Analysis of T cell responses to the autoantigen in Goodpasture's disease

Prognostic value of complement serum C3 level and glomerular C3 deposits in anti-glomerular basement membrane disease

Background and objectives

Activation of the complement system is involved in the pathogenesis of anti-glomerular basement membrane (anti-GBM) disease. Glomerular deposits of complement 3 (C3) are often detected on kidney biopsies. The primary objective of this study was to analyze the prognostic value of the serum C3 level and the presence of C3 glomerular deposits in patients with anti-GBM disease.

Methods

We conducted a retrospective cohort study of 150 single-positive patients with anti-GBM disease diagnosed between 1997 and 2017. Patients were categorized according to the serum C3 level (forming a low C3 (C3<1.23 g/L) and a high C3 (C3≥1.23 g/L) groups) and positivity for C3 glomerular staining (forming the C3+ and C3- groups). The main outcomes were kidney survival and patient survival.

Results

Of the 150 patients included, 89 (65%) were men. The median [interquartile range (IQR)] age was 45 [26-64]. At diagnosis, kidney involvement was characterized by a median [IQR] peak serum creatinine (SCr) level of 578 [298-977] µmol/L, and 106 (71%) patients required dialysis. Patients in the low C3 group (72 patients) had more severe kidney disease at presentation, as characterized by higher prevalences of oligoanuria, peak SCr ≥500 µmol/L (69%, vs. 53% in the high C3 group; p=0.03), nephrotic syndrome (42%, vs. 24%, respectively; p=0.02) and fibrous forms on the kidney biopsy (21%, vs. 8%, respectively; p=0.04). Similarly, we observed a negative association between the presence of C3 glomerular deposits (in 52 (41%) patients) and the prevalence of cellular forms (83%, vs. 58% in the C3- group; p=0.003) and acute tubulo-interstitial lesions (60%, vs. 36% in the C3- group; p=0.007). When considering patients not on dialysis at diagnosis, the kidney survival rate at 12 months was poorer in the C3+ group (50% [25-76], vs. 91% [78-100] in the C3- group; p=0.01), with a hazard ratio [95% confidence interval] of 5.71 [1.13-28.85] (p=0.04, after adjusting for SCr).

Conclusion

In patients with anti-GBM disease, a low serum C3 level and the presence of C3 glomerular deposits were associated with more severe disease and histological kidney involvement at diagnosis. In patients not on dialysis at diagnosis, the presence of C3 deposits was associated with worse kidney survival.

Case Report: Eculizumab and ECMO Rescue Therapy of Severe ARDS in Goodpasture Syndrome

Introduction: Goodpasture's syndrome is a life-threatening autoimmune type IV collagen disease characterized by the presence anti-glomerular basement membrane antibodies, rapid progressive glomerulonephritis and/or pulmonary hemorrhage. Methods: Here, we describe new therapeutic options, which take recent advances in unraveling Goodpasture's pathogenesis into account. Results: In a 17-year old male, severe Goodpasture's syndrome resulted in acute respiratory distress syndrome (ARDS). Within 1 day after hospital admission, the patient required extracorporeal membrane oxygenation (ECMO). Despite steroid-pulse and plasmapheresis, ARDS further deteriorated. Eleven days after admission, the patient was in a pre-final stage. At last, we decided to block the complement-driven lung damage by Eculizumab. Three days after, lung-failure has stabilized in a way allowing us to initiate Cyclophosphamide-therapy. As mechanical ventilation further triggers Goodpasture-epitope exposure, the patient was taken from pressure support - breathing spontaneously by the help of maintaining ECMO therapy. After a total of 24 days, ECMO could be stopped and pulmonary function further recovered. Conclusions: In conclusion, our findings suggest that life-threatening organ-damage in Goodpasture's syndrome can be halted by Eculizumab as well as by lung-protective early withdrawal from pressure support by the help of ECMO. Both therapeutic options serve as new tools in otherwise hopeless situations to prevent further organ-damage and to gain time until the established immunosuppressive therapy works in otherwise lethal autoimmune-diseases.

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.

T cell responses to peptides of Goodpasture autoantigen in patients with anti-glomerular basement membrane disease

AIM

Cell-mediated autoimmunity, especially autoreactive T cells, is crucial in the initiation of anti-glomerular membrane (GBM) disease. Epitopes for T cells on Goodpasture autoantigen are not fully defined. This study investigated T cell epitopes in anti-GBM patients, aiming to identify the epitopes and their clinical significance.

