The neuroimmune CGRP-RAMP1 axis tunes cutaneous adaptive immunity to the microbiota

The somatosensory nervous system surveils external stimuli at barrier tissues, regulating innate immune cells under infection and inflammation. The roles of sensory neurons in controlling the adaptive immune system, and more specifically immunity to the microbiota, however, remain elusive. Here, we identified a mechanism for direct neuroimmune communication between commensal-specific T lymphocytes and somatosensory neurons mediated by the neuropeptide calcitonin gene-related peptide (CGRP) in the skin. Intravital imaging revealed that commensal-specific T cells are in close proximity to cutaneous nerve fibers in vivo. Correspondingly, we observed upregulation of the receptor for the neuropeptide CGRP, RAMP1, in CD8+ T lymphocytes induced by skin commensal colonization. The neuroimmune CGRP-RAMP1 signaling axis functions in commensal-specific T cells to constrain Type 17 responses and moderate the activation status of microbiota-reactive lymphocytes at homeostasis. As such, modulation of neuroimmune CGRP-RAMP1 signaling in commensal-specific T cells shapes the overall activation status of the skin epithelium, thereby impacting the outcome of responses to insults such as wounding. The ability of somatosensory neurons to control adaptive immunity to the microbiota via the CGRP-RAMP1 axis underscores the various layers of regulation and multisystem coordination required for optimal microbiota-reactive T cell functions under steady state and pathology.

The neuroimmune CGRP-RAMP1 axis tunes cutaneous adaptive immunity to the microbiota

The somatosensory nervous system surveils external stimuli at barrier tissues, regulating innate immune cells under infection and inflammation. The roles of sensory neurons in controlling the adaptive immune system, and more specifically immunity to the microbiota, however, remain elusive. Here, we identified a novel mechanism for direct neuroimmune communication between commensal-specific T lymphocytes and somatosensory neurons mediated by the neuropeptide Calcitonin Gene-Related Peptide (CGRP) in the skin. Intravital imaging revealed that commensal-specific T cells are in close proximity to cutaneous nerve fibers in vivo . Correspondingly, we observed upregulation of the receptor for the neuropeptide CGRP, RAMP1, in CD8 + T lymphocytes induced by skin commensal colonization. Neuroimmune CGRP-RAMP1 signaling axis functions in commensal-specific T cells to constrain Type 17 responses and moderate the activation status of microbiota-reactive lymphocytes at homeostasis. As such, modulation of neuroimmune CGRP-RAMP1 signaling in commensal-specific T cells shapes the overall activation status of the skin epithelium, thereby impacting the outcome of responses to insults such as wounding. The ability of somatosensory neurons to control adaptive immunity to the microbiota via the CGRP-RAMP1 axis underscores the various layers of regulation and multisystem coordination required for optimal microbiota-reactive T cell functions under steady state and pathology.

Significance statement

Multisystem coordination at barrier surfaces is critical for optimal tissue functions and integrity, in response to microbial and environmental cues. In this study, we identified a novel neuroimmune crosstalk mechanism between the sensory nervous system and the adaptive immune response to the microbiota, mediated by the neuropeptide CGRP and its receptor RAMP1 on skin microbiota-induced T lymphocytes. The neuroimmune CGPR-RAMP1 axis constrains adaptive immunity to the microbiota and overall limits the activation status of the skin epithelium, impacting tissue responses to wounding. Our study opens the door to a new avenue to modulate adaptive immunity to the microbiota utilizing neuromodulators, allowing for a more integrative and tailored approach to harnessing microbiota-induced T cells to promote barrier tissue protection and repair.

Push-pull mechanics of E-cadherin ectodomains in biomimetic adhesions

E-cadherin plays a central role in cell-cell adhesion. The ectodomains of wild-type cadherins form a crystalline-like two-dimensional lattice in cell-cell interfaces mediated by both trans (apposed cell) and cis (same cell) interactions. In addition to these extracellular forces, adhesive strength is further regulated by cytosolic phenomena involving α and β catenin-mediated interactions between cadherin and the actin cytoskeleton. Cell-cell adhesion can be further strengthened under tension through mechanisms that have not been definitively characterized in molecular detail. Here we quantitatively determine the role of the cadherin ectodomain in mechanosensing. To this end, we devise an E-cadherin-coated emulsion system, in which droplet surface tension is balanced by protein binding strength to give rise to stable areas of adhesion. To reach the honeycomb/cohesive limit, an initial emulsion compression by centrifugation facilitates E-cadherin trans binding, whereas a high protein surface concentration enables the cis-enhanced stabilization of the interface. We observe an abrupt concentration dependence on recruitment into adhesions of constant crystalline density, reminiscent of a first-order phase transition. Removing the lateral cis interaction with a "cis mutant" shifts this transition to higher surface densities leading to denser, yet weaker adhesions. In both proteins, the stabilization of progressively larger areas of deformation is consistent with single-molecule experiments that show a force-dependent lifetime enhancement in the cadherin ectodomain, which may be attributed to the "X-dimer" bond.

A cost analysis of robotic vs. video-assisted thoracic surgery: The impact of the learning curve and the COVID-19 pandemic

Introduction

Robot-assisted thoracoscopic surgery (RATS) is an alternative to video-assessed thoracoscopic surgery (VATS) for the treatment of lung cancer but concern exists regarding the high associated costs. The COVID-19 pandemic added further financial pressure to healthcare systems. This study investigated the impact of the learning curve on the cost-effectiveness of RATS lung resection and the financial impact of the COVID-19 pandemic on a RATS program.

Methods

Patients undergoing RATS lung resection between January 2017 and December 2020 were prospectively followed. A matched cohort of VATS cases were analyzed in parallel. The first 100 and most recent 100 RATS cases performed at our institution were compared to assess the learning curve. Cases performed before and after March 2020 were compared to assess the impact of the COVID-19 pandemic. A comprehensive cost analysis of multiple theatre and postoperative data points was performed using Stata statistics package (v14.2).

Results

365 RATS cases were included. Median cost per procedure was £7,167 and theatre cost accounted for 70%. Major contributing factors to overall cost were operative time and postoperative length of stay. Cost per case was £640 less after passing the learning curve (p < 0.001) largely due to reduced operative time. Comparison of a post-learning curve RATS subgroup matched to 101 VATS cases revealed no significant difference in theatre costs between the two techniques. Overall cost of RATS lung resections performed before and during the COVID-19 pandemic were not significantly different. However, theatre costs were significantly cheaper (£620/case; p < 0.001) and postoperative costs were significantly more expensive (£1,221/case; p = 0.018) during the pandemic.

Discussion

Passing the learning curve is associated with a significant reduction in the theatre costs associated with RATS lung resection and is comparable with the cost of VATS. This study may underestimate the true cost benefit of passing the learning curve due to the effect of the COVID-19 pandemic on theatre costs. The COVID-19 pandemic made RATS lung resection more expensive due to prolonged hospital stay and increased readmission rate. The present study offers some evidence that the initial increased costs associated with RATS lung resection may be gradually offset as a program progresses.

A conserved population of MHC II-restricted, innate-like, commensal-reactive T cells in the gut of humans and mice

Interactions with commensal microbes shape host immunity on multiple levels and play a pivotal role in human health and disease. Tissue-dwelling, antigen-specific T cells are poised to respond to local insults, making their phenotype important in the relationship between host and microbes. Here we show that MHC-II restricted, commensal-reactive T cells in the colon of both humans and mice acquire transcriptional and functional characteristics associated with innate-like T cells. This cell population is abundant and conserved in the human and murine colon and endowed with polyfunctional effector properties spanning classic Th1- and Th17-cytokines, cytotoxic molecules, and regulators of epithelial homeostasis. T cells with this phenotype are increased in ulcerative colitis patients, and their presence aggravates pathology in dextran sodium sulphate-treated mice, pointing towards a pathogenic role in colitis. Our findings add to the expanding spectrum of innate-like immune cells positioned at the frontline of intestinal immune surveillance, capable of acting as sentinels of microbes and the local cytokine milieu.

