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Significance Statement: Treatment of acute, crescentic glomerulonephritis (GN) consists of unspecific and potentially toxic immunosuppression. T cells are central in the pathogenesis of GN, and various checkpoint molecules control their activation. The immune checkpoint molecule B and T-lymphocyte attenuator (BTLA) has shown potential for restraining inflammation in other T-cell-mediated disease models. To investigate its role in GN in a murine model of crescentic nephritis, the authors induced nephrotoxic nephritis in BTLA-deficient mice and wild-type mice. They found that BTLA has a renoprotective role through suppression of local Th1-driven inflammation and expansion of T regulatory cells and that administration of an agonistic anti-BTLA antibody attenuated experimental GN. These findings suggest that antibody-based modulation of BTLA may represent a treatment strategy in human glomerular disease., Background: Modulating T-lymphocytes represents a promising targeted therapeutic option for glomerulonephritis (GN) because these cells mediate damage in various experimental and human GN types. The immune checkpoint molecule B and T-lymphocyte attenuator (BTLA) has shown its potential to restrain inflammation in other T-cell-mediated disease models. Its role in GN, however, has not been investigated., Methods: We induced nephrotoxic nephritis (NTN), a mouse model of crescentic GN, in Btla -deficient ( BtlaKO ) mice and wild-type littermate controls and assessed disease severity using functional and histologic parameters at different time points after disease induction. Immunologic changes were comprehensively evaluated by flow cytometry, RNA sequencing, and in vitro assays for dendritic cell and T-cell function. Transfer experiments into Rag1KO mice confirmed the observed in vitro findings. In addition, we evaluated the potential of an agonistic anti-BTLA antibody to treat NTN in vivo ., Results: The BtlaKO mice developed aggravated NTN, driven by an increase of infiltrating renal Th1 cells. Single-cell RNA sequencing showed increased renal T-cell activation and positive regulation of the immune response. Although BTLA-deficient regulatory T cells (Tregs) exhibited preserved suppressive function in vitro and in vivo , BtlaKO T effector cells evaded Treg suppression. Administration of an agonistic anti-BTLA antibody robustly attenuated NTN by suppressing nephritogenic T effector cells and promoting Treg expansion., Conclusions: In a model of crescentic GN, BTLA signaling effectively restrained nephritogenic Th1 cells and promoted regulatory T cells. Suppression of T-cell-mediated inflammation by BTLA stimulation may prove relevant for a broad range of conditions involving acute GN., (Copyright © 2023 by the American Society of Nephrology.)

Background: Renal denervation (RDN) is an invasive intervention to treat drug-resistant arterial hypertension. Its therapeutic value is contentious. Here we examined the effects of RDN on inflammatory and infectious kidney disease models in mice., Methods: Mice were unilaterally or bilaterally denervated, or sham operated, then three disease models were induced: nephrotoxic nephritis (NTN, a model for crescentic GN), pyelonephritis, and acute endotoxemic kidney injury (as a model for septic kidney injury). Analytical methods included measurement of renal glomerular filtration, proteinuria, flow cytometry of renal immune cells, immunofluorescence microscopy, and three-dimensional imaging of optically cleared kidney tissue by light-sheet fluorescence microscopy followed by algorithmic analysis., Results: Unilateral RDN increased glomerular filtration in denervated kidneys, but decreased it in the contralateral kidneys. In the NTN model, more nephritogenic antibodies were deposited in glomeruli of denervated kidneys, resulting in stronger inflammation and injury in denervated compared with contralateral nondenervated kidneys. Also, intravenously injected LPS increased neutrophil influx and inflammation in the denervated kidneys, both after unilateral and bilateral RDN. When we induced pyelonephritis in bilaterally denervated mice, both kidneys contained less bacteria and neutrophils. In unilaterally denervated mice, pyelonephritis was attenuated and intrarenal neutrophil numbers were lower in the denervated kidneys. The nondenervated contralateral kidneys harbored more bacteria, even compared with sham-operated mice, and showed the strongest influx of neutrophils., Conclusions: Our data suggest that the increased perfusion and filtration in denervated kidneys can profoundly influence concomitant inflammatory diseases. Renal deposition of circulating nephritic material is higher, and hence antibody- and endotoxin-induced kidney injury was aggravated in mice. Pyelonephritis was attenuated in denervated murine kidneys, because the higher glomerular filtration facilitated better flushing of bacteria with the urine, at the expense of contralateral, nondenervated kidneys after unilateral denervation., (Copyright © 2021 by the American Society of Nephrology.)

