred, new diagnostic methods and indeed treatments must be identified to inhibit further progression and promote appropriate tissue repair. Studying cases in which immune homeostasis is re-established may reveal new treatment possibilities.

ABIN1 Determines Severity of Glomerulonephritis via Activation of Intrinsic Glomerular Inflammation

Transcription factor NF-κB regulates expression of numerous genes that control inflammation and is activated in glomerular cells in glomerulonephritis (GN). We previously identified genetic variants for a NF-κB regulatory, ubiquitin-binding protein ABIN1 as risk factors for GN in systemic autoimmunity. The goal was to define glomerular inflammatory events controlled by ABIN1 function in GN. Nephrotoxic serum nephritis was induced in wild-type (WT) and ubiquitin-binding deficient ABIN1[D485N] mice, and renal pathophysiology and glomerular inflammatory phenotypes were assessed. Proteinuria was also measured in ABIN1[D485N] mice transplanted with WT mouse bone marrow. Inflammatory activation of ABIN1[D472N] (D485N homolog) cultured human-derived podocytes, and interaction with primary human neutrophils were also assessed. Disruption of ABIN1 function exacerbated proteinuria, podocyte injury, glomerular NF-κB activity, glomerular expression of inflammatory mediators, and glomerular recruitment and retention of neutrophils in antibody-mediated nephritis. Transplantation of WT bone marrow did not prevent the increased proteinuria in ABIN1[D845N] mice. Tumor necrosis factor-stimulated enhanced expression and secretion of NF-κB-targeted proinflammatory mediators in ABIN1[D472N] cultured podocytes compared with WT cells. Supernatants from ABIN1[D472N] podocytes accelerated chemotaxis of human neutrophils, and ABIN1[D472N] podocytes displayed a greater susceptibility to injurious morphologic findings induced by neutrophil granule contents. These studies define a novel role for ABIN1 dysfunction and NF-κB in mediating GN through proinflammatory activation of podocytes.

The pathogenesis of diclofenac induced immunoallergic hepatitis in a canine model of liver injury

Hypersensitivity to non-steroidal anti-inflammatory drugs is a common adverse drug reaction and may result in serious inflammatory reactions of the liver. To investigate mechanism of immunoallergic hepatitis beagle dogs were given 1 or 3 mg/kg/day (HD) oral diclofenac for 28 days. HD diclofenac treatment caused liver function test abnormalities, reduced haematocrit and haemoglobin but induced reticulocyte, WBC, platelet, neutrophil and eosinophil counts. Histopathology evidenced hepatic steatosis and glycogen depletion, apoptosis, acute lobular hepatitis, granulomas and mastocytosis. Whole genome scans revealed 663 significantly regulated genes of which 82, 47 and 25 code for stress, immune response and inflammation. Immunopathology confirmed strong induction of IgM, the complement factors C3&B, SAA, SERPING1 and others of the classical and alternate pathway. Alike, marked expression of CD205 and CD74 in Kupffer cells and lymphocytes facilitate antigen presentation and B-cell differentiation. The highly induced HIF1A and KLF6 protein expression in mast cells and macrophages sustain inflammation. Furthermore, immunogenomics discovered 24, 17, 6 and 11 significantly regulated marker genes to hallmark M1/M2 polarized macrophages, lymphocytic and granulocytic infiltrates; note, the latter was confirmed by CAE staining. Other highly regulated genes included alpha-2-macroglobulin, CRP, hepcidin, IL1R1, S100A8 and CCL20. Diclofenac treatment caused unprecedented induction of myeloperoxidase in macrophages and oxidative stress as shown by SOD1/SOD2 immunohistochemistry. Lastly, bioinformatics defined molecular circuits of inflammation and consisted of 161 regulated genes.

Altogether, the mechanism of diclofenac induced liver hypersensitivity reactions involved oxidative stress, macrophage polarization, mastocytosis, complement activation and an erroneous programming of the innate and adaptive immune system.

