Th17 cells are most abundant in the gut, where their presence depends on the intestinal microbiota. Here, we examined whether intestinal Th17 cells contribute to extra-intestinal Th17 responses in ...autoimmune kidney disease. We found high frequencies of Th17 cells in the kidneys of patients with antineutrophil cytoplasmatic antibody (ANCA)-associated glomerulonephritis. We utilized photoconversion of intestinal cells in Kaede mice to track intestinal T cell mobilization upon glomerulonephritis induction, and we found that Th17 cells egress from the gut in a S1P-receptor-1-dependent fashion and subsequently migrate to the kidney via the CCL20/CCR6 axis. Depletion of intestinal Th17 cells in germ-free and antibiotic-treated mice ameliorated renal disease, whereas expansion of these cells upon Citrobacter rodentium infection exacerbated pathology. Thus, in some autoimmune settings, intestinal Th17 cells migrate into target organs, where they contribute to pathology. Targeting the intestinal Th17 cell “reservoir” may present a therapeutic strategy for these autoimmune disorders.
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•Pathogenic TH17 cells migrate from the gut to the kidney in autoimmunity•TH17 cells egress the intestine in a S1PR1-dependent manner in glomerulonephritis•Targeting microbiota-induced TH17 cells ameliorates extraintestinal TH17 responses
By photolabelling intestinal cells, Krebs and colleagues provide direct evidence that microbiota-induced TH17 cells egress from the gut S1PR1-dependently and infiltrate the kidney via CCL20/CCR6 in immune-mediated diseases. This finding will build the basis for therapies targeting the intestinal TH17 cell “reservoir” to treat extraintestinal TH17 autoimmunity.
Objective
The CD4+ T cell immune response plays a pivotal role in the immunopathogenesis of human and experimental lupus nephritis, but the contribution of the Th17/interleukin‐17 (IL‐17) immune ...pathway to renal tissue injury in systemic lupus erythematosus (SLE) remains to be elucidated. The aim of this study was to characterize the function of the Th17/IL‐17A immune response in 2 murine models of lupus nephritis.
Methods
IL‐17A–deficient MRL/MPJ‐Faslpr/2J (MRL/lpr) mice were generated, and the clinical course of nephritis was monitored by assessing the levels of albuminuria, extent of renal tissue injury, and functional parameters. In addition, lupus‐prone (NZB × NZW)F1 (NZB/NZW) mice were treated with anti–IL‐17A and anti–interferon‐γ (anti‐IFNγ) antibodies, and their effects on the clinical course of lupus nephritis were assessed.
Results
Characterization of renal IL‐17A–producing and IFNγ‐producing T cells in MRL/lpr and NZB/NZW mice revealed low numbers of infiltrating CD3+IL‐17A+ cells. Renal IL‐17A was mainly produced by CD4/CD8 double‐negative CD3+ T cells and CD4+ Th17 cells. In contrast, the number of renal CD3+IFNγ+ cells continuously increased over time and largely consisted of typical CD4+ Th1 cells. IL‐17A deficiency did not affect the morphologic or functional parameters in MRL/lpr mice with lupus nephritis, nor did IL‐17A neutralization affect the clinical course of nephritis in NZB/NZW mice, but anti‐IFNγ treatment attenuated the severity of the disease.
Conclusion
The Th17/IL‐17A immune response plays no major role in the immunopathogenesis of lupus nephritis in MRL/lpr and NZB/NZW mice. Thus, the results of this study do not support the hypothesis that IL‐17A targeting could be an intriguing new therapeutic approach for the management of proliferative lupus nephritis in SLE patients.
Immune-mediated glomerular diseases like crescentic glomerulonephritis (cGN) are driven by inappropriately regulated cellular and humoral immune responses subsequently leading to renal tissue injury. ...Recent studies demonstrated the crucial role for regulatory T cells (Tregs) in suppressing pathogenic T-cell responses during nephrotoxic nephritis (NTN), a murine model of cGN. However, mechanisms of immune regulation in cGN are less clear. Here, we aim at investigating the role of the co-inhibitory PD-1/PD-L1 pathway in Treg-mediated suppression of renal inflammation. We demonstrated that Foxp3
Tregs expressing PD-L1 infiltrate the kidney during NTN. Inhibition of PD-L1 signalling by using PD-L1
mice or by blockage of PD-L1 in wildtype mice resulted in an increased Treg frequency in the inflamed kidney. However, mice lacking PD-L1 developed more severe NTN associated with an elevated pathogenic renal Th1 immune response, which was reversed by blockage of IFNγ in these mice. Interestingly, lack of PD-L1 altered the gene expression profile of Tregs in homeostasis and kidney inflammation. Functionally, Tregs from nephritic PD-L1
mice had impaired suppressive capacity in vitro and failed to protect from NTN in vivo. Thus, PD-L1 displays a protective role in NTN, which is related to Treg-mediated suppression of the Th1 immune response.