Th17 cells: from gut homeostasis to CNS pathogenesis

Th17 cells play crucial roles in host-microbe interactions, but can also promote chronic inflammation and tissue pathology. Factors influencing Th17 cell heterogeneity and effector functions in different inflammatory contexts remain unclear. Schnell et al. demonstrate that intestinal Th17 cells form a reservoir from which pathogenic Th17 cells can be elicited during severe tissue inflammation.

Computational model of E-cadherin clustering under force

E-cadherins play a critical role in the formation of cell-cell adhesions for several physiological functions, including tissue development, repair, and homeostasis. The formation of clusters of E-cadherins involves extracellular adhesive (trans-) and lateral (cis-) associations between E-cadherin ectodomains and stabilization through intracellular binding to the actomyosin cytoskeleton. This binding provides force to the adhesion and is required for mechanotransduction. However, the exact role of cytoskeletal force on the clustering of E-cadherins is not well understood. To gain insights into this mechanism, we developed a computational model based on Brownian dynamics. In the model, E-cadherins transit between structural and functional states; they are able to bind and unbind other E-cadherins on the same and/or opposite cell(s) through trans- and cis-interactions while also creating dynamic links with the actomyosin cytoskeleton. Our results show that actomyosin force governs the fraction of E-cadherins in clusters and the size and number of clusters. For low forces (below 10 pN), a large number of small E-cadherin clusters form with less than five E-cadherins each. At higher forces, the probability of forming fewer but larger clusters increases. These findings support the idea that force reinforces cell-cell adhesions, which is consistent with differences in cluster size previously observed between apical and lateral junctions of epithelial tissues.

sLRP1'in up retinol keeps the gut SAAfe

Retinol is shuttled to myeloid cells for conversion to retinoic acid, but the receptor facilitating uptake of SAA:retinol complexes on myeloid cells is unknown. In a recent issue of Science, Bang et al. (2021) use genetic and biochemical approaches to reveal this critical receptor to be LRP1 and show that this axis is essential for intestinal innate and adaptive immune responses.

Image-guided combined ablation and resection in thoracic surgery for the treatment of multiple pulmonary metastases: A preliminary case series

Objectives

To demonstrate the feasibility and preliminary outcomes of a novel hybrid technique combining percutaneous microwave ablation and wire-assisted wedge resection for patients with multiple pulmonary metastases using intraoperative imaging.

Methods

We describe our technique and present a retrospective case series of 4 patients undergoing iCART at our institution between August 2018 and January 2020. Procedures were performed in a hybrid operating suite using the ARTIS Pheno cone beam computerized tomography scanner (Siemens Healthineers, Erlangen, German). Patient information included past history of malignancy as well as lesion size, depth, location, and histology result. Surgical complications and length of stay were also recorded.

Results

Five procedures were performed on 4 patients during the study period. One patient underwent bilateral procedures 4 weeks apart. All patients underwent at least 1 ablation and 1 wedge resection during the combined procedure. Patient ages ranged from 40 to 66 years and the majority (75%) were men. All had a past history of cancer. Lesions were treated in every lobe. Size and depth ranged from 6 to 24 mm and 21 to 33 mm, respectively, for ablated nodules and 5 to 27 mm and 0 to 22 mm, respectively, for the wedge resected nodules. Three procedures were completed uniportal and operative time ranged from 51 to 210 minutes. All cases sustained <10 mL blood loss. There were 2 intraoperative pneumothorax, 1 prevented successful completion of the ablation. One patient required a prolonged period of postoperative physiotherapy and was discharged on day 6. The other patients were discharged on postoperative day 2 or 3. All 5 histology specimens confirmed metastatic disease.

Conclusions

Our hybrid approach provides a minimally invasive and comprehensive personalized therapy for patients with multiple pulmonary metastases under a single general anesthetic. It provides histology-based diagnosis whilst minimizing lung tissue loss and eliminating the need for transfer from radiology to operating theatre. Emergence of ablation as a treatment for stage 1 non–small cell lung cancer and the expansion of lung cancer screening may widen the application of iCART in the future.

Response to Comments on "Aberrant type 1 immunity drives susceptibility to mucosal fungal infections"

Puel and Casanova and Kisand et al. challenge our conclusions that interferonopathy and not IL-17/IL-22 autoantibodies promote candidiasis in autoimmune polyendocrinopathy–candidiasis–ectodermal dystrophy. We acknowledge that conclusive evidence for causation is difficult to obtain in complex human diseases. However, our studies clearly document interferonopathy driving mucosal candidiasis with intact IL-17/IL-22 responses in Aire-deficient mice, with strong corroborative evidence in patients.

Gut microbiome stability and dynamics in healthy donors and patients with non-gastrointestinal cancers

As microbial therapeutics are increasingly being tested in diverse patient populations, it is essential to understand the host and environmental factors influencing the microbiome. Through analysis of 1,359 gut microbiome samples from 946 healthy donors of the Milieu Intérieur cohort, we detail how microbiome composition is associated with host factors, lifestyle parameters, and disease states. Using a genome-based taxonomy, we found biological sex was the strongest driver of community composition. Additionally, bacterial populations shift across decades of life (age 20-69), with Bacteroidota species consistently increased with age while Actinobacteriota species, including Bifidobacterium, decreased. Longitudinal sampling revealed that short-term stability exceeds interindividual differences. By accounting for these factors, we defined global shifts in the microbiomes of patients with non-gastrointestinal tumors compared with healthy donors. Together, these results demonstrated that the microbiome displays predictable variations as a function of sex, age, and disease state. These variations must be considered when designing microbiome-targeted therapies or interpreting differences thought to be linked to pathophysiology or therapeutic response.

Prenatal maternal infection promotes tissue-specific immunity and inflammation in offspring

The immune system has evolved in the face of microbial exposure. How maternal infection experienced at distinct developmental stages shapes the offspring immune system remains poorly understood. Here, we show that during pregnancy, maternally restricted infection can have permanent and tissue-specific impacts on offspring immunity. Mechanistically, maternal interleukin-6 produced in response to infection can directly impose epigenetic changes on fetal intestinal epithelial stem cells, leading to long-lasting impacts on intestinal immune homeostasis. As a result, offspring of previously infected dams develop enhanced protective immunity to gut infection and increased inflammation in the context of colitis. Thus, maternal infection can be coopted by the fetus to promote long-term, tissue-specific fitness, a phenomenon that may come at the cost of predisposition to inflammatory disorders.

Combined minimally invasive resection of thoracic neurogenic dumbbell tumors: A European case series

Background

Paraspinal tumors are rare neoplasms arising from neurogenic elements of the posterior mediastinum and surgical resection can be challenging. Here, we demonstrate feasibility and outcomes from the first European case series of combined laminectomy and video‐assisted thoracoscopic surgery (VATS) resection of thoracic neurogenic dumbbell tumors.

Methods

A retrospective review of all combined thoracic dumbbell tumor resections performed at our institution between March 2015 to February 2019 was undertaken. Outcomes included operative time, blood loss, length of stay and recurrence rate. Statistical analysis was performed with SPSS statistics (v26). Values are given as mean ± standard deviation and median ± interquartile range.

