Functional Contribution and Targeted Migration of Group-2 Innate Lymphoid Cells in Inflammatory Lung Diseases: Being at the Right Place at the Right Time

During the last decade, group-2 innate lymphoid cells (ILC2s) have been discovered and successfully established as crucial mediators of lung allergy, airway inflammation and fibrosis, thus affecting the pathogenesis and clinical course of many respiratory diseases, like for instance asthma, cystic fibrosis and chronic rhinosinusitis. As an important regulatory component in this context, the local pulmonary milieu at inflammatory tissue sites does not only determine the activation status of lung-infiltrating ILC2s, but also influences their motility and migratory behavior. In general, many data collected in recent murine and human studies argued against the former concept of a very strict tissue residency of innate lymphoid cells (ILCs) and instead pointed to a context-dependent homing capacity of peripheral blood ILC precursors and the inflammation-dependent capacity of specific ILC subsets for interorgan trafficking. In this review article, we provide a comprehensive overview of the so far described molecular mechanisms underlying the pulmonary migration of ILC2s and thereby the numeric regulation of local ILC2 pools at inflamed or fibrotic pulmonary tissue sites and discuss their potential to serve as innovative therapeutic targets in the treatment of inflammatory lung diseases.

Comparative Transcriptomics of IBD Patients Indicates Induction of Type 2 Immunity Irrespective of the Disease Ideotype

Inflammatory cytokines initiate and sustain the perpetuation of processes leading to chronic inflammatory conditions such as inflammatory bowel diseases (IBD). The nature of the trigger causing an inflammatory reaction decides whether type 1, type 17, or type 2 immune responses, typically characterized by the respective T- helper cell subsets, come into effect. In the intestine, Type 2 responses have been linked with mucosal healing and resolution upon an immune challenge involving parasitic infections. However, type 2 cytokines are frequently elevated in certain types of IBD in particular ulcerative colitis (UC) leading to the assumption that Th2 cells might critically support the pathogenesis of UC raising the question of whether such elevated type 2 responses in IBD are beneficial or detrimental. In line with this, previous studies showed that suppression of IL-13 and other type 2 related molecules in murine models could improve the outcomes of intestinal inflammation. However, therapeutic attempts of neutralizing IL-13 in ulcerative colitis patients have yielded no benefits. Thus, a better understanding of the role of type 2 cytokines in regulating intestinal inflammation is required. Here, we took a comparative transcriptomic approach to address how Th2 responses evolve in different mouse models of colitis and human IBD datasets. Our data show that type 2 immune-related transcripts are induced in the inflamed gut of IBD patients in both Crohn's disease and UC and across widely used mouse models of IBD. Collectively our data implicate that the presence of a type 2 signature rather defines a distinct state of intestinal inflammation than a disease-specific pathomechanism.

Innate Lymphoid Cells as Regulators of Epithelial Integrity: Therapeutic Implications for Inflammatory Bowel Diseases

The occurrence of epithelial defects in the gut relevantly contributes to the pathogenesis of inflammatory bowel diseases (IBD), whereby the impairment of intestinal epithelial barrier integrity seems to represent a primary trigger as well as a disease amplifying consequence of the chronic inflammatory process. Besides epithelial cell intrinsic factors, accumulated and overwhelmingly activated immune cells and their secretome have been identified as critical modulators of the pathologically altered intestinal epithelial cell (IEC) function in IBD. In this context, over the last 10 years increasing levels of attention have been paid to the group of innate lymphoid cells (ILCs). This is in particular due to a preferential location of these rather newly described innate immune cells in close proximity to mucosal barriers, their profound capacity to secrete effector cytokines and their numerical and functional alteration under chronic inflammatory conditions. Aiming on a comprehensive and updated summary of our current understanding of the bidirectional mucosal crosstalk between ILCs and IECs, this review article will in particular focus on the potential capacity of gut infiltrating type-1, type-2, and type-3 helper ILCs (ILC1s, ILC2s, and ILC3s, respectively) to impact on the survival, differentiation, and barrier function of IECs. Based on data acquired in IBD patients or in experimental models of colitis, we will discuss whether the different ILC subgroups could serve as potential therapeutic targets for maintenance of epithelial integrity and/or mucosal healing in IBD.

CCR8 Signaling via CCL1 Regulates Responses of Intestinal IFN-γ Producing Innate Lymphoid CelIs and Protects From Experimental Colitis

A diverse spectrum of immune cells populates the intestinal mucosa reflecting the continuous stimulation by luminal antigens. In lesions of patients with inflammatory bowel disease, an aberrant inflammatory process is characterized by a very prominent infiltrate of activated immune cells producing cytokines and chemokines. These mediators perpetuate intestinal inflammation or may contribute to mucosal protection depending on the cellular context. In order to further characterize this complex immune cell network in intestinal inflammation, we investigated the contribution of the chemokine receptor CCR8 to development of colitis using a mouse model of experimental inflammation. We found that CCR8^-/- mice compared to wildtype controls developed strong weight loss accompanied by increased histological and endoscopic signs of mucosal damage. Further experiments revealed that this gut protective function of CCR8 seems to be selectively mediated by the chemotactic ligand CCL1, which was particularly produced by intestinal macrophages during colitis. Moreover, we newly identified CCR8 expression on a subgroup of intestinal innate lymphoid cells producing IFN-γ and linked a functional CCL1/CCR8 axis with their abundance in the gut. Our data therefore suggest that this pathway supports tissue-specific ILC functions important for intestinal homeostasis. Modulation of this regulatory circuit may represent a new strategy to treat inflammatory bowel disease in humans.

