Interleukin-12 from intrinsic cells is an effector of renal injury in crescentic glomerulonephritis

USP25 attenuates anti-GBM nephritis in mice by negative feedback regulation of Th17 cell differentiation

PURPOSE

This study aimed to elucidate the role of USP25 in a mouse model of anti-glomerular basement membrane glomerulonephritis (anti-GBM GN).

METHODS

USP25-deficient anti-GBM GN mice were generated, and their nephritis progression was monitored. Naïve CD4+ T cells were isolated from spleen lymphocytes and stimulated to differentiate into Th1, Th2, and Th17 cells. This approach was used to investigate the impact of USP25 on CD4+ T lymphocyte differentiation in vitro. Furthermore, changes in USP25 expression were monitored during Th17 differentiation, both in vivo and in vitro.

RESULTS

USP25-/- mice with anti-GBM GN exhibited accelerated renal function deterioration, increased infiltration of Th1 and Th17 cells, and elevated RORγt transcription. In vitro experiments demonstrated that USP25-/- CD4+ T lymphocytes had a higher proportion for Th17 cell differentiation and exhibited higher RORγt levels upon stimulation. Wild-type mice with anti-GBM GN showed higher USP25 levels compared to healthy mice, and a positive correlation was observed between USP25 levels and Th17 cell counts. Similar trends were observed in vitro.

CONCLUSION

USP25 plays a crucial role in mitigating renal histopathological and functional damage during anti-GBM GN in mice. This protective effect is primarily attributed to USP25's ability to inhibit the differentiation of naïve CD4+ T cells into Th17 cells. The underlying mechanism may involve the downregulation of RORγt. Additionally, during increased inflammatory responses or Th17 cell differentiation, USP25 expression is activated, forming a negative feedback regulatory loop that attenuates immune activation.

Pathogenic T-Cell Responses in Immune-Mediated Glomerulonephritis

Glomerulonephritis (GN) comprises a group of immune-mediated kidney diseases affecting glomeruli and the tubulointerstitium. Glomerular crescent formation is a histopathological characteristic of severe forms of GN, also referred to as crescentic GN (cGN). Based on histological findings, cGN includes anti-neutrophil cytoplasmic antibody (ANCA)-associated GN, a severe form of ANCA-associated vasculitis, lupus nephritis associated with systemic lupus erythematosus, Goodpasture’s disease, and IgA nephropathy. The immunopathogenesis of cGN is associated with activation of CD4+ and CD8+ T cells, which particularly accumulate in the periglomerular and tubulointerstitial space but also infiltrate glomeruli. Clinical observations and functional studies in pre-clinical animal models provide evidence for a pathogenic role of Th1 and Th17 cell-mediated immune responses in cGN. Emerging evidence further argues that CD8+ T cells have a role in disease pathology and the mechanisms of activation and function of recently identified tissue-resident CD4+ and CD8+ T cells in cGN are currently under investigation. This review summarizes the mechanisms of pathogenic T-cell responses leading to glomerular damage and renal inflammation in cGN. Advanced knowledge of the underlying immune mechanisms involved with cGN will enable the identification of novel therapeutic targets for the replacement or reduction in standard immunosuppressive therapy or the treatment of refractory disease.

Overexpression of toll-like receptor 9 correlates with podocyte injury in a murine model of autoimmune membranoproliferative glomerulonephritis

Toll-like receptors (Tlrs) are sensors of danger signals which promote the activation of immune cells and intrinsic renal cells. Podocytes, the intrinsic cells of glomerulus, are continuously exposed to various plasma solutes and danger signals due to their unique location in the glomerulus. Herein, we show that Tlr9 is overexpressed in podocytes and the mechanisms which cause its injury and development of membranoproliferative glomerulonephritis (MPGN) in model BXSB/MpJ-Yaa (Yaa) mice. Yaa mice developed typical lesions of MPGN and showed strong expression of Tlr9 mRNA throughout the glomerulus particularly toward the periphery of the glomerulus. However, BXSB/MpJ (BXSB) mice showed no lesion for MPGN but a very weak expression of Tlr9 mRNA. Relative mRNA expression of Tlr9 and its downstream cytokines, including interleukin 1 beta (Il1b), Il6, interferon gamma (Ifng) and tumour necrosis factor alpha (Tnfa) was markedly increased in glomeruli isolated from Yaa mice. Tlr9 protein expression was almost absent in BXSB mice but intense expression was found in Yaa mice. Podocyte protein expression was normal in BXSB mice but decreased in Yaa mice and colocalized with Tlr9 protein. Furthermore, electron microscopy examination revealed podocyte injury and electron-dense materials in thickened glomerular basement membrane of Yaa mice. Glomerular Tlr9 mRNA expression was significantly correlated with anti-dsDNA antibody, proteinuria, renal function indices (sBUN and sCr), glomerular histopathology indices, downstream factors of Tlr family (Ilb and Tnfa), podocyte injury parameters (p < .05 and p < .01). In conclusion, overexpression of TLR9 correlates with podocyte injury and development of MPGN.

The association between interleukin-19 concentration and diabetic nephropathy

Background

Interleukin-19 (IL-19) is a newly discovered cytokine belonging to the Interleukin-10(IL-10) family. IL-19 have indispensable functions in many inflammatory processes and also can induce the angiogenic potential of endothelial cells. The purpose of present study was to investigate the relation of serum interleukin-19 (IL-19) levels with diabetic nephropathy (DN).

Methods

Two hundred study groups of patients with type 2 diabetes mellitus (T2DM) (109 males and 91 females) were recruited, included normoalbuminuria(n = 102), microalbuminuria(n = 72) and macroalbuminuria(n = 26) . The 50 healthy blood donors were enrolled for the control group. All subjects were assessed for: IL-19, High-sensitivity C-reactive protein (Hs-CRP), Cystatin C, urinary albumin excretion rate (UAE) and glycosylated hemoglobin A1c(HbA1c).

Results

The serum IL-19 levels in DN patients were found to be significantly higher compared to controls. IL-19 levels were significantly positively correlated with Hs-CRP, Cystatin C, UAE and HbA1c(r = 0.623, 0.611,0.591 and 0.526 respectively, P < 0.01). Multivariable logistic regression analysis showed IL-19 levels (P = 0.01) were found to be independently associated with patients with DN.

Conclusions

IL-19 is significantly positive correlated with UAE and Cystatin C. IL-19 may play an important role that contributes to the progression of diabetic nephropathy.

