Epidermal growth factor receptor promotes glomerular injury and renal failure in rapidly progressive crescentic glomerulonephritis

Rapidly progressive glomerulonephritis (RPGN) is a life-threatening clinical syndrome and a morphological manifestation of severe glomerular injury that is marked by a proliferative histological pattern ('crescents') with accumulation of T cells and macrophages and proliferation of intrinsic glomerular cells. We show de novo induction of heparin-binding epidermal growth factor-like growth factor (HB-EGF) in intrinsic glomerular epithelial cells (podocytes) from both mice and humans with RPGN. HB-EGF induction increases phosphorylation of the epidermal growth factor receptor (EGFR, also known as ErbB1) in mice with RPGN. In HB-EGF-deficient mice, EGFR activation in glomeruli is absent and the course of RPGN is improved. Autocrine HB-EGF induces a phenotypic switch in podocytes in vitro. Conditional deletion of the Egfr gene from podocytes of mice alleviates the severity of RPGN. Likewise, pharmacological blockade of EGFR also improves the course of RPGN, even when started 4 d after the induction of experimental RPGN. This suggests that targeting the HB-EGF-EGFR pathway could also be beneficial in treatment of human RPGN.     

Correlation of interleukin‐6 and monocyte chemotactic protein‐1 concentrations with crescent formation and myeloperoxidase‐specific anti‐neutrophil cytoplasmic antibody titer in SCG/Kj mice by treatment with anti‐interleukin‐6 receptor antibody or mizoribine

Myeloperoxidase‐specific anti‐neutrophil cytoplasmic antibody (MPO–ANCA) is associated with rapidly progressive glomerulonephritis (RPGN) and glomerular crescent formation. Pathogenic factors in RPGN were analyzed by using SCG/Kj mice, which spontaneously develop MPO–ANCA‐associated RPGN. The serum concentration of soluble IL‐6R was determined by using ELISA and those of another 23 cytokines and chemokines by Bio‐Plex analysis. Sections of frozen kidney tissue were examined by fluorescence microscopy and the CD3⁺B220⁺ T cell subset in the spleen determined by a flow cytometry. Concentrations of IL‐6 and monocyte chemotactic protein‐1 were significantly correlated with the percentages of crescent formation. Anti‐IL‐6R antibody, which has been effective in patients with rheumatoid arthritis, was administered to SCG/Kj mice to elucidate the role of IL‐6 in the development of RPGN. MPO–ANCA titers decreased after administration of anti‐IL‐6R antibody, but not titers of mizoribine, which is effective in Kawasaki disease model mice. These results suggest that IL‐6‐mediated signaling is involved in the production of MPO–ANCA.     

FcR-bearing myeloid cells are responsible for triggering murine lupus nephritis

Lupus glomerulonephritis is initiated by deposition of IgG-containing immune complexes in renal glomeruli. FcR engagement by immune complexes (IC) is crucial to disease development as uncoupling this pathway in FcRgamma(-/-) abrogates inflammatory responses in (NZB x NZW)F1 mice. To define the roles of FcR-bearing hemopoietic cells and of kidney resident mesangial cells in pathogenesis, (NZB x NZW)F1 bone marrow chimeras were generated. Nephritis developed in (NZB x NZW)F1 mice expressing activating FcRs in hemopoietic cells. Conversely, recipients of FcRgamma(-/-) bone marrow were protected from disease development despite persistent expression of FcRgamma in mesangial cell populations. Thus, activating FcRs on circulating hemopoietic cells, rather than on mesangial cells, are required for IC-mediated pathogenesis in (NZB x NZW)F1. Transgenic FcRgamma(-/-) mice expressing FcRgamma limited to the CD11b+ monocyte/macrophage compartment developed glomerulonephritis in the anti-glomerular basement disease model, whereas nontransgenic FcRgamma(-/-) mice were completely protected. Thus, direct activation of circulating FcR-bearing myeloid cells, including monocytes/macrophages, by glomerular IC deposits is sufficient to initiate inflammatory responses.     

