CD103+ Dendritic Cells Elicit CD8+ T Cell Responses to Accelerate Kidney Injury in Adriamycin Nephropathy

Adenine-induced animal model of chronic kidney disease: current applications and future perspectives

Chronic kidney disease (CKD) with high morbidity and mortality all over the world is characterized by decreased kidney function, a condition which can result from numerous risk factors, including diabetes, hypertension and obesity. Despite significant advances in our understanding of the pathogenesis of CKD, there are still no treatments that can effectively combat CKD, which underscores the urgent need for further study into the pathological mechanisms underlying this condition. In this regard, animal models of CKD are indispensable. This article reviews a widely used animal model of CKD, which is induced by adenine. While a physiologic dose of adenine is beneficial in terms of biological activity, a high dose of adenine is known to induce renal disease in the organism. Following a brief description of the procedure for disease induction by adenine, major mechanisms of adenine-induced CKD are then reviewed, including inflammation, oxidative stress, programmed cell death, metabolic disorders, and fibrillation. Finally, the application and future perspective of this adenine-induced CKD model as a platform for testing the efficacy of a variety of therapeutic approaches is also discussed. Given the simplicity and reproducibility of this animal model, it remains a valuable tool for studying the pathological mechanisms of CKD and identifying therapeutic targets to fight CKD.

Entinostat, nivolumab and ipilimumab for women with advanced HER2-negative breast cancer: a phase Ib trial

We report the results of 24 women, 50% (N = 12) with hormone receptor-positive breast cancer and 50% (N = 12) with advanced triple-negative breast cancer, treated with entinostat + nivolumab + ipilimumab from the dose escalation (N = 6) and expansion cohort (N = 18) of ETCTN-9844 ( NCT02453620 ). The primary endpoint was safety. Secondary endpoints were overall response rate, clinical benefit rate, progression-free survival and change in tumor CD8:FoxP3 ratio. There were no dose-limiting toxicities. Among evaluable participants (N = 20), the overall response rate was 25% (N = 5), with 40% (N = 4) in triple-negative breast cancer and 10% (N = 1) in hormone receptor-positive breast cancer. The clinical benefit rate was 40% (N = 8), and progression-free survival at 6 months was 50%. Exploratory analyses revealed that changes in myeloid cells may contribute to responses; however, no correlation was noted between changes in CD8:FoxP3 ratio, PD-L1 status and tumor mutational burden and response. These findings support further investigation of this treatment in a phase II trial.

CD8 T cells induce the peritubular capillary rarefaction during AKI to CKD transition

Acute kidney injury (AKI) transformed to chronic kidney disease (CKD) is a critical clinical issue characterized by tubulointerstitial inflammation (TII) and fibrosis. However, the exact mechanism remains largely unclear. In this study, we used single-cell RNA sequencing (scRNA-seq) to obtain a high-resolution profile of T cells in AKI to CKD transition with a mice model of unilateral ischemia-reperfusion injury (uIRI). We found that T cells accumulated increasingly with the progression of AKI to CKD, which was categorized into 9 clusters. A notably increased proportion of CD8 T cells via self-proliferation occurred in the early stage of AKI was identified. Further study revealed that the CD8 T cells were recruited through CXCL16-CXCR6 pathway mediated by macrophages. Notably, CD8 T cells induced endothelial cell apoptosis via Fas ligand-Fas signaling. Consistently, increased CD8 T cell infiltration accompanied with peritubular capillaries (PTCs) rarefaction was observed in uIRI mice. More impressively, the loss of PTCs and renal fibrosis was remarkably ameliorated after the elimination of CD8 T cells. In summary, our study provides a novel insight into the role of CD8 T cells in the transition from AKI to CKD via induction of PTCs rarefaction, which could suggest a promising therapeutic target for AKI.

Lilrb4 ameliorates ileal injury in rats with hemorrhagic shock and suppresses the activation of NF-κB signaling pathway

Hemorrhagic shock (HS) leads to intestinal damage and subsequent multiple organ dysfunction syndrome. Intestinal barrier dysfunction is the main cause of multiple organ failure associated with HS. Leukocyte immunoglobulin-like receptor B4 (Lilrb4) belongs to the Ig superfamily and is a vital natural immunomodulatory receptor. The purpose of this study was to identify the role and molecular mechanism of Lilrb4 in HS-induced ileal injury. In this work, HS was established by femoral artery cannula and 90 min of HS (blood pressure, 35-40 mmHg), followed by resuscitation. RNA sequencing analysis showed that Lilrb4 was highly expressed in the ileum of HS rats. As observed, HS rats exhibited severe ileal injury, characterized by enlarged subepithelial space, edema, exfoliation and extensive loss of villi. Whereas, lentivirus system-mediated Lilrb4 overexpression considerably mitigated these alterations. HS led to increased release of markers associated with intestinal injury, which was effectively reversed by Lilrb4 overexpression. In addition, after resuscitation, Lilrb4 overexpression inhibited HS-triggered inflammatory response, as evidenced by decreased levels of proinflammatory cytokines. Lilrb4 also inhibited the activation of NF-κB signal induced by HS. Notably, Lilrb4 modulated the balance of regulatory T (Treg)-T helper 17 (Th17) cells in the mesenteric lymph node (MLN), which may also contribute to its protective role in HS progression. In aggregate, these findings confirmed that Lilrb4 overexpression protected against ileal injury caused by HS, indicating that Lilrb4 may be a potential candidate for the treatment of HS.

Recent Advances in Understanding Peripheral and Gut Immune Cell-Mediated Salt-Sensitive Hypertension and Nephropathy

Hypertension is the primary modifiable risk factor for cardiovascular, renal, and cerebrovascular diseases and is considered the main contributing factor to morbidity and mortality worldwide. Approximately 50% of hypertensive and 25% of normotensive people exhibit salt sensitivity of blood pressure, which is an independent risk factor for cardiovascular disease. Human and animal studies demonstrate that the immune system plays an important role in the etiology and pathogenesis of salt sensitivity of blood pressure, kidney damage, and vascular diseases. Antigen-presenting and adaptive immune cells are implicated in salt-sensitive hypertension and salt-induced renal and vascular injury. Elevated sodium activates antigen-presenting cells to release proinflammatory cytokines including IL (interleukin) 6, tumor necrosis factor-α, IL-1β, and accumulate isolevuglandin-protein adducts. In turn, these activate T cells release prohypertensive cytokines including IL-17A. Moreover, high-salt intake is associated with gut dysbiosis, leading to inflammation, oxidative stress, and blood pressure elevation but the mechanistic contribution to salt-sensitivity of blood pressure is not clearly understood. Here, we discuss recent advances in research investigating the cause, potential biomarkers, and therapeutic targets for salt-sensitive hypertension as they pertain to the gut microbiome, immunity, and inflammation.

Mechanistic insights into the interaction between the host gut microbiome and malaria

Malaria is a devastating infectious disease and significant global health burden caused by the bite of a Plasmodium-infected female Anopheles mosquito. Gut microbiota was recently discovered as a risk factor of severe malaria. This review entails the recent advances on the impact of gut microbiota composition on malaria severity and consequence of malaria infection on gut microbiota in mammalian hosts. Additionally, this review provides mechanistic insight into interactions that might occur between gut microbiota and host immunity which in turn can modulate malaria severity. Finally, approaches to modulate gut microbiota composition are discussed. We anticipate this review will facilitate novel hypotheses to move the malaria-gut microbiome field forward.

