Secretion of bioactive interleukin-1β by dendritic cells is modulated by interaction with antigen specific T cells

In Silico Identification of Natural Product-Based Inhibitors Targeting IL-1β/IL-1R Protein-Protein Interface

IL-1β mediates inflammation and regulates immune responses, cell proliferation, and differentiation. Dysregulation of IL-1β is linked to inflammatory and autoimmune diseases. Elevated IL-1β levels are found in patients with severe COVID-19, indicating its excessive production may worsen the disease. Also, dry eye disease patients show high IL-1β levels in tears and conjunctival epithelium. Therefore, IL-1β signaling is a potential therapeutic targeting for COVID-19 and aforementioned diseases. No small-molecule IL-1β inhibitor is clinically approved despite efforts. Developing such inhibitors is highly desirable. Herein, a docking-based strategy was used to screen the TCM (Traditional Chinese Medicine) database to identify possible IL-1β inhibitors with desirable pharmacological characteristics by targeting the IL-1β/IL-1R interface. Primarily, the docking-based screening was performed by selecting the crucial residues of IL-1β interface to retrieve the potential compounds. Afterwards, the compounds were shortlisted on the basis of binding scores and significant interactions with the crucial residues of IL-1β. Further, to gain insights into the dynamic behavior of the protein-ligand interactions, MD simulations were performed. The analysis suggests that four selected compounds were stabilized in an IL-1β pocket, possibly blocking the formation of an IL-1β/IL-1R complex. This indicates their potential to interfere with the immune response, making them potential therapeutic agents to investigate further.

scATACpipe: A nextflow pipeline for comprehensive and reproducible analyses of single cell ATAC-seq data

Single cell ATAC-seq (scATAC-seq) has become the most widely used method for profiling open chromatin landscape of heterogeneous cell populations at a single-cell resolution. Although numerous software tools and pipelines have been developed, an easy-to-use, scalable, reproducible, and comprehensive pipeline for scATAC-seq data analyses is still lacking. To fill this gap, we developed scATACpipe, a Nextflow pipeline, for performing comprehensive analyses of scATAC-seq data including extensive quality assessment, preprocessing, dimension reduction, clustering, peak calling, differential accessibility inference, integration with scRNA-seq data, transcription factor activity and footprinting analysis, co-accessibility inference, and cell trajectory prediction. scATACpipe enables users to perform the end-to-end analysis of scATAC-seq data with three sub-workflow options for preprocessing that leverage 10x Genomics Cell Ranger ATAC software, the ultra-fast Chromap procedures, and a set of custom scripts implementing current best practices for scATAC-seq data preprocessing. The pipeline extends the R package ArchR for downstream analysis with added support to any eukaryotic species with an annotated reference genome. Importantly, scATACpipe generates an all-in-one HTML report for the entire analysis and outputs cluster-specific BAM, BED, and BigWig files for visualization in a genome browser. scATACpipe eliminates the need for users to chain different tools together and facilitates reproducible and comprehensive analyses of scATAC-seq data from raw reads to various biological insights with minimal changes of configuration settings for different computing environments or species. By applying it to public datasets, we illustrated the utility, flexibility, versatility, and reliability of our pipeline, and demonstrated that our scATACpipe outperforms other workflows.

Rheumatoid arthritis synovial microenvironment induces metabolic and functional adaptations in dendritic cells

Rheumatoid arthritis (RA) is a chronic autoimmune disease which causes degradation of cartilage and bone. It is well appreciated that the pathogenic hallmark of RA is the mass influx of inflammatory cells into the joint. However, the role that dendritic cells (DC) may play in this inflammatory milieu is still relatively unexplored. Moreover, the contribution this unique synovial microenvironment has on DC maturation is still unknown. Using monocyte-derived DC (MoDC), we established an in-vitro model to recapitulate the synovial microenvironment to explore DC maturation. MoDC treated with conditioned media from ex-vivo synovial tissue biopsy cultures [explant-conditioned media (ECM)] have increased expression of proinflammatory cytokines, chemokines and adhesion molecules. ECM DC have increased expression of CD83 and CC-chemokine receptor (CCR)7 and decreased expression of CCR5 and phagocytic capacity, suggestive of heightened DC maturation. ECM-induced maturation is concomitant with altered cellular bioenergetics, whereby increased expression of glycolytic genes and increased glucose uptake are observed in ECM DC. Collectively, this results in a metabolic shift in DC metabolism in favour of glycolysis. These adaptations are in-part mediated via signal transducer and activator of transcription-3 (STAT-3), as demonstrated by decreased expression of proinflammatory cytokines and glycolytic genes in ECM DC in response to STAT-3 inhibition. Finally, to translate these data to a more in-vivo clinically relevant setting, RNA-seq was performed on RA synovial fluid and peripheral blood. We identified enhanced expression of a number of glycolytic genes in synovial CD1c+ DC compared to CD1c+ DC in circulation. Collectively, our data suggest that the synovial microenvironment in RA contributes to DC maturation and metabolic reprogramming.

