Homeostatic Pathways Research Articles

Physiology and pathophysiology of potassium homeostasis.

Total body potassium content and proper distribution of potassium across the cell membrane is of critical importance for normal cellular function. Potassium homeostasis is maintained by several different methods. In the kidney, total body potassium content is achieved by alterations in renal excretion of potassium in response to variations in intake. Insulin and beta-adrenergic tone play critical roles in maintaining the internal distribution of potassium under normal conditions. Despite homeostatic pathways designed to maintain potassium levels within the normal range, disorders of altered potassium homeostasis are common. The clinical approach to designing effective treatments relies on understanding the pathophysiology and regulatory influences which govern the internal distribution and external balance of potassium. Here we provide an overview of the key regulatory aspects of normal potassium physiology. This review is designed to provide an overview of potassium homeostasis as well as provide references of seminal papers to guide the reader into a more in depth discussion of the importance of potassium balance. This review is designed to be a resource for educators and well-informed clinicians who are teaching trainees about the importance of potassium balance.

Exposure to a Highly Caloric Palatable Diet during the Perinatal Period Affects the Expression of the Endogenous Cannabinoid System in the Brain, Liver and Adipose Tissue of Adult Rat Offspring.

Recent studies have linked gestational exposure to highly caloric diets with a disrupted endogenous cannabinoid system (ECS). In the present study, we have extended these studies by analyzing the impact of the exposure to a palatable diet during gestation and lactation on a) the adult expression of endocannabinoid-related behaviors, b) the metabolic profile of adult offspring and c) the mRNA expression of the signaling machinery of the ECS in the hypothalamus, the liver and the adipose tissue of adult offspring of both sexes. Exposure to a palatable diet resulted in a) sex-dimorphic and perinatal diet specific feeding behaviors, including the differential response to the inhibitory effects of the cannabinoid receptor inverse agonist AM251, b) features of metabolic syndrome including increased adiposity, hyperleptinemia, hypertriglyceridemia and hypercholesterolemia and c) tissue and sex-specific changes in the expression of both CB1 and CB2 receptors and in that of the endocannabinoid-degrading enzymes FAAH and MAGL, being the adipose tissue the most affected organ analyzed. Since the effects were observed in adult animals that were weaned while consuming a normal diet, the present results indicate that the ECS is one of the targets of maternal programming of the offspring energy expenditure. These results clearly indicate that the maternal diet has long-term effects on the development of pups through multiple alterations of signaling homeostatic pathways that include the ECS. The potential relevance of these alterations for the current obesity epidemic is discussed.

Cytokines and intestinal inflammation.

Cytokines of the intestinal microenvironment largely dictate immunological responses after mucosal insults and the dominance of homeostatic or proinflammatory pathways. This review presents important recent studies on the role of specific cytokines in the pathogenesis of intestinal inflammation. The particular mucosal effects of cytokines depend on their inherent properties but also the cellular origin, type of stimulatory antigens, intermolecular interactions, and the particular immunological milieu. Novel cytokines of the interleukin-1 (IL-1) family, including IL-33 and IL-36, have dominant roles in mucosal immunity, whereas more established ones such as IL-18 are constantly enriched with unique properties. Th17 cells are important mucosal constituents, although their profound plasticity, makes the specific set of cytokines they secrete more important than their mere numbers. Finally, various cytokines, such as tumor necrosis factor-α, IL-6, tumor necrosis factor-like cytokine 1A, and death receptor, 3 demonstrate dichotomous roles with mucosa-protective function in acute injury but proinflammatory effects during chronic inflammation. The role of cytokines in mucosal health and disease is increasingly revealed. Such information not only will advance our understanding of the pathogenesis of gut inflammation, but also set the background for development of reliable diagnostic and prognostic biomarkers and cytokine-specific therapies.