Results

Seven patients were included in the case series and there were no major complications or mortality. Mean tumor size and operative time were 66 (± 35) mm and 171 (± 63) min, respectively. Median blood loss and length of stay were 40 (± 70) ml and four (± 3) days, respectively. One patient required conversion to thoracotomy to remove a tumor of 135 mm in maximal dimension. Histology in all seven cases confirmed schwannoma. There was no disease recurrence at a maximum follow‐up of 54 months.

Conclusions

Our experience demonstrates favorable operative times, minimal blood loss and short length of stay when dealing with relatively large tumors compared to previous reports. Thoracotomy may be required for tumors exceeding 90 mm and chest drain removal on the operative day can facilitate early mobility and discharge. We advocate a combined, minimally invasive laminectomy and VATS resection as the gold‐standard approach for thoracic neurogenic dumbbell tumors.

Environmental enteric dysfunction induces regulatory T cells that inhibit local CD4+ T cell responses and impair oral vaccine efficacy

Environmental enteric dysfunction (EED) is a gastrointestinal inflammatory disease caused by malnutrition and chronic infection. EED is associated with stunting in children and reduced efficacy of oral vaccines. To study the mechanisms of oral vaccine failure during EED, we developed a microbiota- and diet-dependent mouse EED model. Analysis of E. coli-labile toxin vaccine-specific CD4⁺ T cells in these mice revealed impaired CD4⁺ T cell responses in the small intestine and but not the lymph nodes. EED mice exhibited increased frequencies of small intestine-resident RORγT⁺FOXP3⁺ regulatory T (Treg) cells. Targeted deletion of RORγT from Treg cells restored small intestinal vaccine-specific CD4 T cell responses and vaccine-mediated protection upon challenge. However, ablation of RORγT⁺FOXP3⁺ Treg cells made mice more susceptible to EED-induced stunting. Our findings provide insight into the poor efficacy of oral vaccines in EED and highlight how RORγT⁺FOXP3⁺ Treg cells can regulate intestinal immunity while leaving systemic responses intact.

Aberrant type 1 immunity drives susceptibility to mucosal fungal infections

Human monogenic disorders have revealed the critical contribution of type 17 responses in mucosal fungal surveillance. We unexpectedly found that in certain settings, enhanced type 1 immunity rather than defective type 17 responses can promote mucosal fungal infection susceptibility. Notably, in mice and humans with AIRE deficiency, an autoimmune disease characterized by selective susceptibility to mucosal but not systemic fungal infection, mucosal type 17 responses are intact while type 1 responses are exacerbated. These responses promote aberrant interferon-γ (IFN-γ)- and signal transducer and activator of transcription 1 (STAT1)-dependent epithelial barrier defects as well as mucosal fungal infection susceptibility. Concordantly, genetic and pharmacologic inhibition of IFN-γ or Janus kinase (JAK)-STAT signaling ameliorates mucosal fungal disease. Thus, we identify aberrant T cell-dependent, type 1 mucosal inflammation as a critical tissue-specific pathogenic mechanism that promotes mucosal fungal infection susceptibility in mice and humans.

Tracheal leiomyoma mimicking asthma for over 20 years

Benign tracheal tumours have an incidence of 1 in 1,000,000, of which leiomyomas represent only 1%. We report a case of tracheal leiomyoma masquerading as asthma for over 20 years. A 48-year-old man presented aged 26 years with asthma symptoms unresponsive to treatments and an obstructive spirometry pattern. Symptoms were not particularly troubling but suddenly exacerbated 22 years later. Flow-volume studies were consistent with upper airway obstruction. Computed tomography chest revealed a 2.3 cm mass arising from the posterior aspect of the trachea 2 cm above the carina. Bronchoscopic resection was performed using a Nd:YAG laser. Histology confirmed leiomyoma. Follow-up after 6 weeks revealed complete resolution of symptoms with normal spirometry. Tracheal masses should be considered in any patient with atypical asthma. A flow-volume loop may provide a clue to diagnosis and bronchoscopic laser resection is a minimally invasive treatment option.

Trans-endocytosis elicited by nectins transfers cytoplasmic cargo, including infectious material, between cells

Here, we show that cells expressing the adherens junction protein nectin-1 capture nectin-4-containing membranes from the surface of adjacent cells in a trans-endocytosis process. We find that internalized nectin-1-nectin-4 complexes follow the endocytic pathway. The nectin-1 cytoplasmic tail controls transfer: its deletion prevents trans-endocytosis, while its exchange with the nectin-4 tail reverses transfer direction. Nectin-1-expressing cells acquire dye-labeled cytoplasmic proteins synchronously with nectin-4, a process most active during cell adhesion. Some cytoplasmic cargo remains functional after transfer, as demonstrated with encapsidated genomes of measles virus (MeV). This virus uses nectin-4, but not nectin-1, as a receptor. Epithelial cells expressing nectin-4, but not those expressing another MeV receptor in its place, can transfer infection to nectin-1-expressing primary neurons. Thus, this newly discovered process can move cytoplasmic cargo, including infectious material, from epithelial cells to neurons. We name the process nectin-elicited cytoplasm transfer (NECT). NECT-related trans-endocytosis processes may be exploited by pathogens to extend tropism. This article has an associated First Person interview with the first author of the paper.

Neuropeptide CGRP Limits Group 2 Innate Lymphoid Cell Responses and Constrains Type 2 Inflammation

Innate lymphocytes maintain tissue homeostasis at mucosal barriers, with group 2 innate lymphoid cells (ILC2s) producing type 2 cytokines and controlling helminth infection. While the molecular understanding of ILC2 responses has advanced, the complexity of microenvironmental factors impacting ILC2s is becoming increasingly apparent. Herein, we used single-cell analysis to explore the diversity of gene expression among lung lymphocytes during helminth infection. Following infection, we identified a subset of ILC2s that preferentially expressed Il5-encoding interleukin (IL)-5, together with Calca-encoding calcitonin gene-related peptide (CGRP) and its cognate receptor components. CGRP in concert with IL-33 and neuromedin U (NMU) supported IL-5 but constrained IL-13 expression and ILC2 proliferation. Without CGRP signaling, ILC2 responses and worm expulsion were enhanced. Collectively, these data point to CGRP as a context-dependent negative regulatory factor that shapes innate lymphocyte responses to alarmins and neuropeptides during type 2 innate immune responses.

Commensal-specific T cell plasticity promotes rapid tissue adaptation to injury

Barrier tissues are primary targets of environmental stressors and are home to the largest number of antigen-experienced lymphocytes in the body, including commensal-specific T cells. We found that skin-resident commensal-specific T cells harbor a paradoxical program characterized by a type 17 program associated with a poised type 2 state. Thus, in the context of injury and exposure to inflammatory mediators such as interleukin-18, these cells rapidly release type 2 cytokines, thereby acquiring contextual functions. Such acquisition of a type 2 effector program promotes tissue repair. Aberrant type 2 responses can also be unleashed in the context of local defects in immunoregulation. Thus, commensal-specific T cells co-opt tissue residency and cell-intrinsic flexibility as a means to promote both local immunity and tissue adaptation to injury.

Candidate plasma biomarkers for predicting ascending aortic aneurysm in bicuspid aortic valve disease

Background

Bicuspid aortic valve (BAV) disease is the most common congenital cardiac abnormality affecting 1–2% of the population and is associated with a significantly increased risk of ascending aortic aneurysm. However, predicting which patients will develop aneurysms remains a challenge. This pilot study aimed to identify candidate plasma biomarkers for monitoring ascending aortic diameter and predicting risk of future aneurysm in BAV patients.