Specific targeting of IL-1β activity to CD8+ T cells allows for safe use as a vaccine adjuvant

Annual administration and reformulation of influenza vaccines is required for protection against seasonal infections. However, the induction of strong and long-lasting T cells is critical to reach broad and potentially lifelong antiviral immunity. The NLRP3 inflammasome and its product interleukin-1β (IL-1β) are pivotal mediators of cellular immune responses to influenza, yet, overactivation of these systems leads to side effects, which hamper clinical applications. Here, we present a bypass around these toxicities by targeting the activity of IL-1β to CD8+ T cells. Using this approach, we demonstrate safe inclusion of IL-1β as an adjuvant in vaccination strategies, leading to full protection of mice against a high influenza virus challenge dose by raising potent T cell responses. In conclusion, this paper proposes a class of IL-1β-based vaccine adjuvants and also provides further insight in the mechanics of cellular immune responses driven by IL-1β.

Evolution, role in inflammation, and redox control of leaderless secretory proteins

Members of the interleukin (IL)-1 family are key determinants of inflammation. Despite their role as intercellular mediators, most lack the leader peptide typically required for protein secretion. This lack is a characteristic of dozens of other proteins that are actively and selectively secreted from living cells independently of the classical endoplasmic reticulum-Golgi exocytic route. These proteins, termed leaderless secretory proteins (LLSPs), comprise proteins directly or indirectly involved in inflammation, including cytokines such as IL-1β and IL-18, growth factors such as fibroblast growth factor 2 (FGF2), redox enzymes such as thioredoxin, and proteins most expressed in the brain, some of which participate in the pathogenesis of neurodegenerative disorders. Despite much effort, motifs that promote LLSP secretion remain to be identified. In this review, we summarize the mechanisms and pathophysiological significance of the unconventional secretory pathways that cells use to release LLSPs. We place special emphasis on redox regulation and inflammation, with a focus on IL-1β, which is secreted after processing of its biologically inactive precursor pro-IL-1β in the cytosol. Although LLSP externalization remains poorly understood, some possible mechanisms have emerged. For example, a common feature of LLSP pathways is that they become more active in response to stress and that they involve several distinct excretion mechanisms, including direct plasma membrane translocation, lysosome exocytosis, exosome formation, membrane vesiculation, autophagy, and pyroptosis. Further investigations of unconventional secretory pathways for LLSP secretion may shed light on their evolution and could help advance therapeutic avenues for managing pathological conditions, such as diseases arising from inflammation.

Inhibition of Human Dendritic Cell ER Stress Response Reduces T Cell Alloreactivity Yet Spares Donor Anti-tumor Immunity

Acute graft- vs. -host disease (GVHD) is an important cause of morbidity and death after allogeneic hematopoietic cell transplantation (HCT). We identify a new approach to prevent GVHD that impairs monocyte-derived dendritic cell (moDC) alloactivation of T cells, yet preserves graft- vs.-leukemia (GVL). Exceeding endoplasmic reticulum (ER) capacity results in a spliced form of X-box binding protein-1 (XBP-1s). XBP-1s mediates ER stress and inflammatory responses. We demonstrate that siRNA targeting XBP-1 in moDCs abrogates their stimulation of allogeneic T cells. B-I09, an inositol-requiring enzyme-1α (IRE1α) inhibitor that prevents XBP-1 splicing, reduces human moDC migration, allo-stimulatory potency, and curtails moDC IL-1β, TGFβ, and p40 cytokines, suppressing Th1 and Th17 cell priming. B-I09-treated moDCs reduce responder T cell activation via calcium flux without interfering with regulatory T cell (Treg) function or GVL effects by cytotoxic T lymphocytes (CTL) and NK cells. In a human T cell mediated xenogeneic GVHD model, B-I09 inhibition of XBP-1s reduced target-organ damage and pathogenic Th1 and Th17 cells without impacting donor Tregs or anti-tumor CTL. DC XBP-1s inhibition provides an innovative strategy to prevent GVHD and retain GVL.