Abstract B051: Super cross-presentation of tumor antigens by synthetic design of an anti-phosphatidylserine bridge protein

Abstract Cell loss by apoptosis is a common feature in tumors. Dying tumor cells induce immune tolerance within the tumor microenvironment largely through highly conserved homeostatic clearance programs that restore tissue immune homeostasis and contribute to the formation of an immunosuppressive niche. The translocation of phosphatidylserine (PS) on cellular membranes, during the initial phases of apoptosis, functions as a recognition and removal signal that limits the immunogenicity of cell death. We examined whether altering clearance of dying cancer cells to elicit inflammatory turnover can allow for and potentiate immune responses against tumor cells. To remove inhibitory signals in the homeostatic clearance pathway we utilized a molecular bridge scaffold to engineer a modified phosphatidylserine bridge protein (FA58C2-hIgG1 or C2-hIgG1) that works as a bridge between apoptotic cells expressing aminophospholipids and phagocytes bearing Fc receptors. In vivo administration of C2-hIgG1 partially restores immune responses to dead tumor cells in antigen cross presentation assays and promotes recruitment and retention of tumor antigen specific CD8+ T cells, dendritic cells, and natural killer cells into tumors. These effects combine to elicit anti-lymphoma immunity, improve responses to immune checkpoint inhibitors, and enhance the effectiveness of adoptive T cell transfers using engineered T Cell Receptors (TCRs) but not chimeric antigen receptor engineered (CAR-T) T cells. Citation Format: Daniel Corey, Aaron Ring, Melissa McCracken, Masanori Miyanishi, Sydney Gordon, Irving Weissman. Super cross-presentation of tumor antigens by synthetic design of an anti-phosphatidylserine bridge protein [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr B051.

Micro-management: curbing chronic wound infection.

Chronic wounds, including pressure ulcers, foot ulcers, and venous leg ulcers, have a detrimental impact on the health and well-being of an estimated 2% of people in the UK. Chronic wounds are normally colonized by bacteria and in some instances bacterial load increases sufficiently for infection to ensue. Once a chronic wound becomes infected it is difficult to resolve and a combination of continuous inflammation and bacterial proliferation makes these wounds difficult to manage. A state of prolonged inflammation can occur as a result of impaired homeostatic pathways, which are exacerbated by bacterial growth. Chronic, infected wounds can persist for many months or even years, sometimes requiring surgical intervention in the form of regular debridement or amputation when other strategies such as antimicrobial treatments fail. The complex relationships between both oral microbiota and the host have been extensively characterized, including the shift from health to disease, and this has allowed the development of numerous control strategies. This knowledge, combined with contemporary studies of chronic infected wounds, can be used to develop an understanding of the relationship between the host and microorganism in the chronic wound environment. Such information has the potential to inform wound management including strategies to control infection and promote wound healing.

Acute Gene Expression Profile of Lung Tissue Following Sulfur Mustard Inhalation Exposure in Large Anesthetized Swine.

Sulfur mustard (HD) is a vesicating and alkylating agent widely used on the battlefield during World War I and more recently in the Iran-Iraq War. It targets the eyes, skin, and lungs, producing skin burns, conjunctivitis, and compromised respiratory function; early acute effects lead to long-term consequences. However, it is the effects on the lungs that drive morbidity and eventual mortality. The temporal postexposure response to HD within lung tissue raises the question of whether toxicity is driven by the alkylating properties of HD on critical homeostatic pathways. We have established an anesthetized swine model of inhaled HD vapor exposure to investigate the toxic effects of HD 12 h postexposure. Large white female swine were anesthetized and instrumented prior to exposure to air, 60 (sublethal) or 100 μg·kg-1 (∼LD40) doses of HD (10 min). Physiological parameters were continuously assessed. Data indicate that exposure to 100 μg·kg-1 HD lowered arterial blood oxygenation and increased shunt fraction and lavage protein compared with those of air-exposed controls and the 60 μg·kg-1 dose of HD. Histopathology showed an increased total pathology score between the 100 μg·kg-1 HD group and air-exposed controls. Principal component analysis of differentially expressed genes demonstrated a distinct and separable response of inhaled HD between air-exposed controls and the 60 and 100 μg·kg-1 doses of HD. Canonical pathway analysis demonstrated changes in acute phase response signaling, aryl hydrocarbon receptor signaling, NRF-2 mediated oxidative stress, and zymosterol biosynthesis in the 60 and 100 μg·kg-1 HD dose group. Transcriptional changes also indicated alterations in immune response, cancer, and cell signaling and metabolism canonical pathways. The 100 μg·kg-1 dose group also showed significant changes in cholesterol biosynthesis. Taken together, exposure to inhaled HD had a significant effect on physiological responses coinciding with acute changes in gene expression and lung histopathology. In addition, transcriptomics support the observed beneficial effects of N-acetyl-l-cysteine for treatment of acute inhalation HD exposure.

