Advances in human antiglomerular basement membrane disease

Case report: renal recovery in Goodpasture's syndrome treated with rituximab

Successful induction of remission in anti-glomerular basement membrane (anti-GBM) glomerulonephritis can be obtained by using rituximab as a first-line immunosuppressive agent. We report the case of a 20-year-old male patient with Goodpasture's (anti-GBM) syndrome, with poor prognostic factors at presentation including intra-alveolar hemorrhage and dialysis-dependent rapidly progressive glomerulonephritis. The diagnosis was confirmed on kidney biopsy and serology (anti-GBM antibody titer). Rituximab was used as the first-line immunosuppressive agent in combination with pulse corticosteroids and plasmapheresis, to avoid potential side effects of cyclophosphamide. Anti-GBM antibody titers became undetectable after initiating rituximab. No adverse events were reported, and the patient became dialysis-independent after 6 months. This case reports the successful remission of a patient with Goodpasture's syndrome after induction with rituximab.

Epidemiology, clinical features, risk factors, and outcomes in anti-glomerular basement membrane disease: A systematic review and meta-analysis

Anti-glomerular basement membrane (GBM) disease is a small-vessel vasculitis that represents the most aggressive form of autoimmune glomerulonephritis. The study aimed to investigate the prevalence, clinical characteristics, risk factors, and outcomes of anti-GBM disease through a systematic review and meta-analysis involving 47 studies with 2830 patients. The overall incidence of anti-GBM disease ranged from 0.60 to 1.79 per million population per annum. In rapidly progressive glomerulonephritis and crescentic glomerulonephritis, the pooled incidence rates were 8.0% and 12.8%, respectively. The pooled prevalence rates of anti-GBM antibodies, antineutrophil cytoplasmic antibodies (ANCA), and lung hemorrhage were 88.8%, 27.4%, and 32.6%, respectively. Patients with combined ANCA positivity demonstrated a prognosis comparable to those patients with only anti-GBM antibodies, though with differing clinical features. The pooled one-year patient and kidney survival rates were 76.2% and 30.2%, respectively. Kidney function on diagnosis and normal glomeruli percentage were identified as strong prognostic factors. This study represents the first comprehensive meta-analysis on anti-GBM disease, providing insights into its management. However, caution is warranted in interpreting some results due to the observational nature of the included studies and high heterogeneity.

The protease inhibitor E64d might attenuate the development of experimental anti-glomerular basement membrane disease through regulating the activation of Th1 cells

BACKGROUND

Cathepsins have been recently identified as a regulator in the activation of Th1 and Th17 cells, which play an important role in the pathogenesis of anti-glomerular basement membrane (GBM) disease. Whether cathepsins contribute to the development of anti-GBM disease through regulating the activation of CD4+ T cell is still unclear.

METHODS

Rats with experimental anti-GBM disease was established by immunization with the nephritogenic T cell epitope α3127-148. E64d, a cysteine cathepsin inhibitor, was administered in vitro and vivo to evaluate the effect of cathepsins on regulating the activation of antigen specific T cells and the development of anti-GBM disease.

RESULTS

In rats with experimental anti-GBM diseases, E64d treatment not only reduced the levels of proteinuria, serum creatinine and anti-GBM antibody, but also ameliorated the kidney injury with less glomerular IgG deposition, a lower percentage of crescents and less infiltration of CD4+ T cells, CD8+ T cells and macrophages, as well as a lower percentage of splenic Th1 cells. In vitro, E64d treatment could significantly reduce the production of IFN-γ in the supernatant which might be produced by the activation of Th1 cells after being recalled with the autoantigen α3127-148. We also found the CD4+ T cells of rats with anti-GBM disease had an increased expression of cathepsin L (Cts-L), and the percentage of CD4+ T cells with extracellular expression of Cts-L was obviously higher, indicating it as a potential key regulator.

CONCLUSIONS

E64d might attenuate the development of anti-GBM disease by participating in the activation of Th1 cells, indicating it as a potential drug for anti-GBM disease in the future.

Evaluation of the Risk Prediction Models in Predicting Kidney Outcomes in Antiglomerular Basement Membrane Disease

INTRODUCTION

A previous study showed that the renal risk score (RRS) was transferrable to antiglomerular basement membrane (anti-GBM) disease and proposed a risk stratification according to the need of renal replacement therapy (RRT) and the percentage of normal glomeruli (N). Herein, we analyzed the risk factors associated with kidney outcomes in patients with biopsy-proven anti-GBM disease and evaluated these 2 prognosis systems.

METHODS

A total of 120 patients with biopsy-proven anti-GBM disease with complete clinicopathologic and outcome data were analyzed.

RESULTS

The median time to kidney biopsy was 41 days (interquartile range [IQR]: 22-63 days). RRT and N were the only independent predictors of end-stage kidney disease (ESKD). Patients with N ≥10% were more likely to achieve ESKD-free outcomes, even in the subcohort of patients who underwent posttreatment biopsies (P < 0.001). N and serum creatinine at presentation (cut-off values 750 μmol/l and 1300 μmol/l) were 2 independent factors for predicting kidney recovery. The RRS and the risk stratification tool exhibited predictive value for ESKD and could be transferred to patients with kidney biopsy following treatment (Harrell's C statistic [C] = 0.738 and C = 0.817, respectively). However, a cross-over of outcomes among groups was observed in the risk stratification tool in long-term follow-up, when patients with RRT and N ≥10% achieved better kidney outcomes than those without RRT but N <10%.

CONCLUSION

Normal glomeruli percentage, even posttreatment, was a strong indicator for kidney outcomes, especially on long-term prognosis. Serum creatinine is a predictor for kidney recovery, independent of biopsy findings. The risk stratification tool for kidney survival was transferrable to patients with anti-GBM disease with biopsy following treatment in our cohort; however, this needs further validations for long-term outcomes.

Short-chain fatty acids ameliorate experimental anti-glomerular basement membrane disease

BACKGROUND

Short-chain fatty acids (SCFAs), as the link between gut microbiota and the immune system, had been reported to be protective in many autoimmune diseases by the modulation of T cell differentiation. The pathogenic role of autoreactive Th1 and Th17 cells and the protective role of Treg cells in the pathogenesis of anti-GBM disease have been fully demonstrated. Thus, the present study aimed to investigate the therapeutic effects of SCFAs in a rat model of anti-GBM disease.

