First use of a microchip-automated nest box in situ by a brush-tailed phascogale (Phascogale tapoatafa)

Microchip-automated devices have the potential to provide individual free-living animals with safe nesting areas and act as a method of targeted food delivery, while excluding competitors and predators. Wildlife have been successfully trained to use such devices in captivity but never in the wild. Bringing animals into captivity may not always be feasible or appropriate due to the high cost, likely increased stress on the animals, and potential biosecurity risk. Therefore to demonstrate proof of concept that wildlife could be trained in situ to use commercially available microchip-automated devices, a brush-tailed phascogale in the wild was exposed to a microchip-automated door attached to a nest box. The phascogale was successfully trained within 15 days to use the microchip-automated door.

Macrophages acquire a TNF-dependent inflammatory memory in allergic asthma

BACKGROUND

Infectious agents can reprogram or "train" macrophages and their progenitors to respond more readily to subsequent insults. However, whether such an inflammatory memory exists in type-2 inflammatory conditions such as allergic asthma was not known.

OBJECTIVE

To decipher macrophage trained immunity in allergic asthma.

METHODS

We used a combination of clinical sampling of house dust mite (HDM)-allergic patients, HDM-induced allergic airway inflammation (AAI) in mice and an in vitro training set-up to analyze persistent changes in macrophage eicosanoid-, cytokine- and chemokine production as well as underlying metabolic and epigenetic mechanisms. Transcriptional and metabolic profiles of patient-derived and in vitro trained macrophages were assessed by RNA sequencing or Seahorse and LC-MS/MS analysis, respectively.

RESULTS

We found that macrophages differentiated from bone marrow- or blood monocyte- progenitors of HDM-allergic mice or asthma patients show inflammatory transcriptional reprogramming and excessive mediator (TNF-α, CCL17, leukotriene, PGE₂, IL-6) responses upon stimulation. Macrophages from HDM-allergic mice initially exhibited a type-2 imprint, which shifted towards a classical inflammatory training over time. HDM-induced AAI elicited a metabolically activated macrophage phenotype, producing high amounts of 2-hydroxyglutarate (2-HG). HDM-induced macrophage training in vitro was mediated by a formyl-peptide receptor 2 (FPR2)-TNF-2-HG-PGE₂/EP2-axis, resulting in an M2-like macrophage phenotype with high CCL17 production. TNF blockade by etanercept or genetic ablation of Tnf in myeloid cells prevented the inflammatory imprinting of bone marrow-derived macrophages from HDM-allergic mice.

CONCLUSION

Allergen-triggered inflammation drives a TNF-dependent innate memory, which may perpetuate and exacerbate chronic type-2 airway inflammation and thus represents a target for asthma therapy.

Targeting the spliceosome through RBM39 degradation results in exceptional responses in high-risk neuroblastoma models

Aberrant alternative pre-mRNA splicing plays a critical role in MYC-driven cancers and therefore may represent a therapeutic vulnerability. Here, we show that neuroblastoma, a MYC-driven cancer characterized by splicing dysregulation and spliceosomal dependency, requires the splicing factor RBM39 for survival. Indisulam, a “molecular glue” that selectively recruits RBM39 to the CRL4-DCAF15 E3 ubiquitin ligase for proteasomal degradation, is highly efficacious against neuroblastoma, leading to significant responses in multiple high-risk disease models, without overt toxicity. Genetic depletion or indisulam-mediated degradation of RBM39 induces significant genome-wide splicing anomalies and cell death. Mechanistically, the dependency on RBM39 and high-level expression of DCAF15 determine the exquisite sensitivity of neuroblastoma to indisulam. Our data indicate that targeting the dysregulated spliceosome by precisely inhibiting RBM39, a vulnerability in neuroblastoma, is a valid therapeutic strategy.