Conventional type I migratory CD103+ dendritic cells are required for corneal allograft survival

Corneal transplant rejection primarily occurs because of the T helper 1 (Th1) effector cell-mediated immune response of the host towards allogeneic tissue. The evidence suggests that type 1 migratory conventional CD103+ dendritic cells (CD103+DC1) acquire an immunosuppressive phenotype in the tumor environment; however, the involvement of CD103+DC1 in allograft survival continues to be an elusive question of great clinical significance in tissue transplantation. In this study, we assess the role of CD103+DC1 in suppressing Th1 alloreactivity against transplanted corneal allografts. The immunosuppressive function of CD103+DC1 has been extensively studied in non-transplantation settings. We found that host CD103+DC1 infiltrates the corneal graft and migrates to the draining lymph nodes to suppress alloreactive CD4+ Th1 cells via the programmed death-ligand 1 axis. The systemic depletion of CD103+ DC1 in allograft recipients leads to amplified Th1 activation, impaired Treg function, and increased rate of allograft rejection. Although allograft recipient Rag1 null mice reconstituted with naïve CD4+CD25- T cells efficiently generated peripheral Treg cells (pTreg), the CD103+DC1-depleted mice failed to generate pTreg. Furthermore, adoptive transfer of pTreg failed to rescue allografts in CD103+DC1-depleted recipients from rejection. These data demonstrate the critical role of CD103+DC1 in regulating host alloimmune responses.

Immune responses in the uterine mucosa: clues for vaccine development in pigs

The immune system in the upper reproductive tract (URT) protects against sexually transmitted pathogens, while at the same time providing immune tolerance responses against allogenic sperm and the developing fetus. The uterine environment is also responsive to hormonal variations during the estrus cycle, although the most likely timing of exposure to pathogens is during estrus and breeding when the cervix is semi-permissive. The goal for intrauterine immunization would be to induce local or systemic immunity and/or to promote colostral/lactogenic immunity that will passively protect suckling offspring. The developing fetus is not the vaccine target. This minireview article focuses on the immune response induced in the pig uterus (uterine body and uterine horns) with some comparative references to other livestock species, mice, and humans.

The impact of the cytoplasmic ubiquitin ligase TNFAIP3 gene variation on transcription factor NF-κB activation in acute kidney injury

Nuclear factor κB (NF-κB) activation is a deleterious molecular mechanism that drives acute kidney injury (AKI) and manifests in transplanted kidneys as delayed graft function. The TNFAIP3 gene encodes A20, a cytoplasmic ubiquitin ligase and a master negative regulator of the NF- κB signaling pathway. Common population-specific TNFAIP3 coding variants that reduce A20's enzyme function and increase NF- κB activation have been linked to heightened protective immunity and autoimmune disease, but have not been investigated in AKI. Here, we functionally identified a series of unique human TNFAIP3 coding variants linked to the autoimmune genome-wide association studies single nucleotide polymorphisms of F127C; namely F127C;R22Q, F127C;G281E, F127C;W448C and F127C;N449K that reduce A20's anti-inflammatory function in an NF- κB reporter assay. To investigate the impact of TNFAIP3 hypomorphic coding variants in AKI we tested a mouse Tnfaip3 hypomorph in a model of ischemia reperfusion injury (IRI). The mouse Tnfaip3 coding variant I325N increases NF- κB activation without overt inflammatory disease, providing an immune boost as I325N mice exhibit enhanced innate immunity to a bacterial challenge. Surprisingly, despite exhibiting increased intra-kidney NF- κB activation with inflammation in IRI, the kidney of I325N mice was protected. The I325N variant influenced the outcome of IRI by changing the dynamic expression of multiple cytoprotective mechanisms, particularly by increasing NF- κB-dependent anti-apoptotic factors BCL-2, BCL-XL, c-FLIP and A20, altering the active redox state of the kidney with a reduction of superoxide levels and the enzyme super oxide dismutase-1, and enhancing cellular protective mechanisms including increased Foxp3⁺ T cells. Thus, TNFAIP3 gene variants represent a kidney and population-specific molecular factor that can dictate the course of IRI.

Attenuation of renal injury by depleting cDC1 and by repurposing Flt3 inhibitor in anti-GBM disease

Previous studies found cDC1s to be protective in early stage anti-GBM disease through Tregs, but pathogenic in late stage Adriamycin nephropathy through CD8⁺ T cells. Flt3 ligand is a growth factor essential for cDC1 development and Flt3 inhibitors are currently used for cancer treatment. We conducted this study to clarify the role and mechanisms of effects of cDC1s at different time points in anti-GBM disease. In addition, we aimed to utilize drug repurposing of Flt3 inhibitors to target cDC1s as a treatment of anti-GBM disease. We found that in human anti-GBM disease, the number of cDC1s increased significantly, proportionally more than cDC2s. The number of CD8⁺ T cells also increased significantly and their number correlated with cDC1 number. In XCR1-DTR mice, late (day 12-21) but not early (day 3-12) depletion of cDC1s attenuated kidney injury in mice with anti-GBM disease. cDC1s separated from kidneys of anti-GBM disease mice were found to have a pro-inflammatory phenotype (i.e. express high level of IL-6 and IL-12) in late but not early stage. In the late depletion model, the number of CD8⁺ T cells was also reduced, but not Tregs. CD8⁺ T cells separated from kidneys of anti-GBM disease mice expressed high levels of cytotoxic molecules (granzyme B and perforin) and inflammatory cytokines (TNF-α and IFN-γ), and their expression reduced significantly after cDC1 depletion with diphtheria toxin. These findings were reproduced using a Flt3 inhibitor in wild type mice. Therefore, cDC1s are pathogenic in anti-GBM disease through activation of CD8⁺ T cells. Flt3 inhibition successfully attenuated kidney injury through depletion of cDC1s. Repurposing Flt3 inhibitors has potential as a novel therapeutic strategy for anti-GBM disease.

Metabolic signatures of immune cells in chronic kidney disease

Immune cells play a key role in maintaining renal dynamic balance and dealing with renal injury. The physiological and pathological functions of immune cells are intricately connected to their metabolic characteristics. However, immunometabolism in chronic kidney disease (CKD) is not fully understood. Pathophysiologically, disruption of kidney immune cells homeostasis causes inflammation and tissue damage via triggering metabolic reprogramming. The diverse metabolic characteristics of immune cells at different stages of CKD are strongly associated with their different pathological effect. In this work, we reviewed the metabolic characteristics of immune cells (macrophages, natural killer cells, T cells, natural killer T cells and B cells) and several non-immune cells, as well as potential treatments targeting immunometabolism in CKD. We attempt to elaborate on the metabolic signatures of immune cells and their intimate correlation with non-immune cells in CKD.