Membranous glomerulonephritis development with Th2-type immune deviations in MRL/lpr mice deficient for IL-27 receptor (WSX-1)

MRL/lpr mice develop spontaneous glomerulonephritis that is essentially identical with diffuse proliferative glomerulonephritis (World Health Organization class IV) in human lupus nephritis. Lupus nephritis is one of the most serious complications of systemic lupus erythematosus. Diffuse proliferative glomerulonephritis is associated with autoimmune responses dominated by Th1 cells producing high levels of IFN-gamma. The initial mounting of Th1 responses depends on the function of the WSX-1 gene, which encodes a subunit of the IL-27R with homology to IL-12R. In mice deficient for the WSX-1 gene, proper Th1 differentiation was impaired and abnormal Th2 skewing was observed during infection with some intracellular pathogens. Disruption of the WSX-1 gene dramatically changed the pathophysiology of glomerulonephritis developing in MRL/lpr mice. WSX-1-/- MRL/lpr mice developed disease resembling human membranous glomerulonephritis (World Health Organization class V) with a predominance of IgG1 in glomerular deposits, accompanied by increased IgG1 and IgE in the sera. T cells in WSX-1-/- MRL/lpr mice displayed significantly reduced IFN-gamma production along with elevated IL-4 expression. Loss of WSX-1 thus favors Th2-type autoimmune responses, suggesting that the Th1/Th2 balance may be a pivotal determinant of human lupus nephritis development.     

Growth arrest-specific gene 6 is involved in glomerular hypertrophy in the early stage of diabetic nephropathy

Nephropathy is one of the most common complications of diabetes mellitus. Glomerular hypertrophy is a hallmark in the early phase of the nephropathy. The mechanism of glomerular hypertrophy, however, remains incompletely understood. We have reported that Gas6 (growth arrest-specific gene 6) and its receptor, Axl, play a key role in the development of glomerulonephritis. Here we show the important role of Gas6/Axl in the pathogenesis of diabetic glomerular hypertrophy. In streptozotocin (STZ)-induced diabetic rats, mesangial and glomerular hypertrophy and an increase in the glomerular filtration rate (GFR) and albuminuria were observed after 12 weeks of STZ injection. The glomerular expression of Gas6 and Axl was increased in those rats. Administration of warfarin inhibited mesangial and glomerular hypertrophy and the increase in GFR and albuminuria in STZ rats. Moreover, we found less mesangial hypertrophy in STZ-treated Gas6 knockout mice than control mice. In vitro we found that stimulation of mesangial cells with Gas6 resulted in mesangial cell hypertrophy. Thus we have found a novel mechanism of glomerular hypertrophy through the Gas6/Axl-mediated pathway in the development of diabetic nephropathy. Inhibition of the Gas6/Axl pathway in diabetic patients might be beneficial to slow down the progression of diabetic nephropathy.     

B Cell and BAFF dependence of IFN-α-exaggerated disease in systemic lupus erythematosus-prone NZM 2328 mice

IFN-α is a potent activator of innate and adaptive immunity, and its administration to preautoimmune (NZB×NZW)F1 mice promotes virulent systemic lupus erythematosus (SLE) disease. Given the known contributions of B cells and BAFF to SLE, we evaluated the ability of IFN-α administration to induce disease in wild-type (WT), B cell-deficient, and BAFF-deficient NZM 2328 mice. Whereas WT mice rapidly developed proliferative glomerulonephritis, marked proteinuria, and increased mortality in response to IFN-α administration, B cell-deficient mice developed neither renal pathology nor clinical disease. Moreover, BAFF-deficient mice, despite developing limited glomerular IgG and C3 deposition, also remained free of histological glomerulonephritis and clinical disease. Strikingly, similar T cell expansion and serum IgG responses were observed in adenovirus (Adv)-IFN-treated WT and BAFF-deficient mice despite their disparate pathological and clinical responses, whereas numbers of activated B cells increased in WT mice but not in BAFF-deficient mice. Nonetheless, B cell, plasma cell, and T cell infiltration of the kidneys in Adv-IFN-treated WT mice was similar to that in WT mice treated with Adv-control. Its ability to promote SLE disease in WT mice notwithstanding, IFN-α administration failed to drive the preferential expansion of CD4(+) memory T cells that occurs during the natural course of disease, and glomerular infiltration of macrophages failed to associate with development of disease. These results collectively suggest that therapeutic targeting in SLE of BAFF and/or B cells in SLE could be successful even in states of IFN-α overexpression. Moreover, our results document important biological differences between IFN-α-driven and spontaneous natural SLE disease.     

