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Objective: The International Society of Nephrology/Renal Pathology Society classification is the gold standard for the characterisation of lupus nephritis (LN) on renal biopsy, with therapeutic repercussions. Its recent revision simplified the current class subdivisions, eliminating the S/G forms of class IV, although data on a possible pathogenetic/clinical value of this subdivision are still contradictory., Methods: 353 renal biopsies from Belimumab International Study in LN were assessed through central pathology review. Univariate logistic models and a decision tree were performed on 314 adequate biopsies to evaluate the impact of histological features on focal/diffuse classes. Removing class I/II (n=6) and 'pure' class V (n=34), principal component analysis (PCA) and heatmap were used to explore similarities among III, IVS and IVG biopsies either incorporating or not the mixed classes (+V, n=274). Finally, a method aimed at partitioning the cases into k clusters based on their similarity (KMeans), was used to study features from the cohort of 'pure' class III/IVS/IVG cases (n=214) to determine alternative subdivisions based on phenotypic data., Results: Segmental endocapillary hypercellularity (EH) was prevalent in class III, global EH, wire loops, hyaline thrombi and double contours were hallmarks of class IVG, with IVS cases showing intermediate characteristics. Heatmap and PCA confirmed the segregation of these features among classes, showing better segregation for focal/diffuse LN as compared with the mixed classes (+V). KMeans revealed the presence of two main clusters, membranoproliferative-like (n=83) or vasculitis-like (n=131)., Conclusions: This study reveals new phenotypic forms of LN surpassing the traditional classes as determined by the current classification. Future validation and confirmation are required to confirm these findings., Competing Interests: Competing interests: IB, JAB, HTC, FF, L-HN received honoraria from GlaxoSmithKline (London, Great Britain) for their participation in the BLISS-LN trial as central review board., (© Author(s) (or their employer(s)) 2022. No commercial re-use. See rights and permissions. Published by BMJ.)

We present a consensus report pertaining to the improved clarity of definitions and classification of glomerular lesions in lupus nephritis that derived from a meeting of 18 members of an international nephropathology working group in Leiden, Netherlands, in 2016. Here we report detailed recommendations on issues for which we can propose adjustments based on existing evidence and current consensus opinion (phase 1). New definitions are provided for mesangial hypercellularity and for cellular, fibrocellular, and fibrous crescents. The term "endocapillary proliferation" is eliminated and the definition of endocapillary hypercellularity considered in some detail. We also eliminate the class IV-S and IV-G subdivisions of class IV lupus nephritis. The active and chronic designations for class III/IV lesions are replaced by a proposal for activity and chronicity indices that should be applied to all classes. In the activity index, we include fibrinoid necrosis as a specific descriptor. We also make recommendations on issues for which there are limited data at present and that can best be addressed in future studies (phase 2). We propose to proceed to these investigations, with clinicopathologic studies and tests of interobserver reproducibility to evaluate the applications of the proposed definitions and to classify lupus nephritis lesions., (Copyright © 2018 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

In 2012, the Systemic Lupus International Collaborating Clinics (SLICC) presented a new classification for systemic lupus erythematosus (SLE). In this classification, biopsy-confirmed lupus nephritis with positive antinuclear or anti-double-stranded DNA antibodies became a stand-alone criterion. Because of the unknown diagnostic performance among patients from nephrology clinics, we aimed to test the validity of the SLICC classification, compared with the American College of Rheumatology classification, in a cohort of patients whose renal biopsies would raise the clinicopathologic suspicion of lupus nephritis. All patients with a renal biopsy showing full house glomerular deposits and clinical follow-up in our center were included and reevaluated, after which clinicians and a pathologist reached a consensus on the reference-standard clinical diagnosis of SLE. The diagnostic performance and net reclassification improvement were assessed in 149 patients, 117 of whom had clinical SLE. Compared with the American College of Rheumatology classification, the SLICC classification had better sensitivity (100 vs. 94%); although, this was at the expense of specificity (91 vs. 100%; net reclassification improvement -0.03). Excluding the stand-alone renal criterion, the specificity of the SLICC classification reached 100%, with a significant net reclassification improvement of 0.06 compared with the American College of Rheumatology classification. The SLICC classification performed well in terms of diagnostic sensitivity among patients with full house glomerular deposits; whereas, the stand-alone renal criterion had no additional value and compromised the specificity. Thus, presumed patients with lupus nephritis in nephrology clinics reflect a distinct SLE disease spectrum warranting caution when applying SLE classification criteria., (Copyright © 2017 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Background and Objectives: The prognostic significance of histopathologic (sub)classes in the current classification of lupus nephritis (LN) is controversial. We analyzed clinical and histopathologic predictors of renal outcome in LN outside the framework of the classification., Design, Setting, Participants, & Measurements: Variables (50 histopathologic and ten clinical) were tested in mixed, linear, and Cox regression models for their association with renal flare, ESRD, and eGFR during follow-up (1, 5, and 10 years) in 105 patients with LN who underwent biopsy from 1987 to 2011. The Cockcroft-Gault (normalized to a body surface area of 1.73 m 2 ) and Schwartz formulas were used to calculate eGFR for adults and children, respectively., Results: During median follow-up of 9.9 years (25th-75th percentile, 5.9-13.8), 47 patients experienced a renal flare and 21 progressed to ESRD. Renal flare was predicted by fibrinoid necrosis (hazard ratio [HR], 1.04 per %; 95% confidence interval [95% CI], 1.00 to 1.07) and nonwhite race (HR, 2.23; 95% CI, 1.23 to 4.04). ESRD was predicted by fibrinoid necrosis (HR, 1.08 per %; 95% CI, 1.02 to 1.13), fibrous crescents (HR, 1.09 per %; 95% CI, 1.02 to 1.17), interstitial fibrosis/tubular atrophy (IF/TA) ≥25% (HR, 3.89; 95% CI, 1.25 to 12.14), eGFR at baseline (HR, 0.98 per ml/min per 1.73 m 2 ; 95% CI, 0.97 to 1.00), and nonwhite race (HR, 7.16; 95% CI, 2.34 to 21.91). A higher mean eGFR during follow-up was associated with normal glomeruli (+0.2 ml/min per 1.73 m 2 per %; 95% CI, 0.1 to 0.4). Like ESRD, a lower eGFR during follow-up was associated with fibrous crescents, IF/TA≥25%, and nonwhite race, as well as with cellular/fibrocellular crescents (-0.4 ml/min per 1.73 m 2 per %; 95% CI, -0.6 to -0.2) and age (-0.8 ml/min per 1.73 m 2 per year; 95% CI, -1.2 to -0.4)., Conclusion: The LN classification should include an index of evidence-based prognosticators. Awaiting validation of a formal index, we suggest that at least fibrinoid necrosis, fibrous crescents, and IF/TA warrant explicit independent scoring to assess the risk of progressive renal dysfunction in conjunction with clinical findings., (Copyright © 2017 by the American Society of Nephrology.)

