Molecular architecture of the Goodpasture autoantigen in anti-GBM nephritis

Anti-GBM antibody in a patient with diabetic nephropathy; all that glitters is not gold

We present the case of a 58-year-old male diabetic patient admitted to our department for a slight decrease in kidney function, with nephrotic range proteinuria, hematuria (16,000/ml) and positive anti-glomerular basement membrane antibodies. Kidney biopsy revealed diabetic nephropathy with no evidence of crescent formation or linear immunoglobulin deposits along the basement membrane. We discuss the various clinical settings involving positive anti-glomerular basement membrane in the absence of crescentic glomerulonephritis.

Systemic vasculitis involving the kidney: the nephropathologist's point of view

Kidneys are often targets of systemic vasculitis (SVs), being affected in many different forms and representing a possible sentinel of an underlying multi-organ condition. Renal biopsy still remains the gold standard for the identification, characterization and classification of these diseases, solving complex differential diagnosis thanks to the combined application of light microscopy (LM), immunofluorescence (IF) and electron microscopy (EM). Due to the progressively increasing complexity of renal vasculitis classification systems (e.g. pauci-immune vs immune complex related forms), a clinico-pathological approach is mandatory and adequate technical and interpretative expertise in nephropathology is required to ensure the best standard of care for our patients. In this complex background, the present review aims at summarising the current knowledge and challenges in the world of renal vasculitis, unveiling the potential role of the introduction of digital pathology in this setting, from the creation of hub-spoke networks to the future application of artificial intelligence (AI) tools to aid in the diagnostic and scoring/classification process.

Autoimmune diseases: targets, biology, and drug discovery

Autoimmune diseases (AIDs) arise from a breakdown in immunological self-tolerance, wherein the adaptive immune system mistakenly attacks healthy cells, tissues and organs. AIDs impose excessive treatment costs and currently rely on non-specific and universal immunosuppression, which only offer symptomatic relief without addressing the underlying causes. AIDs are driven by autoantigens, targeting the autoantigens holds great promise in transforming the treatment of these diseases. To achieve this goal, a comprehensive understanding of the pathogenic mechanisms underlying different AIDs and the identification of specific autoantigens are critical. In this review, we categorize AIDs based on their underlying causes and compile information on autoantigens implicated in each disease, providing a roadmap for the development of novel immunotherapy regimens. We will focus on type 1 diabetes (T1D), which is an autoimmune disease characterized by irreversible destruction of insulin-producing β cells in the Langerhans islets of the pancreas. We will discuss insulin as possible autoantigen of T1D and its role in T1D pathogenesis. Finally, we will review current treatments of TID and propose a potentially effective immunotherapy targeting autoantigens.

Using imlifidase to elucidate the characteristics and importance of anti-GBM antibodies produced after start of treatment

BACKGROUND

Autoantibodies are common in glomerulonephritis, but the clinical benefit of rapid elimination has not been determined, even in anti-glomerular basement membrane (GBM) disease. Even less is known about the importance of autoantibody characteristics, including epitope specificity and immunoglobulin G (IgG) subclass distribution. We aimed to address this by characterizing the autoantibody profile in anti-GBM patients: we utilized samples from the GOOD-IDES-01 (treating GOODpasture's disease with Imunoglobulin G Degrading Enzyme of Streptococcus pyogenous) (ClinicalTrials.gov identifier: NCT03157037) trial , where imlifidase, which cleaves all IgG in vivo within hours, was given to 15 anti-GBM patients.

METHODS

In the GOOD-IDES-01 trial, plasmapheresis was (re)started if anti-GBM antibodies rebounded. Serum samples were collected prospectively for 6 months and analyzed for anti-GBM epitope specificity using recombinant constructs of the EA and EB epitopes, IgG subclass using monoclonal antibodies, and anti-neutrophil cytoplasmic antibodies (ANCA). The results were correlated with clinical data.

RESULTS

Patients with a rebound (n = 10) tended to have lower eGFR at 6 months (11 vs 34 mL/min/1.73 m2, P = .055), and patients with dialysis at 6 months had a higher EB/EA ratio at rebound (0.8 vs 0.5, P = .047). Moreover, two patients demonstrated increasing epitope restriction and several patients displayed a shift in subclass distribution at rebound. Six patients were double positive for ANCA. ANCA rebound was seen in 50% of patients; only one patient remained ANCA positive at 6 months.

CONCLUSIONS

In this study, rebound of anti-GBM antibodies, especially if directed against the EB epitope, was associated with a worse outcome. This supports the notion that all means should be used to eliminate anti-GBM antibodies. In this study ANCA was removed early and long-term by imlifidase and cyclophosphamide.

Laminin-521: a novel target for pathogenic autoantibodies in anti-glomerular basement membrane disease

Anti-glomerular basement membrane (anti-GBM) disease is typically characterized by autoimmunity against the α3 chain of type IV collagen. Rarely, circulating autoantibodies are not detected. These atypical cases follow a more indolent clinical course, and underlying mechanisms, including alternative target antigens, require investigation. In this issue of Kidney International, Kuang et al. describe a case of anti-GBM disease with autoantibodies against the GBM component laminin-521 and demonstrate that laminin-521 is pathogenic in a rat model of anti-GBM glomerulonephritis.

The role of complement in kidney disease

The complement cascade comprises soluble and cell surface proteins and is an important arm of the innate immune system. Once activated, the complement system rapidly generates large quantities of protein fragments that are potent mediators of inflammatory, vasoactive and metabolic responses. Although complement is crucial to host defence and homeostasis, its inappropriate or uncontrolled activation can also drive tissue injury. For example, the complement system has been known for more than 50 years to be activated by glomerular immune complexes and to contribute to autoimmune kidney disease. Notably, the latest research shows that complement is also activated in kidney diseases that are not traditionally thought of as immune-mediated, including haemolytic-uraemic syndrome, diabetic kidney disease and focal segmental glomerulosclerosis. Several complement-targeted drugs have been approved for the treatment of kidney disease, and additional anti-complement agents are being investigated in clinical trials. These drugs are categorically different from other immunosuppressive agents and target pathological processes that are not effectively inhibited by other classes of immunosuppressants. The development of these new drugs might therefore have considerable benefits in the treatment of kidney disease.

The five types of glomerulonephritis classified by pathogenesis, activity and chronicity (GN-AC)

Glomerulonephritis (GN) is a diverse group of immune-mediated disorders. Currently, GN is classified largely by histological patterns that are difficult to understand and teach, and most importantly, do not indicate treatment choices. Indeed, altered systemic immunity is the primary pathogenic process and the key therapeutic target in GN. Here, we apply a conceptual framework of immune-mediated disorders to GN guided by immunopathogenesis and hence immunophenotyping: (i) infection-related GN require pathogen identification and control; (ii) autoimmunity-related GN, defined by presence of autoantibodies and (iii) alloimmunity-related GN in transplant recipients both require the suppression of adaptive immunity in lymphoid organs and bone marrow; (iv) autoinflammation-related GN, e.g. inborn errors of immunity diagnosed by genetic testing, requires suppression of single cytokine or complement pathways; and (v) Monoclonal gammopathy-related GN requires B or plasma cell clone-directed therapy. A new GN classification should include disease category, immunological activity to tailor the use of the increasing number of immunomodulatory drugs, and chronicity to trigger standard chronic kidney disease care including the evolving spectrum of cardio-renoprotective drugs. Certain biomarkers allow diagnosis and the assessment of immunological activity and disease chronicity without kidney biopsy. The use of these five GN categories and a therapy-focused GN classification is likely to overcome some of the existing hurdles in GN research, management and teaching by reflecting disease pathogenesis and guiding the therapeutic approach.