Do Livestock Injure and Kill Koalas? Insights from Wildlife Hospital and Rescue Group Admissions and an Online Survey of Livestock-Koala Conflicts

Simple Summary

Koala populations in Australia are declining and the species is vulnerable to extinction. In the past decade, grazing livestock emerged anecdotally as a threat to koala survival; cattle and horses were reported to have trampled koalas to death when encountered on the ground. In this study, we investigated the scale, frequency, and outcome of livestock-inflicted incidents to koalas via an online survey, and analysed koala admission records from Queensland wildlife hospitals and a wildlife rescue group (Wildlife Victoria) in Victoria. The results provide evidence of both livestock-inflicted injuries and deaths to koalas, especially as these have been confirmed by witness statements. The outcomes for the koala victims of the incidents were severe, which had a 75% death rate. The reported frequency of livestock–koala incidents was low but increasing, with 72 cases (0.14% out of 50,873 admissions) in Queensland wildlife hospitals during 1997–2019, and 59 cases (0.8% of 7017 rescue records) in Wildlife Victoria during 2007–2019, but it is recognised that this was likely to be under-reported. Future research is encouraged to explore the causes of livestock–koala incidents and to develop management strategies to minimise the livestock threat to koalas.

Abstract

Koala populations in Australia are declining due to threats such as chlamydiosis, wild dog predation and vehicle collision. In the last decade, grazing livestock emerged anecdotally as a threat to koala survival in areas where koala habitat and livestock grazing land overlap. This is the first study investigating the significance of livestock-inflicted injuries and deaths in koala populations over a large spatial and temporal scale. We investigated the outcome, scale, and frequency of livestock–koala incidents via an online survey and analysed koala admission records in Queensland wildlife hospitals and a wildlife rescue group (Wildlife Victoria) in Victoria. The results provide evidence of both livestock-inflicted injuries and deaths to koalas, especially as these have been confirmed by witness statements. The outcomes for the koala victims of the incidents were severe with a 75% mortality rate. The reported frequency of livestock–koala incidents was low but increasing, with 72 cases (0.14% out of 50,873 admissions) in Queensland wildlife hospitals during 1997–2019, and 59 cases (0.8% of 7017 rescue records) in Wildlife Victoria during 2007–2019. These incidents were likely to be under-reported due to the remoteness of the incident location, possible mis-diagnoses by veterinarians and the possible reluctance of farmers to report them. Future research is encouraged to explore the mechanics and causes of livestock–koala incidents and to develop management strategies to minimise the livestock threat to koalas.

Neuroblastoma Formation Requires Unconventional CD4 T Cells and Arginase-1-Dependent Myeloid Cells

Immune cells regulate tumor growth by mirroring their function as tissue repair organizers in normal tissues. To understand the different facets of immune-tumor collaboration through genetics, spatial transcriptomics, and immunologic manipulation with noninvasive, longitudinal imaging, we generated a penetrant double oncogene-driven autochthonous model of neuroblastoma. Spatial transcriptomic analysis showed that CD4⁺ and myeloid populations colocalized within the tumor parenchyma, while CD8⁺ T cells and B cells were peripherally dispersed. Depletion of CD4⁺ T cells or CCR2⁺ macrophages, but not B cells, CD8⁺ T cells, or natural killer (NK) cells, prevented tumor formation. Tumor CD4⁺ T cells displayed unconventional phenotypes and were clonotypically diverse and antigen independent. Within the myeloid fraction, tumor growth required myeloid cells expressing arginase-1. Overall, these results demonstrate how arginine-metabolizing myeloid cells conspire with pathogenic CD4⁺ T cells to create permissive conditions for tumor formation, suggesting that these protumorigenic pathways could be disabled by targeting myeloid arginine metabolism. SIGNIFICANCE: A new model of human neuroblastoma provides ways to track tumor formation and expansion in living animals, allowing identification of CD4⁺ T-cell and macrophage functions required for oncogenesis.

Lactate and IL6 define separable paths of inflammatory metabolic adaptation

Lactate is an end point of Warburg-type metabolism found in inflammatory macrophages. Recently, lactate was shown to modify histones of lipopolysaccharide (LPS)-activated macrophages in a time-dependent way and promote the expression of genes linked to tissue repair, including arginase-1 (Arg1). We tested the interrelationships between histone lactylation (Kla) and tissue reparative gene expression and found that Kla was uncoupled from changes in gene expression linked to resolving M2 macrophage activation but correlated with Arg1 expression. LPS-induced Arg1 was instead dependent on autocrine-paracrine interleukin-6 (IL6) production, the IL6 receptor, and Stat3 signal transduction. We found that Kla increases as macrophages prepare to die under inflammatory stress, and Kla was absent in macrophages that cannot generate reactive nitrogen or have defects in diverse macrophage death pathways. Thus, Kla is a consequence rather than a cause of macrophage activation but occurs coincidently with an IL6- and Arg1-dependent metabolic rewiring under inflammatory duress.