Characterization of chemokine and chemokine receptor expression during Pneumocystis infection in healthy and immunodeficient mice

We examined gene expression levels of multiple chemokines and chemokine receptors during Pneumocystis murina infection in wild-type and immunosuppressed mice, using microarrays and qPCR. In wild-type mice, expression of chemokines that are ligands for Ccr2, Cxcr3, Cxcr6, and Cxcr2 increased at days 32–41 post-infection, with a return to baseline by day 75–150. Concomitant increases were seen in Ccr2, Cxcr3, and Cxcr6, but not in Cxcr2 expression. Induction of these same factors also occurred in CD40-ligand and CD40 knockout mice but only at a much later time-point, during uncontrolled Pneumocystis pneumonia (PCP). Expression of CD4 Th1 markers was increased in wild-type mice during clearance of infection. Ccr2 and Cx3cr1 knockout mice cleared Pneumocystis infection with kinetics similar to wild-type mice, and all animals developed anti-Pneumocystis antibodies. Upregulation of Ccr2, Cxcr3, and Cxcr6 and their ligands supports an important role for T helper cells and mononuclear phagocytes in the clearance of Pneumocystis infection. However, based on the current and prior studies, no single chemokine receptor appears to be critical to the clearance of Pneumocystis.     

Suppression of Rapidly Progressive Mouse Glomerulonephritis with the Non-Steroidal Mineralocorticoid Receptor Antagonist BR-4628

Background/Aim

Steroidal mineralocorticoid receptor antagonists (MRAs) are effective in the treatment of kidney disease; however, the side effect of hyperkalaemia, particularly in the context of renal impairment, is a major limitation to their clinical use. Recently developed non-steroidal MRAs have distinct characteristics suggesting that they may be superior to steroidal MRAs. Therefore, we explored the benefits of a non-steroidal MRA in a model of rapidly progressive glomerulonephritis.

Methods

Accelerated anti-glomerular basement membrane (GBM) glomerulonephritis was induced in groups of C57BL/6J mice which received no treatment, vehicle or a non-steroidal MRA (BR-4628, 5mg/kg/bid) from day 0 until being killed on day 15 of disease. Mice were examined for renal injury.

Results

Mice with anti-GBM glomerulonephritis which received no treatment or vehicle developed similar disease with severe albuminuria, impaired renal function, glomerular tuft damage and crescents in 40% of glomeruli. In comparison, mice which received BR-4628 displayed similar albuminuria, but had improved renal function, reduced severity of glomerular tuft lesions and a 50% reduction in crescents. The protection seen in BR-4628 treated mice was associated with a marked reduction in glomerular macrophages and T-cells and reduced kidney gene expression of proinflammatory (CCL2, TNF-α, IFN-γ) and profibrotic molecules (collagen I, fibronectin). In addition, treatment with BR-4626 did not cause hyperkalaemia or increase urine Na+/K+ excretion (a marker of tubular dysfunction).

Conclusions

The non-steroidal MRA (BR-4628) provided substantial suppression of mouse crescentic glomerulonephritis without causing tubular dysfunction. This finding warrants further investigation of non-steroidal MRAs as a therapy for inflammatory kidney diseases.     

Increased susceptibility to immunologically mediated glomerulonephritis in IFN-gamma-deficient mice.