Three Diseases Mediated by Different Immunopathologic Mechanisms-ANCA-Associated Vasculitis, Anti-Glomerular Basement Membrane Disease, and Immune Complex-Mediated Glomerulonephritis-A Common Clinical and Histopathologic Picture: Rapidly Progressive Crescentic Glomerulonephritis

Immune mechanisms play an important role in the pathogenesis of glomerulonephritis (GN), with autoimmunity being the main underlying pathogenetic process of both primary and secondary GN. We present three autoimmune diseases mediated by different autoimmune mechanisms: glomerulonephritis in vasculitis mediated by anti-neutrophil cytoplasmic antibodies (ANCAs), glomerulonephritis mediated by anti-glomerular basement membrane antibodies (anti-GBM antibodies), and immune complex-mediated glomerulonephritis. Some of these diseases represent a common clinical and histopathologic scenario, namely rapidly progressive crescentic glomerulonephritis. This is a severe illness requiring complex therapy, with the main role being played by therapy aimed at targeting immune mechanisms. In the absence of immune therapy, the crescents, the characteristic histopathologic lesions of this common presentation, progress toward fibrosis, which is accompanied by end-stage renal disease (ESRD). The fact that three diseases mediated by different immunopathologic mechanisms have a common clinical and histopathologic picture reveals the complexity of the relationship between immunopathologic mechanisms and their clinical expression. Whereas most glomerular diseases progress by a slow process of sclerosis and fibrosis, the glomerular diseases accompanied by glomerular crescent formation can progress, if untreated, in a couple of months into whole-nephron glomerulosclerosis and fibrosis. The outcome of different immune processes in a common clinical and histopathologic phenotype reveals the complexity of the relationship of the kidney with the immune system. The aim of this review is to present different immune processes that lead to a common clinical and histopathologic phenotype, such as rapidly progressive crescentic glomerulonephritis.

Antiglomerular basement membrane antibody type rapidly progressive glomerulonephritis with seizures: Two cases and literature review

BACKGROUND

Rapidly progressive glomerulonephritis (RPGN) is clinically manifestations as a rapidly progressive renal failure and pathologically as crescentic and necrotizing lesions with infiltration of inflammatory cells in the glomeruli. Uremic encephalopathy (UE) usually develops in patients who are suffering from acute or chronic renal failure.

OBJECTIVE

The purpose of this article is to provide reference for clinical diagnosis and treatment of renal disease complicated with seizures. Patients Two cases of anti-glomerular basement membrane type rapidly progressive glomerulonephritis complicated with seizures were reported.

MATERIALS & METHODS

In case 1, a 40-year-old woman was hospitalized for the treatment of nausea, anorexia, and fever. On admission, she presented with elevated serum inflammatory indicators, moderate anemia, and advanced acute kidney injury requiring hemodialysis. Her anti-glomerular basement membrane (GBM) antibody in serum and renal tissues was found to be extremely high. She was finally diagnosed with anti-GBM disease. She was treated with a combination of corticosteroid pulse therapy, oral cyclophosphamide and prednisolone, and plasma exchange, while continued to require maintenance hemodialysis for end-stage kidney disease. During treatment, she suddenly suffered blindness, seizure, and consciousness disturbance. She was diagnosed as posterior reversible leukoencephalopathy syndrome by magnetic resonance imaging (MRI). The posterior reversible leukoencephalopathy syndrome subsided quickly after control of her hypertension and reinforcement of immunosuppressive treatment. In case 2, the patient also developed epileptic symptoms on the basis of GBM disease, and was given treatment similar to that of Case 1, so that the epileptic symptoms were controlled.

RESULT

Reversible posterior leukoencephalopathy syndrome, especially when accompanied by cerebral hemorrhage, may lead to irreversible and lethal neurological abnormalities, and nephrologists should, therefore, be aware of the potential risk of reversible posterior leukoencephalopathy syndrome in patients with anti-GBM disease. We can discuss the current two cases in the light of the previous literature.

Demonstration of equivocal anti-glomerular basement membrane antibody positivity as a non-specific reaction through multiple immunologic assays in a case of pediatric asymptomatic hematuria

BACKGROUND

Anti-glomerular basement membrane (anti-GBM) antibody is essential for the diagnosis of anti-GBM disease. The major epitope consists of the α3 subunits of type IV collagen non-collagenous domain (α 3(IV)NC1). There have been only a few reports of patients false-positive for anti-GBM antibody.

CASE REPORT

We experienced an 8-year-old boy who presented with asymptomatic hematuria followed by positivity for anti-GBM antibody as evaluated by a commercially available chemiluminescent enzyme immunoassay (CLEIA). While his condition remained stable other than continuing hematuria, his anti-GBM antibody titer increased. Further examination of another anti-GBM antibody assay (fluoroenzyme immunoassay) showed negative results. Thus, evaluation of the accuracy of his positivity for anti-GBM antibody was required. We conducted the following examinations: A) enzyme-linked immunosorbent assay, B) immunoblotting for recombinant α 1-5(IV)NC1, and C) immunohistochemical analysis of normal kidney tissue sections. Specimens used for the analysis were sera in A and IgG from the patient in B and C, respectively. As a result, no anti-GBM antibody was detected in A. In B, no band specific to α 1-5(IV)NC1 was observed. In C, the kidney tissue was not stained. Taken together, these results led us to judge the positive anti-GBM result in CLEIA of our patient to be a non-specific reaction.

CONCLUSION

The commercial assays for anti-GBM antibody can lead to false-positive results. We recommend confirmation of anti-GBM antibody positivity through the use of multiple assays in patients demonstrating an atypical clinical course for anti-GBM disease.

Unleashing the power of complement activation: unraveling renal damage in human anti-glomerular basement membrane disease

Anti-glomerular basement membrane (GBM) disease is a rare but life-threatening autoimmune disorder characterized by rapidly progressive glomerulonephritis with or without pulmonary hemorrhage. Renal biopsies of anti-GBM patients predominantly show linear deposition of IgG and complement component 3 (C3), indicating a close association between antigen-antibody reactions and subsequent complement activation in the pathogenesis of the disease. All three major pathways of complement activation, including the classical, lectin, and alternative pathways, are involved in human anti-GBM disease. Several complement factors, such as C3, C5b-9, and factor B, show a positive correlation with the severity of the renal injury and act as risk factors for renal outcomes. Furthermore, compared to patients with single positivity for anti-GBM antibodies, individuals who are double-seropositive for anti-neutrophil cytoplasmic antibody (ANCA) and anti-GBM antibodies exhibit a unique clinical phenotype that lies between ANCA-associated vasculitis (AAV) and anti-GBM disease. Complement activation may serve as a potential "bridge" for triggering both AAV and anti-GBM conditions. The aim of this article is to provide a comprehensive review of the latest clinical evidence regarding the role of complement activation in anti-GBM disease. Furthermore, potential therapeutic strategies targeting complement components and associated precautions are discussed, to establish a theoretical basis for complement-targeted therapies.