Th17 Cell-Mediated Colitis Is Positively Regulated by Interferon Regulatory Factor 4 in a T Cell-Extrinsic Manner

Inflammatory bowel diseases (IBDs) are characterized by chronic, inflammatory gastrointestinal lesions and often require life-long treatment with immunosuppressants and repetitive surgical interventions. Despite progress in respect to the characterization of molecular mechanisms e.g. exerted by TNF-alpha, currently clinically approved therapeutics fail to provide long-term disease control for most patients. The transcription factor interferon regulatory factor 4 (IRF4) has been shown to play important developmental as well as functional roles within multiple immune cells. In the context of colitis, a T cell-intrinsic role of IRF4 in driving immune-mediated gut pathology is established. Here, we conversely addressed the impact of IRF4 inactivation in non-T cells on T cell driven colitis in vivo. Employing the CD4+CD25- naïve T cell transfer model, we found that T cells fail to elicit colitis in IRF4-deficient compared to IRF4-proficient Rag1-/- mice. Reduced colitis activity in the absence of IRF4 was accompanied by hampered T cell expansion both within the mesenteric lymph node (MLN) and colonic lamina propria (cLP). Furthermore, the influx of various myeloids, presumably inflammation-promoting cells was abrogated overall leading to a less disrupted intestinal barrier. Mechanistically, gene profiling experiments revealed a Th17 response dominated molecular expression signature in colon tissues of IRF4-proficient, colitic Rag1-/- but not in colitis-protected Rag1-/-Irf4-/- mice. Colitis mitigation in Rag1-/-Irf4-/- T cell recipients resulted in reduced frequencies and absolute numbers of IL-17a-producing T cell subsets in MLN and cLP possibly due to a regulation of conventional dendritic cell subset 2 (cDC2) known to impact Th17 differentiation. Together, extending the T cell-intrinsic role for IRF4 in the context of Th17 cell driven colitis, the provided data demonstrate a Th17-inducing and thereby colitis-promoting role of IRF4 through a T cell-extrinsic mechanism highlighting IRF4 as a putative molecular master switch among transcriptional regulators driving immune-mediated intestinal inflammation through both T cell-intrinsic and T cell-extrinsic mechanisms. Future studies need to further dissect IRF4 controlled pathways within distinct IRF4-expressing myeloid cell types, especially cDC2s, to elucidate the precise mechanisms accounting for hampered Th17 formation and, according to our data, the predominant mechanism of colitis protection in Rag1-/-Irf4-/- T cell receiving mice.

The Regulation of Intestinal Inflammation and Cancer Development by Type 2 Immune Responses

The gut is among the most complex organs of the human body. It has to exert several functions including food and water absorption while setting up an efficient barrier to the outside world. Dysfunction of the gut can be life-threatening. Diseases of the gastrointestinal tract such as inflammatory bowel disease, infections, or colorectal cancer, therefore, pose substantial challenges to clinical care. The intestinal epithelium plays an important role in intestinal disease development. It not only establishes an important barrier against the gut lumen but also constantly signals information about the gut lumen and its composition to immune cells in the bowel wall. Such signaling across the epithelial barrier also occurs in the other direction. Intestinal epithelial cells respond to cytokines and other mediators of immune cells in the lamina propria and shape the microbial community within the gut by producing various antimicrobial peptides. Thus, the epithelium can be considered as an interpreter between the microbiota and the mucosal immune system, safeguarding and moderating communication to the benefit of the host. Type 2 immune responses play important roles in immune-epithelial communication. They contribute to gut tissue homeostasis and protect the host against infections with helminths. However, they are also involved in pathogenic pathways in inflammatory bowel disease and colorectal cancer. The current review provides an overview of current concepts regarding type 2 immune responses in intestinal physiology and pathophysiology.

