Physiological concentrations of transforming growth factor beta1 selectively inhibit human dendritic cell function

Extracellular Matrix Profiling and Disease Modelling in Engineered Vascular Smooth Muscle Cell Tissues

Aortic smooth muscle cells (SMCs) have an intrinsic role in regulating vessel homeostasis and pathological remodelling. In two-dimensional (2D) cell culture formats, however, SMCs are not embedded in their physiological extracellular matrix (ECM) environment. To overcome the limitations of conventional 2D SMC cultures, we established a 3D in vitro model of engineered vascular smooth muscle cell tissues (EVTs). EVTs were casted from primary murine aortic SMCs by suspending a SMC-fibrin master mix between two flexible silicon-posts at day 0 before prolonged culture up to 14 days. Immunohistochemical analysis of EVT longitudinal sections demonstrated that SMCs were aligned, viable and secretory. Mass spectrometry-based proteomics analysis of murine EVT lysates was performed and identified 135 matrisome proteins. Proteoglycans, including the large aggregating proteoglycan versican, accumulated within EVTs by day 7 of culture. This was followed by the deposition of collagens, elastin-binding proteins and matrix regulators up to day 14 of culture. In contrast to 2D SMC controls, accumulation of versican occurred in parallel to an increase in versikine, a cleavage product mediated by proteases of the A Disintegrin and Metalloproteinase with Thrombospondin motifs (ADAMTS) family. Next, we tested the response of EVTs to stimulation with transforming growth factor beta-1 (TGFβ-1). EVTs contracted in response to TGFβ-1 stimulation with altered ECM composition. In contrast, treatment with the pharmacological activin-like kinase inhibitor (ALKi) SB 431542 suppressed ECM secretion. As a disease stimulus, we performed calcification assays. The ECM acts as a nidus for calcium phosphate deposition in the arterial wall. We compared the onset and extent of calcification in EVTs and 2D SMCs cultured under high calcium and phosphate conditions for 7 days. Calcified EVTs displayed increased tissue stiffness by up to 30 % compared to non-calcified controls. Unlike the rapid calcification of SMCs in 2D cultures, EVTs sustained expression of the calcification inhibitor matrix Gla protein and allowed for better discrimination of the calcification propensity between independent biological replicates. In summary, EVTs are an intuitive and versatile model to investigate ECM synthesis and turnover by SMCs in a 3D environment. Unlike conventional 2D cultures, EVTs provide a more relevant pathophysiological model for retention of the nascent ECM produced by SMCs.

Synthetic TGF-β Signaling Agonist-Treated Dendritic Cells Induce Tolerogenicity and Antirheumatic Effects

The newly synthesized compound TGF-β signaling agonist (T74) is a small molecule associated with the TGF-β receptor signaling pathway. Tolerogenic dendritic cells (tDCs) have been used to examine immunosuppressive and anti-inflammatory effects in multiple autoimmune disease models. The aim of this study was to investigate whether treatment of DCs with T74 has an antirheumatic effect in a mouse model of collagen-induced arthritis (CIA). Bone marrow-derived cells were obtained from DBA/1J mice and differentiated into DCs. T74-treated DCs (T74-DCs) were generated by treating bone marrow-derived DCs with LPS, type II collagen, and T74. T74-DCs expressed lower levels of surface molecules and inflammatory cytokines associated with antigen presentation and T cell stimulation. The ability of T74-DCs to differentiate effector T cells was lower than that of T74-untreated DCs (NT-DCs), but T74-DCs increased the regulatory T (Treg) cell differentiation in vitro. DBA/1J mice received two subcutaneous (s.c.) injections of type II collagen to establish CIA. Mice then received two s.c. injections of T74-DCs or NT-DCs. Joint inflammation was ameliorated in the paws of T74-DC-treated mice. Additionally, Treg populations in T74-DC-treated mice were higher than in NT-DC-treated or PBS-treated CIA mice. Taken together, these results demonstrate that T74 induces tolerance in DCs, and that T74-mediated DCs exert antirheumatic effects via induction of Tregs.

Interleukin-10 and Transforming Growth Factor-β Cytokines Decrease Immune Activation During Normothermic Ex Vivo Machine Perfusion of the Rat Liver

Normothermic ex vivo liver perfusion (NEVLP) is a novel system for organ preservation that may improve over static cold storage clinically and offers the chance for graft modification prior to transplantation. Although recent studies have shown the presence of inflammatory molecules during perfusion, none have yet shown the effects of NEVLP on liver-resident immune cell activation. We investigated the effects of NEVLP on liver-resident immune cell activation and assessed the ability of anti-inflammatory cytokines interleukin 10 (IL10) and transforming growth factor β (TGF-β) to improve organ function and reduce immune activation during perfusion. Rat livers were perfused for 4 hours at 37°C with or without the addition of 20 ng/mL of each IL10 and TGF-β (n = 7). Naïve and cold storage (4 hours at 4°C) livers served as controls (n = 4). Following preservation, gene expression profiles were assessed through single-cell RNA sequencing; dendritic cell and macrophage activation was measured by flow cytometry; and cytokine production was assessed by enzyme-linked immunosorbent assay. NEVLP induced a global inflammatory gene expression signature, most notably in liver-resident macrophages and dendritic cells, which was accompanied by an increase in cell-surface levels of major histocompatibility complex (MHC) II, CD40, and CD86. Immune activation was partially ameliorated by IL10 and TGF-β treatment, but no changes were observed in inflammatory cytokine production. Overall levels of liver damage and cellular apoptosis from perfusion were low, and liver function was improved with IL10 and TGF-β treatment. This is the first study to demonstrate that liver-resident immune cells gain an activated phenotype during NEVLP on both the gene and protein level and that this activation can be reduced through therapeutic intervention with IL10 and TGF-β.

Helicobacter-stimulated IL-10-producing B cells suppress differentiation of lipopolysaccharide/Helicobacter felis-activated stimulatory dendritic cells

Regulatory B cells (Bregs) produce antiinflammatory cytokines and inhibits proinflammatory response. Recently, immunosuppressive roles of Bregs in the effector functions of dendritic cells (DCs) were demonstrated. However, cross talk between Bregs and DCs in Helicobacter infection remains unknown. Here, we showed that direct stimulation of bone marrow-derived DCs (BM-DCs) with Helicobacter felis (H. felis) antigen upregulates their CD86 surface expression and causes the production of interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), interleukin-12 (IL-12), and interleukin-10 (IL-10). Furthermore, prestimulation of DCs with supernatants derived from both Helicobacter-stimulated IL-10^– B (Hf_stim-IL-10^– B) or IL-10⁺ B (Hf_stim-IL-10⁺) cells suppresses the secretion of TNF-α and IL-6, but does not affect the expression of CD86 and secretion of IL-12 by lipopolysaccharide (LPS) or H. felis-activated BM-DCs. Remarkably, soluble factors secreted by Hf_stim-IL-10^– B cells, but not by Hf_stim-IL-10⁺ B cells, suppress the secretion of IL-10 by BM-DCs upon subsequent LPS stimulation. In contrast, prestimulation with BM-DCs with supernatants of Hf_stim-IL-10⁺ B cells before H. felis antigen stimulation induces significantly their IL-10 production. Collectively, our data indicated that prestimulation with soluble factors secreted by Hf_stim-IL-10⁺ B cells, DCs exhibit a tolerogenic phenotype in response to LPS or Helicobacter antigen by secreting high levels of IL-10, but decreased levels of IL-6 and TNF-α.

Potential Targets to Mitigate Trauma- or Sepsis-Induced Immune Suppression

In sepsis and trauma, pathogens and injured tissue provoke a systemic inflammatory reaction which can lead to overwhelming inflammation. Concurrent with the innate hyperinflammatory response is adaptive immune suppression that can become chronic. A current key issue today is that patients who undergo intensive medical care after sepsis or trauma have a high mortality rate after being discharged. This high mortality is thought to be associated with persistent immunosuppression. Knowledge about the pathophysiology leading to this state remains fragmented. Immunosuppressive cytokines play an essential role in mediating and upholding immunosuppression in these patients. Specifically, the cytokines Interleukin-10 (IL-10), Transforming Growth Factor-β (TGF-β) and Thymic stromal lymphopoietin (TSLP) are reported to have potent immunosuppressive capacities. Here, we review their ability to suppress inflammation, their dynamics in sepsis and trauma and what drives the pathologic release of these cytokines. They do exert paradoxical effects under certain conditions, which makes it necessary to evaluate their functions in the context of dynamic changes post-sepsis and trauma. Several drugs modulating their functions are currently in clinical trials in the treatment of other pathologies. We provide an overview of the current literature on the effects of IL-10, TGF-β and TSLP in sepsis and trauma and suggest therapeutic approaches for their modulation.

