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In antineutrophil cytoplasmic autoantibody (ANCA)-associated vasculitides (AAV), the two major target antigens of ANCA are proteinase 3 (PR3) and myeloperoxidase (MPO). Evidence is accumulating that there are distinct differences between patients with PR3-AAV and those with MPO-AAV. In the present study, the clinicopathological features and prognosis of patients with PR3-AAV and MPO-AAV from a single center in China were retrospectively analyzed. A total of 212 Chinese patients with AAV were recruited in the present study; 189/212 (89.15%) patients were classified as having MPO-AAV and 23/212 (10.85%) patients as having PR3-AAV. Compared with those in the PR3-AAV group, patients in the MPO-AAV group were older and less frequently had ear, nose and throat or ophthalmic involvement. MPO-AAV patients had higher levels of serum creatinine and proteinuria at baseline. No significant difference was observed with regard to the pathological changes of the glomeruli and tubulointerstitium between the two groups. The probability of developing end-stage renal disease was significantly higher in patients with MPO-AAV compared with that in patients with PR3-AAV. There was no significant difference in the one-year patient survival rate between the two groups. However, differences in certain clinical characteristics and outcomes were observed between MPO-AAV and PR3-AAV patients. A large national investigation of AAV is required to confirm the concept that PR3-AAV and MPO-AAV are distinct disease entities.Copyright © 2021 Spandidos Publications. All rights reserved.

Background Myeloperoxidase ANCA-associated vasculitis is a major cause of ESKD. Efficacy of anti-CD20 mAb treatment was tested in a mouse model of the disease. Methods MPO immunization induced anti-MPO autoimmunity, and a subnephritogenic dose of sheep anti-mouse GBM globulin triggered GN. Results Anti-CD20 mAb treatment increased the numbers and immunomodulatory capacity of MPO-specific T regulatory cells (Tregs) and attenuated T cell-mediated and humoral anti-MPO autoimmunity and GN. Disabling of Tregs negated the therapeutic benefit of anti-CD20 treatment. The mechanism of enhancement of Treg activity could be attributed to anti-CD20 mAb effects on inducing B cell apoptosis. Administering anti-CD20 mAb-induced apoptotic splenocytes to mice developing anti-MPO GN was as effective as anti-CD20 mAb treatment in inducing Tregs and attenuating both anti-MPO autoimmunity and GN. A nonredundant role for splenic macrophages in mediating the anti-CD20 mAb-induced immunomodulation was demonstrated by showing that administration of anti-CD20 mAb ex vivo-induced apoptotic splenocytes to unmanipulated mice attenuated autoimmunity and GN, whereas deletion of splenic marginal zone macrophages prevented anti-CD20 mAb-induced immunomodulation and treatment efficacy. Six days after administering anti-CD20 mAb to mice with murine anti-MPO GN, cell-mediated anti-MPO responses and GN were attenuated, and Tregs were enhanced, but ANCA levels were unchanged, suggesting humoral autoimmunity was redundant at this time point. Conclusions Collectively, these data suggest that, as well as reducing humoral autoimmunity, anti-CD20 mAb more rapidly induces protective anti-MPO Treg-mediated immunomodulation by splenic processing of anti-CD20-induced apoptotic B cells.Copyright © 2021 by the American Society of Nephrology

BACKGROUND: Myeloperoxidase ANCA-associated vasculitis is a major cause of ESKD. Efficacy of anti-CD20 mAb treatment was tested in a mouse model of the disease. METHOD(S): MPO immunization induced anti-MPO autoimmunity, and a subnephritogenic dose of sheep anti-mouse GBM globulin triggered GN. RESULT(S): Anti-CD20 mAb treatment increased the numbers and immunomodulatory capacity of MPO-specific T regulatory cells (Tregs) and attenuated T cell-mediated and humoral anti-MPO autoimmunity and GN. Disabling of Tregs negated the therapeutic benefit of anti-CD20 treatment. The mechanism of enhancement of Treg activity could be attributed to anti-CD20 mAb effects on inducing B cell apoptosis. Administering anti-CD20 mAb-induced apoptotic splenocytes to mice developing anti-MPO GN was as effective as anti-CD20 mAb treatment in inducing Tregs and attenuating both anti-MPO autoimmunity and GN. A nonredundant role for splenic macrophages in mediating the anti-CD20 mAb-induced immunomodulation was demonstrated by showing that administration of anti-CD20 mAb ex vivo-induced apoptotic splenocytes to unmanipulated mice attenuated autoimmunity and GN, whereas deletion of splenic marginal zone macrophages prevented anti-CD20 mAb-induced immunomodulation and treatment efficacy. Six days after administering anti-CD20 mAb to mice with murine anti-MPO GN, cell-mediated anti-MPO responses and GN were attenuated, and Tregs were enhanced, but ANCA levels were unchanged, suggesting humoral autoimmunity was redundant at this time point. CONCLUSION(S): Collectively, these data suggest that, as well as reducing humoral autoimmunity, anti-CD20 mAb more rapidly induces protective anti-MPO Treg-mediated immunomodulation by splenic processing of anti-CD20-induced apoptotic B cells.Copyright © 2021 by the American Society of Nephrology.

Data on anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) are limited in children. This study is to determine the clinical features and outcomes of childhood-onset AAV. A retrospective study was performed on patients who were diagnosed with AAV before 18 years old in Xiangya Hospital. Their medical records were analyzed by retrospective review. Sixteen patients were diagnosed with AAV before 18 years old in the past 9 years, with an average age of 13.3 +/- 3.3 years and 13 of them were female. There were 15 patients with microscopic polyangiitis (MPA) and 1 with Wegener's granulomatosis. The interval between onset of disease and diagnosis of AAV was 2 (1.5-3) months. Most patients (15/16, 93.8%) had multi-organ involvement, and all patients had renal involvement with 7 (43.8%) patients requiring dialysis at presentation. Eleven patients underwent a renal biopsy, of which mixed class and sclerotic class were the most two common histological types. All patients received immunosuppressive therapy for induction therapy including intravenous administrations of methylprednisolone (MP) pulse therapy for 8 patients. 8 patients (50%) achieved remission after induction therapy. After a median follow-up of 46.3 +/- 36.1 months, nine (56.3%) patients progressed to end-stage renal disease (ESRD) and 5 (31.3%) patients died. Childhood-onset AAV showed similar clinical and pathological features compared to those of adults, except that it usually occurs in girls. The most commonly involved organ was the kidney, and it had a high risk of progression to ESRD. Early diagnosis and initiation of appropriate immunomodulatory therapy would be important to improve outcomes.Copyright © 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG.

BACKGROUND: Since 2019, a novel coronavirus named 2019 novel coronavirus (2019-nCoV) has emerged worldwide. Apart from fever and respiratory complications, acute kidney injury has been observed in a few patients with coronavirus disease 2019. Furthermore, according to recent findings, the virus has been detected in urine. Angiotensin-converting enzyme II (ACE2) has been proposed to serve as the receptor for the entry of 2019-nCoV, which is the same as that for the severe acute respiratory syndrome. This study aimed to investigate the possible cause of kidney damage and the potential route of 2019-nCoV infection in the urinary system. METHOD(S): We used both published kidney and bladder cell atlas data and new independent kidney single-cell RNA sequencing data generated in-house to evaluate ACE2 gene expression in all cell types in healthy kidneys and bladders. The Pearson correlation coefficients between ACE2 and all other genes were first generated. Then, genes with r values larger than 0.1 and P values smaller than 0.01 were deemed significant co-expression genes with ACE2. RESULT(S): Our results showed the enriched expression of ACE2 in all subtypes of proximal tubule (PT) cells of the kidney. ACE2 expression was found in 5.12%, 5.80%, and 14.38% of the proximal convoluted tubule cells, PT cells, and proximal straight tubule cells, respectively, in three published kidney cell atlas datasets. In addition, ACE2 expression was also confirmed in 12.05%, 6.80%, and 10.20% of cells of the proximal convoluted tubule, PT, and proximal straight tubule, respectively, in our own two healthy kidney samples. For the analysis of public data from three bladder samples, ACE2 expression was low but detectable in bladder epithelial cells. Only 0.25% and 1.28% of intermediate cells and umbrella cells, respectively, had ACE2 expression. CONCLUSION(S): This study has provided bioinformatics evidence of the potential route of 2019-nCoV infection in the urinary system.Copyright © 2021