Methods

Plasma samples were collected pre-operatively from BAV patients undergoing aortic valve surgery. Maximum ascending aortic diameter was measured on pre-operative transoesophageal echocardiography. Maximum diameter ≥ 45 mm was classified as aneurysmal. Sequential Window Acquisition of all THeoretical Mass Spectra (SWATH-MS), an advanced mass spectrometry technique, was used to identify and quantify all proteins within the samples. Protein abundance and aortic diameter were correlated using logistic regression. Levene’s test was used to identify proteins demonstrating low abundance variability in the aneurysmal patients (consistent expression in disease), and high variability in the non-aneurysmal patients (differential expression between ‘at risk’ and not ‘at risk’ patients).

Results

Fifteen plasma samples were collected (seven non-aneurysmal and 8 aneurysmal BAV patients). The mean age of the patients was 55.5 years and the majority were female (10/15, 67%). Four proteins (haemoglobin subunits alpha, beta and delta and mannan-binding lectin serine protease) correlated significantly with maximal ascending aortic diameter (p < 0.05, r = 0.5–0.6). Five plasma proteins demonstrated significantly lower variability in the aneurysmal group and may indicate increased risk of aneurysm in non-aneurysmal patients (DNA-dependent protein kinase catalytic subunit, lumican, tetranectin, gelsolin and cartilage acidic protein 1). A further 7 proteins were identified only in the aneurysmal group (matrin-3, glucose-6-phosphate isomerase, coactosin-like protein, peptidyl-prolyl cis-trans isomerase A, golgin subfamily B member 1, myeloperoxidase and 2′-deoxynucleoside 5′-phosphate N-hydrolase 1).

Conclusions

This study is the first to identify candidate plasma biomarkers for predicting aortic diameter and risk of future aneurysm in BAV patients. It provides valuable pilot data and proof of principle that could be used to design a large-scale prospective investigation. Ultimately, a more affordable ‘off-the-shelf’ follow-on blood assay could then be developed in place of SWATH-MS, for use in the healthcare setting.

Electronic supplementary material

The online version of this article (10.1186/s13019-018-0762-1) contains supplementary material, which is available to authorized users.

Pathogenic IgG4 autoantibodies from endemic pemphigus foliaceus recognize a desmoglein-1 conformational epitope

Fogo Selvagem (FS), the endemic form of pemphigus foliaceus, is mediated by pathogenic IgG4 autoantibodies against the amino-terminal extracellular cadherin domain of the desmosomal cadherin desmoglein 1 (Dsg1). Here we define the detailed epitopes of these pathogenic antibodies. Proteolytic footprinting showed that IgG4 from 95% of FS donor sera (19/20) recognized a 16-residue peptide (A129LNSMGQDLERPLELR144) from the EC1 domain of Dsg1 that overlaps the binding site for an adhesive-partner desmosomal cadherin molecule. Mutation of Dsg1 residues M133 and Q135 reduced the binding of FS IgG4 autoantibodies to Dsg1 by ∼50%. Molecular modeling identified two nearby EC1 domain residues (Q82 and V83) likely to contribute to the epitope. Mutation of these residues completely abolished the binding of FS IgG4 to Dsg1. Bead aggregation assays showed that native binding interactions between Dsg1 and desmocollin 1 (Dsc1), which underlie desmosome structure, were abolished by Fab fragments of FS IgG4. These results further define the molecular mechanism by which FS IgG4 autoantibodies interfere with desmosome structure and lead to cell-cell detachment, the hallmark of this disease.

Staphylococcus aureus and Staphylococcus epidermidis strain diversity underlying pediatric atopic dermatitis

The heterogeneous course, severity, and treatment responses among patients with atopic dermatitis (AD; eczema) highlight the complexity of this multifactorial disease. Prior studies have used traditional typing methods on cultivated isolates or sequenced a bacterial marker gene to study the skin microbial communities of AD patients. Shotgun metagenomic sequence analysis provides much greater resolution, elucidating multiple levels of microbial community assembly ranging from kingdom to species and strain-level diversification. We analyzed microbial temporal dynamics from a cohort of pediatric AD patients sampled throughout the disease course. Species-level investigation of AD flares showed greater Staphylococcus aureus predominance in patients with more severe disease and Staphylococcus epidermidis predominance in patients with less severe disease. At the strain level, metagenomic sequencing analyses demonstrated clonal S. aureus strains in more severe patients and heterogeneous S. epidermidis strain communities in all patients. To investigate strain-level biological effects of S. aureus, we topically colonized mice with human strains isolated from AD patients and controls. This cutaneous colonization model demonstrated S. aureus strain-specific differences in eliciting skin inflammation and immune signatures characteristic of AD patients. Specifically, S. aureus isolates from AD patients with more severe flares induced epidermal thickening and expansion of cutaneous T helper 2 (T_H2) and T_H17 cells. Integrating high-resolution sequencing, culturing, and animal models demonstrated how functional differences of staphylococcal strains may contribute to the complexity of AD disease.

c-MAF-dependent regulatory T cells mediate immunological tolerance to a gut pathobiont

Both microbial and host genetic factors contribute to the pathogenesis of autoimmune diseases. There is accumulating evidence that microbial species that potentiate chronic inflammation, as in inflammatory bowel disease, often also colonize healthy individuals. These microorganisms, including the Helicobacter species, can induce pathogenic T cells and are collectively referred to as pathobionts. However, how such T cells are constrained in healthy individuals is not yet understood. Here we report that host tolerance to a potentially pathogenic bacterium, Helicobacter hepaticus, is mediated by the induction of RORγt+FOXP3+ regulatory T (iTreg) cells that selectively restrain pro-inflammatory T helper 17 (TH17) cells and whose function is dependent on the transcription factor c-MAF. Whereas colonization of wild-type mice by H. hepaticus promoted differentiation of RORγt-expressing microorganism-specific iTreg cells in the large intestine, in disease-susceptible IL-10-deficient mice, there was instead expansion of colitogenic TH17 cells. Inactivation of c-MAF in the Treg cell compartment impaired differentiation and function, including IL-10 production, of bacteria-specific iTreg cells, and resulted in the accumulation of H. hepaticus-specific inflammatory TH17 cells and spontaneous colitis. By contrast, RORγt inactivation in Treg cells had only a minor effect on the bacteria-specific Treg and TH17 cell balance, and did not result in inflammation. Our results suggest that pathobiont-dependent inflammatory bowel disease is driven by microbiota-reactive T cells that have escaped this c-MAF-dependent mechanism of iTreg-TH17 homeostasis.

Non-classical Immunity Controls Microbiota Impact on Skin Immunity and Tissue Repair

Mammalian barrier surfaces are constitutively colonized by numerous microorganisms. We explored how the microbiota was sensed by the immune system and the defining properties of such responses. Here, we show that a skin commensal can induce T cell responses in a manner that is restricted to non-classical MHC class I molecules. These responses are uncoupled from inflammation and highly distinct from pathogen-induced cells. Commensal-specific T cells express a defined gene signature that is characterized by expression of effector genes together with immunoregulatory and tissue-repair signatures. As such, non-classical MHCI-restricted commensal-specific immune responses not only promoted protection to pathogens, but also accelerated skin wound closure. Thus, the microbiota can induce a highly physiological and pleiotropic form of adaptive immunity that couples antimicrobial function with tissue repair. Our work also reveals that non-classical MHC class I molecules, an evolutionarily ancient arm of the immune system, can promote homeostatic immunity to the microbiota.