The Effect of Cellular Stress on T and B Cell Memory Pathways in Immunized and Unimmunized BALB/c Mice

Immunological memory is a fundamental function of vaccination. The antigenic breakdown products of the vaccine may not persist, and undefined tonic stimulation has been proposed to maintain the specific memory. We have suggested that cellular stress agents to which the immune cells are constantly exposed may be responsible for tonic stimulation. Here we have studied four stress agents: sodium arsenite, an oxidative agent; Gramicidin, eliciting K+ efflux and calcium influx; dithiocarbamate, a metal ionophore; and aluminum hydroxide (alum), an immunological adjuvant. The aims of this study are to extend these investigations to T and B cell responses of unimmunized and ovalbumin (OVA)-immunized BALB/c mice, and furthermore, to ascertain whether stress is involved in optimal expression of memory B cells, as demonstrated in CD4+ T cells. Examination of the homeostatic pathway defined by IL-15/IL-15R (IL-15 receptor) interaction and the inflammasome pathway defined by the IL-1-IL-1R interaction between dendritic cells (DC) and CD4+ T cells suggests that both pathways are involved in the development of optimal expression of CD4+CD45RO+ memory T cells in unimmunized and OVA-immunized BALB/c mice. Furthermore, significant direct correlation was found between CD4+CD44+ memory T cells and both IL-15 of the homeostatic and IL-1β of the inflammasome pathways. However, CD19+CD27+ memory B cells in vivo seem to utilize only the IL-15/IL-15R homeostatic pathway, although the proliferative responses are enhanced by the stress agents. Altogether, stress agents may up-regulate unimmunized and OVA-immunized CD4+CD44+ memory T cells by the homeostatic and inflammasome pathways. However, the CD19+CD27+ memory B cells utilize only the homeostatic pathway.

A hexIM1 on your melanocytes: transcription elongation – the Achilles’ heel of melanoma?

A hexIM1 on your melanocytes: transcription elongation – the Achilles’ heel of melanoma?

Transcriptomic response of yeast cells to ATX1 deletion under different copper levels

BackgroundIron and copper homeostatic pathways are tightly linked since copper is required as a cofactor for high affinity iron transport. Atx1p plays an important role in the intracellular copper transport as a copper chaperone transferring copper from the transporters to Ccc2p for its subsequent insertion into Fet3p, which is required for high affinity iron transport.ResultsIn this study, genome-wide transcriptional landscape of ATX1 deletants grown in media either lacking copper or having excess copper was investigated. ATX1 deletants were allowed to recover full respiratory capacity in the presence of excess copper in growth environment. The present study revealed that iron ion homeostasis was not significantly affected by the absence of ATX1 either at the transcriptional or metabolic levels, suggesting other possible roles for Atx1p in addition to its function as a chaperone in copper-dependent iron absorption. The analysis of the transcriptomic response of atx1∆/atx1∆ and its integration with the genetic interaction network highlighted for the first time, the possible role of ATX1 in cell cycle regulation, likewise its mammalian counterpart ATOX1, which was reported to play an important role in the copper-stimulated proliferation of non-small lung cancer cells.ConclusionsThe present finding revealed the dispensability of Atx1p for the transfer of copper ions to Ccc2p and highlighted its possible role in the cell cycle regulation. The results also showed the potential of Saccharomyces cerevisiae as a model organism in studying the capacity of ATOX1 as a therapeutic target for lung cancer therapy.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2771-6) contains supplementary material, which is available to authorized users.

Contingent and non-contingent recreational-like exposure to ethanol alters BDNF expression and signaling in the cortico-accumbal network differently.