M2c Macrophages Protect Mice from Adriamycin-Induced Nephropathy by Upregulating CD62L in Tregs

Regulatory T cells (Tregs) and M2c macrophages have been shown to exert potentially synergistic therapeutic effects in animals with adriamycin-induced nephropathy (AN), a model chronic proteinuric renal disease. M2c macrophages may protect against renal injury by promoting an increase in the number of Tregs in the renal draining lymph nodes of AN mice, but how they do so is unclear. In this study, we used an AN mouse model to analyze how M2c macrophages induce the migration of Tregs. Using flow cytometry, we found that M2c macrophages promoted the migration of Tregs from the peripheral blood to the spleen, thymus, kidney, and renal draining lymph nodes. At the same time, M2c macrophages significantly upregulated chemokine receptors and adhesion molecule in Tregs, including CCR4, CCR5, CCR7, CXCR5, and CD62L. Treating AN mice with monoclonal anti-CD62L antibody inhibited the migration of M2c macrophages and Tregs to the spleen, thymus, kidney, and renal draining lymph nodes. Taken together, our results suggest that M2c macrophages upregulate CD62L in Tregs and thereby promote their migration to inflammatory sites, where they exert renoprotective effects. These insights may aid the development of treatments against chronic kidney disease.

IL-23 signaling prevents ferroptosis-driven renal immunopathology during candidiasis

During infection the host relies on pattern-recognition receptors to sense invading fungal pathogens to launch immune defense mechanisms. While fungal recognition and immune effector responses are organ and cell type specific, during disseminated candidiasis myeloid cells exacerbate collateral tissue damage. The β-glucan receptor ephrin type-A 2 receptor (EphA2) is required to initiate mucosal inflammatory responses during oral Candida infection. Here we report that EphA2 promotes renal immunopathology during disseminated candidiasis. EphA2 deficiency leads to reduced renal inflammation and injury. Comprehensive analyses reveal that EphA2 restrains IL-23 secretion from and migration of dendritic cells. IL-23 signaling prevents ferroptotic host cell death during infection to limit inflammation and immunopathology. Further, host cell ferroptosis limits antifungal effector functions via releasing the lipid peroxidation product 4-hydroxynonenal to induce various forms of cell death. Thus, we identify ferroptotic cell death as a critical pathway of Candida-mediated renal immunopathology that opens a new avenue to tackle Candida infection and inflammation.

Actions of Dendritic Cells in the Kidney during Hypertension

The immune response plays a critical role in the pathogenesis of hypertension, and immune cell populations can promote blood pressure elevation via actions in the kidney. Among these cell lineages, dendritic cells (DCs), the most potent antigen-presenting cells, play a central role in regulating immune response during hypertension and kidney disease. DCs have different subtypes, and renal DCs are comprised of the CD103⁺ CD11b^- and CD103^- CD11b⁺ subsets. DCs become mature and express costimulatory molecules on their surface once they encounter antigen. Isolevuglandin-modified proteins function as antigens to activate DCs and trigger them to stimulate T cells. Activated T cells accumulate in the hypertensive kidney, release effector cytokines, promote renal oxidative stress, and promote renal salt and water retention. Individual subsets of activated T cells can secrete tumor necrosis factor-alpha, interleukin-17A, and interferon-gamma, each of which has augmented the elevation of blood pressure in hypertensive models by enhancing renal sodium transport. Fms-like tyrosine kinase 3 ligand-dependent classical DCs are required to sustain the full hypertensive response, but C-X₃ -C chemokine receptor 1 positive DCs do not regulate blood pressure. Excess sodium enters the DC through transporters to activate DCs, whereas the ubiquitin editor A20 in dendritic cells constrains blood pressure elevation by limiting T cell activation. By contrast, activation of the salt sensing kinase, serum/glucocorticoid kinase 1 in DCs exacerbates salt-sensitive hypertension. This article discusses recent studies illustrating mechanisms through which DC-T cell interactions modulate levels of pro-hypertensive mediators to regulate blood pressure via actions in the kidney. © 2022 American Physiological Society. Compr Physiol 12:1-15, 2022.

Imbalance of circulating innate lymphoid cell subpopulations in patients with chronic kidney disease

Innate lymphoid cells (ILCs) are a newly identified heterogeneous family of innate immune cells. We conducted this study to investigate the frequency of circulating ILC subsets in various chronic kidney diseases (CKD). In DN, the proportion of total ILCs and certain ILC subgroups increased significantly. Positive correlations between proportion of total ILCs, ILC1s and body mass index, glycated hemoglobin were observed in DN. In LN, a significantly increased proportion of ILC1s was found in parallel with a reduced proportion of ILC2s. The proportions of total ILCs and ILC1s were correlated with WBC count and the level of C3. In all enrolled patients, the proportion of total ILCs and ILC1s was significantly correlated with the levels of ACR and GFR. In the present study, the proportion of circulating ILC subsets increased significantly in various types of CKD and correlated with clinico-pathological features, which suggests a possible role for ILCs in CKD.

Assessing and counteracting fibrosis is a cornerstone of the treatment of CKD secondary to systemic and renal limited autoimmune disorders

Chronic kidney disease (CKD) is an increasing cause of morbidity and mortality worldwide. Besides the higher prevalence of diabetes, hypertension and aging worldwide, immune mediated disorders remain an important cause of kidney disease and are especially prevalent in young adults. Regardless of the initial insult, final pathway to CKD and kidney failure is always the loss of normal tissue and fibrosis development, in which the dynamic equilibrium between extracellular matrix synthesis and degradation is disturbed, leading to excessive production and accumulation. During fibrosis, a multitude of cell types intervene at different levels, but myofibroblasts and inflammatory cells are considered critical in the process. They exert their effects through different molecular pathways, of which transforming growth factor β (TGF-β) has demonstrated to be of particular importance. Additionally, CKD itself promotes fibrosis due to the accumulation of toxins and hormonal changes, and proteinuria is simultaneously a manifestation of CKD and a specific driver of renal fibrosis. Pathways involved in renal fibrosis and CKD are closely interrelated, and although important advances have been made in our knowledge of them, it is still necessary to translate them into clinical practice. Given the complexity of this process, it is highly likely that its treatment will require a multi-target strategy to control the origin of the damage but also the mechanisms that perpetuate it. Fortunately, rapid technology development over the last years and new available drugs in the nephrologist's armamentarium give reasons for optimism that more personalized assistance for CKD and renal fibrosis will appear in the future.

Twist1 in podocytes ameliorates podocyte injury and proteinuria by limiting CCL2-dependent macrophage infiltration

The transcription factor Twist1 regulates several processes that could impact kidney disease progression, including epithelial cell differentiation and inflammatory cytokine induction. Podocytes are specialized epithelia that exhibit features of immune cells and could therefore mediate unique effects of Twist1 on glomerular disease. To study Twist1 functions in podocytes during proteinuric kidney disease, we employed a conditional mutant mouse in which Twist1 was selectively ablated in podocytes (Twist1-PKO). Deletion of Twist1 in podocytes augmented proteinuria, podocyte injury, and foot process effacement in glomerular injury models. Twist1 in podocytes constrained renal accumulation of monocytes/macrophages and glomerular expression of CCL2 and the macrophage cytokine TNF-α after injury. Deletion of TNF-α selectively from podocytes had no impact on the progression of proteinuric nephropathy. By contrast, the inhibition of CCL2 abrogated the exaggeration in proteinuria and podocyte injury accruing from podocyte Twist1 deletion. Collectively, Twist1 in podocytes mitigated urine albumin excretion and podocyte injury in proteinuric kidney diseases by limiting CCL2 induction that drove monocyte/macrophage infiltration into injured glomeruli. Myeloid cells, rather than podocytes, further promoted podocyte injury and glomerular disease by secreting TNF-α. These data highlight the capacity of Twist1 in the podocyte to mitigate glomerular injury by curtailing the local myeloid immune response.