RORα controls inflammatory state of human macrophages

ROR family of nuclear receptor transcription factors forms nodes connecting metabolic and inflammatory signaling pathways. The RORα members of the family have intrinsic transcriptional activity and they are involved in both activation and repression of a wide range of genes. The role of RORα in control of inflammation has been extensively studied using animal models but its function in human cells is not as well understood. To address this shortcoming, we analyzed how RORα is shaping the inflammatory state of human macrophages. Using CRISPR-Cas9 system, we deleted RORA in THP-1 human monocytic cell line. In mutant cells we observed a dramatic increase in basal expression of a subset of NF-κB regulated genes, including TNF, IL-1β and IL-6, at both transcriptional and translational levels. Furthermore, RORA-deletion cells produced notable amounts of pro-IL-1β even in the absence of LPS stimulation. Subsequent LPS stimulation induced cleavage of pro-IL-1β to mature form. Our RNAseq analysis further confirmed the key role of RORA in setting the inflammatory state of macrophages and defined the set of differentially regulated genes. Overall, our data provides evidence supporting the anti-inflammatory function of RORα in human macrophages.

The unconventional secretion of IL-1β: Handling a dangerous weapon to optimize inflammatory responses

Interleukin 1β (IL-1β) is a major mediator of inflammation, with a causative role in many diseases. Unlike most other cytokines, however, it lacks a secretory signal sequence, raising intriguing mechanistic, functional and evolutionary questions. Despite decades of strenuous efforts in many laboratories, how IL-1β is secreted is still a matter of intense debate. Here, we summarize the different mechanisms and pathways that have been proposed for IL-1β secretion. At least two of them, namely the endolysosomal vesicle-based and gasdermin D-dependent pathways (types III and I in the recent Rabouille's classification of unconventional protein secretion), can be triggered in monocytes, the main source of IL-1β in humans, according to the type and strength of the pro-inflammatory stimuli. As during the escalation of human conflicts, monocytes deploy secretory mechanisms of increasing efficiency and dangerousness, shifting from the specific and controlled type III pathway to the much faster release of type I. Thus, the different mechanisms are activated depending on the severity of the conditions, from the self-limiting type III pathways in response of low pathogen load or small trauma, to the uncontrolled responses that underlie autoinflammatory disorders and sepsis.

Overview of the IL-1 family in innate inflammation and acquired immunity

The interleukin-1 (IL-1) family of cytokines and receptors is unique in immunology because the IL-1 family and Toll-like receptor (TLR) families share similar functions. More than any other cytokine family, the IL-1 family is primarily associated with innate immunity. More than 95% of living organisms use innate immune mechanisms for survival whereas less than 5% depend on T- and B-cell functions. Innate immunity is manifested by inflammation, which can function as a mechanism of host defense but when uncontrolled is detrimental to survival. Each member of the IL-1 receptor and TLR family contains the cytoplasmic Toll-IL-1-Receptor (TIR) domain. The 50 amino acid TIR domains are highly homologous with the Toll protein in Drosophila. The TIR domain is nearly the same and present in each TLR and each IL-1 receptor family. Whereas IL-1 family cytokine members trigger innate inflammation via IL-1 family of receptors, TLRs trigger inflammation via bacteria, microbial products, viruses, nucleic acids, and damage-associated molecular patterns (DAMPs). In fact, IL-1 family member IL-1a and IL-33 also function as DAMPs. Although the inflammatory properties of the IL-1 family dominate in innate immunity, IL-1 family member can play a role in acquired immunity. This overview is a condensed update of the IL-1 family of cytokines and receptors.