MATERIALS AND METHODS

Experimental anti-GBM disease was constructed by immunizing Wistar Kyoto rats with a nephrogenic T cell epitope α3127-148, and intervened by sodium acetate, sodium propionate, or sodium butyrate, 150 mM in the drinking water from day 0 to 42. Kidney injury was accessed by the biochemical analyzer, immunofluorescence, and immunohistochemistry. Antibody response was detected by ELISA. T cell clustering and proliferation were detected by flow cytometry. Human kidney 2 (HK2) cells were stimulated in vitro and cytokines were assessed by quantitative real-time PCR.

RESULTS

Treatment with sodium acetate, sodium propionate, or sodium butyrate ameliorated the severity of kidney impairment in rats with anti-GBM glomerulonephritis. In the sodium butyrate-treated rats, the urinary protein, serum creatinine, and blood urea nitrogen levels were significantly lower; the percentage of crescent formation in glomeruli was significantly reduced; and the kidneys showed reduced IgG deposition, complement activation, T cell, and macrophage infiltration as well as the level of circulating antibodies against anti-α3(IV)NC1. The treatment of sodium butyrate reduced the α3127-148-specific T cell activation and increased the Treg cells differentiation and the intestinal beneficial bacteria flora. It also alleviated the damage of HK2 cells treated with inflammatory factors and complement.

CONCLUSION

Treatment with SCFAs, especially butyrate, alleviated anti-GBM nephritis in rat model, indicating its potential therapeutic effects in clinical usage.

Autoantibodies against laminin-521 are pathogenic in anti-glomerular basement membrane disease

Anti-glomerular basement membrane (anti-GBM) disease is an organ-specific autoimmune disorder characterized by autoantibodies against GBM components. Evidence from human inherited kidney diseases and animal models suggests that the α, β, and γ chains of laminin-521 are all essential for maintaining the glomerular filtration barrier. We previously demonstrated that laminin-521 is a novel autoantigen within the GBM and that autoantibodies to laminin-521 are present in about one-third of patients. In the present study, we investigated the pathogenicity of autoantibodies against laminin-521 with clinical and animal studies. Herein, a rare case of anti-GBM disease was reported with circulating autoantibodies binding to laminin-521 but not to the NC1 domains of α1-α5(IV) collagen. Immunoblot identified circulating IgG from this patient bound laminin α5 and γ1 chains. A decrease in antibody levels was associated with improved clinical presentation after plasmapheresis and immunosuppressive treatments. Furthermore, immunization with laminin-521 in female Wistar-Kyoto rats induced crescentic glomerulonephritis with linear IgG deposits along the GBM, complement activation along with infiltration of T cells and macrophages. Lung hemorrhage occurred in 75.0% of the rats and was identified by the presence of erythrocyte infiltrates and hemosiderin-laden macrophages in the lung tissue. Sera and kidney-eluted antibodies from rats immunized with laminin-521 demonstrated specific IgG binding to laminin-521 but not to human α3(IV)NC1, while the opposite was observed in human α3(IV)NC1-immunized rats. Thus, our patient data and animal studies imply a possible independent pathogenic role of autoantibodies against laminin-521 in the development of anti-GBM disease.

Immunity in the balance: Fatal disseminated adenovirus infection in a patient undergoing plasma exchange and immunosuppressive chemotherapy for anti-glomerular basement membrane disease

Anti-glomerular basement membrane (anti-GBM) disease (formerly known as Goodpasture's syndrome) is a rare autoinflammatory condition that affects the renal and/or pulmonary capillaries. The standard therapeutic regimen for anti-GBM disease involves therapeutic plasma exchange (TPE), cyclophosphamide, and corticosteroids to rapidly remove and inhibit autoantibody production and reduce organ inflammation. Herein we report an 82-year-old female who developed anti-GBM disease but expired despite therapy, secondary to multi-organ failure in the setting of disseminated adenovirus disease. We discuss the utility and potential adverse effect of daily TPE for a protracted course (ie, 10-14 days), the recommended TPE intensity in the 2023 American Society for Apheresis guidelines, updated from every-other-day TPE in the 2019 guidelines, despite no new data. We also highlight the potential for unusual infections to occur in these patients due to the profound immunosuppression, and discuss the importance of balancing immunosuppression to treat the disease with close surveillance of any potential opportunistic infections.

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.

Rituximab for the treatment of refractory anti-glomerular basement membrane disease

BACKGROUND

Anti-glomerular basement membrane (anti-GBM) disease is a rare but severe autoantibody-mediated immune disorder. The typical clinical presentation includes rapidly progressive glomerulonephritis and often concurrent pulmonary hemorrhage. The present study is aimed to investigate the therapeutic effects of rituximab either used alone or with other immunosuppressants.

METHODS

Eight patients diagnosed with anti-GBM disease and treated with rituximab from 2014 to 2020 were retrospectively reviewed.

RESULTS

Eight patients included 5 males and 3 females with a median age of 58.5 years. They all presented severe kidney injuries and 1 patient had lung hemorrhage. At diagnosis, the median of serum creatinine was 246 µmol/L (ranging from 91 to 850 µmol/L), with 3 patients requiring dialysis. All of them received corticosteroids and plasmapheresis. Rituximab was given as either standard four weekly doses or one pulse ranging from 100 to 600 mg. After a median follow-up of 34.5 months, kidney function was partially recovered or stabilized in 5/8 (62.5%) patients, free of dialysis. Anti-GBM antibodies remained undetected in all patients during follow-up. No severe adverse effect associated with rituximab was observed.

CONCLUSION

Rituximab may be an alternative therapy in the treatment of patient with severe or refractory anti-GBM disease.

Anti-glomerular basement membrane disease with IgA nephropathy: A case report

BACKGROUND

Anti-glomerular basement membrane (GBM) disease is a rare autoimmune disease manifesting as acute progressive nephritis syndrome with or without varying degrees of pulmonary hemorrhage. Anti-GBM disease coexisting with Immunoglobulin A (IgA) nephropathy is rarer and has different clinical manifestations and prognoses than simple anti-GBM disease. We describe a case of coexistence of these two diseases.

CASE SUMMARY

A 49-year-old man with hematuria and proteinuria accompanied by a slight elevation of serum creatinine was admitted to our hospital. The pathological results of renal biopsy and the elevated serum anti-GBM antibody titer supported a diagnosis of anti-GBM disease combined with IgA nephropathy. After treatment with corticosteroids and cyclophosphamide, the patient's serum creatinine was relatively stable, and the hematuria and proteinuria moderately improved in the subsequent six months.