Role of Dendritic Cell in Diabetic Nephropathy

Diabetic nephropathy (DN) is one of the most significant microvascular complications in diabetic patients. DN is the leading cause of end-stage renal disease, accounting for approximately 50% of incident cases. The current treatment options, such as optimal control of hyperglycemia and elevated blood pressure, are insufficient to prevent its progression. DN has been considered as a nonimmune, metabolic, or hemodynamic glomerular disease initiated by hyperglycemia. However, recent studies suggest that DN is an inflammatory disease, and immune cells related with innate and adaptive immunity, such as macrophage and T cells, might be involved in its development and progression. Although it has been revealed that kidney dendritic cells (DCs) accumulation in the renal tissue of human and animal models of DN require activated T cells in the kidney disease, little is known about the function of DCs in DN. In this review, we describe kidney DCs and their subsets, and the role in the pathogenesis of DN. We also suggest how to improve the kidney outcomes by modulating kidney DCs optimally in the patients with DN.

A flow cytometry approach reveals heterogeneity in conventional subsets of murine renal mononuclear phagocytes

Mononuclear phagocytes (MNPs) participate in inflammation and repair after kidney injury, reflecting their complex nature. Dissection into refined functional subunits has been challenging and would benefit understanding of renal pathologies. Flow cytometric approaches are limited to classifications of either different MNP subsets or functional state. We sought to combine these two dimensions in one protocol that considers functional heterogeneity in each MNP subset. We identified five distinct renal MNP subsets based on a previously described strategy. In vitro polarization of bone marrow-derived macrophages (BMDM) into M1- and M2-like cells suggested functional distinction of CD86 + MHCII + CD206- and CD206 + cells. Combination of both distinction methods identified CD86 + MHCII + CD206- and CD206 + cells in all five MNP subsets, revealing their heterologous nature. Our approach revealed that MNP composition and their functional segmentation varied between different mouse models of kidney injury and, moreover, was dynamically regulated in a time-dependent manner. CD206 + cells from three analyzed MNP subsets had a higher ex vivo phagocytic capacity than CD86 + MHCII + CD206- counterparts, indicating functional uniqueness of each subset. In conclusion, our novel flow cytometric approach refines insights into renal MNP heterogeneity and therefore could benefit mechanistic understanding of renal pathology.

IRF8-Dependent Type I Conventional Dendritic Cells (cDC1s) Control Post-Ischemic Inflammation and Mildly Protect Against Post-Ischemic Acute Kidney Injury and Disease

Post-ischemic acute kidney injury and disease (AKI/AKD) involve acute tubular necrosis and irreversible nephron loss. Mononuclear phagocytes including conventional dendritic cells (cDCs) are present during different phases of injury and repair, but the functional contribution of this subset remains controversial. Transcription factor interferon regulatory factor 8 (IRF8) is required for the development of type I conventional dendritic cells (cDC1s) lineage and helps to define distinct cDC1 subsets. We identified one distinct subset among mononuclear phagocyte subsets according to the expression patterns of CD11b and CD11c in healthy kidney and lymphoid organs, of which IRF8 was significantly expressed in the CD11b^lowCD11c^high subset that mainly comprised cDC1s. Next, we applied a Irf8-deficient mouse line (Irf8^fl/flClec9a^cre mice) to specifically target Clec9a-expressing cDC1s in vivo. During post-ischemic AKI/AKD, these mice lacked cDC1s in the kidney without affecting cDC2s. The absence of cDC1s mildly aggravated the loss of living primary tubule and decline of kidney function, which was associated with decreased anti-inflammatory Tregs-related immune responses, but increased T helper type 1 (T_H1)-related and pro-inflammatory cytokines, infiltrating neutrophils and acute tubular cell death, while we also observed a reduced number of cytotoxic CD8⁺ T cells in the kidney when cDC1s were absent. Together, our data show that IRF8 is indispensable for kidney cDC1s. Kidney cDC1s mildly protect against post-ischemic AKI/AKD, probably via suppressing tissue inflammation and damage, which implies an immunoregulatory role for cDC1s.

Conventional Type 1 Dendritic Cells (cDC1) in Human Kidney Diseases: Clinico-Pathological Correlations

Background

cDC1 is a subset of conventional DCs, whose most recognized function is cross-presentation to CD8⁺ T cells. We conducted this study to investigate the number and location of cDC1s in various human kidney diseases as well as their correlation with clinico-pathological features and CD8⁺ T cells.

Methods

We analyzed 135 kidney biopsies samples. Kidney diseases included: acute tubular necrosis (ATN), acute interstitial nephritis (AIN), proliferative glomerulonephritis (GN) (IgA nephropathy, lupus nephritis, pauci-immune GN, anti-GBM disease), non-proliferative GN (minimal change disease, membranous nephropathy) and diabetic nephropathy. Indirect immunofluorescence staining was used to quantify cDC1s, CD1c⁺ DCs, and CD8⁺ T cells.

Results

cDC1s were rarely present in normal kidneys. Their number increased significantly in ATN and proliferative GN, proportionally much more than CD1c⁺ DCs. cDC1s were mainly found in the interstitium, except in lupus nephritis, pauci-immune GN and anti-GBM disease, where they were prominent in glomeruli and peri-glomerular regions. The number of cDC1s correlated with disease severity in ATN, number of crescents in pauci-immune GN, interstitial fibrosis in IgA nephropathy and lupus nephritis, as well as prognosis in IgA nephropathy. The number of CD8⁺ T cells also increased significantly in these conditions and cDC1 number correlated with CD8⁺ T cell number in lupus nephritis and pauci-immune GN, with many of them closely co-localized.

Conclusions

cDC1 number correlated with various clinic-pathological features and prognosis reflecting a possible role in these conditions. Their association with CD8⁺ T cells suggests a combined mechanism in keeping with the results in animal models.

TGF-β1 Signaling: Immune Dynamics of Chronic Kidney Diseases

Chronic kidney disease (CKD) is a major cause of morbidity and mortality worldwide, imposing a great burden on the healthcare system. Regrettably, effective CKD therapeutic strategies are yet available due to their elusive pathogenic mechanisms. CKD is featured by progressive inflammation and fibrosis associated with immune cell dysfunction, leading to the formation of an inflammatory microenvironment, which ultimately exacerbating renal fibrosis. Transforming growth factor β1 (TGF-β1) is an indispensable immunoregulator promoting CKD progression by controlling the activation, proliferation, and apoptosis of immunocytes via both canonical and non-canonical pathways. More importantly, recent studies have uncovered a new mechanism of TGF-β1 for de novo generation of myofibroblast via macrophage-myofibroblast transition (MMT). This review will update the versatile roles of TGF-β signaling in the dynamics of renal immunity, a better understanding may facilitate the discovery of novel therapeutic strategies against CKD.