Idiopathic membranous nephropathy (IMN) is an organ-specific autoimmune disease of the kidney glomerulus. It may gradually progress to end-stage renal disease (ESRD) characterized by increased proteinuria, which leads to serious consequences. Although substantial advances have been made in the understanding of the molecular bases of IMN in the last 10 years, certain questions remain largely unanswered. To define the transcriptomic landscape at single-cell resolution, we analyzed kidney samples from 6 patients with anti-PLA2R positive IMN and 2 healthy control subjects using single-cell RNA sequencing. We then identified distinct cell clusters through unsupervised clustering analysis of kidney specimens. Identification of the differentially expressed genes (DEGs) and enrichment analysis as well as the interaction between cells were also performed. Based on transcriptional expression patterns, we identified all previously described cell types in the kidney. The DEGs in most kidney parenchymal cells were primarily enriched in genes involved in the regulation of inflammation and immune response including IL-17 signaling, TNF signaling, NOD-like receptor signaling, and MAPK signaling. Moreover, cell-cell crosstalk highlighted the extensive communication of mesangial cells, which infers great importance in IMN. IMN with massive proteinuria displayed elevated expression of genes participating in inflammatory signaling pathways that may be involved in the pathogenesis of the progression of IMN. Overall, we applied single-cell RNA sequencing to IMN to uncover intercellular interactions, elucidate key pathways underlying the pathogenesis, and identify novel therapeutic targets of anti-PLA2R positive IMN.© Copyright © 2021 Xu, Shen, Lin, Meng, Ooi, Eggenhuizen, Tang, Xiao, Jin, Ding, Tang, Peng, Nie, Ao, Xiao, Zhong and Zhou.

Ovarian cancer, in particularly high-grade serous ovarian cancer (HGSOC) and ovarian carcinosarcoma (OCS), are highly aggressive and deadly female cancers with limited treatment options. These tumors are generally unresponsive to immune check-point inhibitor (ICI) therapy and are referred to as immunologically "cold" tumors. Cell-based therapy, in particular, adoptive T-cell therapy, is an alternative immunotherapy option that has shown great potential, especially chimeric antigen receptor T cell (CAR-T) therapy in the treatment of hematologic malignancies. However, the efficacy of CAR-T therapy in solid tumors has been modest. This review explores the potential of another cell-based therapy, T-cell receptor therapy (TCR-T) as an alternate treatment option for immunological "cold" OC and OCS tumors.© Copyright © 2021 Wu, Dand, Doig, Papenfuss, Scott, Ho and Ooi.

Chronic kidney disease (CKD) leads to significant morbidity and mortality worldwide. Glomerulonephritis (GN) is the second leading cause of CKD resulting in end stage renal failure. The most severe and rapidly progressive type of GN is characterized by glomerular crescent formation. The current therapies for crescentic GN, which consist of broad immunosuppressive drugs, are partially effective, non-specific, toxic and cause many serious side effects including infections, cancer, and cardiovascular problems. Therefore, new and safer therapies are needed. Human amniotic epithelial cells (hAECs) are a type of stem cell which are isolated from the placenta after birth. They represent an attractive and novel therapeutic option for the treatment of various inflammatory conditions owing to their unique and selective immunosuppressive ability, as well as their excellent safety profile and clinical applicability. In this review, we will discuss the immunopathogenesis of crescentic GN, issues with currently available treatments and how hAECs offer potential to become a new and harmless treatment option for this condition.© Copyright © 2021 Al Mushafi, Ooi and Odobasic.

Aim: To investigate the contribution of age to the development of anti-myeloperoxidase (MPO) autoimmunity and glomerulonephritis in murine models. Background(s): Autoimmunity to the neutrophil protein MPO results in anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) commonly causing glomerulonephritis. The incidence of AAV increases with age often resulting in worse prognosis and increased mortality. Previous work in aged mice using a passive transfer model of anti-MPO IgG induced glomerulonephritis has implicated innate effectors. However, the role of ageing on active anti-MPO autoimmunity and effector responses is unclear. Method(s): Young (2-3 months) and aged (15-22 months) mice were immunised with whole proteins or peptides from ovalbumin (a model foreign antigen) or MPO and autoimmunity assessed 10- and 35-days later. Anti-MPO glomerulonephritis was induced by immunising mice with MPO and glomerulonephritis was triggered by low dose anti-mouse basement membrane globulin. Disease was assessed 4 days later (day 21). Result(s): While cellular immunity to ovalbumin was diminished in aged mice, cellular autoimmunity to MPO and its immunodominant CD4+ and CD8+ epitopes was increased after immunisation with either whole MPO protein or peptides, assessed by peptide and antigen specific production of the pro-inflammatory cytokines interferon-gamma and interleukin-17A. Both OVA- and MPO-ANCA titres were decreased in aged mice compared with young mice 35 days after immunisation. Aged mice with anti-MPO glomerulonephritis developed more glomerular segmental lesions (young:30.2 +/- 4.9, aged:56.3 +/- 6.4% P < 0.004) and cell mediated injury (including IFN-gamma and TNF producing T cells), likely due to CD4+ and CD8+ T cells, innate immunity and the increased vulnerability of aged kidneys. Conclusion(s): Heightened cellular immunity to MPO develops with ageing in mice and may contribute to the increased incidence and severity of AAV in older people.

Epidemiological studies and clinical trials suggest Bacillus Calmette-Guerin (BCG) vaccine has protective effects against coronavirus disease 2019 (COVID-19). There are now over 30 clinical trials evaluating if BCG vaccination can prevent or reduce the severity of COVID-19. However, the mechanism by which BCG vaccination can induce severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific T cell responses is unknown. Here, we identify 8 novel BCG-derived peptides with significant sequence homology to either SARS-CoV-2 NSP3 or NSP13-derived peptides. Using an in vitro co-culture system, we show that human CD4+ and CD8+ T cells primed with a BCG-derived peptide developed enhanced reactivity to its corresponding homologous SARS-CoV-2-derived peptide. As expected, HLA differences between individuals meant that not all persons developed immunogenic responses to all 8 BCG-derived peptides. Nevertheless, all of the 20 individuals that were primed with BCG-derived peptides developed enhanced T cell reactivity to at least 7 of 8 SARS-CoV-2-derived peptides. These findings provide an in vitro mechanism that may account, in part, for the epidemiologic observation that BCG vaccination confers some protection from COVID-19.© Copyright © 2021 Eggenhuizen, Ng, Chang, Fell, Cheong, Wong, Gan, Holdsworth and Ooi.

Background: Antiglomerular basement membrane (anti-GBM) disease is associated with HLA-DRB1*1501 (the major predisposing genetic factor in the disease), with alpha3127-148 as a nephritogenic T and B cell epitope. Although the cause of disease remains unclear, the association of infections with anti-GBM disease hasbeenlong suspected. Method(s): To investigate whether microbesmight activate autoreactive T and B lymphocytes via molecular mimicry in anti-GBM disease, we used bioinformatic tools, including BLAST, SYFPEITHI, and ABCpred, for peptide searching and epitope prediction. We used sera from patients with anti-GBM disease to assess peptides recognized by antibodies, and immunized WKY rats and a humanized mouse model (HLA-DR15 transgenic mice) with each of the peptide candidates to assess pathogenicity. Result(s): Onthe basis of the criticalmotif, the bioinformatic approach identified 36 microbial peptides thatmimic human alpha3127-148. Circulating antibodies in sera from patients with anti-GBM recognized nine of them. One peptide, B7, derived from Actinomyces species, induced proteinuria, linear IgG deposition on the GBM, and crescent formation when injected into WKY rats. The antibodies to B7 also targeted human and rat alpha3127-148. B7 induced T cell activation from human alpha3127-148-immunized rats. T cell responses to B7 were detected in rats immunized by Actinomyces lysate proteins or recombinant proteins. We confirmed B7's pathogenicity in HLADR15 transgenic mice that developed kidney injury similar to that observed in a3135-145-immunized mice. Conclusion(s): Sera from patients with anti-GBM disease recognizedmicrobial peptides identified through a bioinformatic approach, and a peptide fromActinomycesinduced experimental anti-GBMGNbyTandBcell crossreactivity. These studies demonstrate that anti-GBM disease may be initiated by immunization with a microbial peptide.Copyright © 2020 by the American Society of Nephrology.