Arginase impedes the resolution of colitis by altering the microbiome and metabolome

Arginase 1 (Arg1), which converts l-arginine into ornithine and urea, exerts pleiotropic immunoregulatory effects. However, the function of Arg1 in inflammatory bowel disease (IBD) remains poorly characterized. Here, we found that Arg1 expression correlated with the degree of inflammation in intestinal tissues from IBD patients. In mice, Arg1 was upregulated in an IL-4/IL-13- and intestinal microbiota-dependent manner. Tie2-Cre Arg1fl/fl mice lacking Arg1 in hematopoietic and endothelial cells recovered faster from colitis than Arg1-expressing (Arg1fl/fl) littermates. This correlated with decreased vessel density, compositional changes in intestinal microbiota, diminished infiltration by myeloid cells, and an accumulation of intraluminal polyamines that promote epithelial healing. The proresolving effect of Arg1 deletion was reduced by an l-arginine-free diet, but rescued by simultaneous deletion of other l-arginine-metabolizing enzymes, such as Arg2 or Nos2, demonstrating that protection from colitis requires l-arginine. Fecal microbiota transfers from Tie2-Cre Arg1fl/fl mice into WT recipients ameliorated intestinal inflammation, while transfers from WT littermates into Arg1-deficient mice prevented an advanced recovery from colitis. Thus, an increased availability of l-arginine as well as altered intestinal microbiota and metabolic products accounts for the accelerated resolution from colitis in the absence of Arg1. Consequently, l-arginine metabolism may serve as a target for clinical intervention in IBD patients.

Finding Possible Weakness in the Runoff Simulation Experiments to Assess Rill Erosion Changes without Non-Intermittent Surveying Capabilities

The Terrestrial Photogrammetry Scanner (TEPHOS) offers the possibility to precisely monitor linear erosion features using the Structure from Motion (SfM) technique. This is a static, multi-camera array and dynamically moves the digital videoframe camera designed to obtain 3-D models of rills before and after the runoff experiments. The main goals were to (1) obtain better insight into the rills; (2) reduce the technical gaps generated during the runoff experiments using only one camera; (3) enable the visual location of eroded, transported and accumulated material. In this study, we obtained a mean error for all pictures reaching up to 0.00433 pixels and every single one of them was under 0.15 pixel. So, we obtained an error of about 1/10th of the maximum possible resolution. A conservative value for the overall accuracy was one pixel, which means that, in our case, the accuracy was 0.0625 mm. The point density, in our example, reached 29,484,888 pts/m². It became possible to get a glimpse of the hotspots of sidewall failure and rill-bed incision. We conclude that the combination of both approaches—rill experiment and 3D models—will make easy under laboratory conditions to describe the soil erosion processes accurately in a mathematical–physical way.

Effect of Regional Citrate Anticoagulation vs Systemic Heparin Anticoagulation During Continuous Kidney Replacement Therapy on Dialysis Filter Life Span and Mortality Among Critically Ill Patients With Acute Kidney Injury: A Randomized Clinical Trial

IMPORTANCE

Although current guidelines suggest the use of regional citrate anticoagulation (which involves the addition of a citrate solution to the blood before the filter of the extracorporeal dialysis circuit) as first-line treatment for continuous kidney replacement therapy in critically ill patients, the evidence for this recommendation is based on few clinical trials and meta-analyses.

OBJECTIVE

To determine the effect of regional citrate anticoagulation, compared with systemic heparin anticoagulation, on filter life span and mortality.

DESIGN, SETTING, AND PARTICIPANTS

A parallel-group, randomized multicenter clinical trial in 26 centers across Germany was conducted between March 2016 and December 2018 (final date of follow-up, January 21, 2020). The trial was terminated early after 596 critically ill patients with severe acute kidney injury or clinical indications for initiation of kidney replacement therapy had been enrolled.

INTERVENTIONS

Patients were randomized to receive either regional citrate anticoagulation (n = 300), which consisted of a target ionized calcium level of 1.0 to 1.40 mg/dL, or systemic heparin anticoagulation (n = 296), which consisted of a target activated partial thromboplastin time of 45 to 60 seconds, for continuous kidney replacement therapy.

MAIN OUTCOMES AND MEASURES

Coprimary outcomes were filter life span and 90-day mortality. Secondary end points included bleeding complications and new infections.

RESULTS

Among 638 patients randomized, 596 (93.4%) (mean age, 67.5 years; 183 [30.7%] women) completed the trial. In the regional citrate group vs systemic heparin group, median filter life span was 47 hours (interquartile range [IQR], 19-70 hours) vs 26 hours (IQR, 12-51 hours) (difference, 15 hours [95% CI, 11 to 20 hours]; P < .001). Ninety-day all-cause mortality occurred in 150 of 300 patients vs 156 of 296 patients (Kaplan-Meier estimator percentages, 51.2% vs 53.6%; unadjusted difference, -2.4% [95% CI, -10.5% to 5.8%]; unadjusted hazard ratio, 0.91 [95% CI, 0.72 to 1.13]; unadjusted P = .38; adjusted difference, -6.1% [95% CI, -12.6% to 0.4%]; primary adjusted hazard ratio, 0.79 [95% CI, 0.63 to 1.004]; primary adjusted P = .054). Of 38 prespecified secondary end points, 34 showed no significant difference. Compared with the systemic heparin group, the regional citrate group had significantly fewer bleeding complications (15/300 [5.1%] vs 49/296 [16.9%]; difference, -11.8% [95% CI, -16.8% to -6.8%]; P < .001) and significantly more new infections (204/300 [68.0%] vs 164/296 [55.4%]; difference, 12.6% [95% CI, 4.9% to 20.3%]; P = .002).