Lung CD103+dendritic cells and Clec9a signaling are required for neonatal hyperoxia-induced inflammatory responses to rhinovirus infection

Premature infants, especially those with bronchopulmonary dysplasia (BPD), develop recurrent severe respiratory viral illnesses. We have shown that hyperoxic exposure of immature mice, a model of BPD, increases lung IL-12-producing Clec9a+ CD103+ dendritic cells (DCs), pro-inflammatory responses, and airway hyperreactivity following rhinovirus (RV) infection. However, the requirement for CD103+ DCs and Clec9a, a DAMP receptor that binds necrotic cell cytoskeletal filamentous actin (F-actin), for RV-induced inflammatory responses has not been demonstrated. To test this, 2-day-old C57BL/6J, CD103+ DC-deficient Batf3-/- or Clec9agfp-/- mice were exposed to normoxia or hyperoxia for 14 days. Also, selected mice were treated with neutralizing antibody against CD103. Immediately after hyperoxia, the mice were inoculated with RV intranasally. We found that compared with wild-type mice, hyperoxia-exposed Batf3-/- mice showed reduced levels of IL-12p40, IFN-γ, and TNF-α, fewer IFN-γ-producing CD4+ T cells, and decreased airway responsiveness following RV infection. Similar effects were observed in anti-CD103-treated and Clec9agfp-/- mice. Furthermore, hyperoxia increased airway dead cell number and extracellular F-actin levels. Finally, studies in preterm infants with respiratory distress syndrome showed that tracheal aspirate CLEC9A expression positively correlated with IL12B expression, consistent with the notion that CLEC9A+ cells are responsible for IL-12 production in humans as well as mice. We conclude that CD103+ DCs and Clec9a are required for hyperoxia-induced pro-inflammatory responses to RV infection. In premature infants, Clec9a-mediated activation of CD103+ DCs may promote pro-inflammatory responses to viral infection, thereby driving respiratory morbidity.

Innate lymphoid cells in kidney diseases

It is well known that innate immune cells, including dendritic cells, macrophages, and natural killer cells, contribute to pathogenesis and protection in various kidney diseases. The understanding of innate immunity has been advanced recently by the discovery of a new group of innate lymphoid cells (ILCs), including ILC1, ILC2, and ILC3. ILCs lack adaptive antigen receptors, yet can be triggered by various pathogens and rapidly provide an abundant source of immunomodulatory cytokines to exert immediate immune reactions and direct subsequent innate and adaptive immune responses. ILCs play critical roles in immunity, tissue homeostasis, and pathological inflammation. In this review, we highlight the biological function of ILC subpopulations in the normal kidney, and their important roles in acute and chronic kidney diseases, thus demonstrating the emerging importance of ILC-regulated immunity in this special organ and providing insights for future research directions and therapeutic interventions.

Repurposing of metformin and colchicine reveals differential modulation of acute and chronic kidney injury

Acute kidney injury (AKI) is a major health problem affecting millions of patients globally. There is no effective treatment for AKI and new therapies are urgently needed. Novel drug development, testing and progression to clinical trials is overwhelmingly expensive. Drug repurposing is a more cost-effective measure. We identified 2 commonly used drugs (colchicine and metformin) that alter inflammatory cell function and signalling pathways characteristic of AKI, and tested them in models of acute and chronic kidney injury to assess therapeutic benefit. We assessed the renoprotective effects of colchicine or metformin in C57BL/6 mice challenged with renal ischemia reperfusion injury (IRI), treated before or after injury. All animals underwent analysis of renal function and biomolecular phenotyping at 24 h, 48 h and 4 weeks after injury. Murine renal tubular epithelial cells were studied in response to in vitro mimics of IRI. Pre-emptive treatment with colchicine or metformin protected against AKI, with lower serum creatinine, improved histological changes and decreased TUNEL staining. Pro-inflammatory cytokine profile and multiple markers of oxidative stress were not substantially different between groups. Metformin augmented expression of multiple autophagic proteins which was reversed by the addition of hydroxychloroquine. Colchicine led to an increase in inflammatory cells within the renal parenchyma. Chronic exposure after acute injury to either therapeutic agent in the context of reduced renal mass did not mitigate the development of fibrosis, with colchicine significantly worsening an ischemic phenotype. These data indicate that colchicine and metformin affect acute and chronic kidney injury differently. This has significant implications for potential drug repurposing, as baseline renal disease must be considered when selecting medication.

Impact of anatomic site on antigen-presenting cells in cancer

Checkpoint blockade immunotherapy (CBT) can induce long-term clinical benefits in patients with advanced cancer; however, response rates to CBT vary by cancer type. Cancers of the skin, lung, and kidney are largely responsive to CBT, while cancers of the pancreas, ovary, breast, and metastatic lesions to the liver respond poorly. The impact of tissue-resident immune cells on antitumor immunity is an emerging area of investigation. Recent evidence indicates that antitumor immune responses and efficacy of CBT depend on the tissue site of the tumor lesion. As myeloid cells are predominantly tissue-resident and can shape tumor-reactive T cell responses, it is conceivable that tissue-specific differences in their function underlie the tissue-site-dependent variability in CBT responses. Understanding the roles of tissue-specific myeloid cells in antitumor immunity can open new avenues for treatment design. In this review, we discuss the roles of tissue-specific antigen-presenting cells (APCs) in governing antitumor immune responses, with a particular focus on the contributions of tissue-specific dendritic cells. Using the framework of the Cancer-Immunity Cycle, we examine the contributions of tissue-specific APC in CBT-sensitive and CBT-resistant carcinomas, highlight how these cells can be therapeutically modulated, and identify gaps in knowledge that remain to be addressed.

Podocytes present antigen to activate specific T cell immune responses in inflammatory renal disease

Infiltration of activated T cells into renal tissue plays an essential role in inflammatory nephropathy. However, the mechanism enabling the renal recruitment and activation of T cells remains elusive. Here we report that inflammatory cytokine-promoted antigen presentation by podocytes is a key for recruiting and activating specific T cells. Our results showed that diabetes-associated inflammatory cytokines IFNγ and IL-17 all upregulated expression of MHC-I, MHC-II, CD80 and CD86 on the podocyte surface. Both IFNγ and IL-17 stimulated the uptake and processing of ovalbumin (OVA) by mouse podocytes, resulting in presentation of OVA antigen peptide on the cell surface. OVA antigen presentation by podocytes was also validated using human podocytes. Furthermore, OVA antigen-presenting mouse podocytes were able to activate OT-I mouse T cell proliferation and inflammatory cytokine secretion, which in turn caused podocyte injury and apoptosis. Finally, OT-I mice subjected to direct renal injection of OVA plus IFNγ/IL-17 but not OVA alone exhibited OVA antigen presentation by podocytes and developed nephropathy in 4 weeks. In conclusion, antigen presentation by podocytes under inflammatory conditions plays an important role in activating T cell immune responses and facilitating immune-mediated glomerular disease development. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Regulatory T Cells as a Novel Candidate for Cell-Based Therapy in Kidney Disease

