The HLA complex in Goodpasture's disease: a model for analyzing susceptibility to autoimmunity

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

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

The Association of Class I and II Human Leukocyte Antigen Serotypes With End-Stage Kidney Disease Due to Membranoproliferative Glomerulonephritis and Dense Deposit Disease

RATIONALE & OBJECTIVE

Membranoproliferative glomerulonephritis (MPGN), encompassing several distinct diseases, is a rare but significant cause of kidney failure in the United States. The potential etiologies of MPGN are unclear, but prior studies have suggested dysregulation of the alternative complement pathway and, recently, autoimmunity as potential mechanisms driving MPGN pathogenesis. In this study, we examined HLA associations with end-stage kidney disease (ESKD) due to MPGN and dense deposit disease (DDD) in a large racially and ethnically diverse US-based cohort.

STUDY DESIGN

Case-control study.

SETTING & PARTICIPANTS

Using US Renal Data System (USRDS) and United Network for Organ Sharing (UNOS) data, we identified 3,424 patients with kidney failure due to MPGN and 263 due to DDD. We matched patients to kidney donor controls on designated race and ethnicity in a 1:15 ratio.

EXPOSURE

58 class I and II HLA serotypes.

OUTCOME

Case-control status.

ANALYTICAL APPROACH

For each disease cohort, univariable and multivariable logistic regression analyses were used to investigate associations between the disease and 58 HLA serotypes. In subgroup analyses, we investigated HLA associations in White and Black patients. We also studied antiglomerular basement membrane (anti-GBM) nephritis as a positive-control outcome. We applied a Bonferroni correction to account for multiple comparisons.

RESULTS

Eighteen serotypes were significantly associated with the odds of having MPGN in univariable analyses, with DR17 having the strongest association (odds ratio [OR], 1.55 [95% CI, 1.44-1.68], P=4.33e-28). No significant associations were found between any HLA serotype and DDD. Designated race-specific analyses showed comparable findings. We recapitulated known HLA associations in anti-GBM nephritis.

LIMITATIONS

Reliance on HLA serotypes (rather than genotype), lack of biopsy-confirmed diagnoses.

CONCLUSIONS

HLA-DR17 is associated with ESKD due to MPGN in a racially and ethnically diverse cohort. The strength of association was similar in White and Black patients, suggesting a role in the pathogenesis of MPGN. No HLA associations were observed in patients with DDD.

PLAIN-LANGUAGE SUMMARY

Prior studies have suggested dysregulation of the alternative complement pathway as a potential etiology of membranoproliferative glomerulonephritis (MPGN), but recent evidence from a British White population has implicated an autoimmune mechanism in MPGN pathogenesis. We investigated HLA associations between MPGN and dense deposit disease (DDD) in a large racially and ethnically diverse cohort of patients. We found that HLA-DR17 is associated with end-stage kidney disease (ESKD) due to MPGN in both White and Black patients. By contrast, no significant HLA associations with ESKD due to DDD were identified. These results suggest a role for autoimmunity in some cases of MPGN and highlight differences in the disease etiology of MPGN compared with DDD.

Mechanisms and biomarkers of immune-related adverse events in gastric cancer

Immune-checkpoint inhibitors (ICIs), different from traditional cancer treatment models, have shown unprecedented anti-tumor effects in the past decade, greatly improving the prognosis of many malignant tumors in clinical practice. At present, the most widely used ICIs in clinical immunotherapy for a variety of solid tumors are monoclonal antibodies against cytotoxic T lymphocyte antigen-4 (CTLA-4), programmed cell death protein 1 (PD-1) and their ligand PD-L1. However, tumor patients may induce immune-related adverse events (irAEs) while performing immunotherapy, and irAE is an obstacle to the prospect of ICI treatment. IrAE is a non-specific disease caused by immune system imbalance, which can occur in many tissues and organs. For example, skin, gastrointestinal tract, endocrine system and lung. Although the exact mechanism is not completely clear, related studies have shown that irAE may develop through many ways. Such as excessive activation of autoreactive T cells, excessive release of inflammatory cytokines, elevated levels of autoantibodies, and common antigens between tumors and normal tissues. Considering that the occurrence of severe IrAE not only causes irreversible damage to the patient's body, but also terminates immunotherapy due to immune intolerance. Therefore, accurate identification and screening of sensitive markers of irAE are the main beneficiaries of ICI treatment. Additionally, irAEs usually require specific management, the most common of which are steroids and immunomodulatory therapies. This review aims to summarize the current biomarkers for predicting irAE in gastric cancer and their possible mechanisms.

Genetic variation in the human leukocyte antigen region confers susceptibility to Clostridioides difficile infection

Clostridioides difficile (C. diff.) infection (CDI) is a leading cause of hospital acquired diarrhea in North America and Europe and a major cause of morbidity and mortality. Known risk factors do not fully explain CDI susceptibility, and genetic susceptibility is suggested by the fact that some patients with colons that are colonized with C. diff. do not develop any infection while others develop severe or recurrent infections. To identify common genetic variants associated with CDI, we performed a genome-wide association analysis in 19,861 participants (1349 cases; 18,512 controls) from the Electronic Medical Records and Genomics (eMERGE) Network. Using logistic regression, we found strong evidence for genetic variation in the DRB locus of the MHC (HLA) II region that predisposes individuals to CDI (P > 1.0 × 10-14; OR 1.56). Altered transcriptional regulation in the HLA region may play a role in conferring susceptibility to this opportunistic enteric pathogen.

Case Report: Bilateral Lung Transplantation for Rapidly Progressive Undifferentiated Interstitial Lung Disease—A Cautionary Tale

Interstitial lung disease is fast becoming one of the most common indications for lung transplantation (LTx); however, LTx for Goodpasture's syndrome with pulmonary involvement has not been previously described in the literature. In this report, we outline the case of a young male with undifferentiated rapidly progressive interstitial lung disease who ultimately received a bilateral sequential LTx after deterioration requiring extracorporeal membrane oxygenation. The original disease soon recurred in the graft, and unfortunately, the patient did not survive. The diagnosis of Goodpasture's syndrome was made postmortem and was not clearly evident on examination of the native explanted tissue, nor was there an elevated titer of antiglomerular basement membrane antibodies during his initial work-up. We hypothesize that the donor and recipient's HLA profile made him more susceptible to aggressive disease. In hindsight, active Goodpasture's disease would have been a contraindication to proceed to transplantation. This case is a cautionary reminder of the high stakes of performing LTx without a certain diagnosis.

Research advances on targeted-Treg therapies on immune-mediated kidney diseases

The primary function of regulatory T cells (Tregs) is blocking the pathogenic immunological response mediated by autoreactive cells, establishing and maintaining immune homeostasis in tissues. Kidney diseases are often caused by Immune imbalance, including alloimmune graft damage after renal transplantation, direct immune-mediated kidney diseases like membranous nephropathy (MN) and anti-glomerular basement membrane (anti-GBM) glomerulonephritis, as well as indirect immune-mediated ones like Anti-neutrophil cytoplasmic antibody-associated vasculitis (AAVs), IgA nephropathy (IgAN) and lupus nephritis (LN). Treg cells are deficient numerically and/or functionally in those kidney diseases. Targeted-Treg therapies, including adoptive Tregs transfer therapy and low-dose IL-2 therapy, have begun to thrive in treating autoimmune diseases in recent years. However, the clinical use of targeted Treg-therapies is rarely mentioned in those kidney diseases above except for kidney transplantation. This article mainly discusses the newest progressions of targeted-Treg therapies in those specific examples of immune-mediated kidney diseases. Meanwhile, we also reviewed the main factors that affect Treg development and differentiation, hoping to inspire new strategies to develop target Tregs-therapies. Lastly, we emphasize the significant impediments and prospects to the clinical translation of target-Treg therapy. We advocate for more preclinical and clinical studies on target Tregs-therapies to decipher Tregs in those diseases.