The Players: Cells Involved in Glomerular Disease

Glomerular diseases are common and important. They can arise from systemic inflammatory or metabolic diseases that affect the kidney. Alternately, they are caused primarily by local glomerular abnormalities, including genetic diseases. Both intrinsic glomerular cells and leukocytes are critical to the healthy glomerulus and to glomerular dysregulation in disease. Mesangial cells, endothelial cells, podocytes, and parietal epithelial cells within the glomerulus all play unique and specialized roles. Although a specific disease often primarily affects a particular cell type, the close proximity, and interdependent functions and interactions between cells mean that even diseases affecting one cell type usually indirectly influence others. In addition to those cells intrinsic to the glomerulus, leukocytes patrol the glomerulus in health and mediate injury in disease. Distinct leukocyte types and subsets are present, with some being involved in different ways in an individual glomerular disease. Cells of the innate and adaptive immune systems are important, directing systemic immune and inflammatory responses, locally mediating injury, and potentially dampening inflammation and facilitating repair. The advent of new genetic and molecular techniques, and new disease models means that we better understand both the basic biology of the glomerulus and the pathogenesis of glomerular disease. This understanding should lead to better diagnostic techniques, biomarkers, and predictors of prognosis, disease severity, and relapse. With this knowledge comes the promise of better therapies in the future, directed toward halting pathways of injury and fibrosis, or interrupting the underlying pathophysiology of the individual diseases that lead to significant and progressive glomerular disease.

Selective Dependence of Kidney Dendritic Cells on CX3CR1--Implications for Glomerulonephritis Therapy

As central regulators of the adaptive immune response, dendritic cells (DCs) are found in virtually all lymphatic and non-lymphatic organs. A compact network of DCs also spans the kidneys. DCs play a central role in maintenance of organ homeostasis as well as in induction of immune responses against invading pathogens. They can mediate protective or destructive functions in a context-dependent manner.We recently identified CX(3)CR1 as a kidney-specific "homing receptor" for DCs. There was a strong reduction of DCs in the kidneys of CX(3)CR1-deficient mice compared to controls. This reduction was not observed in other organs except the small intestine. As a possible underlying reason we found a strong expression of the CX(3)CR1 ligand fractalkine in the kidneys. Due to this CX(3)CR1-dependent reduction of DCs, especially in the renal cortex, a glomerulonephritis (GN) model was ameliorated in CX(3)CR1-deficient mice. In contrast, the immune defense against the most common renal infection, bacterial pyelonephritis (PN), was not significantly influenced by CX(3)CR1-deficiency. This was explained by the much smaller CX(3)CR1-dependency of medullary DCs, which recruit effector cells into the kidney during PN. Additionally, once neutrophils had been recruited by mechanisms distinct from CX(3)CR1, they carried out some of the functions of DCs.Taken together, we suggest CX(3)CR1 as a therapeutic target for GN treatment, as the absence of CX(3)CR1 selectively influences DCs in the kidney without rendering mice more susceptible towards bacterial kidney infections.

Janus kinase 3 regulates renal 25-hydroxyvitamin D 1α-hydroxylase expression, calcitriol formation, and phosphate metabolism

Calcitriol, a powerful regulator of phosphate metabolism and immune response, is generated by 25-hydroxyvitamin D 1α-hydroxylase in the kidney and macrophages. Renal 1α-hydroxylase expression is suppressed by Klotho and FGF23, the expression of which is stimulated by calcitriol. Interferon γ (INFγ) regulates 1α-hydroxylase expression in macrophages through transcription factor interferon regulatory factor-1. INFγ-signaling includes Janus kinase 3 (JAK3) but a role of JAK3 in the regulation of 1α-hydroxylase expression and mineral metabolism has not been shown. Thus, the impact of JAK3 deficiency on calcitriol formation and phosphate metabolism was measured. Renal interferon regulatory factor-1 and 1α-hydroxylase transcript levels, serum calcitriol and FGF23 levels, intestinal phosphate absorption as well as absolute and fractional renal phosphate excretion were significantly higher in jak3 knockout than in wild-type mice. Coexpression of JAK3 increased the phosphate-induced current in renal sodium-phosphate cotransporter-expressing Xenopus oocytes. Thus, JAK3 is a powerful regulator of 1α-hydroxylase expression and phosphate transport. Its deficiency leads to marked derangement of phosphate metabolism.

Spleen tyrosine kinase inhibition attenuates autoantibody production and reverses experimental autoimmune GN

Spleen tyrosine kinase (SYK) has an important role in immunoreceptor signaling, and SYK inhibition has accordingly attenuated immune-mediated injury in several in vivo models. However, the effect of SYK inhibition on autoantibody production remains unclear, and SYK inhibition has not been studied in an autoimmune model of renal disease. We, therefore, studied the effect of SYK inhibition in experimental autoimmune GN, a rodent model of antiglomerular basement membrane disease. We show glomerular SYK expression and activation by immunohistochemistry in both experimental and clinical disease, and we show that treatment with fostamatinib, a small molecule kinase inhibitor selective for SYK, completely prevents the induction of experimental autoimmune GN. In established experimental disease, introduction of fostamatinib treatment led to cessation of autoantibody production, reversal of renal injury, preservation of biochemical renal function, and complete protection from lung hemorrhage. B cell ELISpot and flow cytometric analysis suggest that short-term fostamatinib treatment inhibits the generation and activity of antigen-specific B cells without affecting overall B-cell survival. Additionally, fostamatinib inhibited proinflammatory cytokine production by nephritic glomeruli ex vivo and cultured bone marrow-derived macrophages in vitro, suggesting additional therapeutic effects independent of effects on autoantibody production that are likely related to inhibited Fc receptor signaling within macrophages in diseased glomeruli. Given these encouraging results in an in vivo model that is highly applicable to human disease, we believe clinical studies targeting SYK in GN are now warranted.

Interleukin-18 contributes more closely to the progression of diabetic nephropathy than other diabetic complications

Diabetic complication is comprised of a wide variety of pathophysiological factors involving proinflammatory cytokines, adipokines, and oxidative stress, among others. Each of these complications differs in their incidence and the stage of their occurrence. We examined cytokines and stress markers in 48 patients with type 2 diabetes mellitus and compared the difference of their contribution to pathogenesis between nephropathy and other diabetic complications. Hemoglobin A1c correlated with the level of low-density lipoprotein-cholesterol, and significantly elevated in the severe macroangiopathy group. Cystatin C increased in the severe microangiopathy groups but did not increase in the macroangiopathy group. The levels of interleukin 18 (IL-18), high-sensitive CRP (H-CRP), liver-type fatty acid binding protein, and 8-hydroxy-2-deoxyguanosine increased in the severe microangiopathy group. These data suggest the participation of proinflammatory signaling and oxidative stress in the progression of microangiopathy. In particular, IL-18 and H-CRP were significantly elevated only in the severe nephropathy group but did not significantly elevate in other complications. These data suggest another effect of IL-18 on glomerulus in addition to its proinflammatory effect. In conclusion, we propose that IL18 has a specific role that contributes more closely to the progression of diabetic nephropathy than other diabetic complications.