White Adipose Tissue Is a Reservoir for Memory T Cells and Promotes Protective Memory Responses to Infection

White adipose tissue bridges body organs and plays a fundamental role in host metabolism. To what extent adipose tissue also contributes to immune surveillance and long-term protective defense remains largely unknown. Here, we have shown that at steady state, white adipose tissue contained abundant memory lymphocyte populations. After infection, white adipose tissue accumulated large numbers of pathogen-specific memory T cells, including tissue-resident cells. Memory T cells in white adipose tissue expressed a distinct metabolic profile, and white adipose tissue from previously infected mice was sufficient to protect uninfected mice from lethal pathogen challenge. Induction of recall responses within white adipose tissue was associated with the collapse of lipid metabolism in favor of antimicrobial responses. Our results suggest that white adipose tissue represents a memory T cell reservoir that provides potent and rapid effector memory responses, positioning this compartment as a potential major contributor to immunological memory.

The Mouse Model of Infection with Citrobacter rodentium

Citrobacter rodentium is a murine mucosal pathogen used as a model to elucidate the molecular and cellular pathogenesis of infection with two clinically important human gastrointestinal pathogens, enteropathogenic Escherichia coli (EPEC) and enterohaemorrhagic E. coli (EHEC). C. rodentium infection provides an excellent model to study different aspects of host-pathogen interaction in the gut, including intestinal inflammatory responses during bacteria-induced colitis, mucosal healing and epithelial repair, the induction of mucosal immune responses, and the role of the intestinal microbiota in mediating resistance to colonization by enteric pathogens. This unit provides detailed protocols for growing this bacterium, infecting mice by intragastric inoculation, measuring bacterial loads in feces and organs, and monitoring intestinal pathology induced by infection. Additional protocols describe steps needed to create frozen stocks, establish a growth curve, perform ex vivo organ cultures, isolate immune cells from the large intestine, and measure immune response by flow cytometry. © 2017 by John Wiley & Sons, Inc.

Homeostatic Immunity and the Microbiota

The microbiota plays a fundamental role in the induction, education, and function of the host immune system. In return, the host immune system has evolved multiple means by which to maintain its symbiotic relationship with the microbiota. The maintenance of this dialogue allows the induction of protective responses to pathogens and the utilization of regulatory pathways involved in the sustained tolerance to innocuous antigens. The ability of microbes to set the immunological tone of tissues, both locally and systemically, requires tonic sensing of microbes and complex feedback loops between innate and adaptive components of the immune system. Here we review the dominant cellular mediators of these interactions and discuss emerging themes associated with our current understanding of the homeostatic immunological dialogue between the host and its microbiota.

Mammalian O-mannosylation of cadherins and plexins is independent of protein O-mannosyltransferases 1 and 2

Protein O-mannosylation is found in yeast and metazoans, and a family of conserved orthologous protein O-mannosyltransferases is believed to initiate this important post-translational modification. We recently discovered that the cadherin superfamily carries O-linked mannose (O-Man) glycans at highly conserved residues in specific extracellular cadherin domains, and it was suggested that the function of E-cadherin was dependent on the O-Man glycans. Deficiencies in enzymes catalyzing O-Man biosynthesis, including the two human protein O-mannosyltransferases, POMT1 and POMT2, underlie a subgroup of congenital muscular dystrophies designated α-dystroglycanopathies, because deficient O-Man glycosylation of α-dystroglycan disrupts laminin interaction with α-dystroglycan and the extracellular matrix. To explore the functions of O-Man glycans on cadherins and protocadherins, we used a combinatorial gene-editing strategy in multiple cell lines to evaluate the role of the two POMTs initiating O-Man glycosylation and the major enzyme elongating O-Man glycans, the protein O-mannose β-1,2-N-acetylglucosaminyltransferase, POMGnT1. Surprisingly, O-mannosylation of cadherins and protocadherins does not require POMT1 and/or POMT2 in contrast to α-dystroglycan, and moreover, the O-Man glycans on cadherins are not elongated. Thus, the classical and evolutionarily conserved POMT O-mannosylation pathway is essentially dedicated to α-dystroglycan and a few other proteins, whereas a novel O-mannosylation process in mammalian cells is predicted to serve the large cadherin superfamily and other proteins.

Endogenous Reference Genes for Gene Expression Studies on Bicuspid Aortic Valve Associated Aortopathy in Humans

Bicuspid aortic valve (BAV) disease is the most common congenital cardiac abnormality and predisposes patients to life-threatening aortic complications including aortic aneurysm. Quantitative real-time reverse transcription PCR (qRT-PCR) is one of the most commonly used methods to investigate underlying molecular mechanisms involved in aortopathy. The accuracy of the gene expression data is dependent on normalization by appropriate housekeeping (HK) genes, whose expression should remain constant regardless of aortic valve morphology, aortic diameter and other factors associated with aortopathy. Here, we identified an appropriate set of HK genes to be used as endogenous reference for quantifying gene expression in ascending aortic tissue using a spin column-based RNA extraction method. Ascending aortic biopsies were collected intra-operatively from patients undergoing aortic valve and/or ascending aortic surgery. These patients had BAV or tricuspid aortic valve (TAV), and the aortas were either dilated (≥4.5cm) or undilated. The cohort had an even distribution of gender, valve disease and hypertension. The expression stability of 12 reference genes were investigated (ATP5B, ACTB, B2M, CYC1, EIF4A2, GAPDH, SDHA, RPL13A, TOP1, UBC, YWHAZ, and 18S) using geNorm software. The most stable HK genes were found to be GAPDH, UBC and ACTB. Both GAPDH and UBC demonstrated relative stability regardless of valve morphology, aortic diameter, gender and age. The expression of B2M and SDHA were found to be the least stable HK genes. We propose the use of GAPDH, UBC and ACTB as reference genes for gene expression studies of BAV aortopathy using ascending aortic tissue.

Critical role of fatty acid metabolism in ILC2-mediated barrier protection during malnutrition and helminth infection

Belkaid et al. show that type 2 innate lymphoid cells rely predominately on fatty acid metabolism during helminth infection and malnutrition.

Innate lymphoid cells (ILC) play an important role in many immune processes, including control of infections, inflammation, and tissue repair. To date, little is known about the metabolism of ILC and whether these cells can metabolically adapt in response to environmental signals. Here we show that type 2 innate lymphoid cells (ILC2), important mediators of barrier immunity, predominantly depend on fatty acid (FA) metabolism during helminth infection. Further, in situations where an essential nutrient, such as vitamin A, is limited, ILC2 sustain their function and selectively maintain interleukin 13 (IL-13) production via increased acquisition and utilization of FA. Together, these results reveal that ILC2 preferentially use FAs to maintain their function in the context of helminth infection or malnutrition and propose that enhanced FA usage and FA-dependent IL-13 production by ILC2 could represent a host adaptation to maintain barrier immunity under dietary restriction.

T-bet is a key modulator of IL-23-driven pathogenic CD4(+) T cell responses in the intestine

IL-23 is a key driver of pathogenic Th17 cell responses. It has been suggested that the transcription factor T-bet is required to facilitate IL-23-driven pathogenic effector functions; however, the precise role of T-bet in intestinal T cell responses remains elusive. Here, we show that T-bet expression by T cells is not required for the induction of colitis or the differentiation of pathogenic Th17 cells but modifies qualitative features of the IL-23-driven colitogenic response by negatively regulating IL-23R expression. Consequently, absence of T-bet leads to unrestrained Th17 cell differentiation and activation characterized by high amounts of IL-17A and IL-22. The combined increase in IL-17A/IL-22 results in enhanced epithelial cell activation and inhibition of either IL-17A or IL-22 leads to disease amelioration. Our study identifies T-bet as a key modulator of IL-23-driven colitogenic responses in the intestine and has important implications for understanding of heterogeneity among inflammatory bowel disease patients.