Recent Advances in Good Manufacturing Practice-Grade Generation of Dendritic Cells

Dendritic cells (DCs) are pivotal regulators of immune responses, specialized in antigen presentation and bridging the gap between the innate and adaptive immune system. Due to these key features, DCs have become a pillar of the continuously growing field of cellular therapies. Here we review recent advances in good manufacturing practice strategies and their individual specificities in relation to DC production for clinical applications. These take into account both small-scale experimental approaches as well as automated systems for patient care.

Fine-Tuning the TGFβ Signaling Pathway by SARA During Neuronal Development

Neural development is a complex process that involves critical events, including cytoskeleton dynamics and selective trafficking of proteins to defined cellular destinations. In this regard, Smad Anchor for Receptor Activation (SARA) is an early endosome resident protein, where perform trafficking- associated functions. In addition, SARA is also involved in cell signaling, including the TGFβ-dependent pathway. Accordingly, SARA, and TGFβ signaling are required for proper axonal specification and migration of cortical neurons, unveiling a critical role for neuronal development. However, the cooperative action between the TGFβ pathway and SARA to this process has remained understudied. In this work, we show novel evidence suggesting a cross-talk between SARA and TGFβ pathway needed for proper polarization, axonal specification, growth and cortical migration of central neurons both in vitro and in vivo. Using microscopy tools and cultured hippocampal neurons, we show a local interaction between SARA and TβRI (TGFβ I receptor) at endosomes. In addition, SARA loss of function, induced by the expression of the dominant-negative SARA-F728A, over-activates the TGFβ pathway, most likely by preserving phosphorylated TβRI. Consequently, SARA-mediated activation of TGFβ pathway impacts on neuronal development, promoting axonal growth and cortical migration of neurons during brain development. Moreover, our data suggests that SARA basally prevents the activation of TβRI through the recruitment of the inhibitory complex PP1c/GADD34 in polarizing neurons. Together, these results propose that SARA is a negative regulator of the TGFβ pathway, being critical for a proper orchestration for neuronal development.

Antitumor effects of targeting myeloid-derived suppressive cells

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells with major regulatory functions, which are expanded in pathological conditions, including cancers, infections and autoimmune diseases. Evidence has identified MDSCs as critical cells driving immune suppression in tumor microenvironments. Treatments targeting MDSCs have shown promising results in preclinical studies and some clinical trials. In this review, we discuss therapeutic approaches targeting MDSCs, which may benefit future study.

Ex vivo dendritic cell generation-A critical comparison of current approaches

Dendritic cells (DCs) are professional antigen-presenting cells, required for the initiation of naïve and memory T cell responses and regulation of adaptive immunity. The discovery of DCs in 1973, which culminated in the Nobel Prize in Physiology or Medicine in 2011 for Ralph Steinman and colleagues, initially focused on the identification of adherent mononuclear cell fractions with uniquely stellate dendritic morphology, followed by key discoveries of their critical immunologic role in initiating and maintaining antigen-specific immunity and tolerance. The medical promise of marshaling these key capabilities of DCs for therapeutic modulation of antigen-specific immune responses has guided decades of research in hopes to achieve genuine physiologic partnership with the immune system. The potential uses of DCs in immunotherapeutic applications include cancer, infectious diseases, and autoimmune disorders; thus, methods for rapid and reliable large-scale production of DCs have been of great academic and clinical interest. However, difficulties in obtaining DCs from lymphoid and peripheral tissues, low numbers and poor survival in culture, have led to advancements in ex vivo production of DCs, both for probing molecular details of DC function as well as for experimenting with their clinical utility. Here, we review the development of a diverse array of DC production methodologies, ranging from cytokine-based strategies to genetic engineering tools devised for enhancing DC-specific immunologic functions. Further, we explore the current state of DC therapies in clinic, as well as emerging insights into physiologic production of DCs inspired by existing therapies.

Immunosenescence: the potential role of myeloid-derived suppressor cells (MDSC) in age-related immune deficiency

The aging process is associated with chronic low-grade inflammation in both humans and rodents, commonly called inflammaging. At the same time, there is a gradual decline in the functional capacity of adaptive and innate immune systems, i.e., immunosenescence, a process not only linked to the aging process, but also encountered in several pathological conditions involving chronic inflammation. The hallmarks of immunosenescence include a decline in the numbers of naïve CD4+ and CD8+ T cells, an imbalance in the T cell subsets, and a decrease in T cell receptor (TCR) repertoire and signaling. Correspondingly, there is a decline in B cell lymphopoiesis and a reduction in antibody production. The age-related changes are not as profound in innate immunity as they are in adaptive immunity. However, there are distinct functional deficiencies in dendritic cells, natural killer cells, and monocytes/macrophages with aging. Interestingly, the immunosuppression induced by myeloid-derived suppressor cells (MDSC) in diverse inflammatory conditions also targets mainly the T and B cell compartments, i.e., inducing very similar alterations to those present in immunosenescence. Here, we will compare the immune profiles induced by immunosenescence and the MDSC-driven immunosuppression. Given that the appearance of MDSCs significantly increases with aging and MDSCs are the enhancers of other immunosuppressive cells, e.g., regulatory T cells (Tregs) and B cells (Bregs), it seems likely that MDSCs might remodel the immune system, thus preventing excessive inflammation with aging. We propose that MDSCs are potent inducers of immunosenescence.

Bioprinted liver provides early insight into the role of Kupffer cells in TGF-β1 and methotrexate-induced fibrogenesis

Hepatic fibrosis develops from a series of complex interactions among resident and recruited cells making it a challenge to replicate using standard in vitro approaches. While studies have demonstrated the importance of macrophages in fibrogenesis, the role of Kupffer cells (KCs) in modulating the initial response remains elusive. Previous work demonstrated utility of 3D bioprinted liver to recapitulate basic fibrogenic features following treatment with fibrosis-associated agents. In the present study, culture conditions were modified to recapitulate a gradual accumulation of collagen within the tissues over an extended exposure timeframe. Under these conditions, KCs were added to the model to examine their impact on the injury/fibrogenic response following cytokine and drug stimuli. A 28-day exposure to 10 ng/mL TGF-β1 and 0.209 μM methotrexate (MTX) resulted in sustained LDH release which was attenuated when KCs were incorporated in the model. Assessment of miR-122 confirmed early hepatocyte injury in response to TGF-β1 that appeared delayed in the presence of KCs, whereas MTX-induced increases in miR-122 were observed when KCs were incorporated in the model. Although the collagen responses were mild under the conditions tested to mimic early fibrotic injury, a global reduction in cytokines was observed in the KC-modified tissue model following treatment. Furthermore, gene expression profiling suggests KCs have a significant impact on baseline tissue function over time and an important modulatory role dependent on the context of injury. Although the number of differentially expressed genes across treatments was comparable, pathway enrichment suggests distinct, KC- and time-dependent changes in the transcriptome for each agent. As such, the incorporation of KCs and impact on baseline tissue homeostasis may be important in recapitulating temporal dynamics of the fibrogenic response to different agents.

