Glomerular Immune Complex Deposition Research Articles

OP0059 Importance of the protein tyrosine phosphatase SHP1 in dendritic cells for prevention of TH1 cell differentiation and autoimmunity: A potential target for the therapy

BackgroundDendritic cells (DCs) are professional antigen-presenting cells crucial for initiating immune response to pathogens as well as for maintaining immune tolerance to self-antigens. Dysregulation of the function of DCs is...

Analysis of a wild mouse promoter variant reveals a novel role for FcγRIIb in the control of the germinal center and autoimmunity

Genetic variants of the inhibitory Fc receptor FcγRIIb have been associated with systemic lupus erythematosus in humans and mice. The mechanism by which Fcgr2b variants contribute to the development of autoimmunity is unknown and was investigated by knocking in the most commonly conserved wild mouse Fcgr2b promoter haplotype, also associated with autoimmune-prone mouse strains, into the C57BL/6 background. We found that in the absence of an AP-1-binding site in its promoter, FcγRIIb failed to be up-regulated on activated and germinal center (GC) B cells. This resulted in enhanced GC responses, increased affinity maturation, and autoantibody production. Accordingly, in the absence of FcγRIIb activation-induced up-regulation, mice developed more severe collagen-induced arthritis and spontaneous glomerular immune complex deposition. Our data highlight how natural variation in Fcgr2b drives the development of autoimmune disease. They also show how the study of such variants using a knockin approach can provide insight into immune mechanisms not possible using conventional genetic manipulation, in this case demonstrating an unexpected critical role for the activation-induced up-regulation of FcγRIIb in controlling affinity maturation, autoantibody production, and autoimmunity.

Anti–tumor necrosis factor α treatment of interferon‐α–induced murine lupus nephritis reduces the renal macrophage response but does not alter glomerular immune complex formation

To analyze the mechanism for the therapeutic effects of tumor necrosis factor α (TNFα) inhibition in a murine model of systemic lupus erythematosus. We used the (NZB × NZW)F(1) (NZB/NZW) mouse model of interferon-α-induced lupus nephritis and treated mice with TNF receptor type II (TNFRII) Ig after TNFα expression was detected in the kidneys. Autoantibodies were measured by enzyme-linked immunosorbent assay (ELISA), and autoantibody- forming cells were determined using an enzyme-linked immunospot assay. Activation of splenocytes was analyzed by flow cytometry. Kidneys were harvested and analyzed using flow cytometry, immunohistochemistry, ELISA, Western blotting, and real-time polymerase chain reaction. TNFRII Ig treatment stabilized nephritis and markedly prolonged survival. Autoantibody production and systemic immune activation were not inhibited, but the renal response to glomerular immune complex deposition was attenuated. This was associated with decreases in renal production of chemokines, renal endothelial cell activation, interstitial F4/80(high) macrophage accumulation, tubular damage, and oxidative stress. In contrast, perivascular lymphoid aggregates containing B cells, T cells, and dendritic cells accumulated unabated. Our data suggest that TNFα is a critical cytokine that amplifies the response of the nephron to immune complex deposition, but that it has less influence on the response of the systemic vasculature to inflammation.

Discrepancies in glomerular and tubulointerstitial/vascular immune complex IgG subclasses in lupus nephritis

Lupus nephritis is characterized by glomerular and extraglomerular immune complex deposition in the kidney. It is unclear whether the same circulating immune complexes deposit in the glomeruli and in extraglomerular structures, or whether they are pathogenetically different. Differences in the IgG subclass composition may point towards different pathways in the formation of glomerular and extraglomerular immune complexes. Therefore we investigated IgG subclass distribution in the immune complex deposits at these anatomic sites. A total of 84 biopsies diagnosed as lupus nephritis and classified according to the International Society of Nephrology/Renal Pathology Society (ISN/RPS) 2003 classification, were examined by direct immunofluorescence staining for IgG subclasses. The IgG subclass composition in the glomerular, tubular basement membrane (TBM) and vascular wall deposits was compared. We also correlated the presence/absence of interstitial inflammation and IgG subclasses in the TBM and vascular deposits. Lastly, we looked for correlation between staining for IgG subclasses and complement C1q and C3 staining. IgG staining was present in the TBM in 52/84 biopsies, and in the vascular walls in 40/84 biopsies. IgG subclass distribution was discrepant between glomerular and TBM deposits in 36/52 biopsies, and between glomerular and vascular deposits in 27/40 biopsies. Interstitial inflammation did not correlate with the presence of IgG staining or distribution of IgG subclasses in the TBM. Interstitial inflammation was more common in biopsies of African-American patients than Caucasian patients. The IgG subclass staining correlated with C1q staining in all the three compartments. The antibody composition of the glomerular and extraglomerular immune complex deposits appear to differ from each other. They may not represent the same preformed immune complexes from the circulation. It is likely that their pathogenesis and site of formation are different.