Background: Loss of tolerance to MPO in ANCA-associated glomerulonephritis (GN) is poorly understood. It is unknown whether molecular mimicry plays any role in this process. We tested whether microbial peptides homologous to a dominant pathogenic MPO CD4+ T cell epitope (MPO409-428), relevant to several MHCII and lying within an MPO epitope hot spot, would induce anti-MPO autoimmunity. Method(s): Immunity to MPO and MPO409-428 was studied in microbial peptide immunized C57BL/6 (B/6, I-Ab), BALB/c (I-Ad/Ed) and HLA-DR15 transgenic mice (proliferation, IFN-gamma and IL-17A ELISPOT). Anti-MPO GN and anti-MPO immunity in response to peptides, proteins (MPO/ovalbumin as positive/negative controls) and S.aureus strains with/without plasmids carrying the relevant 6-phosphogluconate dehydrogenase (6PGD) sequence were studied in B/6 mice (I-Ab/MPO415-428 tetramers, cytokines, MPOANCA IIF/ELISA, neutrophil ROS production, MPO-ANCA transfer). Anti-6PGD antibodies (Ab) were measured in sera of healthy humans and patients. Result(s): The 4 most homologous microbial peptides were immunogenic but did not induce anti-MPO autoreactivity. However, a plasmid-derived peptide from 6PGD (6PGDp) with similar critical binding residues for MPO409-428 in B/6, BALB/c and DR15+ mice, found in some S.aureus strains, induced expansion of MPO415-428 tetramer+CD4+ cells, anti-MPO T cell autoimmunity (to MPO408-428 and whole MPO) and bioactive MPO-ANCA in B/6 mice. 6PGDp induced anti-MPO autoreactivity in mice with different MHCII (I-Ad/Ed and DR15). Related 6PGD sequences from other S.aureus strains did not induce anti-MPO responses. Healthy human and vasculitis patient sera contained anti-6PGD Ab, demonstrating its immunogenicity in humans. 6PGDp-immunized mice developed GN when MPO was deposited in glomeruli by anti-basement membrane globulin. Immunization with S.aureus containing a plasmid with the mimic 6PGD sequence, or another S.aureus strain transformed with a different plasmid expressing t

Regulatory T cells (Tregs) are a small yet critical subset of CD4+ T cells, which have the role of maintaining immune homeostasis by, for example, regulating self-tolerance, tumor immunity, anti-microbial resistance, allergy and transplantation rejection. The suppressive mechanisms by which Tregs function are varied and pleiotropic. The ability of Tregs to maintain self-tolerance means they are critical for the control and prevention of autoimmune diseases. Irregularities in Treg function and number can result in loss of tolerance and autoimmune disease. Restoring immune homeostasis and tolerance through the promotion, activation or delivery of Tregs has emerged as a focus for therapies aimed at curing or controlling autoimmune diseases. Such therapies have focused on the Treg cell subset by using drugs to suppress T effector cells and promote Tregs. Other approaches have trialed inducing tolerance by administering the autoantigen via direct administration, by transient expression using a DNA vector, or by antigen-specific nanoparticles. More recently, cell-based therapies have been developed as an approach to directly or indirectly enhance Treg cell specificity, function and number. This can be achieved indirectly by transfer of tolerogenic dendritic cells, which have the potential to expand antigen-specific Treg cells. Treg cells can be directly administered to treat autoimmune disease by way of polyclonal Tregs or Tregs transduced with a receptor with high affinity for the target autoantigen, such as a high affinity T cell receptor (TCR) or a chimeric antigen receptor (CAR). This review will discuss the strategies being developed to redirect autoimmune responses to a state of immune tolerance, with the aim of the prevention or amelioration of autoimmune disease.Copyright © 2020 by the authors. Licensee MDPI, Basel, Switzerland.

Autoreactivity to myeloperoxidase (MPO) causes anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), with rapidly progressive glomerulonephritis. Here, we show that a Staphylococcus aureus peptide, homologous to an immunodominant MPO T-cell epitope (MPO409-428), can induce anti-MPO autoimmunity. The peptide (6PGD391-410) is part of a plasmid-encoded 6-phosphogluconate dehydrogenase found in some S. aureus strains. It induces anti-MPO T-cell autoimmunity and MPO-ANCA in mice, whereas related sequences do not. Mice immunized with 6PGD391-410, or with S. aureus containing a plasmid expressing 6PGD391-410, develop glomerulonephritis when MPO is deposited in glomeruli. The peptide induces anti-MPO autoreactivity in the context of three MHC class II allomorphs. Furthermore, we show that 6PGD391-410 is immunogenic in humans, as healthy human and AAV patient sera contain anti-6PGD and anti-6PGD391-410 antibodies. Therefore, our results support the idea that bacterial plasmids might have a function in autoimmune disease.Copyright © 2019, The Author(s).

Background Myeloperoxidase (MPO)-ANCA-associated GN is a significant cause of renal failure. Manipulating autoimmunity by inducing regulatory T cells is potentially a more specific and safer therapeutic option than conventional immunosuppression. Methods To generate MPO-specific regulatory T cells, we used a modified protein-conjugating compound, 1-ethyl-3-(3'dimethylaminopropyl)-carbodiimide (ECDI), to couple the immunodominant MPO peptide (MPO409-428) or a control ovalbumin peptide (OVA323-339) to splenocytes and induced apoptosis in the conjugated cells. We then administered MPO-and OVA-conjugated apoptotic splenocytes (MPO-Sps and OVA-Sps, respectively) to mice and compared their effects on development and severity of anti-MPO GN. We induced autoimmunity to MPO by immunizing mice with MPO in adjuvant; to trigger GN, we used low-dose antiglomerular basement membrane globulin, which transiently recruits neutro-phils that deposit MPO in glomeruli. We also compared the effects of transferring CD4+ T cells from mice treated with MPO-Sp or OVA-Sp to recipient mice with established anti-MPO autoimmunity. Results MPO-Sp but not OVA-Sp administration increased MPO-specific, peripherally derived CD4+ Foxp3- type 1 regulatory T cells and reduced anti-MPO autoimmunity and GN. However, in mice depleted of regulatory T cells, MPO-Sp administration did not protect from anti-MPO autoimmunity or GN. Mice with established anti-MPO autoimmunity that received CD4+ T cells transferred from mice treated with MPO-Sp (but not CD4+ T cells transferred from mice treated with OVA-Sp) were protected from anti-MPO autoimmunity and GN, confirming the induction of therapeutic antigen-specific regulatory T cells. Conclusions These findings in a mouse model indicate that administering apoptotic splenocytes conjugated with the immunodominant MPO peptide suppresses anti-MPO GN by inducing antigen-specific tolerance.Copyright © 2019 by the American Society of Nephrology.

Background: Myeloperoxidase (MPO)-ANCA-associated GN is a significant cause of renal failure. Manipulating autoimmunity by inducing regulatory T cells is potentially a more specific and safer therapeutic option than conventional immunosuppression. Method(s): To generate MPO-specific regulatory T cells, we used a modified protein-conjugating compound, 1-ethyl-3-(3'dimethylaminopropyl)-carbodiimide (ECDI), to couple the immunodominant MPO peptide (MPO409-428) or a control ovalbumin peptide (OVA323-339) to splenocytes and induced apoptosis in the conjugated cells. We then administered MPO- and OVA-conjugated apoptotic splenocytes (MPO-Sps and OVA-Sps, respectively) to mice and compared their effects on development and severity of anti-MPO GN. We induced autoimmunity to MPO by immunizing mice with MPO in adjuvant; to trigger GN, we used low-dose antiglomerular basement membrane globulin, which transiently recruits neutrophils that deposit MPO in glomeruli. We also compared the effects of transferring CD4+ T cells from mice treated with MPO-Sp or OVA-Sp to recipient mice with established anti-MPO autoimmunity. Result(s): MPO-Sp but not OVA-Sp administration increased MPO-specific, peripherally derived CD4+Foxp3- type 1 regulatory T cells and reduced anti-MPO autoimmunity and GN. However, in mice depleted of regulatory T cells, MPO-Sp administration did not protect from anti-MPO autoimmunity or GN. Mice with established anti-MPO autoimmunity that received CD4+ T cells transferred from mice treated with MPO-Sp (but not CD4+ T cells transferred from mice treated with OVA-Sp) were protected from anti-MPO autoimmunity and GN, confirming the induction of therapeutic antigen-specific regulatory T cells. Conclusion(s): These findings in a mouse model indicate that administering apoptotic splenocytes conjugated with the immunodominant MPO peptide suppresses anti-MPO GN by inducing antigen-specific tolerance.Copyright © 2019 by the American Society of Nephrology.