The role of HLA antigens in recurrent primary focal segmental glomerulosclerosis

Primary focal segmental glomerulosclerosis (FSGS), typically characterized by diffuse podocyte foot process effacement and nephrotic syndrome (diffuse podocytopathy), is generally attributed to a circulating permeability factor. Primary FSGS can recur after transplantation where it manifests as diffuse foot process effacement in the early stages, with subsequent evolution of segmental sclerotic lesions. Previous published literature has been limited by the lack of stringent selection criteria to define primary FSGS. Although immunogenetic factors play an important role in many glomerular diseases, their role in recurrent primary FSGS post-transplantation has not been systematically investigated. To address this, we retrospectively studied a multicenter cohort of 74 kidney allograft recipients with end stage kidney disease due to primary FSGS, confirmed by clinical and histologic parameters. After adjusting for race/ethnicity, there was a numeric higher frequency of HLA-A30 antigen in primary FSGS (19%) compared to each of 22,490 healthy controls (7%, adjusted OR=2.0, P=0.04) and 296 deceased kidney donors (10%, OR=2.1, P=0.03). Within the group of transplant patients with end stage kidney disease due to primary FSGS, donor HLA-A30 was associated with recurrent disease (OR=9.1, P=0.02). Multivariable time-to-event analyses revealed that recipients who self-identified as Black people had lower risk of recurrent disease, probably reflecting enrichment of these recipients with APOL1 high-risk genotypes. These findings suggest a role for recipient and donor immunogenetic makeup in recurrent primary FSGS post-transplantation. Further larger studies in well-defined cohorts of primary FSGS that include high-resolution HLA typing and genome-wide association are necessary to refine these hereditary signals.

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.

Mycobacterium avium Complex Lung Disease Complicated With Antiglomerular Basement Membrane Disease: A Case Report

While both Mycobacterium avium complex (MAC) lung diseases and antiglomerular basement membrane (anti-GBM) antibody disease may cause hemoptysis, no case presenting hemoptysis having both diseases has been reported. A woman in her 80s was admitted due to hemoptysis with acute respiratory failure. MAC was isolated from her sputum, and a positive report for anti-GBM antibody was confirmed in screening for hematuria. This patient has been successfully treated with systemic corticosteroid therapy followed by combination chemotherapy against MAC. Although anti-GBM disease is a rare condition, screening might be recommended in case of uncontrollable hemoptysis as MAC lung disease with hematuria.

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

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

A Case of Paediatric Anti-Glomerular Basement Membrane Disease Associated with Thrombotic Thrombocytopenic Purpura

Anti-GBM disease is a rare vasculitis that causes rapid progressive glomerulonephritis and pulmonary haemorrhage. It is usually an adult diagnosis with isolated paediatric cases reported. Thrombotic thrombocytopenic purpura (TTP) is a rare thrombotic microangiopathy mainly affecting adults that causes multiorgan ischaemia, microangiopathic haemolytic anaemia, and thrombocytopenia. We present the first paediatric case of concurrent anti-GBM disease and TTP. A 14-year-old boy presented with acute kidney failure and severe pulmonary haemorrhage due to anti-GBM disease, confirmed on auto-antibody testing. There was thrombocytopenia and moderately low ADAMTS13 activity suggestive of TTP. The renal prognosis was poor with a need for dialysis. He was severely unwell with pulmonary haemorrhages requiring the use of extracorporeal membrane oxygenation (ECMO). His disease was treated with corticosteroids, plasma exchange (PEX), rituximab, and cyclophosphamide, resulting in remission. Anti-GBM disease is rare in children but should be considered in those presenting with acute kidney injury, particularly where there has been exposure to pulmonary irritants. An aggressive presentation warrants aggressive treatment with methylprednisolone, PEX, and cyclophosphamide. Rituximab may benefit patients that have concurrent TTP. TTP may exacerbate pulmonary disease, but complete respiratory recovery is possible. Disease relapse is rare in the paediatric age group, and these patients are candidates for kidney transplantation.

How Thymocyte Deletion in the Cortex May Curtail Antigen-Specific T-Regulatory Cell Development in the Medulla

CD4⁺ T cell responses to self-antigens are pivotal for immunological self-tolerance. Activation of Foxp3^– T-conventional (T-conv) cells can precipitate autoimmune disease, whereas activation of Foxp3⁺ T-regulatory (T-reg) cells is essential to prevent autoimmune disease. This distinction indicates the importance of the thymus in controlling the differentiation of self-reactive CD4⁺ T cells. Thymocytes and thymic antigen-presenting cells (APC) depend on each other for normal maturation and differentiation. In this Hypothesis and Theory article, we propose this mutual dependence dictates which self-antigens induce T-reg cell development in the thymic medulla. We postulate self-reactive CD4⁺ CD8^– thymocytes deliver signals that stabilize and amplify the presentation of their cognate self-antigen by APC in the thymic medulla, thereby seeding a niche for the development of T-reg cells specific for the same self-antigen. By limiting the number of antigen-specific CD4⁺ thymocytes in the medulla, thymocyte deletion in the cortex may impede the formation of medullary T-reg niches containing certain self-antigens. Susceptibility to autoimmune disease may arise from cortical deletion creating a “hole” in the self-antigen repertoire recognized by T-reg cells.

Etanercept-Induced Anti-Glomerular Basement Membrane Disease

Anti-glomerular basement membrane (anti-GBM) disease is a rare form of small-vessel vasculitis that typically causes rapidly progressive glomerulonephritis with or without alveolar haemorrhage. Previously, there has only been one reported case of tumour necrosis factor-α (TNF-α) antagonist-induced anti-GBM disease. Here, we describe the first reported case of etanercept-induced anti-GBM disease. A 55-year-old Caucasian man was referred to our tertiary specialist renal centre with a history of painless macroscopic haematuria. The patient has been receiving weekly etanercept injections over the past 12 months for psoriatic arthropathy. The serum immunology panel results highlighted a significantly raised anti-GBM titre (370.1 U). Etanercept was stopped, and the patient was empirically commenced on pulsed methylprednisolone, cyclophosphamide, and plasma exchange. A renal biopsy showed crescentic glomerulonephritis. Few days after admission, he tested positive for coronavirus disease 2019 (COVID-19), and a decision was made to withhold cyclophosphamide. There was further decline in renal function with hyperkalaemia for which he received 2 sessions of haemodialysis. He was restarted on cyclophosphamide upon discharge. The patient was switched to rituximab treatment afterwards as he developed leucopenia 2 weeks following the commencement of cyclophosphamide. The serum creatinine level continued to improve and remained dialysis-independent. In conclusion, with the increased use of etanercept and other TNF-α antagonists, the prescribing clinician must be aware of the rare but life-threatening drug-induced vasculitis. We recommend careful monitoring of renal indices with the use of this class of medications.