Deficiency of a Transcriptional Regulator, Inhibitor of Differentiation 3, Induces Glomerulonephritis in Apolipoprotein E–Deficient Mice: A Model Linking Hyperlipidemia and Renal Disease

The clinical association between hyperlipidemia and renal disease is well established, yet hyperlipidemia as a cause for renal disease is rare. Apolipoprotein E-deficient (ApoE(-/-)) mice develop hyperlipidemia and are a model for atherosclerosis. Introducing deficiency of inhibitor of differentiation 3 (Id3) in ApoE(-/-) mice further exacerbates atherosclerosis. ID3 is a transcription regulator expressed in multiple cell types. Id3(-/-) mice develop antibodies to self-antigens and salivary gland autoimmunity. This study was undertaken to investigate a link between hyperlipidemia, autoimmunity, and renal disease. ApoE(-/-), Id3(-/-), and ApoE(-/-)Id3(-/-) double-knockout (DKO) mice were studied at different ages for renal pathological features and function. Serum samples were analyzed for the presence of autoantibodies. At 16 weeks, DKO mice developed mesangioproliferative glomerulonephritis (GN), leading to severe proteinuria. GN was associated with glomerular deposition of lipids and immune complexes and with macrophage infiltration. DKO mice had high levels of circulating autoantibodies. Although ApoE(-/-) mice had glomerular lipid deposits and Id3(-/-) mice had circulating autoantibodies, neither group of age-matched single-knockout mice developed GN. These data provide support for the hypothesis that induction of renal disease in hyperlipidemia is dictated by additional factors. Our study shows that some of these factors are regulated by ID3. Thus, ID3 is a novel risk factor linking cardiovascular and renal disease.

Abstract 3632: Nonclinical pharmacokinetics and safety of Angiocal, the first VEGF-A-specific alternative scaffold protein entering clinical development for cancer

Abstract Anticalins are high affinity scaffold proteins based on human lipocalins and represent a new class of biologics. Although lipocalins share limited sequence identity among each other they are all made up of a single conserved beta-barrel. The four loops protruding from the opening of the calyx contribute to the observed various binding functions of different lipocalins. The loop residues of human tear lipocalin were randomized to generate a combinatorial library and successive rounds of panning and screening were employed to generate an Anticalin with high affinity and specificity for VEGF-A, Angiocal. Angiocal was found to antagonize VEGF-A function by preventing its interaction with cognate membrane receptors. Following the initial characterization in cell-based and in vivo models as communicated previously (AACR 2008 #4077, AACR 2009 #2318) we sought to estimate the human pharmacokinetics of Angiocal by interspecies scaling. Therefore, PK profiles in mice, rats and cynomolgus monkeys were obtained and will be presented. Therapeutic antibodies such as bevacizumab are usually well tolerated while significant toxicities occur in a subset of patients, for example leading to an enhanced risk for thromboembolic events. It has been demonstrated that bevacizumab forms multimeric immune complexes in vivo which may be a cause for these effects. Furthermore, immune complex deposition in glomeruli of the kidney may cause glomerulosclerosis. With respect to thromboembolic complications of bevacizumab use, these were mirrored in human FcgammaIIa receptor transgenic mice where administration of complexes between heparin, Bevacizumab and heparin-binding isoforms of its VEGF-A target lead to platelet aggregation and thrombosis (Meyer, T. et al. J. Thromb. Haemost. 2009, 7: 171-181). Angiocal was tested in the same model and does not cause any of these adverse effects on platelets in vivo. GLP toxicology studies with Angiocal were performed in two relevant species to determine the NOAEL. In addition, we did not observe effects on inflammatory cytokines or complement factors in these studies while exaggerated pharmacodynamic effects consistent with potent VEGF neutralization were seen. Angiocal is currently undergoing phase Ib clinical testing in cancer patients to establish Anticalins as novel and safe class of therapeutic molecules. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3632. doi:10.1158/1538-7445.AM2011-3632

