Glomerulopathy induced by immunization with a peptide derived from the goodpasture antigen α3IV-NC1

Experimental models for elderly patients with membranous nephropathy: Application and advancements

Membranous nephropathy (MN) occurs predominantly in middle-aged and elderly individuals and ranks among the most prevalent etiologies of elderly nephrotic syndrome. As an autoimmune glomerular disorder characterized by glomerular basement membrane thickening and immune complex deposition, conventional MN animal models, including the Heymann nephritis rat model and the c-BSA mouse model, have laid a foundation for MN pathogenesis research. However, differences in target antigens between rodents and humans have impeded this work. In recent years, researchers have created antigen-specific MN animal models, primarily centered on PLA2R1 and THSD7A, employing diverse techniques that provide innovative in vivo research platforms for MN. Furthermore, significant advancements have been made in the development of in vitro podocyte models relevant to MN. This review compiles recent antigen-specific MN animal models and podocyte models, elucidates their immune responses and pathological characteristics, and offers insights into the future of MN experimental model development. Our aim is to provide a comprehensive resource for research into the pathogenesis of MN and the development of targeted therapies for older patients with MN to prolong lifespan and improve quality of life.

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

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

A comprehensive analysis of TDO2 expression in immune cells and characterization of immune cell phenotype in TDO2 knockout mice

Tryptophan 2,3-dioxygenase (TDO2) was an initial rate-limiting enzyme of the kynurenine (Kyn) pathway in tryptophan (Trp) metabolism. We undertook this study to determine a comprehensive analysis of TDO2 expression in immune cells and assess the characterization of immune cell phenotype in TDO2 knockout mice. The expression of TDO2 in various tissues of DBA/1 mice was detected by quantitative real-time PCR (qPCR) and immunohistochemistry. Both flow cytometry and immunofluorescence were used to analyze the expression of TDO2 in immune cells. Furthermore, TDO2 knockout (KO) mice were generated by CRISPR/Cas9 technology to detect immune cell phenotype. TDO2 protein level in liver was tested by western blot. High-performance liquid chromatography was used to detect the level of Trp and Kyn. Flow cytometry was used to test the proportions of splenic lymphocyte subsets in wild-type (WT) and TDO2 KO mice. We found that TDO2 was expressed in various tissues and immune cells, and TDO2 staining was mainly observed in the cytoplasm of cells. There was no difference in the development of immune cells between TDO2 KO mice and WT mice, including T cells, B cells, memory B cells, plasma cells, dendritic cells, and natural killer cells. Interestingly, the reduced M1/M2 ratio was observed in the peritoneal macrophages of TDO2 KO mice. Taken together, these findings enriched the known expression profile of TDO2, especially its expression in immune cells. Our study suggested that TDO2-mediated Trp-Kyn metabolism pathway might be involved in the immune response.

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.

Advances of the experimental models of idiopathic membranous nephropathy (Review)

Idiopathic membranous nephropathy (IMN) is one of the main types of chronic kidney disease in adults and one of the most common causes of end-stage renal disease. In recent years, the morbidity of IMN among primary glomerular diseases has markedly increased, while the pathogenesis of the disease remains unclear. To address this, a number of experimental models, including Heymann nephritis, anti-thrombospondin type-1 domain-containing 7A antibody-induced IMN, cationic bovine serum albumin, anti-human podocyte antibodies and zymosan-activated serum-induced C5b-9, have been established. This review comprehensively summarized the available animal and cell models for IMN. The limitations and advantages of the current models were discussed and two improved models were introduced to facilitate the selection of an appropriate model for further studies on IMN.

Intestinal transcriptional profiling reveals fava bean-induced immune response in DBA/1 mice

Background

Fava beans (FBs) have long been used as food, and their principal disadvantage is derived from their haemotoxicity. We hypothesized that FB ingestion alters the intestinal gene expression pattern, thereby inducing an immune response.

Results

In-depth sequence analysis identified 769 differentially expressed genes (DEGs) associated with the intestine in FB-treated DBA/1 mouse intestines. The identified genes were shown to be associated with biological processes (such as response to stimulus and immune system processes), human disease pathways (such as infectious diseases, endocrine and metabolic diseases, and immune diseases), and organismal system pathways (such as the digestive system, endocrine system, environmental adaptation, and immune system). Moreover, plasma total immunoglobulin E (IgE), histamine, interleukin (IL)-4 and IL-13 levels were significantly increased when the mice were treated with FBs.

Conclusions

These results demonstrated that FBs affect the intestinal immune response and IgE and cytokine secretion in DBA/1 mice.

Electronic supplementary material

The online version of this article (10.1186/s40659-019-0216-9) contains supplementary material, which is available to authorized users.

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.

Alternative Pathway Is Essential for Glomerular Complement Activation and Proteinuria in a Mouse Model of Membranous Nephropathy

Membranous nephropathy is an immune kidney disease caused by IgG antibodies that form glomerular subepithelial immune complexes. Proteinuria is mediated by complement activation, as a result of podocyte injury by C5b-9, but the role of specific complement pathways is not known. Autoantibodies-mediating primary membranous nephropathy are predominantly of IgG4 subclass, which cannot activate the classical pathway. Histologic evidence from kidney biopsies suggests that the lectin and the alternative pathways may be activated in membranous nephropathy, but the pathogenic relevance of these pathways remains unclear. In this study, we evaluated the role of the alternative pathway in a mouse model of membranous nephropathy. After inducing the formation of subepithelial immune complexes, we found similar glomerular IgG deposition in wild-type mice and in factor B-null mice, which lack a functional alternative pathway. Unlike wild-type mice, mice lacking factor B did not develop albuminuria nor exhibit glomerular deposition of C3c and C5b-9. Albuminuria was also reduced but not completely abolished in C5-deficient mice. Our results provide the first direct evidence that the alternative pathway is necessary for pathogenic complement activation by glomerular subepithelial immune complexes and is, therefore, a key mediator of proteinuria in experimental membranous nephropathy. This knowledge is important for the rational design of new therapies for membranous nephropathy.

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.

The Effects of Tumstatin on Vascularity, Airway Inflammation and Lung Function in an Experimental Sheep Model of Chronic Asthma

Tumstatin, a protein fragment of the alpha-3 chain of Collagen IV, is known to be significantly reduced in the airways of asthmatics. Further, there is evidence that suggests a link between the relatively low level of tumstatin and the induction of angiogenesis and inflammation in allergic airway disease. Here, we show that the intra-segmental administration of tumstatin can impede the development of vascular remodelling and allergic inflammatory responses that are induced in a segmental challenge model of experimental asthma in sheep. In particular, the administration of tumstatin to lung segments chronically exposed to house dust mite (HDM) resulted in a significant reduction of airway small blood vessels in the diameter range 10⁺–20 μm compared to controls. In tumstatin treated lung segments after HDM challenge, the number of eosinophils was significantly reduced in parenchymal and airway wall tissues, as well as in the bronchoalveolar lavage fluid. The expression of VEGF in airway smooth muscle was also significantly reduced in tumstatin-treated segments compared to control saline-treated segments. Allergic lung function responses were not attenuated by tumstatin administration in this model. The data are consistent with the concept that tumstatin can act to suppress vascular remodelling and inflammation in allergic airway disease.