Although brain-derived neurotrophic factor (BDNF) is part of a homeostatic pathway involved in the development of alcohol dependence, it is not clear whether this is also true after recreational ethanol consumption. We examined BDNF expression and signaling in the cortico-striatal network immediately and 24h after either a single intravenous (i.v.) ethanol operant self-administration session or the last of 14 sessions. To compare contingent and non-contingent ethanol exposure, we incorporated the "yoked control-operant paradigm" in which rats actively taking ethanol (S-Et) were paired with two yoked controls receiving passive infusions of ethanol (Y-Et) or saline. A single ethanol exposure transiently reduced BDNF mRNA levels in the medial prefrontal cortex (mPFC) of Y-Et. Immediately after the last of 14 sessions, mRNA and mature BDNF protein levels (mBDNF) were reduced in the mPFC in both S-Et and Y-Et while mBDNF expression was raised in the nucleus accumbens (NAc), suggesting enhanced anterograde transport from the mPFC. Conversely, 24h later mBDNF expression and signaling were raised in the mPFC and NAc of S-Et rats but reduced in the NAc of Y-Et rats, with concomitant reduction of downstream signaling pathways. Our findings indicate that recreational-like i.v. doses of ethanol promote early changes in neurotrophin expression, depending on the length and modality of administration, the brain region investigated, and the presence of the drug. A rapid intervention targeting the BDNF system might be useful to prevent escalation to alcohol abuse.

Synaptic and intrinsic homeostasis cooperate to optimize single neuron response properties and tune integrator circuits

Homeostatic processes that provide negative feedback to regulate neuronal firing rate are essential for normal brain function, and observations suggest that multiple such processes may operate simultaneously in the same network. We pose two questions: why might a diversity of homeostatic pathways be necessary, and how can they operate in concert without opposing and undermining each other? To address these questions, we perform a computational and analytical study of cell-intrinsic homeostasis and synaptic homeostasis in single-neuron and recurrent circuit models. We demonstrate analytically and in simulation that when two such mechanisms are controlled on a long time scale by firing rate via simple and general feedback rules, they can robustly operate in tandem to tune the mean and variance of single neuron's firing rate to desired goals. This property allows the system to recover desired behavior after chronic changes in input statistics. We illustrate the power of this homeostatic tuning scheme by using it to regain high mutual information between neuronal input and output after major changes in input statistics. We then show that such dual homeostasis can be applied to tune the behavior of a neural integrator, a system that is notoriously sensitive to variation in parameters. These results are robust to variation in goals and model parameters. We argue that a set of homeostatic processes that appear to redundantly regulate mean firing rate may work together to control firing rate mean and variance and thus maintain performance in a parameter-sensitive task such as integration.

Cholesterol and ORP1L-mediated ER contact sites control autophagosome transport and fusion with the endocytic pathway.

Autophagy is the main homeostatic pathway guiding cytosolic materials for degradation by the lysosome. Maturation of autophagosomes requires their transport towards the perinuclear region of the cell, with key factors underlying both processes still poorly understood. Here we show that transport and positioning of late autophagosomes depends on cholesterol by way of the cholesterol-sensing Rab7 effector ORP1L. ORP1L localizes to late autophagosomes and—under low-cholesterol conditions—contacts the ER protein VAP-A, forming ER-autophagosome contact sites, which prevent minus-end transport by the Rab7–RILP–dynein complex. ORP1L-mediated contact sites also inhibit localization of PLEKHM1 to Rab7. PLEKHM1, together with RILP, then recruits the homotypic fusion and vacuole protein-sorting (HOPS) complex for fusion of autophagosomes with late endosomes and lysosomes. Thus, ORP1L, via its liganding by lipids and the formation of contacts between autophagic vacuoles and the ER, governs the last steps in autophagy that lead to the lysosomal degradation of cytosolic material.

The Genetic Basis of Hydrocephalus.

