Anti-glomerular Basement Membrane Research Articles

C/EBPδ Mediates Immunity to Renal Autoinflammatory Disorders in a Stage-specific Manner.

Kidney disease represents a major medical and economic burden for which improved treatments are urgently needed. Emerging data have implicated Th17 cells and IL-17 signaling in the underlying pathogenesis of autoantibody-induced glomerulonephritis (AGN). However, the downstream transduction pathways mediated by IL-17 in autoimmunity are not well defined. In this article, we show that CCAAT/enhancer-binding protein (C/EBP) δ is elevated in kidney biopsies from multiple manifestations of human AGN. C/EBPδ is similarly upregulated in a mouse model of anti-glomerular basement membrane protein-mediated kidney disease, and Cebpd-/- mice were fully refractory to disease. Although C/EBPδ is expressed in a variety of cell types, C/EBPδ was required only in the radioresistant compartment to drive GN pathology. C/EBPδ induced expression of several IL-17-induced kidney injury markers and cytokines implicated in disease, including Il6 and Lcn2. Because mouse AGN models do not progress to fibrosis, we employed a nephrotoxic injury model using aristolochic acid I to assess the contribution of the IL-17-C/EBPδ pathway to renal fibrotic events. Surprisingly, deficiency of either C/EBPδ or the IL-17 receptor caused kidney fibrosis to be enhanced. Thus, C/EBPδ and IL-17 play divergent and apparently stage-specific roles in the pathogenesis of kidney disease.

Immunoadsorption and Plasma Exchange are Comparable in Anti-Neutrophil Cytoplasmic Antibodies or Anti-Glomerular Basement Membrane Removal Kinetics

IntroductionApheresis allows the fast removal of auto-antibodies in anti-glomerular basement membrane (GBM) disease, and in severe ANCA-associated vasculitis. The CINEVAS study tested whether immunoadsorption (IA) allowed a faster removal of ANCA and/or anti-GBM antibodies than plasma exchanges (PEx). MethodsCINEVAS was a prospective multicenter study comparing IA to PEx in consecutive patients with ANCA and/or anti-GBM vasculitides. The primary objective was the reduction rate in auto-antibody titers between the beginning of the first and the end of the seventh apheresis session. Secondary objectives were: number of sessions needed to obtain desired reduction rates; reduction rates of total immunoglobulin (Ig) levels; tolerance of sessions; and patients’ outcome. ResultsThe results of 38 patients (16 treated with IA and 22 with PEx), and 43 auto-antibodies, were analyzed. There was no difference in the reduction rates in auto-antibody titers over 7 sessions between IA and PEx (respectively 98% vs 96%, p=0.39). The numbers of sessions needed to obtain undetectable auto-antibodies, or 50%, 75% or 90% reductions, did not differ between techniques. Greater reduction rates of auto-antibodies were observed when plasma was separated by filtration compared to centrifugation, with IA and PEx. IA allowed a greater reduction in total IgG levels, and better preservation of total IgA and IgM levels than PEx. PEx sessions required higher volumes of plasma, IA sessions higher volumes of citrate; IA sessions were longer. ConclusionsImmunoadsorption and plasma exchange were comparable in ANCA or anti-GBM removal kinetics, despite a faster reduction in total IgG with IA.

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.

#1603 A potent protein inhibitor of HB-EGF protects kidneys from glomerular lesions in a pig model of crescentic glomerulonephritis