Kidney Dendritic Cells Become Pathogenic during Crescentic Glomerulonephritis with Proteinuria

It is unclear why kidney dendritic cells attenuate some models of kidney disease but aggravate others. Kidney dendritic cells ameliorate the early phase of nonaccelerated nephrotoxic nephritis, a murine model of crescentic glomerulonephritis, but their effect on the later phase is unknown. Here, we report that kidney dendritic cells at later stages of nephrotoxic nephritis expressed higher levels of costimulatory molecules but lower levels of the cosuppressor molecule ICOS-L and started production of IL-12/23p40 and TNF-α. Furthermore, we noted that kidney dendritic cells captured more filterable antigen in proteinuric mice at late time points of nephrotoxic nephritis and started to capture molecules that were too large for filtration by a healthy kidney. They presented filtered antigen to Th cells, which responded by producing the proinflammatory cytokines IL-2, IFN-γ, TNF-α, IL-6, and IL-17. Notably, production of the suppressive cytokine IL-10 further increased in late nephrotoxic nephritis. Depletion of kidney dendritic cells at a late stage attenuated nephrotoxic nephritis, in contrast to the exacerbation observed with depletion at an early stage, indicating that their acquired proinflammatory phenotype adversely affected disease. These findings indicate that the intrarenal inflammatory microenvironment determines how kidney dendritic cells affect nephritis. In addition, proteinuria may harm the kidney by providing dendritic cells with more antigens to stimulate potentially pathogenic Th cells.

Effect of the absence of interleukin-12 on mesangial proliferative glomerulonephritis induced by habu snake venom

BACKGROUND

Interleukin-12 (IL12) participates in the pathophysiology of various experimental types of progressive glomerulonephritis, but its role in acute mesangial glomerulonephritis (AMG) induced by habu snake venom (HSV) has not been determined. This study aims to evaluate the effect of the absence of IL12 on AMG induced by HSV.

METHODS

AMG was induced in IL12 knockout (IL12-/-) and C57Bl/6 (IL12+/+) mice by a single i.v. administration of HSV. Vehicle was used in control animals. Mice were studied after 3, 7, and 14 days (D3, D7, and D14).

RESULTS

After treatment with HSV, IL12+/+ and -/- mice developed focal glomerular lesions, but groups of both lineages showed no statistical difference concerning albuminuria, serum creatinine, histopathology, number of cells by glomerular tuft, and glomerular tuft area. Compared to IL12+/+ mice, IL12-/- mice showed lower scores of glomerular desmin expression on D7 [1.55 (1.32; 1.65) vs. 1.12 (1.07; 1.22); p < 0.01] and D14 [1.60 (1.55; 1.75) vs. 1.20 (1.15; 1.20); p < 0.001], respectively, and lower scores of glomerular alpha-SMA expression on D14 [0.30 (0.21; 0.38) vs. 0.16 (0.26; 0.36); p < 0.001], respectively.

CONCLUSION

The absence of IL12 reduced the activity of mesangial cells, but did not modify the course of HSV-induced AMG in mice.

Serum immunoglobulin E can predict minimal change disease before renal biopsy

OBJECTIVES

Minimal change disease (MCD) is a major cause of nephrotic syndrome in both children and adults. The diagnosis of MCD in adults relies on findings of renal biopsy. Complications, although rare, may occur. This invasive procedure is also a suffering experience for some patients. Although Shu et al described the increase of serum immunoglobulin E (IgE) level in patients with MCD, whether IgE could be a predicting factor of MCD has not been determined.

METHODS

The sample was composed of 76 nonlupus patients with nephrotic range (>or=3.5 g/d/1.73 m) proteinuria and normal creatinine level who received renal biopsy since January 2006 to December 2007. Twenty-four demographic, clinical, and laboratory variables as predictors of MCD, including IgG, IgA, IgM, and IgE, were retrospectively gathered by chart review 1 day before renal biopsy.

RESULTS

The overall prevalence of MCD in this group (nonlupus and normal creatinine level) was 27.6% (21 of 76). The independent Student t test identified that 3 of 24 variables is statistically significant (P < 0.05). Serum IgE was found to have a good discriminative power (area under the receiver operating characteristic curve 0.868 +/- 0.053; P < 0.001) according to the area under the receiver operating characteristic curve.

CONCLUSIONS

Serum IgE exhibited high discriminative power in predicting MCD. Serum IgE is a straightforward and easily applied evaluative tool with good predictive abilities.

Poly(ADP-ribose) polymerase-1 regulates the progression of autoimmune nephritis in males by inducing necrotic cell death and modulating inflammation

Necrotic lesions and necrotic cell death characterize severe autoimmune nephritides, and contribute to local inflammation and to progression of the disease. Poly(ADP-ribose) polymerase-1 (PARP-1), a DNA repair enzyme, is involved in the induction of necrosis and is a key player in the acute and chronic inflammation. Therefore, we hypothesized that PARP-1 controls the severity of nephritis by mediating the induction of necrosis in the kidney. We used lupus and anti-glomerular basement membrane models of nephritis to determine the effects of PARP-1 on the inflammatory response in the kidney. We show in this study that PARP-1 is indeed activated during the course of glomerulonephritis. We also show that the absence of PARP-1 or its pharmacological inhibition results in milder nephritis, with lower blood urea nitrogen levels, reduced necrotic lesions, and higher survival rates. The relevance of PARP-1 showed a strong male sex specificity, and treatment of male mice with 17beta-estradiol prolonged their survival during the course of nephritis. PARP-1 also regulated TNF-alpha expression and up-regulation of adhesion molecules, further supporting a role of PARP-1 in the inflammatory process within the kidney. Our results demonstrate that PARP-1 activation and consequent necrotic cell death play an important role in the pathogenesis of male nephritis, and suggest that PARP-1 can be a novel therapeutic target in glomerulonephritis.