Clinical and immunological characteristics of patients with combined anti-glomerular basement membrane disease and IgA nephropathy

Background

The combination of anti-glomerular basement membrane (GBM) disease and immunoglobulin A nephropathy (IgAN) has been well documented in sporadic cases, but lacks overall assessment in large collections. Herein, we investigated the clinical and immunological characteristics and outcome of this entity.

Methods

Seventy-five consecutive patients with biopsy-proven anti-GBM disease from March 2012 to March 2020 were screened. Among them, patients with concurrent IgAN were identified and enrolled. The control group included biopsied classical anti-GBM patients during the same period, excluding patients with IgAN, other glomerular diseases or tumors, or patients with unavailable blood samples and missing data. Serum IgG and IgA autoantibodies against GBM were detected by enzyme-linked immunosorbent assay, as were circulating IgG subclasses against GBM.

Results

Fifteen patients with combined anti-GBM disease and IgAN were identified, accounting for 20% (15/75) of all patients. Among them, nine were male and six were female, with an average (± standard deviation) age of 46.7 ± 17.3 years. Thirty patients with classical anti-GBM disease were enrolled as controls, with 10 males and 20 females at an average age of 45.4 ± 15.3 years. Patients with combined anti-GBM disease and IgAN had restricted kidney involvement without pulmonary hemorrhage. Compared with classical patients, anti-GBM patients with IgAN presented with significantly lower levels of serum creatinine on diagnosis (6.2 ± 2.9 vs 9.5 ± 5.4 mg/dL, P = .03) and less occurrence of oliguria/anuria (20%, 3/15 vs 57%, 17/30, P = .02), but more urine protein excretion [2.37 (1.48, 5.63) vs 1.11 (0.63, 3.90) g/24 h, P = .01]. They showed better kidney outcome during follow-up (ESKD: 47%, 7/15 vs 80%, 24/30, P = .03). The autoantigen and epitope spectrum were comparable between the two groups, but the prevalence of circulating anti-α3(IV)NC1 IgG1 (67% vs 97%, P = .01) and IgG3 (67% vs 97%, P = .01) were lower in patients with IgAN.

Conclusions

Concurrent IgAN was not rare in anti-GBM disease. Patients showed milder kidney lesions and better recovery after immunosuppressive therapies. This might be partly explained by lower prevalence of anti-GBM IgG1 and IgG3 in these patients.

Peptide location fingerprinting identifies structural alterations within basement membrane components in ageing kidney

During ageing, the glomerular and tubular basement membranes (BM) of the kidney undergo a progressive decline in function that is underpinned by histological changes, including glomerulosclerosis and tubular interstitial fibrosis and atrophy. This BM-specific ageing is thought to result from damage accumulation to long-lived extracellular matrix (ECM) protein structures. Determining which BM proteins are susceptible to these structure-associated changes, and the possible mechanisms and downstream consequences, is critical to understand age-related kidney degeneration and to identify markers for therapeutic intervention. Peptide location fingerprinting (PLF) is an emerging proteomic mass spectrometry analysis technique capable of identifying ECM proteins with structure-associated differences that may occur by damage modifications in ageing. Here, we apply PLF as a bioinformatic screening tool to identify BM proteins with structure-associated differences between young and aged human glomerular and tubulointerstitial compartments. Several functional regions within key BM components displayed alterations in tryptic peptide yield, reflecting potential age-dependent shifts in molecular (e.g. laminin-binding regions in agrin) and cellular (e.g. integrin-binding regions in laminins 521 and 511) interactions, oxidation (e.g. collagen IV) and the fragmentation and release of matrikines (e.g. canstatin and endostatin from collagens IV and XVIII). Furthermore, we found that periostin and the collagen IV α2 chain exhibited structure-associated differences in ageing that were conserved between human kidney and previously analysed mouse lung, revealing BM components that harbour shared susceptibilities across species and organs.

Anti-GBM disease with positive serum anti-GBM antibodies but negative IgG deposition: A case report

Anti-glomerular basement membrane antibodies are significantly specific for detecting anti-glomerular basement membrane disease. These antibodies are typically targeted against the non-collagenous (NC1) domain of the alpha 3 chain of type IV collagen and, to a lesser extent, the α4(IV) or α5(IV) chains, which create a triple-helical structure in the glomerular basement membrane. The modification of the hexameric structure of NC1 (α3(IV)) results in the exposure of new epitopes, leading to an immune reaction and the subsequent deposition of linear antibodies along the glomerular basement membrane, culminating in crescentic glomerulonephritis. Anti-glomerular basement membrane antibodies that are positive are believed to be pathogenic and capable of binding to the glomerular basement membrane in vivo, particularly in the context of rapidly progressive glomerulonephritis. Herein, we present a patient with positive serum anti-glomerular basement membrane antibodies but negative IgG deposition. The current findings are significant for raising physicians' awareness of the probable errors in detecting anti-glomerular basement membrane antibody disease as a possible cause of irreversible kidney failure.

Identification of unique α4 chain structure and conserved antiangiogenic activity of α3NC1 type IV collagen in zebrafish

BACKGROUND

Type IV collagen is an abundant component of basement membranes in all multicellular species and is essential for the extracellular scaffold supporting tissue architecture and function. Lower organisms typically have two type IV collagen genes, encoding α1 and α2 chains, in contrast with the six genes in humans, encoding α1-α6 chains. The α chains assemble into trimeric protomers, the building blocks of the type IV collagen network. The detailed evolutionary conservation of type IV collagen network remains to be studied.

RESULTS

We report on the molecular evolution of type IV collagen genes. The zebrafish α4 non-collagenous (NC1) domain, in contrast with its human ortholog, contains an additional cysteine residue and lacks the M93 and K211 residues involved in sulfilimine bond formation between adjacent protomers. This may alter α4 chain interactions with other α chains, as supported by temporal and anatomic expression patterns of collagen IV chains during the zebrafish development. Despite the divergence between zebrafish and human α3 NC1 domain (endogenous angiogenesis inhibitor, Tumstatin), the zebrafish α3 NC1 domain exhibits conserved antiangiogenic activity in human endothelial cells.

CONCLUSIONS

Our work supports type IV collagen is largely conserved between zebrafish and humans, with a possible difference involving the α4 chain.

Atypical Anti-Glomerular Basement Membrane Disease

Atypical anti-glomerular basement membrane (anti-GBM) disease is characterized by linear immunoglobulin G (IgG) deposition along the GBM without circulating IgG anti-GBM antibodies. Compared to classic anti-GBM disease, atypical anti-GBM disease tends to be milder with a more indolent course in certain cases. Moreover, pathologic disease pattern is much more heterogenous in atypical anti-GBM disease than in the classic type, which is uniformly characterized by diffuse crescentic and necrotizing glomerulonephritis. Although there is no single well-established target antigen in atypical anti-GBM disease, the target antigen (within the GBM) and the autoantibody type are hypothesized to be different from the classic type. Some patients have the same antigen as the Goodpasture antigen that are detected only by a highly sensitive technique (biosensor analysis). Some cases of atypical anti-GBM disease have autoantibodies of a different subclass restriction like IgG4, or of monoclonal nature. Antibodies targeting antigen/epitope structure other than the Goodpasture antigen can be detected using modified assays in some cases. Patients with IgA- and IgM-mediated anti-GBM disease are known to have negative circulating antibodies because conventional assays do not detect these classes of antibodies. A significant proportion of cases with atypical anti-GBM disease do not have any identifiable antibodies despite extensive evaluation. Nevertheless, extensive evaluation of atypical autoantibodies using modified assays and sensitive techniques should be attempted, if feasible. This review summarizes the recent literature on atypical anti-GBM disease.