Nephritogenic antibodies bind in glomeruli through interaction with exposed chromatin fragments and not with renal cross-reactive antigens

Cross-reactivity of anti-double stranded DNA (anti-dsDNA) antibodies with glomerular antigens has been postulated as a key factor in the development of lupus nephritis. Because no direct proof has been presented on anti-dsDNA antibodies binding in vivo to glomerular structures, we have analysed the binding of potentially nephritogenic anti-dsDNA antibodies to α-actinin and laminin. By enzyme-linked immunosorbent assay and surface plasmon resonance (SPR) analyses, we demonstrate that monoclonal antibodies (mAbs) bind both double-stranded DNA and α-actinin at high affinity. However, when added to nephritic kidney sections they did not bind to such structures, but rather to nucleosome-containing structures within the mesangial matrix or the glomerular basement membranes (GBMs). Nucleosomes, anti-nuclear antibodies and complexes of them were tested for their binding to glomerular components such as agrin, perlecan and laminin using SPR analysis. Nucleosomes bound to laminin, marginally to agrin, but not to perlecan or heparan sulphate-depleted agrin. Anti-histone H2B and anti-nucleosome antibodies in complex with nucleosomes slightly increased the binding of nucleosomes to agrin, while binding to laminin was slightly decreased compared to nucleosomes alone. In conclusion, the availability of nucleosomal antigens and the binding of these antigens to components of the mesangial matrix and GBM seem crucial for the glomerular deposition of immune complexes.

Novel Therapeutic Approaches to Lupus Glomerulonephritis: Translating Animal Models to Clinical Practice

Systemic lupus erythematosus is a chronic autoimmune disease frequently affecting the kidney. Renal involvement is characterized by glomerular immune complex deposits and proliferative glomerulonephritis progressing to glomerulosclerosis and kidney failure. The development of systemic lupus erythematosus is regulated genetically, and lupus susceptibility genes have been linked to immune hyper-responsiveness and loss of immune regulation. In addition to the systemic immune defects, recent studies in animal models show that susceptibility to lupus nephritis is influenced by intrinsic renal factors. Thus, renal cell responses to immune-mediated glomerular injury determine disease outcome. This supports the idea that future treatments for lupus nephritis need to focus on regulating end-organ responses. The feasibility of this approach has been shown in animal models of kidney disease. For more than 50 years, the emphasis in management of lupus nephritis has been suppression of autoimmune responses and systemic control of inflammation. This review describes recently developed targeted drug delivery technologies and potential targets that can regulate glomerular cell responses, offering a novel therapeutic approach for lupus nephritis.

Interferon‐γ–dependent inhibition of B cell activation by bone marrow–derived mesenchymal stem cells in a murine model of systemic lupus erythematosus

Bone marrow-derived mesenchymal stem cells (BM-MSCs) are multipotent cells characterized by immunomodulatory properties and are therefore considered a promising tool for the treatment of immune-mediated diseases. This study was undertaken to assess the influence of murine BM-MSCs on the activation of B cells in (NZB × NZW)F(1) mice as an animal model of systemic lupus erythematosus (SLE). We evaluated the in vitro effects of BM-MSCs on the proliferation and differentiation to plasma cells of splenic mature B cell subsets, namely follicular and marginal zone B cells isolated from (NZB × NZW)F(1) mice. Lupus mice were also treated with BM-MSCs, and serum autoantibodies, proteinuria, histologic changes in the kidney, and survival rates were monitored. BM-MSCs inhibited antigen-dependent proliferation and differentiation to plasma cells of follicular and marginal zone B cells in vitro. This inhibitory effect was dependent on interferon-γ (IFNγ) and was mediated by cell-to-cell contact, involving the programmed death 1 (PD-1)/PD ligand pathway. In vivo treatment with BM-MSCs did not affect the levels of anti-double-stranded DNA antibodies or proteinuria. However, a reduction in glomerular immune complex deposition, lymphocytic infiltration, and glomerular proliferation was observed. Our findings indicate that BM-MSCs affect B cell receptor-dependent activation of both follicular and marginal zone B cells from lupus mice. This inhibitory effect is IFNγ-dependent and cell contact-dependent. MSCs in vivo do not affect the production of autoantibodies, the level of proteinuria, or the mortality rates. Nonetheless, the significant improvement in histologic findings in the kidney supports the potential role of MSCs in the prevention of glomerular damage.