Studies of syndromic hydrocephalus have led to the identification of >100 causative genes. Even though this work has illuminated numerous pathways associated with hydrocephalus, it has also highlighted the fact that the genetics underlying this phenotype are more complex than anticipated originally. Mendelian forms of hydrocephalus account for a small fraction of the genetic burden, with clear evidence of background-dependent effects of alleles on penetrance and expressivity of driver mutations in key developmental and homeostatic pathways. Here, we synthesize the currently implicated genes and inheritance paradigms underlying hydrocephalus, grouping causal loci into functional modules that affect discrete, albeit partially overlapping, cellular processes. These in turn have the potential to both inform pathomechanism and assist in the rational molecular classification of a clinically heterogeneous phenotype. Finally, we discuss conceptual methods that can lead to enhanced gene identification and dissection of disease basis, knowledge that will potentially form a foundation for the design of future therapeutics.

Catecholamines Facilitate Fuel Expenditure and Protect Against Obesity via a Novel Network of the Gut-Brain Axis in Transcription Factor Skn-1-deficient Mice

Taste signals and nutrient stimuli sensed by the gastrointestinal tract are transmitted to the brain to regulate feeding behavior and energy homeostasis. This system is referred to as the gut-brain axis. Here we show that both brush cells and type II taste cells are eliminated in the gastrointestinal tract of transcription factor Skn-1 knockout (KO) mice. Despite unaltered food intake, Skn-1 KO mice have reduced body weight with lower body fat due to increased energy expenditure. In this model, 24-h urinary excretion of catecholamines was significantly elevated, accompanied by increased fatty acid β-oxidation and fuel dissipation in skeletal muscle and impaired insulin secretion driven by glucose. These results suggest the existence of brain-mediated energy homeostatic pathways originating from brush cells and type II taste cells in the gastrointestinal tract and ending in peripheral tissues, including the adrenal glands. The discovery of food-derived factors that regulate these cells may open new avenues the treatment of obesity and diabetes. Research ContextTaste signals and nutrient stimuli sensed by the gastrointestinal tract are transmitted to the brain to regulate feeding behavior and energy homeostasis along the gut-brain axis. We propose the concept that taste-receiving cells in the oral cavity and/or food-borne chemicals-receiving brush cells in the gut are involved in regulation of the body weight and adiposity via the brain. The discovery of food-derived factors that regulate these cells may open new avenues for the treatment of obesity and diabetes.

Metabolic Profiling of Children Undergoing Surgery for Congenital Heart Disease

Surv Anesthesiol 2016;60(2):70–71 Approximately a third of children who received a diagnosis of congenital heart disease need surgery during early childhood, but these surgical interventions can themselves disrupt homeostatic pathways, ultimately resulting in adverse clinical consequences, including severe organ failure and secondary morbidity. Recent developments in metabolic profiling techniques have shown promise as a means to improve diagnostic accuracy and patient stratification through the identification of metabolic biomarkers of disease risk, severity, and outcome.

Transgenerational programming of longevity and reproduction by post-eclosion dietary manipulation in Drosophila.

Accumulating evidence suggests that early-life diet may program one's health status by causing permanent alternations in specific organs, tissues, or metabolic or homeostatic pathways, and such programming effects may propagate across generations through heritable epigenetic modifications. However, it remains uninvestigated whether postnatal dietary changes may program longevity across generations. To address this question of important biological and public health implications, newly-born flies (F0) were collected and subjected to various post-eclosion dietary manipulations (PDMs) with different protein-carbohydrate (i.e., LP, IP or HP for low-, intermediate- or high-protein) contents or a control diet (CD). Longevity and fecundity analyses were performed with these treated F0 flies and their F1, F2 and F3 offspring, while maintained on CD at all times. The LP and HP PDMs shortened longevity, while the IP PDM extended longevity significantly up to the F3 generation. Furthermore, the LP reduced while the IP PDM increased lifetime fecundity across the F0-F2 generations. Our observations establish the first animal model for studying transgenerational inheritance of nutritional programming of longevity, making it possible to investigate the underlying epigenetic mechanisms and identify gene targets for drug discovery in future studies.

Glucose Availability and AMP-Activated Protein Kinase Link Energy Metabolism and Innate Immunity in the Bovine Endometrium.