Dendritic cells (DCs) are thought to form a dendritic network across barrier surfaces and throughout organs, including the kidney, to perform an important sentinel function. However, previous studies of DC function used markers, such as CD11c or CX3CR1, that are not unique to DCs. Here, we evaluated the role of DCs in renal inflammation using a CD11c reporter mouse line and two mouse lines with DC-specific reporters, Zbtb46 -GFP and Snx22 -GFP. Multiphoton microscopy of kidney sections confirmed that most of the dendritically shaped CD11c + cells forming a network throughout the renal interstitium expressed macrophage-specific markers. In contrast, DCs marked by Zbtb46 -GFP or Snx22 -GFP were less abundant, concentrated around blood vessels, and round in shape. We confirmed this pattern of localization using imaging mass cytometry. Motility measurements showed that resident macrophages were sessile, whereas DCs were motile before and after inflammation. Although uninflamed glomeruli rarely contained DCs, injury with nephrotoxic antibodies resulted in accumulation of ZBTB46 + cells in the periglomerular region. ZBTB46 identifies all classic DCs, which can be categorized into two functional subsets that express either CD103 or CD11b. Depletion of ZBTB46 + cells attenuated the antibody-induced kidney injury, whereas deficiency of the CD103 + subset accelerated injury through a mechanism that involved increased neutrophil infiltration. RNA sequencing 7 days after nephrotoxic antibody injection showed that CD11b + DCs expressed the neutrophil-attracting cytokine CXCL2, whereas CD103 + DCs expressed high levels of several anti-inflammatory genes. These results provide new insights into the distinct functions of the two major DC subsets in glomerular inflammation., (Copyright © 2018 by the American Society of Nephrology.)

The total number of glomeruli is a fundamental parameter of kidney function but very difficult to determine using standard methodology. Here, we counted all individual glomeruli in murine kidneys and sized the capillary tufts by combining in vivo fluorescence labeling of endothelial cells, a novel tissue-clearing technique, lightsheet microscopy, and automated registration by image analysis. Total hands-on time per organ was <1 hour, and automated counting/sizing was finished in <3 hours. We also investigated the novel use of ethyl-3-phenylprop-2-enoate (ethyl cinnamate) as a nontoxic solvent-based clearing reagent that can be handled without specific safety measures. Ethyl cinnamate rapidly cleared all tested organs, including calcified bone, but the fluorescence of proteins and immunohistochemical labels was maintained over weeks. Using ethyl cinnamate-cleared kidneys, we also quantified the average creatinine clearance rate per glomerulus. This parameter decreased in the first week of experimental nephrotoxic nephritis, whereas reduction in glomerular numbers occurred much later. Our approach delivers fundamental parameters of renal function, and because of its ease of use and speed, it is suitable for high-throughput analysis and could greatly facilitate studies of the effect of kidney diseases on whole-organ physiology., (Copyright © 2017 by the American Society of Nephrology.)