Commensal-dendritic-cell interaction specifies a unique protective skin immune signature

The skin represents the body’s primary interface with the environment, acting as the first line of physical and immunological defense. This organ is also home to trillions of microbes (bacteria, fungi and viruses) that play an important role in tissue homeostasis and local immunity. Skin microbial communities are highly diverse and can be remodeled over time or in response to environmental challenges. How in the context of this complexity, individual commensals may differentially modulate skin immunity and what the consequences of these responses for tissue physiology are remain unclear. Here, we demonstrate that defined commensals dominantly impact skin immunity and identify the cellular mediators involved in this specification. In particular, colonization with Staphylococcus epidermidis induces IL-17A+CD8+T cells that home to the epidermis, enhance innate barrier immunity and limit pathogen invasion. These commensal-specific T cell responses result from the coordinated action of skin resident dendritic cell subsets and are not associated with inflammation, revealing that tissue resident cells are poised to sense and respond to alterations in microbial communities. This dialogue may represent an evolutionary means by which the skin immune system uses fluctuating commensal clues to calibrate barrier immunity and provide heterologous protection against invasive pathogens. Altogether these findings reveal that the skin immune landscape is a highly dynamic environment that can be rapidly and specifically remodeled by encounters with defined commensals, findings that have profound implications for our understanding of tissue specific immunity and pathologies.

Operative time and outcome of enhanced recovery after surgery after laparoscopic colorectal surgery

Background and Objectives:

Combining laparoscopy and enhanced recovery provides benefit to short-term outcomes after colorectal surgery. Advances in training and techniques have allowed surgeons to operate on cases that are technically challenging and associated with prolonged operative time. Laparoscopic techniques improve the outcome of enhanced recovery after colorectal surgery; however, there are no specifications on the effect of prolonged operations on the outcome. The objective was to elucidate the impact of prolonged surgery and blood loss on the outcome of enhanced recovery after surgery after laparoscopic colorectal surgery.

Methods:

Four-hundred patients who underwent elective colorectal resection on enhanced recovery after surgery in Yeovil District Hospital between 2002 and 2009 were retrospectively reviewed. Delayed discharge was defined as a prolonged length of stay beyond the mean in this series (≥8 days).

Results:

Three-hundred eighty-five patients were included. Median operative time was 180 minutes with a median blood loss of 100 mL. Conversion was not associated with a prolonged length of stay. Operative time and blood loss correlated with length of stay in a stepwise fashion. There were 2 cutoff points of operative time at 160 minutes and 300 minutes (5 hours), where risk of prolonged stay increased significantly (odds ratio [OR] = 2.02; 95% confidence interval [CI], 1.05–3.90; P = .027), and blood loss of >500 mL (OR = 3.114; 95% CI, 1.501–6.462, P = .002).

Conclusions:

Total operative timing impacts negatively on the outcome of enhanced recovery after laparoscopic colorectal resections with increased risk of delayed discharge seen after ∼2.5 hours and 5-hour duration.

The autophagy gene Atg16l1 differentially regulates Treg and TH2 cells to control intestinal inflammation

A polymorphism in the autophagy gene Atg16l1 is associated with susceptibility to inflammatory bowel disease (IBD); however, it remains unclear how autophagy contributes to intestinal immune homeostasis. Here, we demonstrate that autophagy is essential for maintenance of balanced CD4⁺ T cell responses in the intestine. Selective deletion of Atg16l1 in T cells in mice resulted in spontaneous intestinal inflammation that was characterized by aberrant type 2 responses to dietary and microbiota antigens, and by a loss of Foxp3⁺ T_reg cells. Specific ablation of Atg16l1 in Foxp3⁺ T_reg cells in mice demonstrated that autophagy directly promotes their survival and metabolic adaptation in the intestine. Moreover, we also identify an unexpected role for autophagy in directly limiting mucosal T_H2 cell expansion. These findings provide new insights into the reciprocal control of distinct intestinal T_H cell responses by autophagy, with important implications for understanding and treatment of chronic inflammatory disorders.

DOI:http://dx.doi.org/10.7554/eLife.12444.001

The gut presents a puzzle to our immune system. Immune cells must rapidly respond to antigens produced by harmful bacteria, but food and the beneficial bacteria that inhabit the gut also produce antigens that our immune system must tolerate. Inappropriate immune responses in the gut can lead to inflammatory bowel disease, a debilitating disease with no current cure. We do not fully understand why these harmful inflammatory responses arise, but we know that genetic factors are important. Mutations in genes that affect a process known as autophagy – a pathway that breaks down and recycles unwanted material inside cells – make inflammatory bowel disease more likely to develop, but exactly how they do so remains unclear.

T helper cells are crucial controllers of intestinal immune responses and changes in their numbers and behaviour occur during inflammatory bowel disease. Kabat et al. explored how the autophagy pathway affects these key immune cells in mice. Blocking autophagy in T cells altered the balance of different types of T helper cells in the gut. A crucial population of regulatory T cells, which keep inflammatory responses in check, was lost. At the same time, another population of T cells expanded: the T helper 2 (T_H2) cells that are responsible for driving allergies. As a result, the mice developed intestinal inflammation and produced antibodies against gut bacteria and food.

Overall, Kabat et al.’s results show that autophagy defects can alter the balance of different types of T cells in the gut, leading to inflammation in the intestine. These observations contribute to our understanding of how genetic changes may influence susceptibility to inflammatory bowel disease. They also suggest that drugs that activate autophagy could help to treat diseases associated with changes in regulatory T cells or T_H2 cells, including inflammatory bowel disease and allergies. It will now be important to test this and to confirm whether similar changes in T cells are present in humans that have mutations in autophagy genes.

DOI:http://dx.doi.org/10.7554/eLife.12444.002

Microbiota-Dependent Sequelae of Acute Infection Compromise Tissue-Specific Immunity

Infections have been proposed as initiating factors for inflammatory disorders; however, identifying associations between defined infectious agents and the initiation of chronic disease has remained elusive. Here, we report that a single acute infection can have dramatic and long-term consequences for tissue-specific immunity. Following clearance of Yersinia pseudotuberculosis, sustained inflammation and associated lymphatic leakage in the mesenteric adipose tissue deviates migratory dendritic cells to the adipose compartment, thereby preventing their accumulation in the mesenteric lymph node. As a consequence, canonical mucosal immune functions, including tolerance and protective immunity, are persistently compromised. Post-resolution of infection, signals derived from the microbiota maintain inflammatory mesentery remodeling and consequently, transient ablation of the microbiota restores mucosal immunity. Our results indicate that persistent disruption of communication between tissues and the immune system following clearance of an acute infection represents an inflection point beyond which tissue homeostasis and immunity is compromised for the long-term. VIDEO ABSTRACT.

Commensal-dendritic-cell interaction specifies a unique protective skin immune signature

The skin represents the primary interface between the host and the environment. This organ is also home to trillions of microorganisms that play an important role in tissue homeostasis and local immunity. Skin microbial communities are highly diverse and can be remodelled over time or in response to environmental challenges. How, in the context of this complexity, individual commensal microorganisms may differentially modulate skin immunity and the consequences of these responses for tissue physiology remains unclear. Here we show that defined commensals dominantly affect skin immunity and identify the cellular mediators involved in this specification. In particular, colonization with Staphylococcus epidermidis induces IL-17A(+) CD8(+) T cells that home to the epidermis, enhance innate barrier immunity and limit pathogen invasion. Commensal-specific T-cell responses result from the coordinated action of skin-resident dendritic cell subsets and are not associated with inflammation, revealing that tissue-resident cells are poised to sense and respond to alterations in microbial communities. This interaction may represent an evolutionary means by which the skin immune system uses fluctuating commensal signals to calibrate barrier immunity and provide heterologous protection against invasive pathogens. These findings reveal that the skin immune landscape is a highly dynamic environment that can be rapidly and specifically remodelled by encounters with defined commensals, findings that have profound implications for our understanding of tissue-specific immunity and pathologies.