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

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

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

RATIONALE

Simultaneous occurrence of anti-glomerular basement membrane (anti-GBM) disease and thin basement membrane nephropathy (TBMN), both of which invade the type IV collagen subunits, is very rare. Here, we present the case of a 20-year-old male patient diagnosed with both anti-GBM disease and TBMN upon presenting dyspnea and hemoptysis.

PATIENT CONCERNS

No laboratory abnormalities, except arterial hypoxemia (PaO275.4 mmHg) and microscopic hematuria, were present. Chest computed tomography revealed bilateral infiltrations in the lower lung fields; thus, administration of empirical antibiotics was initiated. Gross hemoptysis persisted nonetheless, and bronchoscopy revealed diffuse pulmonary hemorrhage with no endobronchial lesions. Broncho-alveolar lavage excluded bacterial pneumonia, tuberculosis, and fungal infection.

DIAGNOSIS

Enzyme-linked immunosorbent assay of his serum was positive for anti-GBM antibody (95.1 U/mL). Human leukocyte antigen (HLA) test was positive for both HLA-DR15/-DR04. Other than diffuse thinning of the GBM (average thickness, 220 nm), index kidney biopsy did not demonstrate any specific abnormalities such as crescent formation.

INTERVENTIONS

Methylprednisolone was administered intravenously for 7 consecutive days (500 mg/day), followed by the daily dose of oral prednisolone (80 mg). Cyclophosphamide was also orally administered every day for 3 months (250 mg/day). Following 6 sessions of plasmapheresis, the anti-GBM antibody in serum became negative.

OUTCOMES

There was no clinical evidence suggesting recurrence of pulmonary hemorrhage or azotemia during hospitalization and 12-month follow-up period. Twelve months after hospital discharge, oral prednisolone was discontinued.

LESSONS

The patients with concurrent anti-GBM disease and TBMN will have a favorable prognosis after proper therapy. However, further research is needed to elucidate the pathogenesis and long-term outcome of the comorbidity of these 2 diseases.

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

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

Recurrence and Outcome of Anti-Glomerular Basement Membrane Glomerulonephritis After Kidney Transplantation

Introduction

Recurrence of anti-glomerular basement membrane (anti-GBM) glomerulonephritis in the kidney graft is a rare event, described in limited reports. The aim of this study was to evaluate, in a large cohort of patients with long follow-up, the risk of recurrence of anti-GBM disease, the risk factors associated with clinical recurrence, and the long-term patient and graft survival.

Methods

This was a multicenter retrospective study. Inclusion criteria were patients with anti-GBM glomerulonephritis who underwent transplantation of a kidney between 1977 and 2015. Exclusion criteria were systemic vasculitis, lupus erythematosus, and cryoglobulinemia. Recurrence was defined as reappearance of clinical signs of glomerulonephritis along with histological signs of proliferative glomerulonephritis and linear IgG staining on kidney biopsy, with or without anti-GBM antibodies.

Results

A total of 53 patients were included. Recurrence of anti-GBM glomerulonephritis in a first kidney transplant occurred in only 1 patient 5 years after transplantation (a prevalence rate of 1.9%) in the context of cessation of immunosuppressive drugs, and resulted in graft loss due to recurrence. Linear IgG staining on kidney biopsy in the absence of histological signs of proliferative glomerulonephritis was observed in 4 patients, in the context of cellular rejection. Patient survival was 100%, 94%, and 89% at 5, 10, and 15 years, respectively. Death-censored first-graft survival rates were 88%, 83%, and 79% at 5, 10, and 15 years, respectively.

Conclusion

The recurrence rate of anti-GBM glomerulonephritis after transplantation is very low but is associated with graft loss. The long-term patient and graft survival rates are excellent.

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

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

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

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

Common Denominators in the Immunobiology of IgG4 Autoimmune Diseases: What Do Glomerulonephritis, Pemphigus Vulgaris, Myasthenia Gravis, Thrombotic Thrombocytopenic Purpura and Autoimmune Encephalitis Have in Common?

IgG4 autoimmune diseases (IgG4-AID) are an emerging group of autoimmune diseases that are caused by pathogenic autoantibodies of the IgG4 subclass. It has only recently been appreciated, that members of this group share relevant immunobiological and therapeutic aspects even though different antigens, tissues and organs are affected: glomerulonephritis (kidney), pemphigus vulgaris (skin), thrombotic thrombocytopenic purpura (hematologic system) muscle-specific kinase (MuSK) in myasthenia gravis (peripheral nervous system) and autoimmune encephalitis (central nervous system) to give some examples. In all these diseases, patients’ IgG4 subclass autoantibodies block protein-protein interactions instead of causing complement mediated tissue injury, patients respond favorably to rituximab and share a genetic predisposition: at least five HLA class II genes have been reported in individual studies to be associated with several different IgG4-AID. This suggests a role for the HLA class II region and specifically the DRβ1 chain for aberrant priming of autoreactive T-cells toward a chronic immune response skewed toward the production of IgG4 subclass autoantibodies. The aim of this review is to provide an update on findings arguing for a common pathogenic mechanism in IgG4-AID in general and to provide hypotheses about the role of distinct HLA haplotypes, T-cells and cytokines in IgG4-AID.

Immune regulation in renal inflammation

Renal inflammation, induced by autoantigen recognition or toxic drugs, leads to renal tissue injury and decline in kidney function. Recent studies have demonstrated the crucial role for regulatory T cells in suppressing pathogenic adaptive but also innate immune responses in the inflamed kidney. However, there is also evidence for other immune cell populations with immunosuppressive function in renal inflammation. This review summarizes mechanisms of immune cell regulation in immune-mediated glomerulonephritis and acute and chronic nephrotoxicity.

Human leucocyte antigen-associated anti-glomerular basement membrane disease in siblings

We report a case of anti-glomerular basement membrane (GBM) disease in association with human leucocyte antigen (HLA) DRB1 15:01. A 71-year-old woman presented with oligoanuric acute kidney injury accompanied by high titre anti-GBM antibodies. Renal biopsy revealed a severe crescentic glomerulonephritis. Her brother had presented 6 years earlier with oligoanuric acute kidney injury. He was dual positive for MPO ANCA and anti-GBM antibodies. Renal biopsy was not performed. Both had an absence of pulmonary involvement. Tissue typing confirmed both were heterozygous for HLA DRB1 15:01 and DRB1 04:03.

Human leucocyte antigen DR15, a possible predictive marker for immune checkpoint inhibitor-induced secondary adrenal insufficiency

BACKGROUND

Immune checkpoint inhibitors (ICPis) induce various immune-related adverse events (irAEs), despite their beneficial effects in treating various advanced cancers. ICPi-induced secondary adrenal insufficiency is described as a prevalent and serious 'pituitary irAE.' However, its precise mechanism remains unclear, and no definitive predictive markers have been reported.

PATIENTS AND METHODS

We enrolled and studied 11 patients with advanced cancer (aged 39-70 years; 6 male patients) receiving nivolumab, pembrolizumab or ipilimumab who developed pituitary irAEs. Their clinical data, including endocrine functions, were retrospectively assessed and human leucocyte antigen (HLA) genotypes were determined to compare the HLA allele frequencies in these patients and healthy controls.