Expert perspectives on pathological findings in vasculitis

Pathological findings are important in the diagnosis of vasculitis. However, due to the rarity of the disease, standard textbooks usually devote only a few pages to this topic, and this makes it difficult for clinicians not specializing in vasculitis to fully understand the pathological findings in vasculitis. To address the paucity of information, we present representative pathological findings in vasculitis classified in the 2012 Revised International Chapel Hill Consensus Conference Nomenclature of Vasculitides (CHCC2012). The CHCC2012 classifies 26 vasculitides into seven categories: (1) large-vessel vasculitis, (2) medium-vessel vasculitis, (3) small-vessel vasculitis, including antineutrophil cytoplasmic antibody-associated vasculitis and immune complex small-vessel vasculitis, (4) variable-vessel vasculitis, (5) single-organ vasculitis, (6) vasculitis associated with systemic disease, and (7) vasculitis associated with probable aetiology. Moreover, representative pathological findings of vasculitis-related diseases and non-inflammatory vasculopathy not mentioned in the CHCC2012 are also presented. This will be useful for clinicians to refer to typical pathological findings of vasculitis in daily practice.

Anti-glomerular basement membrane vasculitis

Antiglomerular basement membrane disease (anti-GBM) is a rare life-threatening autoimmune vasculitis that involves small vessels and it is characterized by circulating autoantibodies directed against type IV collagen antigens expressed in glomerular and alveolar basement membrane. The typical clinical manifestations are the rapidly progressive glomerulonephritis and the alveolar hemorrhage. The diagnosis is usually confirmed by the detection of anti-GBM circulating antibodies. If not rapidly recognized, anti-GBM disease can lead to end stage kidney disease (ESKD). An early diagnosis and prompt treatment with immunosuppressive therapies and plasmapheresis are crucial to prevent a poor outcome. In this review, we discuss the primary form of anti-GBM (the so called Goodpasture syndrome) but also cases associated with other autoimmune diseases such as antineutrophil-cytoplasmic-antibody (ANCA) vasculitis, membranous nephropathy, IgA nephritis and systemic lupus erythematosus (SLE), as well as the few cases of anti-GBM vasculitis complicating kidney transplantation in the Alport syndrome.

Autoimmunity in Anti-Glomerular Basement Membrane Disease: A Review of Mechanisms and Prospects for Immunotherapy

Anti-glomerular basement membrane (anti-GBM) disease is an organ-specific autoimmune disorder characterized by autoantibodies against the glomerular and alveolar basement membranes, leading to rapidly progressive glomerulonephritis and severe alveolar hemorrhage. The noncollagenous domain of the α3 chain of type IV collagen, α3(IV)NC1, contains the main target autoantigen in this disease. Epitope mapping studies of α3(IV)NC1 have identified several nephritogenic epitopes and critical residues that bind to autoantibodies and trigger anti-GBM disease. The discovery of novel target antigens has revealed the heterogeneous nature of this disease. In addition, both epitope spreading and mimicry have been implicated in the pathogenesis of anti-GBM disease. Epitope spreading refers to the development of autoimmunity to new autoepitopes, thus worsening disease progression, whereas epitope mimicry, which occurs via sharing of critical residues with microbial peptides, can initiate autoimmunity. An understanding of these autoimmune responses may open opportunities to explore potential new therapeutic approaches for this disease. We review how current advances in epitope mapping, identification of novel autoantigens, and the phenomena of epitope spreading and mimicry have heightened the understanding of autoimmunity in the pathogenesis of anti-GBM disease, and we discuss prospects for immunotherapy.

The neutrophil: A key resourceful agent in immune‐mediated vasculitis

The term "vasculitis" refers to a group of rare immune-mediated diseases characterized by the dysregulated immune system attacking blood vessels located in any organ of the body, including the skin, lungs, and kidneys. Vasculitides are classified according to the size of the vessel that is affected. Although this observation is not specific to small-, medium-, or large-vessel vasculitides, patients show a high circulating neutrophil-to-lymphocyte ratio, suggesting the direct or indirect involvement of neutrophils in these diseases. As first responders to infection or inflammation, neutrophils release cytotoxic mediators, including reactive oxygen species, proteases, and neutrophil extracellular traps. If not controlled, this dangerous arsenal can injure the vascular system, which acts as the main transport route for neutrophils, thereby amplifying the initial inflammatory stimulus and the recruitment of immune cells. This review highlights the ability of neutrophils to "set the tone" for immune cells and other cells in the vessel wall. Considering both their long-established and newly described roles, we extend their functions far beyond their direct host-damaging potential. We also review the roles of neutrophils in various types of primary vasculitis, including immune complex vasculitis, anti-neutrophil cytoplasmic antibody-associated vasculitis, polyarteritis nodosa, Kawasaki disease, giant cell arteritis, Takayasu arteritis, and Behçet's disease.

A case report of atypical anti-glomerular basement membrane disease

Background

Anti-glomerular basement membrane (anti-GBM) disease is characterized by crescentic necrotizing glomerulonephritis, with linear deposits of immunoglobulin G (IgG) in the GBM. Classic anti-GBM disease is clinically associated with rapidly progressive glomerulonephritis with or without pulmonary hemorrhage. Some patients have a better renal prognosis and milder symptoms than those with classic anti-GBM disease, which is termed atypical anti-GBM disease.

Case presentation

A 43-year-old Japanese woman was admitted to our hospital complaining of hematuria that had persisted for more than one month. Serological examination revealed negativity for anti-nuclear, anti-neutrophilic cytoplasmic, and anti-GBM antibodies. However, renal biopsy showed cellular crescents. Immunofluorescence revealed strong diffuse linear capillary loop staining for IgG. An indirect immunofluorescence antibody method was performed by applying the patient serum to normal kidney tissue to confirm the presence of autoantibodies binding to the GBM. Using this method, anti-GBM antibodies were detected. The patient was treated with high-dose steroids, cyclophosphamide, and plasma exchange. Aggressive treatment resolved proteinuria and hematuria and improved renal function.

Conclusions

Renal biopsy is crucial in the diagnosis of anti-GBM disease, especially when serological tests are negative. Accurately identifying the presence of anti-GBM disease is important to initiate optimal treatment.

Triple Jeopardy: Rapidly Progressive Glomerulonephritis Induced by Triple Seropositive Disease—A Rare Case

The double-positive disease is the co-occurrence of antiglomerular basement membrane (anti-GBM) disease and antineutrophil cytoplasmic antibodies (ANCAs) and is an uncommon cause of renal failure. Our case of triple-positive disease is an even rarer cause of isolated renal failure, as it includes anti-GBM, antimyeloperoxidase (MPO), and antiproteinase 3 (PR3). We present a case of a 62-year-old Caucasian male with a history of multiple comorbidities, who presented to the emergency department (ED) with worsening dyspnea on exertion that started about one month prior to admission. He was found to be in renal failure secondary to triple-positive disease. We believe that the likely mechanism of our patient's triple-positive disease was a drug-induced ANCA vasculitis overlapping with Goodpasture's syndrome. We believe our case to be a valuable addition to the literature as it is a rare overlap syndrome without a previously established disease course or etiology.