The alarmin IL-33 promotes regulatory T-cell function in the intestine

FOXP3(+) regulatory T cells (Treg cells) are abundant in the intestine, where they prevent dysregulated inflammatory responses to self and environmental stimuli. It is now appreciated that Treg cells acquire tissue-specific adaptations that facilitate their survival and function; however, key host factors controlling the Treg response in the intestine are poorly understood. The interleukin (IL)-1 family member IL-33 is constitutively expressed in epithelial cells at barrier sites, where it functions as an endogenous danger signal, or alarmin, in response to tissue damage. Recent studies in humans have described high levels of IL-33 in inflamed lesions of inflammatory bowel disease patients, suggesting a role for this cytokine in disease pathogenesis. In the intestine, both protective and pathological roles for IL-33 have been described in murine models of acute colitis, but its contribution to chronic inflammation remains ill defined. Here we show in mice that the IL-33 receptor ST2 is preferentially expressed on colonic Treg cells, where it promotes Treg function and adaptation to the inflammatory environment. IL-33 signalling in T cells stimulates Treg responses in several ways. First, it enhances transforming growth factor (TGF)-β1-mediated differentiation of Treg cells and, second, it provides a necessary signal for Treg-cell accumulation and maintenance in inflamed tissues. Strikingly, IL-23, a key pro-inflammatory cytokine in the pathogenesis of inflammatory bowel disease, restrained Treg responses through inhibition of IL-33 responsiveness. These results demonstrate a hitherto unrecognized link between an endogenous mediator of tissue damage and a major anti-inflammatory pathway, and suggest that the balance between IL-33 and IL-23 may be a key controller of intestinal immune responses.

Regulatory T cells and immune tolerance in the intestine

A fundamental role of the mammalian immune system is to eradicate pathogens while minimizing immunopathology. Instigating and maintaining immunological tolerance within the intestine represents a unique challenge to the mucosal immune system. Regulatory T cells are critical for continued immune tolerance in the intestine through active control of innate and adaptive immune responses. Dynamic adaptation of regulatory T-cell populations to the intestinal tissue microenvironment is key in this process. Here, we discuss specialization of regulatory T-cell responses in the intestine, and how a breakdown in these processes can lead to chronic intestinal inflammation.

Should resuscitative thoracotomy be performed in the pre-hospital phase of care?

Penetrating thoracic trauma is increasing in the UK and elsewhere and immediate transfer to a Major Trauma Centre with cardio-thoracic expertise is usually optimal management. Pre-hospital traumatic cardiac arrest has an extremely poor prognosis. Performing thoracotomy before arrival in hospital has produced neurologically intact survivors in several case series. The technique described involves rapid clamshell thoracotomy and release of pericardial tamponade. Favourable outcomes appear to be associated with a single stab wound to the heart causing cardiac tamponade. Pre-hospital thoracotomy is described in the current European Resuscitation Guidelines and courses for non-surgeons are now taught at the Royal College of Surgeons of England and at the Surgical Skills Training Centre at Newcastle Freeman Hospital. It is likely that further survivors will be reported as the technique becomes more widely used. Alternatives to pre-hospital thoracotomy in the future for patients with hypovolaemic cardiac arrest may include resuscitative endovascular balloon occlusion of the aorta and pre-hospital extended preservation and resuscitation.

T cell depletion protects against alveolar destruction due to chronic cigarette smoke exposure in mice

The role of T cells in chronic obstructive pulmonary disease (COPD) is not well understood. We have previously demonstrated that chronic cigarette smoke exposure can lead to the accumulation of CD4+ and CD8+ T cells in the alveolar airspaces in a mouse model of COPD, implicating these cells in disease pathogenesis. However, whether specific inhibition of T cell responses represents a therapeutic strategy has not been fully investigated. In this study inhibition of T cell responses through specific depleting antibodies, or the T cell immunosuppressant drug cyclosporin A, prevented airspace enlargement and neutrophil infiltration in a mouse model of chronic cigarette smoke exposure. Furthermore, individual inhibition of either CD4+ T helper or CD8+ T cytotoxic cells prevented airspace enlargement to a similar degree, implicating both T cell subsets as critical mediators of the adaptive immune response induced by cigarette smoke exposure. Importantly, T cell depletion resulted in significantly decreased levels of the Th17-associated cytokine IL-17A, and of caspase 3 and caspase 7 gene expression and activity, induced by cigarette smoke exposure. Finally, inhibition of T cell responses in a therapeutic manner also inhibited cigarette smoke-induced airspace enlargement, IL-17A expression, and neutrophil influx in mice. Together these data demonstrate for the first time that therapeutic inhibition of T cell responses may be efficacious in the treatment of COPD. Given that broad immunosuppression may be undesirable in COPD patients, this study provides proof-of-concept for more targeted approaches to inhibiting the role of T cells in emphysema development.

An observational study of intraoperative transfusion management in a cardiac surgical unit in Trinidad and Tobago

OBJECTIVE

To investigate the intraoperative transfusion requirements in off-pump coronary artery bypass grafting (OPCABG) and the cost implication of blood products and cell savers on a background of limited resources.

METHODS

Prospective data collection identified 60 patients undergoing OPCABG surgery at the Eric Williams Medical Sciences Complex, Trinidad and Tobago. Data relating to these patients (including preoperative haemoglobin (Hb), graft number, presence of diabetes, ejection fraction, preoperative serum creatinine, intraoperative blood use and blood loss) and costing for cell saver disposables and prepared donor (or allogenic) blood were obtained.

RESULTS

Twenty units of packed red blood cells (pRBCs) were given in theatre to 27% (16 of 60) of patients. Transfusion requirement was significantly lower in patients with fewer grafts, higher preoperative Hb level and non-diabetic patients. Cell saver disposables and one unit of pRBCs were estimated to cost TT$5000 and TT$1700, respectively. Each patient's transfusion cost TT$2125.00 per unit.

CONCLUSION

The study demonstrates the financial implications of routine cell saver use in OPCABG in a setting of limited resources. The cost-effectiveness of routine cell saver use remains to be elucidated, but we recommend the selective use of cell savers in patients who are at a higher risk for transfusion.

Nectin ectodomain structures reveal a canonical adhesive interface

Nectins are immunoglobulin superfamily glycoproteins that mediate intercellular adhesion in many vertebrate tissues. Homophilic and heterophilic interactions between nectin family members help to mediate tissue patterning. We determined homophilic binding affinities and heterophilic specificities of all four nectins and the related protein nectin-like 5 from human and mouse, revealing a range of homophilic strengths and a defined heterophilic specificity pattern. To understand the molecular basis of adhesion and specificity, we determined crystal structures of natively glycosylated full ectodomains or adhesive fragments of nectins 1–4 and nectin-like 5. All crystal structures reveal dimeric nectins bound through a stereotyped interface previously proposed to represent a cis dimer. However, conservation of this interface and results of targeted cross-linking experiments show that this dimer likely represents the adhesive trans interaction. Its structure provides a simple molecular explanation for the adhesive binding specificity of nectins.

IL-1β mediates chronic intestinal inflammation by promoting the accumulation of IL-17A secreting innate lymphoid cells and CD4(+) Th17 cells

IL-1β promotes chronic intestinal inflammation through recruitment of granulocytes, activation of ILCs, accumulation of pathogenic T cells, and promotion of Th17 responses.