METHODS

Peripheral blood mononuclear cells (PBMC) were collected from 13 patients with anti-GBM disease. Twenty-four overlapping linear peptides were synthesized covering the whole sequence of human α3(IV)NC1. PBMC response to each peptide was detected by proliferation assay. Their associations with clinical features were further analyzed.

RESULTS

Peripheral blood mononuclear cells proliferative responses to linear peptides on α3(IV)NC1 could be detected in all patients. Five major epitopes were identified as stimulatory in over half of the patients: α3(IV)NC1_127-148 (P14) (69.2%), α3(IV)NC1_159-178 (77.8%), α3(IV)NC1_179-198 (55.6%), α3(IV)NC1_189-208 (P19) (75.0%) and α3(IV)NC1_141-154 (57.1%). P14 and P19 were highly recognized in patients comparing with healthy controls (69.2% vs. 0.0%, P = 0.011; 75.0% vs. 0.0%, P = 0.021, respectively).

CONCLUSION

T cell proliferation to linear epitopes was detected in human anti-GBM disease. α3_127-148 was a mutual T and B cell epitope, implying its initial role in epitope spreading process.

Anti-Glomerular Basement Membrane Disease

Anti-glomerular basement membrane (anti-GBM) disease is a rare small vessel vasculitis that affects the capillary beds of the kidneys and lungs. It is an archetypic autoimmune disease, caused by the development of directly pathogenic autoantibodies targeting a well characterized autoantigen expressed in the basement membranes of these organs, although the inciting events that induce the autoimmune response are not fully understood. The recent confirmation of spatial and temporal clustering of cases suggests that environmental factors, including infection, may trigger disease in genetically susceptible individuals. The majority of patients develop widespread glomerular crescent formation, presenting with features of rapidly progressive GN, and 40%-60% will have concurrent alveolar hemorrhage. Treatment aims to rapidly remove pathogenic autoantibody, typically with the use of plasma exchange, along with steroids and cytotoxic therapy to prevent ongoing autoantibody production and tissue inflammation. Retrospective cohort studies suggest that when this combination of treatment is started early, the majority of patients will have good renal outcome, although presentation with oligoanuria, a high proportion of glomerular crescents, or kidney failure requiring dialysis augur badly for renal prognosis. Relapse and recurrent disease after kidney transplantation are both uncommon, although de novo anti-GBM disease after transplantation for Alport syndrome is a recognized phenomenon. Copresentation with other kidney diseases such as ANCA-associated vasculitis and membranous nephropathy seems to occur at a higher frequency than would be expected by chance alone, and in addition atypical presentations of anti-GBM disease are increasingly reported. These observations highlight the need for future work to further delineate the immunopathogenic mechanisms of anti-GBM disease, and how to better refine and improve treatments, particularly for patients presenting with adverse prognostic factors.

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.

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.

Goodpasture's disease following extracorporeal shock wave lithotripsy: a case report & literature review

Shock wave lithotripsy may unmask epitopes within the glomerular basement membrane, leading to the formation of anti-glomerular basement membrane (GBM) antibodies and clinical disease in susceptible individuals. Although rare, our case highlights the need for vigilant monitoring of renal function following extracorporeal shock wave lithotripsy. This may allow for early recognition, treatment and improved outcome of anti-GBM disease.

Update on crescentic glomerulonephritis

The recent years have seen a number of major progresses in the field of extracapillary glomerulonephritis. This entity is the final damage caused by unrelated immunological disorders such as immune complexes glomerular deposits or microvascular injury caused by proinflammatory cytokines, neutrophil extracellular traps (NET), and cell adhesion molecules in the context of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). This review provides a summary of recent advances in the understanding of crescentic glomerulonephritis, focusing on interplays of local immune cells and on local mediators participating to crescent formation especially in anti-glomerular basement membrane (anti-GBM) antibody disease. The recent advances about AAV and lupus nephritis are covered by other chapters of this issue. Nevertheless, these considerations may apply to the general case of crescentic glomerulonephritis of all causes.