Allogeneic mesenchymal stem cells do not protect NZB × NZW F1 mice from developing lupus disease

Mesenchymal stem cell (MSC) therapy has shown promise clinically in graft-versus-host disease and in preclinical animal models of T helper type 1 (Th1)-driven autoimmune diseases, but whether MSCs can be used to treat autoimmune disease in general is unclear. Here, the therapeutic potential of MSCs was tested in the New Zealand black (NZB)xNew Zealand white (NZW) F1 (NZB/W) lupus mouse model. The pathogenesis of systemic lupus erythematosus involves abnormal B and T cell activation leading to autoantibody formation. To test whether the immunomodulatory activity of MSCs would inhibit the development of autoimmune responses and provide a therapeutic benefit, NZB/W mice were treated with Balb/c-derived allogeneic MSCs starting before or after disease onset. Systemic MSC administration worsened disease and enhanced anti-double-stranded DNA (dsDNA) autoantibody production. The increase in autoantibody titres was accompanied by an increase in plasma cells in the bone marrow, an increase in glomerular immune complex deposition, more severe kidney pathology, and greater proteinuria. Co-culturing MSCs with plasma cells purified from NZB/W mice led to an increase in immunoglobulin G antibody production, suggesting that MSCs might be augmenting plasma cell survival and function in MSC-treated animals. Our results suggest that MSC therapy may not be beneficial in Th2-type T cell- and B cell-driven diseases such as lupus and highlight the need to understand further the appropriate application of MSC therapy.

Glomerular Antibodies in Lupus Nephritis

Lupus nephritis (LN) remains the most common severe manifestation of systemic lupus erythematosus (SLE) characterized by the presence of autoantibodies (Abs) that are believed to play a central role in the pathogenesis of LN. Among more than 100 Abs reported in SLE, only a few display a direct glomerular binding capacity. Such antiglomerular Abs are detected at the onset of the disease before antinuclear Abs detection and proteinuria, this detection is associated with the related autoantigen overexpression. Antiglomerular Abs are able to interfere with cell metabolism, to penetrate living cells, and to induce glomerular cell proliferation. In addition, antiglomerular Abs could be nephritogenic causing proteinuria, particularly when they cross-react with anti-dsDNA Abs. Antiglomerular Abs encompass anti-α-actinin, anti-laminin-1, antifibronectin, antimyosin, and anticollagen Abs. The pathogenic activity of anti-α-actinin Abs has been demonstrated in non-autoimmune mice after immunization with α-actinin, but not with dsDNA, leading to a SLE-like disease with proteinuria and glomerular immune complex deposition. Similarly, extracorporeal immunoabsorption to remove anti-laminin-1 Abs reduces kidney-Abs deposition and proteinuria in mice and humans proving their pathogenic effect. Altogether this suggests that antiglomerular Abs participate, at least at the beginning, in the glomerular immune complex deposition and in the kidney damage.