Maternal CD8+ T-cell depletion alleviates intrauterine inflammation-induced perinatal brain injury

We investigated the mechanisms by which CD8⁺ T-cell trafficking in placenta contributes to perinatal brain injury by studying effects of maternal CD8⁺ T-cell depletion (DEP) in a mouse model of intrauterine inflammation (IUI). Maternal CD8⁺ T cells were depleted with anti-CD8⁺ antibodies. IUI was induced with lipopolysaccharide (LPS). DEP was confirmed using flow cytometry. Preterm birth rate was evaluated. Offspring neurologic sequelae were assessed by Nissl staining, immune arrays, confirmatory individual TaqMan^® gene assays, and neurobehavioral tests. DEP did not significantly prevent LPS-induced preterm birth but improved neurobehavioral performance (P < .001) and increased cortical neuronal density (P < .05) in LPS-exposed pups compared to controls. These changes were associated with decreased CCL3 and CXCL10 and increased CCL5 in DEP LPS-exposed mice. We demonstrate that DEP reduces perinatal brain injury following IUI. This supports a role for maternal CD8⁺ T-cell trafficking in placenta in mediating perinatal brain injury separate from preterm birth mechanisms.

Interleukin-1β in innate inflammation, autophagy and immunity

Although IL-1β is the master inflammatory cytokine in the IL-1 family, after more than ten years of continuous breeding, mice deficient in IL-1β exhibit no spontaneous disease. Therefore, one concludes that IL-1β is not needed for homeostasis. However, IL-1β-deficient mice are protected against local and systemic inflammation due to live infections, autoimmune processes, tumor metastasis and even chemical carcinogenesis. Based on a large number of preclinical studies, blocking IL-1β activity in humans with a broad spectrum of inflammatory conditions has reduced disease severity and for many, has lifted the burden of disease. Rare and common diseases are controlled by blocking IL-1β. Immunologically, IL-1β is a natural adjuvant for responses to antigen. Alone, IL-1β is not a growth factor for lymphocytes; rather in antigen activated immunocompetent cells, blocking IL-1 reduces IL-17 production. IL-1β markedly increases in the expansion of naive and memory CD4T cells in response to challenge with their cognate antigen. The response occurs when only specific CD4T cells respond to IL-1β and not to IL-6 or CD-28. A role for autophagy in production of IL-1β has emerged with deletion of the autophagy gene ATG16L1. Macrophages from ATG16L1-deficient mice produce higher levels of IL-1β after stimulation with TLR4 ligands via a mechanism of caspase-1 activation. The implications for increased IL-1β release in persons with defective autophagy may have clinical importance for disease.

The secretion of IL-1β and options for release

Unlike most cytokines, IL-1β lacks a secretory signal sequence raising the question of how is this cytokine processed and delivered outside the producing cells. After the seminal observation that IL-1β is actively secreted by human monocytes through a route alternative to the classic endoplasmic reticulum-Golgi, several different pathways have been proposed for IL-1β secretion in different cell types and culture conditions, some of which are unique to macrophage cell lines. Here we describe the most credited of these pathways. In particular, we will focus on IL-1β secretion from primary human blood monocytes. In fact, although data from macrophages or macrophage cell lines are predominant, secretion of IL-1β by monocytes is the most clinically relevant.

Immunological and inflammatory functions of the interleukin-1 family

More than any other cytokine family, the interleukin (IL)-1 family is closely linked to the innate immune response. This linkage became evident upon the discovery that the cytoplasmic domain of the IL-1 receptor type I is highly homologous to the cytoplasmic domains of all Toll-like receptors (TLRs). Thus, fundamental inflammatory responses such as the induction of cyclooxygenase type 2, increased expression of adhesion molecules, or synthesis of nitric oxide are indistinguishable responses of both IL-1 and TLR ligands. Both families nonspecifically affect antigen recognition and lymphocyte function. IL-1beta is the most studied member of the IL-1 family because of its role in mediating autoinflammatory diseases. Although the TLR and IL-1 families evolved to assist in host defense against infection, unlike the TLR family, the IL-1 family also includes members that suppress inflammation, both specifically within the IL-1 family but also nonspecifically for TLR ligands and the innate immune response.