Kidney disease is a significant health concern worldwide. Ineffective treatment can lead to disastrous consequences, such as organ failure and death. Research has turned to cell-based therapy, but has yet to produce an effective and reliable treatment for kidney disease. To address this problem, we examined four datasets of gene expression profiles from diseased and healthy kidney tissue in humans, mice, and rats. Differentially expressed genes (DEGs) were screened and subjected to enrichment analyses. Up-regulated genes in diseased kidney tissue were significantly enriched in pathways associated with regulatory T cells (Tregs). Analysis with the xCell tool showed that Tregs were generally increased in diseased kidney tissue in all species. To validate these results in vivo, kidneys were removed from mice with Adriamycin-induced nephropathy, and histology confirmed increase of Tregs. Furthermore, Tregs were adoptively transferred from healthy mice into mice with kidney injury, restoring normal structure to the damaged kidneys. Treg cells that were co-cultured with M2c macrophages exhibited up-regulation of chemokine receptors CCR2, CCR5, CCR7, CD62L, and CX3CR1. This may be the mechanism by which M2c cells enhance the migration of Tregs to the site of inflammation. We propose that Tregs may be an effective, novel candidate for cell-based therapy in pre-clinical kidney injury models.

The Emerging Role of Innate Immunity in Chronic Kidney Diseases

Renal fibrosis is a common fate of chronic kidney diseases. Emerging studies suggest that unsolved inflammation will progressively transit into tissue fibrosis that finally results in an irreversible end-stage renal disease (ESRD). Renal inflammation recruits and activates immunocytes, which largely promotes tissue scarring of the diseased kidney. Importantly, studies have suggested a crucial role of innate immunity in the pathologic basis of kidney diseases. This review provides an update of both clinical and experimental information, focused on how innate immune signaling contributes to renal fibrogenesis. A better understanding of the underlying mechanisms may uncover a novel therapeutic strategy for ESRD.

Flt3 inhibition alleviates chronic kidney disease by suppressing CD103+ dendritic cell-mediated T cell activation

BACKGROUND

Chronic kidney disease (CKD) is a global public health problem, which lacks effective treatment. Previously, we have shown that CD103+ dendritic cells (DCs) are pathogenic in adriamycin nephropathy (AN), a model of human focal segmental glomerulosclerosis (FSGS). Fms-like tyrosine kinase 3 (Flt3) is a receptor that is expressed with high specificity on tissue resident CD103+ DCs.

METHODS

To test the effect on CD103+ DCs and kidney injury of inhibition of Flt3, we used a selective Flt3 inhibitor (AC220) to treat mice with AN.

RESULTS

Human CD141+ DCs, homologous to murine CD103+ DCs, were significantly increased in patients with FSGS. The number of kidney CD103+ DCs, but not CD103- DCs or plasmacytoid DCs, was significantly decreased in AN mice after AC220 administration. Treatment with AC220 significantly improved kidney function and reduced kidney injury and fibrosis in AN mice. AC220-treated AN mice had decreased levels of inflammatory cytokines and chemokines, tumor necrosis factor-α, interleukin (IL)-1β, IL-6, CCL2 and CCL5 and reduced kidney infiltration of CD4 T cells and CD8 T cells. The protective effect of AC220 was associated with its suppression of CD103+ DCs-mediated CD8 T cell proliferation and activation in AN mice.

CONCLUSION

Flt3 inhibitor AC220 effectively reduced kidney injury in AN mice, suggesting that this inhibitor might be a useful pharmaceutical agent to treat CKD.

Mesenchymal stem cells alleviate rat diabetic nephropathy by suppressing CD103+ DCs-mediated CD8+ T cell responses

Diabetic nephropathy (DN) as a kind of serious microvascular complication of Diabetes Mellitus (DM) usually causes the end‐stage of renal disease (ESRD). Studies have demonstrated that CD103⁺ dendritic cells (DCs) exhibited a renal pathogenic effect in murine chronic kidney disease (CKD). Mesenchymal stem cells (MSCs) can alleviate DN and suppress the DCs maturation. To explore the role of CD103⁺ DCs and the potential mechanisms underlying MSCs‐mediated protective effects in DN, we used bone marrow MSCs (BM‐MSCs) to treat DN rats. MSCs transplantation considerably recovered kidney function and diminished renal injury, fibrosis and the population of renal CD103⁺ DCs in DN rat. The MSCs‐treated DN rats had decreased mRNA expression levels of interleukin (IL)1β, IL6, tumour necrosis factor alpha (TNF‐α), monocyte chemotactic protein 1 (MCP‐1) and reduced CD8 T cell infiltration in the kidney. MSCs significantly down‐regulated the genes expression of transcription factors (Basic leucine zipper transcriptional factor ATF‐like 3, Batf3 and DNA‐binding protein inhibitor ID‐2, Id2) and FMS‐like tyrosine kinase‐3 (Flt3) which are necessary for CD103⁺ DCs development. The protective effect of MSCs may be partly related to their immunosuppression of CD8⁺ T cell proliferation and activation mediated by CD103⁺ DCs in the kidney of DN rats.

Inflammation in Renal Diseases: New and Old Players

Inflammation, a process intimately linked to renal disease, can be defined as a complex network of interactions between renal parenchymal cells and resident immune cells, such as macrophages and dendritic cells, coupled with recruitment of circulating monocytes, lymphocytes, and neutrophils. Once stimulated, these cells activate specialized structures such as Toll-like receptor and Nod-like receptor (NLR). By detecting danger-associated molecules, these receptors can set in motion major innate immunity pathways such as nuclear factor ĸB (NF-ĸB) and NLRP3 inflammasome, causing metabolic reprogramming and phenotype changes of immune and parenchymal cells and triggering the secretion of a number of inflammatory mediators that can cause irreversible tissue damage and functional loss. Growing evidence suggests that this response can be deeply impacted by the crosstalk between the kidneys and other organs, such as the gut. Changes in the composition and/or metabolite production of the gut microbiota can influence inflammation, oxidative stress, and fibrosis, thus offering opportunities to positively manipulate the composition and/or functionality of gut microbiota and, consequentially, ameliorate deleterious consequences of renal diseases. In this review, we summarize the most recent evidence that renal inflammation can be ameliorated by interfering with the gut microbiota through the administration of probiotics, prebiotics, and postbiotics. In addition to these innovative approaches, we address the recent discovery of new targets for drugs long in use in clinical practice. Angiotensin II receptor antagonists, NF-ĸB inhibitors, thiazide diuretics, and antimetabolic drugs can reduce renal macrophage infiltration and slow down the progression of renal disease by mechanisms independent of those usually attributed to these compounds. Allopurinol, an inhibitor of uric acid production, has been shown to decrease renal inflammation by limiting activation of the NLRP3 inflammasome. So far, these protective effects have been shown in experimental studies only. Clinical studies will establish whether these novel strategies can be incorporated into the arsenal of treatments intended to prevent the progression of human disease.