Anti-glomerular basement membrane disease in HLA-identical non-twin siblings

Anti glomerular basement membrane disease (AGBM) is an autoinmune disorder characterised by the presence of anti-glomerular basement membrane (Anti-GBM) antibodies, alveolar hemorrhage, necrotizing glomerulonephritis, and linear deposition of immunoglobulins through direct inmunofluorescence. Genetic predisposition, among other factors, plays an important role in the development of the disease. Previous studies have shown that HLA-DR15 and HLA-DR4 increase the risk of presenting it, while HLA-DR1 and HLA-DR7 protect against its development. We describe the first case of two non-twin siblings with AGBM and identical HLA, with HLA-DR4 as risk factor and HLA-DR7 as protection factor. We propose the importance of analysing HLA in siblings of patients with AGBM, to determine the degree of genetic susceptibility and to carry out a close follow-up on them, with the aim of achieving an early diagnosis and treatment in case of presenting the disease.

Renal diseases and the role of complement: Linking complement to immune effector pathways and therapeutics

The complement system is an ancient and phylogenetically conserved key danger sensing system that is critical for host defense against pathogens. Activation of the complement system is a vital component of innate immunity required for the detection and removal of pathogens. It is also a central orchestrator of adaptive immune responses and a constituent of normal tissue homeostasis. Once complement activation occurs, this system deposits indiscriminately on any cell surface in the vicinity and has the potential to cause unwanted and excessive tissue injury. Deposition of complement components is recognized as a hallmark of a variety of kidney diseases, where it is indeed associated with damage to the self. The provenance and the pathophysiological role(s) played by complement in each kidney disease is not fully understood. However, in recent years there has been a renaissance in the study of complement, with greater appreciation of its intracellular roles as a cell-intrinsic system and its interplay with immune effector pathways. This has been paired with a profusion of novel therapeutic agents antagonizing complement components, including approved inhibitors against complement components (C)1, C3, C5 and C5aR1. A number of clinical trials have investigated the use of these more targeted approaches for the management of kidney diseases. In this review we present and summarize the evidence for the roles of complement in kidney diseases and discuss the available clinical evidence for complement inhibition.

Case Report: Eculizumab and ECMO Rescue Therapy of Severe ARDS in Goodpasture Syndrome

Introduction: Goodpasture's syndrome is a life-threatening autoimmune type IV collagen disease characterized by the presence anti-glomerular basement membrane antibodies, rapid progressive glomerulonephritis and/or pulmonary hemorrhage. Methods: Here, we describe new therapeutic options, which take recent advances in unraveling Goodpasture's pathogenesis into account. Results: In a 17-year old male, severe Goodpasture's syndrome resulted in acute respiratory distress syndrome (ARDS). Within 1 day after hospital admission, the patient required extracorporeal membrane oxygenation (ECMO). Despite steroid-pulse and plasmapheresis, ARDS further deteriorated. Eleven days after admission, the patient was in a pre-final stage. At last, we decided to block the complement-driven lung damage by Eculizumab. Three days after, lung-failure has stabilized in a way allowing us to initiate Cyclophosphamide-therapy. As mechanical ventilation further triggers Goodpasture-epitope exposure, the patient was taken from pressure support - breathing spontaneously by the help of maintaining ECMO therapy. After a total of 24 days, ECMO could be stopped and pulmonary function further recovered. Conclusions: In conclusion, our findings suggest that life-threatening organ-damage in Goodpasture's syndrome can be halted by Eculizumab as well as by lung-protective early withdrawal from pressure support by the help of ECMO. Both therapeutic options serve as new tools in otherwise hopeless situations to prevent further organ-damage and to gain time until the established immunosuppressive therapy works in otherwise lethal autoimmune-diseases.

Advances in Understanding of Pathogenesis and Treatment of Immune-Mediated Kidney Disease: A Review

There continues to be rapid advancement in our understanding of the pathogenesis of immune-mediated kidney disease. This progress has culminated in the development of multiple therapeutic agents that have consistently improved renal and patient outcomes. The focus of this review is to discuss these recent advancements in immune-mediated kidney disease via the lens of direct and indirect immune-mediated mechanisms. In the direct immune-mediated disease, recently described antigens in anti-glomerular basement membrane (GBM) disease and membranous nephropathy are discussed, along with new therapeutic regimens in membranous nephropathy and focal segmental glomerulosclerosis. From an indirect immune-mediated disease standpoint, recent pivotal trials in antineutrophil cytoplasmic antibody vasculitis, lupus nephritis, and IgA nephropathy are examined from a real-world practice perspective. New molecular pathways in various disorders of alternate complement pathway are described, which in turn have led to development of various experimental therapies. In addition, pivotal and ongoing therapeutic trials in the aforementioned diseases are presented.

Anti-glomerular basement membrane disease in HLA-identical non-twin siblings

Anti-glomerular basement membrane disease (AGBM) is an autoinmune disorder characterized by the presence of anti-glomerular basement membrane (anti-GBM) antibodies, alveolar hemorrhage, necrotizing glomerulonephritis, and linear deposition of immunoglobulins through direct inmunofluorescence. Genetic predisposition, among other factors, plays an important role in the development of the disease. Previous studies have shown that HLA-DR15 and HLA-DR4 increase the risk of presenting it, while HLA-DR1 and HLA-DR7 protect against its development. We describe the first case of two non-twin siblings with AGBM and identical HLA, with HLA-DR4 as risk factor and HLA-DR7 as protection factor. We propose the importance of analyzing HLA in siblings of patients with AGBM, to determine the degree of genetic susceptibility and to carry out a close follow-up on them, with the aim of achieving an early diagnosis and treatment in case of presenting the disease.

Anti-glomerular basement membrane disease (Goodpasture disease): From pathogenesis to plasma exchange to IdeS

Anti-glomerular basement membrane (GBM) disease (Goodpasture disease) often presents with severe kidney failure and pulmonary hemorrhage. Anti-GBM antibodies are pathogenic, and other autoantibodies such as laminin-521 have been identified recently, potentially indicating a subset with a more severe disease phenotype and poor prognosis. Around 30%-40% of patients are also anti-neutrophil cytoplasmatic antibody (ANCA)-positive and this subset combines features of anti-GBM disease and ANCA-associated vasculitis, with particular impact on long-term treatment. A combination of therapeutic plasma exchange (or immunoadsorption), cyclophosphamide, and glucocorticoids is considered standard of care management, but despite early initiation, patients with poor prognostic factors often remain dialysis dependent. Imlifidase (IdeS), capable to cleave IgG within hours, has been tested in a phase II trial. Among 15 patients, 10 with poor prognosis at baseline (eGFR <15 ml/min/1.73 m² ) were dialysis independent at 6 months. Further developments are needed to refine treatment approaches in anti-GBM disease.