CONCLUSION

Anti-GBM disease coexisting with IgA nephropathy is rare. The clinical manifestations and prognosis are better than those of simple anti-GBM disease. In this case, the patient's condition was improved and his renal function remained relatively stable with corticosteroid and cyclophosphamide treatment. New detection methods to identify whether the crescents in this case were derived from anti-GBM disease or IgA nephropathy are worthy of further exploration.

The Th17 Pathway in Vascular Inflammation: Culprit or Consort?

The involvement of IL-17A in autoimmune and inflammatory diseases has prompted the development of therapeutic strategies to block the Th17 pathway. Promising results came from their use in psoriasis and in ankylosing spondylitis. IL-17A acts on various cell types and has both local and systemic effects. Considering the premature mortality observed during chronic inflammatory diseases, IL-17A action on vascular cells was studied. Both in vitro and in vivo results suggest that this cytokine favors inflammation, coagulation and thrombosis and promotes the occurrence of cardiovascular events. These observations led to study the role of IL-17A in diseases characterized by vascular inflammation, namely allograft rejection and vasculitis. Increased circulating levels of IL-17A and histological staining reveal that the Th17 pathway is involved in the pathogenesis of these diseases. Vasculitis treatment faces challenges while the use of steroids has many side effects. Regarding results obtained in giant cell arteritis with IL-6 inhibitors, a cytokine involved in Th17 differentiation, the use of anti-IL-17 is a promising strategy. However, lessons from rheumatoid arthritis and multiple sclerosis must be learnt before targeting IL-17 in vasculitis, which may be culprit, consort or both of them.

Pathogenetic mechanisms, clinical signs and consequences of the autoimmune thyroiditis impact on body systems (a literature review)

Background. The review analyzes the publications on the pathogenetic mechanisms and clinical consequences of the impact of autoimmune thyroiditis and hypothyroidism on body systems. Autoimmune thyroiditis is an organ-specific autoimmune disease of the thyroid gland and the most common cause of hypothyroidism in regions of the world with sufficient iodine. Sources of information. The sources of information were reports in domestic and, mostly, foreign periodicals on immunology, pathological physiology, internal medicine, and endocrinology. Synthesis of evidence. The effect of autoimmune thyroiditis on the systems of the body is implemented in two ways. The first one is accomplished through the body’s immune system, when the organ-specific immune process in the thyroid gland for unknown reasons acquires signs of systemic disease with clinical manifestations of damage to other organs and systems. The second is due to hypothyroidism, which is the logical conclusion of the autoimmune process in the thyroid. The effects of hypothyroidism on the body as a whole and its systems, in particular, are known, and the pathogenetic mechanisms are not fully understood and require in-depth study. The issues of the body's autoimmune disease, the mechanisms of its initiation and progression remain undiscovered and poorly understood. Conclusions. The effect of autoimmune thyroiditis is realized through the immune system when the organ-specific immune process in the thyroid gland for unknown reasons acquires signs of systemic disease and hypothyroidism, which is the logical conclusion of the autoimmune process in the thyroid gland. The pathogenetic mechanisms of the effects of autoimmune thyroiditis and hypothyroidism on the body are not fully understood and require in-depth study. The presented data show that over the last decade the interest in studying the problem of autoimmune thyroiditis, hypothyroidism, and their pathological significance for the body has deepened.

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.

Glomerulonephritis in AKI: From Pathogenesis to Therapeutic Intervention

Acute kidney injury (AKI) is increasingly emerging as a global emergency. Sepsis, major surgery, and nephrotoxic drugs are the main causes of AKI in hospitalized patients. However, glomerulonephritis accounts for about 10% of AKI episodes in adults, mainly related to rapidly progressive glomerulonephritis resulting from granulomatous polyangiitis (GPA, Wegener granulomatosis), microscopic polyangiitis (MPA), and anti-glomerular basement membrane (GBM) disease. Also, diffuse proliferative lupus nephritis, immunoglobulin A nephropathy, post-streptococcal glomerulonephritis, mixed cryoglobulinemia, mesangiocapillary glomerulonephritis, membranous nephropathy, hemolytic uremic syndrome, thrombotic thrombocytopenic purpura, and scleroderma can induce acute renal failure. Early diagnosis of AKI due to glomerulonephritis is crucial for prompt, effective management to improve short- and long-term outcomes. Kidney biopsy is the gold standard for the diagnosis of glomerular disease, but it is not frequently performed in critically ill patients because of their clinical conditions. In this setting, a growing number of diagnostic assays can support the working hypothesis, including antineutrophil cytoplasmic antibodies (ANCAs), anti-double-stranded DNA antibodies, anti-GBM antibodies, antistreptolysin O and anti-DNase B antibodies, cryoglobulins, antiphospholipid antibodies, and complement levels. Therapeutic strategies in AKI patients with glomerulonephritis include high-dose corticosteroids, cyclophosphamide, and plasma exchange. This article reviews the wide spectrum of glomerulopathies associated with AKI, describing the immunological mechanisms underlying glomerular diseases and presenting an overview of the therapeutic options.

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.

Clinical-Pathological Features and Outcome of Atypical Anti-glomerular Basement Membrane Disease in a Large Single Cohort

Background: Atypical cases of anti-glomerular basement membrane (GBM) disease had absent circulating antibodies but linear IgG deposits along GBM in the kidneys. Herein, we reported the clinical-pathological features and outcome of these rare cases.

Methods: Linear IgG deposit along GBM were examined by immunofluorescence on renal specimens, with exclusion of diabetic kidney disease. Circulating anti-GBM antibodies were tested by commercial ELISA assay. Clinical, pathological and follow-up data were retrospectively analyzed.

Results: From 2013 to 2018, a total of 60 patients were diagnosed as atypical anti-GBM disease. They had a male predominance, with an average age of 51.7 ± 15.6 years. Three (5.0%) patients had alveolar hemorrhage. Forty five percent of them presented with acute kidney disease. All patients had linear IgG deposit along GBM, some in addition on tubular basement membrane and/or Bowmans' capsules. C3 deposition was found in 65.0% of the patients. 41.7% (25/60) of the patients showed crescent formation and the percentage of crescent was (34.7 ± 23.5)% in those patients. They had higher prevalence of hematuria and C3 deposit, higher levels of serum creatinine, worse renal and patient survival than those without crescent (P < 0.05). During the follow-up of 35.7 ± 21.4 months, 14 (23.3%) patients progressed to ESRD. The serum creatinine on diagnosis [per 200 μmol/L increase, HR (95% CI): 2.663 (1.372, 5.172), P = 0.004], serum C3 [per 0.1 g/L increase, HR (95% CI): 0.689(0.483, 0.984), P = 0.040] and the intensity of kidney C3 staining [per 1+ increase, HR (95% CI): 2.770 (1.115, 6.877), P = 0.028] were independent predictive factors for kidney outcome. Nine (15.0%) patients died of all causes.