CONCLUSIONS AND RELEVANCE

Among critically ill patients with acute kidney injury receiving continuous kidney replacement therapy, anticoagulation with regional citrate, compared with systemic heparin anticoagulation, resulted in significantly longer filter life span. The trial was terminated early and was therefore underpowered to reach conclusions about the effect of anticoagulation strategy on mortality.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02669589.

An in vivo gene delivery approach for the isolation of reasonable numbers of type 2 innate lymphoid cells

Group 2 innate lymphoid cells (ILC2s) are a recently recognized subset of innate lymphocytes with crucial role in mucosal immunity and tissue homeostasis. Over the past decade, substantial advances in our understanding of ILC2 biology have established them as an essential element in innate and adaptive immunity. However, their relatively low abundance and laborious purification from mucosal tissues make their study difficult. Moreover, due to a lack of an ILC2-specific Cre mouse-line, adoptive transfer of ILC2s into ILC-deficient hosts is inevitable. Herein we describe an in-depth protocol for the induction, isolation, and expansion of murine ILC2s. By combining an in vivo gene delivery approach to boost ILC2 numbers and a cell culture strategy to expand isolated cells, large quantities of highly pure ILC2s can be obtained. The isolated cells maintain their phenotype and can be used for subsequent cell transfer or in vitro studies. In comparison to previous protocols, this approach is cost-effective and efficient with potential yield of more than 20 million ILC2s isolated per mouse.

• Group 2 innate lymphoid cells (ILC2s) are extensively studied in mouse models and humans in recent years.

• Low abundance of ILC2s and current lack of specific ILC2 knockout mice makes in vivo research challenging.

• This method allows high and pure ILC2 numbers for in vitro or adoptive in vivo transfer experiments.

Participation of the intestinal microbiota in the mechanism of beneficial effect of treatment with synbiotic Syngut on experimental colitis under stress conditions

Gut-brain axis plays a central role in the regulation of stress related diseases such as irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD). It is increasingly recognized that stress modulates gut microbiota community structure and activity and represents an important causal factor in dysbiosis. This study was designed to determine the effect of daily treatment with synbiotic (Syngut) containing inulin, Lactobacillus acidophilus, Bifidobacterium lactis W51, Lactobacillus plantarum W21 and Lactococcus lactis applied i.g. at a dose of 50 mg/kg i.g. on the colonic damage and colonic mucosal blood flow in rats with experimentally induced TNBS-colitis that were additionally exposed or not to acute stress (episodes of cold restraint stress every other day before colitis induction). Control rats received daily treatment with vehicle (saline, i.g.) or mesalazine (50 mg/kg-d i.g.), the standard drug recommended in therapy of IBD. At the termination of TNBS colitis, the histologic evaluation of colonic mucosa, mucosal malonyldialdehyde (MDA) level and plasma concentrations of proinflammatory cytokines (TNF-α, IL-1β) and adipokine adiponectin were assessed. the samples of colonic mucosa not involving colonic lesions and surrounding the flared mucosa were excised for the determination of mRNA expression for proinflammatory biomarkers TNF-α, IL-1β, IL-10 and COX-2 as well as antioxidazing factors SOD-1 and SOD-2. Finally, the gut microbial profiles were analyzed by 16S rRNA sequencing at phylum, family and genus level. Episodes of cold stress significantly aggravated the course of TNBS colitis, and significantly increased the release of proinflammatory cytokines as well as the significant increase in the MDA concentration has been observed as compared with non-stressed TNBS rats. These changes were followed by the significant fall in the CBF and plasma adiponectin levels and by the overexpression of mRNA of proinflammatory biomarkers. Synbiotic treatment with Syngut significantly reduced the area of colonic lesions observed macroscopically and microscopically in rats with TNBS colitis with or without exposure to cold stress, significantly increased the CBF, normalized plasma adiponectin levels and significantly attenuated the release and colonic expression of proinflammatory cytokines and biomarkers. the analysis of the gut microbiota showed a significant reduction of microbial diversity (Shannon index) in rats with TNBS colitis with or without exposure to stress. The therapy with Syngut failed to significantly affect the alpha diversity. At the phylum level, the significant rise in Proteobacteria has been observed in stressed rats with TNBS colitis and this effects was attenuated by treatment with Syngut. At family level, TNBS colitis alone or in combination with stress led to a significant decrease of SCFA producing bacterial taxa such as Ruminococaceae and Lachnospiraceae and Syngut counteracted this effect. We conclude that: 1) cold stress exacerbates the gastrointestinal inflammation in experimental colitis; 2) the synbiotic therapy with Syngut ameliorates the gut inflammation in rats with TNBS colitis combined with cold stress; 3) the beneficial effect of Syngut is accompanied by increase of anti-inflammatory taxa such as Ruminococaceae and Lachnospiraceae, and 4) the modulation of gut microbiota with Syngut alleviates stress-related intestinal inflammation suggesting a potential usefulness of synbiotic therapy in intestinal disorders accompanied by stress in patients with IBD.