Invariant natural killer T cells and TGF-beta attenuate anti-GBM glomerulonephritis

Invariant natural killer T (iNKT) cells represent a particular subset of T lymphocytes capable of producing several cytokines, which exert regulatory or effector functions, following stimulation of the T cell receptor. In this study, we investigated the influence of iNKT cells on the development of experimental anti-glomerular basement membrane glomerulonephritis (anti-GBM GN). After injection of anti-GBM serum, the number of kidney iNKT cells rapidly increased. iNKT cell-deficient mice (Jalpha18-/-) injected with anti-GBM serum demonstrated worse renal function, increased proteinuria, and greater glomerular and tubular injury compared with similarly treated wild-type mice. We did not detect significant differences in Th1/Th2 polarization in renal tissue that might have explained the severity of disease in Jalpha18-/- mice. Interestingly, expression of both TGF-beta and TGF-beta-induced (TGFBI) mRNA was higher in wild-type kidneys compared with Jalpha18-/- kidneys, suggesting a possible protective role for TGF-beta in anti-GBM GN. Administration of an anti-TGF-beta neutralizing antibody significantly enhanced the severity of disease in wild-type, but not Jalpha18-/-, mice. In conclusion, in experimental anti-GBM GN, iNKT cells attenuate disease severity and TGF-beta has a renoprotective role.

Critical involvement of Th1-related cytokines in renal injuries induced by ischemia and reperfusion

Renal ischemia and reperfusion injury (IRI) is considered an inflammatory syndrome. To move forward in its pathogenesis, we exploited the role of several cytokines on renal damages triggered by IRI. Specifically to evaluate the role of Th1 immune profile in this system, IL-12, IFN-gamma, and IFN-gamma/IL-12 deficient (KO) mice on C57BL/6 background and their controls were subjected to IRI. In each group, blood and kidney samples were harvested. Renal function was evaluated by serum creatinine and renal morphometric analyses. Gene expression of IL-6 and HO-1 were also investigated by Q-PCR. IFN-gamma KO animals presented the highest impairment in renal function compared to controls. Conversely, IL-12 KO animals were absolutely protected and, in a lesser extent, IFN-gamma/IL-12 KO double knockout was also protected from IRI. Gene expression analyses showed higher expression of HO-1, a cytoprotective gene, and IL-6, a pro-inflammatory cytokine, in IFN-gamma deficient animals subjected to IRI. Our results confirm that Th1 related cytokines such as IL-12 and IFN-gamma are critically involved in renal ischemia and reperfusion injury.

Mammalian collagen IV

Four decades have passed since the first discovery of collagen IV by Kefalides in 1966. Since then collagen IV has been investigated extensively by a large number of research laboratories around the world. Advances in molecular genetics have resulted in identification of six evolutionary related mammalian genes encoding six different polypeptide chains of collagen IV. The genes are differentially expressed during the embryonic development, providing different tissues with specific collagen IV networks each having unique biochemical properties. Newly translated alpha-chains interact and assemble in the endoplasmic reticulum in a chain-specific fashion and form unique heterotrimers. Unlike most collagens, type IV collagen is an exclusive member of the basement membranes and through a complex inter- and intramolecular interactions form supramolecular networks that influence cell adhesion, migration, and differentiation. Collagen IV is directly involved in a number of genetic and acquired disease such as Alport's and Goodpasture's syndromes. Recent discoveries have also highlighted a new and direct role for collagen IV in the development of rare genetic diseases such as cerebral hemorrhage and porencephaly in infants and hemorrhagic stroke in adults. Years of intensive investigations have resulted in a vast body of information about the structure, function, and biology of collagen IV. In this review article, we will summarize essential findings on the structural and functional relationships of different collagen IV chains and their roles in health and disease.

Bovine Luteal Cells Stimulate Proliferation of Major Histocompatibility Nonrestricted Gamma Delta T Cells1

Luteal cells are potent activators of T cell proliferation in vitro. The purpose of this study was to determine which subset of T cells is stimulated by luteal cells and whether luteal cell-induced T cell activation elicits a proinflammatory or anti-inflammatory T cell response. The first objective was to determine if luteal cell-stimulated T cell proliferation was mediated by class I or II major histocompatibility complex (MHC) molecules. T cell proliferation was inhibited by anti-MHC class I but not anti-MHC class II antibodies. The second objective was to determine which T cell subtype proliferates when cultured with luteal cells. The proportions of CD4(+) and CD8(+) cells were unchanged, but the number of gamma delta T cells was increased by coculture with luteal cells. Immunohistochemistry confirmed the presence of gamma delta T cells in midcycle and regressing corpus luteum. The final objective was to characterize T cell cytokine production stimulated by luteal cells. The concentrations of interferon-gamma (IFNG) and interleukin 10 (IL10) were increased in luteal cell-T cell cocultures, whereas IL4 was undetectable, and IL12 was barely detectable in culture medium. It was concluded that coculture of luteal cells and T cells resulted in activation of a somewhat unique T cell subset, gamma delta T cells, as well as production of both pro- and anti-inflammatory cytokines. To our knowledge, this is the first report of gamma delta T cell activation by luteal parenchymal cells of any species, raising the possibility that tissue-resident gamma delta T cells are involved in regulating the balance between tissue homeostasis and luteolysis.

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

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

Genes expressed by both mesangial cells and bone marrow-derived cells underlie genetic susceptibility to crescentic glomerulonephritis in the rat

The Wistar-Kyoto (WKY) rat shows marked susceptibility to crescentic glomerulonephritis. In the model of nephrotoxic nephritis (NTN) that is induced by a small dose of nephrotoxic globulin, WKY rats developed crescents in 80 +/- 2% of glomeruli at day 10, whereas no crescents were seen in Lewis rats. This was associated with marked increase in monocyte chemoattractant protein-1 synthesis in WKY glomeruli. It was posited whether susceptibility depended on circulating cells or intrinsic renal cells. Bone marrow (BM) isografts from WKY to WKY or Lewis to Lewis did not affect susceptibility to NTN. When BM was transferred from WKY to Lewis rats, crescents developed in 35 +/- 9% of glomeruli 10 d after induction of NTN, indicating that susceptibility could be transferred by BM cells. However, crescents were also seen in WKY rats that were given Lewis marrow. For assessment of the contribution of intrinsic renal cells, kidneys from WKY or Lewis rats were transplanted into F1 animals. In NTN, the ratio of crescents in the transplanted kidney to the native kidney was significantly higher for WKY-to-F1 than for Lewis-to-F1 transplants, demonstrating that the kidney itself also influences susceptibility. Mesangial cell responses were then examined in the two strains. Mesangial cells that were derived from WKY rats synthesized significantly more monocyte chemoattractant protein-1 basally and after stimulation with heat-aggregated rabbit IgG or TNF-alpha. These results show that susceptibility to NTN in the WKY rat depends on both circulating and intrinsic renal cells and that there are genetic differences between the strains in mesangial responses to inflammatory stimuli.