Conclusions: Atypical anti-GBM disease manifested milder kidney injury and scarce pulmonary hemorrhage compared to the classical cases. Though heterogeneous, a substantial number of the patients had complement activation and crescent formation. Patients having crescents presented with more severe clinical course and worse outcomes. The poor kidney and patient prognosis emphasize prompt interventions from physicians. The immunosuppressive intervention was not associated with kidney or patient outcome. Further studies are needed to address the optimal therapeutic regimen.

Management of End-stage Renal Disease Associated with Systemic Rheumatic Diseases

The outcomes of rheumatic diseases (RDs) have improved over the past decades. However, a significant proportion of the patients still suffer from end-stage renal disease (ESRD) and have to bear the burden of hemodialysis. It is crucial to prevent patients with RDs from developing ESRD from viewpoints of medicine and medical economics. For those who already have ESRD, it is important to improve vial prognosis and quality of life through appropriate management of disease activity and comorbidities related to ESRD. Thus, rheumatologists and nephrologists need to recognize risk factors associated with progression to ESRD along with their appropriate management. Although the activity of most RDs tends to decrease after initiation of hemodialysis, disease activity may still increase, and recognizing how to appropriately use immunosuppressive agents even after the development of ESRD is crucial. The treatment of RDs needs extra attention as hydroxychloroquine requires more frequent monitoring for adverse drug reactions; therapeutic drug monitoring is necessary for mycophenolate mofetil, cyclosporine A, and tacrolimus; cyclophosphamide and azathioprine need dose adjustments; methotrexate and bucillamine are contraindicated in patients with ESRD; leflunomide and sulfasalazine do not require significant dose reduction and iguratimod should be carefully administered. The pharmacokinetics of biological agents such as rituximab or belimumab are not affected by ESRD, and dose adjustments are not necessary. Collaboration between rheumatologists and nephrologists is needed more than ever and is expected to produce a complementary effect and achieve better outcomes in clinical settings, although this cooperation has not always been conducted appropriately.

B Cell-Mediated Autoimmune Diseases

Extensive studies have suggested a central role of B cells in the autoimmune pathogenesis, as loss of B cell tolerance results in increased serum levels of autoantibodies, enhanced effector T cell response and tissue damages. Here, we provide an overview of dysregulated B cell responses in the development of autoimmunity. In addition to their presence in the target organs, autoreactive B cells can promote the formation of ectopic lymphoid structures and differentiate into plasma cells that produce large amounts of autoantibodies and cytokines. In animal models that recapitulate the key features of human autoimmune disease, mechanistic studies have indicated two categories of autoantibodies: (1) serological markers for disease diagnosis and prognosis; (2) effector molecules that induce organ hypofunction or damage directly in an epitope-specific manner, or indirectly by activating other immune cell subsets. Moreover, B cell-derived cytokines usually promote the autoreactive T cell response during autoimmune development, but there is compelling evidence that a subpopulation of B cells negatively regulates immune responses, also known as regulatory B cells via secreting anti-inflammatory cytokines (IL-10, IL-35, etc.) or a contact-dependent fashion. Although B cell depletion could eliminate most circulating B cells in the periphery, the clinical outcomes of B cell depletion therapy for autoimmune diseases vary among individuals due to differential activation or survival signals for B cells provided by tissue microenvironment. Thus, therapeutic combinations that target immune checkpoints and B cell activation may represent a promising strategy for the effective treatment of human autoimmune diseases.

Anti-glomerular basement membrane nephritis with bronchial carcinoma: a case report

Renal insufficiency is common among patients with various types of malignant tumors. However, the occurrence of anti-glomerular basement membrane (GBM) nephritis in a patient with a malignant tumor is relatively rare. Here, we describe a patient with bronchial carcinoma who exhibited acute kidney injury, hematuria, and non-nephrotic-range proteinuria. The patient had positive serum anti-GBM antibody findings and biopsy-proven anti-GBM nephritis. This is a rare instance of anti-GBM nephritis in a patient with a malignant solid tumor. Neoplasia was presumed to contribute to the development of anti-GBM nephritis through secretion of tumor-related antigens or unusual exposure to GBM.

A Modified Peptide Derived from Goodpasture Autoantigen Arrested and Attenuated Kidney Injuries in a Rat Model of Anti-GBM Glomerulonephritis

BACKGROUND

In Goodpasture disease, the noncollagenous domain 1 of the α3 chain (α3NC1) of type IV collagen is the main target antigen of antibodies against glomerular basement membrane (GBM). We previously identified a nephritogenic epitope, P14 (α3_127-148), that could induce crescentic nephritis in WKY rats, and defined its core motif. Designing a modified peptide, replacing critical pathogenic residues with nonpathogenic ones (on the basis of homologous regions in α1NC1 chain of type IV collagen, known to be nonpathogenic), might provide a therapeutic option for anti-GBM GN.

METHODS

We synthesized a modified peptide, replacing a single amino acid, and injected it into α3-P14-immunized rats from day 0 (the early-treatment group) or a later-treatment group (from days 17 to 21). A scrambled peptide administrated with the same protocol served as a control.

RESULTS

The modified peptide, but not the scrambled peptide, attenuated anti-GBM GN in both treatment groups, and halted further crescent formation even after disease onset. Kidneys from the modified peptide-treated rats exhibited reductions in IgG deposits, complement activation, and infiltration by T cells and macrophages. Treatment also resulted in an anti-inflammatory cytokine profile versus a proinflammatory profile for animals not receiving the modified peptide; it also reduced α3-P14-specific T cell activation, modulated T cell differentiation by decreasing Th17 cells and enhancing the ratio of Treg/Th17 cells, and inhibited binding of α3-P14 to antibodies and MHC II molecules.

CONCLUSIONS

A modified peptide involving alteration of a critical motif in a nephritogenic T cell epitope alleviated anti-GBM GN in a rat model. Our findings may provide insights into an immunotherapeutic approach for autoimmune kidney disorders such as Goodpasture disease.

Difficulties in Goodpasture's syndrome diagnosing

The article analyzes the diagnosis and treatment of anti-GBM antibody disease (Goodpasture's syndrome) - a rare, severe progressive disease, associated with anti-glomerular basement membrane antibody-induced pulmonary hemorrhage and glomerulonephritis. The main problem of this pathology is late diagnosis, resulted in ineffective treatment. The article provides current information on the epidemiology, etiology and pathogenesis, diagnosis, and treatment of Goodpasture's syndrome, as well as clinical case of a patient with this rare disease.