From mother to child--transplacental effect of AT1R-AAin preeclampsia

Preeclampsia is a common hypertensive disorder of pregnancy and a leading cause of maternal and foetal morbidity and mortality worldwide. Preeclampsia requires the presence of the placenta and generally dramatically resolves after placental delivery. The abnormal placentation with failure of trophoblast remodelling of uterine spiral arterioles represents a point where current theories on mechanisms responsible for the condition converge [1]. Various pathways have been proposed to contribute to placental disease. Two major recent concepts, namely, autoimmunity and anti-angiogenesis, have helped us gain new insights into this ‘disease of theories’. Possible mediators leading to impaired angiogenesis in the placenta were recently reviewed [2]. The autoimmunity notion received support with the discovery of autoantibodies directed against the angiotensin (Ang) II Type 1 receptor (AT1R-AA) in the serum of preeclamptic women [3]. AT1R-AA activate the AT1R and induce a cascade of events in various cell types, similar to the actions of Ang II [4]. Increased oxidative stress, increased production of soluble fms-like tyrosine kinase (sFlt-1) in the placenta and initiation of pro-inflammatory and pro-coagulation responses all appear to be key mechanisms resulting from AT1R-AA actions [5]. AT1R-AA were also found in a rodent model for preeclampsia. In that model, the dams of female rats transgenic for the human angiotensinogen gene crossed with male rats transgenic for the human renin gene developed severe (telemetrymeasured) hypertension and albuminuria in the latter half of pregnancy, accompanied by glomerular endotheliosis [6]. Thus, many features of the preeclampsia-related maternal syndrome including hypertension, proteinuria and generalized endothelial dysfunction were attributed to circulating AT1R-AA. Preeclamptic AT1R-AA are IgG3 subclass immunoglobulins that target the structures contained in the second extracellular loop of AT1R and induce agonistic responses similar to Ang II despite a different binding site from the natural ligand [3]. Their actions can be neutralized with the corresponding seven-amino-acid peptide sequence or pharmacologic blockade of the AT1R. Recent studies on the pathogenesis of preeclampsia focused mainly on the features of the maternal syndrome, as preeclampsia can lead to serious maternal and foetal complications. Agonistic antibody-mediated AT1R stimulation has been demonstrated in severe vascular renal allograft rejection and the passive transfer of human IgG containing AT1R-AA induced vascular lesions similar to the human disease. Furthermore, AT1R-AA led to increased blood pressure in otherwise non-rejecting and normotensive transplanted animals [7]. Investigators from the University of Texas in Houston pursued a similar strategy of passive human IgG transfer. They recently showed that AT1R-AA recovered from the circulation of women with preeclampsia induced preeclampsia-like generalized endothelial dysfunction in pregnant mice. Short duration (5 days) of the passive transfer induced an increase in tail-cuff blood pressure measurements. Links to impaired placental angiogenesis was demonstrated with an increase in sFlt concentrations in the serum of these pregnant mice [8]. sFlt is a shorter splice variant of the functional receptor that lacks the transmembrane domain. The shortened version interferes with angiogenesis and thereby placental development. Together with previous f indings implicating overproduction of plasminogen activator inhibitor-1 and tissue factor in human trophoblast cells, their findings provided further evidence that AT1R-AA may have a causative role in abnormal placentation. Some prototypic features of maternal syndrome in terms of swelling of the endothelial cells (glomerular endotheliosis) were found in the antibody-transferred pregnant mice. However, the mouse model differed from the human disease. For instance, electron microscopic analysis revealed subendothelial deposits of immune complexes. Glomerular immune complex deposition is not common in human preeclampsia [9] and it remains to be determined whether or not the mice developed antibodies against human AT1R-AA IgG used in the transfer experiments. The team from Houston now focused on foetal complications. Intrauterine growth restriction (IUGR) can be

FTY720 exerts a survival advantage through the prevention of end-stage glomerular inflammation in lupus-prone BXSB mice

FTY720 is a novel investigational agent targeting the sphingosine 1-phosphate (S1P) receptors with an ability to cause immunosuppression by inducing lymphocyte sequestration in lymphoid organs. Systemic lupus erythematosus (SLE) is refractory autoimmune disease characterized by the production of a wide variety of autoantibodies and immune complex (IC)-mediated lupus nephritis. Among several SLE-prone strains of mice, BXSB is unique in terms of the disease-associated monocytosis in periphery and the reduced frequency of marginal zone B (MZ B) cells in spleen. In the present study, we examined the effect of FTY720 on lupus nephritis of BXSB mice. FTY720 treatment resulted in a marked decrease in lymphocytes, but not monocytes, in peripheral blood, and caused relocalization of marginal zone B (MZ B) cells into the follicle in the spleen. These changes did not affect the production of autoantibodies, thus IgG and C3 were deposited in glomeruli in FTY720-treated mice. Despite these IC depositions, FTY720-treated mice showed survival advantage with the improved proteinuria. Histological analysis revealed that FTY720 suppressed mesangial cell proliferation and inflammatory cell infiltration. These results suggest that FTY720 ameliorates lupus nephritis by inhibiting the end-stage inflammatory process following IC deposition in glomeruli.

Cytokine Overproduction, T-Cell Activation, and Defective T-Regulatory Functions Promote Nephritis in Systemic Lupus Erythematosus

Lupus nephritis (LN) occurs in more than one-third of patients with systemic lupus erythematosus. Its pathogenesis is mostly attributable to the glomerular deposition of immune complexes and overproduction of T helper- (Th-) 1 cytokines. In this context, the high glomerular expression of IL-12 and IL-18 exerts a major pathogenetic role. These cytokines are locally produced by both macrophages and dendritic cells (DCs) which attract other inflammatory cells leading to maintenance of the kidney inflammation. However, other populations including T-cells and B-cells are integral for the development and worsening of renal damage. T-cells include many pathogenetic subsets, and the activation of Th-17 in keeping with defective T-regulatory (Treg) cell function regards as further event contributing to the glomerular damage. These populations also activate B-cells to produce nephritogenic auto-antibodies. Thus, LN includes a complex pathogenetic mechanism that involves different players and the evaluation of their activity may provide an effective tool for monitoring the onset of the disease.