Abstract Background and Aims Crescentic glomerulonephritis (CGN) is a severe disease that rapidly destroys the glomerular architecture. CGN is due to immuno-inflammatory aggressions triggered by anti-neutrophil cytoplasmic autoantibody-associated vasculitides, anti-glomerular basement membrane (GBM) autoantibodies, or immune complexes deposition as occurs in systemic lupus erythematosus, IgA nephropathy or infections. Treatments are based on aggressive immunosuppression. Although required, immunosuppression doesn't directly target the deleterious glomerular response to inflammation and leads to significant morbidity. Moreover, most patients still develop chronic or end-stage kidney failure, indicating that complementary strategies are needed. We showed previously that local over-expression of the growth factor HB-EGF (Heparin-binding EGF-like growth factor) and subsequent activation of EGFR lead to dedifferentiation and proliferation of parietal epithelial cells and podocytes, leading to crescentic lesions that irreversibly obliterate the glomeruli. We aimed to evaluate the therapeutic potential of a protein inhibitor of HB-EGF in a pig model of CGN. Method We engineered a protein inhibitor of HB-EGF, DTR8, from the receptor-binding domain of diphtheria toxin, a highly selective natural ligand of HB-EGF. Twelve mutations improved solubility, led to pM affinity, and reduced immunogenicity and antigenicity. Pigs received decomplemented nephrotoxic serum (NTS) from sheep immunized against pig GBM to mimic anti-GBM antibodies disease responsible for one form of CGN. Ten pigs were treated with 0.3 mg/kg of DTR8 twice a day by intramuscular route for 20 days, and 12 pigs received vehicle only starting 6 hours after NTS. Animals were sacrificed on day 21, and blood, urine and kidneys were analyzed. Five animals that had received pre-immune sheep serum served as controls. Results Pigs developed a nephritic syndrome with high proteinuria, hypoalbuminemia, kidney failure with increased BUN and blood creatinine levels, anasarca and crescentic lesions typical of CGN along with de novo HB-EGF glomerular overexpression. The vehicle-treated group had only 24.8% of histologically normal glomeruli, while the DTR8-treated group had 57.3% of healthy glomeruli. DTR8 treatment significantly reduced the percentage of crescentic lesions (P = .0365) and preserved podocyte differentiation as assessed by the expression of nephrin that was markedly reduced in vehicle-treated animals but maintained close to normal in DTR8-treated animals (P = .0028). DTR8 administration reduced EGFR phosphorylation in glomerular cells (P = .0161), suggesting local inhibition of the HB-EGF/EGFR cascade. Lymphocyte infiltration was reduced (P = .2543). Notably, the treatment group also displayed a global reduction in interstitial fibrosis (P = .0313). Conclusion The therapeutic protein candidate DTR8 protects kidney glomeruli in a CGN model in pigs.

#2889 Multiple renal tumors as an atypical clinical manifestation of granulomatosis with polyangiitis

Abstract Background and Aims Granulomatosis with polyangiitis (GPA) is a systemic small- vessel vasculitis associated with antineutrophilic cytoplasmic antibody (ANCA), in which kidney involvement often occurs. In some cases the course of vasculitis with kidney involvement is atypical, what complicates the diagnostic process and makes appropriate treatment difficult. Finding nodular masses in the kidneys always causes an oncological concern, while in the differential diagnosis a systemic vasculitis is rarely taken into account, what may lead to an unnecessary nephrectomy. Method We present a case of granulomatosis with polyangiitis (GPA) who presented with multiple tumors in the kidneys and adrenal gland. Results 29-year-old man experienced a sudden disease onset, at the age of 18 years, when due to peripheral oedema, nephrotic grade proteinuria (13.7 g/24 h), hematuria and presence of renal failure markers (serum creatinine 3.4 mg/dL), he was admitted to hospital. A suggestion of a rapidly progressive glomerulonephritis (RPGN) was put forward and a renal biopsy was performed (in the histopathological examination of the kidney, pauci-immune crescentic necrotizing glomerulonephritis was revealed). A treatment with plasmaphereses, high glucocorticosteroid doses and cyclophosphamide pulses was instituted. Haemodialysis therapy was also applied temporarily. ANCA and anti-glomerular basement membrane (GBM) antibodies were determined to give negative results. As a result of the remission-inducing treatment, an improvement of the renal function was obtained (serum creatinine 1.6-1.9 mg/dL). In spite of the remission-maintaining treatment with mycophenolate mofetil (MMF) and oral prednisone, after 10 years again a dramatic renal function impairment occurred, with a necessity of institution of a long-term haemodialysis therapy. Furthermore, on abdominal ultrasound examination multiple focal lesions were found in both kidneys, which rendered a kidney transplantation procedure in the patient impossible. In order to extend the diagnostic procedures, a magnetic resonance imaging (MRI) of the abdominal cavity without contrast agent administration was carried out (in both kidneys disseminated focal lesions were described: non-homogeneous, with moderately enhanced signal on T2-weighted images in the central part, without signs of water diffusion restriction; in the left kidney, of 23 x 22 mm and 19 x 15 mm dimensions; in the right kidney, of 30 x 32 mm, 26 x 22 mm and 22 x 18 mm dimensions. The picture of the lesions was unspecific and atypical. In the differential diagnosis granulomas could not have been ruled out, while disseminated proliferative lesions were less likely. Besides that, in both kidneys cysts of up to 7 mm diameters were present. In the lateral limb of the left adrenal gland a focal lesion was visible, of 23 x 14 mm dimensions, of a structure identical to that of the foci in both kidneys). On high-resolution computed tomography (HRCT) of the chest at the same time, small ground glass areas were found in the lungs. On positron emission tomography/computed tomography (PET/CT) no changes were visualised, suggesting presence of a metabolically active proliferative process. Tests for ANCA, antinuclear antibodies (ANA), anti- double-stranded DNA (dsDNA) antibodies, anti- GBM antibodies were again performed and gave negative results. He was diagnosed with granulomatosis with polyangiitis without ANCA and treated with corticosteroid and intravenous rituximab (4x 787 mg). Three months later, follow-up showed reduced mass lesions in the kidney and adrenal gland by MRI. Conclusion The case highlights the atypical clinical presentation of vasculitis and the significance of considering this possibility in differential diagnosis when confronting mass lesions present in the kidney.