Kidney dendritic cells (DCs) regulate nephritogenic T cell responses. Most kidney DCs belong to the CD11b + subset and promote crescentic GN (cGN). The function of the CD103 + subset, which represents <5% of kidney DCs, is poorly understood. We studied the role of CD103 + DCs in cGN using several lines of genetically modified mice that allowed us to reduce the number of these cells. In all lines, we detected a reduction of FoxP3 + intrarenal regulatory T cells (T regs ), which protect against cGN. Mice lacking the transcription factor Batf3 had a more profound reduction of CD103 + DCs and T regs than did the other lines used, and showed the most profound aggravation of cGN. The conditional reduction of CD103 + DC numbers by 50% in Langerin-DTR mice halved T reg numbers, which did not suffice to significantly aggravate cGN. Mice lacking the cytokine Flt3L had fewer CD103 + DCs and T regs than Langerin-DTR mice but exhibited milder cGN than did Batf3 -/- mice presumably because proinflammatory CD11b + DCs were somewhat depleted as well. Conversely, Flt3L supplementation increased the number of CD103 + DCs and T regs , but also of proinflammatory CD11b + DCs. On antibody-mediated removal of CD11b + DCs, Flt3L supplementation ameliorated cGN. Mechanistically, CD103 + DCs caused cocultured T cells to differentiate into T regs and produced the chemokine CCL20, which is known to attract T regs into the kidney. Our findings show that CD103 + DCs foster intrarenal FoxP3 + T reg accumulation, thereby antagonizing proinflammatory CD11b + DCs. Thus, increasing CD103 + DC numbers or functionality might be advantageous in cGN., (Copyright © 2016 by the American Society of Nephrology.)

The NFκB transcription factor family facilitates the activation of dendritic cells (DCs) and CD4(+) T helper (Th) cells, which are important for protective adaptive immunity. Inappropriate activation of these immune cells may cause inflammatory disease, and NFκB inhibitors are promising anti-inflammatory drug candidates. Here, we investigated whether inhibiting the NFκB-inducing kinase IKK2 can attenuate crescentic GN, a severe DC- and Th cell-dependent kidney inflammatory disease. Prophylactic pharmacologic IKK2 inhibition reduced DC and Th cell activation and ameliorated nephrotoxic serum-induced GN in mice. However, therapeutic IKK2 inhibition during ongoing disease aggravated the nephritogenic immune response and disease symptoms. This effect resulted from the renal loss of regulatory T cells, which have been shown to protect against crescentic GN and which require IKK2. In conclusion, although IKK2 inhibition can suppress the induction of nephritogenic immune responses in vivo, it may aggravate such responses in clinically relevant situations, because it also impairs regulatory T cells and thereby, unleashes preexisting nephritogenic responses. Our findings argue against using IKK2 inhibitors in chronic GN and perhaps, other immune-mediated diseases., (Copyright © 2016 by the American Society of Nephrology.)

Pathologic proliferation of mesangial and parietal epithelial cells (PECs) is a hallmark of various glomerulonephritides. Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine that mediates inflammation by engagement of a receptor complex involving the components CD74, CD44, CXCR2, and CXCR4. The proliferative effects of MIF may involve CD74 together with the coreceptor and PEC activation marker CD44. Herein, we analyzed the effects of local glomerular MIF/CD74/CD44 signaling in proliferative glomerulonephritides. MIF, CD74, and CD44 were upregulated in the glomeruli of patients and mice with proliferative glomerulonephritides. During disease, CD74 and CD44 were expressed de novo in PECs and colocalized in both PECs and mesangial cells. Stress stimuli induced MIF secretion from glomerular cells in vitro and in vivo, in particular from podocytes, and MIF stimulation induced proliferation of PECs and mesangial cells via CD74. In murine crescentic GN, Mif-deficient mice were almost completely protected from glomerular injury, the development of cellular crescents, and the activation and proliferation of PECs and mesangial cells, whereas wild-type mice were not. Bone marrow reconstitution studies showed that deficiency of both nonmyeloid and bone marrow-derived Mif reduced glomerular cell proliferation and injury. In contrast to wild-type mice, Cd74-deficient mice also were protected from glomerular injury and ensuing activation and proliferation of PECs and mesangial cells. Our data suggest a novel molecular mechanism and glomerular cell crosstalk by which local upregulation of MIF and its receptor complex CD74/CD44 mediate glomerular injury and pathologic proliferation in GN., (Copyright © 2016 by the American Society of Nephrology.)