RESULTS

Among 11 patients, 7, 3 and 1 patients exhibited malignant melanoma, non-small-cell lung cancer and gastric cancer, respectively. HLA type screening results revealed that HLA-DR15, B52 and Cw12 were observed in 9, 7, and 7 patients with pituitary irAE, respectively. DR15, B52 and Cw12 were significantly more prevalent in our group than in the healthy control group from the Japanese HLA-haplotype database (this study vs healthy control group); DR15: 81.8% vs 33.5% (n = 11, P = 0.0014), B52: 63.6% vs 21.0% (n = 11, P = 0.0026) and Cw12: 70% vs 21.3% (n = 10, P = 0.0013).

CONCLUSIONS

HLA-DR15, B52 and Cw12 are possible predisposing factors for pituitary irAEs. HLA-DR15 is reportedly associated with autoimmune disease via interleukin-17 regulation, suggesting its involvement in pituitary irAE development. Using HLA haplotypes as pituitary irAE predictive markers, we could provide safe ICPi treatment and understand irAE pathogenesis.

Molecular Analysis of Goodpasture's Disease Following Hematopoietic Stem Cell Transplant in a Pediatric Patient, Recalls the Conformeropathy of Wild-Type Anti-GBM Disease

Background: Goodpasture's disease (GP) is mediated by autoantibodies that bind the glomerular and alveolar basement membrane, causing rapidly progressive glomerulonephritis with or without pulmonary hemorrhage. The autoantibodies bind neoepitopes formed upon disruption of the quaternary structure of α345NC1 hexamer, a critical structural domain of α345 collagen IV scaffolds. Hexamer disruption leads to a conformational changes that transitions α3 and α5NC1 subunits into immunogens, however, the trigger remains unknown. This contrasts with another anti-GBM disease, Alports' post-transplant nephritis (APTN), where the pathogenic alloantibody binds directly to native NC1 hexamer. The current report includes the first study of antigenic specificity and allo-incompatability in anti-GBM disease occurring after allogeneic haematopoietic stem cell transplant (HSCT).

Results: The anti-GBM antibodies were found to be directed predominantly against the E_A epitope of the α3 NC1 monomer of collagen IV and developed rapidly in patient serum reaching peak level within 5 weeks. Autoantibody binding to native α345NC1 hexamer was minimal; however, binding was greatly increased upon dissociation of the native hexamer. There were no polymorphic genetic differences between donor and recipient collagen IV genes which would be predicted to cause a significant NC1 conformational change or to provide a target for antibody binding. Both patient and donor possessed the Goodpasture's susceptibility HLA-allele DRB1^*1501.

Conclusions: The current report includes the first in-depth study of allo-incompatability and antigenic specificity in anti-GBM disease occurring after allogeneic haematopoietic stem cell transplant (HSCT). No polymorphic genetic differences were identified between donor and recipient collagen IV genes which would be predicted to provide a target for antibody binding. Furthermore, autoantibody binding to native α345NC1 hexamer was minimal, increasing greatly upon dissociation of the native hexamer, resembling wild-type GP diseases and marking this as the first example of a post-HSCT conformeropathy.

HLA-DR15-specific inhibition attenuates autoreactivity to the Goodpasture antigen

Goodpasture's disease manifests as rapidly progressive glomerulonephritis. Current immunosuppressive treatments do not specifically target the pathological immune response and have significant side effects. Like most autoimmune diseases, the strongest genetic association is with the HLA alleles. Inheritance of HLA-DR15 confers susceptibility, and structure-function studies have shown that HLA-DR15 plays a causative role in activating autoreactive pro-inflammatory T cells. Thus, specific inhibition of HLA-DR15 would provide a targeted therapeutic approach. We hypothesised that PV-267, an HLA-DR15-specific inhibitor, would effectively block HLA-DR15 presentation of the dominant epitope, attenuate the activation of autoreactive T cells, and limit disease. Using humanised HLA-DR15 transgenic mice, α3_135-145-specific, pro-inflammatory T cell recall responses were measured using IFN-γ and IL-17A ELISPOTs and by proliferation assay. To determine if PV-267 could limit disease, experimental autoimmune anti-GBM glomerulonephritis was induced in HLA-DR15 transgenic mice (on an Fcgr2b^-/- background), and functional and histological disease endpoints were measured. PV-267 effectively inhibited α3_135-145-specific immune responses and disease development. Mice treated prior to immunization with α3_135-145 had reduced α3_135-145-specific recall responses, and limited disease by albuminuria, histological glomerular injury, IgG deposition, and inflammatory cell infiltrates. PV-267 treatment commencing after the onset of active anti-α3(IV)NC1 autoimmunity attenuated functional and histological renal injury. When treatment was administered after disease was established, PV-267 limited the severity of histological injury. In conclusion, HLA-DR15 inhibition attenuates α3(IV)NC1-specific pro-inflammatory responses and could be used as an adjunct therapy for anti-GBM disease.

Incidence, management, and outcomes of autoimmune nephropathies following alemtuzumab treatment in patients with multiple sclerosis

Background:

Autoimmune disorders including nephropathies have been reported more frequently in alemtuzumab-treated multiple sclerosis (MS) patients than in the general population.

Objective:

Describe instances of autoimmune nephropathy in alemtuzumab-treated MS patients.

Methods:

Cases were identified from safety monitoring within the alemtuzumab relapsing-remitting multiple sclerosis (RRMS) clinical development program (CDP) or post-marketing, or following off-label use.

Results:

As of 16 June 2017, 16 autoimmune nephropathies have occurred following alemtuzumab treatment for MS. The incidence of autoimmune nephropathies was 0.34% within the CDP (5/1485 patients). The five CDP cases (one of anti-glomerular basement membrane (anti-GBM) disease, two of membranous glomerulonephropathy, and two of serum anti-GBM antibody without typical anti-GBM disease) were identified early, responded to conventional therapy (where needed), and had favorable outcomes. Three of 11 cases outside the CDP occurred following off-label alemtuzumab use prior to approval for RRMS and were all anti-GBM disease. Diagnosis was delayed in one of these three cases and another did not receive appropriate treatment; all three cases resulted in end-stage renal failure. All anti-GBM disease cases with documented urinalysis demonstrated prior microscopic hematuria.

Conclusion:

Close monitoring of alemtuzumab-treated MS patients facilitates diagnosis and treatment early in the nephropathy course when preservation of renal function is more likely.

Specific Donor HLA-DR Types Correlate With Altered Susceptibility to Development of Chronic Lung Allograft Dysfunction

BACKGROUND

The greatest challenge to long-term graft survival is the development of chronic lung allograft dysfunction. Th17 responses to collagen type V (colV) predispose lung transplant patients to the severe obstructive form of chronic lung allograft dysfunction, known as bronchiolitis obliterans syndrome (BOS). In a previous study cohort (n = 54), pretransplant colV responses were increased in recipients expressing HLA-DR15, consistent with the high binding avidity of colV (α1) peptides for HLA-DR15, whereas BOS incidence, which was known to be strongly associated with posttransplant autoimmunity to colV, was higher in patients who themselves lacked HLA-DR15, but whose lung donor expressed it.