Cytokines in Glomerulonephritis

Cytokines play central roles in both innate and adaptive immune responses that lead to renal inflammation. They are involved systemically in cross-talk between antigen-presenting cells, leukocytes, and regulatory cells to initiate and modulate nephritogenic immunity. Within the kidney, cytokines play a central role in signaling between infiltrating leukocytes and intrinsic renal cells and orchestrate the effector responses that lead to renal damage. Glomerulonephritis (GN) is an important cause of renal inflammation leading to renal failure that results from adaptive responses targeted at the kidney. Animal models of GN have shown that cytokines play critical roles in initiation and modulation of renal inflammatory responses through their ability to modulate the T helper 1/T helper 2 balance of nephritogenic immune responses. Evidence from clinical studies is now confirming the importance of this paradigm in directing the inflammatory mechanisms, histologic patterns, and clinical consequences of human GN. Cytokines also have critical intrarenal effector roles in the development, perpetuation, and resolution of GN. The proinflammatory role of intrarenal cytokine production by leukocytes in GN is well recognized, but, more recently, the role of intrinsic renal cell cytokine production in amplifying renal inflammation has been shown in animal models of GN. Studies showing benefits of specific anticytokine therapies directed at tumor necrosis factor in human GN are now appearing.

Glomérulonéphrites extracapillaires

Crescentic glomerulonephritis are characterised by a crescent shaped cellular proliferation that may lead to glomerular destruction. Over 50% of at least 10 analysed glomeruli should be affected. The search for immune deposits by immunofluorescence is an important diagnostic step. Patients present with rapidly progressive glomerulonephritis (RPGN): renal failure, proteinuria and haematuria. Extra-renal symptoms may help diagnosis. Diseases are classified in three groups according to immunofluorescence studies. Group I is characterised by linear deposits along the glomerular basement membrane (GBM) with anti-GBM auto-antibodies responsible for Goodpasture's disease. Group II put together various diseases with immune complex deposits. In group III, no significant immune deposits are found. Those "pauci-immune" glomerulonephritis are secondary to anti-neutrophil cytoplasmic antibodies (ANCA) positive systemic vasculitis, mainly Wegener's granulomatosis and microscopic polyangiitis. Primary glomerulonephritis may also be associated with crescent formation. Treatment is urgently required. Diagnosis is suspected in the context of extra-renal symptoms or immunological abnormalities, and confirmed by a kidney biopsy, that also helps to define prognosis. Apart from some group II glomerulonephritis, the induction treatment is often an association of steroids and cyclophosphamide, with plasma exchange in case of Goodpasture's disease. After remission, a maintenance treatment is required for ANCA-positive vasculitis to prevent relapses. The high rate of opportunistic infections and cancer give the rational for searching less aggressive therapeutic options.

T cells in crescentic glomerulonephritis

Crescent formation in glomerulonephritis (GN) is a manifestation of severe glomerular injury that usually results in a poor clinical outcome. In humans, crescentic GN is frequently associated with evidence of either systemic or organ-specific autoimmunity. T cells play a major role in initiation of adaptive immune responses that lead to crescentic injury. In experimental models of crescentic GN, Th1 predominant immune responses have been shown to promote crescent formation. Perturbation of regulatory T cell function may contribute to development of autoimmune crescentic GN. The presence of T cells and macrophages in crescentic glomeruli, frequently in the absence of humoral mediators of immunity, suggest a dominant effector role for T cells in crescentic GN. The association of cellular immune mediators with local fibrin deposition implicates cell-mediated "delayed-type hypersensitivity-like" mechanisms in crescent formation. Intrinsic renal cells also contribute to T cell-driven effector mechanisms in crescentic GN, via expression of MHC II and co-stimulatory molecules and by production of chemokines and cytokines that amplify leukocyte recruitment and injury.

Contributions of intrinsic renal cells to crescentic glomerulonephritis

The pro-inflammatory contributions of leukocytes, particularly macrophages and T cells, to the immunopathogenesis of proliferative forms of glomerulonephritis (GN) have been clearly established by various techniques, including in vivo depletion studies in experimental models. The evidence for an active pro-inflammatory role for intrinsic renal cells in GN has relied on studies demonstrating their production of pro-inflammatory mediators in vitro and during the development of GN. Until recently,the specific in vivo contributions of mediators from intrinsic renal cells to inflammatory injury in GN have proven difficult to define. Utilising 'chimeric' mice as a tool, several studies have explored the involvement of intrinsic renal cells via their production of cytokines and other key pro-inflammatory molecules. These studies provide evidence of important functional contributions of intrinsic renal cells to inflammatory injury in GN via their expression of cytokines, cytokine receptors, MHC-II and co-stimulatory molecules. They suggest a sequence of interactions between cytokines from leukocytes and intrinsic renal cells and important contributions of glomerular epithelial cell proliferation to crescent formation.

Hygiene hypothesis and prevalence of glomerulonephritis

The hygiene hypothesis was proposed to explain the marked increase in allergies that has been observed in industrialized (Westernized) societies. This hypothesis proposes that early and frequent exposure to bacterial and other antigens, such as is common in developing nations, leads to a normal Th1 response, but that better public hygiene and less infections observed in industrialized nations may lead to persistence of the Th2 phenotype and thereby increase our risk for developing allergies. Infection early in life with measles or hepatitis A virus, immunization with bacille Calmette-Guérin, certain gastrointestinal bacteria (lactobacillus), and environmental endotoxin exposure may protect individuals from developing allergy in adulthood. Paradoxically, infestation by parasites stimulates a Th2-cell response; however, the incidence of allergic disease is very low, perhaps due to the stimulation of T-regulatory lymphocytes that can downregulate Th1 and Th2 responses. Some types of human glomerulonephritis (GN) have Th1-predominant immune responses, including crescentic and membranoproliferative GN, whereas other types of GN have a predominant Th2 immune response, including membranous nephropathy, minimal change disease, and immunoglobulin A nephropathy. A review of the prevalence of specific GN shows that the higher prevalence of membranoproliferative GN in developing countries and the higher frequency of immunoglobulin A nephropathy and minimal change disease in industrialized countries could be explained by the hygiene hypothesis. We suggest that studies examining Th1/Th2 balance, particularly as it develops in childhood, should be performed to determine if early polarization of the immune response is responsible for the later development of specific forms of GN.