Genetic susceptibility to experimental autoimmune glomerulonephritis in the Wistar Kyoto rat

In experimental autoimmune glomerulonephritis (EAG), a model of Goodpasture's disease, Wistar Kyoto (WKY) rats immunized with collagenase-solubilized glomerular basement membrane (GBM) or the recombinant NC1 domain of the α3 chain of type IV collagen [α3(IV)NC1] develop anti-GBM antibodies and focal necrotizing glomerulonephritis with crescent formation. However, Lewis (LEW) rats, which share the same major histocompatibility complex (MHC) haplotype, are resistant to EAG development. A genome-wide linkage analysis of backcrossed animals with EAG revealed a major quantitative trait locus (QTL) on rat chromosome 13 (LOD = 3.9) linked to the percentage of glomerular crescents. To investigate the role of this QTL in EAG induction, reciprocal congenic rats were generated (LEW.WCrgn1 congenic and WKY.LCrgn1 congenic), immunized with recombinant rat α3(IV)NC1, and assessed for EAG development. WKY.LCrgn1 rats showed a marked reduction in albuminuria, severity of crescentic nephritis, and number of glomerular macrophages compared with WKY controls. No reduction in antibody levels was observed. However, LEW.WCrgn1 rats were resistant to EAG development, as were LEW controls. Macrophage activation in vitro was assessed in parental and congenic rat bone marrow-derived macrophages (BMDMs). WKY.LCrgn1 BMDMs showed a significant reduction in Fc receptor-mediated oxidative burst, phagocytosis of opsonised polystyrene beads, and LPS-induced levels of MCP-1 secretion and iNOS mRNA expression compared with WKY rats. These results confirm the importance of Crgn1 on chromosome 13 in EAG susceptibility, mediated partly through differences in Fc receptor-mediated macrophage activation.

Genetic elimination of α3(IV) collagen fails to rescue anti-collagen B cells

Organ deposition of autoantibodies against the noncollagenous-1 domain of the α3 chain of type IV collagen leads to severe kidney and lung injury in anti-glomerular basement membrane disease. The origin and regulation of these highly pathogenic autoantibodies remains unknown. Anti-α3(IV) collagen B lymphocytes are predicted to mature in vivo ignorant of target antigen because α3(IV) collagen expression is highly tissue restricted and pathogenic epitopes are cryptic. However, a recent analysis of an anti-α3(IV)NC1 collagen autoantibody transgenic mouse model revealed that developing B cells are rapidly silenced by deletion and editing in the bone marrow. To dissect the role of collagen as central tolerogen in this model, we determined B cell fate in autoantibody transgenic mice genetically lacking α3(IV) collagen. We found that absence of the tissue target autoantigen has little impact on the fate of anti-α3(IV)NC1 B cells. This implies a more complex regulatory mechanism for preventing anti-glomerular basement membrane disease than has been previously considered, including the possibility that a second antigen present in bone marrow engages and tolerizes anti-α3(IV)NC1 collagen B cells.

Central tolerance regulates B cells reactive with Goodpasture antigen alpha3(IV)NC1 collagen

Patients and rodents with Goodpasture's syndrome (GPS) develop severe autoimmune crescentic glomerulonephritis, kidney failure, and lung hemorrhage due to binding of pathogenic autoantibodies to the NC1 domain of the alpha3 chain of type IV collagen. Target epitopes are cryptic, normally hidden from circulating Abs by protein-protein interactions and the highly tissue-restricted expression of the alpha3(IV) collagen chain. Based on this limited Ag exposure, it has been suggested that target epitopes are not available as B cell tolerogens. To determine how pathogenic anti-GPS autoantibody responses are regulated, we generated an Ig transgenic (Tg) mouse model that expresses an Ig that binds alpha3(IV)NC1 collagen epitopes recognized by serum IgG of patients with GPS. Phenotypic analysis reveals B cell depletion and L chain editing in Tg mice. To determine the default tolerance phenotype in the absence of receptor editing and endogenous lymphocyte populations, we crossed Tg mice two generations with mice deficient in Rag. Resulting Tg Rag-deficient mice have central B cell deletion. Thus, development of Tg anti-alpha3(IV)NC1 collagen B cells is halted in the bone marrow, at which point the cells are deleted unless rescued by a Rag enzyme-dependent process, such as editing. The central tolerance phenotype implies that tolerizing self-Ag is expressed in bone marrow.

Experimental anti-GBM disease as a tool for studying spontaneous lupus nephritis

Lupus nephritis is an immune-mediated disease, where antibodies and T cells both play pathogenic roles. Since spontaneous lupus nephritis in mouse models takes 6-12 months to manifest, there is an urgent need for a mouse model that can be used to delineate the pathogenic processes that lead to immune nephritis, over a quicker time frame. We propose that the experimental anti-glomerular basement membrane (GBM) disease model might be a suitable tool for uncovering some of the molecular steps underlying lupus nephritis. This article reviews the current evidence that supports the use of the experimental anti-GBM nephritis model for studying spontaneous lupus nephritis. Importantly, out of about 25 different molecules that have been specifically examined in the experimental anti-GBM model and also spontaneous lupus nephritis, all influence both diseases concordantly, suggesting that the experimental model might be a useful tool for unraveling the molecular basis of spontaneous lupus nephritis. This has important clinical implications, both from the perspective of genetic susceptibility as well as clinical therapeutics.