MicroRNA-155 modulates the interleukin-1 signaling pathway in activated human monocyte-derived dendritic cells

In response to inflammatory stimulation, dendritic cells (DCs) have a remarkable pattern of differentiation (maturation) that exhibits specific mechanisms to control immunity. Here, we show that in response to Lipopolysaccharides (LPS), several microRNAs (miRNAs) are regulated in human monocyte-derived dendritic cells. Among these miRNAs, miR-155 is highly up-regulated during maturation. Using LNA silencing combined to microarray technology, we have identified the Toll-like receptor/interleukin-1 (TLR/IL-1) inflammatory pathway as a general target of miR-155. We further demonstrate that miR-155 directly controls the level of TAB2, an important signal transduction molecule. Our observations suggest, therefore, that in mature human DCs, miR-155 is part of a negative feedback loop, which down-modulates inflammatory cytokine production in response to microbial stimuli.

Expression of IL-1beta, IL-1 receptor type I and IL-1 receptor antagonist in human aortic smooth muscle cells: effects of all-trans-retinoic acid

The proinflammatory cytokine interleukin (IL)-1beta and the IL-1 receptor antagonist are expressed by atherosclerotic plaques and may be linked to the development of atherosclerosis. Existing evidence shows that retinoids and their receptors are involved in inflammatory response and that they are found in atherosclerotic plaques. In all-trans-retinoic acid (atRA)-treated human aortic smooth muscle cells (AOSMC), significant increases in IL-1beta levels were observed, compared with untreated cells. Examination of IL-1 receptor antagonist and IL-1 receptor type I levels did not show any difference between atRA-treated and -untreated AOSMC. The results show that atRA-treated AOSMC express both the precursor (33 kDa) and the active form (17 kDa) of the IL-1beta protein. atRA-treated carotid lesions showed significantly elevated IL-1beta mRNA levels (2.9 +/- 2.33) compared with untreated lesions (2.0 +/- 1.77; p < 0.05). These results support the role of atRA as a regulator of inflammation such as in atherosclerosis.

Histone deacetylase inhibitors prevent exocytosis of interleukin-1beta-containing secretory lysosomes: role of microtubules

A number of agents reducing interleukin-1beta (IL-1beta) activity are being developed as novel immunomodulatory and anti-inflammatory therapies. However, the elucidation of their molecular mechanism of action is required in the context of medical management of inflammatory diseases. Inhibitors of histone deacetylases (HDACs) are promising anticancer agents with pleiotropic activities. Of these, suberoylanilide hydroxamic acid has been reported to inhibit the production of several proinflammatory cytokines. In the present study, we investigated the effects of 2 HDAC inhibitors on IL-1beta secretion: suberoylanilide hydroxamic acid and a newly developed hydroxamic acid-derived compound ITF2357. These HDAC inhibitors do not affect the synthesis or intracellular localization of IL-1beta but both strongly reduce the levels of extracellular IL-1beta by preventing the exocytosis of IL-1beta-containing secretory lysosomes. At nanomolar concentrations, ITF2357 reduces the secretion of IL-1beta following ATP activation of the P2X7 receptor. Whereas the inhibition of HDACs results in hyperacetylation of tubulin, acetylation of HSP90 was unaffected. The reduction in IL-1beta secretion appears to be due to disruption of microtubules impairing lysosome exocytosis. Together, these observations indicate that a functional microtubule network is required for IL-1beta secretion and suggest that disruption of tubulin is the mechanism by which inhibitors of HDACs reduce the secretion of IL-1beta.

NK/iDC interaction results in IL-18 secretion by DCs at the synaptic cleft followed by NK cell activation and release of the DC maturation factor HMGB1