Contribution of Resident Memory CD8+ T Cells to Protective Immunity Against Respiratory Syncytial Virus and Their Impact on Vaccine Design

Worldwide, human respiratory syncytial virus (RSV) is the most common etiological agent for acute lower respiratory tract infections (ALRI). RSV-ALRI is the major cause of hospital admissions in young children, and it can cause in-hospital deaths in children younger than six months old. Therefore, RSV remains one of the pathogens deemed most important for the generation of a vaccine. On the other hand, the effectiveness of a vaccine depends on the development of immunological memory against the pathogenic agent of interest. This memory is achieved by long-lived memory T cells, based on the establishment of an effective immune response to viral infections when subsequent exposures to the pathogen take place. Memory T cells can be classified into three subsets according to their expression of lymphoid homing receptors: central memory cells (T_CM), effector memory cells (T_EM) and resident memory T cells (T_RM). The latter subset consists of cells that are permanently found in non-lymphoid tissues and are capable of recognizing antigens and mounting an effective immune response at those sites. T_RM cells activate both innate and adaptive immune responses, thus establishing a robust and rapid response characterized by the production of large amounts of effector molecules. T_RM cells can also recognize antigenically unrelated pathogens and trigger an innate-like alarm with the recruitment of other immune cells. It is noteworthy that this rapid and effective immune response induced by T_RM cells make these cells an interesting aim in the design of vaccination strategies in order to establish T_RM cell populations to prevent respiratory infectious diseases. Here, we discuss the biogenesis of T_RM cells, their contribution to the resolution of respiratory viral infections and the induction of T_RM cells, which should be considered for the rational design of new vaccines against RSV.

FLT3/FLT3L-mediated CD103+ dendritic cells alleviates hepatic ischemia-reperfusion injury in mice via activation of treg cells

BACKGROUND

This study was conducted to investigate the protective effect of Fms-like tyrosine kinase 3 (FLT3)/FLT3 ligand (FLT3L)-dependent CD103⁺ dendritic cells (DCs) on hepatic ischemia-reperfusion injury (IRI).

METHODS

A mouse model of hepatic IRI and cellular model following hypoxia-reperfusion (H/R) treatment were established. Peripheral blood and liver tissues were obtained and analyzed by flow cytometer in terms of percentage of CD103⁺DCs and regulatory T (Treg) cells. Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) were determined to assess liver function. Moreover, pro-inflammatory cytokines levels including tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6 were measured using enzyme-linked immunosorbent assay (ELISA). The histological morphology of liver tissues was examined with hematoxylin and eosin (HE) staining. The apoptosis was detected by terminal deoxynucleotidyl transferase (TdT) dUTP Nick End Labeling (TUNEL) assay. Treg-associated cytokines transforming growth factor (TGF)-β and IL-10 expressions were measured using quantitative real time polymerase chain reaction (qRT-PCR).

RESULTS

CD103⁺ DCs were significantly decreased in peripheral blood and liver tissues of mouse model of hepatic IRI. In vivo experiments indicated that CD103⁺ DCs infusion ameliorated IRI-induced liver damage and Treg inhibition. Further investigations demonstrated that FLT3/FLT3L-dependent CD103⁺ DCs suppressed hepatocyte apoptosis via activation of Treg cells in vitro.

CONCLUSION

FLT3/FLT3L-induced CD103⁺ DCs alleviated hepatic IRI through activating Treg cells.

Lymphangiogenesis in kidney and lymph node mediates renal inflammation and fibrosis

Lymphangiogenesis is associated with chronic kidney disease (CKD) and occurs following kidney transplant. Here, we demonstrate that expanding lymphatic vessels (LVs) in kidneys and corresponding renal draining lymph nodes (RDLNs) play critical roles in promoting intrarenal inflammation and fibrosis following renal injury. Our studies show that lymphangiogenesis in the kidney and RDLN is driven by proliferation of preexisting lymphatic endothelium expressing the essential C-C chemokine ligand 21 (CCL21). New injury-induced LVs also express CCL21, stimulating recruitment of more CCR7⁺ dendritic cells (DCs) and lymphocytes into both RDLNs and spleen, resulting in a systemic lymphocyte expansion. Injury-induced intrarenal inflammation and fibrosis could be attenuated by blocking the recruitment of CCR7⁺ cells into RDLN and spleen or inhibiting lymphangiogenesis. Elucidating the role of lymphangiogenesis in promoting intrarenal inflammation and fibrosis provides a key insight that can facilitate the development of novel therapeutic strategies to prevent progression of CKD-associated fibrosis.

Composite tissue allotransplantation: opportunities and challenges

Vascularized composite allotransplants (VCAs) have unique properties because of diverse tissue components transplanted en mass as a single unit. In addition to surgery, this type of transplant also faces enormous immunological challenges that demand a detailed analysis of all aspects of alloimmune responses, organ preservation, and injury, as well as the immunogenicity of various tissues within the VCA grafts to further improve graft and patient outcomes. Moreover, the side effects of long-term immunosuppression for VCA patients need to be carefully balanced with the potential benefit of a non-life-saving procedure. In this review article, we provide a comprehensive update on limb and face transplantation, with a specific emphasis on the alloimmune responses to VCA, established and novel immunosuppressive treatments, and patient outcomes.

Does tubulitis without interstitial inflammation represent borderline acute T cell mediated rejection?

Tubulitis without interstitial inflammation (Banff i0), termed "isolated tubulitis" (ISO-T), has been controversially included within the Banff "borderline" category of acute T cell mediated rejection (TCMR). This single-center, retrospective, observational study of 2055 consecutive biopsies from 775 recipients, determined the clinical significance of ISO-T. ISO-T prevalence was 19.1%, comprising mild tubulitis (i0t1) in 97.2%. Independent clinical predictors of tubulitis were HLA mismatch, prior TCMR and antibody-mediated rejection, pulse corticosteroids, and BKVAN (P = .006 to P < .001 by multivariable analysis). Histological associations of tubulitis included interstitial inflammation, peritubular capillaritis, tubular atrophy, and SV40T (P = .005 to <.001). The dominant pathological diagnoses in ISO-T (n = 393) were interstitial fibrosis/tubular atrophy (IF/TA, 44.5%) or normal/minimal (31.8%). Subanalysis of ISO-T from indication biopsies (n = 107) found acute tubular injury (37.4%), IF/TA (28.0%), normal/minimal (12.1%), acute rejection (9.3%, vascular or antibody), chronic-active TCMR (2.8%), and BKVAN (5.6%). Allograft function of ISO-T frequently improved, affected by early biopsy timing and underlying disease diagnosis. Subsequent histology of 1197 ISO-T biopsy-pairs was generally benign. The 1- and 5-year death-censored graft survivals of ISO-T were 98.8% and 92.7%. In summary, tubulitis without inflammation does not represent borderline TCMR. We suggest its removal from the borderline category, and reinstatement of i1 as the diagnostic threshold.