A distinct non-enzymatic role for Indoleamine-2,3-dioxygenase (IDO)2 vs. IDO1 in autoimmune arthritis

IDO1 and IDO2 are closely related immune modulating enzymes encoded by linked genes. Whereas IDO1 is best known for its immunoregulatory role in tumor immune evasion, IDO2 acts as a proinflammatory effector of B cell-mediated autoimmunity. Given their opposing roles in inflammatory responses, interpretation of results obtained using IDO1 or IDO2 single knockout (ko) mice have been complicated by the expression of the other enzyme. Using single and double knockout (dko) mice and the KRN arthritis model, we distinguished differential roles for IDO1 and IDO2 in autoreactive B vs. T cell responses driving arthritis. Both autoreactive T and B cell responses and severity of arthritis were decreased in IDO2, but not IDO1, ko mice. Despite a similar attenuation of disease, only autoreactive B cell responses were reduced in dko mice, demonstrating that IDO2 directly mediates autoreactive B cell responses, while autoreactive T cell responses are indirectly affected by IDO1. Like IDO1, IDO2 was originally identified as a tryptophan catabolizing enzyme. However, we recently showed that the enzymatic activity of IDO2 is not required to drive arthritis. To define the non-enzymatic mechanism mediating IDO2 function, we identified IDO2-interacting proteins using a yeast two-hybrid screen. Specific interaction between IDO2, but not IDO1, and several candidate proteins was confirmed using overexpressing cell lines and co-IP/Western. Using site-directed mutagenesis and an in vitro IDO2-expression model, we identified potential regions outside of the catalytic site on IDO2 that mediate these interactions, providing the first evidence for the non-enzymatic mechanism by which IDO2 mediates proinflammatory B cell responses.

Auto-aggressive CXCR6+ CD8 T cells cause liver immune pathology in NASH

Nonalcoholic steatohepatitis (NASH) is a manifestation of systemic metabolic disease related to obesity, and causes liver disease and cancer^1,2. The accumulation of metabolites leads to cell stress and inflammation in the liver³, but mechanistic understandings of liver damage in NASH are incomplete. Here, using a preclinical mouse model that displays key features of human NASH (hereafter, NASH mice), we found an indispensable role for T cells in liver immunopathology. We detected the hepatic accumulation of CD8 T cells with phenotypes that combined tissue residency (CXCR6) with effector (granzyme) and exhaustion (PD1) characteristics. Liver CXCR6⁺ CD8 T cells were characterized by low activity of the FOXO1 transcription factor, and were abundant in NASH mice and in patients with NASH. Mechanistically, IL-15 induced FOXO1 downregulation and CXCR6 upregulation, which together rendered liver-resident CXCR6⁺ CD8 T cells susceptible to metabolic stimuli (including acetate and extracellular ATP) and collectively triggered auto-aggression. CXCR6⁺ CD8 T cells from the livers of NASH mice or of patients with NASH had similar transcriptional signatures, and showed auto-aggressive killing of cells in an MHC-class-I-independent fashion after signalling through P2X7 purinergic receptors. This killing by auto-aggressive CD8 T cells fundamentally differed from that by antigen-specific cells, which mechanistically distinguishes auto-aggressive and protective T cell immunity.

Cancer metastasis linked to macrophage size, shape, and metabolism

Using macrophage morphology in human colorectal cancer liver metastasis, Donadon et al. in this issue of JEM (https://doi.org/10.1084/jem.20191847) provide a window into lipid metabolism and foamy macrophages, which accrue in numerous pathological states and here are shown to have clinical application.