Innate Immune Determinants of Graft-Versus-Host Disease and Bidirectional Immune Tolerance in Allogeneic Transplantation

The success of tissue transplantation from a healthy donor to a diseased individual (allo-transplantation) is regulated by the immune systems of both donor and recipient. Developing a state of specific non-reactivity between donor and recipient, while maintaining the salutary effects of immune function in the recipient, is called “immune (transplantation) tolerance”. In the classic early post-transplant period, minimizing bidirectional donor ←→ recipient reactivity requires the administration of immunosuppressive drugs, which have deleterious side effects (severe immunodeficiency, opportunistic infections, and neoplasia, in addition to drug-specific reactions and organ toxicities). Inducing immune tolerance directly through donor and recipient immune cells, particularly via subsets of immune regulatory cells, has helped to significantly reduce side effects associated with multiple immunosuppressive drugs after allo-transplantation. The innate and adaptive arms of the immune system are both implicated in inducing immune tolerance. In the present article, we will review innate immune subset manipulations and their potential applications in hematopoietic stem cell transplantation (HSCT) to cure malignant and non-malignant hematological disorders by inducing long-lasting donor ←→ recipient (bidirectional) immune tolerance and reduced graft-versus-host disease (GVHD). These innate immunotherapeutic strategies to promote long-term immune allo-transplant tolerance include myeloid-derived suppressor cells (MDSCs), regulatory macrophages, tolerogenic dendritic cells (tDCs), Natural Killer (NK) cells, invariant Natural Killer T (iNKT) cells, gamma delta T (γδ-T) cells and mesenchymal stromal cells (MSCs).

Comparative transcriptomic profile of tolerogenic dendritic cells differentiated with vitamin D3, dexamethasone and rapamycin

Tolerogenic dendritic cell (tolDC)-based therapies have become a promising approach for the treatment of autoimmune diseases by their potential ability to restore immune tolerance in an antigen-specific manner. However, the broad variety of protocols used to generate tolDC in vitro and their functional and phenotypical heterogeneity are evidencing the need to find robust biomarkers as a key point towards their translation into the clinic, as well as better understanding the mechanisms involved in the induction of immune tolerance. With that aim, in this study we have compared the transcriptomic profile of tolDC induced with either vitamin D3 (vitD3-tolDC), dexamethasone (dexa-tolDC) or rapamycin (rapa-tolDC) through a microarray analysis in 5 healthy donors. The results evidenced that common differentially expressed genes could not be found for the three different tolDC protocols. However, individually, CYP24A1, MUCL1 and MAP7 for vitD3-tolDC; CD163, CCL18, C1QB and C1QC for dexa-tolDC; and CNGA1 and CYP7B1 for rapa-tolDC, constituted good candidate biomarkers for each respective cellular product. In addition, a further gene set enrichment analysis of the data revealed that dexa-tolDC and vitD3-tolDC share several immune regulatory and anti-inflammatory pathways, while rapa-tolDC seem to be playing a totally different role towards tolerance induction through a strong immunosuppression of their cellular processes.

Searching for the Transcriptomic Signature of Immune Tolerance Induction-Biomarkers of Safety and Functionality for Tolerogenic Dendritic Cells and Regulatory Macrophages

The last years have witnessed a breakthrough in the development of cell-based tolerance-inducing cell therapies for the treatment of autoimmune diseases and solid-organ transplantation. Indeed, the use of tolerogenic dendritic cells (tolDC) and regulatory macrophages (Mreg) is currently being tested in Phase I and Phase II clinical trials worldwide, with the aim of finding an effective therapy able to abrogate the inflammatory processes causing these pathologies without compromising the protective immunity of the patients. However, there exists a wide variety of different protocols to generate human tolDC and Mreg and, consequently, the characteristics of each product are heterogeneous. For this reason, the identification of biomarkers able to define their functionality (tolerogenicity) is of great relevance, on the one hand, to guarantee the safety of tolDC and Mreg before administration and, on the other hand, to compare the results between different cell products and laboratories. In this article, we perform an exhaustive review of protocols generating human tolDC and Mreg in the literature, aiming to elucidate if there are any common transcriptomic signature or potential biomarkers of tolerogenicity among the different approaches. However, and although several effectors seem to be induced in common in some of the most reported protocols to generate both tolDC or Mreg, the transcriptomic profile of these cellular products strongly varies depending on the approach used to generate them.

Prostaglandin E2 Antagonizes TGF-β Actions During the Differentiation of Monocytes Into Dendritic Cells

Inflammatory dendritic cells (DCs) are a distinct subset of DCs that derive from circulating monocytes infiltrating injured tissues. Monocytes can differentiate into DCs with different functional signatures, depending on the presence of environment stimuli. Among these stimuli, transforming growth factor-beta (TGF-β) and prostaglandin E2 (PGE2) have been shown to modulate the differentiation of monocytes into DCs with different phenotypes and functional profiles. In fact, both mediators lead to contrasting outcomes regarding the production of inflammatory and anti-inflammatory cytokines. Previously, we have shown that human semen, which contains high concentrations of PGE2, promoted the differentiation of DCs into a tolerogenic profile through a mechanism dependent on signaling by E-prostanoid receptors 2 and 4. Notably, this effect was induced despite the huge concentration of TGF-β present in semen, suggesting that PGE2 overrides the influence exerted by TGF-β. No previous studies have analyzed the joint actions induced by PGE2 and TGF-β on the function of monocytes or DCs. Here, we analyzed the phenotype and functional profile of monocyte-derived DCs differentiated in the presence of TGF-β and PGE2. DC differentiation guided by TGF-β alone enhanced the expression of CD1a and abrogated LPS-induced expression of IL-10, while differentiation in the presence of PGE2 impaired CD1a expression, preserved CD14 expression, abrogated IL-12 and IL-23 production, stimulated IL-10 production, and promoted the expansion of FoxP3+ regulatory T cells in a mixed lymphocyte reaction. Interestingly, DCs differentiated in the presence of TGF-β and PGE2 showed a phenotype and functional profile closely resembling those induced by PGE2 alone. Finally, we found that PGE2 inhibited TGF-β signaling through an action exerted by EP2 and EP4 receptors coupled to cyclic AMP increase and protein kinase A activity. These results indicate that PGE2 suppresses the influence exerted by TGF-β during DC differentiation, imprinting a tolerogenic signature. High concentrations of TGF-β and PGE2 are usually found in infectious, autoimmune, and neoplastic diseases. Our observations suggest that in these scenarios PGE2 might play a mandatory role in the acquisition of a regulatory profile by DCs.

Dexamethasone and Monophosphoryl Lipid A Induce a Distinctive Profile on Monocyte-Derived Dendritic Cells through Transcriptional Modulation of Genes Associated With Essential Processes of the Immune Response

There is growing interest in the use of tolerogenic dendritic cells (tolDCs) as a potential target for immunotherapy. However, the molecular bases that drive the differentiation of monocyte-derived DCs (moDCs) toward a tolerogenic state are still poorly understood. Here, we studied the transcriptional profile of moDCs from healthy subjects, modulated with dexamethasone (Dex) and activated with monophosphoryl lipid A (MPLA), referred to as Dex-modulated and MPLA-activated DCs (DM-DCs), as an approach to identify molecular regulators and pathways associated with the induction of tolerogenic properties in tolDCs. We found that DM-DCs exhibit a distinctive transcriptional profile compared to untreated (DCs) and MPLA-matured DCs. Differentially expressed genes downregulated by DM included MMP12, CD1c, IL-1B, and FCER1A involved in DC maturation/inflammation and genes upregulated by DM included JAG1, MERTK, IL-10, and IDO1 involved in tolerance. Genes related to chemotactic responses, cell-to-cell signaling and interaction, fatty acid oxidation, metal homeostasis, and free radical scavenging were strongly enriched, predicting the activation of alternative metabolic processes than those driven by counterpart DCs. Furthermore, we identified a set of genes that were regulated exclusively by the combined action of Dex and MPLA, which are mainly involved in the control of zinc homeostasis and reactive oxygen species production. These data further support the important role of metabolic processes on the control of the DC-driven regulatory immune response. Thus, Dex and MPLA treatments modify gene expression in moDCs by inducing a particular transcriptional profile characterized by the activation of tolerance-associated genes and suppression of the expression of inflammatory genes, conferring the potential to exert regulatory functions and immune response modulation.