#1155 Outcomes after kidney transplantation in anti-glomerular basement membrane disease

Abstract Background and Aims Anti-glomerular basement membrane antibody disease-associated glomerulonephritis (anti-GBM-GN) can lead to end-stage kidney disease (ESKD), requiring replacement therapy with dialysis or kidney transplant (KT). Few studies evaluated the outcome of these patients after KT. Our aim was to describe, in comparison with a control group, the occurrence of the following events: delayed graft function recovery, graft survival, relapse, acute rejection, overall survival; and to study the risk factors associated with these events. Method This was a retrospective, multicenter (6 French centers), observational study including patients who received a KT between 2005 and 2023 for ESKD secondary to anti-GBM-GN. Each vasculitis case receiving a KT was matched with 2 controls, matched on gender, center, recipient age (±5 years) and transplant period (±1 year). Event-free survival and the associated risk factors were analyzed. Results 126 patients were included, including 42 with anti-GBM-GN and 84 control patients. The median post-KT follow-up for vasculitis patients was 95 months. There was no difference in the occurrence of DGF between the groups (24 vs 18%, p = 0.5). There was no difference in graft survival when comparing both groups (78% vs 82% at 10 years, p = 0.48) (Fig. 1A). Only one patient experienced a relapse after KT (being anti-GBM negative at the time of transplantation). There was no difference in the incidence of acute rejection between the groups (p = 0.82). There was no difference in overall survival when comparing both groups (83% vs 89% at 10 years, p = 0.76) (Fig. 1B). Conclusion Kidney transplantation is an interesting option for patients with anti-GBM-GN: outcomes are similar to those of a matched population with similar occurrence of acute rejection, graft loss or death. Moreover, relapse rate is low. Comparison with a matched anti-GBM-GN population remaining on dialysis would be of interest to go further.

Macrophage-derived macrophage migration inhibitory factor mediates renal injury in anti-glomerular basement membrane glomerulonephritis

Macrophages are a rich source of macrophage migration inhibitory factor (MIF). It is well established that macrophages and MIF play a pathogenic role in anti-glomerular basement membrane crescentic glomerulonephritis (anti-GBM CGN). However, whether macrophages mediate anti-GBM CGN via MIF-dependent mechanism remains unexplored, which was investigated in this study by specifically deleting MIF from macrophages in MIFf/f−lysM−cre mice. We found that compared to anti-GBM CGN induced in MIFf/f control mice, conditional ablation of MIF in macrophages significantly suppressed anti-GBM CGN by inhibiting glomerular crescent formation and reducing serum creatinine and proteinuria while improving creatine clearance. Mechanistically, selective MIF depletion in macrophages largely inhibited renal macrophage and T cell recruitment, promoted the polarization of macrophage from M1 towards M2 via the CD74/NF-κB/p38MAPK-dependent mechanism. Unexpectedly, selective depletion of macrophage MIF also significantly promoted Treg while inhibiting Th1 and Th17 immune responses. In summary, MIF produced by macrophages plays a pathogenic role in anti-GBM CGN. Targeting macrophage-derived MIF may represent a novel and promising therapeutic approach for the treatment of immune-mediated kidney diseases.

#675 Application of ANCA-associated vasculitis Histopathological Classification and Renal Risk Score for prediction of end-stage kidney disease