Although very high levels of interleukin (IL)-1β are present in the intestines of patients suffering from inflammatory bowel diseases (IBD), little is known about the contribution of IL-1β to intestinal pathology. Here, we used two complementary models of chronic intestinal inflammation to address the role of IL-1β in driving innate and adaptive pathology in the intestine. We show that IL-1β promotes innate immune pathology in Helicobacter hepaticus–triggered intestinal inflammation by augmenting the recruitment of granulocytes and the accumulation and activation of innate lymphoid cells (ILCs). Using a T cell transfer colitis model, we demonstrate a key role for T cell–specific IL-1 receptor (IL-1R) signals in the accumulation and survival of pathogenic CD4⁺ T cells in the colon. Furthermore, we show that IL-1β promotes Th17 responses from CD4⁺ T cells and ILCs in the intestine, and we describe synergistic interactions between IL-1β and IL-23 signals that sustain innate and adaptive inflammatory responses in the gut. These data identify multiple mechanisms through which IL-1β promotes intestinal pathology and suggest that targeting IL-1β may represent a useful therapeutic approach in IBD.

Thinking outside the cell: how cadherins drive adhesion

Cadherins are a superfamily of cell surface glycoproteins whose ectodomains contain multiple repeats of β-sandwich extracellular cadherin (EC) domains that adopt a similar fold to immunoglobulin domains. The best characterized cadherins are the vertebrate 'classical' cadherins, which mediate adhesion via trans homodimerization between their membrane-distal EC1 domains that extend from apposed cells, and assemble intercellular adherens junctions through cis clustering. To form mature trans adhesive dimers, cadherin domains from apposed cells dimerize in a 'strand-swapped' conformation. This occurs in a two-step binding process involving a fast-binding intermediate called the 'X-dimer'. Trans dimers are less flexible than cadherin monomers, a factor that drives junction assembly following cell-cell contact by reducing the entropic cost associated with the formation of lateral cis oligomers. Cadherins outside the classical subfamily appear to have evolved distinct adhesive mechanisms that are only now beginning to be understood.

Early intervention in intersigmoid hernia may prevent bowel resection-A case report

INTRODUCTION

Intersigmoid hernia is a rare internal hernia presenting with symptoms of bowel obstruction. Preoperative diagnosis is uncommon but computerised tomography (CT) may show signs to suggest internal hernia.

PRESENTATION OF CASE

A 63-year-old female presented with abdominal pain, vomiting and absolute constipation. Examination revealed a tense distended abdomen. A plain abdominal radiograph showed features of small bowel obstruction. Conservative management was initiated without success and a CT scan was performed which showed a dilated distal oesophagus, stomach and small bowel with a non-dilated length of distal ileum and large bowel. Internal hernia was suggested as a possible cause and the patient underwent a laparotomy where a loop of small bowel was found to be strangulated and gangrenous within the intersigmoid fossa. The gangrenous bowel was resected, an end-to-end anastamosis was performed and the fossa was closed. The patient made an uneventful recovery.

DISCUSSION

Hernias of the sigmoid mesocolon account for 6% of internal hernias with internal hernias themselves causing between 0.2 and 4.1% of intestinal obstruction. This report presents a case of intersigmoid hernia, a rare internal hernia which should be suspected in patients presenting with acute obstruction, no past surgical history and no external hernia. Patients with these symptoms should receive an urgent CT scan to facilitate early surgery and minimise strangulation and prevent bowel resection.

CONCLUSION

Intersigmoid hernia presents with acute obstruction, no past surgical history and no external hernia. Urgent CT scanning and early surgery may minimise strangulation, conserve bowel and reduce patient morbidity and mortality.

Innate immune activation in intestinal homeostasis

Loss of intestinal immune regulation leading to aberrant immune responses to the commensal microbiota are believed to precipitate the chronic inflammation observed in the gastrointestinal tract of patients with inflammatory bowel diseases (IBD), Crohn's disease and ulcerative colitis. Innate immune receptors that recognize conserved components derived from the microbiota are widely expressed by both epithelial cells and leucocytes of the gastrointestinal tract and play a key role in host protection from infectious pathogens; yet precisely how pathogenic and commensal microbes are distinguished is not understood. Furthermore, aberrant innate immune activation may also drive intestinal pathology, as patients with IBD exhibit extensive infiltration of innate immune cells to the inflamed intestine, and polymorphisms in many innate immunity genes influence susceptibility to IBD. Thus, a balanced interaction between the microbiota and innate immune activation is required to maintain a healthy mutualistic relationship between the microbiota and the host, which when disturbed can result in intestinal inflammation.

The extracellular architecture of adherens junctions revealed by crystal structures of type I cadherins

Adherens junctions, which play a central role in intercellular adhesion, comprise clusters of type I classical cadherins that bind via extracellular domains extended from opposing cell surfaces. We show that a molecular layer seen in crystal structures of E- and N-cadherin ectodomains reported here and in a previous C-cadherin structure corresponds to the extracellular architecture of adherens junctions. In all three ectodomain crystals, cadherins dimerize through a trans adhesive interface and are connected by a second, cis, interface. Assemblies formed by E-cadherin ectodomains coated on liposomes also appear to adopt this structure. Fluorescent imaging of junctions formed from wild-type and mutant E-cadherins in cultured cells confirm conclusions derived from structural evidence. Mutations that interfere with the trans interface ablate adhesion, whereas cis interface mutations disrupt stable junction formation. Our observations are consistent with a model for junction assembly involving strong trans and weak cis interactions localized in the ectodomain.

Structure and binding mechanism of vascular endothelial cadherin: a divergent classical cadherin

Vascular endothelial cadherin (VE-cadherin), a divergent member of the type II classical cadherin family of cell adhesion proteins, mediates homophilic adhesion in the vascular endothelium. Previous investigations with a bacterially produced protein suggested that VE-cadherin forms cell surface trimers that bind between apposed cells to form hexamers. Here we report studies of mammalian-produced VE-cadherin ectodomains suggesting that, like other classical cadherins, VE-cadherin forms adhesive trans dimers between monomers located on opposing cell surfaces. Trimerization of the bacterially produced protein appears to be an artifact that arises from a lack of glycosylation. We also present the 2.1-Å-resolution crystal structure of the VE-cadherin EC1-2 adhesive region, which reveals homodimerization via the strand-swap mechanism common to classical cadherins. In common with type II cadherins, strand-swap binding involves two tryptophan anchor residues, but the adhesive interface resembles type I cadherins in that VE-cadherin does not form a large nonswapped hydrophobic surface. Thus, VE-cadherin is an outlier among classical cadherins, with characteristics of both type I and type II subfamilies.

T-cadherin structures reveal a novel adhesive binding mechanism

Vertebrate genomes encode 19 classical cadherins and about 100 nonclassical cadherins. Adhesion by classical cadherins depends on binding interactions in their N-terminal EC1 domains, which swap N-terminal beta-strands between partner molecules from apposing cells. However, strand-swapping sequence signatures are absent from nonclassical cadherins, raising the question of how these proteins function in adhesion. Here, we show that T-cadherin, a glycosylphosphatidylinositol (GPI)-anchored cadherin, forms dimers through an alternative nonswapped interface near the EC1-EC2 calcium-binding sites. Mutations within this interface ablate the adhesive capacity of T-cadherin. These nonadhesive T-cadherin mutants also lose the ability to regulate neurite outgrowth from T-cadherin-expressing neurons. Our findings reveal the likely molecular architecture of the T-cadherin homophilic interface and its requirement for axon outgrowth regulation. The adhesive binding mode used by T-cadherin may also be used by other nonclassical cadherins.