Changes in Gastrointestinal Microbiome Composition in PD: A Pivotal Role of Covariates

Altered gut microbiota may trigger or accelerate alpha-synuclein aggregation in the enteric nervous system in Parkinson's disease (PD). While several previous studies observed gut microbiota alterations in PD, findings like diversity indices, and altered bacterial taxa itself show a considerable heterogeneity across studies. We recruited 179 participants, of whom 101 fulfilled stringent inclusion criteria. Subsequently, the composition of the gut microbiota in 71 PD patients and 30 healthy controls was analyzed, sequencing V3–V4 regions of the bacterial 16S ribosomal RNA gene in fecal samples. Our goal was (1) to evaluate whether gut microbiota are altered in a southern German PD cohort, (2) to delineate the influence of disease duration, stage, and motor impairment, and (3) to investigate the influence of PD associated covariates like constipation and coffee consumption. Aiming to control for a large variety of covariates, strict inclusion criteria were applied. Finally, propensity score matching was performed to correct for, and to delineate the effect of remaining covariates (non-motor symptom (NMS) burden, constipation, and coffee consumption) on microbiota composition. Prior to matching altered abundances of distinct bacterial classes, orders, families, and genera were observed. Both, disease duration, and stage influenced microbiome composition. Interestingly, levodopa equivalent dose influenced the correlation of taxa with disease duration, while motor impairment did not. Applying different statistical tests, and after propensity score matching to control for NMS burden, constipation and coffee consumption, Faecalibacterium and Ruminococcus were most consistently reduced in PD compared to controls. Taken together, similar to previous studies, alterations of several taxa were observed in PD. Yet, further controlling for PD associated covariates such as constipation and coffee consumption revealed a pivotal role of these covariates. Our data highlight the impact of these PD associated covariates on microbiota composition in PD. This suggests that altered microbiota may mediate the protective effect of i.e., coffee consumption and the negative effect of constipation in PD.

Neutrophil Extracellular Traps Promote the Development and Growth of Human Salivary Stones

Salivary gland stones, or sialoliths, are the most common cause of the obstruction of salivary glands. The mechanism behind the formation of sialoliths has been elusive. Symptomatic sialolithiasis has a prevalence of 0.45% in the general population, is characterized by recurrent painful periprandial swelling of the affected gland, and often results in sialadenitis with the need for surgical intervention. Here, we show by the use of immunohistochemistry, immunofluorescence, computed tomography (CT) scans and reconstructions, special dye techniques, bacterial genotyping, and enzyme activity analyses that neutrophil extracellular traps (NETs) initiate the formation and growth of sialoliths in humans. The deposition of neutrophil granulocyte extracellular DNA around small crystals results in the dense aggregation of the latter, and the subsequent mineralization creates alternating layers of dense mineral, which are predominantly calcium salt deposits and DNA. The further agglomeration and appositional growth of these structures promotes the development of macroscopic sialoliths that finally occlude the efferent ducts of the salivary glands, causing clinical symptoms and salivary gland dysfunction. These findings provide an entirely novel insight into the mechanism of sialolithogenesis, in which an immune system-mediated response essentially participates in the physicochemical process of concrement formation and growth.

Microbiome Patterns in Matched Bile, Duodenal, Pancreatic Tumor Tissue, Drainage, and Stool Samples: Association with Preoperative Stenting and Postoperative Pancreatic Fistula Development

Postoperative complications after pancreatic surgery are still a significant problem in clinical practice. The aim of this study was to characterize and compare the microbiomes of different body compartments (bile duct, duodenal mucosa, pancreatic tumor lesion, postoperative drainage fluid, and stool samples; preoperative and postoperative) in patients undergoing pancreatic surgery for suspected pancreatic cancer, and their association with relevant clinical factors (stent placement, pancreatic fistula, and gland texture). For this, solid (duodenal mucosa, pancreatic tumor tissue, stool) and liquid (bile, drainage fluid) biopsy samples of 10 patients were analyzed using 16s rRNA gene next-generation sequencing. Our analysis revealed: (i) a distinct microbiome in the different compartments, (ii) markedly higher abundance of Enterococcus in patients undergoing preoperative stent placement in the common bile duct, (iii) significant differences in the beta diversity between patients who developed a postoperative pancreatic fistula (POPF B/C), (iv) patients with POPF B/C were more likely to have bacteria belonging to the genus Enterococcus, and (v) differences in microbiome composition with regard to the pancreatic gland texture. The structure of the microbiome is distinctive in different compartments, and can be associated with the development of a postoperative pancreatic fistula.