Traditionally, arterial hypertension and subsequent end-organ damage have been attributed to hemodynamic factors, but increasing evidence indicates that inflammation also contributes to the deleterious consequences of this disease. The immune system has evolved to prevent invasion of foreign organisms and to promote tissue healing after injury. However, this beneficial activity comes at a cost of collateral damage when the immune system overreacts to internal injury, such as prehypertension. Renal inflammation results in injury and impaired urinary sodium excretion, and vascular inflammation leads to endothelial dysfunction, increased vascular resistance, and arterial remodeling and stiffening. Notably, modulation of the immune response can reduce the severity of BP elevation and hypertensive end-organ damage in several animal models. Indeed, recent studies have improved our understanding of how the immune response affects the pathogenesis of arterial hypertension, but the remarkable advances in basic immunology made during the last few years still await translation to the field of hypertension. This review briefly summarizes recent advances in immunity and hypertension as well as hypertensive end-organ damage., (Copyright © 2016 by the American Society of Nephrology.)

Neutrophil trafficking to sites of inflammation is essential for the defense against bacterial and fungal infections, but also contributes to tissue damage in TH17-mediated autoimmunity. This process is regulated by chemokines, which often show an overlapping expression pattern and function in pathogen- and autoimmune-induced inflammatory reactions. Using a murine model of crescentic GN, we show that the pathogenic TH17/IL-17 immune response induces chemokine (C-X-C motif) ligand 5 (CXCL5) expression in kidney tubular cells, which recruits destructive neutrophils that contribute to renal tissue injury. By contrast, CXCL5 was dispensable for neutrophil recruitment and effective bacterial clearance in a murine model of acute bacterial pyelonephritis. In line with these findings, CXCL5 expression was highly upregulated in the kidneys of patients with ANCA-associated crescentic GN as opposed to patients with acute bacterial pyelonephritis. Our data therefore identify CXCL5 as a potential therapeutic target for the restriction of pathogenic neutrophil infiltration in TH17-mediated autoimmune diseases while leaving intact the neutrophil function in protective immunity against invading pathogens., (Copyright © 2015 by the American Society of Nephrology.)

Podocytes are essential to the structure and function of the glomerular filtration barrier; however, they also exhibit increased expression of MHC class II molecules under inflammatory conditions, and they remove Ig and immune complexes from the glomerular basement membrane (GBM). This finding suggests that podocytes may act as antigen-presenting cells, taking up and processing antigens to initiate specific T cell responses, similar to professional hematopoietic cells such as dendritic cells or macrophages. Here, MHC-antigen complexes expressed exclusively on podocytes of transgenic mice were sufficient to activate CD8+ T cells in vivo. In addition, deleting MHC class II exclusively on podocytes prevented the induction of experimental anti-GBM nephritis. Podocytes ingested soluble and particulate antigens, activated CD4+ T cells, and crosspresented exogenous antigen on MHC class I molecules to CD8+ T cells. In conclusion, podocytes participate in the antigen-specific activation of adaptive immune responses, providing a potential target for immunotherapies of inflammatory kidney diseases and transplant rejection.

Although the spleen is a major site where immune tolerance to circulating innocuous antigens occurs, the kidney also contributes. Circulating antigens smaller than albumin are constitutively filtered and concentrated in the kidney and reach the renal lymph node by lymphatic drainage, where resident dendritic cells (DCs) capture them and induce tolerance of specific cytotoxic T cells through unknown mechanisms. Here, we found that the coinhibitory cell surface receptor programmed death 1 (PD-1) on cytotoxic T cells mediates to their tolerance. Renal lymph node DCs of the CD8(+) XCR1(+) subset, which depend on the transcription factor Batf3, expressed the PD-1 cognate ligand PD-L1. Batf3-dependent DCs in the renal lymph node presented antigen that had been concentrated in the kidney and used PD-L1 to induce apoptosis of cytotoxic T cells. In contrast, T cell tolerance in the spleen was independent of PD-1, PD-L1, and Batf3. In summary, these results clarify how the kidney/renal lymph node system tolerizes the immune system against circulating innocuous antigens.