METHODS

To determine if this DR-restricted effect on BOS incidence could be validated in a larger cohort, we performed a retrospective analysis of outcomes for 351 lung transplant recipients transplanted between 1988 and 2008 at the University of Wisconsin. All subjects were followed until graft loss, death, loss to follow-up, or through 2014, with an average follow-up of 7 years. Comparisons were made between recipients who did or did not develop BOS. Grading of BOS followed the recommendations of the international society for heart and lung transplantation.

RESULTS

Donor HLA-DR15 was indeed associated with increased susceptibility to severe BOS in this population. We also discovered that HLA-DR7 expression by the donor or HLA-DR17 expression by the recipient decreased susceptibility.

CONCLUSIONS

We show in this retrospective study that specific donor HLA class II types are important in lung transplantation, because they are associated with either protection from or susceptibility to development of severe BOS.

Role of regulatory T cells in experimental autoimmune glomerulonephritis

Anti-glomerular basement membrane (anti-GBM) disease is characterized by antibodies and T cells directed against the Goodpasture antigen, the noncollagenous domain of the α3-chain of type IV collagen [α3(IV)NC1] of the GBM. Consequences are the deposition of autoantibodies along the GBM and the development of crescentic glomerulonephritis (GN) with rapid loss of renal function. Forkhead box protein P3 (Foxp3)⁺ regulatory T (Treg) cells are crucial for the maintenance of peripheral tolerance to self-antigens and the prevention of immunopathology. Here, we use the mouse model of experimental autoimmune GN to characterize the role of Treg cells in anti-GBM disease. Immunization of DBA/1 mice with α3(IV)NC1 induced the formation of α3(IV)NC1-specific T cells and antibodies and, after 8-10 wk, the development of crescentic GN. Immunization resulted in increased frequencies of peripheral Treg cells and renal accumulation of these cells in the stage of acute GN. Depletion of Treg cells during immunization led to enhanced generation of α3(IV)NC1-specific antibodies and T cells and to aggravated GN. In contrast, depletion or expansion of the Treg cell population in mice with established autoimmunity had only minor consequences for renal inflammation and did not alter the severity of GN. In conclusion, our results indicate that in anti-GBM disease, Treg cells restrict the induction of autoimmunity against α3(IV)NC1. However, Treg cells are inefficient in preventing crescentic GN after autoimmunity has been established.

A meta-analysis of association of Human Leukocyte Antigens A, B, C, DR and DQ with Human Papillomavirus 16 infection

Human Papillomavirus (HPV) induced cervical cancer (CaCx) is a major health problem in women from both developing and developed regions of the world. This virus accounts for >95% of the CaCx cases with a preponderance of HPV type -16 (65%). Paradoxically HPV-16 is prevalent even in the cervix of healthier women and anti HPV-16 T-cell response is considered critical for the viral clearance. Studies on HLA association with HPV-16 infection and cervical cancer have yielded varied HLA associations in different epidemiological settings. To validate these associations, we performed a meta-analysis of HLA-A, B, C, DR and DQ association with HPV-16 infection. Of the 1409 studies retrieved, 26 qualified for meta-analysis based on stringent inclusion and exclusion criteria. HLA-B*47, B*57, DRB1*10, DRB1*15 and DQB1*0303 were significantly associated with HPV-16 infection (OR = 3.4, 1.8, 1.5, 1.1 and 1.5 respectively). HLA-B*49, B*39, A28 (serotype), C*04 and DRB1*13 were negatively associated with HPV-16 (OR = 0.5, 0.6, 0.7, 0.7, and 0.7 respectively). Certain HLA alleles such as B*07, DRB1*15, DRB1*11 and DRB1*07 showed weakly positive associations. A comprehensive analysis coupling HPV-16 antigenic diversity and the HLA variation in various global populations shall provide further insights into the immunogenetic predisposition to HPV-16 and shall help identify host-parasite co-evolution.

Antigen-Specificity in the Thymic Development and Peripheral Activity of CD4+FOXP3+ T Regulatory Cells

CD4⁺Foxp3⁺ T regulatory cells (Treg) are essential for the life of the organism, in particular because they protect the host against its own autoaggressive CD4⁺Foxp3^- T lymphocytes (Tconv). Treg distinctively suppress autoaggressive immunity while permitting efficient defense against infectious diseases. This split effect indicates that Treg activity is controlled in an antigen-specific manner. This specificity is achieved first by the formation of the Treg repertoire during their development, and second by their activation in the periphery. This review presents novel information on the antigen-specificity of Treg development in the thymus, and Treg function in the periphery. These aspects have so far remained imprecisely understood due to the lack of knowledge of the actual antigens recognized by Treg during the different steps of their life, so that most previous studies have been performed using artificial antigens. However, recent studies identified some antigens mediating the positive selection of autoreactive Treg in the thymus, and the function of Treg in the periphery in autoimmune and allergic disorders. These investigations emphasized the remarkable specificity of Treg development and function. Indeed, the development of autoreactive Treg in the thymus was found to be mediated by single autoantigens, so that the absence of one antigen led to a dramatic loss of Treg reacting toward that antigen. The specificity of Treg development is important because the constitution of the Treg repertoire, and especially the presence of holes in this repertoire, was found to crucially influence human immunopathology. Indeed, it was found that the development of human immunopathology was permitted by the lack of Treg against the antigens driving the autoimmune or allergic T cell responses rather than by the impairment of Treg activation or function. The specificity of Treg suppression in the periphery is therefore intimately associated with the mechanisms shaping the formation of the Treg repertoire during their development. This novel information refines significantly our understanding of the antigen-specificity of Treg protective function, which is required to envision how these cells distinctively regulate unwanted immune responses as well as for the development of appropriate approaches to optimally harness them therapeutically in autoimmune, malignant, and infectious diseases.

Management of adverse renal events related to alemtuzumab treatment in multiple sclerosis: a Belgian consensus

Alemtuzumab is a humanized monoclonal antibody indicated for the treatment of adult patients with relapsing–remitting multiple sclerosis with active disease. Multiple sclerosis (MS) patients treated with alemtuzumab are at increased risk for autoimmune adverse events (thyroid disorders, immune thrombocytopenia, and renal disease). The use of alemtuzumab has been associated with the development of renal immune-mediated adverse events in 0.3% of patients in clinical trials in MS, which generally occurred within 39 months of the last administration. Both anti-GBM disease and membranous nephropathy have been associated with the use of alemtuzumab. Early detection is necessary to allow for early diagnosis and prevent adverse renal and patient outcomes. Through the implementation of the risk minimization measures, patients can be diagnosed, and treated if needed, early allowing for generally favorable outcomes. This important goal can be reached through health care professional and patient education, careful analysis of the monthly lab tests, and close collaboration between the patient, neurologist, and the nephrologist. This article presents the consensus of Belgian MS specialists and nephrologists on the practicalities of diagnosis, management, and treatment of alemtuzumab-associated renal adverse events based on good clinical practice.