Background: Full-house immunofluorescence in combination with various histopathologic lesions in the renal biopsies of patients without overt systemic lupus erythematosus (SLE) poses a diagnostic challenge. In this setting, the biopsy findings are sometimes termed non-lupus 'full-house nephropathy' (FHN). It is presently unknown whether idiopathic non-lupus FHN is clinicopathologically and prognostically distinct from lupus FHN., Methods: We included non-lupus FHN patients and lupus FHN controls (four or more American College of Rheumatology or Systemic Lupus International Collaborating Clinics criteria) who were biopsied between 1968 and 2014 at the Leiden University Medical Centre. Non-lupus FHN patients were studied for progression to SLE and/or the presence of other conditions with FHN. The clinicopathologic characteristics and prognosis of idiopathic non-lupus FHN patients were compared with those of lupus FHN patients., Results: Of 149 included patients, 32 had non-lupus FHN. During the median follow-up of 20 years, no non-lupus FHN patients developed SLE. In all, 20 non-lupus FHN patients had idiopathic non-lupus FHN, and in 12 patients, secondary non-lupus FHN was considered due to membranous nephropathy (anti-PLA2R-positive, n  = 1; cancer-associated, n  = 3), IgA nephropathy ( n  = 4), infection-related glomerulonephritis ( n  = 2) or anti-neutrophil cytoplasmic antibody-associated glomerulonephritis ( n  = 2). Idiopathic non-lupus FHN patients were more often male (P   <   0.001) than lupus FHN patients and their renal biopsies more often showed a mesangial (P   =   0.04) or membranous pattern of injury (P   =   0.02) and less intense C1q staining (P   =   0.002). Clinically, they presented with lower-range erythrocyturia (P   =   0.04), more proteinuria (P   <   0.01) and less complement consumption in the classical pathway (P   <   0.001) than lupus FHN patients. By multivariable Cox regression analysis of patients with a lupus nephritis class III/IV pattern of injury, idiopathic non-lupus FHN compared with lupus FHN was an independent risk factor for end-stage renal disease [hazard ratio 5.31 (95% confidence interval 1.47-19.24)]., Conclusions: Our results show that the clinical recognition of idiopathic non-lupus FHN as a diagnostic category is critical., (© The Author 2017. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved.)

Vascular endothelial growth factor A (VEGF-A) is essential for maintaining the glomerular filtration barrier. Absolute renal levels of VEGF-A change in patients with diabetic nephropathy and inflammatory kidney diseases, but whether changes in the renal splicing patterns of VEGF-A play a role remains unclear. In this study, we investigated mRNA splicing patterns of pro-angiogenic isoforms of VEGF-A in glomeruli and whole kidney samples from human patients with kidney disease and from mouse models of kidney disease. Kidney biopsies were obtained from patients with acute rejection following kidney transplantation, patients with diabetic nephropathy, and control subjects. In addition, kidney samples were obtained from mice with lupus nephritis, mice with diabetes mellitus, and control mice. The relative expression of each VEGF-A splice variant was measured using RT-PCR followed by quantitative fragment analysis. The pattern of renal VEGF-A splice variants was unchanged in diabetic nephropathy and lupus nephritis and was stable throughout disease progression in acute transplant rejection and diabetic nephropathy; these results suggest renal VEGF-A splicing stability during kidney disease. The splicing patterns were species-specific; in the control human kidney samples, VEGF-A 121 was the dominant isoform, whereas VEGF-A 164 was the dominant isoform measured in the mouse kidney samples., Competing Interests: The authors have declared that no competing interests exist.

Over 10 years have passed since the latest revision of the histopathologic classification of lupus nephritis. This revision was a significant improvement compared with the previous version, mainly because of clearer and more concise definitions and the elimination of mixed subclasses. Despite these improvements, there are still some difficulties in the classification for lupus nephritis, many of which are in the definitions provided. In this review, we focus on the difficulties surrounding the evaluation of classes III and IV lesions, particularly the definitions of endocapillary and extracapillary proliferation, the use of the terms endocapillary proliferation and hypercellularity, the clinical relevance of segmental and global subdivision in class IV, and the value of distinguishing lesions that indicate activity and chronicity. Vascular and tubulointerstitial lesions are also discussed. Furthermore, we give an overview of the history of the classification to provide background on the origin and development of the definitions in lupus nephritis. The issues raised in this review as well as the suggestions for improvements may assist with a revision of the lupus nephritis classification in the near future., (Copyright © 2015 by the American Society of Nephrology.)