Abstract Background and Aims Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a systemic autoimmune disease predominantly characterized by inflammation of small-sized blood vessels along with the presence of circulating ANCA. The kidney is frequently involved and, even though immunosuppressive therapy has dramatically improved the outcome of AAV patients, a significant proportion of patients progress to end-stage kidney disease (ESKD). Therefore, establishing and validating tools to predict renal outcomes in patients with AAV is crucial. Here we analyzed the application of two tools in predicting kidney survival in a Portuguese single-center cohort with AAV. Method We conducted a retrospective cohort study at a tertiary-care hospital in Portugal (Hospital de São João, Porto), from December 2010 to June 2023. Patients with a kidney biopsy-proven AAV were included. Serological ANCA-negative patients and patients with overlap syndromes, such as AAV in combination with anti-glomerular basement membrane disease, were excluded. Based on electronic records, information on demographics and clinical variables were collected. Kidney biopsies were reviewed to calculate: Berden histopathological classification and the Brix Renal Risk Score (RRS). Kidney survival was defined as the time from diagnosis to the need for kidney replacement therapy. A Kaplan-Meier analysis was performed to compare kidney survival based on the mentioned classifications. Results Fifty-one patients were enrolled, 78% (n = 40) of whom were positive for myeloperoxidase (MPO). The majority were men (61%, n = 31) with a mean age of 65 (± 12) years and a mean serum creatinine of 4.59 mg/dL (± 2.74) at diagnosis. During a median follow-up of 39 (IQR, 7-84) months, 20 patients (39%) progressed to end-stage kidney disease (ESKD), 10 patients (20%) died with preserved renal function and 21 patients (41%) did not need hemodialysis. Concerning Berden classification, 13 patients with a crescentic class, 4 patients with a mixed class and 3 patients with a sclerotic class developed ESKD. After 48 months of follow-up, renal survival was 100%, 90%, 61% and 26.7% in the focal, mixed, crescentic and sclerotic class groups, respectively. Berden classification did not correlate with kidney survival (p = 0.211). Concerning RRS, 10 patients in the high-risk group and 5 patients in the medium-risk group developed ESKD. After 48 months of follow-up, renal survival was 100% in the low-risk group, 85.7% in the medium-risk group, and 41.6% in the high-risk group. A correlation was established between kidney survival and RRS score (p = 0.003). Conclusion In our cohort RRS was predictive of ESKD, contrary to Berden histopathological classification. The information derived from these risk models strongly add to standard biochemical and clinical data. Patients with higher risk of ESKD need close follow-up and a tailored treatment plan regarding preparation for renal replacement therapy.

#417 Targeting parietal epithelial cell activation with mineralocorticoid receptor antagonism controls FSGS and crescentic glomerulonephritis

Abstract Background and Aims We have recently demonstrated that targeting specific pathways in parietal epithelial cells (PEC) can markedly alleviate experimental extracapillary glomerular injury [1]. Accumulating evidence has indicated the potential contributions of the mineralocorticoid receptor (MR) to the pathophysiology of chronic kidney disease. MR is expressed in endothelial cells, glomerular mesangial cells, podocytes, and distal tubular cells. Previous studies have shown that administering mineralocorticoid receptor antagonists has beneficial effects in various renal injury animal models, the role of the MR in extracapillary glomerulopathies is still elusive and mechanistically unclear. Methods To investigate the cell-specific role of the MR in PEC in the course of focal segmental glomerulosclerosis (FSGS) and crescentic glomerulonephritis (GN), we generated chimeric mice specifically lacking MR (Pec Cre Nr3c2lox/lox) in PECs using an inducible Cre recombinase system. Maladaptive FSGS was induced by combining a high-salt diet and deoxycorticosterone acetate (DOCA) with unilateral nephrectomy (DOCA-UniN). Crescentic glomerulonephritis (GN) was induced using the anti-glomerular basement membrane nephrotoxic serum (NTS) model. Results At baseline, Pec Cre Nr3c2wt/wt and Pec Cre Nr3c2lox/lox mice displayed no kidney morphology and function differences. When challenged by DOCA-UniN, PEC-selective Nr3c2 targeting significantly inhibited the expression of PEC activation markers Ki67, CD44, and FSGS lesions. Importantly, Pec Cre Nr3c2lox/lox mice showed less albuminuria and preserved renal function compared to Pec Cre Nr3c2 wt/wt counterparts. Likewise, Pec Cre Nr3c2lox/lox mice showed less albuminuria and preserved renal function in the NTS-induced CGN model. Crescents were also more numerous and organised in Pec Cre Nr3c2wt/wt mice than in Pec Cre Nr3c2lox/lox animals. Next, we examined whether pharmacological MR inhibition could alleviate the severity of crescentic GN. When Pec Cre Nr3c2wt/wt mice were orally given eplerenone for 14 days after the onset of the crescentic GN, they were significantly protected from renal injury and failure (decreased proteinuria, normal BUN and reduced number of crescent). Such global action was associated with less expression of the CD44 activation marker on PECs. Thus, genetic disruption of MR in PEC and pharmacological inhibition using eplerenone reduced glomerular expression of CD44 and crescent formation. Furthermore, kidney biopsies of individuals diagnosed with crescentic glomerulonephritis displayed increased expression of MR in PEC within FSGS and crescents. We next evaluated PEC migration under various conditions (DMSO, HB-EGF, Eplerenone, or HB-EGF+Eplerenone) for 24 hours. Eplerenone fully abrogated HB-EGF-induced PEC migration and Pcna, Snai1, and Vim mRNA expressions. Conclusion Altogether, these results indicate the critical role of MR in PEC activation during crescentic glomerulonephritis, along with the recently discovered CD9/EGFR/PDGFR [1] and CLDN1 pathways. This further supports the idea that the PEC phenotype switch is not a bystander event but plays a targetable critical active pathogenic role in FGSS and, more surprisingly, in crescentic GN. MR modulation using eplerenone may be a new therapeutic option for the management of such severe disease.