Granulocyte Macrophage Colony-Stimulating Factor Expression by Both Renal Parenchymal and Immune Cells Mediates Murine Crescentic Glomerulonephritis

GM-CSF has previously been demonstrated to be important in crescentic glomerulonephritis (GN). As both renal parenchymal cells and infiltrating inflammatory cells produce GM-CSF, their separate contributions to inflammatory renal injury were investigated by creation of two different types of GM-CSF chimeric mice: (1) GM-CSF-deficient (GM-CSF-/-)-->wild-type (WT) chimeras with leukocytes that are unable to produce GM-CSF and (2) WT-->GM-CSF-/- chimeras with deficient renal cell GM-CSF expression. Crescentic anti-glomerular basement membrane GN was induced in WT, GM-CSF(-/-)-->WT chimeras, WT-->GM-CSF-/- chimeras, and GM-CSF-/- mice by planting an antigen (sheep globulin) in their glomeruli. WT mice developed severe crescentic GN, whereas GM-CSF-/- were protected from development of disease. Glomerular T cell recruitment, CD40+ glomerular cells, and renal IFN-gamma and TNF expression were similar in both chimeras and WT mice but significantly reduced in GM-CSF-/- mice, indicating that either leukocyte or renal sources of GM-CSF are sufficient to drive these aspects of the inflammatory response. Restricted expression of GM-CSF revealed a major role for renal cell-derived GM-CSF but a minor role for leukocyte-derived GM-CSF in the formation of cellular crescents; glomerular MHC II expression; serum creatinine; and monocyte chemoattractant protein-1, vascular cellular adhesion molecule, and IL-1beta expression. Glomerular macrophage accumulation, proteinuria, and interstitial infiltrate were equivalent in both chimeric groups but intermediate between WT and GM-CSF-/-, indicating that both sources are required for the full development of glomerular injury in crescentic GN.

IL-12p40 and IL-18 in crescentic glomerulonephritis: IL-12p40 is the key Th1-defining cytokine chain, whereas IL-18 promotes local inflammation and leukocyte recruitment

Experimental crescentic glomerulonephritis (GN) is characterized by T helper 1 (Th1) directed nephritogenic immune responses and cell-mediated glomerular injury. IL-12p40, the common cytokine chain for both IL-12 and IL-23, is important in the generation and potentially the maintenance of Th1 responses, whereas IL-18 is a co-factor for Th1 responses that may have systemic and local proinflammatory effects. For testing the hypothesis that both endogenous IL-12p40 and endogenous IL-18 play pathogenetic roles in crescentic GN, accelerated anti-glomerular basement membrane GN was induced in mice genetically deficient in IL-12p40 (IL-12p40-/-), IL-18 (IL-18-/-), or both IL-12p40 and IL-18 (IL-12p40-/-IL-18-/-). Compared with wild-type C57BL/6 mice, IL-12p40-/- mice failed to make a nephritogenic Th1 response and developed markedly reduced crescent formation and renal leukocytic infiltration, despite renal production of chemoattractants and adhesion molecules. IL-18-/- mice developed an intact antigen-specific systemic Th1 response, a similar degree of crescent formation, but fewer glomeruli affected by other severe histologic changes and fewer leukocytes in glomeruli and interstitium. IL-18 was expressed within diseased kidneys. Local production of TNF, IL-1beta, IFN-gamma, CCL3 (MIP-1alpha), and CCL4 (MIP-1beta) was reduced in IL-18-/- mice, demonstrating a local proinflammatory role for IL-18. Combined deletion of IL-12p40 and IL-18 did not result in synergistic effects. Consistent with the hypothesis that inflammation leads to fibrosis, all three groups of deficient mice expressed lower levels of intrarenal TGF-beta1 and/or alpha1(I) procollagen mRNA. These studies demonstrate that in severe experimental crescentic GN, IL-12p40 is the key Th1-defining cytokine chain, whereas IL-18 has local proinflammatory roles.

Multiple facets of macrophages in renal injury

Macrophage infiltration is a common feature of renal disease and their presence has been synonymous with tissue damage and progressive renal failure. More recently work has focused on the heterogeneity of macrophage activation and in particular their ability to curtail inflammation and restore normal function. This has led to the view that it is macrophage function rather than their number that is important in determining the outcome of inflammatory disease. This review will focus on the pathways that regulate macrophage infiltration and activation and how these could be manipulated to control renal inflammatory disease. In particular, the ability of specific cell surface receptors and intracellular signaling pathways to control macrophage activation and how macrophages can be genetically manipulated to develop properties that favor resolution over ongoing injury.

An IL-12-independent role for CD40-CD154 in mediating effector responses: studies in cell-mediated glomerulonephritis and dermal delayed-type hypersensitivity

Crescentic glomerulonephritis (GN) results from IL-12-driven Th1-directed cell-mediated responses (akin to delayed-type hypersensitivity (DTH)) directed against glomerular Ags. CD40-CD154 interactions are critical for IL-12 production and Th1 polarization of immune responses. Crescentic anti-glomerular basement membrane GN was induced in C57BL/6 (wild-type (WT)) mice (sensitized to sheep globulin) by planting this Ag (as sheep anti-mouse glomerular basement membrane globulin) in their glomeruli. Crescentic GN did not develop in CD40(-/-) mice due to significantly reduced nephritogenic Th1 responses. IL-12 was administered to CD40(-/-) mice with GN to dissect interactions between IL-12 and CD40 in inducing nephritogenic immunity and injury. Administration of IL-12 to CD40(-/-) mice restored Th cell IFN-gamma production, and up-regulated intrarenal chemokines and glomerular T cell and macrophage accumulation compared with WT control mice. Despite this, renal macrophages were not activated and renal injury and dermal DTH were not restored. Thus, CD40-directed IL-12 drives Th1 generation and effector cell recruitment but CD40 is required for activation. To test this hypothesis, activated OT-II OVA-specific CD4(+) cells and OVA(323-339)-loaded nonresponsive APCs were transferred into footpads of WT, CD40(-/-), and macrophage-depleted WT mice. WT mice developed significant DTH compared with CD40(-/-) and macrophage-depleted WT mice. This study demonstrated that CD40-induced IL-12 is required for generation of systemic Th1 immunity to nephritogenic Ags, and that IL-12 enhances Th1 effector cell recruitment to peripheral sites of Ag presentation via generation of local chemokines. Effector cell activation, renal DTH-like injury, and dermal DTH require direct Th1 CD154/macrophage CD40 interactions.