Physicochemical regulation of TGF and VEGF delivery from mesoporous calcium phosphate bone substitutes

Aim: Determination of the physicochemical parameters governing growth factors (GFs) adsorption and release from mesoporous calcium phosphate ceramics. Materials & methods: Six mesoporous calcium phosphate ceramics prepared by soft and hard templating were loaded with two different physiological concentrations of TGF-β1 or VEGF165 and their in vitro kinetics of adsorption/release were studied. Results: This low GF loading promotes adsorption on the highest binding sites. The usually encountered detrimental burst release is thus considerably reduced for samples prepared by hard-templating method. Conclusion: Our findings highlight that the strong affinity of GFs with the ceramic surfaces, demonstrated by a slow GFs release, is enhanced by the large surface area, confinement into mesopores of ceramics and high difference of surface charge between ceramic surfaces and GFs.

Regulation of the Immune Response by TGF-β: From Conception to Autoimmunity and Infection

Transforming growth factor β (TGF-β) is a pleiotropic cytokine involved in both suppressive and inflammatory immune responses. After 30 years of intense study, we have only begun to elucidate how TGF-β alters immunity under various conditions. Under steady-state conditions, TGF-β regulates thymic T-cell selection and maintains homeostasis of the naïve T-cell pool. TGF-β inhibits cytotoxic T lymphocyte (CTL), Th1-, and Th2-cell differentiation while promoting peripheral (p)Treg-, Th17-, Th9-, and Tfh-cell generation, and T-cell tissue residence in response to immune challenges. Similarly, TGF-β controls the proliferation, survival, activation, and differentiation of B cells, as well as the development and functions of innate cells, including natural killer (NK) cells, macrophages, dendritic cells, and granulocytes. Collectively, TGF-β plays a pivotal role in maintaining peripheral tolerance against self- and innocuous antigens, such as food, commensal bacteria, and fetal alloantigens, and in controlling immune responses to pathogens.

Treatment with Dexamethasone and Monophosphoryl Lipid A Removes Disease-Associated Transcriptional Signatures in Monocyte-Derived Dendritic Cells from Rheumatoid Arthritis Patients and Confers Tolerogenic Features

Tolerogenic dendritic cells (TolDCs) are promising tools for therapy of autoimmune diseases, such as rheumatoid arthritis (RA). Here, we characterize monocyte-derived TolDCs from RA patients modulated with dexamethasone and activated with monophosphoryl lipid A (MPLA), referred to as MPLA-tDCs, in terms of gene expression, phenotype, cytokine profile, migratory properties, and T cell-stimulatory capacity in order to explore their suitability for cellular therapy. MPLA-tDCs derived from RA patients displayed an anti-inflammatory profile with reduced expression of co-stimulatory molecules and high IL-10/IL-12 ratio, but were capable of migrating toward the lymphoid chemokines CXCL12 and CCL19. These MPLA-tDCs induced hyporesponsiveness of autologous CD4+ T cells specific for synovial antigens in vitro. Global transcriptome analysis confirmed a unique transcriptional profile of MPLA-tDCs and revealed that RA-associated genes, which were upregulated in untreated DCs from RA patients, returned to expression levels of healthy donor-derived DCs after treatment with dexamethasone and MPLA. Thus, monocyte-derived DCs from RA patients have the capacity to develop tolerogenic features at transcriptional as well as at translational level, when modulated with dexamethasone and MPLA, overcoming disease-related effects. Furthermore, the ability of MPLA-tDCs to impair T cell responses to synovial antigens validates their potential as cellular treatment for RA.

Human tolerogenic dendritic cells generated with protein kinase C inhibitor are optimal for functional regulatory T cell induction - A comparative study

Tolerogenic dendritic cells (tDCs) are a promising therapeutic tool for specific induction of immunological tolerance. Human tDCs can be generated ex vivo using various compounds. However, the compound(s) most suitable for clinical application remain undefined. We compared the tolerogenic properties of tDCs treated with protein kinase C inhibitor (PKCI), dexamethasone, vitamin D3 (Vit D3), rapamycin (Rapa), interleukin (IL)-10, transforming growth factor (TGF)-β, and a combination of peroxisome proliferator-activated receptor γ agonist and retinoic acid. All tDCs had a semi-mature DC phenotype. PKCI-, TGF-β-, and Rapa-tDCs showed CCR7 expression and migration to CCL19, but other tDCs showed little or none. PKCI- and IL-10-tDCs induced functional regulatory T cells more strongly than other tDCs. The tolerogenic properties of all tDCs were stable against proinflammatory stimuli. Furthermore, PKCI-tDCs were generated from patients with rheumatoid arthritis and primary Sjögren's syndrome. Therefore, PKCI-tDCs showed the characteristics best suited for tolerance-inducing therapy.

Editor's Highlight: Modeling Compound-Induced Fibrogenesis In Vitro Using Three-Dimensional Bioprinted Human Liver Tissues

Compound-induced liver injury leading to fibrosis remains a challenge for the development of an Adverse Outcome Pathway useful for human risk assessment. Latency to detection and lack of early, systematically detectable biomarkers make it difficult to characterize the dynamic and complex intercellular interactions that occur during progressive liver injury. Here, we demonstrate the utility of bioprinted tissue constructs comprising primary hepatocytes, hepatic stellate cells, and endothelial cells to model methotrexate- and thioacetamide-induced liver injury leading to fibrosis. Repeated, low-concentration exposure to these compounds enabled the detection and differentiation of multiple modes of liver injury, including hepatocellular damage, and progressive fibrogenesis characterized by the deposition and accumulation of fibrillar collagens in patterns analogous to those described in clinical samples obtained from patients with fibrotic liver injury. Transient cytokine production and upregulation of fibrosis-associated genes ACTA2 and COL1A1 mimics hallmark features of a classic wound-healing response. A surge in proinflammatory cytokines (eg, IL-8, IL-1β) during the early culture time period is followed by concentration- and treatment-dependent alterations in immunomodulatory and chemotactic cytokines such as IL-13, IL-6, and MCP-1. These combined data provide strong proof-of-concept that 3D bioprinted liver tissues can recapitulate drug-, chemical-, and TGF-β1-induced fibrogenesis at the cellular, molecular, and histological levels and underscore the value of the model for further exploration of compound-specific fibrogenic responses. This novel system will enable a more comprehensive characterization of key attributes unique to fibrogenic agents during the onset and progression of liver injury as well as mechanistic insights, thus improving compound risk assessment.

Tolerogenic dendritic cells for reprogramming of lymphocyte responses in autoimmune diseases

Dendritic cells (DCs) control immune responses by driving potent inflammatory actions against external and internal threats while generating tolerance to self and harmless components. This duality and their potential to reprogram immune responses in an antigen-specific fashion have made them an interesting target for immunotherapeutic strategies to control autoimmune diseases. Several protocols have been described for in vitro generation of tolerogenic DCs (tolDCs) capable of modulating adaptive immune responses and restoring tolerance through different mechanisms that involve anergy, generation of regulatory lymphocyte populations, or deletion of potentially harmful inflammatory T cell subsets. Recently, the capacity of tolDCs to induce interleukin (IL-10)-secreting regulatory B cells has been demonstrated. In vitro assays and rodent models of autoimmune diseases provide insights to the molecular regulators and pathways enabling tolDCs to control immune responses. Here we review mechanisms through which tolDCs modulate adaptive immune responses, particularly focusing on their suitability for reprogramming autoreactive CD4⁺ effector T cells. Furthermore, we discuss recent findings establishing that tolDCs also modulate B cell populations and discuss clinical trials applying tolDCs to patients with autoimmune diseases.