Immature renal dendritic cells (DCs) are protective early in murine crescentic GN, but the mechanisms underlying this protection are unknown. Here, depletion of DCs reduced the recruitment of invariant natural killer T (iNKT) cells, which attenuate GN, into the kidney in the early stage of experimental crescentic GN. More than 90% of renal iNKT cells expressed the chemokine receptor CXCR6, and renal DCs produced high amounts of the cognate ligand CXCL16 early after induction of nephritis, suggesting that renal DC-derived CXCL16 might attract protective CXCR6(+) iNKT cells. Consistent with this finding, CXCR6-deficient mice exhibited less iNKT cell recruitment and developed nephritis that was more severe, similar to the aggravated nephritis observed in mice depleted of immature DCs. Finally, adoptive transfer of CXCR6-competent NKT cells ameliorated nephritis. Taken together, these results suggest an immunoprotective mechanism involving immature DCs, CXCL16, CXCR6, and regulatory iNKT cells, which might stimulate the development of new therapeutic strategies for GN.

The Th17 immune response appears to contribute to the pathogenesis of human and experimental crescentic GN, but the cell types that produce IL-17A in the kidney, the mechanisms involved in its induction, and the IL-17A-mediated effector functions that promote renal tissue injury are incompletely understood. Here, using a murine model of crescentic GN, we found that CD4(+) T cells, γδ T cells, and a population of CD3(+)CD4(-)CD8(-)γδT cell receptor(-)NK1.1(-) T cells all produce IL-17A in the kidney. A time course analysis identified γδ T cells as a major source of IL-17A in the early phase of disease, before the first CD4(+) Th17 cells arrived. The production of IL-17A by renal γδ T cells depended on IL-23p19 signaling and retinoic acid-related orphan receptor-γt but not on IL-1β or IL-6. In addition, depletion of dendritic cells, which produce IL-23 in the kidney, reduced IL-17A production by renal γδ T cells. Furthermore, the lack of IL-17A production in γδ T cells, as well as the absence of all γδ T cells, reduced neutrophil recruitment into the kidney and ameliorated renal injury. Taken together, these data suggest that γδ T cells produce IL-17A in the kidney, induced by IL-23, promoting neutrophil recruitment, and contributing to the immunopathogenesis of crescentic GN.

Parietal epithelial cells (PECs) of the renal glomerulus contribute to the formation of both cellular crescents in rapidly progressive GN and sclerotic lesions in FSGS. Subtotal transgenic ablation of podocytes induces FSGS but the effect of specific ablation of PECs is unknown. Here, we established an inducible transgenic mouse to allow subtotal ablation of PECs. Proteinuria developed during doxycycline-induced cellular ablation but fully reversed 26 days after termination of doxycycline administration. The ablation of PECs was focal, with only 30% of glomeruli exhibiting histologic changes; however, the number of PECs was reduced up to 90% within affected glomeruli. Ultrastructural analysis revealed disruption of PEC plasma membranes with cytoplasm shedding into Bowman's space. Podocytes showed focal foot process effacement, which was the most likely cause for transient proteinuria. After >9 days of cellular ablation, the remaining PECs formed cellular extensions to cover the denuded Bowman's capsule and expressed the activation marker CD44 de novo. The induced proliferation of PECs persisted throughout the observation period, resulting in the formation of typical cellular crescents with periglomerular infiltrate, albeit without accompanying proteinuria. In summary, subtotal ablation of PECs leads the remaining PECs to react with cellular activation and proliferation, which ultimately forms cellular crescents.

The renal mononuclear phagocytic system, conventionally composed of macrophages (Mø) and dendritic cells (DCs), plays a central role in health and disease of the kidney. Overlapping definitions of renal DCs and Mø, stemming from historically separate research tracks and the lack of experimental tools to specifically study the roles of these cells in vivo, have generated confusion and controversy, however, regarding their immunologic function in the kidney. This brief review provides an appraisal of the current state of knowledge of the renal mononuclear phagocytic system interpreted from the perspective of immunologic function. Physical characteristics, ontogeny, and known functions of the main subsets of renal mononuclear phagocytes as they relate to homeostasis, surveillance against injury and infection, and immune-mediated inflammatory injury and repair within the kidney are described. Gaps and inconsistencies in current knowledge are used to create a roadmap of key questions to be answered in future research.