Leukocyte-derived interleukin-1beta interacts with renal interleukin-1 receptor I to promote renal tumor necrosis factor and glomerular injury in murine crescentic glomerulonephritis

The involvement of proinflammatory cytokines interleukin (IL)-1 and tumor necrosis factor (TNF) in crescentic glomerulonephritis (GN) is well established. Recently the requirement of intrinsic renal cell participation via their production of TNF in crescentic GN was demonstrated. The current studies address the relative contributions of leukocyte and intrinsic renal cell-derived IL-1beta in the induction of TNF production and glomerular injury by studying bone marrow chimeric mice. Leukocyte-derived IL-1beta was critical in the development of crescentic renal injury because IL-1beta(-/-)-->WT (absent leukocyte IL-1beta) chimeric mice had significantly attenuated TNF expression and were protected from the development of crescentic GN. In contrast, WT-->IL-1beta(-/-) chimeric mice (intact leukocyte but absent renal IL-1beta) developed similar TNF expression and crescentic GN to wild-type mice. To determine the cellular target for IL-1 in this model, IL-RI chimeric mice were studied. IL-1RI(-/-)-->WT chimeric (absent leukocyte IL-1RI expression) mice showed no attenuation of crescentic GN, whereas in the absence of renal IL-1RI (WT-->IL-1RI(-/-) chimeras), glomerular TNF expression and the development of crescentic GN were significantly decreased. These studies demonstrate that leukocytes are the major cellular source of IL-1beta, and that IL-1beta acts principally via the IL-1RI on intrinsic renal cells to induce TNF expression and crescentic glomerular injury.

Effect of anemia and renal cytokine production on erythropoietin production during blood-stage malaria

BACKGROUND

Renal dysfunction and severe anemia are clinical complications of blood-stage malaria. Erythropoietin (Epo) is a hormone produced by the kidney and plays an essential role in stimulating erythrocyte production. Renal dysfunction in malaria is associated with changes in renal cytokine levels, which may affect the production of Epo and the alleviation of anemia.

METHODS

Resistant C57BL/6 (B6) and susceptible A/J mice were infected with Plasmodium chabaudi AS. The levels of Epo and cytokines were measured by enzyme-linked immunosorbent assay (ELISA) and the degree of anemia was determined by hematocrit. Regression analyses were employed to estimate the influences of anemia and renal cytokines on the production of Epo during infection.

RESULTS

A/J mice developed higher peak parasitemia, more severe anemia, and succumbed as compared to B6 mice, which survived the infection. B6 mice had higher levels of renal tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-10, whereas A/J mice had higher levels of IL-12p70, granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-4, and Epo. Regression analyses revealed that kidney Epo levels were influenced most strongly by changes in hematocrit levels. In addition, albeit to a much weaker degree, kidney Epo levels correlated negatively with GM-CSF levels but positively with IL-10 levels.

CONCLUSION

Blood-stage malaria infection modulates the production of renal pro- and anti-inflammatory cytokines in resistant versus susceptible strains of mice differentially. However, despite the fluctuations of renal cytokines, the degree of anemia is the main determinant for Epo production during blood-stage malaria while kidney cytokines may exert secondary influences.

Intrinsic renal cell expression of CD40 directs Th1 effectors inducing experimental crescentic glomerulonephritis

Evidence suggests that human and experimental crescentic GN results from Th1-predominant immunity to glomerular antigens. CD40/CD154 signaling plays a key role in initiating Th1 responses and may direct Th1 effector responses. The role of CD40 in the development of GN was assessed in murine experimental anti-glomerular basement membrane GN. In this model, C57BL/6 wild-type (WT) mice sensitized to sheep globulin develop crescentic GN resulting from Th1 effector responses when challenged with sheep globulin planted in glomeruli. CD40-/- mice do not develop immunity in response to sheep globulin and thus fail to develop effector responses or significant GN. CD40 is expressed in nephritic glomeruli, suggesting a potential role for intrarenal CD40-CD154 interactions in injurious effector responses. Immune neutralization of the CD40 ligand (CD154) at the time of challenge significantly reduced accumulation of Th1 effectors and injury. The role of CD40 expression by renal cells was assessed by comparing GN in WT-->CD40-/- chimeras (absent renal but intact bone marrow CD40) and sham chimeric mice (WT-->WT). Both groups developed strong antigen-specific immune responses (antibody and IFN-gamma production). However, WT-->CD40-/- chimeras demonstrated reduced renal monocyte chemotactic protein 1 and IFN-inducible protein 10 mRNA levels and minimal T cell and macrophage influx and were protected from renal injury. Sham chimeric mice developed reduced GFR, with prominent renal expression of monocyte chemotactic protein 1 and IFN-inducible protein 10 mRNA and effector cell accumulation. In conclusion, the expression of CD40 by nonimmune renal cells plays a major role in Th1 effector responses by inducing Th1 chemokine production. Therefore, CD40-CD154 interactions are a potential therapeutic target in GN.

Bone morphogenic protein-7 inhibits progression of chronic renal fibrosis associated with two genetic mouse models

Tubulointerstitial fibrosis is a hallmark feature of chronic renal injury. Specific therapies to control the progression of renal fibrosis toward end-stage renal failure are limited. Previous studies have demonstrated that expression of endogenous bone morphogenic protein-7 (BMP-7) is reduced in the kidneys of several inducible mouse models of acute and chronic renal disease and that administration of exogenous recombinant human BMP-7 (rhBMP-7) has a beneficial effect on kidney function. Here we report that treatment with rhBMP-7 leads to improved renal function, histology, and survival in mice deficient in the alpha3-chain of type IV collagen and MRL/MpJlpr/lpr lupus mice, two genetic models for chronic renal injury and fibrosis. Such therapeutic benefit is also associated with a significant decrease in the expression of profibrotic molecules, such as type I collagen and fibronectin, in renal fibroblasts. Additionally, rhBMP-7 induces expression of active matrix metalloproteinase-2, which is potentially important for removal of fibrotic matrix. Collectively, these studies provide further evidence for rhBMP-7 as an important bone-associated protein with protective function against renal pathology.