Fever and prodromal infections in anti-glomerular basement membrane disease

AIM

Anti-glomerular basement membrane (GBM) disease is an autoimmune disorder with rapidly progressive glomerulonephritis and alveolar haemorrhage. Fever symptoms and prodromal infections have been reported in many cases, but still not been elucidated.

METHODS

Our study enrolled 140 consecutive patients with anti-GBM disease and retrospectively analyzed the characteristics of fever symptoms and the possible reasons.

RESULTS

Among the 140 patients, 94 (67.1%) patients presented with fever (over 37.5°C) prior to admission or within 48 h of hospitalization. Among those with fever, 74 (78.7%) patients had infections, 15 (16.0%) patients had positive serum anti-neutrophil cytoplasmic antibodies, all towards myeloperoxidase, which was comparable to the patients without fever (17.4%, P = 0.830). There were 93/140 patients suffered from infections, with 47.3% in lungs and 31.2% on upper respiratory tract. In some cases, we identified the microbes of infections, including Candida albicans, Escherichia coli, Acinetobacter baumannii, Enterococcus faecalis, Klebsiella pneumoniae, Hemolytic staphylococci, Pseudomonas aeruginosa and Citrobacter braakii. Patients with fever had higher levels of serum anti-GBM antibodies (154.9 ± 58.4 vs. 106.0 ± 63.2 IU/mL, P < 0.001), higher serum creatinine (733.4 ± 402.5 vs. 580.6 ± 368.1 μmol/L, P = 0.032), higher percentage of crescents (87.0 ± 15.6 vs. 67.4 ± 37.6%, P = 0.021), and higher frequency of progression to end stage renal disease (ESRD) (80.9% vs. 60.9%, P = 0.011).

CONCLUSION

We concluded that fever is a common symptom in anti-GBM disease and associates with more severe glomerulonephritis. The majority of patients at presentation had fever with respiratory tract infections, which needs further investigation to reveal their role in the pathogenesis of anti-GBM disease.

Use of rituximab as an induction therapy in anti-glomerular basement-membrane disease

BACKGROUND

Anti-glomerular basement-membrane (anti-GBM) disease (or Goodpasture disease) is characterized by severe kidney and lung involvement. Prognoses have improved with treatments that combine plasma exchange and immunosuppressive drugs. However, patients with severe renal involvement can have poor renal outcomes and cyclophosphamide can cause significant complications. Anti-GBM antibodies have a direct pathogenic effect on the disease: thus, therapeutics that can decrease their production, such as rituximab, could be a good alternative.

METHODS

The medical files of five patients that had received rituximab as a first-line therapy (instead of cyclophosphamide), plus plasma exchange and steroids, were reviewed. All patients had severe disease manifestations.

RESULTS

Four patients required dialysis at diagnosis and remained dialysis-dependent over the mean follow-up of 15 months. Three patients had pulmonary involvement, but recovered even though mechanical ventilation was required. Anti-GBM antibodies became rapidly undetectable in all patients. One infectious and two hematological complications were observed.

CONCLUSIONS

We report the outcomes of five patients with Goodpasture disease and treated with rituximab as a first-line treatment. This strategy was effective at treating pulmonary manifestations and was associated with a good biological response with no major serious adverse events. However, renal outcomes were not significantly improved.

The Clinical and Immunologic Features of Patients With Combined Anti-GBM Disease and Castleman Disease

Patients with both anti-glomerular basement membrane (anti-GBM) disease and Castleman disease have been rarely reported. In this study, we report 3 patients with this combination. They had immunologic features similar to patients with classic anti-GBM disease. Sera from the 3 patients recognized the noncollagenous (NC) domain of the α3 chain of type IV collagen (α3(IV)NC1) and its 2 major epitopes, EA and EB. All 4 immunogloblin G (IgG) subclasses against α3(IV)NC1 were detectable, with predominance of IgG1. In one patient with lymph node biopsy specimens available, sporadic plasma cells producing α3(IV)NC1-IgG were found, suggesting a causal relationship between the 2 diseases. One patient, who achieved remission with antibody clearance and normalization of serum creatinine and interleukin 6 concentrations after plasma exchange and 3 cycles of chemotherapy, experienced recurrence of anti-GBM antibodies and an increase in interleukin 6 concentration after chemotherapy discontinuation because of adverse effects, but both returned to normal after another cycle of chemotherapy. This clinical course and the pathologic findings support the hypothesis that the Castleman disease-associated tumor cells are the source of the anti-GBM autoantibodies.

18F-FDG PET/CT Imaging of Necrotizing Crescentic Glomerulonephritis With Anti-Glomerular Basement Membrane Disease

A 30-year-old woman presented with lethargy, night sweats, and fever with raised inflammatory markers. Anti-neutrophil cytoplasmic antibody was negative. Abdominopelvic CT was unremarkable. Subsequently, she underwent FDG PET/CT showing globally enlarged kidneys with diffuse hypermetabolic activity within the renal parenchyma bilaterally. Renal biopsies showed morphologic features of an active necrotizing crescentic glomerulonephritis, which was confirmed clinically and treated. This case demonstrates the role that FDG PET/CT can play in inflammatory conditions, such as glomerulonephritis, where it may be clinically useful when the presentation is atypical.

Autoimmune Thyroiditis and Glomerulopathies

Autoimmune thyroiditis (AIT) is generally associated with hypothyroidism. It affects ~2% of the female population and 0.2% of the male population. The evidence of thyroid function- and thyroid autoantibody-unrelated microproteinuria in almost half of patients with AIT and sometimes heavy proteinuria as in the nephrotic syndrome point to a link of AIT with renal disease. The most common renal diseases observed in AIT are membranous nephropathy, membranoproliferative glomerulonephritis, minimal change disease, IgA nephropathy, focal segmental glomerulosclerosis, antineutrophil cytoplasmic autoantibody (ANCA) vasculitis, and amyloidosis. Different hypotheses have been put forward regarding the relationship between AIT and glomerulopathies, and several potential mechanisms for this association have been considered. Glomerular deposition of immunocomplexes of thyroglobulin and autoantibodies as well as the impaired immune tolerance for megalin (a thyrotropin-regulated glycoprotein expressed on thyroid cells) are the most probable mechanisms. Cross-reactivity between antigens in the setting of genetic predisposition has been considered as a potential mechanism that links the described association between ANCA vasculitis and AIT.