Phenotypic profile of dendritic and T cells in the lymph node of Balb/C mice with breast cancer submitted to dendritic cells immunotherapy

Breast cancer (BC) is the most common malignant neoplasm and the cause of death by cancer among women worldwide. Its development influenced by various mutations that occur in the tumor cell and by the immune system's status, which has a direct influence on the tumor microenvironment and, consequently, on interactions with non-tumor cells involved in the immunological response. Strategies using dendritic cells (DCs) or antigen-presenting cells (APCs), therapeutic mode, in cancer have been developed for some time. The proper interaction between DCs and T cells upon antigen presentation is of greatest importance for an antitumor immune response activation. Thus, various receptors on the surface of T cells must be able to recognize ligands that are located on the surface of APCs. However, little is known about the real behavior and interaction forms of CDs and T cells after vaccination. Due to the crucial importance of DCs in an effective anti-tumor immune response activation and the search for compliant results in inducing this response by immunotherapies with DCs, the phenotypic profile of DCs and T cells in lymph nodes obtained from female Balb/C mice with breast cancer induced by 4T1 cells and DCs treated with vaccines was investigated. We evaluated through flow cytometry based on the surface and intracellular molecules marking; as well as the presence of cytokines and chemokines, IL-2, IL-4, IL-10, IL-12, IFN-γ, TNF-α and TGF-β in the supernatant of the culture of Balb/C lymph nodes by ELISA. The results show that the vaccination with DCs, in the maturation parameters used in this study, was able to stimulate the secretion of cytokines such as IFN-γ and IL-12 and inhibit the secretion of TGF-β and IL-10 in nodal lymph infiltrates, as well as co-stimulatory activating (CD86) and adhesion molecules in DCs and T cells LFA-1/ICAM-1 and inhibit the secretion of CTLA-4 present in lymph nodes. Facts that led to aTh1 profile polarization, immuno competent in relation to breast cancer. We indirectly evaluated the interaction between DCs and T cells dependent on the vaccination with DCs in tumor draining lymph nodes, in breast cancer in Balb/C mice and we believe that, this way, we will be able to achieve a model vaccine protocol in the future, based on the correct interaction between cells that enable the induction of anti-tumor effective response. Breast cancer (BC) is the most common malignant neoplasm and the cause of death by cancer among women worldwide. Its development influenced by various mutations that occur in the tumor cell and by the immune system's status, which has a direct influence on the tumor microenvironment and, consequently, on interactions with non-tumor cells involved in the immunological response. Strategies using dendritic cells (DCs) or antigen-presenting cells (APCs), therapeutic mode, in cancer have been developed for some time. The proper interaction between DCs and T cells upon antigen presentation is of greatest importance for an antitumor immune response activation. Thus, various receptors on the surface of T cells must be able to recognize ligands that are located on the surface of APCs. However, little is known about the real behavior and interaction forms of DCs and T cells after vaccination. Due to the crucial importance of DCs in an effective anti-tumor immune response activation and the search for compliant results in inducing this response by immunotherapies with DCs, the phenotypic profile of DCs and T cells in lymph nodes obtained from female Balb/C mice with breast cancer induced by 4T1 cells and DCs treated with vaccines was investigated. We evaluated through flow cytometry based on the surface and intracellular molecules marking; as well as the presence of cytokines and chemokines, IL-2, IL-4, IL-10, IL-12, IFN-γ, TNF-α and TGF-β in the supernatant of the culture of Balb/C lymph nodes by ELISA. The results show that the vaccination with DCs, in the maturation parameters used in this study, was able to stimulate the secretion of cytokines such as IFN-γ and IL-12 and inhibit the secretion of TGF-β and IL-10 in nodal lymph infiltrates, as well as co-stimulatory activating (CD86) and adhesion molecules in DCs and T cells LFA-1/ICAM-1 and inhibit the secretion of CTLA-4 present in lymph nodes. Facts that led to aTh1 profile polarization, immuno competent in relation to breast cancer. We indirectly evaluated the interaction between DCs and T cells dependent on the vaccination with DCs in tumor draining lymph nodes, in breast cancer in Balb/C mice and we believe that, this way, we will be able to achieve a model vaccine protocol in the future, based on the correct interaction between cells that enable the induction of anti-tumor effective response.

Tolerogenic Vaccination with MOG/VitD Overcomes Aggravating Effect of C. albicans in Experimental Encephalomyelitis

AIMS

Multiple sclerosis (MS) is an immune-mediated demyelinating disorder of the central nervous system (CNS). We described that Candida albicans (Ca) aggravates experimental autoimmune encephalomyelitis (EAE) that is a model to study MS. We also observed that vaccination with a myelin peptide (MOG) in the presence of vitamin D (VitD) protected mice against EAE. In this work, we investigated whether Ca infection interferes with the efficacy of this vaccine.

METHODS

EAE was induced in C57BL/6 female mice previously vaccinated with MOG+VitD and then infected 3 days before encephalomyelitis induction.

RESULTS

Vaccination was able to control EAE development in infected mice. These animals gained weight, and only a few progressed to very low clinical scores. Protection was confirmed by a lower inflammatory infiltration in the CNS and was also associated with a reduced production of encephalitogenic cytokines by spleen and CNS cell cultures. The elevated percentage of CD25(+) FoxP3(+) cells suggests that regulatory T cells are involved in the protection. Adoptive transfer of splenocytes from mice vaccinated with MOG+VitD supports the view that protection is mediated by immunoregulatory cells.

CONCLUSION

Together, these experiments provide evidence demonstrating that EAE can be prevented by the inverse vaccination with MOG+VitD even in the presence of a disease-aggravating infectious agent.

Gene Expression Profiling of Human Monocyte-derived Dendritic Cells - Searching for Molecular Regulators of Tolerogenicity

The ability of dendritic cells (DCs) to initiate and modulate antigen-specific immune responses has made them attractive targets for immunotherapy. Since DC research in humans is limited by the scarcity of DC populations in the blood circulation, most of our knowledge about DC biology and function has been obtained in vitro from monocyte-derived DCs (moDCs), which can be readily generated in sufficient numbers and are able to differentiate into distinct functional subsets depending on the nature of stimulus. In particular, moDCs with tolerogenic properties (tolDCs) possess great therapeutic potential for the treatment of autoimmune diseases. Several protocols have been developed to generate tolDCs in vitro, able to reinstruct auto-reactive T cells and to promote regulatory cells. While ligands and soluble mediators, by which DCs shape immune responses, have been vastly studied, the intracellular pathways and transcriptional regulators that govern tolDC differentiation and function are poorly understood. Whole-genome microarrays and proteomics provide useful strategies to dissect the complex molecular processes that promote tolerogenicity. Only few attempts have been made to understand tolDC biology through a global view on "omics" profiles. So far, the identification of a common regulator of tolerogenicity has been hampered by the fact that each protocol, used for tolDC generation, targets distinct signaling pathways. Here, we review the progress in understanding the transcriptional regulation of moDC differentiation, with a special focus on tolDCs, and highlight candidate molecules that might be associated with DC tolerogenicity.

Mechanosensitivity of the 2nd Kind: TGF-β Mechanism of Cell Sensing the Substrate Stiffness

Cells can sense forces applied to them, but also the stiffness of their environment. These are two different phenomena, and here we investigate the mechanosensitivity of the 2^nd kind: how the cell can measure an elastic modulus at a single point of adhesion—and how the cell can receive and interpret the chemical signal released from the sensor. Our model uses the example of large latent complex of TGF-β as a sensor. Stochastic theory gives the rate of breaking of latent complex, which initiates the signaling feedback loop after the active TGF-β release and leads to a change of cell phenotype driven by the α-smooth muscle actin. We investigate the dynamic and steady-state behaviors of the model, comparing them with experiments. In particular, we analyse the timescale of approach to the steady state, the stability of the non-linear dynamical system, and how the steady-state concentrations of the key markers vary depending on the elasticity of the substrate. We discover a crossover region for values of substrate elasticity closely corresponding to that of the fibroblast to myofibroblast transition. We suggest that the cell could actively vary the parameters of its dynamic feedback loop to ‘choose’ the position of the transition region and the range of substrate elasticity that it can detect. In this way, the theory offers the unifying mechanism for a variety of phenomena, such as the myofibroblast conversion in fibrosis of wounds and lungs and smooth muscle cell dysfunction in cardiac disease.

Skewing dendritic cell differentiation towards a tolerogenic state for recovery of tolerance in rheumatoid arthritis

To date, the available options to treat autoimmune diseases such as rheumatoid arthritis (RA) include traditional corticoids and biological drugs, which are not exempt of adverse effects. The development of cellular therapies based on dendritic cells with tolerogenic functions (TolDCs) has opened a new possibility to efficiently eradicate symptoms and control the immune response in the field of autoimmunity. TolDCs are an attractive tool for antigen-specific immunotherapy to restore self-tolerance in RA and other autoimmune disorders. A promising strategy is to inject autologous self-antigen-loaded TolDCs, which are able to delete or reprogram autoreactive T cells. Different protocols for the generation of stable human TolDCs have been established and the therapeutic effect of TolDCs has been investigated in multiple rodent models of arthritis. Pilot studies in humans confirmed that TolDC application is safe, encouraging clinical trials using self-antigen-loaded TolDCs in RA patients. Although an abundance of molecular regulators of DC functions has been discovered in the last decade, no master regulator of tolerogenicity has been identified yet. Further research is required to define biomarkers or key regulators of tolerogenicity that might facilitate the induction and monitoring of TolDCs.