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, alpha3135-145-specific, pro-inflammatory T cell recall responses were measured using IFN-gamma 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 alpha3135-145-specific immune responses and disease development. Mice treated prior to immunization with alpha3135-145 had reduced alpha3135-145-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-alpha3(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 alpha3(IV)NC1-specific pro-inflammatory responses and could be used as an adjunct therapy for anti-GBM disease.Copyright © 2019 Elsevier Ltd

Autoimmune diseases resulting from MHC class II-restricted autoantigen-specific T cell immunity include the systemic inflammatory autoimmune conditions rheumatoid arthritis and vasculitis. While currently treated with broad-acting immunosuppressive drugs, a preferable strategy is to regulate antigen-specific effector T cells (Teffs) to restore tolerance by exploiting DC antigen presentation. We targeted draining lymph node (dLN) phagocytic DCs using liposomes encapsulating 1alpha,25-dihydroxyvitamin D3 (calcitriol) and antigenic peptide to elucidate mechanisms of tolerance used by DCs and responding T cells under resting and immunized conditions. PD-L1 expression was upregulated in dLNs of immunized relative to naive mice. Subcutaneous administration of liposomes encapsulating OVA323-339 and calcitriol targeted dLN PD-L1hi DCs of immunized mice and reduced their MHC class II expression. OVA323-339/calcitriol liposomes suppressed expansion, differentiation, and function of Teffs and induced Foxp3+ and IL-10+ peripheral Tregs in an antigen-specific manner, which was dependent on PD-L1. Peptide/ calcitriol liposomes modulated CD40 expression by human DCs and promoted Treg induction in vitro. Liposomes encapsulating calcitriol and disease-associated peptides suppressed the severity of rheumatoid arthritis and Goodpasture's vasculitis models with suppression of antigen-specific memory T cell differentiation and function. Accordingly, peptide/calcitriol liposomes leverage DC PD-L1 for antigen-specific T cell regulation and induce antigen-specific tolerance in inflammatory autoimmune diseases.Copyright © 2019, American Society for Clinical Investigation.

Anti-myeloperoxidase nephritogenic autoimmunity induces severe glomerulonephritis. To assess the therapeutic potential of monoclonal antibodies targeting T helper (Th) subset differentiation determining cytokines, we studied a murine model of anti-myeloperoxidase glomerulonephritis. The temporal participation of T helper subsets was determined by quantitating gene expression of CD4+ T-cells isolated from nephritic kidneys and cytokine production by lymphocytes from nodes draining myeloperoxidase immunization sites. Th17 cytokines (IL-17A and IL-6) rose rapidly but declined as autoimmunity matured when Th1 cytokines (IL-12 and TNF) predominated. Therefore, T helper subset participation in anti-myeloperoxidase autoimmunity is biphasic, with Th17 early and Th1 late. To confirm the functional relevance of this biphasic pattern, we compared systemic anti-myeloperoxidase autoimmunity in wild type, Th17 deficient and Th1 deficient mice. Early, Th1 deficient mice developed similar autoimmunity and glomerulonephritis to wild type mice. However, Th17 deficient mice had significantly reduced anti-myeloperoxidase autoimmunity. In late autoimmunity, Th1 deficient mice developed reduced autoimmunity and were protected from anti-myeloperoxidase glomerulonephritis. The therapeutic potential of these findings were demonstrated by neutralizing monoclonal antibodies. Targeting IL-23p19 attenuated early Th17 dominated anti-myeloperoxidase autoimmunity and glomerulonephritis but not late phase disease. Targeting IL-12p35 attenuated late phase Th1 dominated anti-myeloperoxidase autoimmunity and glomerulonephritis but not early autoimmunity or glomerulonephritis. Targeting both T helper subsets with an anti-IL-12p40 monoclonal antibody was effective during both early and late phases of anti-myeloperoxidase glomerulonephritis. Thus, definition of dominant T helper differentiating subsets in anti-myeloperoxidase glomerulonephritis by renal CD4+ T-cell cytokine gene expression allows effecti

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. The kidney is vulnerable to immune mediated injury. Regulated T cells can modulate the systemic autoimmune and allogenic responses in glomerulonephritis and transplantation. Furthermore, intrarenal regulatory T cells can effect suppression on immune and intrinsic kidney cells.Copyright © 2018 The Authors. Clinical & Translational Immunology published by John Wiley & Sons Australia, Ltd on behalf of Australasian Society for Immunology Inc.

Since the first association between HLA and diseases of native kidneys was described almost 50 years ago, technological and conceptual advances in HLA biology and typing, together with better case ascertainment, have led to an improved understanding of HLA associations with a variety of renal diseases. A substantial body of evidence now supports the existence of HLA genetic associations in the field of renal disease beyond the role of HLA in allogeneic responses in transplant recipients. Allomorphs of HLA have emerged as important risk factors in most immune-mediated renal diseases, which, together with other genetic and environmental factors, lead to loss of tolerance and autoimmune-mediated renal inflammation. HLA associations have also been described for renal diseases that are less traditionally seen as autoimmune or immune-mediated. Here, we review essential concepts in HLA biology and the association of HLA with diseases of the native kidneys, and describe the current understanding of the epistatic and mechanistic bases of HLA-associated kidney disease. Greater understanding of the relationship between HLA and kidney function has the potential not only to further the understanding of immune renal disease at a fundamental level but also to lead to the development and application of more effective, specific and less toxic therapies for kidney diseases.Copyright © 2018, Springer Nature Limited.

Introduction Animal models have been significant contributors to our understanding of the pathogenesis of many autoimmune diseases, and in some cases have also been useful as pre-clinical models to inform the development of new treatments. A number of animal models have been developed to help understand the pathogenesis of antineutrophil antibody (ANCA)-associated vasculitis (AAV). This commentary will focus on some of the models of myeloperoxidase (MPO)-ANCA associated glomerulonephritis, briefly outlining some of the currently available models (several recent detailed reviews exist) and reviewing some of the recent insights gained from these models in the last two years. Models of MPO-ANCA Associated Glomerulonephritis Models induced by MPO-ANCA-Like Antibodies Transfer of MPO-ANCA like antibodies induced by immunising Mpo-/-mice with native mouse MPO induces proteinuria, haematuria and focal necrotising and crescentic glomerulonephritis [1, 2]. Neutrophil accumulation, assessed several hours after anti-MPO antibody transfer can be induced by low doses of anti-MPO antibodies, but higher doses of anti-MPO antibodies are required for more significant injury [3, 4] and the severity of injury can be increased by pre-treating mice with LPS [5]. The degree of injury, usually measured at day six, is variable, probably due at least in part to the titre and pathogenicity of the antiMPO antibodies raised in the Mpo-/-mice [1, 3, 6]. However, recent publications point towards the capacity for neutrophils to be activated and the numbers of neutrophils in the peripheral blood as important. Xiao et al. found that the 129S6/SvEv and CAST/EiJ mouse strains were markedly more susceptible in this model [7]. Genetic analyses were consistent with the involvement of multiple genetic interactions and studies on neutrophil activation showed that 126S6 neutrophils were more strongly activated by TNF and anti-MPO antibodies [7]. A different approach was taken by Feeley et al [8]. By pre-t