Mycobacterial Cord Factor Reprograms the Macrophage Response to IFN-γ towards Enhanced Inflammation yet Impaired Antigen Presentation and Expression of GBP1

Mycobacteria survive in macrophages despite triggering pattern recognition receptors and T cell-derived IFN-γ production. Mycobacterial cord factor trehalose-6,6-dimycolate (TDM) binds the C-type lectin receptor MINCLE and induces inflammatory gene expression. However, the impact of TDM on IFN-γ-induced macrophage activation is not known. In this study, we have investigated the cross-regulation of the mouse macrophage transcriptome by IFN-γ and by TDM or its synthetic analogue trehalose-6,6-dibehenate (TDB). As expected, IFN-γ induced genes involved in Ag presentation and antimicrobial defense. Transcriptional programs induced by TDM and TDB were highly similar but clearly distinct from the response to IFN-γ. The glycolipids enhanced expression of a subset of IFN-γ-induced genes associated with inflammation. In contrast, TDM/TDB exerted delayed inhibition of IFN-γ-induced genes, including pattern recognition receptors, MHC class II genes, and IFN-γ-induced GTPases, with antimicrobial function. TDM downregulated MHC class II cell surface expression and impaired T cell activation by peptide-pulsed macrophages. Inhibition of the IFN-γ-induced GTPase GBP1 occurred at the level of transcription by a partially MINCLE-dependent mechanism that may target IRF1 activity. Although activation of STAT1 was unaltered, deletion of Socs1 relieved inhibition of GBP1 expression by TDM. Nonnuclear Socs1 was sufficient for inhibition, suggesting a noncanonical, cytoplasmic mechanism. Taken together, unbiased analysis of transcriptional reprogramming revealed a significant degree of negative regulation of IFN-γ-induced Ag presentation and antimicrobial gene expression by the mycobacterial cord factor that may contribute to mycobacterial persistence.

STAT3 activation through IL-6/IL-11 in cancer-associated fibroblasts promotes colorectal tumour development and correlates with poor prognosis

OBJECTIVE

Cancer-associated fibroblasts (CAFs) influence the tumour microenvironment and tumour growth. However, the role of CAFs in colorectal cancer (CRC) development is incompletely understood.

DESIGN

We quantified phosphorylation of STAT3 (pSTAT3) expression in CAFs of human colon cancer tissue using a tissue microarray (TMA) of 375 patients, immunofluorescence staining and digital pathology. To investigate the functional role of CAFs in CRC, we took advantage of two murine models of colorectal neoplasia and advanced imaging technologies. In loss-of-function and gain-of-function experiments, using genetically modified mice with collagen type VI (COLVI)-specific signal transducer and activator of transcription 3 (STAT3) targeting, we evaluated STAT3 signalling in fibroblasts during colorectal tumour development. We performed a comparative gene expression profiling by whole genome RNA-sequencing of fibroblast subpopulations (COLVI+ vs COLVI-) on STAT3 activation (IL-6 vs IL-11).

RESULTS

The analysis of pSTAT3 expression in CAFs of human TMAs revealed a negative correlation of increased stromal pSTAT3 expression with the survival of colon cancer patients. In the loss-of-function and gain-of-function approach, we found a critical role of STAT3 activation in fibroblasts in driving colorectal tumourigenesis in vivo. With different imaging technologies, we detected an expansion of activated fibroblasts in colorectal neoplasias. Comparative gene expression profiling of fibroblast subpopulations on STAT3 activation revealed the regulation of transcriptional patterns associated with angiogenesis. Finally, the blockade of proangiogenic signalling significantly reduced colorectal tumour growth in mice with constitutive STAT3 activation in COLVI+ fibroblasts.

CONCLUSION

Altogether our work demonstrates a critical role of STAT3 activation in CAFs in CRC development.

Type 2 innate lymphoid cells inhibit the differentiation of osteoclasts and protect from ovariectomy-induced bone loss

While the role of T cells in the regulation of bone homeostasis is well defined, little is known about the role of innate lymphoid cells (ILCs) on bone. ILCs are innate immune cells that share cytokine expression patterns with T cells but lack the T cell receptor. In this study we show that type 2 ILCs (ILC2) potently inhibit the generation of bone resorbing osteoclasts in vitro as well as favorably influence bone homeostasis under steady state conditions in vivo using loss and gain of function models. Furthermore, adoptive transfer of ILC2 completely abrogated ovariectomy-induced bone loss by significantly down-regulating osteoclast numbers in vivo. The suppressive effects of ILC2s on osteoclasts in vitro and in vivo as well as the protection from ovariectomy-induced bone loss were linked to their expression of IL-4 and IL-13 as well as STAT6 activation on the myeloid target cell, since deletion of IL-4/IL-13 in ILC2s or STAT6 in osteoclast precursors abrogated the anti-osteoclastogenic effect of ILC2s. Taken together, these findings show that ILC2 have to be considered as potent regulators of bone homeostasis.