Pure anti-dsDNA mAbs need chromatin structures to promote glomerular mesangial deposits in BALB/c mice

The glomerular targets for nephritogenic antibodies have been identified as membrane-associated chromatin fragments. The processes responsible for their deposition are poorly understood. To determine early events in antibody-mediated nephritis, we injected highly pure anti-dsDNA mAbs into BALB/c mice. Mice receiving one dose of anti-dsDNA mAbs were sacrificed 6 or 24 h later. No direct binding of mAbs to glomerular membranes or to the mesangial matrix was observed by immune electron microscopy. In contrast, repeated injections of the same antibodies over 4 weeks resulted in deposition of electron dense structures predominantly in the mesangial matrix. These structures contained mAbs and chromatin fragments as determined by co-localization immune electron microscopy. Biotinylated anti-dsDNA mAbs, injected into nephritic (NZB × NZW)F1 or MRLlpr/lpr mice were detected in newly formed electron dense structures within glomerular capillary membranes. There were no correlation between mAb affinity for DNA, as determined by surface plasmon resonance analyses, and ability to bind chromatin fragments in vivo. No direct binding of mAbs to inherent membrane antigens was observed. Quantification of DNA in sera before and after one single injection of antibodies revealed increased DNA levels at 6 h after injection of anti-dsDNA mAb, and lower levels after 24 h. Repeated injections of anti-dsDNA caused an increase in circulating DNA. These results indicate that availability of chromatin fragments, presumable in circulation, is important for glomerular mesangial matrix deposition of anti-dsDNA antibody-containing immune complexes in context of lupus nephritis.

A New Model of Induced Experimental Systemic Lupus Erythematosus (SLE) in Pigs and Its Amelioration by Treatment with a Tolerogenic Peptide

Systemic lupus erythematosus (SLE) is characterized by a variety of autoantibodies and systemic clinical manifestations. A tolerogenic peptide, hCDR1, ameliorated lupus manifestations in mice models. The objectives of this study were to induce experimental SLE in pigs and to determine the ability of hCDR1 to immunomodulate the disease manifestations. We report here the successful induction, by a monoclonal anti-DNA antibody, of an SLE-like disease in pigs, manifested by autoantibody production and glomerular immune complex deposits. Treatment of pigs with hCDR1 ameliorated the lupus-related manifestations. Furthermore, the treatment downregulated the gene expression of the pathogenic cytokines, interleukin (IL)-1beta, tumor necrosis factor alpha, interferon gamma, and IL-10, and upregulated the expression of the immunosuppressive cytokine transforming growth factor beta, the antiapoptotic molecule Bcl-xL, and the suppressive master gene, Foxp3, hence restoring the expression of the latter to normal levels. Thus, hCDR1 is capable of ameliorating lupus in large animals and is a potential candidate for the treatment of SLE patients.

Oversecretion of Cytokines and Chemokines in Lupus Nephritis Is Regulated by Intraparenchymal Dendritic Cells

Lupus nephritis (LN) occurs in more than one-third of patients with systemic lupus erythematosus. Its pathogenesis is attributed to the glomerular deposition of immune complexes as well as to imbalance of the cytokine homeostasis. In this context, high production of cytokines and chemokines by dendritic cells (DCs) may concur to LN. In addition, urinary cytokine excretion may reflect the accumulation of DCs within glomeruli. DCs are differentiated in both myeloid and plasmacytoid (p) subsets in relation to their typical antigen and chemokine expression. Both subsets migrate in response to chemotactic stimuli because pDCs are susceptible to IL-18 expressed by resident glomerular cells. pDCs bear the IL-18R, and it is conceivable that DCs migrate to the kidney under the attraction of IL-18. Therefore, the depletion of DCs reflects the inflammation severity in LN, whereas measurement of Th1 cytokines may represent an effective tool for monitoring the onset of LN.