Laminin-521 is a Novel Target of Autoantibodies Associated with Lung Hemorrhage in Anti-GBM Disease

BACKGROUND

Antiglomerular basement membrane (anti-GBM) disease is characterized by GN and often pulmonary hemorrhage, mediated by autoantibodies that typically recognize cryptic epitopes within α345(IV) collagen-a major component of the glomerular and alveolar basement membranes. Laminin-521 is another major GBM component and a proven target of pathogenic antibodies mediating GN in animal models. Whether laminin-521 is a target of autoimmunity in human anti-GBM disease is not yet known.

METHODS

A retrospective study of circulating autoantibodies from 101 patients with anti-GBM/Goodpasture's disease and 85 controls used a solid-phase immunoassay to measure IgG binding to human recombinant laminin-521 with native-like structure and activity.

RESULTS

Circulating IgG autoantibodies binding to laminin-521 were found in about one third of patients with anti-GBM antibody GN, but were not detected in healthy controls or in patients with other glomerular diseases. Autoreactivity toward laminin-521 was significantly more common in patients with anti-GBM GN and lung hemorrhage, compared with those with kidney-limited disease (51.5% versus 23.5%, P=0.005). Antilaminin-521 autoantibodies were predominantly of IgG1 and IgG4 subclasses and significantly associated with lung hemorrhage (P=0.005), hemoptysis (P=0.008), and smoking (P=0.01), although not with proteinuria or serum creatinine at diagnosis.

CONCLUSIONS

Besides α345(IV) collagen, laminin-521 is another major autoantigen targeted in anti-GBM disease. Autoantibodies to laminin-521 may have the potential to promote lung injury in anti-GBM disease by increasing the total amount of IgG bound to the alveolar basement membranes.

Kidney organoid systems for studies of immune-mediated kidney diseases: challenges and opportunities

Acute and chronic kidney diseases are major contributors to morbidity and mortality in the global population. Many nephropathies are considered to be immune-mediated with dysregulated immune responses playing an important role in the pathogenesis. At present, targeted approaches for many kidney diseases are still lacking, as the underlying mechanisms remain insufficiently understood. With the recent development of organoids—a three-dimensional, multicellular culture system, which recapitulates important aspects of human tissues—new opportunities to investigate interactions between renal cells and immune cells in the pathogenesis of kidney diseases arise. To date, kidney organoid systems, which reflect the structure and closer resemble critical aspects of the organ, have been established. Here, we highlight the recent advances in the development of kidney organoid models, including pluripotent stem cell-derived kidney organoids and primary epithelial cell-based tubuloids. The employment and further required advances of current organoid models are discussed to investigate the role of the immune system in renal tissue development, regeneration, and inflammation to identify targets for the development of novel therapeutic approaches of immune-mediated kidney diseases.

A Novel Insight into the Role of PLA2R and THSD7A in Membranous Nephropathy

Membranous nephropathy (MN) is an organ-restricted autoimmune disease mainly caused by circulating autoantibodies against podocyte antigens, including the M-type phospholipase A2 receptor (PLA2R) and thrombospondin domain-containing 7A (THSD7A). Antibodies against PLA2R are present in 70%-80% and against THSD7A in 2% of adult patients, which provides a paradigm shift in molecular diagnosis and management monitoring. Both antigens share some similar characteristics: they are expressed by podocytes and have wide tissue distributions; they are bound by autoantibodies only under nonreducing conditions, and the subtype of most autoantibodies is IgG4. However, the factors triggering autoantibody production as well as the association among air pollution, malignancy, and the pathogenesis of MN remain unclear. In this review, we discuss the similarity between the pathological mechanisms triggered by disparate antigens and their associated diseases. Furthermore, we demonstrated the possibility that PM2.5, malignancy, and gene expression specifically induce exposure of these antigens through conformational changes, molecular mimicry, or increased expression eliciting autoimmune responses. Thus, this review provides novel insights into the pathological mechanism of MN.

Neutralization of IL-6 inhibits formation of autoreactive TH17 cells but does not prevent loss of renal function in experimental autoimmune glomerulonephritis

In anti-glomerular basement membrane glomerulonephritis (anti-GBM GN), antibodies and T cells directed against the Goodpasture antigen, the non-collagenous domain of the α3-chain of type IV collagen (α3(IV)NC1), provoke renal inflammation resulting in rapidly progressing crescentic GN. Interleukin 6 (IL-6) is a pleiotropic cytokine with both pro- and anti-inflammatory activities, and IL-6 blockade is successfully used for treatment of diseases associated with acute and chronic inflammation. However, the role of IL-6 in anti-GBM GN is unclear. Here, we use the mouse model of experimental autoimmune glomerulonephritis (EAG) to study the role of IL-6 in anti-GBM GN. DBA/1J mice were immunized with α3(IV)NC1 and developed fatal crescentic GN. Treatment of mice with neutralizing anti-IL-6 antibodies impaired the generation of α3(VI)NC1-specific TH1 and TH17 cells. However, despite lasting reduction of the TH17 cell response, antibody treatment did not prevent crescentic GN. Antibody treatment was also ineffective in a therapeutic setting with pre-existing autoantibodies and T cells. In conclusion, our results indicate that although the blockade of IL-6 impairs the development of autoimmunity against α3(VI)NC1, this treatment does not ameliorate crescentic GN both in a preemptive and a therapeutic approach.

Anti-glomerular basement membrane disease mediated by IgG and IgA: a case report

Background

Anti-glomerular basement membrane (anti-GBM) disease is a rare autoimmune condition responsible for rapidly progressive glomerulonephritis. This disease is usually mediated by IgG autoantibodies against the noncollagenous domain of the α3(IV) collagen chain. In rare cases, IgA or IgM anti-GBM antibodies are involved. This raises the question of whether there are different types of antibody-mediated anti-GBM disease at the same time.

Case report

A 37-year-old woman with anti-GBM disease mediated by IgG and IgA. The patient developed rapidly progressive glomerulonephritis with nephrotic syndrome. Indirect immunofluorescence analysis indicated the presence of IgG and IgA antibodies reactive with a basement membrane component, identified by enzyme-linked immunoadsorbent assay and Western blotting as the α3(IV) collagen chain. After plasmapheresis and immunotherapy (steroids and cyclophosphamide), much improved the massive proteinuria and renal function. Follow up to date, she had normal renal function without proteinuria.

Conclusions

This is the first case report of anti-GBM disease mediated by IgG and IgA. If the clinical presentation and histopathological findings are suggestive of atypical anti-GBM disease, alternative laboratory tests such as Western blotting analysis can be used to confirm the diagnosis.

Recurrent, Atypical Anti-Glomerular Basement Membrane Disease

Anti-glomerular basement membrane disease (GBM) (Goodpasture's disease) typically presents with acute manifestations of rapidly progressive glomerulonephritis often accompanied by lung haemorrhage. Anti-GBM disease is usually monophasic. However, atypical presentations with indolent renal involvement are being increasingly recognized. Herein we report a patient who presented with lung haemorrhage, minimal renal involvement, and negative result for serum anti-GBM antibody, while immunofluorescence examination of the renal biopsy provided the diagnosis leading to the institution right treatment with excellent response. Interestingly, he had presented 10 years earlier with lung hemorrhage, more significant renal involvement clinically and histologically, with positive serum anti-GBM antibody. The present case is intended to increase our awareness regarding the variable presentations of anti-GBM disease, such as with negative serology and recurrence of anti-GBM disease. The presentation of anti-GBM nephritis with non-proliferative, non-crescentic glomerulonephritis is also highlighted. The possible explanations for negative serum anti-GBM antibody are explored with a brief review of literature.