It is postulated that IFN-gamma confers susceptibility to immunologically mediated tissue injury. To test this hypothesis, we compared the intensity of accelerated anti-glomerular basement membrane glomerulonephritis between wild-type (IFN-gamma+/+) and IFN-gamma gene knockout (IFN-gamma-/-) mice. This disease model is initiated by binding of heterologous (sheep) anti-glomerular basement membrane Abs to the glomeruli of mice preimmunized with sheep IgG. The secondary cellular and humoral immune responses to the planted Ag then lead to albuminuria and glomerular pathology. We found that IFN-gamma-/- mice or IFN-gamma+/+ mice injected with IFN-gamma-neutralizing Ab develop worse albuminuria and glomerular pathology than IFN-gamma+/+ mice. The humoral response to sheep IgG (serum mouse anti-sheep IgG titers and intraglomerular mouse IgG deposits) was comparable in the IFN-gamma+/+ and IFN-gamma-/- groups. In contrast, IFN-gamma-/- mice mounted a stronger cellular immune response (cutaneous delayed-type hypersensitivity reaction) to sheep IgG than IFN-gamma+/+ mice. These findings provide evidence that endogenous IFN-gamma has a protective role in immunologically mediated glomerulonephritis initiated by foreign Ags.     

Inhibition of B cell death causes the development of an IgA nephropathy in (New Zealand white x C57BL/6)F(1)-bcl-2 transgenic mice

Little is known about the pathogenic mechanisms of IgA nephropathy, despite being the most prevalent form of glomerulonephritis in humans. We report in this study that in (New Zealand White (NZW) x C57BL/6)F(1) mice predisposed to autoimmune diseases, the expression of a human bcl-2 (hbcl-2) transgene in B cells promotes a CD4-dependent lupus-like syndrome characterized by IgG and IgA hypergammaglobulinemia, autoantibody production, and the development of a fatal glomerulonephritis. Histopathological analysis of glomerular lesions reveals that the glomerulonephritis observed in these animals resembles that of human IgA nephropathy. The overexpression of Bcl-2 in B cells selectively enhances systemic IgA immune responses to T-dependent Ags. Significantly, serum IgA purified from (NZW x C57BL/6)F(1)-hbcl-2 transgenic mice, but not from nontransgenic littermates, shows reduced levels of galactosylation and sialylation and an increased ability to deposit in the glomeruli, as observed in human patients with IgA nephropathy. Our results indicate that defects in the regulation of B lymphocyte survival associated with aberrant IgA glycosylation may be critically involved in the pathogenesis of IgA nephropathy, and that (NZW x C57BL/6)F(1)-hbcl-2 Tg mice provide a new experimental model for this form of glomerulonephritis.     

CXC chemokine receptor 4 expressed in T cells plays an important role in the development of collagen-induced arthritis

Introduction  

Chemokines and their receptors are potential therapeutic targets in rheumatoid arthritis (RA). Among these, several studies suggested the involvement of CXC chemokine 4 (CXCR4) and its ligand CXC ligand 12 (SDF-1) in RA pathogenesis. However, the role of these molecules in T-cell function is not known completely because of embryonic lethality of Cxcr4- and Cxcl12- deficient mice. In this report, we generated T cell-specific Cxcr4 -deficient mice and showed that the CXCR4 in T cells is important for the development of collagen-induced arthritis (CIA).     

Modulation of renal disease in MRL/lpr mice genetically deficient in the alternative complement pathway factor B