Background and Objectives: To treat lupus nephritis effectively, proper identification of the histologic class is essential. Although the classification system for lupus nephritis is nearly 40 years old, remarkably few studies have investigated interobserver agreement. Interobserver agreement among nephropathologists was studied, particularly with respect to the recognition of class III/IV lupus nephritis lesions, and possible causes of disagreement were determined., Design, Setting, Participants, & Measurements: A link to a survey containing pictures of 30 glomeruli was provided to all 360 members of the Renal Pathology Society; 34 responses were received from 12 countries (a response rate of 9.4%). The nephropathologist was asked whether glomerular lesions were present that would categorize the biopsy as class III/IV. If so, additional parameters were scored. To determine the interobserver agreement among the participants, κ or intraclass correlation values were calculated. The intraclass correlation or κ-value was also calculated for two separate levels of experience (specifically, nephropathologists who were new to the field or moderately experienced [less experienced] and nephropathologists who were highly experienced)., Results: Intraclass correlation for the presence of a class III/IV lesion was 0.39 (poor). The κ/intraclass correlation values for the additional parameters were as follows: active, chronic, or both: 0.36; segmental versus global: 0.39; endocapillary proliferation: 0.46; influx of inflammatory cells: 0.32; swelling of endothelial cells: 0.46; extracapillary proliferation: 0.57; type of crescent: 0.46; and wire loops: 0.35. The highly experienced nephropathologists had significantly less interobserver variability compared with the less experienced nephropathologists (P=0.004)., Conclusions: There is generally poor agreement in terms of recognizing class III/IV lesions. Because experience clearly increases interobserver agreement, this agreement may be improved by training nephropathologists. These results also underscore the importance of a central review by experienced nephropathologists in clinical trials., (Copyright © 2015 by the American Society of Nephrology.)

Background: The clinical utility of performing repeat biopsies during lupus nephritis flares is questionable and data pointing towards frequent class switches are based on the old WHO classification. This retrospective study investigates the hypothesis that clinically relevant switches from proliferative to non-proliferative lesions and vice versa as determined by the new ISN/RPS classification are a rare event and that repeat biopsies are unnecessary in many cases., Methods: Thirty-five patients with lupus nephritis and one or more repeat renal biopsies were included. Eighty-four biopsies were blindly reassessed according to the ISN/RPS classification., Results: Twenty-five patients had one repeat biopsy, 6 patients had two and 4 patients had three repeat biopsies. Forty-nine comparisons between reference and repeat biopsies could be made. In 25 cases (54.3%), there was no shift in ISN/RPS class on repeat biopsies. In 41 instances, paired biopsies showed proliferative lesions both on reference and repeat biopsies, whereas five of six cases with non-proliferative lesions on a reference biopsy switched to proliferative lesions on a repeat biopsy. Clinically significant class switches during lupus nephritis flares were more frequent in patients with non-proliferative lesions in their reference biopsy (P < 0.001)., Conclusion: The results show that patients with proliferative lesions in the original biopsy rarely switch to a pure non-proliferative nephritis during a flare. Therefore, a repeat biopsy during a lupus nephritis flare is frequently not necessary if proliferative lesions were found in the reference biopsy. However, in the case of a non-proliferative lesion in the reference biopsy, class switches are frequently found and repeat biopsies are advisable.

Objective: In patients with systemic lupus erythematosus (SLE) and lupus nephritis, the presence of antiphospholipid antibodies (aPL) is considered to be an indication of increased risk of thrombotic microangiopathy, a serious complication of SLE. Previous studies have demonstrated a critical role for activation of the classical pathway of complement that leads to thrombotic injury in the presence of aPL. This study was undertaken to investigate whether C4d deposition in lupus nephritis is related to circulating aPL and the presence of renal microthrombi., Methods: Deposition patterns of C4d in 44 renal biopsy samples obtained from 38 patients with biopsy-proven lupus nephritis were determined by staining with a polyclonal anti-C4d antibody. A phosphotungstic acid-hematoxylin stain was used to identify fibrin microthrombi. Clinical data (serum creatinine levels and presence or absence of aPL) were obtained and correlated with findings in the renal biopsy specimens. Patients were categorized as having aPL (n = 20) or not having aPL (n = 18)., Results: A strong relationship between the intensity of glomerular C4d staining and the presence of microthrombi was found (P < 0.002). Intense glomerular C4d deposition was present in 7 of 8 biopsy samples showing renal microthrombi. Neither C4d deposition nor the presence of microthrombi was correlated with aPL status., Conclusion: Our findings suggest that activation of the classical pathway of complement plays a pathogenic role in the development of renal tissue injury leading to thrombosis, irrespective of the type of circulating antibodies present. Immunodetection of glomerular C4d deposition in renal biopsy samples could be a convenient method of identifying patients at risk of thrombotic microangiopathy.

Chimerism occurs twice as often in the kidneys of women with lupus nephritis as in normal kidneys and may be involved in the pathogenesis of systemic lupus erythematosus. Pregnancy is considered the most important source of chimerism, but the exact relationship between pregnancy, the persistence of chimeric cells and the development of systemic lupus erythematosus has not been investigated. Renal biopsies and clinical data from patients in the First Dutch Lupus Nephritis Study were used. Chimeric cells were identified by in-situ hybridization of the Y chromosome. A questionnaire was used to obtain detailed reproductive data including pregnancy history and miscarriages. Chimerism was found in 12 of 26 (46%) renal biopsies. Of the 12 chimeric women, 5 reported a pregnancy; of 14 women who were not chimeric, 8 reported a pregnancy. Chimeric women who had been pregnant reported significantly more pregnancies than non-chimeric women who had been pregnant (P=0.04). The median age of the youngest child was higher in chimeric women (19 years) than in non-chimeric women (6 years). Despite the attention given to pregnancy histories with respect to chimerism, this study shows that in patients with systemic lupus erythematosus, a clear-cut relationship is not apparent. A considerable number of chimeric women did not report a pregnancy: in these women, other sources of chimerism must be considered. Our data support the theory that only certain subsets of chimeric cells persist into the maternal circulation after pregnancy.