Anti-ferroptotic mechanism of IL4i1-mediated amino acid metabolism

Interleukin-4-induced-1 (IL4i1) is an amino acid oxidase secreted from immune cells. Recent observations have suggested that IL4i1 is pro-tumorigenic via unknown mechanisms. As IL4i1 has homologs in snake venoms (L-amino acid oxidases [LAAO]), we used comparative approaches to gain insight into the mechanistic basis of how conserved amino acid oxidases regulate cell fate and function. Using mammalian expressed recombinant proteins, we found that venom LAAO kills cells via hydrogen peroxide generation. By contrast, mammalian IL4i1 is non-cytotoxic and instead elicits a cell protective gene expression program inhibiting ferroptotic redox death by generating indole-3-pyruvate (I3P) from tryptophan. I3P suppresses ferroptosis by direct free radical scavenging and through the activation of an anti-oxidative gene expression program. Thus, the pro-tumor effects of IL4i1 are likely mediated by local anti-ferroptotic pathways via aromatic amino acid metabolism, arguing that an IL4i1 inhibitor may modulate tumor cell death pathways.

Tryptophan and indole metabolism in immune regulation

L-tryptophan is an essential amino acid that undergoes complex metabolic routes, resulting in production of many types of signaling molecules that fall into two types: retaining the indole ring such as serotonin, melatonin and indole-pyruvate or breaking the indole ring to form kynurenine. Kynurenines are the precursor of signaling molecules and are the first step in de novo NAD⁺ synthesis. In mammalian cells, the kynurenine pathway is initiated by the rate-limiting enzymes tryptophan-2,3-dioxygenase (TDO) and interferon responsive indoleamine 2,3-dioxygenase (IDO1) and is the major route for tryptophan catabolism. IDO1 regulates immune cell function through the kynurenine pathway but also by depleting tryptophan in microenvironments, and especially in tumors, which led to the development of IDO1 inhibitors for cancer therapy. However, the connections between tryptophan depletion versus product supply remain an ongoing challenge in cellular biochemistry and metabolism. Here, we highlight current knowledge about the physiological and pathological roles of tryptophan signaling network with a focus on the immune system.

How quoll-ified are northern and spotted-tailed quoll detection dogs?

Abstract ContextWildlife detection dogs have been used globally in environmental monitoring. However, their effectiveness in the Australian context has been only minimally researched. Increased understanding of detection dog accuracy and efficacy is required for their inclusion in survey guidelines used by proponents of referred actions potentially impacting Australia’s threatened mammals. Evaluation of new methods is also important for advancing population monitoring, particularly for threatened species. AimsTo determine the efficacy of wildlife detection dogs as a survey tool for low-density, cryptic species, using northern (Dasyurus hallucatus) and spotted-tailed (D. maculatus) quolls as subjects. We compared detection dogs, human search effort and camera trapping results, in simulated accuracy and efficacy trials, and field surveys. MethodsTwo wildlife detection dogs’ scores for sensitivity (ability to identify a target species scat) and specificity (ability to distinguish target from non-target species scats) were calculated during accuracy trials. The dogs were tested using 288 samples, of which 32 were targets, where northern and spotted-tailed quoll scat were the targets in separate trials. Survey efficacy was determined following completing 12 simulated surveys (6 per target species) involving a single, randomly placed scat sample in a 1–1.5ha search area. During the northern quoll simulated surveys the dogs’ survey efficacy was compared with that of a human surveyor. The dogs also undertook field surveys for both northern and spotted-tailed quolls, in conjunction with camera trapping for comparison. Key resultsDuring accuracy trials the dogs had an average sensitivity and specificity respectively of 100% and 98.4% for northern quoll, and 100% and 98% for spotted-tailed quoll. Their average search time in efficacy trials for northern quoll was 11.07min (significantly faster than the human surveyor), and 2.98min for spotted-tailed quoll in the 1–1.5ha search areas. During field surveys, northern quoll scats were detected at sites where camera trapping failed to determine their presence. No spotted-tailed quoll scat was detected by the dogs during field surveys. ConclusionsTrained and experienced detection dogs can work very accurately and efficiently, which is vital to their field success. Detection dogs are therefore capable of detecting evidence of species presence where alternative methods may be unsuccessful. ImplicationsOur study supports the future use of highly trained detection dogs for wildlife surveys and monitoring in Australia. Our results demonstrate that detection dogs can be highly accurate and are a beneficial stand-alone or complimentary method.