In systemic lupus erythematosus, the renal deposition of complement-containing immune complexes initiates an inflammatory cascade resulting in glomerulonephritis. Activation of the classical complement pathway with deposition of C3 is pathogenic in lupus nephritis. Although the alternative complement pathway is activated in lupus nephritis, its role in disease pathogenesis is unknown. To determine the role of the alternative pathway in lupus nephritis, complement factor B-deficient mice were backcrossed to MRL/lpr mice. MRL/lpr mice develop a spontaneous lupus-like disease characterized by immune complex glomerulonephritis. We derived complement factor B wild-type (B+/+), homozygous knockout (B-/-), and heterozygous (B+/-) MRL/lpr mice. Compared with B+/- or B+/+ mice, MRL/lpr B-/- mice developed significantly less proteinuria, less glomerular IgG deposition, and decreased renal scores as well as lower IgG3 cryoglobulin production and vasculitis. Serum C3 levels were normal in the B-/- mice compared with significantly decreased levels in the other two groups. These results suggest that: 1) factor B plays an important role in the pathogenesis of glomerulonephritis and vasculitis in MRL/lpr mice; and 2) activation of the alternative pathway, either by the amplification loop or by IgA immune complexes, has a prominent effect on serum C3 levels in this lupus model.     

Autoimmune glomerulonephritis induced in congenic mouse strain carrying telomeric region of chromosome 1 derived from MRL/MpJ

In lupus erythematosus-prone mice, including the BXSB, NZW and NZB strains, telomeric regions of chromosome 1 (Chr.1) contain major glomerulonephritis susceptibility loci such as Bxs3, Sle1, and Nba2. To assess whether strain MRL, a model for lupus erythematosus, had glomerulonephritis susceptibility loci on Chr.1, we created B6.MRLc1(82-100) congenic mice carrying MRL/MpJ Chr.1 (82-100 cM) based on the C57BL/6 background and investigated renal pathology. From 6 months of age, B6.MRLc1 (82-100) showed the onset of diseases such as splenomegaly due to proliferation of CD3- or B220-positive cells, glomerular damage, and an increased serum anti-dsDNA antibody concentration, and these were earlier and severer in females. The score for glomerular damage was higher in B6.MRLc1(82-100) mice over 12 months old than in C57BL/6 or even in wild-type MRL/MpJ. Immune-complex depositions were demonstrated on glomerular basement membrane in B6.MRLc1(82-100) by immunohistochemistry and electron microscopy. For the percentage of IgG1-positive glomeruli, B6.MRLc1 (82-100) had significantly higher values than C57BL/6. In evaluations of clinical parameters, serum levels of blood urea nitrogen and the anti-dsDNA antibody in B6.MRLc1(82-100) were significantly higher than those in C57BL/6. In conclusion, B6.MRLc1(82-100) clearly developed autoimmune-mediated glomerulonephritis, and we demonstrated that MRL Chr.1 contained a novel glomerulonephritis susceptibility locus. We named this locus Mag (MRL autoimmune glomerulonephritis) and it provided new insights into the genetic basis and pathogenesis of lupus nephritis.     

CD4+ T cell-associated pathophysiology critically depends on CD18 gene dose effects in a murine model of psoriasis

In a CD18 hypomorphic polygenic PL/J mouse model, the severe reduction of CD18 (beta(2) integrin) to 2-16% of wild-type levels leads to the development of a psoriasiform skin disease. In this study, we analyzed the influence of reduced CD18 gene expression on T cell function, and its contribution to the pathogenesis of this disease. Both CD4(+) and CD8(+) T cells were significantly increased in the skin of affected CD18 hypomorphic mice. But only depletion of CD4(+) T cells, and not the removal of CD8(+) T cells, resulted in a complete clearance of the psoriasiform dermatitis. This indicates a central role of CD4(+) T cells in the pathogenesis of this disorder, further supported by the detection of several Th1-like cytokines released predominantly by CD4(+) T cells. In contrast to the CD18 hypomorphic mice, CD18 null mutants of the same strain did not develop the psoriasiform dermatitis. This is in part due to a lack of T cell emigration from dermal blood vessels, as experimental allergic contact dermatitis could be induced in CD18 hypomorphic and wild-type mice, but not in CD18 null mutants. Hence, 2-16% of CD18 gene expression is obviously sufficient for T cell emigration driving the inflammatory phenotype in CD18 hypomorphic mice. Our data suggest that the pathogenic involvement of CD4(+) T cells depends on a gene dose effect with a reduced expression of the CD18 protein in PL/J mice. This murine inflammatory skin model may also have relevance for human polygenic inflammatory diseases.     