Goodpasture's disease in a patient with advanced lung cancer treated with nivolumab: An autopsy case report

Nivolumab, an anti-programmed death-1 immune checkpoint inhibitor (ICI), is now widely used to treat numerous cancers. Although most adverse effects related to ICIs are controllable, fulminant immune-related adverse events can occur. A 74-year-old patient with non-small-cell lung cancer was treated with nivolumab as a second-line treatment. After 8 cycles, acute kidney injury with macroscopic hematuria appeared, followed by diffuse ground-glass opacities with hemoptysis. Since the clinical course suggested Goodpasture's disease, methylprednisolone pulse therapy and plasma exchange were started. Later, it was confirmed that the serum anti-glomerular basement membrane antibody was positive. However, the patient died 35 days after admission due to respiratory failure, and an autopsy showed crescentic glomerulonephritis and massive alveolar hemorrhage which were compatible with Goodpasture's disease. Our case provides a possible link between nivolumab and lethal Goodpasture's disease.

Urinary podocyte and TGF-β1 mRNA as markers for disease activity and progression in anti-glomerular basement membrane nephritis

Background

Podocyte depletion causes glomerulosclerosis, with persistent podocyte loss being a major factor driving disease progression. Urinary podocyte mRNA is potentially useful for monitoring disease progression in both animal models and in humans. To determine whether the same principles apply to crescentic glomerular injury, a rat model of anti-glomerular basement membrane (anti-GBM) nephritis was studied in parallel with a patient with anti-GBM nephritis.

Methods

Podocyte loss was measured by Wilms' Tumor 1-positive podocyte nuclear counting and density, glomerular epithelial protein 1 or synaptopodin-positive podocyte tuft area and urinary podocyte mRNA excretion rate. Glomerulosclerosis was evaluated by Azan staining and urinary transforming growth factor (TGF)-β1 mRNA excretion rate.

Results

In the rat model, sequential kidney biopsies revealed that after a threshold of 30% podocyte loss, the degree of glomerulosclerosis was linearly associated with the degree of podocyte depletion, compatible with podocyte depletion driving the sclerotic process. Urinary podocyte mRNA correlated with the rate of glomerular podocyte loss. In treatment studies, steroids prevented glomerulosclerosis in the anti-GBM model in contrast to angiotensin II inhibition, which lacked a protective effect, and urinary podocyte and TGF-β1 mRNA markers more accurately reflected both the amount of podocyte depletion and the degree of glomerulosclerosis compared with proteinuria under both scenarios. In a patient successfully treated for anti-GBM nephritis, urinary podocyte and TGB-β1 mRNA reflected treatment efficacy.

Conclusion

These results emphasize the role of podocyte depletion in anti-GBM nephritis and suggest that urinary podocyte and TGF-β1 mRNA could serve as markers of disease progression and treatment efficacy.

Goodpasture's autoimmune disease - A collagen IV disorder

Goodpasture's (GP) disease is an autoimmune disorder characterized by the deposition of pathogenic autoantibodies in basement membranes of kidney and lung eliciting rapidly progressive glomerulonephritis and pulmonary hemorrhage. The principal autoantigen is the α345 network of collagen IV, which expression is restricted to target tissues. Recent discoveries include a key role of chloride and bromide for network assembly, a novel posttranslational modification of the antigen, a sulfilimine bond that crosslinks the antigen, and the mechanistic role of HLA in genetic susceptibility and resistance to GP disease. These advances provide further insights into molecular mechanisms of initiation and progression of GP disease and serve as a basis for developing of novel diagnostic tools and therapies for treatment of Goodpasture's disease.

Regulatory T cells in renal disease

The kidney is vulnerable to injury, both acute and chronic from a variety of immune and metabolic insults, all of which at least to some degree involve inflammation. Regulatory T cells modulate systemic autoimmune and allogenic responses in glomerulonephritis and transplantation. Intrarenal regulatory T cells (Tregs), including those recruited to the kidney, have suppressive effects on both adaptive and innate immune cells, and probably also intrinsic kidney cells. Evidence from autoimmune glomerulonephritis implicates antigen-specific Tregs in HLA-mediated dominant protection, while in several human renal diseases Tregs are abnormal in number or phenotype. Experimentally, Tregs can protect the kidney from injury in a variety of renal diseases. Mechanisms of Treg recruitment to the kidney include via the chemokine receptors CCR6 and CXCR3 and potentially, at least in innate injury TLR9. The effects of Tregs may be context dependent, with evidence for roles for immunoregulatory roles both for endogenous Tbet-expressing Tregs and STAT-3-expressing Tregs in experimental glomerulonephritis. Most experimental work and some of the ongoing human trials in renal transplantation have focussed on unfractionated thymically derived Tregs (tTregs). However, induced Tregs (iTregs), type 1 regulatory T (Tr1) cells and in particular antigen-specific Tregs also have therapeutic potential not only in renal transplantation, but also in other kidney diseases.

Plasticity and heterogeneity of Th17 in immune-mediated kidney diseases

Anti-neutrophil cytoplasmatic antibody (ANCA)-associated glomerulonephritis, anti-glomerular basement membrane (GBM) glomerulonephritis and lupus nephritis are the most common causes of rapid progressive glomerulonephritis (RPGN) in the Western world. These aggressive forms of autoimmune kidney diseases significantly contribute to end-stage renal disease and are associated with high morbidity and mortality. Moreover, patients show significant heterogeneity with respect to clinical outcome and response to therapy. T cell infiltration is a morphological hallmark of RPGN and it is a critical driver of kidney injury. Different CD4⁺ T cell subsets that are endowed with distinct regulatory and effector functions are involved in this detrimental inflammatory process. In particular, the identification and functional characterization of IL-17-expressing CD4⁺ Th17 cells have substantially advanced our understanding of organ-specific autoimmunity. In experimental models of crescentic and proliferative GN, including ANCA-associated GN, anti-GBM-GN and lupus nephritis, the Th17/IL-17 axis significantly contributes to renal tissue damage. In patients with ANCA-associated GN or lupus nephritis, IL-17 serum levels correlated with disease activity. Moreover, Th17 cells are present in the kidneys of these patients and represents a topic of intense ongoing clinical and basic research. Importantly, recent studies have challenged the view of CD4⁺ T cells subsets as terminally differentiated homogenous cells, showing that T cells, in particular Th17 cells, are much more flexible and heterogeneous than previously thought. However, analysis of Th17 cell fate in mouse models of autoimmune kidney disease revealed a high degree of stability within these cells, an observation that is in contrast to Th17 cells in other models of autoimmune diseases including experimental autoimmune encephalomyelitis. Interestingly, anti-CD3 treatment interferes with stable Th17 cells and induces a potential regulatory phenotype in Th17 cells, highlighting the therapeutic potential of targeting pathogenic Th17 cells in autoimmunity. In this review, we discuss the current knowledge of Th17 cell plasticity and heterogeneity in autoimmune kidney diseases with a special focus on the underlying mechanisms of this process and debate if Th17 cell plasticity is beneficial or harmful to renal inflammation.

The Role of Fungi in the Etiology of Multiple Sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disorder of the central nervous system. Infectious triggers of MS are being actively investigated. Substantial evidence supports the involvement of the Epstein-Barr virus (EBV), though other viruses, bacteria, protists, and fungi are also being considered. Many links between fungi and diseases involving chronic inflammation have been found recently. Evidence linking MS and fungi is reviewed here. The HLA-DRB1*15 allele group is the most important genetic risk factor of MS, and is a risk factor in several other conditions linked to fungal infections. Many biomarkers of MS are consistent with fungal infections, such as IL-17, chitotriosidase, and antibodies against fungi. Dimethyl fumarate (DMF), first used as an industrial fungicide, was recently repurposed to reduce MS symptoms. Its mechanisms of action in MS have not been firmly established. The low risk of MS during childhood and its moderate association with herpes simplex virus type 2 suggest genital exposure to microbes (including fungi) should be investigated as a possible trigger. Molecular and epidemiological evidence support a role for infections such as EBV in MS. Though fungal infections have not been widely studied in MS, many lines of evidence are consistent with a fungal etiology. Future microbiome and serological studies should consider fungi as a possible risk factor for MS, and future clinical studies should consider the effect of fungicides other than DMF on MS symptoms.