The critical amino acids of a nephritogenic epitope on human Goodpasture autoantigen for binding to HLA-DRB1*1501

BACKGROUND

Anti-GBM disease is caused by autoimmunity to Goodpasture antigen on α3(IV)NC1 and had strong associations with HLA-DRB1*1501. Previous studies identified α3_127-148 (P14: TDIPPCPHGWISLWKGFSFIMF) as a T cell epitope. The present study was aimed to investigate the binding capacity of P14 to HLA-DRB1*1501 and the critical amino acids for this binding.

METHODS

A line of EBV-transformed human B cells homozygous for HLA-DRB1*1501 was used to detect the binding capacity of peptides to HLA-DRB1*1501 using flow cytometry analysis. P14 was sequentially truncated into 8 peptides with 15 amino acids to identify the core binding motif. A set of alanine substituted peptides of P14-2 was then synthesized to identify its critical residues for binding to HLA-DRB1*1501. The structure of HLA-DR2b-Peptide-TCR complex was constructed by modeling to analyze the interaction of each amino acids of P14-2 with the HLA-DR2b molecule.

RESULTS

P14 could bind to HLA-DRB1*1501 expressed on B cell surface. The N-terminus of P14 was the core binding motif and the truncated peptide P14-2 (DIPPCPHGWISLWKG) _128-142 had the strongest binding capacity. After sequential amino acid substitution, we found the binding capacity of P14-2 was completely lost by the substitution of cysteine (C) ₁₃₂ and significantly decreased by the substitution of tryptophan (W) ₁₃₆, lysine (K) ₁₄₁, or glycine (G) ₁₄₂, but still at a high level. The modeling showed that (C) ₁₃₂ had a strong interaction with pocket 4 on the β chain of DR2b. Thus, C₁₃₂, W ₁₃₆, K₁₄₁, and G₁₄₂ were defined as the critical amino acid residues for the binding capacity of P14 to HLA-DRB1*1501.

CONCLUSION

We identified α3_128-142 (DIPPCPHGWISLWKG) as the core binding motif of P14 to HLA-DRB1*1501 molecule. And the critical amino acid residues for this binding were further defined as C₁₃₂, W ₁₃₆, K ₁₄₁, and G ₁₄₂.

T cells and autoimmune kidney disease

Glomerulonephritis is traditionally considered to result from the invasion of the kidney by autoantibodies and immune complexes from the circulation or following their formation in situ, and by cells of the innate and the adaptive immune system. The inflammatory response leads to the proliferation and dysfunction of cells of the glomerulus, and invasion of the interstitial space with immune cells, resulting in tubular cell malfunction and fibrosis. T cells are critical drivers of autoimmunity and related organ damage, by supporting B-cell differentiation and antibody production or by directly promoting inflammation and cytotoxicity against kidney resident cells. T cells might become activated by autoantigens in the periphery and become polarized to secrete inflammatory cytokines before entering the kidney where they have the opportunity to expand owing to the presence of costimulatory molecules and activating cytokines. Alternatively, naive T cells could enter the kidney where they become activated after encountering autoantigen and expand locally. As not all individuals with a peripheral autoimmune response to kidney antigens develop glomerulonephritis, the contribution of local kidney factors expressed or produced by kidney cells is probably of crucial importance. Improved understanding of the biochemistry and molecular biology of T cells in patients with glomerulonephritis offers unique opportunities for the recognition of treatment targets for autoimmune kidney disease.

Deglycosylation of myeloperoxidase uncovers its novel antigenicity

Myeloperoxidase (MPO) is a common target antigen of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis and is recognized in one-third of patients with anti-glomerular basement membrane (GBM) disease. Our previous study identified over 60% of patients with anti-GBM disease recognizing linear peptides of MPO heavy chain. Here we tested whether aberrant glycosylation alters MPO antigenicity through exposure of neo-epitopes on MPO molecules. Atypical glycosylated MPO molecules, including all possible glycosylation types, were prepared by exoglycosidase and endoglycosidase treatments. Antibodies were detected from the sera of 40 patients with anti-GBM disease without the coexistence of MPO-ANCA. Circulating antibodies against aberrant glycosylated MPO existed in 21 of these patients. Non-glycan MPO and MPO with only N-acetylglucosamine had high frequencies of recognition (16 and 15 patients, respectively). Antibodies binding to aberrant glycosylated MPO could not be inhibited by intact MPO or GBM antigen. When applied to ethanol-fixed neutrophils from normal individuals, these antibodies yielded a typical cytoplasmic staining pattern (c-ANCA). Antigen specificity was detected in 90% of the antibodies using five peptides containing one of the five N-glycosylation sites each, mostly on N323, N355, and N391. The antibodies were restricted to IgG1 subclass, could activate complement, and induce neutrophil degranulation in vitro. Thus, aberrant glycosylated MPO exposed neo-epitopes and was recognized by half of the patients with anti-GBM disease. Their antibodies possessed pathogenic characteristics and may be associated with kidney injury.

Simultaneous comprehensive multiplex autoantibody analysis for rapidly progressive glomerulonephritis

Rapidly progressive glomerulonephritis (RPGN) is mainly caused by anti-glomerular basement membrane (GBM) antibody-mediated glomerulonephritis, immune-complex or anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides and leads to rapid loss of renal function. Detection of ANCA and autoantibodies (autoAbs) to GBM and dsDNA enables early diagnosis and appropriate treatment of RPGN aiding in preventing end-stage renal disease.Determination of ANCA on neutrophils (ANCA) as well as autoAbs to myeloperoxidase (MPO-ANCA), proteinase 3 (PR3-ANCA), GBM, and dsDNA was performed by the novel multiplex CytoBead technology combining cell- and microbead-based autoAb analyses by automated indirect immunofluorescence (IIF). Forty patients with granulomatosis with polyangiitis (GPA), 48 with microscopic polyangiitis (MPA), 2 with eosinophilic GPA, 42 with systemic lupus erythematosus (SLE), 43 with Goodpasture syndrome (GPS), 57 with infectious diseases (INF), and 55 healthy subjects (HS) were analyzed and findings compared with classical single testing.The CytoBead assay revealed for GPA, MPA, GPS, and SLE the following diagnostic sensitivities and for HS and INF the corresponding specificities: PR3-ANCA, 85.0% and 100.0%; MPO-ANCA, 77.1% and 99.1%; anti-GBM autoAb, 88.4% and 96.4%; anti-dsDNA autoAb, 83.3% and 97.3%; ANCA, 91.1% and 99.1%, respectively. Agreement with classical enzyme-linked immunosorbent assay and IIF was very good for anti-GBM autoAb, MPO-ANCA, PR3-ANCA, and ANCA, respectively. Anti-dsDNA autoAb comparative analysis demonstrated fair agreement only and a significant difference (P = 0.0001).The CytoBead technology provides a unique multiplex reaction environment for simultaneous RPGN-specific autoAb testing. CytoBead RPGN assay is a promising alternative to time-consuming single parameter analysis and, thus, is well suited for emergency situations.