The prospects for complement-targeted therapy in ANCA-associated vasculitis have been enhanced by a recent clinical trial in which C5a receptor 1 (C5aR1) inhibition safely replaced glucocorticoids in induction treatment. C5aR1 primes neutrophils for activation by anti-neutrophil cytoplasmic antibody (ANCA) and is therefore required in models of glomerulonephritis induced by anti-myeloperoxidase antibody. Although humoral and cellular autoimmunity play essential roles in ANCA-associated vasculitis, a role for C5aR1 in these responses has not been described. Here, we use murine models to dissect the role of C5aR1 in the generation of anti-myeloperoxidase autoimmunity and the effector responses resulting in renal injury. The genetic absence or pharmacological inhibition of C5aR1 results in reduced autoimmunity to myeloperoxidase with an attenuated Th1 response, increased Foxp3+ regulatory T cells and reduction in generation of myeloperoxidase-ANCA. These changes are mediated by C5aR1 on dendritic cells, which promotes activation, and thus myeloperoxidase autoimmunity and glomerulonephritis. We also use renal intravital microscopy to determine the effect of C5aR1 inhibition on ANCA induced neutrophil dysfunction. We found that myeloperoxidase-ANCA induce neutrophil retention and reactive oxygen species burst within glomerular capillaries. These pathological behaviors are abrogated by C5aR1 inhibition. Thus, C5aR1 inhibition ameliorates both autoimmunity and intra-renal neutrophil activation in ANCA-associated vasculitis.Copyright © 2017 International Society of Nephrology

Observations in patients with ANCA-associated vasculitis suggest that CD8+ T cells participate in disease, but there is no experimental functional evidence of pathologic involvement for these cells. Myeloperoxidase (MPO) is a well defined autoantigen in ANCA-associated vasculitis. Studies in experimental models of anti-MPO GN suggest that, after ANCA-induced neutrophil localization, deposited MPO within glomeruli is recognized by autoreactive T cells that contribute to injury. We tested the hypothesis that CD8+ T cells mediate disease in experimental ANCA-associated vasculitis. CD8+ T cell depletion in the effector phase of disease attenuated injury in murine anti-MPO GN. This protection associated with decreased levels of intrarenal IFN-gamma, TNF, and inflammatory chemokines and fewer glomerular macrophages. Moreover, we identified a pathogenic CD8+ T cell MPO epitope (MPO431-439) and found that cotransfer of MPO431-439-specific CD8+ T cell clones exacerbated disease mediated by MPO-specific CD4+ cells in Rag1-/- mice. Transfer of MPO431-439-specific CD8+ cells without CD4+ cells mediated glomerular injury when MPO was planted in glomeruli. These results show a pathogenic role for MPO-specific CD8+ T cells, provide evidence that CD8+ cells are a therapeutic target in ANCA-associated vasculitis, and suggest that a molecular hotspot within the MPO molecule contains important CD8+, CD4+, and B cell epitopes.Copyright © 2016 by the American Society of Nephrology.

Objectives: In microscopic polyangiitis, autoreactivity to myeloperoxidase (MPO) can cause rapidly progressive glomerulonephritis. While it is unknown how tolerance to MPO is lost, infections have been implicated in the development of autoimmunity and disease. MPO409-428 is a promiscuous MPO CD4+ T-cell epitope overlapping a pathogenic B cell MPO epitope. This study tests the hypothesis that molecular mimicry can induce pathogenic anti-MPO autoimmunity. Method(s): BLAST searches were used to identify candidate microbial peptides with homology to MPO409-428. Anti-MPO T-cell responses were determined by immunizing C57BL/6 mice with candidate peptides, then measuring recall responses to MPO by 3[H]-T proliferation and IFN-g and IL-17A ELISPOTs. Anti-MPO antibodies were measured by ELISA, indirect immunofluorescence, and their activity by ex vivo ROS production and by neutrophil glomerular recruitment after passive antibody transfer. Disease was induced by immunizing mice with peptide or whole bacteria, followed by depositing MPO in the glomerulus using low-dose sheep anti-mouse basement membrane globulin. Result(s): Immunizing C57BL/6 mice with 4 different peptides from human pathogens most homologous to the core residues of MPO409-428 did not trigger autoreactivity to MPO or MPO409-428. However, immunization with a peptide derived from 6-phosphogluconate dehydrogenase (mimic-6-pgd), found only in some strains of Staphylococci, did induce T cell autoreactivity to MPO. The corresponding mammalian and closely related bacterial 6-pgd sequences did not induce anti-MPO autoimmunity, demonstrating the specificity of this sequence. Mimic-6-pgd peptide immunization induced MPOANCA that stained neutrophils in a p-ANCA pattern and were functionally active in vitro and in vivo. Mimic-6-pgd-induced MPO T cell autoreactivity resulted in anti-MPO glomerulonephritis in a T cell mediated model. Furthermore, when MPO was planted in glomeruli, mice immunized with whole killed Staphyloco

Aim: To use Goodpasture's disease (GPD), a classical form of HLA-linked autoimmunity, to define the mechanism of HLA-mediated risk, and dominant protection from risk of disease. Background(s): The mechanisms underpinning HLA-mediated susceptibility to, and protection from autoimmune diseases are unknown. GPD is HLAlinked and characterized by an immunodominant CD4+ self-epitope derived from the alpha3 chain of Type IV collagen (alpha3135-145). Method(s): HLA-DR transgenic mice, cells from HLA-typed healthy humans and from patients with GPD were used, with HLA-DR-alpha3135-145 tetramers, Xray crystallography, and in vivo/in vitro models of autoimmunity. Result(s): Autoreactive alpha3135-145-specific T cells clonally expanded in GPD patients. In alpha3135-145-immunized HLA-DR15 transgenic mice with GPD, alpha3135-145-specific T cells infiltrated the kidney. Structurally, HLA-DR15 and HLA-DR1 presented alpha3135-145 in different binding registers, resulting in differential T cell receptor (TCR) usage. HLA-DR15-alpha3135-145 tetramer+ CD4+ T cells in disease susceptible HLA-DR15 transgenic mice exhibited a conventional phenotype (Tconv), secreting pro-inflammatory cytokines. In contrast, HLA-DR1-alpha3135-145 tetramer+ cells in disease resistant HLA-DR1 and HLADR15/ DR1 transgenic mice were largely CD4+Foxp3+ regulatory T cells (Tregs) expressing tolerogenic cytokines. In HLA-DR15/DR1 transgenic mice, HLA-DR1-alpha3135-145 specific Tregs conferred protection to alpha3135-145-specific autoimmunity and protected from GPD (alpha3135-145-immunized, Treg intact vs Treg depleted: segmental necrosis 0+/-0 vs 50+/-13% P<0.01, serum urea 9+/-1 vs 31+/-10 P<0.001). HLA-DR15+ and HLA-DR1+ healthy human donors displayed altered alpha3135-145-specific TCRs, with HLA-DR15-alpha3135-145 tetramer+ Foxp3- Tconv and HLA-DR1-alpha3135-145 tetramer+ Foxp3+CD25hiCD127lo Treg dominant phenotypes (alpha3135-145 tetramer+ Treg:Tconv ratios: DR15 0.04+/-0.00, DR1 9.61+/-1.79, P<0.001). Conclusio