Interaction of natural killer (NK) cells with autologous immature dendritic cells (DCs) results in reciprocal activation; however, the underlying mechanisms are so far elusive. We show here that NK cells trigger immature DCs to polarize and secrete interleukin 18 (IL-18), a cytokine lacking a secretory leader sequence. This occurs through a Ca2+-dependent and tubulin-mediated recruitment of IL-18-containing secretory lysosomes toward the adhering NK cell. Lysosome exocytosis and IL-18 secretion are restricted at the synaptic cleft, thus allowing activation of the interacting NK cells without spreading of the cytokine. In turn, DC-activated NK cells secrete the proinflammatory cytokine high mobility group B1 (HMGB1), which induces DC maturation and protects DCs from lysis. Also HMGB1 is a leaderless cytokine that undergoes regulated secretion. Differently from IL-18, soluble HMGB1 is consistently detected in NK/DC supernatants. These data point to secretion of leaderless cytokines as a key event for the reciprocal activation of NK cells and DCs. DCs initiate NK cell activation by targeted delivery of IL-18, thus instructing NK cells in the absence of adaptive-type cytokines; in turn, activated NK cells release HMGB1, which promotes inflammation and induces DC maturation, thus favoring the onset of the adaptive immune response. (Blood. 2005;106:609-616)

Monocytes promote natural killer cell interferon gamma production in response to the endogenous danger signal HMGB1

Substantial attention has been paid to the role of the toll-like receptor (TLR) ligands of late and their role in regulating the innate immune response. They serve as exogenous danger signals important in informing and driving the distal adaptive immune response to pathogens. Less clear has been the role of the nominal endogenous danger signals released and recognized in stressed cells following genotoxic or metabolic stress as occurs in progressively growing tumors. HMGB1 (high-mobility group B1) is a nuclear protein well characterized for its ability to modify DNA access to transcriptional proteins that is released from necrotic cells as well as secreted through the endosomal route from hematopoietic cells, serving as a late mediator of sepsis. It interacts with high-affinity RAGE (receptor for advanced glycation end products) and TLR2 receptors. Here we show that HMGB1 enhances interferon gamma release from macrophage (but not dendritic cell)-stimulated NK cells. This is effective only when coupled with other pro-inflammatory cytokines particularly with IL-2 in combination with IL-1 or IL-12. We have used this information to suggest that HMGB1, which also promotes epithelial migration and proliferation, drives repair in the absence or inhibition of other factors but enhances inflammation in their presence. The implications for tumorigenesis and tumor progression are quite important as they may be for other states of chronic inflammation.

Role of dendritic cell phenotype, determinant spreading, and negative costimulatory blockade in dendritic cell-based melanoma immunotherapy

MART-1(27-35)-peptide-pulsed immature dendritic cells (DCs) resulted in immunologic and clinical activity in a prior phase 1 trial. A phase 2 cohort expansion was initiated to further characterize the phenotype and cytokine milieu of the DC vaccines and their immunologic activity in vitro and to further examine a possible link between clinical activity and determinant spreading. In an open-label phase 2 trial, 10(7) autologous ex vivo generated DCs pulsed with the HLA-A*0201 immunodominant peptide MART-1(27-35) were administered to 10 subjects with stage II-IV melanoma. The experimental vaccines were administered intradermally in a biweekly schedule for a total of three injections, and blood for immunologic assays was obtained before each administration and at three time points after. DC vaccine preparations had wide intra- and interpatient variability in terms of cell surface markers and preferential cytokine milieu, but they did not correlate with the levels of antigen-specific T cells after vaccination. Of four patients with measurable disease, one had stable disease for 6 months and another has a continued complete response for over 2 years, which is confounded by receiving a closely sequenced CTLA4 blocking antibody. The DC vaccines induced determinant spreading in this subject, and CTLA4 blockade reactivated T cells with prior antigen exposure. The DC phenotype and cytokine profile do not correlate with the ability to induce antigen-specific T cells, while determinant spreading after DC immunization may be a marker of an efficient antitumor response. Sequential CTLA4 blockade may enhance the immune activity of DC-based immunotherapy.

Phospholipases C and A2 control lysosome-mediated IL-1 beta secretion: Implications for inflammatory processes