Defences against the bacteria that usually infect the endometrium of postpartum cattle are impaired when there is metabolic energy stress, leading to endometritis and infertility. The endometrial response to bacteria depends on innate immunity, with recognition of pathogen-associated molecular patterns stimulating inflammation, characterised by secretion of interleukin (IL)-1β, IL-6 and IL-8. How metabolic stress impacts tissue responses to pathogens is unclear, but integration of energy metabolism and innate immunity means that stressing one system might affect the other. Here we tested the hypothesis that homeostatic pathways integrate energy metabolism and innate immunity in bovine endometrial tissue. Glucose deprivation reduced the secretion of IL-1β, IL-6 and IL-8 from ex vivo organ cultures of bovine endometrium challenged with the pathogen-associated molecular patterns lipopolysaccharide and bacterial lipopeptide. Endometrial inflammatory responses to lipopolysaccharide were also reduced by small molecules that activate or inhibit the intracellular sensor of energy, AMP-activated protein kinase (AMPK). However, inhibition of mammalian target of rapamycin, which is a more global metabolic sensor than AMPK, had little effect on inflammation. Similarly, endometrial inflammatory responses to lipopolysaccharide were not affected by insulin-like growth factor-1, which is an endocrine regulator of metabolism. Interestingly, the inflammatory responses to lipopolysaccharide increased endometrial glucose consumption and induced the Warburg effect, which could exacerbate deficits in glucose availability in the tissue. In conclusion, metabolic energy stress perturbed inflammatory responses to pathogen-associated molecular patterns in bovine endometrial tissue, and the most fundamental regulators of cellular energy, glucose availability and AMPK, had the greatest impact on innate immunity.

Bidirectional crosstalk via IL-6, PGE2 and PGD2 between murine myofibroblasts and alternatively activated macrophages enhances anti-inflammatory phenotype in both cells.

Alternatively activated macrophages (AAMs) are important cells in the resolution of inflammation and tissue repair. We examined the impact of myofibroblasts, a vital cell in wound healing and tissue repair, on the development and function of AAMs. The interaction between AAMs and myofibroblasts was tested using conditioned medium from murine dermal myofibroblasts and bone marrow-derived macrophages. AAMs were differentiated with IL-4 and IL-13. Conditioned medium from myofibroblasts enhanced the expression of AAM markers, arginase 1 and Ym1 (chitinase-3-like 3) and the spontaneous production of IL-10, while suppressing LPS-induced nitric oxide production. IL-6 from the myofibroblasts contributed to the amplification of the AAM phenotype; the selective COX-2 inhibitor, NS-398, significantly reduced the ability of myofibroblasts to promote an AAM phenotype. Pharmacological analyses indicated that myofibroblast-derived IL-6 enhanced arginase activity and spontaneous IL-10 output, while PGE2 , via the EP4 receptor, enhanced arginase expression and LPS-evoked IL-10 production. PGD2 suppressed LPS-evoked nitric oxide via the DP1 receptor. Reciprocally, conditioned medium from macrophages treated with IL-4 + IL-13 and myofibroblast conditioned medium components, but not macrophages given IL-4 + IL-13 only, reduced myofibroblast migration, the expression of COX-2, and the production of PGE2 and PGD2 . These findings define mechanisms by which myofibroblasts enhance an AAM phenotype, which can promote wound healing directly, and/or via feedback communication to the myofibroblast, subsequently down-regulating its capacity to promote AAM function. This is an important homeostatic regulatory pathway in wound healing that can also limit unwanted fibrosis.

TNF biology, pathogenic mechanisms and emerging therapeutic strategies.