Objectives: Anti-glomerular basement membrane (GBM) disease is a small vessel vasculitis caused by anti-a3(IV)NC1 T and B cell autoreactivity. An immunodominant T cell epitope, a3135-145, has been defined. HLA-DR15 confers an increased disease risk (OR 8.5) while HLA-DR1 is dominantly protective from this risk. These studies aimed to define the mechanisms by which different HLA-DR alleles lead to susceptibility or protection from disease. Method(s): a3135-145-specific CD4+ T cells were enumerated in anti-GBM patients, HLA-typed healthy humans and HLA-DR transgenic mice using HLA-DR-a3135-145 tetramers. The crystal structures of HLADR15-a3135-145 and HLA-DR1-a3135-145 were solved. a3135-145-specific T cell receptor (TCR) usage was determined by single cell sequencing. T cell phenotype was determined by flow cytometry. T cell responses were determined in vivo, ex vivo and by culturing naive T cells with a3135-145 in vitro. Experimental autoimmune anti-GBM disease was induced by a3135-145 immunization of HLA-DR transgenic mice (Treg intact or Treg depleted). Result(s): a3135-145-specific CD4+ T cells were expanded in anti-GBM patients and infiltrated kidneys of a3135-145-immunized HLA-DR15 transgenic mice. Mice transgenic for both HLA-DR15 and HLA-DR1 showed similar reactivity to most a3 peptides, but lacked proinflammatory responses to a3135-145. Structurally, HLA-DR15 and HLA-DR1 presented a3135-145 in different binding registers. Compared to the conformation of a3135-145 in HLA-DR15, in HLA-DR1 a3135-145 adopted a more pronounced conformation with a flipped backbone. These different HLA-peptide conformations altered a3135-145-specific TCR usage and T cell phenotypes. HLA-DR15-a3135-145-specific T cells exhibited a Foxp3-conventional T cell phenotype resulting in proinflammatory T cell autoreactivity, anti-GBM antibody production and disease. In contrast, HLA-DR1-a3135-145-specific T cells were predominantly anti-inflammatory Foxp3+ Tregs that proliferated and respon

Aim: To test the hypothesis that biological neutralization of the dominant T helper (TH) cell subset inducing cytokine attenuates anti-MPO GN. Background(s): Both CD4+ TH17 and TH1 cells, have been demonstrated to be pathogenic in anti-MPO GN. Definition of the dominant TH subset would allow targeted biological treatment. Method(s): Anti-MPO autoimmunity was induced by MPO immunization and GN triggered using anti-GBM Ig. TH subsets in anti-MPO GN was defined by their cytokine profile in draining lymph nodes (dLN) and glomerular effector responses. TH subsets was assessed early after induction of anti-MPO GN on day 20 (d20) and when disease was fully established (d32). Result(s): In WT mice, anti-MPO GN progressively intensifies from d20 to d32 with increasing frequency of segmental necrosis (10+/-1vs17+/-2%, P<0.01) and albuminuria (1.22+/-0.2vs2.0+/-0.2mg/24hr, P<0.05). Analysis of TH cytokines in dLN showed key TH17 cytokines, IL-17A (2.8+/-0.1vs1.6+/-0.3ng/ml, P<0.05) and IL-6 were maximal at d20 and subsides by d32 while TH1 dominant cytokines, IFNgamma (19.9+/-8.1vs52.9+/-12.3pg/ml, P<0.05) and TNF-alpha were maximum at d32. Gene analysis of isolated kidney CD4+ T cells demonstrated that expression of TH17 genes (IL-17A, CCR6, TGF-beta) are more upregulated early while upregulation of TH1 genes (IFNgamma, CXCR3, STAT4) increases by d32. This suggests TH17 dominates GN early and TH1 late. Treatment with monoclonal antibodies (mAb) to the TH17 inducing cytokine, IL-23p19, attenuated GN (albuminuria; 105.3+/-28.2vsIgG2b controls; 325.4+/-60.5 mug/24hr, P<0.01) on d20 but not on d32. Whereas mAb to TH1 inducing cytokine, IL-12p35, was protective at d32 (albuminuria, 788.2+/-323.3vs IgG2a controls; 1797+/-229.9 mug/24hr, P<0.05). Conclusion(s): In anti-MPO GN, TH subset dominance is biphasic, TH17 early then TH1 late. Anti-cytokine biological treatment is effective only when it targets the dominant TH cytokines inducing anti-MPO GN.

Observations in experimental murine myeloperoxidase (MPO)-ANCA-associated vasculitis (AAV) show mast cells degranulate, thus enhancing injury as well as producing immunomodulatory IL-10. Here we report that, compared with biopsy specimens from control patients, renal biopsy specimens from 44 patients with acute AAV had more mast cells in the interstitium, which correlated with the severity of tubulointerstitial injury. Furthermore, most of the mast cells were degranulated and spindle-shaped in patients with acute AAV, indicating an activated phenotype. We hypothesized that the mast cell stabilizer disodium cromoglycate would attenuate mast cell degranulation without affecting IL-10 production. We induced anti-MPO GN by immunizing mice with MPO and a low dose of anti-glomerular basement membrane antibody. When administered before or after induction of MPO autoimmunity in these mice, disodium cromoglycate attenuated mast cell degranulation, development of autoimmunity, and development of GN, without diminishing IL-10 production. In contrast, administration of disodiumcromoglycate tomast cell-deficientmice had no effect on the development of MPO autoimmunity or GN. MPO-specific CD4+ effector T cell proliferationwas enhanced by co-culture with mast cells, but in the presence of disodiumcromoglycate, proliferation was inhibited and IL-10 production was enhanced. These results indicate that disodium cromoglycate blocks injurious mast cell degranulation specifically without affecting the immunomodulatory role of these cells. Thus as a therapeutic, disodium cromoglycate may substantially enhance the regulatory role of mast cells in MPO-AAV.Copyright © 2016 by the American Society of Nephrology.

Anti-GBM disease is a form of small vessel vasculitis that manifests as rapidly progressive glomerulonephritis. It has a strong association with the HLA-DR15 allele (odds ratio: 8.5), and the immunodominant T cell epitope a3135-145 is restricted to HLA-DR15. A DR15-specific inhibitor, PV-267, has potential as a targeted therapy, as current treatment is broadly immunosuppressive and has detrimental side effects. This study aims to demonstrate that specific inhibition of HLA-DR15 prevents autoreactivity to the immunodominant T cell epitope and attenuates injury in experimental autoimmune anti-glomerular basement membrane (GBM) disease. HLA-DR15 transgenic mice (backcrossed onto an FcgRIIb-/-background) were used in this study. Autoreactivity to a3135-145 was determined by immunising mice with a3135-145 at day 0, while administering PV-267 daily (30mg/kg) from day-1 to day 10, then measuring recall responses ex vivo by [3H]-thymidine proliferation and IFNg and IL-17A ELISPOTs. Experimental autoimmune anti-GBM disease was induced in mice by immunisations of a3135-145 at days 0, 7, and 14. In a prevention model, mice were administered PV-267 every second day (30mg/kg) from day-1 to day 42. In a treatment model, PV-267 was administered daily (50mg/kg) from day 28 to day 42. Mice were culled at day 42. Functional and histological endpoints, as well as immune cell infiltration were determined. Compared with mice that received vehicle control, mice that received PV-267 had reduced a3135-145-specific proliferation (SI: 9.5+/-0.9 vs 2.2+/-0.5, P<0.001) as well as reduced numbers of IFNg and IL-17A spots. In the prevention model of disease, mice given PV-267 had fewer infiltrating glomerular CD4+ T-cells (0.90+/-0.12 vs 0.36+/-0.03 cells/glomerular cross section, P<0.01), reduced albuminuria (albumin/creatinine ratio: 0.215+/-0.056 vs 0.010+/-0.007 mg/mmol, P<0.01), and reduced glomerular segmental necrosis and crescents. In the treatment model, there was no difference in album

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 selfepitope derived from the a3 chain of type IV collagen (a3135-145)1-4. 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 a3135-145-specific T cells expand in patients with Goodpasture disease and, in a3135-145- immunized HLA-DR15 transgenic mice, a3135-145-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 a3135-145 epitope in different binding registers. HLA-DR15-a3135-145 tetramer+ T cells in HLA-DR15 transgenic mice exhibit a conventional T-cell phenotype (Tconv) that secretes pro-inflammatory cytokines. In contrast, HLADR1- a3135-145 tetramer+ T cells in HLA-DR1 and HLA-DR15/DR1 transgenic mice are predominantly CD4+Foxp3+ regulatory T cells (Treg cells) expressing tolerogenic cytokines. HLA-DR1-induced Treg cells confer resistance to disease in HLA-DR15/DR1 transgenic mice. HLA-DR15+ and HLA-DR1+ healthy human donors display altered a3135-145-specific T-cell antigen receptor usage, HLADR15- a3135-145 tetramer+ Foxp3- Tconv and HLA-DR1-a3135-145 tetramer+ Foxp3+CD25hiCD127lo Treg dominant phenotypes. Moreover, patients with Goodpasture disease display a clonally expanded a3135-145-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 ab