Systemic administration of naked plasmid encoding HGF attenuates puromycin aminonucleoside-induced damage of murine glomerular podocytes

Podocyte injury is considered to play important roles in the pathogenesis of human glomerular disease. There is accumulating evidence suggesting that hepatocyte growth factor (HGF) elicits preventive activity for glomerular cells in animal models of chronic renal diseases. In this study, we demonstrated that delivery of a naked plasmid vector encoding the human HGF gene into mice by a hydrodynamic-based in vivo gene transfection approach markedly reduced proteinuria and attenuated podocyte injury in a mouse model induced by puromycin aminonucleoside (PAN) injection. Systemic administration by rapid injection via the tail vein of a naked plasmid containing HGF cDNA driven under a cytomegalovirus promoter (pCMV-HGF) produced a remarkable level of human HGF protein in the circulation. Tissue distribution studies suggested that the kidney expressed a high level of the HGF transgene. Meanwhile, compared with tubules and interstitium, a higher level of exogenous HGF protein was detected in the glomeruli. Administration of pCMV-HGF dramatically abated the urine albumin excretion and podocyte injury in PAN nephropathy in mice. Exogenous expression of HGF produced evidently beneficial effects, leading to restoration of Wilms' tumor-1 (WT1) and α-actinin-4 expression and attenuation of ultrastructural damage of the podocytes. In vitro, HGF not only restored WT1 and α-actinin-4 expression but also inhibited albumin leakage of podocytes incubated with PAN in a Transwell culture chamber. These results suggest that HGF might provide a novel strategy for amelioration of podocyte injury.     

Combined VHLH and PTEN mutation causes genital tract cystadenoma and squamous metaplasia

Patients with von Hippel-Lindau (VHL) disease develop tumors in a range of tissues, but existing mouse models of Vhlh mutation have failed to reproduce these lesions. Epididymal cystadenomas arise frequently in VHL patients, but VHL mutation alone is believed to be insufficient for tumor formation, implying a requirement for cooperating mutations in epididymal pathogenesis. Here we show that epididymal cystadenomas from VHL patients frequently also lack expression of the PTEN tumor suppressor and display activation of phosphatidylinositol 3-kinase (PI3K) pathway signaling. Strikingly, while conditional inactivation of either Vhlh or Pten in epithelia of the mouse genital tract fails to produce a tumor phenotype, their combined deletion causes benign genital tract tumors with regions of squamous metaplasia and cystadenoma. The latter are histologically identical to lesions found in VHL patients. Importantly, these lesions are characterized by expansion of basal stem cells, high levels of expression and activity of HIF1alpha and HIF2alpha, and dysregulation of PI3K signaling. Our studies suggest a model for cooperative tumor suppression in which inactivation of PTEN facilitates epididymal cystadenoma genesis initiated by loss of VHL.     

Trafficking of QD-conjugated MPO-ANCA in murine systemic vasculitis and glomerulonephritis model mice

In systemic vasculitis, the serum level of myeloperoxidase (MPO)-specific anti-neutrophil cytoplasmic autoantibodies (MPO-ANCA) is significantly elevated with the progression of disease. We have established a model of murine systemic vasculitis by administration of MPO-ANCA and fungal mannoprotein to C57BL/6 mice. We examined the role of MPO and MPO-ANCA in the pathogenesis of glomerulonephritis and systemic vasculitis in this model using quantum dots (QDs). We demonstrated that QD-conjugated MPO-ANCA (ANCA-QD) visualized the translocation of MPO on the neutrophil membrane surface after stimulation with proinflammatory cytokines. We also observed that MPO translocation on neutrophils in both patients with rapid progressive glomerulonephritis and these model mice without any stimulation, suggesting that MPO translocation is certain to contribute to the development of glomerular lesion. In addition, blood flow on the kidney surface vessel was significantly decelerated in both SCG/Kj mice and this model, suggesting that ANCA induces the damage of blood vessel. These results indicate that MPO-ANCA and surface-translocated MPO on the activated neutrophils coordinately plays essential roles in the initial steps of the glomerulonephritis.     