Increased Mer and Axl receptor tyrosine kinase expression on glomeruli in lupus nephritis

Mer and Axl receptor tyrosine kinases (MerTK and AxlTK) play important roles in the clearance of apoptotic cells and the inhibition of inflammatory responses. Previous studies demonstrated that they might participate in glomerular injury in mice model. This study aimed to elucidate the expression of MerTK and AxlTK on glomeruli and analyze their clinical significance in lupus nephritis (LN) patients. Twenty-nine LN and 10 primary nephrotic syndrome (NS) patients were recruited. The expression of MerTK and AxlTK on glomeruli was measured by immunohistochemistry. Correlations between the levels of MerTK and AxlTK and clinical data were investigated. Statistical differences in each group were calculated by one-way analysis of variance, t test, or Mann-Whitney U test. Correlations were evaluated with Pearson's or Spearman's correlation tests. Both MerTK and AxlTK were expressed mainly on mesangial cells. LN patients demonstrated more expression of MerTK and AxlTK than primary NS patients (1.19 ± 1.01 × 10^-2 vs 0.21 ± 0.29 × 10^-2, 7.25 ± 2.69 × 10^-2 vs 3.10 ± 1.22 × 10^-2, p < 0.01). In LN patients, MerTK expression correlated with AxlTK (r = 0.529, p < 0.01). LN patients with class IV expressed more MerTK and AxlTK (1.50 ± 1.03 × 10^-2 and 7.56 ± 2.93 × 10^-2). The expression of MerTK and AxlTK varied according to the deposition of immunoglobulin and complements on glomeruli. Both MerTK and AxlTK expressions were increased on glomeruli and varied according to pathological classifications. Thus, we assumed that both two subsets might participate in the pathogenesis of LN.

Prevalence of Glomerulopathies in Canine Mammary Carcinoma

The incidence and prevalence of paraneoplastic glomerulopathy, especially associated with carcinoma, are a matter of debate and the causal link between cancer and glomerular diseases remains unclear. The aim of this study was to evaluate renal biopsies of selected bitches with spontaneous mammary gland carcinoma. We hypothesized that dogs with mammary carcinomas would show histologic evidence of glomerular pathology. A prospective study was performed in dogs with naturally occurring mammary carcinoma that were undergoing tumor resection and ovariohysterectomy. We evaluated renal biopsies of 32 bitches with spontaneous mammary gland carcinoma and 11 control dogs without mammary gland neoplasia. Samples were obtained from the left kidney and the biopsy material was divided for light microscopy (LM), immunofluorescence (IF) and transmission electron microscopy (TEM). Light microscopy abnormalities were identified in 78.1% of dogs with mammary carcinoma (n = 25) and in none of the dogs in the control group. Focal glomerular mesangial matrix expansion was the most common alteration (n = 15, 60.0%), but mesangial cell proliferation (n = 9, 36.0%) and focal segmental glomerulosclerosis (n = 9, 36.0%), synechiae (n = 7, 28.0%), and globally sclerotic glomeruli (n = 6, 24.0%) were also frequent in dogs with malignancy. Immunofluorescence microscopy revealed strong IgM staining was demonstrated in 64.3% (n = 18) of carcinoma dogs. Transmission electron microscopy from dogs with carcinoma revealed slight changes, the most frequent of which was faint sub-endothelial and mesangial deposits of electron-dense material (78%). Mesangial cell interpositioning and segmental effacement of podocyte foot processes were identified in some specimens (45%). Changes in the glomerulus and proteinuria are common in dogs with naturally occurring mammary carcinoma and this condition appears to provide an excellent large animal model for cancer-associated glomerulopathy in humans.

Significance of Lipid-Derived Reactive Aldehyde-Specific Immune Complexes in Systemic Lupus Erythematosus