Collagen IVα345 dysfunction in glomerular basement membrane diseases. II. Crystal structure of the α345 hexamer

Our recent work identified a genetic variant of the α345 hexamer of the collagen IV scaffold that is present in patients with glomerular basement membrane diseases, Goodpasture’s disease (GP) and Alport syndrome (AS), and phenocopies of AS in knock-in mice. To understand the context of this “Zurich” variant, an 8-amino acid appendage, we developed a construct of the WT α345 hexamer using the single-chain NC1 trimer technology, which allowed us to solve a crystal structure of this key connection module. The α345 hexamer structure revealed a ring of 12 chloride ions at the trimer–trimer interface, analogous to the collagen α121 hexamer, and the location of the 170 AS variants. The hexamer surface is marked by multiple pores and crevices that are potentially accessible to small molecules. Loop-crevice-loop features constitute bioactive sites, where pathogenic pathways converge that are linked to AS and GP, and, potentially, diabetic nephropathy. In Pedchenko et al., we demonstrate that these sites exhibit conformational plasticity, a dynamic property underlying assembly of bioactive sites and hexamer dysfunction. The α345 hexamer structure is a platform to decipher how variants cause AS and how hypoepitopes can be triggered, causing GP. Furthermore, the bioactive sites, along with the pores and crevices on the hexamer surface, are prospective targets for therapeutic interventions.

Collagen IVα345 dysfunction in glomerular basement membrane diseases. III. A functional framework for α345 hexamer assembly

We identified a genetic variant, an 8-residue appendage, of the α345 hexamer of collagen IV present in patients with glomerular basement membrane diseases, Goodpasture’s disease and Alport syndrome, and determined the long-awaited crystal structure of the hexamer. We sought to elucidate how variants cause glomerular basement membrane disease by exploring the mechanism of the hexamer assembly. Chloride ions induced in vitro hexamer assembly in a composition-specific manner in the presence of equimolar concentrations of α3, α4, and α5 NC1 monomers. Chloride ions, together with sulfilimine crosslinks, stabilized the assembled hexamer. Furthermore, the chloride ion–dependent assembly revealed the conformational plasticity of the loop-crevice-loop bioactive sites, a critical property underlying bioactivity and pathogenesis. We explored the native mechanism by expressing recombinant α345 miniprotomers in the cell culture and characterizing the expressed proteins. Our findings revealed NC1-directed trimerization, forming protomers inside the cell; hexamerization, forming scaffolds outside the cell; and a Cl gradient–signaled hexamerization. This assembly detail, along with a crystal structure, provides a framework for understanding hexamer dysfunction. Restoration of the native conformation of bioactive sites and α345 hexamer replacement are prospective approaches to therapeutic intervention.

Collagen IVα345 dysfunction in glomerular basement membrane diseases. I. Discovery of a COL4A3 variant in familial Goodpasture's and Alport diseases

Diseases of the glomerular basement membrane (GBM), such as Goodpasture’s disease (GP) and Alport syndrome (AS), are a major cause of chronic kidney failure and an unmet medical need. Collagen IV^α345 is an important architectural element of the GBM that was discovered in previous research on GP and AS. How this collagen enables GBM to function as a permselective filter and how structural defects cause renal failure remain an enigma. We found a distinctive genetic variant of collagen IV^α345 in both a familial GP case and four AS kindreds that provided insights into these mechanisms. The variant is an 8-residue appendage at the C-terminus of the α3 subunit of the α345 hexamer. A knock-in mouse harboring the variant displayed GBM abnormalities and proteinuria. This pathology phenocopied AS, which pinpointed the α345 hexamer as a focal point in GBM function and dysfunction. Crystallography and assembly studies revealed underlying hexamer mechanisms, as described in Boudko et al. and Pedchenko et al. Bioactive sites on the hexamer surface were identified where pathogenic pathways of GP and AS converge and, potentially, that of diabetic nephropathy (DN). We conclude that the hexamer functions include signaling and organizing macromolecular complexes, which enable GBM assembly and function. Therapeutic modulation or replacement of α345 hexamer could therefore be a potential treatment for GBM diseases, and this knock-in mouse model is suitable for developing gene therapies.

Australia and New Zealand renal gene panel testing in routine clinical practice of 542 families

Genetic testing in nephrology clinical practice has moved rapidly from a rare specialized test to routine practice both in pediatric and adult nephrology. However, clear information pertaining to the likely outcome of testing is still missing. Here we describe the experience of the accredited Australia and New Zealand Renal Gene Panels clinical service, reporting on sequencing for 552 individuals from 542 families with suspected kidney disease in Australia and New Zealand. An increasing number of referrals have been processed since service inception with an overall diagnostic rate of 35%. The likelihood of identifying a causative variant varies according to both age at referral and gene panel. Although results from high throughput genetic testing have been primarily for diagnostic purposes, they will increasingly play an important role in directing treatment, genetic counseling, and family planning.

Sequential occurrence of microscopic polyangiitis and anti-glomerular basement membrane disease in a patient with small cell lung cancer: a case report

Background

The association between a preceding malignancy and the onset of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) has been reported in several studies. While the co-existence of ANCA and anti-glomerular basement membrane (GBM) antibodies in an individual patient is not a common occurrence, this double-positive disease currently has no optimal treatment method. Herein, we report a case of a double-positive disease involving the sequential development of acute kidney injury (AKI) and diffuse alveolar hemorrhage (DAH) in a patient with small cell lung cancer (SCLC).

Case presentation

A 75-year-old Japanese woman was diagnosed with small cell lung cancer (cT3N2M1b cStage IV) and received chemotherapy. After one cycle of chemotherapy, she experienced fever and malaise. Her serum creatinine level rapidly increased, and she tested positive for myeloperoxidase (MPO)-ANCA and anti-GBM antibody. She was diagnosed with AKI due to microscopic polyangiitis (MPA) based on renal biopsy. Corticosteroid therapy was initiated, which improved her renal dysfunction. Eight days after she was discharged from the hospital, she complained of dyspnea and bloody sputum, and her condition rapidly progressed to respiratory failure. Upon chest imaging, ground-glass opacities were seen in her bilateral lower lungs. Laboratory examinations after admission revealed a lower MPO-ANCA titer and an elevated anti-GBM antibody titer compared to her previous admission. We diagnosed her with DAH due to an anti-GBM disease. After corticosteroid pulse therapy, plasma exchange was performed five times; her oxygen saturation and chest radiologic findings improved gradually. Following five cycles of plasma exchange, her oxygen saturation recovered to 95% in room air.

Conclusions

To our knowledge, this is the first reported case of vasculitis caused by MPA and anti-GBM disease leading to the development of AKI and DAH during treatment of SCLC. SCLC, MPA, and anti-GBM disease may occur sequentially. A double-positive disease might have a worse prognosis; therefore, intensive therapy is more likely to achieve a better outcome.