CCL20 blockade increases the severity of nephrotoxic folic acid-induced acute kidney injury

The chemokine CCL20 activates the CCR6 receptor and has been implicated in the pathogenesis of glomerular injury. However, it is unknown whether it contributes to acute kidney injury (AKI). We identified CCL20 as upregulated in a systems biology strategy combining transcriptomics of kidney tissue from experimental toxic folic acid-induced AKI and from stressed cultured tubular cells and have explored the expression and function of CCL20 in experimental and clinical AKI. CCL20 upregulation was confirmed in three models of kidney injury induced by a folic acid overdose, cisplatin or unilateral ureteral obstruction. In injured kidneys, CCL20 was expressed by tubular, endothelial, and interstitial cells, and was also upregulated in human kidneys with AKI. Urinary CCL20 was increased in human AKI and was associated with severity. The function of CCL20 in nephrotoxic folic acid-induced AKI was assessed by using neutralising anti-CCL20 antibodies or CCR6-deficient mice. CCL20/CCR6 targeting increased the severity of kidney failure and mortality. This was associated with more severe histological injury, nephrocalcinosis, capillary rarefaction, and fibrosis, as well as higher expression of tubular injury-associated genes. Surprisingly, mice with CCL20 blockade had a lower tubular proliferative response and a higher number of cells in the G2/M phase, suggesting impaired repair mechanisms. This may be related to a lower influx of Tregs, despite a milder inflammatory response in terms of chemokine expression and infiltration by IL-17⁺ cells and neutrophils. In conclusion, CCL20 has a nephroprotective role during AKI, both by decreasing tissue injury and by facilitating repair. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Parabiosis reveals leukocyte dynamics in the kidney

The immune cellular compartment of the kidney is involved in organ development and homeostasis, as well as in many pathological conditions. Little is known about the mechanisms that drive intrarenal immune responses in the presence of renal tubular and interstitial cell death. However, it is known that tissue-resident leukocytes have the potential to have distinct roles compared with circulating cells. We used a parabiosis model in C57BL/6 CD45 congenic and green fluorescent protein transgenic mice to better understand the dynamics of immune cells in the kidney. We found F4/80^Hi intrarenal macrophages exhibit minimal exchange with the peripheral circulation in two models of parabiosis, whether mice were attached for 4 or 16 weeks. Other intrarenal inflammatory cells demonstrate near total exchange with the circulating immune cell pool in healthy kidneys, indicating that innate and adaptive immune cells extensively traffic through the kidney interstitium during normal physiology. Neutrophils, dendritic cells, F4/80^Low macrophages, T cells, B cells, and NK cells are renewed from the circulating immune cell pool. However, a fraction of double-negative T (CD4^- CD8^-) and NKT cells are long-lived or tissue resident. This study provides direct evidence of leukocyte sub-populations that are resident in the renal tissue, cells which demonstrate minimal to no exchange with the peripheral blood. In addition, the data demonstrate continual exchange of other sub-populations through uninflamed tissue.

Organ-specific mechanisms linking innate and adaptive antifungal immunity

Fungal infections remain a significant global health problem in humans. Fungi infect millions of people worldwide and cause from acute superficial infections to life-threatening systemic disease to chronic illnesses. Trying to decipher the complex innate and adaptive immune mechanisms that protect humans from pathogenic fungi is therefore a key research goal that may lead to immune-based therapeutic strategies and improved patient outcomes. In this review, we summarize how the cells and molecules of the innate immune system activate the adaptive immune system to elicit long-term immunity to fungi. We present current knowledge and exciting new advances in the context of organ-specific immunity, outlining the tissue-specific tropisms for the major pathogenic fungi of humans, the antifungal functions of tissue-resident myeloid cells, and the adaptive immune responses required to protect specific organs from fungal challenge.

ELABELA and an ELABELA Fragment Protect against AKI

Renal ischemia-reperfusion (I/R) injury is the most common cause of AKI, which associates with high mortality and has no effective therapy. ELABELA (ELA) is a newly identified 32-residue hormone peptide highly expressed in adult kidney. To investigate whether ELA has protective effects on renal I/R injury, we administered the mature peptide (ELA32) or the 11-residue furin-cleaved fragment (ELA11) to hypoxia-reperfusion (H/R)-injured or adriamycin-treated renal tubular cells in vitro ELA32 and ELA11 significantly inhibited the elevation of the DNA damage response, apoptosis, and inflammation in H/R-injured renal tubular cells and suppressed adriamycin-induced DNA damage response. Similarly, overexpression of ELA32 or ELA11 significantly inhibited H/R-induced cell death, DNA damage response, and inflammation. Notably, treatment of mice with ELA32 or ELA11 but not an ELA11 mutant with a cysteine to alanine substitution at the N terminus (AE11C) inhibited I/R injury-induced renal fibrosis, inflammation, apoptosis, and the DNA damage response and markedly reduced the renal tubular lesions and renal dysfunction. Together, our results suggest that ELA32 and ELA11 may be therapeutic candidates for treating AKI.

Mononuclear phagocyte subpopulations in the mouse kidney

Mononuclear phagocytes are the most common cells in the kidney associated with immunity and inflammation. Although the presence of these cells in the kidney has been known for decades, the study of mononuclear phagocytes in the context of kidney function and dysfunction is still at an early stage. The purpose of this review is to summarize the present knowledge regarding classification of these cells in the mouse kidney and to identify relevant questions that would further advance the field and potentially lead to new opportunities for treatment of acute kidney injury and other kidney diseases.

Liraglutide Reduces Both Atherosclerosis and Kidney Inflammation in Moderately Uremic LDLr-/- Mice

Chronic kidney disease (CKD) leads to uremia. CKD is characterized by a gradual increase in kidney fibrosis and loss of kidney function, which is associated with a progressive increase in risk of atherosclerosis and cardiovascular death. To prevent progression of both kidney fibrosis and atherosclerosis in uremic settings, insight into new treatment options with effects on both parameters is warranted. The GLP-1 analogue liraglutide improves glucose homeostasis, and is approved for treatment of type 2 diabetes. Animal studies suggest that GLP-1 also dampens inflammation and atherosclerosis. Our aim was to examine effects of liraglutide on kidney fibrosis and atherosclerosis in a mouse model of moderate uremia (5/6 nephrectomy (NX)). Uremic (n = 29) and sham-operated (n = 14) atherosclerosis-prone low density lipoprotein receptor knockout mice were treated with liraglutide (1000 μg/kg, s.c. once daily) or vehicle for 13 weeks. As expected, uremia increased aortic atherosclerosis. In the remnant kidneys from NX mice, flow cytometry revealed an increase in the number of monocyte-like cells (CD68⁺F4/80^-), CD4⁺, and CD8⁺ T-cells, suggesting that moderate uremia induced kidney inflammation. Furthermore, markers of fibrosis (i.e. Col1a1 and Col3a1) were upregulated, and histological examinations showed increased glomerular diameter in NX mice. Importantly, liraglutide treatment attenuated atherosclerosis (~40%, p < 0.05) and reduced kidney inflammation in NX mice. There was no effect of liraglutide on expression of fibrosis markers and/or kidney histology. This study suggests that liraglutide has beneficial effects in a mouse model of moderate uremia by reducing atherosclerosis and attenuating kidney inflammation.