Dendritic cells (DCs) are the most abundant immune cells in the kidney and form an intricate network in the tubulointerstitium, suggesting that they may play an important role in interstitial infections such as pyelonephritis. Here, we optimized a murine pyelonephritis model by instilling uropathogenic Escherichia coli two times at a 3-hour interval, which produced an infection rate of 84%. By 3 hours after the second instillation, resident kidney DCs began secreting the chemokine CXCL2, which recruits neutrophilic granulocytes. During the time studied, DCs remained responsible for most of the CXCL2 production. Neutrophils began infiltrating the kidney 3 hours after the second instillation and phagocytozed bacteria. Macrophages followed 3 hours later and contributed much less to both CXCL2 production and bacterial phagocytosis. To investigate whether DCs recruit neutrophils into the kidney for antibacterial defense, we used CD11c.DTR mice allowing conditional depletion of CD11c(+) dendritic cells. The absence of CD11c(+) DCs markedly delayed neutrophil recruitment and bacterial clearance. In conclusion, these findings suggest that the tubulointerstitial dendritic cell network serves an innate immune sentinel function against bacterial pyelonephritis.

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.

T cells infiltrate the kidney in both human and experimental glomerulonephritis, and several lines of evidence indicate that T cell-mediated tissue damage plays an important role in the immunopathogenesis of renal inflammatory diseases. However, the functions of the different T cell subsets, particularly the recently identified interleukin-17 (IL-17)-producing T cells (Th17 cells), are incompletely understood in glomerulonephritis. Here, we identified renal IL-17-producing T cells in the T cell-mediated model of nephrotoxic nephritis in mice. In vitro, IL-17 enhanced the production of the proinflammatory chemokines CCL2/MCP-1, CCL3/MIP-1alpha, and CCL20/LARC, which are implicated in the recruitment of T cells and monocytes, in mouse mesangial cells. To determine the function of Th17 cells in renal inflammation, we induced nephrotoxic nephritis in IL-23 p19(-/-) mice, which have reduced numbers of Th17 cells, and in IL-17(-/-) mice, which are deficient in the effector cytokine IL-17 itself. In comparison with nephritic wild-type mice, IL-23 p19(-/-) mice demonstrated less infiltration of Th17 cells, and both IL-23 p19(-/-) and IL-17(-/-) mice developed less severe nephritis as measured by renal function, albuminuria, and frequency of glomerular crescent formation. These results demonstrate that the IL-23/IL-17 pathway significantly contributes to renal tissue injury in experimental glomerulonephritis. Targeting the IL-23/Th17 axis may be a promising therapeutic strategy for the treatment of proliferative and crescentic glomerulonephritis.

The role of renal dendritic cells (DCs) in glomerulonephritis is unknown. This question was addressed in nephrotoxic nephritis, a murine model of human necrotizing glomerulonephritis, which is dependent on CD4(+) Th1 cells and macrophages. DCs in nephritic kidneys showed signs of activation, accumulated in the tubulo-interstitium, and infiltrated the periglomerular space surrounding inflamed glomeruli. In ex vivo coculture experiments with antigen-specific CD4(+) T cells, DCs stimulated the secretion of IL-10, which is known to attenuate nephrotoxic nephritis, and the Th1 cytokine IFNgamma. Endogenous renal CD4(+) T cells produced both of these cytokines as well, but those from nephritic mice secreted increased amounts of IL-10. Renal DCs were found to express ICOS-L, an inducer of IL-10. To evaluate the in vivo role of renal DCs in disease, CD11c(+) DCs were depleted on days 4 and 10 after the induction of nephritis by injecting CD11c-DTR/GFP mice with diphtheria toxin. Sparing DCs until day 4 did not affect the autologous phase of nephritis. The number of renal DCs was reduced by 70% to 80%, the number of renal macrophages was unchanged, and periglomerular infiltrates were eliminated. On days 11 to 14, we observed aggravated tubulointerstitial and glomerular damage, reduced creatinine clearance, and increased proteinuria. These findings demonstrate that renal DCs exert a renoprotective effect in nephrotoxic nephritis, possibly by expressing ICOS-L and/or by inducing IL-10 in infiltrating CD4(+) Th1 cells.