The clinical and immunological features of the post-extracorporeal shock wave lithotripsy anti-glomerular basement membrane disease

Introduction

Extracorporeal shock wave lithotripsy (ESWL) is a noninvasive modality to treat urolithiasis, with complications including tissue damage and hematoma of kidney parenchyma. Anti-glomerular basement membrane (GBM) disease is suggested to be a rare complication of ESWL since it was reported in several cases to occur after ESWL. However, the clinical and immunological features of the ESWL-associated anti-GBM disease have not been fully investigated so far.

Case Presentation

Here, we present the clinical, pathological, and immunological characteristics of three patients with the post-ESWL anti-GBM disease in our hospital. Anti-GBM disease occurred within a median of 22 months after ESWL treatment. It presented with similar clinical features to the classic anti-GBM disease, including fever, gross hematuria, and rapidly progressive glomerulonephritis (RPGN) with poor renal prognosis. Sera from all patients recognized the α3(IV)NC1 in GBM, but with IgG2 and IgG4 as the dominant IgG subclasses.

Conclusion

Although further exploration is required to prove the causal relationship in this rare condition, our study reminds physicians that patients developing acute renal insufficiency after ESWL should lead to the suspicion of anti-GBM disease and in-time diagnosis and treatment.

Experimental Antiglomerular Basement Membrane GN Induced by a Peptide from Actinomyces

BACKGROUND

Antiglomerular basement membrane (anti-GBM) disease is associated with HLA-DRB1*1501 (the major predisposing genetic factor in the disease), with α3_127-148 as a nephritogenic T and B cell epitope. Although the cause of disease remains unclear, the association of infections with anti-GBM disease has been long suspected.

METHODS

To investigate whether microbes might activate autoreactive T and B lymphocytes via molecular mimicry in anti-GBM disease, we used bioinformatic tools, including BLAST, SYFPEITHI, and ABCpred, for peptide searching and epitope prediction. We used sera from patients with anti-GBM disease to assess peptides recognized by antibodies, and immunized WKY rats and a humanized mouse model (HLA-DR15 transgenic mice) with each of the peptide candidates to assess pathogenicity.

RESULTS

On the basis of the critical motif, the bioinformatic approach identified 36 microbial peptides that mimic human α3_127-148. Circulating antibodies in sera from patients with anti-GBM recognized nine of them. One peptide, B7, derived from Actinomyces species, induced proteinuria, linear IgG deposition on the GBM, and crescent formation when injected into WKY rats. The antibodies to B7 also targeted human and rat α3_127-148. B7 induced T cell activation from human α3_127-148-immunized rats. T cell responses to B7 were detected in rats immunized by Actinomyces lysate proteins or recombinant proteins. We confirmed B7's pathogenicity in HLA-DR15 transgenic mice that developed kidney injury similar to that observed in α3_135-145-immunized mice.

CONCLUSIONS

Sera from patients with anti-GBM disease recognized microbial peptides identified through a bioinformatic approach, and a peptide from Actinomyces induced experimental anti-GBM GN by T and B cell crossreactivity. These studies demonstrate that anti-GBM disease may be initiated by immunization with a microbial peptide.

Anti-glomerular Basement Membrane Disease: What Have We Learned?

Since the first clinicopathologic description by Ernest Goodpasture of a patient whom he considered to have died of influenza in 1919, substantial progress has been made in our knowledge of anti-glomerular basement membrane disease. This has led to a significant decrease in the morbidity and mortality associated with this disease. In this paper, we aim to review the literature that has enhanced our understanding of classic anti-glomerular basement membrane disease and its clinic-pathologic variants in the key areas of immunopathogenesis and histopathology. We also summarize varied clinical presentations and therapeutic strategies.

Absence of Anti-Glomerular Basement Membrane Antibodies in 200 Patients With Systemic Lupus Erythematosus With or Without Lupus Nephritis: Results of the GOODLUPUS Study

Introduction

Anti-glomerular basement membrane (GBM) antibodies are pathogenic antibodies first detected in renal-limited anti-GBM disease and in Goodpasture disease, the latter characterized by rapidly progressive crescentic glomerulonephritis combined with intra-alveolar hemorrhage. Studies have suggested that anti-GBM antibody positivity may be of interest in lupus nephritis (LN). Moreover, severe anti-GBM vasculitis cases in patients with systemic lupus erythematosus (SLE) have been described in the literature, but few studies have assessed the incidence of anti-GBM antibodies in SLE patients.

Objective

The main study objective was to determine if positive anti-GBM antibodies were present in the serum of SLE patients with or without proliferative renal damage and compared to a healthy control group.

Methodology

This retrospective study was performed on SLE patients’ sera from a Franco-German European biobank, developed between 2011 and 2014, from 17 hospital centers in the Haut-Rhin region. Patients were selected according to their renal involvement, and matched by age and gender. The serum from healthy voluntary blood donors was also tested. Anti-GBM were screened by fluorescence enzyme immunoassay (FEIA), and then by indirect immunofluorescence (IIF) in case of low reactivity detection (titer >6 U/ml).

Results

The cohort was composed of 100 SLE patients with proliferative LN (27% with class III, 67% with class IV, and 6% with class V), compared to 100 SLE patients without LN and 100 controls. Patients were mostly Caucasian and met the ACR 1997 criteria and/or the SLICC 2012 criteria. Among the 300 tested sera, no significant levels of anti-GBM antibodies were detected (>10 U/ml) by the automated technique, three sera were found “ambivalent” (>7 U/ml): one in the SLE with LN group and two in the SLE without LN group. Subsequent IIF assays did not detect anti-GBM antibodies.

Conclusion

Anti-GBM antibodies were not detected in the serum of Caucasian patients with SLE, even in case of renal involvement, a situation favoring the antigenic exposure of glomerular basement membranes. Our results reaffirm the central role of anti-GBM antibodies as a specific diagnostic biomarker for Goodpasture vasculitis and therefore confirm that anti-GBM antibody must not be carried out in patients with SLE (with or without LN) in the absence of disease-suggestive symptoms.

The development of rapidly progressive glomerulonephritis associated with both antineutrophil cytoplasmic antibody-associated vasculitis and anti-glomerular basement membrane nephritis in the course of nontuberculous mycobacterium infection: a case report

BACKGROUND

Antineutrophil cytoplasmic antibodies (ANCA) and Anti-glomerular basement membrane (GBM) antibodies often induce rapidly progressive glomerulonephritis (RPGN). Some reports have demonstrated RPGN with the sequential appearance of ANCA then anti-GBM antibodies, suggesting that ANCA may induce the development of anti-GBM antibodies. Whereas, many reports have shown that the development of ANCA is associated with various infectious diseases, such as non-tuberculous mycobacterial infection.

CASE PRESENTATION

A 65-year-old woman with pulmonary non-tuberculous mycobacterial (NTM) infection was monitored without treatment. One year later, serum myeloperoxidase (MPO)- ANCA were elevated (14.1 U/mL (normal value < 3.0 U/ml)). A high fever and RPGN appeared 1 year later, and serum MPO-ANCAs were 94.1 U/mL. Anti-GBM antibodies were also detected. A renal biopsy revealed crescentic glomerulonephritis with linear deposits of IgG and C3c along the GBM and interstitial inflammation with endarteritis of arterioles. The diagnosis was RPGN associated with anti-GBM nephritis and ANCA-associated vasculitis.

CONCLUSION

This report shows that preceding NTM infection may have induced ANCA and anti-GBM antibodies and caused the development of RPGN.