A murine Ig light chain transgene reveals IGKV3 gene contributions to anti-collagen types IV and II specificities

A subset of autoimmune diseases result from autoantibodies targeting epitopes on matrix collagen. The most extensively studied are anti-glomerular basement membrane glomerulonephritis (or its systemic counterpart Goodpasture's disease) that destroys kidneys and lungs, and rheumatoid arthritis that leads to disabling arthritis. Autoantibodies in these disorders bind evolutionarily conserved conformational epitopes on the noncollagenous domain 1 (NC1) of the alpha3 chain of type IV [alpha3(IV)NC1] collagen in glomerular and alveolar basement membranes, and on native or citrullinated type II collagen (CII) in joint cartilage, respectively. The genetic origins of pathogenic anti-collagen B cells in these diseases is unknown, but observations from murine models raise the possibility that they overlap despite distinct in vivo immunopathologies. Monoclonal autoantibodies isolated from mice immunized with alpha3(IV)NC1 collagen or CII show a biased use of Ig light chains (LC) encoded by genes of the IGKV3 subgroup (previously Vk21 family), paired with diverse Ig heavy chains. To further explore this relationship and determine if a single murine IGKV3 LC independently predisposes to both anti-collagen responses, we generated a novel transgenic (Tg) C57BL/6 mouse that expresses a productively rearranged IGKV3-encoded LC, termed mLCV3-Tg, in conjunction with endogenously rearranged Ig heavy chains. Tg mice are also genetically deficient in endogenous kappa chains to permit tracking of the mLCV3 transgene. We show that mLCV3-Tg mice are susceptible to humoral autoimmunity against both collagen chains. Anti-alpha3(IV)NC1 collagen, but not anti-CII, mLCV3-encoded Ig are detected in serum of unmanipulated Tg mice, while Toll-like receptor ligands induce secretion of mLCV3-Tg autoantibodies of both collagen specificities from splenocytes ex vivo. This indicates developmental survival of mLCV3-Tg B cells reactive with each antigen, and is consistent with production of the two anti-collagen autoIg from distinct B cell populations. Reduced B cell numbers, low serum Ig kappa levels, low cell surface Ig kappa density, and abundant endogenous lambda chain expression suggest that subsets of IGKV3-encoded B cells are regulated in vivo by mechanisms that include deletion, anergy, and LC editing. These results support the notion that murine IGKV3 LCs contribute structural fitness to antigen binding sites that support diverse anti-collagen autoimmune responses, that these responses are regulated in vivo, and that these cells can nonetheless readily escape immune regulation.

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.

The susceptible HLA class II alleles and their presenting epitope(s) in Goodpasture's disease

Goodpasture's disease is closely associated with HLA, particularly DRB1*1501. Other susceptible or protective HLA alleles are not clearly elucidated. The presentation models of epitopes by susceptible HLA alleles are also unclear. We genotyped 140 Chinese patients and 599 controls for four-digit HLA II genes, and extracted the encoding sequences from the IMGT/HLA database. T-cell epitopes of α3(IV)NC1 were predicted and the structures of DR molecule-peptide-T-cell receptor were constructed. We confirmed DRB1*1501 (OR = 4·6, P = 5·7 × 10^-28 ) to be a risk allele for Goodpasture's disease. Arginine at position 13 (ARG13) (OR = 4·0, P = 1·0 × 10^-17 ) and proline at position 11 (PRO11) (OR = 4·0, P = 2·0 × 10^-17 ) on DRβ1, encoded by DRB1*1501, were associated with disease susceptibility. α_134-148 (HGWISLWKGFSFIMF) was predicted as a T-cell epitope presented by DRB1*1501. Isoleucine₁₃₇ , tryptophan₁₄₀ , glycine₁₄₂ , phenylalanine₁₄₃ and phenylalanine₁₄₅ , were presented in peptide-binding pockets 1, 4, 6, 7 and 9 of DR2b, respectively. ARG13 in pocket 4 interacts with tryptophan₁₄₀ and forms a hydrogen bond. In conclusion, we propose a mechanism for DRB1*1501 susceptibility for Goodpasture's disease through encoding ARG13 and PRO11 on MHC-DRβ1 chain and presenting T-cell epitope, α_134-148 , with five critical residues.

Dominant protection from HLA-linked autoimmunity by antigen-specific regulatory T cells

Susceptibility and protection against human autoimmune diseases, including type I diabetes, multiple sclerosis, and Goodpasture disease, is associated with particular human leukocyte antigen (HLA) alleles. However, the mechanisms underpinning such HLA-mediated effects on self-tolerance remain unclear. Here we investigate the molecular mechanism of Goodpasture disease, an HLA-linked autoimmune renal disorder characterized by an immunodominant CD4⁺ T-cell self-epitope derived from the α3 chain of type IV collagen (α3_135-145). While HLA-DR15 confers a markedly increased disease risk, the protective HLA-DR1 allele is dominantly protective in trans with HLA-DR15 (ref. 2). We show that autoreactive α3_135-145-specific T cells expand in patients with Goodpasture disease and, in α3_135-145-immunized HLA-DR15 transgenic mice, α3_135-145-specific T cells infiltrate the kidney and mice develop Goodpasture disease. HLA-DR15 and HLA-DR1 exhibit distinct peptide repertoires and binding preferences and present the α3_135-145 epitope in different binding registers. HLA-DR15-α3_135-145 tetramer⁺ T cells in HLA-DR15 transgenic mice exhibit a conventional T-cell phenotype (T_conv) that secretes pro-inflammatory cytokines. In contrast, HLA-DR1-α3_135-145 tetramer⁺ T cells in HLA-DR1 and HLA-DR15/DR1 transgenic mice are predominantly CD4⁺Foxp3⁺ regulatory T cells (T_reg cells) expressing tolerogenic cytokines. HLA-DR1-induced T_reg cells confer resistance to disease in HLA-DR15/DR1 transgenic mice. HLA-DR15⁺ and HLA-DR1⁺ healthy human donors display altered α3_135-145-specific T-cell antigen receptor usage, HLA-DR15-α3_135-145 tetramer⁺ Foxp3^- T_conv and HLA-DR1-α3_135-145 tetramer⁺ Foxp3⁺CD25^hiCD127^lo T_reg dominant phenotypes. Moreover, patients with Goodpasture disease display a clonally expanded α3_135-145-specific CD4⁺ T-cell repertoire. Accordingly, we provide a mechanistic basis for the dominantly protective effect of HLA in autoimmune disease, whereby HLA polymorphism shapes the relative abundance of self-epitope specific T_reg cells that leads to protection or causation of autoimmunity.