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.
•Rapid progressive glomerulonephritis is a leading cause for end-stage renal disease.•IL-17 producing T cells were identified in human nephritic kidneys and in experimental models of crescentic ...glomerulonephritis.•IL-17 signaling on residential cells contributes to inflammatory tissue damage in experimental glomerulonephritis.•IL-17C promotes the TH17 cell immune response and therefore enhances renal disease pathology.•IL-17 signaling is a potential therapeutic target for rapid progressive glomerulonephritis.
Immune-mediated glomerular diseases (glomerulonephritis) encompass a heterogeneous collection of diseases that cause inflammation within the glomerulus and other renal compartments with significant morbidity and mortality. In general, CD4+ T cells orchestrate the immune response and play a unique role in autoimmune and chronic inflammatory diseases. In particular, the characterization of a distinct, IL-17 cytokines producing CD4+ T cell subset named TH17 cells has significantly advanced the current understanding of the pathogenic mechanisms of organ-specific immunity. Our group and others have shown that the recruitment of TH17 cells to the inflamed kidney drives renal tissue injury in experimental and possibly human crescentic glomerulonephritis (GN), but much remains to be understood about the biological functions, regulation, and signaling pathways of the TH17/IL-17 axis leading to organ damage. Here we review our current knowledge about the mechanisms and functions of IL-17 signaling in renal autoimmune diseases, with a special focus on experimental and human crescentic GN.
Infiltration of T cells into the kidney is a typical feature of human and experimental lupus nephritis that contributes to renal tissue injury. The chemokine receptor CXCR3 is highly expressed on Th1 ...cells and is supposed to be crucial for their trafficking into inflamed tissues. In this study, we explored the functional role of CXCR3 using the MRL/MpJ-Fas(lpr) (MRL/lpr) mouse model of systemic lupus erythematosus that closely resembles the human disease. CXCR3(-/-) mice were generated and backcrossed into the MRL/lpr background. Analysis of 20-wk-old CXCR3(-/-) MRL/lpr mice showed amelioration of nephritis with reduced glomerular tissue damage and decreased albuminuria and T cell recruitment. Most importantly, not only the numbers of renal IFN-gamma-producing Th1 cells, but also of IL-17-producing Th17 cells were significantly reduced. Unlike in inflamed kidneys, there was no reduction in the numbers of IFN-gamma- or IL-17-producing T cells in spleens, lymph nodes, or the small intestine of MRL/lpr CXCR3(-/-) mice. This observation suggests impaired trafficking of effector T cells to injured target organs, rather than the inability of CXCR3(-/-) mice to mount efficient Th1 and Th17 immune responses. These findings show a crucial role for CXCR3 in the development of experimental lupus nephritis by directing pathogenic effector T cells into the kidney. For the first time, we demonstrate a beneficial effect of CXCR3 deficiency through attenuation of both the Th1 and the newly defined Th17 immune response. Our data therefore identify the chemokine receptor CXCR3 as a promising therapeutic target in lupus nephritis.
Staphylococcus aureus is frequently detected in patients with sepsis and thus represents a major health burden worldwide. CD4+ T helper cells are involved in the immune response to S. aureus by ...supporting antibody production and phagocytosis. In particular, Th1 and Th17 cells secreting IFN-γ and IL-17A, are involved in the control of systemic S. aureus infections in humans and mice. To investigate the role of T cells in severe S. aureus infections, we established a mouse sepsis model in which the kidney was identified to be the organ with the highest bacterial load and abundance of Th17 cells. In this model, IL-17A but not IFN-γ was required for bacterial control. Using Il17aCre × R26YFP mice we could show that Th17 fate cells produce Th17 and Th1 cytokines, indicating a high degree of Th17 cell plasticity. Single cell RNA-sequencing of renal Th17 fate cells uncovered their heterogeneity and identified a cluster with a Th1 expression profile within the Th17 cell population, which was absent in mice with T-bet/Tbx21-deficiency in Th17 cells (Il17aCre x R26eYFP x Tbx21-flox). Blocking Th17 to Th1 transdifferentiation in Th17 fate cells in these mice resulted in increased S. aureus tissue loads. In summary, we highlight the impact of Th17 cells in controlling systemic S. aureus infections and show that T-bet expression by Th17 cells is required for bacterial clearance. While targeting the Th17 cell immune response is an important therapeutic option in autoimmunity, silencing Th17 cells might have detrimental effects in bacterial infections.