Until recently, intravenous cyclophosphamide pulses with oral corticosteroids were regarded standard therapy for proliferative lupus nephritis (LN). Azathioprine, a less toxic alternative, was never proven to be inferior. In the first Dutch lupus nephritis study (enrollment between 1995 and 2001), we randomized 87 proliferative LN patients to either cyclophosphamide pulses (750 mg/m(2), 13 pulses in 2 years) combined with oral prednisone (CY) or to azathioprine (2 mg/kg/day in 2 years) combined with intravenous pulses of methylprednisolone (3 x 3 pulses of 1000 mg) and oral prednisone (AZA). After a median follow-up of 5.7 years (interquartile range 4.1-7.2 years), doubling of serum creatinine was more frequent in the AZA group, although not statistically significant (relative risk (RR): 4.1, with 95% confidence interval (95% CI): 0.8-20.4). Relapses occurred more often in the AZA group (RR: 8.8, 95% CI: 1.5-31.8). Creatinine and proteinuria at last visit did not differ between the two treatment arms. Moreover, 88.4% of the patients in the AZA arm were still free of cyclophosphamide treatment. During the first 2 years, the frequency of remission was not different, but infections, especially herpes zoster virus infections (HZV) were more frequent in the AZA group. Parameters for ovarian function did not differ between the two groups. In conclusion, in this open-label randomized controlled trial, cyclophosphamide was superior to azathioprine with regard to renal relapses and HZV. At last follow-up, there were no differences in serum creatinine or proteinuria between the two groups. However, since our study lacked sufficient power, longer follow-up is needed to reveal putative differences.

The currently used classification reflects our understanding of the pathogenesis of the various forms of lupus nephritis, but clinicopathologic studies have revealed the need for improved categorization and terminology. Based on the 1982 classification published under the auspices of the World Health Organization (WHO) and subsequent clinicopathologic data, we propose that class I and II be used for purely mesangial involvement (I, mesangial immune deposits without mesangial hypercellularity; II, mesangial immune deposits with mesangial hypercellularity); class III for focal glomerulonephritis (involving <50% of total number of glomeruli) with subdivisions for active and sclerotic lesions; class IV for diffuse glomerulonephritis (involving > or =50% of total number of glomeruli) either with segmental (class IV-S) or global (class IV-G) involvement, and also with subdivisions for active and sclerotic lesions; class V for membranous lupus nephritis; and class VI for advanced sclerosing lesions. Combinations of membranous and proliferative glomerulonephritis (i.e., class III and V or class IV and V) should be reported individually in the diagnostic line. The diagnosis should also include entries for any concomitant vascular or tubulointerstitial lesions. One of the main advantages of the current revised classification is that it provides a clear and unequivocal description of the various lesions and classes of lupus nephritis, allowing a better standardization and lending a basis for further clinicopathologic studies. We hope that this revision, which evolved under the auspices of the International Society of Nephrology and the Renal Pathology Society, will contribute to further advancement of the WHO classification.

Lupus nephritis is a frequent and severe complication of SLE. In the last decades, animal models for SLE have been studied widely to investigate the immunopathology of this autoimmune disease because abnormalities can be studied and manipulated before clinical signs of the disease become apparent. In this review an overview is given of our current knowledge on the development of lupus nephritis, as derived from animal models, and a hypothetical pathway for the development of lupus nephritis is postulated. The relevance of the studies in experimental models in relationship with our knowledge of human SLE is discussed.

Mice with chronic graft-versus-host disease (GvHD) develop a lupus-like disease with severe immune complex glomerulonephritis. Previous studies with this model have shown that anti-laminin autoantibodies are involved in immune complex formation and that glomerular laminin expression alters qualitatively. The present study investigated glomerular laminin chain expression and autoantibody reactivity with matrix antigens during disease development in mice with chronic GvHD, killed before and 6, 8, 10, and 11 weeks after disease induction, using antibodies raised against laminin chain peptides, in immunofluorescence and western blotting studies. Decreased glomerular expression of the laminin beta1 chain, unaltered expression of the laminin beta2 and gamma1 chains, and increased expression of the laminin alpha1 chain and filamin/actin-binding protein 280 (ABP 280) were found during disease progression. Furthermore, 4 weeks after disease induction, autoantibodies appeared which were reactive with laminin alpha1, beta1, beta2, and gamma1 chains, and filamin in rat mesangial cell matrix. Ten weeks after disease induction, autoantibodies reacted with filamin, and beta2 and gamma1 laminin chains. Autoantibodies reacted with laminin chains only and not with other proteins in matrices extracted from glomeruli of normal and diseased mice. Staining with H50, an anti-laminin alpha1 chain/anti-filamin monoclonal autoantibody derived from an MRL/lpr mouse with spontaneous lupus nephritis, confirmed these observations and showed identical anti-laminin/anti-filamin autoantibody reactivity in two different models for lupus nephritis. In summary, differential glomerular expression of laminin chains was found during the development of chronic GvHD. Concomitantly with expression of the laminin alpha1 chain and/or filamin in the glomerulus, anti-laminin alpha1 and/or anti-filamin reactivity was present, pointing towards a role for (neo) antigen expression in the epitope spreading of the immune response. Furthermore, glomerular expression of laminin beta1 decreased in conjunction with decreased presence of anti-laminin beta1 reactivity, presumably due to antigen masking or shedding of immune complexes into the urine. These changes in anti-laminin chain autoantibodies, with concomitant alterations in the glomerular expression of laminin chains, may aggravate progressive immune injury in this model for lupus nephritis., (Copyright 2000 John Wiley & Sons, Ltd.)