Reproductive seasonality and rate of increase of wild sambar deer (Rusa unicolor) in a new environment, Victoria, Australia

Sambar (Rusa unicolor) are the most numerous and rapidly expanding of Australia's six introduced deer species, however, there is little information about the reproductive biology of sambar deer in their natural habitat. To better predict and manage wild sambar populations in Australia it is important to understand their reproductive seasonality and rate of population growth. From results of the present study, there is reporting of field estimates of age at first breeding, reproductive lifespan, juvenile survival, adult bodyweights and fecundity to derive estimates of the current and intrinsic rates of increase for sambar in Victoria, Australia. Mean age of first reproduction was estimated to be 1.8 years, approximately 80 % of hinds calved between April and August, juvenile survival was estimated as 0.81 and age of last reproduction 12.75 years. Seasonality of reproduction is apparently compressed at 36° latitude compared to sambar at the equator indicating a response to photoperiod. Demographic data were used to estimate the current rate of growth of the Victorian population using the two stage Lotke-Euler equation and age-specific schedules of survival and fecundity in a lifetable. These estimates of r were 0.21 and 0.14, respectively, inferring annual rates of population increase of 24 % and 15 %. These data are in the context of a population which, even though there is a marked harvesting, is reportedly growing and dispersing northwards. Suggestions for how this information can inform management decisions directed at the conservation for sustainable use and/or population reduction in Australia are made.

Development of the Mata Hari Judas Queen (Felis catus)

Cats (Felis catus) are significant predators of mammals, birds, frogs and reptiles and are implicated in mammal species extinctions in Australia. Current controls fail to eradicate entire populations allowing survivors to re-establish. The use of the Mata Hari Judas (MHJ) technique, i.e., inducing prolonged oestrus using hormone implants, can enhance the eradication of remnant animals and would greatly improve conservation efforts. The hypotheses tested were that hormone implants could induce prolonged oestrus in queens (adult female cats), and that prolonging oestrus would result in sustained attractiveness to toms (adult male cats). Queens (n = 14) were randomly allocated to five treatments including a control and four treatments using hormone implants. Queens were observed daily; alone and during indirect contact with a tom for 30 consecutive days. There were significant increases (p < 0.001) in oestrus duration (19 to 27 days) for entire and ovariohysterectomised queens given Compudose100™ implants (1/8 or 1/4 implant). This study shows that it is possible to induce and prolong oestrus in queens using Compudose100™ implants where these queens are attractive to toms. The MHJ queen is a new tool with the potential to enhance the detection and thus the control of feral cats in remnant populations.

Cold non-ischemic heart preservation with continuous perfusion prevents early graft failure in orthotopic pig-to-baboon xenotransplantation

BACKGROUND

Successful preclinical transplantations of porcine hearts into baboon recipients are required before commencing clinical trials. Despite years of research, over half of the orthotopic cardiac xenografts were lost during the first 48 hours after transplantation, primarily caused by perioperative cardiac xenograft dysfunction (PCXD). To decrease the rate of PCXD, we adopted a preservation technique of cold non-ischemic perfusion for our ongoing pig-to-baboon cardiac xenotransplantation project.

METHODS

Fourteen orthotopic cardiac xenotransplantation experiments were carried out with genetically modified juvenile pigs (GGTA1- KO/hCD46/hTBM) as donors and captive-bred baboons as recipients. Organ preservation was compared according to the two techniques applied: cold static ischemic cardioplegia (IC; n = 5) and cold non-ischemic continuous perfusion (CP; n = 9) with an oxygenated albumin-containing hyperoncotic cardioplegic solution containing nutrients, erythrocytes and hormones. Prior to surgery, we measured serum levels of preformed anti-non-Gal-antibodies. During surgery, hemodynamic parameters were monitored with transpulmonary thermodilution. Central venous blood gas analyses were taken at regular intervals to estimate oxygen extraction, as well as lactate production. After surgery, we measured troponine T and serum parameters of the recipient's kidney, liver and coagulation functions.