Blocking the activity of IL-1 beta has entered the clinical arena of treating autoimmune diseases. However, a successful outcome of this approach requires a clear definition of the mechanisms controlling IL-1 beta release. These are still unclear as IL-1 beta, lacking a secretory signal peptide, follows a nonclassical pathway of secretion. Here, we analyze the molecular mechanism(s) undergoing IL-1 beta processing and release in human monocytes and provide a unifying model for the regulated secretion of the cytokine. Our data show that in a first step, pro-caspase-1 and endotoxin-induced pro-IL-1 beta are targeted in part to specialized secretory lysosomes, where they colocalize with other lysosomal proteins. Externalization of mature IL-1 beta and caspase-1 together with lysosomal proteins is then facilitated by extracellular ATP. ATP triggers the efflux of K(+) from the cell, followed by Ca(2+) influx and activation of three phospholipases: phosphatidylcholine-specific phospholipase C and calcium-independent and -dependent phospholipase A(2). Whereas calcium-independent phospholipase A(2) is involved in processing, phosphatidylcholine-specific phospholipase C and calcium-dependent phospholipase A(2) are required for secretion. Dissection of the events that follow ATP triggering allowed to demonstrate that K(+) efflux is responsible for phosphatidylcholine-specific phospholipase C induction, which in turn allows the rise in intracellular free calcium concentration required for activation of phospholipase A(2). This activation is ultimately responsible for lysosome exocytosis and IL-1 beta secretion.

Towards determining the differentiation program of antigen-presenting dendritic cells by transcriptional profiling

Dendritic cells (DC) represent professional antigen-presenting cells that develop from hematopoietic progenitors through successive steps of differentiation. Employing DNA microarray technology, we analysed the specific changes in gene expression that occur when human progenitor cells differentiate into DC. CD34 progenitor cells were first amplified in vitro with stem cell factor (SCF), Flt3 ligand (FL), thrombopoietin and IL-6/soluble IL-6 receptor fusion protein, and cells were then induced to differentiate into DC with IL-4 and GM-CSF. DC maturation was induced by TNFalpha. Progenitor cells and DC were subjected to transcriptional profiling by DNA microarrays that represent 13000 human genes. Our analysis revealed specific changes in the expression of a large number of cell surface antigens including molecules involved in antigen uptake and processing, cell migration and antigen presentation. Genes encoding such molecules were upregulated during DC differentiation as were genes encoding cytokines, cytokine receptors, chemokines and chemokine receptors. Stem cell genes and genes related to the multilineage differentiation potential and proliferative state of progenitor cells were downregulated. Our analysis also provides information on the expression profiles of transcriptional regulators such as the NF-kappaB/rel and STAT transcription factors. Interestingly, NF-kappaB/rel factors were found to be expressed in both progenitor cells and DC at similar levels and were induced by TNFalpha. In contrast, expression of STAT factors increased during DC differentiation and their expression was virtually unaffected by TNFalpha.

Ganglioside GD1a impedes lipopolysaccharide-induced maturation of human dendritic cells

Immunosuppressive membrane gangliosides are released by tumor cells and inhibit normal antigen presenting cell (APC) function. To better understand this process, we have studied the effect of gangliosides on lipopolysaccharide (LPS)-induced maturation of human dendritic cells (DCs). Immature DCs were generated in vitro from human peripheral blood monocytes and were exposed for 72 h to a highly purified ganglioside, G(D1a). During the last 24 h, LPS was added to effect maturation. As assessed by fluorescence activated cell sorting (FACS) analysis, incubation in 50 microM G(D1a) significantly blunted the LPS-induced maturation of the dendritic cells. The expected up-regulation of expression of the co-stimulatory molecules CD80 and CD86 was ablated and that of CD40 was reduced, as were surface CD83 expression and intracellular CD208 production. In addition, ganglioside pretreatment of DC markedly inhibited the allostimulatory capacity and partially prevented the down-regulation of FITC-dextran uptake characteristic of LPS-activated DC. Furthermore, ganglioside-exposed DC also evidenced a broad down-regulation of the cytokine release that is normally initiated by LPS exposure, i.e., there was no increase in IL-1 beta, IL-6, IL-10, IL-12, or tumor necrosis factor (TNF)-alpha release. That a common mechanism may underlie these defects was suggested by the finding that G(D1a) exposure of DC also inhibited the nuclear binding of NF-kappa B that is normally induced by LPS. These results suggest that tumor gangliosides may blunt the anti-tumor immune response in vivo by binding and interfering with dendritic cell maturation.

Correlation of local interleukin-1beta levels with specific IgA response against Gardnerella vaginalis cytolysin in women with bacterial vaginosis

PROBLEM

Mucosal immune system activation may represent a critical determinant of adverse sequelae correlated with bacterial vaginosis, as HIV sexual transmission, upper genital tract infections, cervicitis, endometritis, postsurgical infections, and adverse pregnancy outcomes as preterm delivery (PTD), low birth weight (LBW).