Zebrafish to humans: evolution of the alpha3-chain of type IV collagen and emergence of the autoimmune epitopes associated with Goodpasture syndrome

Goodpasture syndrome is an autoimmune vascular disease associated with kidney and lung failure, with pathogenic circulating autoantibodies targeted to a set of discontinuous epitope sequences within the noncollagenous domain-1 (NC1) of the alpha3 chain of type IV collagen (alpha3(IV)NC1), the Goodpasture autoantigen. We demonstrate that basement membrane extracted NC1 domain preparations from Caenorhabditis elegans, Drosophila melanogaster, and Danio rerio do not bind Goodpasture autoantibodies, while Xenopus laevis, chicken, mouse and human alpha3(IV)NC1 domains bind autoantibodies. The alpha3(IV) chain is not present in C elegans and Drosophila melanogaster, but is first detected in the Danio rerio. Interestingly, native Danio rerio alpha3(IV)NC1 does not bind Goodpasture autoantibodies. Next, we cloned, sequenced, and generated recombinant Danio rerio alpha3(IV)NC1 domain. In contrast to recombinant human alpha3(IV)NC1 domain, there was complete absence of autoantibody binding to recombinant Danio rerio alpha3(IV)NC1. Three-dimensional molecular modeling from existing x-ray coordinates of human NC1 domain suggest that evolutionary alteration of electrostatic charge and polarity due to the emergence of critical serine, aspartic acid, and lysine residues, accompanied by the loss of asparagine and glutamine, contributes to the emergence of the 2 major Goodpasture epitopes on the human alpha3(IV)NC1 domain, as it evolved from the Danio rerio over 450 million years.

Experimental autoimmune Goodpasture's disease: a pathogenetic role for both effector cells and antibody in injury

BACKGROUND

Goodpasture's disease [antiglomerular basement membrane (GBM) glomerulonephritis] is a classic autoimmune disease and the only organ-specific autoimmune renal disease in which the antigen is well described. The importance of antibodies against the non-collagenous domain of the alpha3 chain of type IV collagen [alpha3(IV)NC1] is well established. However, observational human studies and studies in experimental systems also imply a role for cell-mediated effector injury.

METHODS

Active experimental autoimmune glomerulonephritis (EAG) was induced by immunization with alpha3-alpha5(IV)NC1 heterodimers in B cell intact C57BL/6 mice and B cell (mu chain-deficient) mice. Passive disease was induced by transferring sera from B cell intact and B cell deficient mice with EAG to RAG-1-/- mice (that lack adaptive immunity). Histologic and functional injury was studied.

RESULTS

Despite the absence of B cells and immunoglobulin in B-cell-deficient mice, histologic and functional injury developed in mice immunized with alpha3-alpha5(IV)NC1, with T cells and macrophages in glomeruli. Injury occurred to a similar degree to that found in B-cell-intact mice. Transfer of sera from B-cell-intact mice with EAG containing antibodies (but not from B-cell-deficient mice with EAG) to RAG-1-/- mice induced linear immunoglobulin deposits on the glomerular basement membrane (GBM) and pathologic proteinuria.

CONCLUSION

Both cell-mediated and humoral effectors are capable of inducing renal injury in EAG. Given the similarity of the disease-initiating antigen in this model to the antigen in human anti-GBM glomerulonephritis, similar overlapping mechanisms are likely to operate in human disease.

Glomerular T Cells Are of Restricted Clonality and Express Multiple CDR3 Motifs across Different Vβ T-Cell Receptor Families in Experimental Autoimmune Glomerulonephritis