MPO-specific CD4+ and CD8+ T cells have the capacity to induce injury in experimental anti-MPO glomerulonephritis (GN) in mice. However, mechanisms by which CD8+ cells participate in disease in this model have not been elucidated. Patients with an unfavorable prognosis have a non-exhausted CD8+ phenotype associated with increased signaling through the IL-7Ra (CD127). Furthermore, the inhibitory receptor PD-1 is associated with reduced IL-7R signaling. We therefore investigated the contribution of the IL-7R to anti-MPO GN by blocking IL-7 signalling using a neutralizing but non-depleting anti-IL-7Ra antibody. Anti-MPO autoimmunity was induced by immunizing mice with recombinant mouse MPO (rmMPO) at day 0 and 7. GN was triggered using a subnephritogenic dose of anti-mouse basement membrane globulin at day 16 (this induces neutrophil recruitment and deposits MPO in glomeruli), and mice culled at day 20. We also used an extended model where immunization remained at days 0 and 7 (rmMPO or OVA), but the trigger was delayed until day 43 and mice were culled at day 47. Comparing CD8+ and CD4+ cells at days 20 and 47, a higher proportion of intrarenal and splenic CD8+ cells expressed CD127 at day 20 compared to day 47 in the MPO immunized groups. In contrast, a higher proportion of renal and splenic CD8+ cells expressed PD-1 at day 47 in MPO immunised mice, suggesting that the CD8+ cells are more exhausted at this time point. A similar pattern was also seen on CD4+ T cells, suggesting that the role of IL-7 signalling in this model may not be restricted to CD8+ T cells. Administration of anti-IL-7Ra antibodies after the induction of anti-MPO autoimmunity (commencing day 15) in the day 20 model attenuated anti-MPO GN with reduced albuminuria, segmental necrosis, dermal DTH, glomerular leukocytes and renal chemokines (CCL2, CXCL1, CXCL10 and CXCL20) compared with control antibody treatment. However, PD-1 expression in the kidney was not correspondingly increased in MPO immunize

Myeloperoxidase (MPO) anti-neutrophil cytoplasmic Ab (ANCA)-associated vasculitis results from autoimmunity to MPO. IL-17A plays a critical role in generating this form of autoimmune injury but its cell of origin is uncertain. We addressed the hypothesis that IL-17A-producing gd T cells are a nonredundant requisite in the development of MPO autoimmunity and glomerulonephritis (GN).We studied MPO-ANCA GN in wild type, ab, or gd T cell-deficient (C57BL/6, bTCR2/2, and dTCR2/2 respectively) mice. Both T cell populations played important roles in the generation of autoimmunity to MPO and GN. Humoral autoimmunity was dependent on intact ab T cells but was unaffected by gd T cell deletion. Following MPO immunization, activated gd T cells migrate to draining lymph nodes. Studies in dTCR2/2 and transfer of gd T cells to dTCR2/2 mice show that gd T cells facilitate the generation of anti-MPO autoimmunity and GN. dTCR2/2 mice that received IL-17A2/2 gd T cells demonstrate that the development of anti-MPO autoimmunity and GN are dependent on gd T cell IL-17A production. Finally, transfer of anti-MPO CD4+ T cell clones to naive dTCR2/2 and wild type mice with planted glomerular MPO shows that gd T cells are also necessary for recruitment of anti-MPO ab CD4+ effector T cells. This study demonstrates that IL-17A produced by gd T cells plays a critical role in the pathogenesis of MPO-ANCA GN by promoting the development of MPO-specific ab T cells.Copyright © 2017 by The American Association of Immunologists, Inc.

Less toxic treatment options for patients with myeloperoxidase (MPO)-ANCA-associated GN are needed. Using an established murine model of focal necrotizing GN mediated by autoimmunity to MPO (autoimmune anti-MPO GN), we assessed the capacity for nasal tolerance induced by nasal insufflation of the immunodominant nephritogenic MPO peptide (MPO409-428) to attenuate this disease. Compared with mice that received an irrelevant immunodominant ovalbumin (OVA) peptide, OVA323-339, mice that received MPO409-428 were protected from the development of humoral and cell-mediated autoimmunity to full-lengthMPOand the development of GN. In mice with established anti-MPO autoimmunity, nasal insufflation of MPO409-428 as a therapeutic attenuated anti-MPO GN. To investigate the nature of this induced tolerance, we isolated CD4+ T cells from the upper airway draining lymph nodes of both OVA323-339-and MPO409-428-tolerized mice. Adoptive transfer of CD4+ T cells from MPO409-428-but not OVA323-339-tolerized mice to animals with established anti-MPO autoimmunity attenuated the subsequent development of GN, confirming that the immunosuppression induced by these T cells is antigen specific. Ex vivo studies showed that nasal tolerance to MPO is mediated by both conventional and induced T regulatory cells. The strong homology between the pathogenic human MPO B cell epitope recognized by ANCA in patients with acute vasculitis and the nephritogenic murine T cell MPO epitope emphasizes the clinical relevance of this study.Copyright © 2016 by the American Society of Nephrology.

Microscopic polyangiitis is a small-vessel vasculitic autoimmune disease whereby autoreactivity to the neutrophil enzyme myeloperoxidase (MPO) causes rapidly progressive glomerulonephritis. It is unknown how tolerance is lost, but there are reports in patients that S aureus infections precede anti- MPO autoimmunity, and in other forms of vasculitis, molecular mimicry has been shown to induce cross-reactive pathogenic autoimmunity. This study tests the hypothesis that molecular mimicry induces cross-reactive pathogenic anti-MPO autoimmunity. A BLAST search was used to identify 5 candidate microbial peptides with homology to the immunodominant MPO T-cell epitope, MPO409-428. Anti-MPO T-cell responses were determined by immunizing C57BL/6 mice with candidate peptides then measuring recall responses ex vivo to MPO by 3 [H]-T proliferation and IFN-gamma and IL-17 ELISPOTs. Anti-MPO antibodies were measured by ELISA, immunofluorescence on ethanol-fixed neutrophils and by enumerating neutrophil glomerular recruitment after passive transfer of antibody. Disease was assessed by immunizing mice with peptide or whole bacteria followed by depositing MPO in the glomerulus using low-dose sheep anti-mouse glomerular basement membrane antibodies, then measuring functional and histological endpoints. Only 1 peptide induced cross-reactive T-cell responses to MPO. This peptide was derived from a S aureus plasmid. Antibodies from mice immunized with this peptide cross-reacted with MPO, bound to neutrophils in a perinuclear fashion, and induced neutrophil glomerular recruitment. Furthermore, mice immunized with either this peptide or a clinical strain of S aureus containing the plasmid, developed albuminuria and focal necrotizing glomerulonephritis. This shows that molecular mimicry by a S aureus plasmid derived peptide induces anti-MPO pathogenic autoimmunity.

The generation of inbred mouse strains in the late 19th and early 20th centuries, coupled with the later establishment of specific pathogen-free animal research facilities created a powerful biological platform for exploration of the immune system in health and disease. Studies in this setting have been responsible for huge advances in our understanding of immunobiology and disease, including immune-mediated kidney disease. However, whereas this reductionist and relatively standardized approach allows us to make sense of complex disease biology, it takes place in controlled environments that clearly differ from those that we humans encounter in everyday life. Recent studies comparing the immune systems of wild mice, pet shop mice, and laboratory mice suggest ways in which the murine immune system can be influenced to behave more like the human immune system.Copyright © 2016 International Society of Nephrology