Both in animal models and in human systemic lupus erythematosus (SLE) the occurrence of nephritogenic autoantibodies bearing dominant idiotypes has been described. In this study we investigate the relation between the induction pathway of polyclonal B cell activation and the production and glomerular deposition of nephritogenic antibodies with shared dominant idiotype(s). Polyclonal B cell activation was induced in several experimental models characterized by glomerular immune deposit formation. We monitored the occurrence of dominant idiotypes among immunoglobulins deposited in the glomeruli. In addition, we studied the species specificity of the dominant idiotypes, by monitoring their presence in kidney sections of patients with an immunologically mediated kidney disease. Anti-idiotype antisera against two monoclonal anti-DNA autoantibodies were used, derived from MRL-lpr/lpr mice, i. e. clone H241 and clone H130. Autoantibodies with the H241 idiotype were present in immune complex depositions in all experimental models but not in humans. We therefore conclude that the presence of this dominant idiotype is independent of the induction pathway of polyclonal B cell activation. However, autoantibodies bearing the H130 idiotype were only detected in kidney sections of mice with spontaneous lupus.

A limited T-cell receptor (TCR) Vbeta repertoire employed by autoreactive T cells may be related to the development and course of autoimmune diseases. Vbeta repertoire skewing has been observed not only in man, but also in animal models of several human autoimmune diseases, such as MRL-lpr mice, which spontaneously develop a systemic lupus erythematosus (SLE)-like disease. Murine chronic graft-versus-host disease (GVHD) is an inducible model for SLE, involving direct interaction between donor T cells and recipient B cells. It is not known whether Vbeta-specific T-cell subsets are pathogenically involved in this model. Retroviral superantigens such as Mls-1 are known to have a profound impact on the TCR Vbeta repertoire in mice. Restriction of the peripheral TCR repertoire may result from intrathymic expression of Mls-1, which causes deletion of T cells expressing Vbeta6, -7, -8.1, or -9. Mls-1 incompatibility between donor and recipient can be used to determine the involvement of these TCR Vbeta families in GVHD. In the present study we induced GVHD in several strain combinations to investigate TCR Vbeta gene expression during GVHD, and the effect of Mls-1 incompatibility on the TCR Vbeta repertoire. TCR Vbeta gene expression was determined using an RNase protection assay. Our results indicate that T cells expressing the Vbeta2 or Vbeta16 chain play an important pathogenetic role, while T cells bearing the Vbeta1 or Vbeta6 chain may be related to self-limitation of the lupus-like disease in this model.

Mice with chronic graft-versus-host disease (GvHD) induced by injection of DBA/2 lymphocytes into (DBA/2 x C57BL/10) F1 hybrids (DBA/2 GvHD) develop a lupus-like glomerulonephritis with global glomerulosclerosis 12 weeks after induction of the disease. In two other strain combinations with similar H-2 incompatibilities [BALB/c into BALB/c x BL10 (BALB/c GvHD) and BALB.D2 into BALB.D2 x BL10 (BALB.D2 GvHD)], GvHD induction leads to lupus nephritis without global glomerulosclerosis. This study investigated the identity of kidney-infiltrating leukocytes and their involvement in the development of glomerulosclerosis in these three strain combinations. In mice with DBA/2 GvHD, a significant increase in glomerular CD11a-positive cells was found 4 weeks after disease induction. Mice with BALB/c or BALB.D2 GvHD did not show an increase in glomerular CD11a-positive cells at any time point. In the interstitium, CD11a-positive cells were observed 4 weeks after disease induction only in mice with DBA/2 GvHD. In mice with BALB.D2 GvHD, no increase was found in interstitial CD11a-positive cells. In mice with BALB/c GvHD, interstitial CD11a-positive cells were found from week 4 onward. Further immunohistochemical analysis of the glomerular CD11a-positive cells in mice with DBA/2 GvHD showed that these cells were neither polymorphonuclear leukocytes (PMN), nor CD3-positive (T cells), B220-positive (B cells), or F4/80-positive (macrophages). They were all CD45-positive (leukocytes) and MHC class II-positive. In conclusion, we have shown in this model of chronic lupus nephritis that glomerular influx of as yet unidentified CD11a-positive leukocytes is associated with the development of glomerulosclerosis.

The purpose of this article is to review a set of recently obtained data concerning matrix and matrix adhesion molecules in renal disease. Our goal is not to cover the entire topic, but rather to focus on findings obtained with an experimental model for chronic lupus nephritis, evoked in mice by inducing graft-versus-host disease (GVHD). The overall aim of these studies was to investigate the role of adhesion molecules as targets for autoantibodies, in the recruitment of inflammatory cells, and in the accumulation of matrix in kidney disorders. In addition, we set out to discover how matrix proteins in renal diseases differ from normal matrix molecules both quantitatively, in their increased frequency, and qualitatively, in their intramolecular structure. The advances in understanding and methodology described in this review imply a substantial capability for greater insight into the pathogenesis of kidney disease; for making better use of renal biopsies, such as in applying competitive reverse-transcriptase-polymerase chain reaction (RT-PCR) in RNA analysis for matrix; and in developing more effective treatment strategies for patients with kidney disease.