Wheat Consumption Aggravates Colitis in Mice via Amylase Trypsin Inhibitor-mediated Dysbiosis

BACKGROUND & AIMS

Wheat has become the world's major staple and its consumption correlates with prevalence of noncommunicable disorders such as inflammatory bowel diseases. Amylase trypsin inhibitors (ATIs), a component of wheat, activate the intestine's innate immune response via toll-like receptor 4 (TLR4). We investigated the effects of wheat and ATIs on severity of colitis and fecal microbiota in mice.

METHODS

C57BL/6 wild-type and Tlr4^-/- mice were fed wheat- or ATI-containing diets or a wheat-free (control) diet and then given dextran sodium sulfate to induce colitis; we also studied Il10^-/- mice, which develop spontaneous colitis. Changes in fecal bacteria were assessed by taxa-specific quantitative polymerase chain reaction and 16S ribosomal RNA metagenomic sequencing. Feces were collected from mice on wheat-containing, ATI-containing, control diets and transplanted to intestines of mice with and without colitis on control or on ATI-containing diets. Intestinal tissues were collected and analyzed by histology, immunohistochemistry, and flow cytometry. Bacteria with reported immunomodulatory effects were incubated with ATIs and analyzed in radial diffusion assays.

RESULTS

The wheat- or ATI-containing diets equally increased inflammation in intestinal tissues of C57BL/6 mice with colitis, compared with mice on control diets. The ATI-containing diet promoted expansion of taxa associated with development of colitis comparable to the wheat-containing diet. ATIs inhibited proliferation of specific human commensal bacteria in radial diffusion assays. Transplantation of microbiota from feces of mice fed the wheat- or ATI-containing diets to intestines of mice on control diets increased the severity of colitis in these mice. The ATI-containing diet did not increase the severity of colitis in Tlr4^-/- mice.

CONCLUSIONS

Consumption of wheat or wheat ATIs increases intestinal inflammation in mice with colitis, via TLR4, and alters their fecal microbiota. Wheat-based, ATI-containing diets therefore activate TLR4 signaling and promote intestinal dysbiosis.

Regulation of Human Innate Lymphoid Cells in the Context of Mucosal Inflammation

Since their identification as a unique cell population, innate lymphoid cells (ILCs) have revolutionized our understanding of immune responses, leaving their impact on multiple inflammatory and fibrotic pathologies without doubt. Thus, a tightly controlled regulation of local ILC numbers and their activity is of crucial importance. Even though this has been extensively studied in murine ILCs in the last few years, our knowledge of human ILCs is still lagging behind. Our review article will therefore summarize recent insights into the function of human ILCs and will particularly focus on their regulation under inflammatory conditions. The quality and intensity of ILC involvement into local immune responses at mucosal sites of the human body can potentially be modulated via three different axes: (1) activation of tissue-resident mature ILCs, (2) plasticity and local transdifferentiation of specific ILC subsets, and (3) tissue migration and accumulation of peripheral ILCs. Despite a still ongoing scientific effort in this field, already existing data on the fate of human ILCs under different pathologic conditions clearly indicate that all three of these mechanisms are of relevance for the clinical course of chronic inflammatory and autoimmune diseases and might likewise provide new target structures for future therapeutic strategies.

Interleukin-9 protects from early podocyte injury and progressive glomerulosclerosis in Adriamycin-induced nephropathy

A wide spectrum of immunological functions has been attributed to Interleukin 9 (IL-9), including effects on the survival and proliferation of immune and parenchymal cells. In recent years, emerging evidence suggests that IL-9 expression can promote tissue repair in inflammatory conditions. However, data about the involvement of IL-9 in kidney tissue protection is very limited. Here, we investigated the role of IL-9 in Adriamycin-induced nephropathy (AN), a mouse model for proteinuric chronic kidney disease. Compared to wild type mice, IL-9 knockout (Il9^-/-) mice with AN displayed accelerated development of proteinuria, aggravated glomerulosclerosis and deterioration of kidney function. At an early stage of disease, the Il9^-/- mice already displayed a higher extent of glomerular podocyte injury and loss of podocyte number compared to wild type mice. In the kidney, T cells and innate lymphoid cells produced IL-9. However, selective deficiency of IL-9 in the innate immune system in Il9^-/-Rag2^-/- mice that lack T and B cells did not alter the outcome of AN, indicating that IL-9 derived from the adaptive immune system was the major driver of tissue protection in this model. Mechanistically, we could show that podocytes expressed the IL-9 receptor in vivo and that IL-9 signaling protects podocytes from Adriamycin-induced apoptosis in vitro. Finally, in vivo treatment with IL-9 effectively protected wild type mice from glomerulosclerosis and kidney failure in the AN model. The detection of increased serum IL-9 levels in patients with primary focal and segmental glomerulosclerosis further suggests that IL-9 production is induced by glomerular injury in humans. Thus, IL-9 confers protection against experimental glomerulosclerosis, identifying the IL-9 pathway as a potential therapeutic target in proteinuric chronic kidney disease.