Experimental autoimmune glomerulonephritis (EAG) is an animal model of Goodpasture's disease which can be induced in Wistar-Kyoto (WKY) rats by a single intramuscular injection of collagenase-digested rat glomerular basement membrane (GBM) in adjuvant. This model is characterised by anti-GBM antibody production, accompanied by focal necrotising glomerulonephritis with crescent formation and glomerular infiltration by T cells and macrophages. Previous work has shown that EAG is a T-cell-dependent disease. We proposed that intraglomerular T cells might be directly involved in pathogenesis and would be oligoclonal. In this study, EAG was induced by standard methods, the kidneys perfused with saline at week 2 and week 4, and the glomeruli separated by a sieving method. Glomerular RNA was extracted and reverse transcribed. RT-PCR showed overexpression of an average of two Vbeta families in each kidney analysed. However, no predominant single Vbeta family was overexpressed in any of the experimental animals. CDR3 spectratyping of Fam-labelled PCR products showed a marked restriction involving different Vbeta families. Sequencing demonstrated multiple CDR3 motifs, each expressed in association with different Vbeta gene segments. Our results show that glomerular T cells are of restricted clonality and suggest a role for antigen-specific effector T cells in the pathogenesis of EAG.

Pathogenesis of Goodpasture syndrome: a molecular perspective

Goodpasture (GP) syndrome is a form of anti-glomerular basement membrane (GBM) disease, in which autoantibodies bind to alpha3(IV) collagen in GBM causing rapidly progressive glomerulonephritis and pulmonary hemorrhage. The conformational GP epitopes have been mapped to 2 regions within the noncollagenous (NC1) domain of the alpha3(IV) chain. Recently, we described the molecular organization of the autoantigen in the native alpha3alpha4alpha5(IV) collagen network of the GBM. The crystal structure of the NC1 domain has revealed how the GP epitopes are sequestered in the native GBM. Further insight into the pathogenesis of disease has been obtained from better animal models. These advances provide a foundation for the development of new specific therapies.

Regulation by CD25+ lymphocytes of autoantigen-specific T-cell responses in Goodpasture's (anti-GBM) disease

BACKGROUND

Goodpasture's, or anti-glomerular basement membrane (GBM), disease is unusual among autoimmune diseases in that it rarely follows a relapsing-remitting course. Moreover, untreated, autoantibodies disappear spontaneously after 1 to 3 years and, following treatment, autoreactive T cells diminish in frequency. This suggests that operational tolerance toward the autoantigen is reestablished. However, the mechanisms underlying this have remained unclear. Recent data have suggested that a population of regulatory T lymphocytes can suppress both autoimmune and alloimmune responses in animal models and are present in normal individuals. However, to date, they have not been demonstrated to play a role in human renal autoimmune disease.

METHODS

We studied the role of regulatory CD25+ cells in suppressing T-cell responses to the Goodpasture autoantigen in nine patients with Goodpasture's disease.

RESULTS

At the time of acute presentation, there was no evidence of a regulatory cell population. However, from 3 months onward a population emerged, capable of suppressing the response to the Goodpasture autoantigen. Following depletion of CD25+ cells, the frequencies of autoreactive-, GBM-, or collagen alpha 3(IV)NC1-specific T cells were significantly increased (P = 0.031 by paired t test), with five of seven (71%) convalescent patients and no acute patients demonstrating regulation.

CONCLUSION

These data demonstrate that, in Goodpasture's disease, regulatory CD25+ T cells play a role in inhibiting the autoimmune response. Their emergence and persistence may underlie the "single hit" nature of this condition. Understanding the conditions required for the development and propagation of these cells would allow development of novel therapeutic strategies for inducing hyporesponsiveness in autoimmune disease.

The evolution of crescentic nephritis and alveolar haemorrhage following induction of autoimmunity to glomerular basement membrane in an experimental model of Goodpasture's disease

Goodpasture's, or anti-glomerular basement membrane (GBM), disease presents with rapidly progressive glomerulonephritis and lung haemorrhage, and is caused by autoimmunity to the NC1 domain of the alpha3 chain of type IV collagen (alpha3(IV)NC1). This study examines the development of crescentic nephritis and alveolar haemorrhage in a model of Goodpasture's disease, experimental autoimmune glomerulonephritis (EAG), induced in WKY rats by immunization with rat GBM in adjuvant. An increase in circulating anti-GBM antibodies and albuminuria was observed by week 2, which increased further by weeks 3 and 4, while a decrease in creatinine clearance was observed by week 2, which decreased further by weeks 3 and 4. The kidneys of animals with EAG showed linear deposits of IgG on the GBM and a transient glomerular infiltration by CD4+ T cells at week 2. By week 3 there were large deposits of fibrin in Bowman's space, and glomerular infiltration by CD8+ T cells and macrophages, accompanied by focal necrotizing glomerulonephritis with crescent formation. Ultrastructural studies showed glomerular endothelial cell swelling and epithelial cell foot process effacement at week 2. As the lesion progressed, capillary loops became occluded and the mesangium became expanded by mononuclear cells. By week 3 there was detachment of the endothelium from the GBM, and accumulation of fibrin beneath the disrupted endothelial cells and in Bowman's space. Occasional breaks were observed in the continuity of the basement membrane, and cytoplasmic projections from infiltrating mononuclear cells could be seen crossing the capillary wall between the lumen and the crescent. The lungs of animals with EAG showed patchy binding of IgG to the alveolar basement membrane (ABM) at week 2, and infiltration of the interstitium by CD8+ T cells and macrophages by weeks 3 and 4, accompanied by both interstitial and alveolar haemorrhage. Ultrastructural studies showed focal mononuclear cell infiltrates in alveolar walls at week 2. Occasional breaks were observed in the basement membrane and adjacent endothelium by weeks 3 and 4, together with accumulation of surfactant and erythrocytes within the alveolar spaces. This study defines for the first time the relationship between the immunological and pathological events during the evolution of EAG, and provides the basis for further work on the pathogenesis of Goodpasture's disease.