Even though systemic lupus erythematosus (SLE) is associated with high morbidity and mortality rates among young and middle-aged women, the molecular mechanisms of disease pathogenesis are not fully understood. Previous studies from our laboratory suggested an association between oxidative stress and SLE disease activity (SLEDAI). To further assess the role of reactive oxygen species (ROS) in SLE, we examined the contribution of lipid-derived reactive aldehydes (LDRAs)-specific immune complexes in SLE. Sera from 60 SLE patients with varying SLEDAI and 32 age- and gender- matched healthy controls were analyzed for oxidative stress and related markers. Patients were divided into two groups based on their SLEDAI scores (<6 and ≥ 6). Both SLEDAI groups showed higher serum 4-hydroxynonenal (HNE)-/malondialdehyde (MDA)-protein adducts and their specific immune complexes (HNE-/MDA-specific ICs) together with IL-17 than the controls, but the levels were significantly greater in the high SLEDAI (≥ 6) group. Moreover, the serum levels of anti-oxidant enzymes Cu/Zn superoxide dismutase (SOD) and catalase (CAT) were significantly reduced in both patient groups compared to controls. Remarkably, for the first time, our data show that increased HNE-/MDA-specific ICs are positively associated with SLEDAI and elevated circulating immune complexes (CICs), suggesting a possible causal relationship among oxidative stress, LDRA-specific ICs and the development of SLE. Our findings, apart from providing firm support to an association between oxidative stress and SLE, also suggest that these oxidative stress markers, especially the HNE-/MDA-specific ICs, may be useful in evaluating the prognosis of SLE as well as in elucidating the mechanisms of disease pathogenesis.

Treatment with rituximab in idiopathic membranous nephropathy

BACKGROUND

Rituximab represents a valid therapeutic option to induce remission in patients with primary glomerulonephritis. Despite several studies proving its efficacy in improving outcomes in patients with membranous nephropathy (MN), its role in therapeutic protocols is not yet defined.

METHODS

We studied 38 patients with idiopathic MN treated with rituximab (in 13 patients as first-line therapy, in the remaining 25 after conventional immunosuppressive therapy). The patients were analyzed for a 15-month median (interquartile range 7.7-30.2) follow-up, with serial monitoring of 24-h proteinuria, renal function and circulating CD19⁺ B cells.

RESULTS

The percentages of patients who achieved complete remission, partial remission and the composite endpoint (complete or partial remission) were 39.5% (15 patients), 36.8% (14 patients) and 76.3% (29 patients), respectively. The 24-h proteinuria was reduced significantly during the entire period of follow-up (from a baseline value of 6.1 to 0.9 g/day in the last visit; P < 0.01), while albuminemia increased constantly (from a baseline value of 2.6 to 3.5 g/dL in the last observation; P < 0.01). Renal function did not significantly change during the observation period. Circulating CD19⁺ B cells were reduced significantly from the baseline value to the 24-month value (P < 0.01); data about anti-phospholipase A₂ receptor antibodies were available in 14 patients, 10 of which experienced a decreasing trend after treatment. No significant adverse events were described during and after infusions.

CONCLUSIONS

The present study confirmed that treatment with rituximab was remarkably safe and allowed for a large percentage of complete or partial remissions in patients with MN.

Insights from Mendelian Interferonopathies: Comparison of CANDLE, SAVI with AGS, Monogenic Lupus

Autoinflammatory disorders are sterile inflammatory conditions characterized by episodes of early-onset fever and disease-specific patterns of organ inflammation. Recently, the discoveries of monogenic disorders with strong type I interferon (IFN) signatures caused by mutations in proteasome degradation and cytoplasmic RNA and DNA sensing pathways suggest a pathogenic role of IFNs in causing autoinflammatory phenotypes. The IFN response gene signature (IGS) has been associated with systemic lupus erythematosus (SLE) and other autoimmune diseases. In this review, we compare the clinical presentations and pathogenesis of two IFN-mediated autoinflammatory diseases, CANDLE and SAVI, with Aicardi Goutières syndrome (AGS) and monogenic forms of SLE (monoSLE) caused by loss-of-function mutations in complement 1 (C1q) or the DNA nucleases, DNASE1 and DNASE1L3. We outline differences in intracellular signaling pathways that fuel a pathologic type I IFN amplification cycle. While IFN amplification is caused by predominantly innate immune cell dysfunction in SAVI, CANDLE, and AGS, autoantibodies to modified RNA and DNA antigens interact with tissues and immune cells including neutrophils and contribute to IFN upregulation in some SLE patients including monoSLE, thus justifying a grouping of "autoinflammatory" and "autoimmune" interferonopathies. Understanding of the differences in the cellular sources and signaling pathways will guide new drug development and the use of emerging targeted therapies.