Deletion of Activating Fcγ Receptors Does Not Confer Protection in Murine Cryoglobulinemia-Associated Membranoproliferative Glomerulonephritis

Many types of glomerulonephritis are initiated by the deposition of immune complexes, which induce tissue injury via either engagement of Fc receptors on effector cells or via complement activation. Four murine Fcgamma receptors (FcgammaRs) have been identified at present. Ligand binding to FcgammaRI, III, and IV induces cell activation via the immunoreceptor tyrosine-based activation motif on the common gamma chain (FcRgamma). In this study, FcRgamma chain knockout (FcRgamma(-/-)) mice were crossed with thymic stromal lymphopoietin transgenic (TSLPtg) mice, which develop cryoglobulinemic membranoproliferative glomerulonephritis (MPGN). Female mice were studied at 30 and 50 days of age, when MPGN is in early and fully developed stages, respectively. Both TSLPtg and TSLPtg/FcRgamma(-/-) mice developed MPGN with massive glomerular immune deposits, mesangial cell proliferation, extensive mesangial matrix accumulation, and macrophage influx. TSLPtg/FcRgamma(-/-) mice had more glomerular immune complex deposits and higher levels of circulating cryoglobulins, IgG2a, IgG2b, and IgM, compared with TSLPtg mice. TSLPtg and TSLPtg/FcRgamma(-/-) mice developed similar levels of proteinuria. These results demonstrated that deletion of activating FcgammaRs does not confer protection in this model of immune complex-mediated MPGN. The findings contradict accepted paradigms on the role of activating FcgammaRs in promoting features of glomerulonephritis as seen in other model systems. We speculate engagement of FcgammaRs on cells such as monocytes/macrophages may be important for the clearance of deposited immune complexes and extracellular matrix proteins.

Circulating chromatin–anti-chromatin antibody complexes bind with high affinity to dermo-epidermal structures in murine and human lupus nephritis

Murine and human lupus nephritis are characterized by glomerular deposits of electron-dense structures (EDS). Dominant components of EDS are chromatin fragments and IgG antibodies. Whether glomerular EDS predispose for similar deposits in skin is unknown. We analysed (i) whether dermo-epidermal immune complex deposits have similar molecular composition as glomerular deposits, (ii) whether chromatin fragments bind dermo-epidermal structures, and (iii) whether deposits in nephritic glomeruli predispose for accumulation of similar deposits in skin. Paired skin and kidney biopsies from nephritic (NZBxNZW)F1 and MRL-lpr/lpr mice and from five patients with lupus nephritis were analysed by immunofluorescence, immune electron microscopy (IEM) and co-localization TUNEL IEM. Affinity of chromatin fragments for membrane structures was determined by surface plasmon resonance. Results demonstrated (i) presence of EDS containing chromatin fragments and IgG in both organs in nephritic patients, (ii) chromatin fragments possessed high affinity for dermo-epidermal laminins and collagens, (iii) glomerular immune complex deposits did not predict similar interstitial deposits in skin, although such complexes were present in capillary lumina in glomeruli and skin of all nephritic individuals. Thus, chromatin-IgG complexes accounting for lupus nephritis seem to reach skin through circulation, but other undetermined factors are required for these complexes to deposit within skin membranes.

Blockade of the CD30/CD30L pathway inhibits renal disease in young, SLE-prone NZB/W F1 mice (50.41)

Abstract CD30 and CD30L are interacting members of the TNFR and TNF family, respectively. CD30 is expressed by subsets of activated T and B cells, whereas CD30L is expressed by subsets of activated T cells, macrophages and dendritic cells. The CD30 / CD30L interaction modulates T cell activation, germinal center formation and antibody isotype class switching. Given the importance of this pathway to B cell function, we tested the hypothesis that blockade of the CD30 / CD30L pathway would decrease or abrogate autoantibody formation and renal disease in the NZB/W F1 murine model of systemic lupus erythematosis (SLE). Young (5 mo) NZB/W F1 mice were treated with 300 μg CD30L blocking (M15-N297A) or blocking / depleting (M15-IgG2a) antibody weekly for 3 months during the onset of autoimmunity. Both treatments a) reduced the onset and severity of proteinuria, b) significantly decreased the severity of renal histologic scores, c) decreased glomerular immune complex and complement deposition and d) these effects were associated with reduced production of anti-DNA antibodies of the IgG, but not IgM isotype. CD30 / CD30L blockade may be a viable approach for the treatment of SLE.