#1290 Adverse proinflammatory responses in the kidney after FGF23 administration in three murine kidney disease models

Abstract Background and Aims The hormone FGF23 is a biomarker associated with morbidity and mortality in individuals with and without kidney disease, but the role of FGF23 excess as a pathogenic factor is incompletely understood. Here, we investigated renal FGF23 signaling in kidney disease models. Method This study used three independent disease models: i) Male C57BL/6 mice (n = 16) were treated with Freud's adjuvant and nephrotoxic serum (NTS) to induce anti-glomerular basement membrane (anti-GBM) disease. ii) Female BALB/c mice (n = 8) were treated with adriamycin (doxorubicin) 10.5 mg/kg to induce focal and segmental glomerulosclerosis (FSGS). iii) Male DBA/2J mice (n = 20) were fed a diet containing adenine 0.2%. Control mice of the respective same strain and sex received vehicle injections. Mice of the anti-GBM and FSGS models and controls received intravenous injections of recombinant FGF23 1 µg or vehicle for six consecutive days (anti-GBM) or once (FSGS), with dissection 24 h after the last injection. Mice of the adenine model were dissected after 15 weeks. Following dissection, ex vivo precision-cut kidney slices (PCKS) were obtained from n = 4 mice and maintained for 24 at 37°C, 95% O2 and 5% CO2, followed by a 1 h treatment with recombinant FGF23 200 ng/ml or vehicle. Glomerular filtration rate (GFR) or renal retention parameters in serum and albuminuria were assessed. Kidneys underwent histological assessment using hematoxylin & eosin or Masson's trichrome. Renal RNA was isolated for bulk RNAseq. Differential gene expression was assessed to determine the effect of FGF23 treatment in disease-free controls, in each disease model, and the interaction between FGF23 X disease effect for the anti-GBM and FSGS groups. Gene set enrichment analysis was performed with a focus on the immune system. Results Anti-GBM mice showed a 45 ± 27% GFR decline (mean ± SD) compared to baseline, whereas controls showed an GFR increase of 11 ± 36% (p < 0.01). Kidney histology revealed an interstitial infiltrate. The FSGS model showed elevated serum creatinine and albuminuria, and hypercellularity in some glomeruli. Mice of the adenine model showed progressively increased blood urea nitrogen concentrations starting after 2 weeks, up to a 3-fold increase at week 14. Histology revealed interstitial fibrosis and tubular atrophy. Bulk RNAseq revealed proinflammatory transcriptional signatures after FGF23 treatment in all disease models, regardless of which timepoint or model: In the anti-GBM model, Hallmark gene sets of inflammatory response, interferon-α response, interferon-β response and allograft rejection were significantly increased after 6 days of FGF23 treatment, whereas disease-free controls showed no significantly changed immune gene sets after 6 days of FGF23. In FSGS mice, none of the Hallmark gene sets were changed after 1 FGF23 injection, but top individual gene expression affected by 1 FGF23 injection were an increased proinflammatory transcription factor Cebpb and an increased DNA damage transcript Dclre1b. Finally, the PCKS of adenine model revealed no significant Hallmark gene sets, but the two genes with differential expression were a proinflammatory macrophage/fibroblast chemokine Ccl4 (increased) and an immunoglobulin heavy variable Ighv2-2 (decreased). Conclusion FGF23-driven patterns of proinflammatory gene expression were observed in three experimental models of kidney disease, both in vivo and ex vivo assessment of FGF23 signaling, thus excluding effects of FGF23 on other organs. As these findings were limited to transcriptional analyses, the present data warrant further confirmation and exploration of FGF23 as a pathogenic agent in kidney disease.