Unraveling the immunopathogenesis of glomerular disease

Immune-mediated damage to glomerular structures is largely responsible for the pathology associated with the majority of glomerular diseases. Therefore, a detailed understanding of the basic immune mechanisms responsible for glomerular damage is needed to inform the design of novel intervention strategies. Glomerular injury of immune origin is complex and involves both inflammatory and non-inflammatory processes driven by elements of the innate and adaptive immune system. This review summarizes the basic immune mechanisms that cause glomerular injury leading to the nephritic and nephrotic syndromes. A major focus of the review is to highlight the mechanisms by which antibodies cause glomerular injury through their interactions with glomerular cells, complement proteins, phagocytes bearing complement and Fcγ receptors, and dendritic cells expressing the neonatal receptor for IgG, FcRn.

Advances in the evaluation of canine renal disease

Many recent advances in the evaluation of dogs with kidney disease have improved our diagnostic algorithms and have impacted our therapeutic strategies. Non-invasive techniques, such as urinary and serologic biomarker evaluation, can help a clinician diagnose and treat a patient that cannot undergo a renal biopsy for clinical or financial reasons. Some biomarkers might help localize the affected structure (glomerulus vs. tubule) and indicate the type or severity of injury present. Although more research is needed, studies indicate that some biomarkers (e.g. urine protein to creatinine ratio and urinary immunoglobulins) can be useful in predicting adverse outcomes. Importantly, the sensitivity and specificity of biomarkers for renal injury should be established and clinicians need to understand the limitations of these assays. If a renal biopsy is performed, then it should be evaluated by a specialty diagnostic service with expertise in nephropathology. A panel of special stains, immunofluorescence for the detection of immunoglobulins and complement factors, and transmission electron microscopy can be routinely employed in cases of glomerular disease. These advanced diagnostics can be used to detect immune deposits in order to definitively diagnose immune complex mediated glomerular disease. Integrating the results of biomarker assays and comprehensive renal biopsy evaluation, the clinician can make informed therapeutic decisions, such as whether or not to immunosuppress a patient.

Alternative Pathway Dysregulation and the Conundrum of Complement Activation by IgG4 Immune Complexes in Membranous Nephropathy

Membranous nephropathy (MN), a major cause of nephrotic syndrome, is a non-inflammatory immune kidney disease mediated by IgG antibodies that form glomerular subepithelial immune complexes. In primary MN, autoantibodies target proteins expressed on the podocyte surface, often phospholipase A2 receptor (PLA2R1). Pathology is driven by complement activation, leading to podocyte injury and proteinuria. This article overviews the mechanisms of complement activation and regulation in MN, addressing the paradox that anti-PLA2R1 and other antibodies causing primary MN are predominantly (but not exclusively) IgG4, an IgG subclass that does not fix complement. Besides immune complexes, alterations of the glomerular basement membrane (GBM) in MN may lead to impaired regulation of the alternative pathway (AP). The AP amplifies complement activation on surfaces insufficiently protected by complement regulatory proteins. Whereas podocytes are protected by cell-bound regulators, the GBM must recruit plasma factor H, which inhibits the AP on host surfaces carrying certain polyanions, such as heparan sulfate (HS) chains. Because HS chains present in the normal GBM are lost in MN, we posit that the local complement regulation by factor H may be impaired as a result. Thus, the loss of GBM HS in MN creates a micro-environment that promotes local amplification of complement activation, which in turn may be initiated via the classical or lectin pathways by subsets of IgG in immune complexes. A detailed understanding of the mechanisms of complement activation and dysregulation in MN is important for designing more effective therapies.