Mice with chronic graft-versus-host disease (GVHD), induced by injection of DBA/2 lymphocytes in (C57BL10*DBA/2) F1 hybrids, develop a syndrome resembling systemic lupus erythematosus (SLE) with immune complex glomerulonephritis. In this model we evaluated the role of interactions between CD11a (LFA-1alpha) and CD54 (intercellular adhesion molecule-1 (ICAM-1)) molecules on leucocytes in the development of renal disease in systemic autoimmunity. Two weeks after induction of GVHD, when anti-nuclear autoantibodies were detected in the circulation and immune complexes had formed in the glomeruli, mice were injected twice per week with rat anti-CD11a and anti-CD54 MoAbs, or with their vehicle PBS, or with control rat IgG. MoAb treatment significantly lowered albuminuria and increased survival compared with control mice with GVHD. In the glomeruli of MoAb-treated mice there was markedly less binding of immunoglobulin and C3, while anti-renal tubular epithelium autoantibodies, but not anti-glomerular basement membrane autoantibodies, were significantly lowered in the circulation 4 weeks after disease induction. In addition, MoAb treatment inhibited the glomerular influx of CD11a+ cells and decreased development of histological abnormalities in the kidneys. Both rat IgG- and MoAb-treated mice developed anti-rat immunoglobulin antibodies. Furthermore, a marked splenomegaly with an increase of the T cell compartment was observed in MoAb-treated mice with GVHD. These results show that CD11a/CD54 interactions are crucial for the full-blown development of lupus nephritis in this model. Treatment aimed at blocking the activity of these molecules profoundly attenuated the development of renal disease in chronic GVHD even if started when first symptoms of SLE (i.e. anti-nuclear autoantibodies in sera and glomerular binding of immunoglobulins) were already detectable.

In patients with systemic lupus erythematosus, the female-to-male ratio is as high as 10:1. Sex hormones are thought to play a role in this difference in susceptibility. In a previous study, we demonstrated a high susceptibility of female mice to the development of glomerulonephritis after induction of chronic graft-versus-host disease (GVHD), compared with male mice. In order to unravel further this gender-related difference (C57B1/10*DBA/2)F1 hybrid mice were either castrated or ovariectomized and treated with 17beta-ethinyloestradiol or testosterone-decanoate preceding the induction of chronic GVHD. Testosterone-decanoate reduced significantly the development of albuminuria in females. In contrast, proteinuria of 17beta-ethinyloestradiol-treated female mice was in the same range as that of sham-operated mice. Autoantibody levels against glomerular basement membrane, renal tubular epithelium, dsDNA and ssDNA, as determined by ELISA, were higher in 17beta-ethinyloestradiol-treated female mice than in all other groups. Immunofluorescence studies showed the presence of immunoglobulin and complement deposits in glomeruli of all animals, without significant differences between the experimental groups. Our findings confirm earlier observations, in that testosterone-decanoate is shown to be an inhibitory compound, whereas 17beta-ethinyloestradiol has stimulating properties in autoimmunity. Moreover, our results show for the first time differential hormonal effects on autoantibody levels and proteinuria in experimental lupus nephritis.

Susceptibility to systemic lupus erythematosus (SLE) and, in particular, lupus nephritis is strongly influenced by genetic factors. Previous studies have shown that MHC-related antigens influence the development of SLE. In the current study, we set out to investigate how non-MHC genes influence the pathogenesis of glomerulonephritis in chronic graft-versus-host disease (GVHD) in mice, a model for lupus nephritis. For the induction of GVHD we used parent-to-F1 hybrid mouse strain combinations. DBA/2, BALB/c, BALB.D2 and C57B1/10.D2 (BL10.D2) donor lymphocytes carrying an H-2d haplotype were injected into H-2b/d F1 hybrids of BL10 mice, which differed only at non-MHC loci. Within these hybrid strains the development of immune complex glomerulonephritis was investigated by monitoring the occurrence of autoantibodies in the circulation, deposition of immunoglobulins in the glomeruli, development of albuminuria, and glomerulosclerosis. In diseased DBA/2 mice albuminuria developed 6 weeks after induction of the disease. Mice with a BALB background developed a lupus-like syndrome characterized by albuminuria starting 8 weeks after induction of the GVHD. During the development of the GVHD, polyclonal B cell activation occurred in both the DBA/2 and BALB/c strains, resulting in the formation of autoantibodies. Only the strain combination using DBA/2 mice developed anti-GBM antibodies. In DBA/2 and BALB strain combinations immune complexes were detected in a granular pattern along the glomerular capillary walls. In the DBA/2 recipients a linear pattern of immunoglobulin depositions preceded the granular phase. This study demonstrates that: (i) non-MHC genes govern the pathogenesis of immune complex nephritis in this model by influencing the autoantibody profile; and (ii) the presence of anti-GBM antibodies in the early stages of the disease is a conditio sine qua non for the development of full-blown glomerulonephritis and glomerulosclerosis in this model.

Mice with chronic graft-versus-host disease (GvHD), induced by injection of DBA/2 lymphocytes into (C57BL10*DBA/2)F1 hybrids, develop a lupus-like syndrome with immune complex glomerulonephritis. Circulating autoantibodies are reactive with various self-antigens, including DNA, renal tubular epithelium (RTE), and laminin-1. To elucidate the reactivity of autoantibodies with renal antigens in experimental lupus nephritis further, the reactivity of the autoantibodies was studied in more detail by generating hybridomas from GvHD spleen cells. Hybridomas were selected for reactivity with RTE and laminin-1 coated on nitrocellulose sheets. Four stable clones were obtained (GV1-GV4). Monoclonal antibody (mAb) GV1 showed no reactivity on kidney sections, while GV2 stained the brush border of proximal tubular epithelial cells. Both GV1 and GV2 reacted only with RTE in ELISA. GV3 showed a nuclear staining pattern, while GV4 stained matrix structures on F1 kidney sections. GV3 and GV4 both reacted with RTE, laminin-1, ssDNA, and dsDNA in ELISA. Growth of hybridomas in mice, but not passive transfer of the mAbs, led to glomerular Ig binding for mAbs GV3 and GV4 without development of proteinuria. Our results show that in addition to anti-nuclear autoantibodies cross-reactive with renal antigens, autoantibodies reactive with renal antigens and not with DNA are generated during chronic GvHD. Based on these results, combined with those of earlier experiments, we conclude that a combination of autoantibodies against multiple epitopes is necessary for the induction of glomerular damage in this model for lupus nephritis.