#2842 Increased incidence of anti-glomerular basement membrane disease in Madrid in the past two decades

Abstract Background and Aims Recently, epidemiological changes have been identified in the incidence of anti-glomerular basement membrane (GBM) in different European regions, reporting an increased incidence in population-based studies in Ireland and Denmark, possibly due to demographic changes and exposure to environmental triggers, since the evidence of spatial and temporal clustering of cases suggests that environmental factors could be playing a role in this trend. The aim of our study was to evaluate the changes in incidence of anti-GBM disease in the past two decades in two different urban areas in Madrid (North and Southwest), identify possible environmental triggers, and analyse temporal and within-area differences in presentation and outcome of the disease. Method We performed a retrospective observational study using data between 2006 and 2022 from the hospital coding databases and laboratory databases of two hospitals in Madrid covering a population of 884000 residents. We collected data from patients who were diagnosed with anti-GBM disease with confirmed positive anti-GBM antibodies and renal and/or pulmonary manifestations. We excluded patients with positive anti-GBM antibodies without clinical manifestations suggestive of the disease. Incidence was described as per 100000 person-years at risk, and 95% confidence intervals were computed assuming a Poisson distribution. In order to detect changes in incidence, we divided the analysis into three time periods: 2006-2010, 2011-2016 and 2017-2022. We also compared the incidence before and after the onset of COVID-19 pandemic in Madrid (March 2020). Demographic data, clinical data at presentation, previous exposure to environmental factors (smoking, exposure to hydrocarbons, infections, vaccination), and treatments received and outcome was collected. Renal survival was defined as a state free from renal replacement therapy. Results During the 17-year study period, 26 cases of anti-GMN disease were identified (incidence rate 2.94 per 100000 persons); with a mean age of 52 ± 26 years at presentation, and 53.6% were females. 30.8% of patients were double-seropositive for ANCA and anti-GBM, 42.3% presented only renal involvement, 3.8% with only pulmonary involvement, and 53.8% with both renal and pulmonary involvement. At presentation, 19.2% of patients required mechanical ventilation and 65.4% required renal replacement therapy. After induction treatment, 13 patients (50%) remained on maintenance dialysis. After a median follow-up of 33 months, 46.2% patients died. Renal and patient survival after 1 year was 30.8% and 73.1% respectively. The incidence rate gradually increased from time periods 2006-2010 to 2017-2022, from 1.81 cases per 100000 persons (CI95% 0.78-3.57) to 2.83 cases per 100000 persons (CI95% 1.58-4.66) (OR 1.56, CI95%0.66-3.69, p = 0.30). We observed that the incidence rate significantly increased from 1.13 cases per 100000 persons (95% CI 0.62-1.90) before March 2020 to 4.53 cases per 100000 persons (95% CI 2.34-7.90) after the onset of the COVID-19 pandemic (OR 4, P < 0.001). Serum creatinine at presentation was significantly lower in cases diagnosed after COVID-19 (5.09 ± 4 vs 8.7 ± 3.9 mg/dl, p = 0.037). We found no differences within time periods in demographic data, previous exposure to environmental triggers, presence of double-seropositivity, or treatments received or patient survival after 1 year. However, we found that renal survival after 1 year has improved from 0% in 2006-2010 to 46.7% in 2017-2022 (p = 0.023) and 14.3% pre-COVID to 50% post-COVID (p = 0.049). Conclusion There is a gradual increase in the incidence rate of anti-GBM disease in our population, which has markedly increased after the COVID-19 pandemic, with a significantly lower serum creatinine at presentation with improved renal survival. We did not find any changes in the rate of exposure to known environmental triggers within time periods. These findings suggest that the rising incidence may be attributable to an increased awareness and diagnosis of anti-GBM disease, which leads to a better renal survival.

Transcriptome Analysis of BAFF/BAFF-R System in Murine Nephrotoxic Serum Nephritis.