TNF-alpha up-regulates renal MIF expression in rat crescentic glomerulonephritis.

BACKGROUND: Macrophage migration inhibitory factor (MIF) is a potent proinflammatory mediator that participates in the pathogenesis of endotoxemia and experimental crescentic glomerulonephritis. However, very little is known about how MIF production is regulated in disease. We therefore examined whether tumor necrosis factor alpha (TNF-alpha), a known inducer of MIF expression by macrophages in vitro, up-regulates local and systemic MIF expression in a macrophage-mediated rat model of crescentic glomerulonephritis. MATERIALS AND METHODS: Anti-glomerular basement membrane (GBM) glomerulonephritis was induced in groups of six primed rats. Animals were treated with 1 mg/kg soluble TNF-alpha receptor (TNFbp) or saline from the time of disease induction until they were killed on Days 1, 7, or 14. Renal MIF expression was assessed by in situ hybridization, immunohistochemistry, and ELISA, and compared with macrophage accumulation and indices of renal damage. RESULTS: Although TNFbp treatment on Day 1 of the disease had only a partial effect upon the up-regulation of glomerular MIF expression, on Days 7 to 14 it almost completely abrogated the increase in glomerular and interstitial MIF mRNA and protein expression. In addition, TNFbp treatment significantly inhibited MIF secretion by cultured glomeruli and reduced serum MIF levels. The inhibition of renal MIF expression was paralleled by a significant inhibition of glomerular and interstitial macrophage infiltration (p < 0.001 versus saline treated), a significant suppression of renal injury (proteinuria and serum creatinine), and a marked reduction in histologic damage (glomerular hypercellularity, crescent formation, and interstitial fibrosis; all p < 0.01 versus saline treated). CONCLUSIONS: This study demonstrates for the first time that TNF-alpha up-regulates local MIF expression by both infiltrating macrophages and resident kidney cells in rat crescentic glomerulonephritis. In addition, TNF-alpha regulates systemic MIF production. Thus, TNF-alpha, together with MIF, may play a pathological role in immunologically induced renal disease.     

The Spleen Plays No Role in Nephrotoxic Serum Nephritis,but Constitutes a Place of Compensatory Haematopoiesis

Background

The spleen has been implicated in the pathogenesis of immune-complex glomerulonephritis by initiating and resolving adaptive immune responses. Thus, we aimed to evaluate the role of the spleen in experimental nephrotoxic serum nephritis (NTS).

Methods

In order to accelerate the disease, animals were subjected to NTS by preimmunizing male C57BL/6J mice with rabbit IgG three days before injecting the rabbit anti-glomerular basement antiserum, or were immunized only. A group underwent splenectomy before NTS induction.

Results

We observed enlargement of the spleen with a maximum at 14 days after NTS induction or immunization only. Splenectomized mice were found to develop albuminuria and renal histological changes comparable to sham-operated controls. Nevertheless, anaemia was aggravated in mice after splenectomy. During the course of NTS, we detected CD41⁺ megakaryocytes and Ter119⁺ erythroid precursor cells in the spleen of mice with NTS and of immunized mice. Ter119⁺Cxcr4⁺ cells and the binding partner Cxcl12 increased in the spleen, and decreased in the bone marrow. This was accompanied by a significant systemic increase of interferon-gamma in the serum.

Conclusions

In summary, splenectomy does not influence the course of NTS per se, but is involved in concomitant anaemia. Extramedullary haematopoiesis in the spleen is probably facilitated through the migration of Cxcr4⁺ erythroid precursor cells from the bone marrow to the spleen via a Cxcl12 gradient and likely arises from the suppressive capacity of chronic inflammation on the bone marrow.