Previous studies have revealed quantitative alterations in laminin-1 expression at the mRNA and protein levels during the development of glomerulonephritis and glomerulosclerosis in chronic graft-versus-host disease in mice, a model for lupus nephritis. We have now studied the qualitative alterations in laminin expression with two monoclonal antibodies that recognize epitopes on either the E8 or the P1 fragment of laminin-1. Both of these fragments are involved in cell-matrix and matrix-matrix interactions. In normal glomeruli these laminin epitopes are present only in the mesangial matrix; during embryogenesis, however, they are also present in the glomerular basement membrane. The distribution of laminin epitopes was first studied by using immunofluorescence in kidneys of mice with graft-versus-host disease at different points in time after disease induction. Reflection contrast and immunoelectron microscopy were performed after in vivo injection of the horseradish peroxidase-coupled monoclonal antibodies. In glomeruli of mice 8 weeks after disease induction, both injected antibodies bound specifically in electron-dense immune deposits in the mesangium and subepithelially along the glomerular basement membrane as well as in the expanded mesangial matrix. At 11 and 12 weeks after disease induction, when focal and segmental glomerulosclerosis had developed, the antibodies additionally bound in the matrix subendothelially along the glomerular basement membrane and at the periphery of end-stage sclerotic lesions. To study changes in the distribution of laminin epitopes over time, mice were injected with either monoclonal antibody before induction of graft-versus-host disease. The antibodies were detected 8 and 12 weeks later in the mesangial matrix of mice with lupus nephritis. Once segmental glomerulosclerosis had developed, the antibodies were additionally detected within the thickened glomerular capillary wall. The specific binding of anti-laminin monoclonal antibodies in electron-dense immune deposits further substantiates the hypothesis that anti-laminin autoantibodies participate in glomerular immune complex formation in this model, as suggested by earlier studies. Furthermore, our results show that the distribution of glomerular laminin epitopes in the matrix is altered during the development of glomerular disease. These changes in the structure of the glomerular basement membrane may contribute to the abnormal cell-matrix and matrix-matrix interactions during the development of glomerular disease in this model for lupus nephritis.

The influence of cyclosporine A (CsA) treatment on the development of glomerulonephritis and glomerulosclerosis was investigated in chronic graft-versus-host disease (GvHD), a murine model for lupus nephritis. The renal disease is characterized by the formation of IgG-containing electron-dense deposits along the glomerular basement membrane (GBM) and in the mesangium, followed by the onset of proteinuria which starts, varying per individual mouse, about six weeks after the induction of the disease. Glomerular mRNA levels for matrix molecules were increased from week 4, preceding mesangial matrix expansion and GBM thickening which occurred from week 6. These initial events finally led to development of glomerulosclerosis, and end-stage renal failure. Groups of mice received three intraperitoneal (i.p.) injections per week with different doses of CsA, and treatment was started 2, 4, or 6 weeks after induction of the disease. Treatment with 10 or 50 mg CsA/kg/week did not influence the development of glomerulonephritis or glomerulosclerosis. Injection of 100 mg CsA/kg/week delayed the onset of proteinuria only when treatment was started in week 2. In week 6 some mice had already developed proteinuria whereas others had not. Treatment with 250 mg CsA/kg/week starting in week 6 abrogated glomerulonephritis and glomerulosclerosis only in those animals which were not yet proteinuric at that time. This, despite comparable increased autoantibody levels against DNA, GBM, and renal tubular epithelium (RTE) in both treated and untreated GvHD mice. Further increase in proteinuria and development of glomerulosclerosis could not be prevented if the mice already had developed proteinuria when CsA treatment was started. Dot blot analysis and in situ hybridization showed significantly decreased mRNA levels for alpha 1(I) and alpha 1(IV) collagen in kidneys of CsA-treated mice as compared to those of untreated mice 12 weeks after induction of the disease, if the highest dose of CsA was administered before the onset of proteinuria. No effect on these whole-kidney mRNA levels was observed in mice which had already developed proteinuria before CsA injections were started. Increased mRNA expression for matrix molecules in this group and in untreated GvHD mice was observed mainly in the interstitium. The kidneys of the treated GvHD mice and those of mice injected with 250 mg CsA/kg/week without induction of GvHD showed no morphological signs of CsA nephrotoxicity. We conclude that treatment with 250 mg CsA/kg/week prevents the development of glomerulonephritis and glomerulosclerosis in this model of lupus nephritis, if started before the onset of proteinuria.(ABSTRACT TRUNCATED AT 400 WORDS)

Systemic lupus erythematosus is a disease that is particularly suited for studies of glomerular basement membrane pathology. Classification of the renal pathology of lupus nephritis is usually based on light microscopic features, combined with immunofluorescence findings and electron microscopic alterations. Study of renal biopsy helps to distinguish potentially reversible and irreversible disease, and to estimate prognosis of patients with lupus nephritis. Moreover, studies of human disease, as well as the availability of animal models and in vitro cell culture systems employing biochemical and molecular biological studies of extracellular matrix, have led to a considerable increase in knowledge of the pathogenetic events underlying derangements of the glomerular basement membrane in lupus nephritis.