RESULTS

In porcine grafts preserved with IC, we found significantly depressed systolic cardiac function after transplantation which did not recover despite increasing inotropic support. Postoperative oxygen extraction and lactate production were significantly increased. Troponin T, creatinine, aspartate aminotransferase levels were pathologically high, whereas prothrombin ratios were abnormally low. In three of five IC experiments, PCXD developed within 24 hours. By contrast, all nine hearts preserved with CP retained fully preserved systolic function, none showed any signs of PCXD. Oxygen extraction was within normal ranges; serum lactate as well as parameters of organ functions were only mildly elevated. Preformed anti-non-Gal-antibodies were similar in recipients receiving grafts from either IC or CP preservation.

CONCLUSIONS

While standard ischemic cardioplegia solutions have been used with great success in human allotransplantation over many years, our data indicate that they are insufficient for preservation of porcine hearts transplanted into baboons: Ischemic storage caused severe impairment of cardiac function and decreased tissue oxygen supply, leading to multi-organ failure in more than half of the xenotransplantation experiments. In contrast, cold non-ischemic heart preservation with continuous perfusion reliably prevented early graft failure. Consistent survival in the perioperative phase is a prerequisite for preclinical long-term results after cardiac xenotransplantation.

Differential Roles of IDO1 and IDO2 in T and B Cell Inflammatory Immune Responses

Indoleamine-2,3-dioxygenase (IDO)1 and IDO2 are two closely related tryptophan catabolizing enzymes encoded by linked genes. The IDO pathway is also immunomodulatory, with IDO1 well-characterized as a mediator of tumor immune evasion. Due to its homology with IDO1, IDO2 has been proposed to have a similar immunoregulatory function. Indeed, IDO2, like IDO1, is necessary for the differentiation of regulatory T cells in vitro. However, compared to IDO1, in vivo studies demonstrated a contrasting role for IDO2, with experiments in preclinical models of autoimmune arthritis establishing a proinflammatory role for IDO2 in mediating B and T cell activation driving autoimmune disease. Given their potentially opposing roles in inflammatory responses, interpretation of results obtained using IDO1 or IDO2 single knockout mice could be complicated by the expression of the other enzyme. Here we use IDO1 and IDO2 single and double knockout (dko) mice to define the differential roles of IDO1 and IDO2 in B cell-mediated immune responses. Autoreactive T and B cell responses and severity of joint inflammation were decreased in IDO2 ko, but not IDO1 ko arthritic mice. Dko mice had a reduction in the number of autoantibody secreting cells and severity of arthritis: however, percentages of differentiated T cells and their associated cytokines were not reduced compared to IDO1 ko or wild-type mice. These data suggest that autoreactive B cell responses are mediated by IDO2, while autoreactive T cell responses are indirectly affected by IDO1 expression in the IDO2 ko mice. IDO2 also influenced antibody responses in models of influenza infection and immunization with T cell-independent type II antigens. Taken together, these studies provide evidence for the contrasting roles IDO1 and IDO2 play in immune responses, with IDO1 mediating T cell suppressive effects and IDO2 working directly in B cells as a proinflammatory mediator of B cell responses.

Disabled Homolog 2 Controls Prometastatic Activity of Tumor-Associated Macrophages

Tumor-associated macrophages (TAM) are regulators of extracellular matrix (ECM) remodeling and metastatic progression, the main cause of cancer-associated death. We found that disabled homolog 2 mitogen-responsive phosphoprotein (DAB2) is highly expressed in tumor-infiltrating TAMs and that its genetic ablation significantly impairs lung metastasis formation. DAB2-expressing TAMs, mainly localized along the tumor-invasive front, participate in integrin recycling, ECM remodeling, and directional migration in a tridimensional matrix. DAB2⁺ macrophages escort the invasive dissemination of cancer cells by a mechanosensing pathway requiring the transcription factor YAP. In human lobular breast and gastric carcinomas, DAB2⁺ TAMs correlated with a poor clinical outcome, identifying DAB2 as potential prognostic biomarker for stratification of patients with cancer. DAB2 is therefore central for the prometastatic activity of TAMs. SIGNIFICANCE: DAB2 expression in macrophages is essential for metastasis formation but not primary tumor growth. Mechanosensing cues, activating the complex YAP-TAZ, regulate DAB2 in macrophages, which in turn controls integrin recycling and ECM remodeling in 3-D tissue matrix. The presence of DAB2⁺ TAMs in patients with cancer correlates with worse prognosis.This article is highlighted in the In This Issue feature, p. 1611.