TGF-β favors bone marrow-derived dendritic cells to acquire tolerogenic properties

Dendritic cells (DCs) are the most powerful antigen-presenting cells that have an important role in the immunity and immune tolerance. Transforming growth factor β (TGF-β) is a pleiotropic cytokine widely expressing in various tissues and cells, which regulates cellular proliferation, differentiation and apoptosis of several immune cells and is considered to be a key factor in inducing immune tolerance. The effect of TGF-β on DCs is very complex. In this study, we further investigated the effect of TGF-β on inducing immune tolerance of DCs. DCs were differentiated from mice bone marrow cells in the absence or presence of TGF-β. The phenotype as well as function was studied in detail. We found that TGF-β limited the expression of CD40, CD83, CD86 and MHCII in DCs, increased CD45RB and indoleamine 2, 3-dioxygenase (IDO) expression in DCs, promoted IL-10 and limited IL-12 secretion by DCs. Moreover, TGF-β increased the endocytosis ability of DCs and limited the ability of DCs in activating T cells. These results suggest that TGF-β affects the immunity of DCs and enhances their tolerogenicity.

Protein kinase C inhibitor generates stable human tolerogenic dendritic cells

Tolerogenic dendritic cells (DCs) are a promising tool for a specific form of cellular therapy whereby immunological tolerance can be induced in the context of transplantation and autoimmunity. From libraries of bioactive lipids, nuclear receptor ligands, and kinase inhibitors, we screened conventional protein kinase C inhibitors (PKCIs) bisindolylmaleimide I, Gö6983, and Ro32-0432 with strong tolerogenic potential. PKCI-treated human DCs were generated by subjecting them to a maturation process after differentiation of immature DCs. The PKCI-treated DCs had a semimature phenotype, showing high production of IL-10, and efficiently induced IL-10-producing T cells and functional Foxp3(+) regulatory T cells from naive CD4(+) T cells, thus eliciting a strong immunosuppressive function. They also showed CCR7 expression and sufficient capacity for migration toward CCR7 ligands. Additionally, PKCI-treated DCs were highly stable when exposed to inflammatory stimuli such as proinflammatory cytokines or LPS. Conventional PKCIs inhibited NF-κB activation of both the canonical and noncanonical pathways of DC maturation, thus suppressing the expression of costimulatory molecules and IL-12 production. High production of IL-10 in PKCI-treated DCs was due to not only an increase of intracellular cAMP, but also a synergistic effect of increased cAMP and NF-κB inhibition. Moreover, PKCI-treated mouse DCs that had properties similar to PKCI-treated human DCs prevented graft-versus-host disease in a murine model of acute graft-versus-host disease. Conventional PKCI-treated DCs may be useful for tolerance-inducing therapy, as they satisfy the required functional characteristics for clinical-grade tolerogenic DCs.

IL-6 restores dendritic cell maturation inhibited by tumor-derived TGF-β through interfering Smad 2/3 nuclear translocation

We previously found, in a canine transferable tumor model, that high concentration of IL-6 produced by tumor-infiltrating lymphocytes effectively restores the MHC expression of the tumor cells and T-cell activation inhibited by tumor-derived TGF-β. This tumor also significantly suppresses monocyte-derived dendritic cells (DCs) differentiation and the functions of differentiated DCs with unknown mechanisms. In this study, we have demonstrated that a strong reaction of IL-6 was present to neutralize TGF-β-down-regulated surface marker expression on DCs (MHC II, CD1a, CD40, CD80, CD83, CD86), TGF-β-hampered DC functions and DC-associated T-cell activation. Western blotting and confocal microscopy results indicated that the presence of IL-6 markedly decreased the nuclear concentration of a TGF-β signaling transducer, Smad 2/3. In addition, while Smad 7 is a potent molecule inhibiting Smad 2/3 nuclear translocation, no significant increase in Smad 7 gene expression upon addition of IL-6 in TGF-β-pretreated DCs was detected, which suggested that the blockage of Smad 2/3 nuclear translocation by IL-6 did not occur through a Smad 7-inhibitory mechanism. In conclusion, IL-6 inhibited TGF-β signaling and concomitantly antagonized the suppression activities of TGF-β on DC maturation and activity. This study enables further understandings of host/cancer interactions an also provide hints facilitating improvements of DC-based cancer immunotherapy.

IL-10-generated tolerogenic dendritic cells are optimal for functional regulatory T cell induction--a comparative study of human clinical-applicable DC

Tolerogenic dendritic cells (tDC) are a promising tool for specific cellular therapy to induce immunological tolerance in transplantation and autoimmunity. To date, most described tDC methods have not been converted into clinically applicable protocols and systematic comparison of required functional characteristics, i.e. migration and functional regulatory T cell (Treg) induction, is lacking. We compare clinical-grade tDC generated with vitamin D(3), IL-10, dexamethasone, TGFβ or rapamycin. For good migratory capacity and a stable phenotype, additional maturation of tDC was required. Maturation with a cocktail of TNFα, IL-1β and PGE(2) induced optimal migration. Importantly, all tDC showed a stable phenotype under pro-inflammatory conditions. Especially IL-10 DC showed most powerful tolerogenic characteristics with high IL-10 production and low T cell activation. Moreover, in a functional suppression assay only IL-10 DC induced Treg that strongly suppressed T cell reactivity. Thus, clinical-grade IL-10 DC show functional characteristics that make them best suited for tolerance-inducing therapies.

Suppressive effect of aqueous humor on lipopolysaccharide-induced dendritic cell maturation

PURPOSE

The aqueous humor (AH) contains numerous immunosuppressive molecules that contribute to the ocular immune privilege. Here, we mimic an inflammatory environment to analyze the inhibitory effects of the AH on lipopolysaccharide (LPS)-induced maturation of dendritic cells (DC).

METHODS

Different concentrations of AH were added to dendritic cell cultures together with LPS. Dendritic cell surface markers CD80, CD86, and MHC-II were assessed by use of flow cytometry. Endocytic capability and mixed lymphocyte reaction were measured as functional maturation.

RESULTS

AH inhibited LPS-induced DC maturation, resulting in down-regulated expression of CD80, CD86, MHC-II, enhancement of endocytic capacity, and reduced T cell activation. Neutralizing transforming growth factor beta 2 (TGF-β(2)) in AH can totally reverse the inhibitory effect. Treatment with prostaglandin E2 (PGE(2)) antagonist alone had no effect on DC maturation. However, blocking of both TGF-β(2) and PGE(2) in the AH resulted in synergistic suppression of the inhibiting effect of AH.

CONCLUSIONS

These results reveal that TGF-β(2) in the AH is of crucial importance in maintaining DC in the immature state. Further experiments will clarify the immune role of PGE(2) in AH.

Cooperative regulation of NOTCH1 protein-phosphatidylinositol 3-kinase (PI3K) signaling by NOD1, NOD2, and TLR2 receptors renders enhanced refractoriness to transforming growth factor-beta (TGF-beta)- or cytotoxic T-lymphocyte antigen 4 (CTLA-4)-mediated impairment of human dendritic cell maturation

Dendritic cells (DCs) as sentinels of the immune system are important for eliciting both primary and secondary immune responses to a plethora of microbial pathogens. Cooperative stimulation of a complex set of pattern-recognition receptors, including TLR2 and nucleotide-binding oligomerization domain (NOD)-like receptors on DCs, acts as a rate-limiting factor in determining the initiation and mounting of the robust immune response. It underscores the need for "decoding" these multiple receptor interactions. In this study, we demonstrate that TLR2 and NOD receptors cooperatively regulate functional maturation of human DCs. Intriguingly, synergistic stimulation of TLR2 and NOD receptors renders enhanced refractoriness to TGF-β- or CTLA-4-mediated impairment of human DC maturation. Signaling perturbation data suggest that NOTCH1-PI3K signaling dynamics assume critical importance in TLR2- and NOD receptor-mediated surmounting of CTLA-4- and TGF-β-suppressed maturation of human DCs. Interestingly, the NOTCH1-PI3K signaling axis holds the capacity to regulate DC functions by virtue of PKCδ-MAPK-dependent activation of NF-κB. This study provides mechanistic and functional insights into TLR2- and NOD receptor-mediated regulation of DC functions and unravels NOTCH1-PI3K as a signaling cohort for TLR2 and NOD receptors. These findings serve in building a conceptual foundation for the design of improved strategies for adjuvants and immunotherapies against infectious diseases.