Plasma from patients with anti-glomerular basement membrane disease could recognize microbial peptides

Infection has long been suspected as a trigger of autoimmune diseases, and molecular mimicry mechanism was hypothesized in this study. Microbe originated peptides were searched from the Uniprot database based on a previous defined critical amino acid motif within α3_129−150, isoleucine137, tryptophan140, glycine142, phenylalanine 143 and phenylalanine 145. 23826 microbial peptides were identified using our searching strategy, among which seven were related with human infections. Circulating IgG and IgM antibodies against the seven microbial peptides were detected using ELISA in 76 patients with anti-GBM disease. Four peptides were recognized by both IgG and IgM antibodies, and one peptide was recognized by IgG antibodies only. Peptides from Bacteroides, Saccharomyces cerevisiae, and Bifidobacterium thermophilum possessed the highest recognition frequency with the prevalence of 73.7%, 61.8% and 67.1% for IgG, 56.6%, 44.7% and 67.1% for IgM in anti-GBM patients. Patients with antibodies against these microbial peptides showed more severe kidney injury, including higher serum creatinine and higher percentage of crescent formation. In conclusion, antibodies against microbial peptides were identified in the circulation of anti-GBM patients, implying its etiological role in eliciting autoimmune response against α3(IV)NC1 through molecular mimicry.

Clinicopathological characteristics of typical and atypical anti-glomerular basement membrane nephritis

Anti-glomerular basement membrane (GBM) antibody disease is a rare pathological condition that mainly involves renal and/or pulmonary parenchyma. It is characterized by the presence of circulating anti-GBM antibodies accompanied by a linear deposition of immunoglobulins (Ig) detected through immunofluorescence (IF) technique and typical signs and symptoms of organ dysfunction, such as rapidly progressive glomerulonephritis (RPGN) and pulmonary hemorrhage (PH). However, recently atypical forms of anti-GBM disease have been described and the presence of overlapping diseases contributed to make its diagnosis challenging. In this review will be discussed the entire spectrum of renal anti-GBM related conditions, focusing the attention on the differences in terms of pathogenesis, diagnosis and therapy of these disparate entities.

The pathogenicity of T cell epitopes on human Goodpasture antigen and its critical amino acid motif

Goodpasture antigen, the non‐collagenous domain of α3 chain of type IV collagen [α3(IV)NC1], is the target antigen of anti‐glomerular basement membrane (GBM) antibodies. The pathogenicity of T cell epitopes is not elucidated clearly. In this study, we aim to define the nephritogenic T cell epitopes and its critical amino acid residues. Twenty‐four overlapping linear peptides were synthesized covering the whole sequence of human α3(IV)NC1. Wistar–Kyoto rats were immunized with linear peptides, and experimental autoimmune glomerulonephritis was evaluated. Critical amino acid was identified by the loss of nephritogenic function after each amino acid substitution by alanine. Of the 24 peptides, P14 (α3_127‐148) could induce 90.5% (19/21) of WKY rats developing anti‐GBM glomerulonephritis with proteinuria, elevated serum urea and creatinine, IgG linear deposit on GBM and substantial (in average 82.4 ± 5.6%) crescent formation in glomeruli. Lymphocytes of immunized rats proliferated in response to α3_127‐148 and α3(IV)NC1 in vitro. Sera of these rats recognized α3_127‐148 and later on together with intact human α3(IV)NC1. Antibodies towards α3_127‐148 and intact α3(IV)NC1 could also be detected from the kidney elutes. These antibodies showed no cross‐reaction with each other, which implies intramolecular epitope spreading during disease progress. After sequential amino acid substitution, the α3_127‐148 with substitution of tryptophan₁₃₆, isoleucine₁₃₇, leucine₁₃₉ or tryptophan₁₄₀ lost its nephritogenicity. Human α3_127‐148 is a nephritogenic T cell epitope in WKY rats, with the critical amino acids as W₁₃₆I₁₃₇xL₁₃₉W₁₄₀. These findings might facilitate future investigation on microbial aetiology and potential specific immunotherapy of anti‐GBM disease.

Basement membranes and autoimmune diseases

Basement membrane components are targets of autoimmune attack in diverse diseases that destroy kidneys, lungs, skin, mucous membranes, joints, and other organs in man. Epitopes on collagen and laminin, in particular, are targeted by autoantibodies and T cells in anti-glomerular basement membrane glomerulonephritis, Goodpasture's disease, rheumatoid arthritis, post-lung transplant bronchiolitis obliterans syndrome, and multiple autoimmune dermatoses. This review examines major diseases linked to basement membrane autoreactivity, with a focus on investigations in patients and animal models that advance our understanding of disease pathogenesis. Autoimmunity to glomerular basement membrane type IV is discussed in depth as a prototypic organ-specific autoimmune disease yielding novel insights into the complexity of anti-basement membrane immunity and the roles of genetic and environmental susceptibility.

Optimizing the translational value of animal models of glomerulonephritis: insights from recent murine prototypes

Animal models are indispensable for the study of glomerulonephritis, a group of diseases that destroy kidneys but for which specific therapies do not yet exist. Novel interventions are urgently needed, but their rational design requires suitable in vivo platforms to identify and test new candidates. Animal models can recreate the complex immunologic microenvironments that foster human autoimmunity and nephritis and provide access to tissue compartments not readily examined in patients. Study of rat Heymann nephritis identified fundamental disease mechanisms that ultimately revolutionized our understanding of human membranous nephropathy. Significant species differences in expression of a major target antigen, however, and lack of spontaneous autoimmunity in animals remain roadblocks to full exploitation of preclinical models in this disease. For several glomerulonephritides, humanized models have been developed to circumvent cross-species barriers and to study the effects of human genetic risk variants. Herein we review humanized mouse prototypes that provide fresh insight into mediators of IgA nephropathy and origins of antiglomerular basement membrane nephritis and Goodpasture's disease, as well as a means to test novel therapies for ANCA vasculitis. Additional and refined model systems are needed to mirror the full spectrum of human disease in a genetically diverse population, to facilitate development of patient-specific interventions, to determine the origin of nephritogenic autoimmunity, and to define the role of environmental exposures in disease initiation and relapse.

T cell infiltration is associated with kidney injury in patients with anti-glomerular basement membrane disease

Cell-mediated autoimmunity, particularly that involving autoreactive T cells, participates in mediating anti-glomerular basement membrane (GBM) disease. However, direct kidney injury mediated by renal infiltrated T cells has not been clearly elucidated in humans. The T cell profile (CD3, CD4, CD8, IL-17, and foxp3) and macrophage (CD68) were examined by immunohistochemistry on renal biopsy tissues from 13 patients with anti-GBM disease. The correlation between cell infiltration and clinical data was also analyzed. We found that the distribution of T cell infiltration was predominant in the peri-glomerular and interstitial areas. CD³⁺ T cell infiltratrion around the glomeruli with cellular crescent formations was significantly higher than that around the glomeruli with mild mesangial proliferation. CD⁸⁺ T cells significantly accumulated around the glomeruli with cellular crescents without IgG deposits compared to those with IgG deposits. The prevalence of infiltrating CD⁸⁺ T cells was correlated with the percentage of ruptured Bowman's capsules. In conclusion, cellular immunity may play a crucial role in the inflammatory kidney injury in anti-GBM patients. The periglomerular infiltration of T cells, especially CD⁸⁺ T cells, may participate in the pathogenic mechanism of glomerular damage.