Fcγ Receptors in Solid Organ Transplantation

In the current era, one of the major factors limiting graft survival is chronic antibody-mediated rejection (ABMR), whilst patient survival is impacted by the effects of immunosuppression on susceptibility to infection, malignancy and atherosclerosis. IgG antibodies play a role in all of these processes, and many of their cellular effects are mediated by Fc gamma receptors (FcγRs). These surface receptors are expressed by most immune cells, including B cells, natural killer cells, dendritic cells and macrophages. Genetic variation in FCGR genes is likely to affect susceptibility to ABMR and to modulate the physiological functions of IgG. In this review, we discuss the potential role played by FcγRs in determining outcomes in solid organ transplantation, and how genetic polymorphisms in these receptors may contribute to variations in transplant outcome.

Frequently relapsing anti-glomerular basement membrane antibody disease with changing clinical phenotype and antibody characteristics over time

Anti-glomerular basement membrane (GBM) antibody disease is a typically monophasic autoimmune disease with severe pulmonary and renal involvement. We report an atypical case of frequently relapsing anti-GBM antibody disease with both anti-GBM antibody-positive flares with pulmonary and renal involvement, and anti-GBM antibody-negative flares that were pulmonary limited with no histologic renal disease. This is the first report of alternating disease phenotype and anti-GBM antibody status over time. Disease severity paralleled the detection of anti-GBM antibodies but was independent of IgG subtype staining along the GBM. This case suggests a role for changing subpopulations of pathogenic antibodies as an explanation for variation in disease phenotype and anti-GBM antibody results.

Novel therapy for anti-glomerular basement membrane disease with IgA nephropathy: A case report

Anti-glomerular basement membrane (GBM) disease is characterized by circulating anti-GBM antibodies and deposition of these antibodies in the renal GBM. Renal involvement in anti-GBM is more severe when compared with other types of immune-mediated glomerulonephritis, and the majority of patients manifest progressive renal failure, leading to end-stage renal disease. In a limited number of cases, anti-GBM disease has been shown to be accompanied with other immune-mediated glomerulonephritis. The present study reported the case of a 50-year-old female patient presenting with rapidly progressive glomerulonephritis, who was diagnosed with anti-GBM disease with IgA nephropathy. The patient achieved a relatively good therapeutic outcome with administration of corticosteroids plus mycophenolate mofetil (MMF), which may prove to be a novel treatment option for this rare disease; however, the exact underlying mechanism requires further in-depth investigation.

Antibodies to Type IV Collagen Induce Type 1 Autoimmune Pancreatitis

Type 1 autoimmune pancreatitis (AIP) is prototypic autoantibody-mediated diseases. Sclerosis accompanied by fiber deposition is generally regarded as the primary lesion in the development of obliterative vasculitis. However, why collagens or their antibodies play a crucial role in the pathogenesis of AIP has not been demonstrated. This study was performed to investigate if anti-collagen type IV antibodies (ACIVAbs) are the key factor of fiber deposition and recruit leukocytes, resulting in obliterative vasculitis in pancreas. Enzyme-linked immunosorbent analyses (ELISA) were used to measure the expression of Col IV and ACIVAbs in serum of patients with and without AIP. In vitro, adhesion and proliferation were determined by human lymphocytes incubated with Col IV and ACIVAbs. In vivo, C57BL0/6 mice were immunized with IgG-ACIVAbs, followed by analysis of clinical phenotype. IgG-ACIVAbs were recognized by the serum specimens from 12 of 22 patients with type 1 AIP, 3 of 9 patients with Crohn's disease, and 2 of 18 patients with pancreatic cancer, but not in healthy controls and acute pancreatitis. In patient's biopsy, ACIVAb staining increased and co-localized with subepithelial IgG4 deposits along the capillary walls and surrounding nerve fibers. In vitro, recombinant IgG-ACIVAbs increased leukocyte adhesion and proliferation. What is more, AIP could be induced in mice by immunization with IgG-ACIVAbs into adult mice.

Atypical anti-glomerular basement membrane disease

Background

Anti-glomerular basement membrane (anti-GBM) disease classically presents with aggressive necrotizing and crescentic glomerulonephritis, often with pulmonary hemorrhage. The pathologic hallmark is linear staining of GBMs for deposited immunoglobulin G (IgG), usually accompanied by serum autoantibodies to the collagen IV alpha-3 constituents of GBMs.

Methods

Renal pathology files were searched for cases with linear anti-GBM to identify cases with atypical or indolent course. Histopathology, laboratory studies, treatment and outcome of those cases was reviewed in detail.

Results

Five anti-GBM cases with atypical clinicopathologic features were identified (accounting for ∼8% of anti-GBM cases in our laboratory). Kidney biopsies showed minimal glomerular changes by light microscopy; one patient had monoclonal IgG deposits in an allograft (likely recurrent). Three patients did not have detectable serum anti-GBM by conventional assays. Three patients had indolent clinical courses after immunosuppressive treatment. One patient, untreated after presenting with brief mild hematuria, re-presented after a short interval with necrotizing and crescentic glomerulonephritis.

Conclusions

Thorough clinicopathologic characterization and close follow-up of patients with findings of atypical anti-GBM on renal biopsy are needed. Review of the literature reveals only rare well-documented atypical anti-GBM cases to date, only one of which progressed to end-stage kidney disease.

Review series: The cell biology of renal filtration

The function of the kidney, filtering blood and concentrating metabolic waste into urine, takes place in an intricate and functionally elegant structure called the renal glomerulus. Normal glomerular function retains circulating cells and valuable macromolecular components of plasma in blood, resulting in urine with just trace amounts of proteins. Endothelial cells of glomerular capillaries, the podocytes wrapped around them, and the fused extracellular matrix these cells form altogether comprise the glomerular filtration barrier, a dynamic and highly selective filter that sieves on the basis of molecular size and electrical charge. Current understanding of the structural organization and the cellular and molecular basis of renal filtration draws from studies of human glomerular diseases and animal models of glomerular dysfunction.