The chemokine receptor CXCR3 is highly expressed on Th1 polarized T cells and has been predicted to play an important role in T cell recruitment and immune response in a number of inflammatory and autoimmune diseases. For testing whether CXCR3 plays a role in renal inflammation, CXCR3-deficient mice were generated and nephrotoxic nephritis was induced in C57BL/6 CXCR3(-/-) and C57BL/6 wild-type mice. Induction of the nephrotoxic nephritis leads to an increased renal mRNA expression of IP-10/CXCL10 (8.6-fold), Mig/CXCL9 (2.3-fold), and I-TAC/CXCL11 (4.9-fold) during the autologous phase at days 7 and 14. This increased chemokine expression was paralleled by the renal infiltration of T cells, followed by renal tissue injury, albuminuria, and loss of renal function. Compared with wild-type mice, CXCR3-deficient mice had significantly reduced renal T cell infiltrates. Moreover, CXCR3(-/-) mice developed less severe nephritis, with significantly lower albuminuria, better renal function, and a reduced frequency of glomerular crescent formation. Nephritic wild-type and CXCR3(-/-) mice both elicited an efficient systemic nephritogenic immune response in terms of antigen-specific IgG production and IFN-gamma expression by splenocytes in response to the nephritogenic antigen. These findings indicate that the ameliorated nephritis in CXCR3-deficient mice is due to impaired renal trafficking of effector T cells rather than their inability to mount an efficient humoral or cellular immune response. The neutralization of CXCR3 might be a promising therapeutic strategy for Th1-dependent inflammatory renal disease.

Heat shock proteins (Hsp) are ubiquitous intracellular proteins that can be released in various forms of cellular stress. Some Hsp, such as Hsp60, have been shown to stimulate directly T cell-mediated immune responses in vitro. Here, it is demonstrated that Hsp60 is released from the kidneys and excreted into the urine of mice with nephrotoxic nephritis (NTN), a model of rapidly progressive glomerulonephritis. For examining the functional relevance of Hsp60 release, this protein was injected into mice with subnephritogenic NTN, in which only transient proteinuria and minimal organ damage occur that do not progress to terminal kidney failure. Injection of Hsp60 strikingly aggravated disease, as evidenced by global glomerular necrosis, tubulointerstitial damage, and complete anuria after 10 to 12 d. This effect was mediated neither by endotoxin contaminations of Hsp60 nor by autologous antibodies. It was strictly T cell dependent but not associated with a systemic Th1/Th2 shift. Thus, Hsp60 is an endogenous mediator stimulating immune effector mechanisms that contribute to the progression of NTN. These findings demonstrate in vivo that Hsp60 fulfills criteria of immunologic danger signals and suggest that such signals may be involved in immune-mediated kidney disease.

The kidney tubulointerstitium contains numerous bone marrow-derived antigen-presenting cells, which are often referred to as resident tissue macrophages, although several previous studies had demonstrated characteristics of dendritic cells (DC). In this study, we describe a subset of tubulointerstitial cells expressing the DC marker CD11c. A protocol was established to isolate these cells for in vitro analysis. Renal CD11c(+) cells resembled splenic DC, but not peritoneal macrophages, in morphology, lysosomal content, phagocytic activity, microbicidal effector functions, expression of T cell costimulatory molecules, and ability to activate T cells. Nevertheless, many CD11c(+) renal cells expressed low or intermediate levels of F4/80 and CD11b, indicating that both markers are not absolutely specific for macrophages in the kidney. Subpopulations of renal DC could be distinguished based on their expression of MHC class II and costimulatory molecules and may represent different maturation stages. In nephrotoxic glomerulonephritis, increased numbers of CD11c(+) cells showing DC functionality were found in the tubulointerstitium. Focal accumulation was seen within tubulointerstitial mononuclear infiltrates and adjacent to, but not within, inflamed glomeruli. These results are the first to identify and characterize renal CD11c(+) cells as DC and to demonstrate marked changes in experimental glomerulonephritis.