Recruitment of polymorphonuclear neutrophils (PMNs) remains a paramount prerequisite in innate immune defense and a critical cofounder in inflammatory vascular disease. Neutrophil recruitment ...comprises a cascade of concerted events allowing for capture, adhesion and extravasation of the leukocyte. Whereas PMN rolling, binding, and diapedesis are well characterized, receptor-mediated processes, mechanisms attenuating the electrostatic repulsion between the negatively charged glycocalyx of leukocyte and endothelium remain poorly understood. We provide evidence for myeloperoxidase (MPO), an abundant PMN-derived heme protein, facilitating PMN recruitment by its positive surface charge. In vitro, MPO evoked highly directed PMN motility, which was solely dependent on electrostatic interactions with the leukocyte's surface. In vivo, PMN recruitment was shown to be MPO-dependent in a model of hepatic ischemia and reperfusion, upon intraportal delivery of MPO and in the cremaster muscle exposed to local inflammation or to intraarterial MPO application. Given MPO's affinity to both the endothelial and the leukocyte's surface, MPO evolves as a mediator of PMN recruitment because of its positive surface charge. This electrostatic MPO effect not only displays a so far unrecognized, catalysis-independent function of the enzyme, but also highlights a principal mechanism of PMN attraction driven by physical forces.
The discovery of interleukin (IL)-17-producing CD4+ T (Th17) cells as a unique T-helper cell lineage has revised our understanding of T-cell-mediated tissue injury. Recent data from studies in humans ...and mice indicate that autoimmune diseases such as multiple sclerosis and rheumatoid arthritis, classically believed to be Th1-mediated, are predominantly driven by a Th17 immune response. IL-17 (IL-17A), IL-17F, IL-21, IL-22, and possibly also IL-9 produced by Th17 cells promote inflammation by directly causing tissue injury and enhancing secretion of pro-inflammatory cytokines and chemokines by resident cells. This results in augmented infiltration of leukocytes, in particular neutrophils, to the affected tissue where they induce organ inflammation and injury. Recent studies have highlighted the potential importance of the Th17 immune response also in renal inflammatory disease. This includes the identification and characterization of IL-17-producing T cells in nephritic kidneys of mice and humans, as well as evidence for the contribution of IL-17 and the IL-23/Th17 axis to renal tissue injury in glomerulonephritis. In this review, we will briefly summarize general characteristics of Th17 cells and discuss in detail the potential role of the Th17 immune response in human and experimental renal inflammation with a special focus on glomerulonephritis.
Th1 and Th17 subtype effector CD4+ T cells are thought to play a critical role in the pathogenesis of human and experimental crescentic glomerulonephritis. The time course, mechanism, and functions ...of Th1 and Th17 cell recruitment, and their potential interaction in glomerulonephritis, however, remain to be elucidated. We performed interventional studies using IL-17- and IFN-γ-gene-deficient mice, as well as neutralizing antibodies that demonstrated the importance of the Th17-mediated immune response during the early phase of the disease. At a later stage, we found that Th1 cells were critical mediators of renal tissue injury. Early recruitment of IL-17-producing Th17 cells triggered expression of the chemokine CXCL9 in the kidney that drove the infiltration of Th1 cells bearing its receptor CXCR3. At a later stage, Th1 cell–derived IFN-γ was found to inhibit local chemokine CCL20 expression, acting through its receptor CCR6 on Th17 cells, thereby limiting the renal Th17 immune response. Thus, our findings provide mechanistic evidence for a cytokine–chemokine-driven feedback loop that orchestrates the observed differential Th1 and Th17 cell infiltration into the inflamed kidney. This contributes to the observed time-dependent function of these two major pathogenic effector CD4+ T cell subsets in crescentic glomerulonephritis.
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