New Insights into Molecular Mechanisms of Immune Complex-Induced Injury in Lung

While the phlogistic activities of IgM or IgG immune complexes (ICs) have been well established as complement-activating agents and seem likely to play important roles in humans with vasculitis, certain types of glomerulonephritis as well as in a variety of autoimmune diseases, the predominant clinical strategies have involved the use of immunosuppressive or anti-inflammatory drugs. Over the past decade, new insights into molecular events developing during IC models in rodents have identified new phlogistic products that may be candidates for therapeutic blockade. Extracellular histones, located in the web-like structures of neutrophil extracellular traps, are released from complement-activated polymorphonuclear neutrophils (PMNs) downstream of IC deposition. Extracellular histones appear to be a new class of highly tissue-damaging products derived from complement-activated PMNs. Histones have also been discovered in cell-free broncho-alveolar lavage fluids from humans with acute respiratory distress syndrome (ARDS). Recent studies emphasize that in the setting of ARDS-like reactions in rodents, extracellular histones are released and are exceedingly proinflammatory, tissue damaging, and prothrombotic. Such studies suggest that in humans with ARDS, extracellular histones may represent therapeutic targets for blockade.

Evaluation of the hemocompatibility and rapid hemostasis of (RADA)4 peptide-based hydrogels

(RADA)4 peptides are promising biomaterials due to their high degree of hydration (<99.5% (w/v)), programmability at the molecular level, and their subsequent potential to respond to external stimuli. Interestingly, these peptides have also demonstrated the ability to cause rapid (∼15s) hemostasis when applied directly to wounds. General hemocompatibility of (RADA)4 nanofibers was investigated systematically using clot formation kinetics, C3a generation, and platelet activation (morphology and CD62P) studies. (RADA)4 nanofibers caused a rapid clot formation, but yielded a low platelet activation and low C3a activation. The study suggests that the rapid hemostasis observed when these materials are employed results principally from humoral coagulation, despite these materials having a net neutral charge and high hydration at physiological conditions. The observed rapid hemostasis may be induced due to the available nanofiber surface area within the hydrogel construct. In conclusion, our experiments strongly support further development of (RADA)4 peptide based biomaterials.

STATEMENT OF SIGNIFICANCE

Biomedicine based applications of (RADA)4 peptides are being extensively studied for the purpose of improving drug carriers, and 3D peptide nanofiber scaffolds. However, this peptide's biocompatibility has not been investigated till now. One particular study has reported a revolutionary and very desirable ability of (RADA)4 peptide to achieve complete and rapid hemostasis, nevertheless, the literature remains inconclusive on the underlying molecular mechanism. In this manuscript we bridge these two main knowledge gaps by providing the much needed systematic biocompatibility analysis (morphology analysis, platelet and C3a activation) of the (RADA)4 based hydrogels, and also investigate the underlying hemostatic mechanism of this peptide-induced hemostasis. Our work not only provides the much-needed biocompatibility of the peptide for applicative research, but also explores the molecular mechanism of hemostasis, which will help us design novel biomaterials to achieve hemostasis.

Immunology of membranous nephropathy: from animal models to humans

Membranous nephropathy (MN), the leading cause of nephrotic syndrome in adults, is characterized by the deposition of subepithelial immune deposits that consist mainly of immunoglobulin (Ig)G and complement. Most of the cases are primary or idiopathic (iMN), while only approximately 25% of the cases are secondary to some known disease such as systemic lupus erythematosus, hepatitis B, drugs and malignancies. Most of our knowledge on the pathogenesis of iMN has relied upon old experimental models (i.e. Heymann nephritis) that have shown that immune deposits are formed in situ by the reaction of autoantibodies against the respective podocyte antigen. Recent findings indicate that podocyte proteins also act as an autoantigen in human iMN. The M-type phospholipase A2 receptor (PLA2R) has been identified as the main target antigen, as it can be found in approximately 70% of iMN patients but only rarely in other glomerulonephritides. Podocytes damage in the experimental model of Heymann nephritis is complement-mediated. In humans, the presence of complement within the subepithelial deposits is well established, but IgG4, which does not activate complement by classical or alternative pathways, represents the predominant subclass of IgG anti-PLA2R. Some evidence suggests that IgG4 anti-PLA2R autoantibodies can bind mannan-binding lectin (MBL) and activate the lectin complement pathway. A genetic background for iMN has been demonstrated by genome-wide association studies that have shown highly significant associations of the PLA2R1 and the human leucocyte antigen (HLA)-DQA1 loci with iMN. In addition to their diagnostic value, anti-PLA2R antibodies may be useful to monitor disease activity and predict response to treatment.