Background: In murine chronic graft-versus-host disease, an experimental model for lupus nephritis, autoantibodies against renal tubular epithelium can be found. Part of these antibodies are directed against a constituent of renal tubular epithelium, the enzyme Dipeptidyl peptidase IV (DPP IV). DPP IV is present on the cell membrane of glomerular epithelial and endothelial cells, and plays an important role in cell-extracellular matrix interactions. In mice and rats, administration of heterologous anti-DPP IV antibodies can induce proteinuria and podocyte effacement., Experimental Design: In this study, the glomerular DPP IV enzyme activity was investigated in the course of graft-versus-host disease in (C57BL/10 x DBA/2) F1 hybrids both by light- and electron microscopy using a DPP IV-specific substratum., Results: Light microscopical examination revealed an overall reduction of DPP IV activity and an altered distribution pattern in glomeruli as early as 4 weeks after induction of graft-versus-host disease. Immunofluorescence studies using anti-DPP IV antibodies showed actual redistribution, excluding antibody-mediated enzyme inactivation. Enzyme electron microscopy revealed an irregular deposition of reaction product characterized by a patchy, "moth eaten" appearance of the endothelial and epithelial membranes. This process occurred simultaneously with the development of albuminuria and preceded the effacement of epithelial foot processes. In control mice, DPP IV showed a continuous distribution along endothelial and podocyte membranes., Conclusions: In view of these findings we postulate that impairment of the function of DPP IV as a non integrin adhesion molecule may be one of the causative factors underlying the structural and functional lesions observed in this model for lupus nephritis.

Autoimmune diseases are far more common in women than in men. In the incidence of systemic lupus erythematosus (SLE), the female-to-male ratio is as high as 10:1. This suggests that sex hormones may play a fundamental role in determining the susceptibility to these diseases. In order to investigate the sex-related differences in the inducibility of chronic graft-versus-host disease-related experimental lupus nephritis, lymphocytes from female DBA/2 donor mice were administered to either male or female (C57BL10 x DBA/2)F1 recipients. An additional group of male recipients received lymphocytes from male DBA/2 donors. After four cell transfers, female recipients developed a significantly higher albuminuria than both male groups. Serum concentrations of autoantibodies against glomerular basement membrane (GBM), collagen IV, and laminin were significantly higher in females 2-4 weeks after induction. Levels of circulating autoantibodies against renal tubular epithelial antigens (RTE) and nuclear antigens were not different between the sexes. In transfer studies, the necessity of the presence of anti-GBM and anti-RTE autoantibodies for the development of glomerulonephritis was confirmed. These findings indicate that: (i) in this model of lupus nephritis, susceptibility to glomerulonephritis is strongly influenced by sex-related genes; and (ii) among the variety of autoantibodies occurring in this model of SLE, both anti-GBM and anti-RTE autoantibodies play a key role in the pathogenesis of glomerulonephritis.

The present studies dealt with the pathogenesis of renal involvement in murine chronic graft-versus-host disease, which is a model for human systemic lupus erythematosus. The disease was induced in (C57BL10xDBA/2)F1 hybrids by injection of DBA/2 lymphocytes. The animals developed systemic disease accompanied by deposition of autoantibodies in the glomeruli and a lupus type of nephritis. Antibodies were eluted from glomeruli isolated during various stages of the disease by magnetic extraction from iron-perfused kidneys. For assessment of the specificity of the antibodies, we used indirect immunofluorescence, an enzyme-linked immunosorbent assay, and immunoblotting. In glomeruli from week 4, autoantibodies were found to be directed against several antigens, among which were the glomerular basement membrane component laminin and the glomerular enzyme dipeptidyl peptidase IV, whereas week 8 glomeruli also showed antibodies directed against nuclear antigens. Both laminin and dipeptidyl peptidase IV are known nephritogenic antigens occurring in renal tubular epithelial brush border preparations. Antibodies eluted from isolated glomeruli of diseased animals bound in a granular pattern along the glomerular capillary wall after in vivo transfer. Anti-renal tubular epithelial antibodies in the sera of diseased animals were affinity purified and injected into naive mice, which induced immune complex glomerulonephritis and proteinuria, thus confirming the nephritogenic role of these autoantibodies in this model.

The pathogenesis of renal involvement was studied in murine chronic graft-versus-host disease (GVHD), which is a model for human systemic lupus erythematosus. GVHD was induced by four i.v. injections of lymphocytes from DBA/2 donor mice into (C57BL/10 x DBA/2)F1 hybrids at 3-4-day intervals. Two weeks after the first injection, antibodies were found to have been deposited in the mesangium and along the glomerular basement membrane (GBM) in a linear arrangement, which changed to a granular pattern after 6-8 weeks. In this stage, large electron-dense complexes were present both subepithelially and subendothelially along the GBM. Proteinuria increased up to 11,300 +/- 2140 micrograms/18 h. Indirect immunofluorescence studies and ELISA showed that sera and kidney eluates contained autoantibodies directed against nuclear antigens and GBM component laminin as well as against renal tubular epithelial antigens (RTE). The specificity of the anti-RTE antibodies was further characterized by the use of absorption techniques as well as immunoblotting. The early linear immunofluorescence pattern seems to be associated with glomerular binding of anti-GBM antibodies, while electron-dense complex formation in later stages may be induced by the superimposed deposition of anti-RTE antibodies. Similar phenomena were recently described in Heymann's nephritis in the rat, a model for human membranous nephropathy.

Chronic graft-versus-host disease (GvHD) was induced in (C57BL/10 x DBA/2)F1 and (B10.S x DBA/2)F1 hybrids by injection of DBA/2 lymphocytes. All of the animals developed GvHD. Renal disease and proteinuria occurred in all of the (C57BL/10 x DBA/2)F1 hybrids, but only in 54% of the (B10.S x DBA/2)F1. The type of renal lesion was similar in all diseased animals of both strains, i.e., immune complex glomerulonephritis (ICGN) with deposition of antibodies and complement in glomeruli. To find out whether H-2 haplotype or other factors, such as non-H-2 linked genes, determine the susceptibility for renal involvement in GvHD, we produced (B10 x B10.S)F1 x DBA/2 mice, determined their H-2 genotype serologically, and separated them into H-2b/d and H-2s/d groups. These two groups did not differ with respect to susceptibility to renal disease in the course of GvHD, which indicates that H-2 is not the decisive genetic factor. We conclude that factors not linked with H-2 exert a major influence on susceptibility to GvHD-related renal disease in these mice.