Overlapping roles of endothelial selectins and vascular cell adhesion molecule-1 in immune complex-induced leukocyte recruitment in the cremasteric microvasculature

Many adhesion molecule pathways have been invoked as mediating leukocyte recruitment during immune complex-induced inflammation. However the individual roles of these molecules have not been identified via direct visualization of an affected microvasculature. Therefore, to identify the specific adhesion molecules responsible for leukocyte rolling and adhesion in immune complex-dependent inflammation we used intravital microscopy to examine postcapillary venules in the mouse cremaster muscle. Wild-type mice underwent an intrascrotal reverse-passive Arthus model of immune complex-dependent inflammation and subsequently, leukocyte-endothelial cell interactions and P- and E-selectin expression were assessed in cremasteric postcapillary venules. At 4 hours, the reverse-passive Arthus response induced a significant reduction in leukocyte rolling velocity and significant increases in adhesion and emigration. P-selectin expression was increased above constitutive levels whereas E-selectin showed a transient induction of expression peaking between 2.5 to 4 hours and declining thereafter. While E-selectin was expressed, rolling could only be eliminated by combined blockade of P- and E-selectin. However, by 8 hours, all rolling was P-selectin-dependent. In contrast, inhibition of vascular cell adhesion molecule-1 had a minimal effect on leukocyte rolling, but significantly reduced both adhesion and emigration. These observations demonstrate that immune complex-mediated leukocyte recruitment in the cremaster muscle involves overlapping roles for the endothelial selectins and vascular cell adhesion molecule-1.

Intrinsic renal cells are the major source of tumor necrosis factor contributing to renal injury in murine crescentic glomerulonephritis

Macrophages are prominent participants in crescentic glomerulonephritis (GN) and have been suggested to be the major source of TNF in this cell-mediated form of glomerular inflammation. Intrinsic renal cells also have the capacity to produce TNF. For dissecting the contribution of local versus bone marrow (BM)-derived TNF in inflammatory renal injury, TNF chimeric mice were created by transplanting normal wild-type (WT) BM into irradiated TNF-deficient recipients (WT-->TNF-/- chimeras) and vice versa (TNF-/- -->WT chimeras). A model of crescentic GN induced by an intravenous injection of sheep anti-murine glomerular basement membrane antibody was studied in WT mice, mice with complete TNF deficiency (TNF-/-), and chimeric mice. Crescentic GN was attenuated in TNF-/- mice with fewer crescents (crescents, 13.7 +/- 1.7% of glomeruli) and reduced functional indices of renal injury (serum creatinine, 15.2 +/- 0.8 micromol/L). Similar protection (crescents, 14.3 +/- 1.9% of glomeruli; serum creatinine, 18.9 +/- 1.1 micromol/L) was observed in chimeric mice with intact BM but absent renal-derived TNF (WT-->TNF-/- chimeras), suggesting a minor contribution of infiltrating leukocytes to TNF-mediated renal injury. Chimeric mice with TNF-deficient leukocytes but intact intrinsic renal cell-derived TNF (crescents, 20.5 +/- 2.0% of glomeruli; serum creatinine, 21.6 +/- 1.4 micromol/L) developed similar crescentic GN to WT mice (crescents, 22.3 +/- 1.4% of glomeruli; serum creatinine, 24.8 +/- 1.9 micromol/L). Cutaneous delayed-type hypersensitivity after subdermal challenge with the nephritogenic antigen was attenuated in the absence of BM cell-derived TNF but unaffected in WT-->TNF-/- chimeric mice. These studies suggest that intrinsic renal cells are the major cellular source of TNF contributing to inflammatory injury in crescentic GN.

IFN-gamma production by intrinsic renal cells and bone marrow-derived cells is required for full expression of crescentic glomerulonephritis in mice

The contribution of IFN-gamma from bone marrow (BM) and non-BM-derived cells to glomerular and cutaneous delayed-type hypersensitivity (DTH) was studied in mice. Chimeric IFN-gamma mice (IFN-gamma(+/+) BM chimera), in which IFN-gamma production was restricted to BM-derived cells, were created by transplanting normal C57BL/6 (wild-type (WT)) BM into irradiated IFN-gamma-deficient mice. BM IFN-gamma-deficient chimeric mice (IFN-gamma(-/-) BM chimera) were created by transplanting WT mice with IFN-gamma-deficient BM. WT and sham chimeric mice (WT mice transplanted with WT BM) developed crescentic glomerulonephritis (GN) with features of DTH (including glomerular T cell and macrophage infiltration) in response to an Ag planted in their glomeruli and skin DTH following subdermal Ag challenge. IFN-gamma-deficient mice showed significant protection from crescentic GN and reduced cutaneous DTH. IFN-gamma(+/+) BM chimeric and IFN-gamma(-/-) BM chimeric mice showed similar attenuation of crescentic GN as IFN-gamma-deficient mice, whereas cutaneous DTH was reduced only in IFN-gamma(-/-) BM chimeras. In crescentic GN, IFN-gamma was expressed by tubular cells and occasional glomerular cells and was colocalized with infiltrating CD8(+) T cells, but not with CD4(+) T cells or macrophages. Renal MHC class II expression was reduced in IFN-gamma(+/+) BM chimeric mice and was more severely reduced in IFN-gamma-deficient mice and IFN-gamma(-/-) BM chimeric mice. These studies show that IFN-gamma expression by both BM-derived cells and intrinsic renal cells is required for the development of crescentic GN, but IFN-gamma production by resident cells is not essential for the development of cutaneous DTH.

Increased expression of cell adhesion kinase beta in human and rat crescentic glomerulonephritis

Cell adhesion kinase beta (CAKbeta, also known as Pyk2/CadTK/RAFTK) is the second member of the focal adhesion kinase (FAK) subfamily. We examined the expression of CAKbeta in various human glomerulopathies by immunohistochemistry. Although CAKbeta expression in the normal kidney is confined to the brush border of the proximal tubule with no detectable glomerular staining, we found that glomerular crescents strongly expressed this kinase. Expression of CAKbeta was prominent in cellular crescents but was minimal in fibrocellular or fibrous crescents. Serial section analysis revealed that most CAKbeta-expressing cells were positive for cytokeratin but were negative for CD68 (a macrophage marker), suggesting that CAKbeta was expressed by parietal epithelium in the crescents. We also examined CAKbeta expression in a rat model of crescentic glomerulonephritis induced by anti-glomerular basement membrane antibody. Similar to human nephritis, enhanced expression of CAKbeta in glomerular crescents was apparent. Increased expression of CAKbeta also was confirmed by anti-CAKbeta immunoblotting and by real-time quantitative polymerase chain reaction. Previous studies have shown that CAKbeta is activated by various stimuli regulating cell growth and survival. Although our findings do not determine whether or not increased expression of CAKbeta is a primary event for the development of crescentic glomerulonephritis, further understanding of this pathway may be important to gain novel insights into the factors that promote crescent formation.