Immunology of anti-glomerular basement membrane disease

Anti-glomerular basement membrane disease is a form of autoimmune glomerulonephritis often accompanied by lung haemorrhage. It is characterized by circulating and deposited antibodies that bind basement membrane components in the glomerulus and lung alveolus. Since early descriptions of the deposition of immunoglobulin on the glomerular basement membrane, work has focused on the binding properties of the autoantibodies, and this has led to the identification of the autoantigen as the non-collagenous region of the alpha 3 chain of type IV collagen. Despite being thought of as a prototypic antibody mediated autoimmune disease, it is becoming apparent that both humoral and cellular immune mechanisms act in concert to initiate and perpetuate disease. Recent data have shed light on the molecular pathogenesis of anti-glomerular basement membrane disease and provided a more complete framework on which to build our understanding of autoimmune renal disease. This should lead to novel approaches to immunotherapy for patients with glomerulonephritis.

CD4(+) T cells specific to a glomerular basement membrane antigen mediate glomerulonephritis

Ab-mediated mechanisms have been considered the major causes of glomerulonephritis (GN). However, recent studies suggest that T cells may be more important in mediating GN. To investigate the effects of antigen-specific CD4(+) T cells, we generated Th1 cell lines specific for this antigen from rats that had been immunized with a recombinant form of the glomerular basement membrane (GBM) antigen, Col4alpha3NC1. Upon the transfer of in vitro-activated T cell lines to pertussis toxin-primed, naive syngeneic rats, the recipients developed severe proteinuria/albuminuria, which plateaued after approximately 35 days. Although no IgG binding to GBM or C3 deposition could be detected by immunofluorescence, five out of eleven rats exhibited severe GN, as judged by the formation of characteristic crescent-shaped lesions in the glomeruli, whereas the others exhibited modest GN. Thus Col4alpha3NC1-specific T cells directly initiated glomerular injury in the recipients. One notable difference from GN induced by active immunization was a T cell infiltration in the renal interstitium, which affected some tubules. We therefore injected fluorescence-labeled Col4alpha3NC1-specific into naive rats, and we found that they were enriched 4.5-fold in the kidney cortex relative to nonspecific control T cells 24 hours later. Many of the T cells were located in the Bowman's space and had a flattened shape, suggesting that the primary target for the T cells was in or adjacent to the Bowman's capsule.

Expression and characterization of recombinant rat alpha 3(IV)NC1 and its use in induction of experimental autoimmune glomerulonephritis

BACKGROUND

The autoantigen in Goodpasture's disease is known to be the non-collagenous domain of the alpha3 chain of type IV collagen, alpha 3(IV)NC1. There is mounting evidence that alpha 3(IV)NC1 is also a target of autoimmunity in experimental autoimmune glomerulonephritis (EAG). Sado et al. [Kidney Int 1998; 53, 664-671] have reported that recombinant human alpha 3(IV)NC1 and alpha4(IV)NC1 are nephritogenic in WKY rats. We have proposed that immunization with homologous antigen is more appropriate for detailed investigation of autoimmunity in EAG.

METHODS

To this end, we have cloned and sequenced rat alpha 3(IV)NC1 and expressed it in COS-7 cells. Recombinant rat alpha 3(IV)NC1, secreted into the COS-7 cell supernatant, was purified on an anti-M2 FLAG affinity column and characterized by western blotting. Recombinant antigen was then used to immunize WKY rats, in order to induce EAG.