Chronic kidney disease (CKD) is an emerging cause for morbidity and mortality worldwide. Acute kidney injury (AKI) can transition to CKD and finally to end-stage renal disease (ESRD). Targeted treatment is still unavailable. NF-κB signaling is associated with CKD and activated by B cell activating factor (BAFF) via BAFF-R binding. In turn, renal tubular epithelial cells (TECs) are critical for the progression of fibrosis and producing BAFF. Therefore, the direct involvement of the BAFF/BAFF-R system to the pathogenesis of CKD is conceivable. We performed non-accelerated nephrotoxic serum nephritis (NTN) as the CKD model in BAFF KO (B6.129S2-Tnfsf13btm1Msc/J), BAFF-R KO (B6(Cg)-Tnfrsf13ctm1Mass/J) and wildtype (C57BL/6J) mice to analyze the BAFF/BAFF-R system in anti-glomerular basement membrane (GBM) disease using high throughput RNA sequencing. We found that BAFF signaling is directly involved in the upregulation of collagen III as BAFF ko mice showed a reduced expression. However, these effects were not mediated via BAFF-R. We identified several upregulated genes that could explain the effects of BAFF in chronic kidney injury such as Txnip, Gpx3, Igfbp7, Ccn2, Kap, Umod and Ren1. Thus, we conclude that targeted treatment with anti-BAFF drugs such as belimumab may reduce chronic kidney damage. Furthermore, upregulated genes may be useful prognostic CKD biomarkers.

Atypical anti-glomerular basement membrane disease with membranous hyperplasia: diagnostic challenges and treatment variability

This case report presents a detailed analysis of a 31-year-old male patient who presented with a complex array of clinical symptoms, including proteinuria, hematuria, edema, and kidney insufficiency. Despite undergoing multiple tests, the results for anti-glomerular basement membrane antibodies yielded negative findings. Subsequently, kidney biopsy pathology revealed a distinct diagnosis of atypical anti-glomerular basement membrane (anti-GBM) disease with membrane hyperplasia. Treatment was initiated with a comprehensive approach involving high doses of corticosteroids therapy and cyclophosphamide (CTX). However, contrary to expectations, the patient’s kidney function exhibited rapid deterioration following this therapeutic regimen. The culmination of these complications necessitated a pivotal transition to maintenance hemodialysis. This case underscores the intricate challenges associated with diagnosing and managing rare and atypical presentations of kidney disorders. The negative anti-GBM antibody results and subsequent identification of atypical anti-GBM nephropathy highlight the need for tailored diagnostic strategies to discern subtle nuances within complex clinical scenarios. Additionally, the unexpected response to the treatment regimen emphasizes the potential variability in individual patient responses, underlining the necessity for vigilant monitoring and adaptable treatment strategies. This case report contributes to the evolving understanding of atypical kidney pathologies and the complexities involved in their management.

USP25 attenuates anti-GBM nephritis in mice by negative feedback regulation of Th17 cell differentiation

Purpose This study aimed to elucidate the role of USP25 in a mouse model of anti-glomerular basement membrane glomerulonephritis (anti-GBM GN). Methods USP25-deficient anti-GBM GN mice were generated, and their nephritis progression was monitored. Naïve CD4+ T cells were isolated from spleen lymphocytes and stimulated to differentiate into Th1, Th2, and Th17 cells. This approach was used to investigate the impact of USP25 on CD4+ T lymphocyte differentiation in vitro. Furthermore, changes in USP25 expression were monitored during Th17 differentiation, both in vivo and in vitro. Results USP25−/− mice with anti-GBM GN exhibited accelerated renal function deterioration, increased infiltration of Th1 and Th17 cells, and elevated RORγt transcription. In vitro experiments demonstrated that USP25−/− CD4+ T lymphocytes had a higher proportion for Th17 cell differentiation and exhibited higher RORγt levels upon stimulation. Wild-type mice with anti-GBM GN showed higher USP25 levels compared to healthy mice, and a positive correlation was observed between USP25 levels and Th17 cell counts. Similar trends were observed in vitro. Conclusion USP25 plays a crucial role in mitigating renal histopathological and functional damage during anti-GBM GN in mice. This protective effect is primarily attributed to USP25’s ability to inhibit the differentiation of naïve CD4+ T cells into Th17 cells. The underlying mechanism may involve the downregulation of RORγt. Additionally, during increased inflammatory responses or Th17 cell differentiation, USP25 expression is activated, forming a negative feedback regulatory loop that attenuates immune activation.

Laboratory diagnostics for vasculitis beyond antineutrophil cytoplasmatic autoantibodies

The diagnosis of systemic vasculitis (SV) is amajor clinical challenge due to the very different forms of presentation and requires an interdisciplinary approach. Targeted laboratory diagnostics support making the diagnosis, differential diagnosis and classification and are also akey component in the detection of active organ manifestations and treatment complications. The basic laboratory tests include the erythrocyte sedimentation rate (ESR), C‑reactive protein (CRP), blood count, serum creatinine, urinalysis, specific autoantibodies, complement, immunoglobulins, cryoglobulins and hepatitisB and C serology. Antineutrophil cytoplasmic autoantibodies (ANCA), antiglomerular basement membrane antibodies (anti-GBM antibodies) and anti-C1q antibodies are valuable laboratory markers for the diagnosis of the various forms of small vessel vasculitis. There are no specific laboratory tests for the diagnosis of medium and large vessel vasculitis. Despite advances in our understanding of the pathogenesis of vasculitis, no biomarkers have yet been identified that can be reliably used to guide treatment or that are useful in distinguishing vasculitis from other inflammatory diseases such as infections or treatment complications.