IL-37 is a fundamental inhibitor of innate immunity

The function of interleukin 37 (formerly IL-1 family member 7) remains elusive. Expression of IL-37 in macrophages or epithelial cells imparted near complete suppression of pro-inflammatory cytokines, whereas the abundance of these cytokines increased with silencing of endogenous IL-37 in human blood cells. Anti-inflammatory cytokines remained unchanged under similar conditions. IL-37-transgenic mice were protected from lipopolysaccharide-induced shock, exhibiting markedly improved lung and kidney function and reduced liver damage. IL-37-transgenic mice had less circulating and tissue cytokines (72-95% lower) than wild-type mice and exhibited less dendritic cell activation. IL-37 interacted intracellularly with Smad3 and IL-37-expressing cells and transgenic mice exhibited less cytokine suppression when endogenous Smad3 was depleted. IL-37 thus emerges as a natural suppressor of innate inflammatory and immune responses.

HCV+ hepatocytes induce human regulatory CD4+ T cells through the production of TGF-beta

Background

Hepatitis C Virus (HCV) is remarkably efficient at establishing persistent infection and is associated with the development of chronic liver disease. Impaired T cell responses facilitate and maintain persistent HCV infection. Importantly, CD4⁺ regulatory T cells (Tregs) act by dampening antiviral T cell responses in HCV infection. The mechanism for induction and/or expansion of Tregs in HCV is unknown.

Methodology/Principal Findings

HCV-expressing hepatocytes were used to determine if hepatocytes are able to induce Tregs. The infected liver environment was modeled by establishing the co-culture of the human hepatoma cell line, Huh7.5, containing the full-length genome of HCV genotype 1a (Huh7.5-FL) with activated CD4⁺ T cells. The production of IFN-γ was diminished following co-culture with Huh7.5-FL as compared to controls. Notably, CD4⁺ T cells in contact with Huh7.5-FL expressed an increased level of the Treg markers, CD25, Foxp3, CTLA-4 and LAP, and were able to suppress the proliferation of effector T cells. Importantly, HCV⁺ hepatocytes upregulated the production of TGF-β and blockade of TGF-β abrogated Treg phenotype and function.

Conclusions/Significance

These results demonstrate that HCV infected hepatocytes are capable of directly inducing Tregs development and may contribute to impaired host T cell responses.

Decreased small airway and alveolar CD83+ dendritic cells in COPD

BACKGROUND

Dendritic cells (DCs) have been reported to be increased in the small airways of patients with COPD, but the maturity status of these cells is unclear. We have quantified the numbers of cells expressing markers associated with DC maturation.

METHODS

Lung tissue was obtained at resection for lung cancer from 41 patients with COPD (30 current smokers and 11 ex-smokers; 32 steroid-treated patients and 9 steroid-naïve patients), 19 ex-smokers without COPD and 9 never-smokers without COPD. Tissue sections were immunostained for CD1a to mark immature DCs, and for CD83, fascin, and DC-lysosome-associated membrane protein (DC-LAMP) to delineate mature DCs.

RESULTS

The volume density (ie, the volume of DCs as the percentage volume of the airway wall) comprising CD83+ DCs was significantly reduced in patients with COPD (median, 0; range, 0 to 5.1%) vs smokers (median, 2.8%; range, 0 to 10.2%) and never-smokers (median, 1.9%; range, 0.8 to 5.1%) without COPD (p = 0.000 and 0.012, respectively). Using a semiquantitative score for the alveolar wall, CD83+ DCs also were decreased in patients with COPD (median, 0; range, 0 to 2%) vs smokers (median, 1%; range, 0 to 2%) and never-smokers (median, 1%; range, 0.7 to 2%) without COPD (p = 0.004 and 0.04, respectively). No differences were detected in CD83+ DCs between current smokers and ex-smokers with COPD or between steroid-treated and steroid-naive patients. No differences were detected in CD1a+ DCs. Fascin and DC-LAMP were found to have poor specificity for mature DCs.

CONCLUSIONS

COPD is associated with decreased numbers of (mature) CD83+ DCs in small airways and alveoli. The relevance of such a reduction on pulmonary immune responses requires further investigation.

The role of dendritic cells and regulatory T cells in the regulation of allergic asthma

Airways hyperresponsiveness (AHR) is one of the major clinical features of allergic airways disease including allergic asthma, however the immunological mechanisms leading to the induction and regulation of this disorder are not fully understood. In this review we will summarise the evidence of a number of studies, principally in murine models of AHR, suggesting a central role for respiratory tract dendritic cells (RTDC) in the induction of AHR through the generation of lung-homing, allergen-specific effector T cells. We will also summarise the evidence supporting a role for regulatory T cells in the attenuation of AHR and will propose that, as a counterpoint to their capacity to induce AHR, RTDC may also play a role in the attenuation of AHR through the generation of regulatory T cells (T(reg)). A better understanding of the relationship between the physiological and immunological responses to allergen-induced AHR attenuation, and particularly the role of RTDC and T(reg) in this process, will be essential for the development of new treatments and therapies.

TGF-beta1 dampens the susceptibility of dendritic cells to environmental stimulation, leading to the requirement for danger signals for activation

In contrast to its favourable effects on Langerhans cell (LC) differentiation, transforming growth factor (TGF)-beta1 has been reported to prevent dendritic cells from maturing in response to tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta, or lipopolysaccharide (LPS). We first characterized the effects of TGF-beta1 on dendritic cell function by testing the response of TGF-beta1-treated monocyte-derived dendritic cells (MoDCs) to maturation stimuli that LCs receive in the epidermis, namely, haptens, ATP and ultraviolet (UV). TGF-beta1 treatment, which augmented E-cadherin and down-regulated dendritic cell-specific ICAM3-grabbing non-integrin on MoDCs, significantly suppressed their CD86 expression and hapten-induced expression of IL-1beta and TNF-alpha mRNA and protein. As TGF-beta1-treated MoDCs lacked Langerin expression, we demonstrated the suppressive effects of TGF-beta1 on haematopoietic progenitor cell-derived dendritic cells expressing both CD1a and Langerin. These suppressive effects of TGF-beta1 increased with the duration of treatment. Furthermore, TGF-beta1-treated MoDCs became resistant to apoptosis/necrosis induced by high hapten, ATP or UV doses. This was mainly attributable to dampened activation of p38 mitogen-activated protein kinase (MAPK) in TGF-beta1-treated MoDCs. Notably, although ATP or hapten alone could only induce CD86 expression weakly and could not augment the allogeneic T-cell stimulatory function of TGF-beta1-treated MoDCs, ATP and hapten synergized to stimulate these phenotypic and functional changes. Similarly, 2,4-dinitro, 1-chlorobenzene (DNCB) augmented the maturation of TGF-beta1-treated MoDCs upon co-culture with a keratinocyte cell line, in which ATP released by the hapten-stimulated keratinocytes synergized with the hapten to induce their maturation. These data may suggest that TGF-beta1 protects LCs from being overactivated by harmless environmental stimulation, while maintaining their ability to become activated in response to danger signals released by keratinocytes.