RESULTS

The recombinant material was antigenic as judged by binding to sera from patients with Goodpasture's disease and a mAb to alpha 3(IV)NC1. Immunization of WKY rats (n=5), with recombinant rat alpha 3(IV)NC1 in FCA at a dose of 1 mg/kg resulted in circulating anti-GBM antibodies directed towards alpha 3(IV)NC1, linear deposits of IgG on the GBM, albuminuria, deposits of fibrin in the glomeruli, severe focal necrotizing glomerulonephritis with crescent formation, and glomerular influx of CD8+ T cells and macrophages. Western blot analysis demonstrated that sera from these rats bound strongly to recombinant rat alpha 3(IV)NC1, as well as to collagenase-solubilized human and rat GBM. The pattern of binding was indistinguishable from that of sera from patients with Goodpasture's disease.

CONCLUSIONS

This purified recombinant rat alpha 3(IV)NC1, which is both antigenic and nephritogenic, will be of value in analysing autoimmune responses in experimental anti-GBM disease.

Helper T cells in antibody-mediated, organ-specific autoimmunity

The production of pathogenic autoantibodies in organ-specific autoimmune diseases is largely T cell dependent. For many of these diseases, the precise specificities and cytokine profiles of the T cells that respond to the corresponding autoantigens have now been identified. This knowledge has been exploited to treat some models of antibody-mediated autoimmunity using peptides corresponding to the dominant helper epitopes, giving impetus to the development of a similar approach in the equivalent human diseases.

Properties of HLA class II molecules divergently associated with Goodpasture's disease

Goodpasture's disease provides an opportunity to analyse molecular mechanisms that may underlie MHC class II associations with autoimmune disease because it is caused by autoimmunity to a defined antigen [the 230 amino acid NC1 domain of the alpha3 chain of type IV collagen (alpha3(IV)NC1)] and has strong HLA class II associations. We compared the alpha3(IV)NC1 peptide binding of class II molecules with strong positive (DR15) and dominant negative (DR7/1) associations using an inhibition binding assay and short synthetic peptides spanning the sequence of alpha3(IV)NC1. DR15 in general bound the peptides with low affinity (three of 23 < 100 nM) compared to DR1 and DR7 (12 and 10 < 100 nM respectively), and no peptide bound DR15 with much higher affinity (>10-fold) than both DR1 and DR7. Thus DR15 molecules are unlikely to increase susceptibility to Goodpasture's disease by presenting a particular alpha3(IV)NC1-derived peptide uniquely well and DR1/7 are unlikely to protect by their inability to present particular peptides. However DR1/7 could protect by capturing alpha3(IV)NC1 peptides and preventing their display bound to DR15; the binding data suggest that all the major (biochemically detectable) alpha3(IV)NC1 peptides presented bound to DR15 by DR15 homozygous antigen-presenting cells (APC) would bind preferentially to DR1/7 in DR15, 1/7 heterozygote APC.

Sequential development of pulmonary hemorrhage with MPO-ANCA complicating anti-glomerular basement membrane antibody-mediated glomerulonephritis

We report a case of rapidly progressive glomerulonephritis caused by anti-glomerular basement membrane (anti-GBM) antibodies that progressed to end-stage renal disease in a 67-year-old woman with diabetes. Intensive combined immunosuppressive therapy with methylprednisolone bolus, oral prednisone, and cyclophosphamide led to negativity of anti-GBM antibodies but was not able to restore renal function. After 28 months of hemodialysis, the patient suddenly presented with pulmonary hemorrhage. In this setting, high levels of myeloperoxidase (MPO)-antineutrophil cytoplasmic antibody (ANCA) and negative anti-GBM antibodies were found. Therapy with oral prednisone and cyclophosphamide led to resolution of pulmonary hemorrhage and negativity of MPO-ANCA.

De Novo Autoimmunity to Cardiac Myosin After Heart Transplantation and Its Contribution to the Rejection Process

Allograft rejection is initiated by an immune response to donor MHC proteins. We recently reported that this response can result in breakdown of immune tolerance to a recipient self Ag. However, the contribution of this autoimmune response to graft rejection has yet to be determined. Here, we found that after mouse allogeneic heart transplantation, de novo CD4+ T cell and B cell autoimmune response to cardiac myosin (CM), a major contractile protein of cardiac muscle, is elicited in recipients. Importantly, CM is the autoantigen that causes autoimmune myocarditis, a heart autoimmune disease whose histopathological features resemble those observed in rejected cardiac transplants. Furthermore, T cell responses directed to CM peptide myhcα 334–352, a known myocarditogenic determinant, were detected in heart-transplanted mice. No responses to CM were observed in mice that had received an allogeneic skin graft or a syngeneic heart transplant, demonstrating that this response is tissue specific and that allogeneic response is necessary to break tolerance to CM. Next, we showed that sensitization of recipient mice with CM markedly accelerates the rejection of allogeneic heart. Therefore, posttransplant autoimmune response to CM is relevant to the rejection process. We conclude that transplantation-induced autoimmune response to CM represents a new mechanism that may play a significant role in cardiac transplant rejection.