364 Atypical case of anti-glomerular basement membrane disease

364 Atypical case of anti-glomerular basement membrane disease

Two acute kidney injury episodes after ICI therapy: a case report.

A 74-year-old Japanese male with lung squamous cell carcinoma received his first dose of immune checkpoint inhibitors (ICIs): ipilimumab and nivolumab. He developed acute kidney injury (AKI) and was admitted to our department. We diagnosed kidney immune-related adverse effects (irAE), and a kidney biopsy revealed acute tubulointerstitial nephritis. We started oral prednisolone (PSL) and his AKI immediately improved. The patient maintained stable findings after PSL was tapered off. However, seven months after the ICI administration, he developed rapid progressive glomerular nephritis and was admitted to our department again. The second kidney biopsy showed findings consistent with anti-glomerular basement membrane glomerulonephritis. Although the patient was treated with pulse methylprednisolone followed by oral PSL and plasma exchange, he became dependent on maintenance hemodialysis. To our knowledge, no case report has described two different types of biopsy-proven nephritis. In cases of suspected relapsing kidney irAEs, both a relapse of previous nephritis and the development of another type of nephritis should be considered.

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 presentationincluding 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 6months. This case reports the successful remission of a patient with Goodpasture's syndrome after induction with rituximab.

Infective Endocarditis Caused by Streptococcus sanguinis Resulting in Stroke, Ruptured Infected Pseudoaneurysm of Superior Mesenteric Artery, and Rapidly Progressive Glomerulonephritis.

A 71-year-old-man was admitted to our hospital with a cerebral embolism and diagnosed with infective endocarditis (IE) caused by Streptococcus sanguinis. Mitral valve replacement was performed. About one month later, he experienced sudden abdominal pain and shock due to a ruptured infected mesenteric artery pseudoaneurysm. Forty-four days after abdominal surgery, he presented with rapidly progressive glomerulonephritis with anti-glomerular basement membrane antibodies. He was treated with plasma exchange and prednisolone, and his renal function gradually improved. Since postoperative complications often occur within a few years after surgery for IE, careful follow-up is important, even after antimicrobial therapy and valve surgery.

Atypical Anti-Glomerular Basement Membrane Nephritis: A Case Series From the French Nephropathology Group

Rationale & ObjectiveAtypical anti-glomerular basement membrane (GBM) nephritis is characterized by a bright linear immunoglobulin staining along the GBM by immunofluorescence without a diffuse crescentic glomerulonephritis nor serum anti-GBM antibodies by conventional ELISA. We characterized a series of patients with atypical anti-GBM disease. Study DesignCase series. Setting & ParticipantsPatients were identified by the French Nephropathology Group as having atypical anti-GBM nephritis between 2003 and 2022. FindingsAmong 38 potential cases, 25 were included. 14 (56%) were female and 23 (92%) had hematuria. Median [interquartile range (IQR)] serum creatinine at diagnosis was 150 [102-203] μmol/L and median [IQR] urine protein to creatinine ratio was 2.4 [1.3-5.2] g/g. 9 (36%) patients had endocapillary proliferative glomerulonephritis (GN), 4 (16%) had mesangial proliferative GN, 4 (16%) had membranoproliferative GN, 2 (8%) had pure and focal crescentic GN, 1 (4%) had focal segmental glomerulosclerosis, and 5 had glomeruli that were unremarkable on histopathology. Nine patients (36%) had crescents, involving a median of 9% of glomeruli. Bright linear staining for IgG was seen in 22 cases (88%) and for IgA in 3 cases (12%). The nine patients (38%) who had a monotypic staining pattern tended to be older with less proteinuria and rarely had crescents. Kidney survival rate at one year was 83% and did not appear to be associated with the light chain restriction. LimitationsRetrospective case series with a limited number of biopsies including electron microscopy. ConclusionsCompared to typical anti-GBM disease, atypical anti-GBM nephritis frequently presents with endocapillary or mesangial proliferative glomerulonephritis pattern and appears to have slower disease progression. Further studies are needed to fully characterize its pathophysiology and associated clinical outcomes.