Cutting Edge: TNF Is Essential for Mycobacteria-Induced MINCLE Expression, Macrophage Activation, and Th17 Adjuvanticity

TNF blockade is a successful treatment for human autoimmune disorders like rheumatoid arthritis and inflammatory bowel disease yet increases susceptibility to tuberculosis and other infections. The C-type lectin receptors (CLR) MINCLE, MCL, and DECTIN-2 are expressed on myeloid cells and sense mycobacterial cell wall glycolipids. In this study, we show that TNF is sufficient to upregulate MINCLE, MCL, and DECTIN-2 in macrophages. TNF signaling through TNFR1 p55 was required for upregulation of these CLR and for cytokine secretion in macrophages stimulated with the MINCLE ligand trehalose-6,6-dibehenate or infected with Mycobacterium bovis bacillus Calmette-Guérin. The Th17 response to immunization with the MINCLE-dependent adjuvant trehalose-6,6-dibehenate was specifically abrogated in TNF-deficient mice and strongly attenuated by TNF blockade with etanercept. Together, interference with production or signaling of TNF antagonized the expression of DECTIN-2 family CLR, thwarting vaccine responses and possibly increasing infection risk.

Relaxed predation theory: size, sex and brains matter

Australia's wildlife is being considerably impacted by introduced mammalian predators such as cats (Felis catus), dogs (Canis lupus familiaris), and foxes (Vulpes vulpes). This is often attributed to native wildlife being naïve to these introduced predators. A systematic review of the literature reveals that native metatherians (body mass range 0.02-25 kg) do not recognise, and show relaxed antipredator behaviours towards, native and some introduced mammalian predators. Native eutherians (all with body mass < 2 kg), however, do appear to recognise and exhibit antipredator behaviours towards both native and introduced predators. Based on our findings, we propose a novel theory, the 'Relaxed Predation Theory'. Our new theory is based on the absence of large mammalian predators leading to reduced predation pressure in Australia during the past 40000-50000 years, and on three key differences between Australian metatherians and eutherians: size, sex, and brains. In light of this Relaxed Predation Theory, we make a number of recommendations for the conservation of Australian wildlife: (i) predator avoidance training of suitable species; (ii) exclusion fencing to exclude some, but not all, predators to facilitate the development of antipredator behaviours; (iii) captive breeding programs to prevent the extinction of some species; and (iv) reintroduction of Australia's larger predators, potentially to compete with and displace introduced predators. A more detailed understanding of the responses of Australian mammals to predators will hopefully contribute to the improved conservation of susceptible species.

Environmental arginine controls multinuclear giant cell metabolism and formation

Multinucleated giant cells (MGCs) are implicated in many diseases including schistosomiasis, sarcoidosis and arthritis. MGC generation is energy intensive to enforce membrane fusion and cytoplasmic expansion. Using receptor activator of nuclear factor kappa-Β ligand (RANKL) induced osteoclastogenesis to model MGC formation, here we report RANKL cellular programming requires extracellular arginine. Systemic arginine restriction improves outcome in multiple murine arthritis models and its removal induces preosteoclast metabolic quiescence, associated with impaired tricarboxylic acid (TCA) cycle function and metabolite induction. Effects of arginine deprivation on osteoclastogenesis are independent of mTORC1 activity or global transcriptional and translational inhibition. Arginine scarcity also dampens generation of IL-4 induced MGCs. Strikingly, in extracellular arginine absence, both cell types display flexibility as their formation can be restored with select arginine precursors. These data establish how environmental amino acids control the metabolic fate of polykaryons and suggest metabolic ways to manipulate MGC-associated pathologies and bone remodelling.