ILC2 Lung-Homing in Cystic Fibrosis Patients: Functional Involvement of CCR6 and Impact on Respiratory Failure

Cystic fibrosis patients suffer from a progressive, often fatal lung disease, which is based on a complex interplay between chronic infections, locally accumulating immune cells and pulmonary tissue remodeling. Although group-2 innate lymphoid cells (ILC2s) act as crucial initiators of lung inflammation, our understanding of their involvement in the pathogenesis of cystic fibrosis remains incomplete. Here we report a marked decrease of circulating CCR6⁺ ILC2s in the blood of cystic fibrosis patients, which significantly correlated with high disease severity and advanced pulmonary failure, strongly implicating increased ILC2 homing from the peripheral blood to the chronically inflamed lung tissue in cystic fibrosis patients. On a functional level, the CCR6 ligand CCL20 was identified as potent promoter of lung-directed ILC2 migration upon inflammatory conditions in vitro and in vivo using a new humanized mouse model with light-sheet fluorescence microscopic visualization of lung-accumulated human ILC2s. In the lung, blood-derived human ILC2s were able to augment local eosinophil and neutrophil accumulation and induced a marked upregulation of pulmonary type-VI collagen expression. Studies in primary human lung fibroblasts additionally revealed ILC2-derived IL-4 and IL-13 as important mediators of this type-VI collagen-inducing effect. Taken together, the here acquired results suggest that pathologically increased CCL20 levels in cystic fibrosis airways induce CCR6-mediated lung homing of circulating human ILC2s. Subsequent ILC2 activation then triggers local production of type-VI collagen and might thereby drive extracellular matrix remodeling potentially influencing pulmonary tissue destruction in cystic fibrosis patients. Thus, modulating the lung homing capacity of circulating ILC2s and their local effector functions opens new therapeutic avenues for cystic fibrosis treatment.

RELMα-expressing macrophages protect against fatal lung damage and reduce parasite burden during helminth infection

Alternatively activated macrophages (AAMs) can contribute to wound healing, regulation of glucose and fat metabolism, resolution of inflammation, and protective immunity against helminths. Their differentiation, tissue distribution, and effector functions are incompletely understood. Murine AAMs express high levels of resistin-like molecule (RELM) α, an effector protein with potent immunomodulatory functions. To visualize RELMα⁺ macrophages (MΦs) in vivo and evaluate their role in defense against helminths, we generated RELMα reporter/deleter mice. Infection with the helminth Nippostrongylus brasiliensis induced expansion of RELMα⁺ lung interstitial but not alveolar MΦs in a STAT6-dependent manner. RELMα⁺ MΦs were required for prevention of fatal lung damage during primary infection. Furthermore, protective immunity was lost upon specific deletion of RELMα⁺ MΦs during secondary infection. Thus, RELMα reporter/deleter mice reveal compartmentalization of AAMs in different tissues and demonstrate their critical role in resolution of severe lung inflammation and protection against migrating helminths.

Group 2 Innate Lymphoid Cells (ILC2) Suppress Beneficial Type 1 Immune Responses During Pulmonary Cryptococcosis

Cryptococcus neoformans is an opportunistic fungal pathogen preferentially causing disease in immunocompromised individuals such as organ-transplant-recipients, patients receiving immunosuppressive medications or, in particular, individuals suffering from HIV infection. Numerous studies clearly indicated that the control of C. neoformans infections is strongly dependent on a prototypic type 1 immune response and classical macrophage activation, whereas type 2-biased immunity and alternative activation of macrophages has been rather implicated in disease progression and detrimental outcomes. However, little is known about regulatory pathways modulating and balancing immune responses during early phases of pulmonary cryptococcosis. Here, we analyzed the role of group 2 innate lymphoid cells (ILC2s) for the control of C. neoformans infection. Using an intranasal infection model with a highly virulent C. neoformans strain, we found that ILC2 numbers were strongly increased in C. neoformans-infected lungs along with induction of a type 2 response. Mice lacking ILC2s due to conditional deficiency of the transcription factor RAR-related orphan receptor alpha (Rora) displayed a massive downregulation of features of type 2 immunity as reflected by reduced levels of the type 2 signature cytokines IL-4, IL-5, and IL-13 at 14 days post-infection. Moreover, ILC2 deficiency was accompanied with increased type 1 immunity and classical macrophage activation, while the pulmonary numbers of eosinophils and alternatively activated macrophages were reduced in these mice. Importantly, this shift in pulmonary macrophage polarization in ILC2-deficient mice correlated with improved fungal control and prolonged survival of infected mice. Conversely, adoptive transfer of ILC2s was associated with a type 2 bias associated with less efficient anti-fungal immunity in lungs of recipient mice. Collectively, our date indicate a non-redundant role of ILC2 in orchestrating myeloid anti-cryptococcal immune responses toward a disease exacerbating phenotype.