Th1 and Th2 T helper cell subsets affect patterns of injury and outcomes in glomerulonephritis

The recognition that human immune responses can be directed by two different subsets of T helper cells (Th1 and Th2) has been an important development in modern immunology. Immune responses polarized by either the Th1 or Th2 subset predominance result in different inflammatory effector pathways and disease outcomes. Many autoimmune diseases are associated with either Th1- or Th2- polarized immune responses. Although these different immune response patterns are relevant to glomerulonephritis (GN), little attention has been paid to the consequences of Th1 or Th2 predominance of nephritogenic immune responses for the pattern and outcome of GN. Unlike other autoimmune conditions, GN results from a variety of different immune responses and has a range of histologic features and immune effectors in glomeruli. This review assesses the data available from studies of experimental and human GN that address the Th1 or Th2 predominance of nephritogenic immune responses and their relevance to the different histopathological patterns and outcomes of GN. In particular, the evidence that Th1-predominant nephritogenic immune responses are associated with severe proliferative and crescentic GN is presented.

Susceptibility to anti-glomerular basement membrane disease and Goodpasture syndrome is linked to MHC class II genes and the emergence of T cell-mediated immunity in mice

We developed a new mouse model of human anti-glomerular basement membrane (GBM) disease to better characterize the genetic determinants of cell-mediated injury. While all major histocompatibility complex (MHC) haplotypes (H-2a, k, s, b, and d) immunized with alpha3 NC1 domains of type IV collagen produce anti-alpha3(IV) NC1 antibodies that cross-react with human Goodpasture [anti-GBM/anti-alpha3(IV) NC1] autoantibodies, only a few strains developed nephritis and lung hemorrhage associated with Goodpasture syndrome. Crescentic glomerulonephritis and lung hemorrhage were MHC-restricted in haplotypes H-2s, b, and d (A beta/A alpha region in H-2s) and associated with the emergence of an IL-12/Th1-like T cell phenotype. Lymphocytes or anti-alpha3(IV) NC1 antibodies from nephritogenic strains transfer disease to syngeneic recipients. However, passive transfer of isogenic alpha3(IV) NC1 antibodies into -/- T cell receptor-deficient mice failed to produce nephritis. Finally, nephritis and its associated IL-12/Th1-like T cell response attenuate in disease-susceptible mice tolerized orally to alpha3(IV) collagen before immunization. Our findings suggest collectively, as a hypothesis, that anti-GBM antibodies in mice only facilitate disease in MHC haplotypes capable of generating nephritogenic lymphocytes with special T cell repertoires.

Susceptibility to anti-glomerular basement membrane disease is strongly associated with HLA-DRB1 genes

Anti-glomerular basement membrane (anti-GBM) disease is caused by autoimmunity to a component of glomerular basement membrane. The major autoantigen has been identified as the NC1 domain of the alpha 3 chain of type IV collagen, and patients are characterized by the presence of specific autoantibodies to this molecule. In common with other autoimmune disorders, there is a strong association with HLA genes, with up to 80% of patients inheriting an HLA-DR2 haplotype. To examine the genetic basis of susceptibility to anti-GBM disease in more detail, the HLA-DRB and DQB alleles inherited by 82 patients were analyzed using sequence specific oligonucleotides. This identified a hierachy of association of DRB1 genes with anti-GBM disease, including susceptibility (DRB1*15, DRB1*04), neutral (DRB1*03) and protective (DRB1*07) alleles. Analysis of inherited haplotypes, particularly DRB1*04 and DRB1*07 carrying haplotypes, provided further evidence that the primary association was with genes at the DRB1 locus. Comparison of the sequences of the positively and negatively associated alleles showed that polymorphic residues in the second peptide binding region of the HLA Class II antigen binding groove segregated with disease. This work supports the hypothesis that the HLA associations in anti-GBM disease reflect the ability of certain Class II molecules to bind and present peptides derived from the autoantigen to T helper cells.