Coexistence of Anti-Glomerular Basement Membrane Antibodies and Anti-Neutrophil Cytoplasmic Antibodies in a Child With Human Leukocyte Antigen Susceptibility and Detailed Antibody Description: A Case Report

Anti-glomerular basement membrane (anti-GBM) disease and anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis both could cause rapidly progressive glomerulonephritis. The coexistence of ANCAs and anti-GBM antibodies was known as "double positive," which was extremely rare in children. We report a pediatric case with coexistence of ANCAs and anti-GBM antibodies. A 6-year-old girl presented with acute renal failure, hematuria, proteinuria, and oliguria. She was double positive of ANCAs specific to myeloperoxidase, and anti-GBM antibodies. Kidney biopsy confirmed linear immunoglobulin (Ig)G deposit along GBM and 100% of crescent formation in glomeruli; among them 83.3% were cellular crescents. Human leukocyte antigen (HLA) gene typing showed DRB1*1501, an allele strongly associated with anti-GBM disease, and DRB1*0405, an independent risk factor for renal failure in patients with ANCA-associated vasculitis. The titer of anti-GBM antibodies was 1:800, and the predominant IgG subclass was IgG1, which was closely related with severe kidney injury and worse outcome. The target antigen of anti-GBM antibodies was restricted on the noncollagen domain 1 of the α3 chain of type IV collagen (α3[IV]NC1), with recognitions to both epitopes, EA (α317-31) and EB (α3127-141). This is the first reported pediatric case with coexistence of ANCAs and anti-GBM antibodies, in which the HLA typing and immunologic characters of autoantibodies were identified. The findings on this early-onset patient are meaningful for understanding the mechanisms of both anti-GBM disease and ANCA-associated vasculitis.

Autoantigen complementarity and its contributions to hallmarks of autoimmune disease

The question considered is, "What causes the autoimmune response to begin and what causes it to worsen into autoimmune disease?" The theory of autoantigen complementarity posits that the initiating immunogen causing disease is a protein complementary (antisense) to the self-antigen, rather than a response to the native protein. The resulting primary antibody elicits an anti-antibody response or anti-idiotype, consequently producing a disease-inciting autoantibody. Yet, not everyone who developes self-reactive autoantibodies will manifest autoimmune disease. What is apparent is that manifestation of disease is governed by the acquisition of multiple immune-compromising traits that increase susceptibility and drive disease. Taking into account current cellular, molecular, and genetic information, six traits, or 'hallmarks', of autoimmune disease were proposed: (1) Autoreactive cells evade deletion, (2) Presence of asymptomatic autoantibodies, (3) Hyperactivity of Fc-FcR pathway, (4) Susceptibility to environmental impact, (5) Antigenic modifications of self-proteins, (6) Microbial Infections. Presented here is a discussion on how components delineated in the theory of autoantigen complementarity potentially promote the acquisition of multiple 'hallmarks' of disease.

PF-1355, a mechanism-based myeloperoxidase inhibitor, prevents immune complex vasculitis and anti-glomerular basement membrane glomerulonephritis

Small vessel vasculitis is a life-threatening condition and patients typically present with renal and pulmonary injury. Disease pathogenesis is associated with neutrophil accumulation, activation, and oxidative damage, the latter being driven in large part by myeloperoxidase (MPO), which generates hypochlorous acid among other oxidants. MPO has been associated with vasculitis, disseminated vascular inflammation typically involving pulmonary and renal microvasculature and often resulting in critical consequences. MPO contributes to vascular injury by 1) catabolizing nitric oxide, impairing vasomotor function; 2) causing oxidative damage to lipoproteins and endothelial cells, leading to atherosclerosis; and 3) stimulating formation of neutrophil extracellular traps, resulting in vessel occlusion and thrombosis. Here we report a selective 2-thiouracil mechanism-based MPO inhibitor (PF-1355 [2-(6-(2,5-dimethoxyphenyl)-4-oxo-2-thioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamide) and demonstrate that MPO is a critical mediator of vasculitis in mouse disease models. A pharmacokinetic/pharmacodynamic response model of PF-1355 exposure in relation with MPO activity was derived from mouse peritonitis. The contribution of MPO activity to vasculitis was then examined in an immune complex model of pulmonary disease. Oral administration of PF-1355 reduced plasma MPO activity, vascular edema, neutrophil recruitment, and elevated circulating cytokines. In a model of anti-glomerular basement membrane disease, formerly known as Goodpasture disease, albuminuria and chronic renal dysfunction were completely suppressed by PF-1355 treatment. This study shows that MPO activity is critical in driving immune complex vasculitis and provides confidence in testing the hypothesis that MPO inhibition will provide benefit in treating human vasculitic diseases.

Applications of urinary proteomics in renal disease research using animal models

Animal models of renal disease are essential tools in research on kidney disease and have provided valuable insights into pathogenesis. Use of animal models minimises inter-individual differences, allows specific pathological changes to be examined, and facilitates collection of tissue samples. Thus, mechanistic research and identification of biomarkers are possible. Various animal models manifesting specific pathological lesions can be used to investigate acute or chronic kidney disease (CKD). Urine, a terminal metabolic product, is produced via glomerular filtration, reabsorption, and excretion in the tubular and collecting ducts, reflecting the functions of glomeruli or tubular tissue stimulated in various ways or subject to disease. Almost 70 % of urinary proteins originate from the kidney (the other 30 % come from plasma), and urinary sampling is important to noninvasively detect renal disease. Proteomics is powerful when used to screen urine components. Increasingly, urine proteomics is used to explore the pathogenesis of kidney disease in animals and to identify novel biomarkers of renal disease. In this section, we will introduce the field of urinary proteomics as applied in different models of animal renal disease and the valuable role played by proteomics in noninvasive diagnosis and rational treatment of human renal disease.

Clinical research in a modern Chinese peritoneal dialysis center

A prerequisite for enhancing the quality of peritoneal dialysis is the continuous review and analysis of clinical data from routine clinical care and research. Here, we describe our strategy (Peking University First Hospital, Beijing, China) to achieve that objective.

What is the role of autoimmunity in type 1 diabetes? A clinical perspective

Despite tremendous research efforts, type 1 diabetes is one of the few remaining autoimmune diseases without any approved immunological treatment. This observation compels us to reconsider the role of autoimmunity in the pathogenesis of this disease. In this commentary, we will review solely human data in an attempt to appreciate, in an unbiased manner, the importance and relevance of the immunological alterations in patients with type 1 diabetes. The aim of this paper is to generate reflection on this topic, rather than a controversy.