TNF is a pleiotropic cytokine with important functions in homeostasis and disease pathogenesis. Recent discoveries have provided insights into TNF biology that introduce new concepts for the development of therapeutics for TNF-mediated diseases. The model of TNF receptor signalling has been extended to include linear ubiquitination and the formation of distinct signalling complexes that are linked with different functional outcomes, such as inflammation, apoptosis and necroptosis. Our understanding of TNF-induced gene expression has been enriched by the discovery of epigenetic mechanisms and concepts related to cellular priming, tolerization and induction of 'short-term transcriptional memory'. Identification of distinct homeostatic or pathogenic TNF-induced signalling pathways has introduced the concept of selectively inhibiting the deleterious effects of TNF while preserving its homeostatic bioactivities for therapeutic purposes. In this Review, we present molecular mechanisms underlying the roles of TNF in homeostasis and inflammatory disease pathogenesis, and discuss novel strategies to advance therapeutic paradigms for the treatment of TNF-mediated diseases.

A Common Progenitor for Macrophages, Osteoclasts and Dendritic Cells Newly Discovered in Human Bone Marrow and Cord Blood Yields Dendritic Cells with T-Cell Priming Ability

Dendritic cells (DC) have potent antigen-presentation and T-cell priming ability and therefore hold great promise in cancer immunotherapy. However, DC vaccination has not yet delivered a reliable clinical response rate, despite great efforts. Since primary DCs are rare (up 0.2-1.5% of circulating leukocytes), therapeutic DCs are generally derived from peripheral blood monocytes by culture with GM-CSF (moDC). Vaccines composed of moDC loaded with tumor antigens can induce potent and long-lasting tumour-specific immune responses in patients, but such positive results are infrequent and unpredictable. To improve success rate, research has focused on moDC culture regimens, antigen loading and activation strategies and methods of DC injection. Nevertheless, to date clinical trials using moDC have not yielded statistically significant treatment benefits over conventional strategies. Current attention has therefore shifted to the rare primary DCs that circulate in the blood under homeostatic conditions.Knowing the identity of the precursors of these DCs may facilitate the ex-vivo or in-vivo generation of DCs via the homeostatic pathway, potentially yielding DCs with optimal T cell priming ability. We (Xiao et al. Stem Cell Rep. 2015) and others (Lee et al. J. Exp. Med. 2015) have recently identified a population with DC progenitor potential in human bone marrow and cord blood, respectively. This population can be isolated on basis of a CD34+ c-KIT+ FLT3+ IL3Rαhigh phenotype and is furthermore Lin- CD10- CD11b- CD45RA+ CD38+. We have shown that this population is highly enriched for or identical to a common progenitor (P) of macrophages (M), osteoclasts (O) and DCs (D) and termed it MODP. We also identified the progenitor directly upstream from the MODP that still has granulocyte (G) differentiation potential and termed it GMODP.We hypothesized that DCs generated from GMODP or MODP under homeostatic conditions would have superb T-cell priming capacity. To examine this, the progenitors were sorted by flow cytometry from human bone marrow or cord blood and cultured with Flt3 ligand, M-CSF and IL-3 to generate DCs. We also tested the effect of a mensenchymal stem cell (MSC) feeder layer. Within 2-3 weeks of culture, 1000 DC progenitors generated approximately 150,000-250,000 DCs. Co-culture with MSC increased DC output significantly, at least 2 fold. The progenitor-derived DCs could be discerned into CD141+ conventional (c)DC, CD1c+ cDC and CD303+ plasmacytoid (p)DC. To study T-cell priming capacity of progenitor-derived DCs, we set up an in vitro DC-T co-culture assay. CD141+ cDC, CD1c+ cDC and CD303+ pDC were generated from GMODP or MODP of HLA-A2+ donors, flow cytometrically purified, activated with lipopolysaccharide and loaded with MART-126-35 peptide that represents a melanoma-derived tumor antigen. Primary T cells from peripheral blood of unrelated donors were retrovirally transduced to express a T cell antigen receptor (TCR) ab specific for the HLA-A2/MART-126-35 peptide complex. The ability of the DCs to prime a T-cell response was read out by antigen-specific CD8+ T cell proliferation. All DC subsets were able to induce MART-1 specific T cell proliferation, with the CD1c+ cDCs being most potent and the CD303+ pDC being least potent.In conclusion: We have established a culture method to derive DCs with T-cell priming ability from a newly identified DC progenitor. These results are of value for improvement of DC-based immunotherapy. DisclosuresNo relevant conflicts of interest to declare.