[Platelet immunology and the immune response]

Platelets exert not only hemostatic activities, but also pro-inflammatory effects. Platelet-linked inflammation seems essentially related to their capacity of secreting cytokines, chemokines and related molecules. This activity is important in terms of concentration of secreted products. This secretory function confers to platelets a regulatory role in immunity. Besides, platelets do exhibit non-self infectious danger detection molecules on their surfaces, belonging in particular to the "Toll-like receptor family"; through this property, platelets can bind infectious agents but also deliver differential signals for the secretion of cytokines and chemokines. Platelets, which are non-nucleated cells deprived of nuclear DNA, possess however some cellular machinery which permits intracellular signalling and even the production of RNA transcripts for certain cytokines. Last, platelets express variant surface determinants of hemostatic molecules (referred to as HPA antigens) along with HLA class I variant molecules, the function of which on platelets is still unknown. An intriguing question is to reconcile those diverse properties and to understand whether the pro-inflammatory secretory process can affect the immunogenicity of transfused, allogeneic, platelet components.

Immunosuppression associated with interleukin-1R-associated-kinase-M upregulation predicts mortality in Gram-negative sepsis (melioidosis)

OBJECTIVES

Sepsis is associated with immunosuppression (characterized by a reduced capacity of circulating monocytes to release proinflammatory cytokines), which has been implicated in late mortality. Melioidosis, caused by the Gram-negative bacterium Burkholderia pseudomallei, is an important cause of community-acquired sepsis in Southeast Asia with a mortality of up to 40%. Previous in vitro and murine studies have suggested a key role for the so-called negative regulators of the toll-like receptor (TLR) signaling pathway in immunosuppression. In this study, we investigated the expression of these negative TLR regulators in patients with septic melioidosis in association with the responsiveness of peripheral blood leukocytes of these patients to lipopolysaccharide and B. pseudomallei.

DESIGN

Ex vivo study.

SETTING

Academic research laboratory.

PATIENTS

Thirty-two healthy controls and 34 patients with sepsis caused by B. pseudomallei.

INTERVENTIONS

None.

MEASUREMENTS

1) Plasma cytokine levels; 2) ex vivo cytokine production capacity of whole blood; and 3) purified mononuclear cell-derived messenger RNA (mRNA) levels of key inhibitory molecules of the TLR-signaling cascade were investigated.

MAIN RESULTS

In accordance with an immunosuppressed state, whole blood of patients demonstrated a strongly decreased capacity to release the proinflammatory cytokines tumor necrosis factor-[alpha], interleukin-1[beta], and the chemokine interleukin-8 after ex vivo stimulation with lipopolysaccharide or B. pseudomallei. Analysis of myeloid-differentiation-88-short, interleukin-1R-associated-kinase (IRAK)-M, IRAK-1, suppressor-of-cytokine signaling-3, Src-homology-2-domain-containing inositol-5-phosphatase-1, single-immunoglobulin-interleukin-1R-related-molecule, and A20 mRNA expression in purified mononuclear cells showed decreased IRAK-1 and elevated IRAK-M expression in patients with septic melioidosis. Immunosuppression was correlated with mortality; furthermore, patients who eventually died had higher IRAK-M mRNA levels on admission than the patients who survived.

CONCLUSIONS

Immunosuppression in sepsis caused by B. pseudomallei is associated with an upregulation of IRAK-M and an indicator of poor outcome.

Induction of tolerogenic dendritic cells by vitamin D receptor agonists

Dendritic cells induce and regulate T cell responses, and tolerogenic dendritic cells (DCs) can promote the development of regulatory T cells with suppressive activity. Thus, the possibility to manipulate DCs using different pharmacological or biological agents enables them to exert tolerogenic activities, could be exploited to better control a variety of chronic inflammatory conditions, from autoimmune diseases to allograft rejection. A variety of both biological and pharmacological agents can induce tolerogenic DCs, and several in vitro studies have demonstrated that human regulatory T cells can be induced by DCs manipulated to acquire and/or enhance tolerogenic properties, with in vivo data also accumulating. Within this context, we have explored the immunoregulatory activities of vitamin D receptor (VDR) agonists, secosteroid hormones able to induce tolerogenic DCs and regulatory T cells. Tolerogenic DCs induced by a short treatment with VDR agonists promote CD4(+) CD25(+) Foxp3(+) suppressor T cells that are able to mediate transplantation tolerance and to arrest the development of autoimmune diseases. VDR agonists not only favour the induction of CD4(+) CD25(+) regulatory T cells, but can also enhance their recruitment to inflammatory sites. VDR agonists have been proven effective and safe drugs in a variety of autoimmune disease and graft rejection models, highlighting their potential applicability to chronic inflammatory conditions sustained by autoreactive or alloreactive immune responses. In addition to the topical treatment of psoriasis, a Th1-mediated autoimmune disease of the skin where VDR agonists are the most used topical drugs; these agents might eventually find a broader application in the treatment of inflammatory conditions, where their modulatory effects on DCs enhancing T cells with regulatory functions could turn out to be quite beneficial.

Attenuation of allergen-induced airway hyperresponsiveness is mediated by airway regulatory T cells

Understanding the mechanisms involved in respiratory tolerance to inhaled allergens could potentially result in improved therapies for asthma and allergic diseases. Airway hyperresponsiveness (AHR) is a major feature of allergic asthma, thus the aim of the current study was to investigate mechanisms underlying suppression of allergen-induced AHR during chronic allergen exposure. Adult BALB/c mice were systemically sensitized with ovalbumin (OVA) in adjuvant and then challenged with a single 3 or 6 wk of OVA aerosols. Airway and parenchymal responses to inhaled methacholine (MCh), inflammatory cell counts, cytokines, OVA-specific IgE and IgG(1), parenchymal histology, and numbers of airway CD4(+)69(+) activated and CD4(+)25(+)FoxP3(+) regulatory T (Treg) cells were assessed 24 h after the final aerosol. Single OVA challenge resulted in AHR, eosinophilia, increased serum OVA-specific IgE, and T helper 2 (Th2) cytokines in bronchoalveolar lavage (BAL) but no difference in numbers of Treg compared with control mice. Three weeks of OVA challenges resulted in suppression of AHR and greater numbers of airway Treg cells and increased transforming growth factor-beta(1) (TGFbeta(1)) compared with control mice despite the presence of increased eosinophilia, OVA-specific IgE and IgG(1), and airway remodeling. Six weeks of OVA challenges restored AHR, whereas airway Treg numbers, TGFbeta(1), BAL eosinophilia, and Th2 cytokines returned to control levels. Partial in vivo depletion or adoptive transfer of Treg cells restored or inhibited AHR, respectively, but did not affect TGFbeta(1) or Th2 cytokine production. In conclusion, AHR suppression is mediated by airway Treg cells and potentially via a paracrine induction of TGFbeta(1) in the airways.

Transforming growth factor beta up-regulates cysteine-rich protein 2 in vascular smooth muscle cells via activating transcription factor 2

CRP2 (cysteine-rich protein) is a vascular smooth muscle cell (VSMC)-expressed LIM-only protein. CRP2 associates with the actin cytoskeleton and interacts with transcription factors in the nucleus to mediate smooth muscle cell gene expression. Using Csrp2 (gene symbol of the mouse CRP2 gene)-deficient mice, we previously demonstrated that an absence of CRP2 enhances VSMC migration and increases neointima formation following arterial injury. Despite its importance in vascular injury, the molecular mechanisms controlling CRP2 expression in VSMC are largely unknown. Transforming growth factor beta (TGFbeta), a key factor present in the vessel wall in the early phases of arterial response to injury, plays an important role in modulating lesion formation. Because both CRP2 and TGFbeta are mediators of VSMC responses, we examined the possibility that TGFbeta might regulate CRP2 expression. TGFbeta significantly induced CRP2 mRNA and protein expression in VSMCs. Promoter analysis identified a conserved cAMP-responsive element (CRE)-like site (TAACGTCA) in the Csrp2 promoter that was critical for basal promoter activity and response to TGFbeta. Gel mobility shift assays revealed that mainly ATF2 bound to this CRE-like element, and mutation of the CRE sequences abolished binding. TGFbeta enhanced the activation of ATF2, leading to increased phospho-ATF2 levels within the DNA-protein complexes. Furthermore, ATF2-transactivated Csrp2 promoter activity and TGFbeta enhanced this activation. In addition, a phosphorylation-negative ATF2 mutant construct decreased basal and TGFbeta-mediated Csrp2 promoter activity. Our results show for the first time in VSMC that TGFbeta activates ATF2 phosphorylation and Csrp2 gene expression via a CRE promoter element.