Anti-glomerular basement membrane (GBM) disease is an autoimmune disease that manifests as rapidly progressive glomerulonephritis. It has a strong HLA association with the DR15 allele (odds ratio: 8.5) and the immunodominant, DR15-restricted T-cell epitope has been defined. A DR15 specific inhibitor, PV-267, has potential as a targeted therapy, as current treatments are non-specific and have detrimental side effects. Using humanised HLA transgenic mice expressing DR15, this study tests the hypotheses that administration of PV-267 will inhibit autoreactivity to the immunodominant T cell epitope, alpha3135-145, and prevent disease in experimental autoimmune anti-GBM disease. Autoreactivity to alpha3135-145 was determined by immunizing mice with alpha3135-145, then measuring recall responses ex vivo 10 days later by [3H]-T proliferation and IFN-gamma and IL-17 ELISPOTs. Experimental anti-GBM disease was induced by immunizing DR15 transgenic mice (backcrossed onto an FcgammaRIIb-/- background) with three weekly injections of alpha3135-145, then functional and histological endpoints measured at 6 weeks. Compared with mice that received vehicle control, DR15 transgenic mice that received PV-267 daily (30mg/kg) from day -1 developed markedly reduced alpha3135-145-specific proliferation (SI: 9.5+/-0.9 vs 2.2+/-0.5, P< 0.001) as well as reduced numbers of IFN-gamma and IL-17 spots. In experimental anti-GBM disease, DR15 transgenic mice that received PV-267 (30mg/kg) on alternate days from day -1 had markedly reduced 24 hour albuminuria (mg: 1064+/-313 vs 42+/-29, P< 0.01) and reduced glomerular segmental necrosis and glomerular crescent formation. In conclusion, PV-267 effectively prevents experimental autoimmune anti-GBM disease, and highlights the potential for specific MHCII inhibitors as a targeted therapy for autoimmune disease.

The NLRP3 inflammasome is an intracellular platform that converts the pro-inflammatory cytokines interleukin (IL)-1beta and IL-18 to their active forms in response to 'danger' signals, which can be either host or pathogen derived, and mediates a form of inflammatory cell death called pyroptosis. This component of the innate immune system was initially discovered because of its role in rare autoinflammatory syndromes called cryopyrinopathies, but it has since been shown to mediate injurious inflammation in a broad range of diseases. Inflammasome activation occurs in both immune cells, primarily macrophages and dendritic cells, and in some intrinsic kidney cells such as the renal tubular epithelium. The NLRP3 inflammasome has been implicated in the pathogenesis of a number of renal conditions, including acute kidney injury, chronic kidney disease, diabetic nephropathy and crystal-related nephropathy. The inflammasome also plays a role in autoimmune kidney disease, as IL-1beta and IL-18 influence adaptive immunity through modulation of T helper cell subsets, skewing development in favour of Th17 and Th1 cells that are important in the development of autoimmunity. Both IL-1 blockade and two recently identified specific NLRP3 inflammasome blockers, MCC950 and beta-hydroxybutyrate, have shown promise in the treatment of inflammasome-mediated conditions. These targeted therapies have the potential to be of benefit in the growing number of kidney diseases in which the NLRP3 inflammasome has been implicated.Copyright © 2016 Asian Pacific Society of Nephrology

Toll-like receptor 9 (TLR9) enhances proinflammatory responses, but whether it can act in a regulatory capacity remains to be established. In experimental murine AKI induced by cisplatin, Tlr92/2 mice developed enhanced renal injury and exhibited fewer intrarenal regulatory T cells (Tregs) compared with genetically intact mice. A series of reconstitution and depletion studies defined a role for TLR9 in maintaining Treg-mediated homeostasis in cisplatin-induced AKI.When Rag12/2 mice were reconstituted with nonregulatory CD252 splenocytes from wild-type (WT) or Tlr92/2 mice, AKI was similarly enhanced. However, when Rag12/2 mice were reconstituted with CD4+CD25+ regulatory cells, WT CD4+CD25+ cells were more renoprotective and localized to the kidney more efficiently than Tlr92/2 CD4+CD25+ cells. In Tregdepleted Foxp3DTR mice, reconstitution with naive WT CD4+CD25+ cells resulted in less severe AKI than did reconstitution with Tlr92/2 Tregs. Tlr92/2 mice were not deficient in CD4+CD25+ cells, and WT and TLR9-deficient Tregs had similar suppressive function ex vivo. However, expression of adhesion molecules important in Treg trafficking was reduced on peripheral CD4+CD25+ cells from Tlr92/2 mice. In conclusion, we identified a pathway by which TLR9 promotes renal Treg accumulation in AKI.

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis is an autoimmune disease that manifests as focal and necrotizing glomerulonephritis and renal failure. Observations in patients suggest that CD8+ T cells participate in disease, but there is no experimental functional evidence of their pathological involvement. Myeloperoxidase (MPO) is a well defined autoantigen in ANCAassociated vasculitis and following ANCA-induced neutrophil localization, deposited MPO within glomeruli is recognized by autoreactive T-cells that contribute to injury. The current studies test the hypothesis that CD8+ T-cells mediate disease in experimental ANCAassociated vasculitis. CD8+ T-cells were depleted in experimental murine anti-MPO glomerulonephritis using monoclonal antibodies. Candidate CD8+ T-cell epitopes were identified in silico using the IEDB and their immunogenic and cytotoxicity assessed using flow cytometric tetramer based and cytotoxicity assays. The pathogenicity of MPO-specific CD8+ T-cells was determined by transferring Tcell clones into Rag1-/- mice. CD8+ T-cell depletion in the effector phase of disease attenuated injury in murine anti-MPO glomerulonephritis. This was associated with decreased intrarenal IFN-gamma and TNF-alpha, reduced inflammatory chemokines and fewer glomerular macrophages. A pathogenic CD8+ T-cell MPO epitope (MPO431-439) was identified and transferred MPO431-439-specific CD8+ T-cell clones exacerbated disease when co-transferred with MPO-specific CD4+ cells. Transfer of MPO431-439-specific CD8+ Tcells, without CD4+ T-cells, could mediate glomerular injury when MPO was planted in glomeruli. These results demonstrate a pathogenic role for MPO-specific CD8+ T-cells, provide evidence that CD8+ T-cells are a therapeutic target in ANCA-associated vasculitis and suggest that a molecular hot spot within the MPO molecule contains important CD8+, CD4+ and B cell epitopes.

Aim: To determine the therapeutic efficacy and mechanisms of action of anti- CD20 B cell monoclonal antibodies (mAb) in the treatment of murine autoimmune MPO-ANCA glomerulonephritis (anti-MPO GN). Background(s): Anti-CD20 treatment (with rituximab) is effective treatment for human anti-MPO GN. Its efficacy is attributed to B cell depletion. However, B cells also potentially play roles in immunoregulation and the initiation and maintenance of CD4 T cell autoimmunity. Method(s): Experimental anti-MPO autoimmunity was induced by MPO immunisation and GN triggered using a subnephritogenic dose of anti-GBM globulin. B cell depletion using mouse anti-CD20 mAb (or control mouse anti-IgG2a mAb) commenced after the induction of anti-MPO autoimmunity (day 14) and continued through the development of GN. Result(s): Administration of anti-CD20 mAb protected mice from the development of renal injury, compared to controls (segmental glomerular necrosis: 16 +/- 4 vs 44 +/- 4%, P < 0.01 and albuminuria: 221.0 +/- 81.6 vs 898.8 +/- 330.3 mug/24 hrs, P < 0.05). Attenuation of GN was associated with reduced systemic anti-MPO autoimmunity; serum anti-MPO IgG (ANCA) titres (0.21 +/- 0.02 vs 0.34 +/- 0.07 OD450nm, P < 0.05) and dermal MPO induced DTH swelling (0.07 +/- 0.02 vs 0.2 +/- 0.03DELTAmm, P < 0.01). Anti-CD20 mAb treatment decreased MPO specific recall proliferation in draining lymph node cells (104.5 +/- 12.7 vs 217.7 +/- 55.3 counts per minute, P < 0.05) with reduced frequency of IFN-gamma and IL-17A producing cells (ELISPOT; 22 +/- 6 vs 115 +/- 27 cells, P < 0.01 and 6 +/- 3 vs 40 +/- 18 cells, P < 0.05, respectively). Furthermore anti-CD20 treatment increased the proportion of proliferating Foxp3+ T regulatory cells (2.9 +/- 0.1 vs 1.7 +/- 0.1%, P < 0.001; 15% of proliferating Foxp3+ T cells in both groups produced IL-10). Conclusion(s): Anti-CD20 B cell directed immunotherapy suppresses anti-MPO autoimmunity and the development of GN by reducing the development of T and B c