METHOD OF STUDY

Levels of interleukin-1beta (IL-1beta), anti-Gardnerella vaginalis hemolysin (Gvh) IgA, pH, Nugent score, and number of leukocytes were measured in vaginal fluids of 60 fertile women with bacterial vaginosis and of 64 healthy controls.

RESULTS

Vaginal IL-1beta levels were nearly 13-fold higher in women with bacterial vaginosis (BV) and were associated with anti-Gvh IgA response. IL-1beta was positively correlated with leukocyte counts in the smear both in healthy and bacterial vaginosis positive women.

CONCLUSIONS

Induction of the proinflammatory cytokine IL-1beta may be a necessary event to elicit an innate immune response to control anaerobic genital tract infections. High levels of vaginal IL-1beta are associated with mounting of an antigen-specific mucosal immune response in women with bacterial vaginosis. Parallel induction of innate and adaptive immune response may be associated with protection from ascent of micro-organisms to the upper genital tract, and from acquiring viral infection through the vaginal tract.

Antigen-presenting dendritic cells provide the reducing extracellular microenvironment required for T lymphocyte activation

T lymphocytes are defective in cystine uptake and thus require exogenous thiols for activation and function. Here we show that monocyte-derived human dendritic cells (DCs) release cysteine in the extracellular space. Cysteine generation is increased by lipopolysaccharide and tumor necrosis factor alpha, and by contact with T cells specifically recognizing soluble or alloantigens. These stimuli also induce thioredoxin (TRX) accumulation in DCs. However, only the contact with antigen-specific T cells triggers TRX secretion by the antigen-presenting cells. Fewer extracellular thiols are recovered after DC-T cell interactions when cystine uptake or TRX activity are inhibited. In addition, glutamate (Glu) and anti-TRX-inactivating antibodies inhibit antigen-dependent T lymphocyte proliferation. These findings indicate that, during antigen presentation, DCs uptake cystine and release cysteine and TRX, thus providing a reducing microenvironment that facilitates immune response.

IL-1 beta enhances CD40 ligand-mediated cytokine secretion by human dendritic cells (DC): a mechanism for T cell-independent DC activation

CD40 ligand (CD40L) is a membrane-bound molecule expressed by activated T cells. CD40L potently induces dendritic cell (DC) maturation and IL-12p70 secretion and plays a critical role during T cell priming in the lymph nodes. IFN-gamma and IL-4 are required for CD40L-mediated cytokine secretion, suggesting that T cells are required for optimal CD40L activity. Because CD40L is rapidly up-regulated by non-T cells during inflammation, CD40 stimulation may also be important at the primary infection site. However, a role for T cells at the earliest stages of infection is unclear. The present study demonstrates that the innate immune cell-derived cytokine, IL-1beta, can increase CD40L-induced cytokine secretion by monocyte-derived DC, CD34(+)-derived DC, and peripheral blood DC independently of T cell-derived cytokines. Furthermore, IL-1beta is constitutively produced by monocyte-derived DC and monocytes, and is increased in response to intact Escherichia coli or CD40L, whereas neither CD34(+)-derived DC nor peripheral blood DC produce IL-1beta. Finally, DC activated with CD40L and IL-1beta induce higher levels of IFN-gamma secretion by T cells compared with DC activated with CD40L alone. Therefore, IL-1beta is the first non-T cell-derived cytokine identified that enhances CD40L-mediated activation of DC. The synergy between CD40L and IL-1beta highlights a potent, T cell-independent mechanism for DC activation during the earliest stages of inflammatory responses.

Dendritic cells in patients with non-progressive B-chronic lymphocytic leukaemia have a normal functional capability but abnormal cytokine pattern

Dendritic cells (DC) are attractive candidates for use in vaccine-based immunotherapy. We have analysed the functional capability of DC generated in vitro from blood CD14(+) cells of chronic lymphocytic leukaemia (CLL) patients and healthy donors by culturing for 10 d with granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin 4 (IL-4) and tumour necrosis factor-alpha (TNF-alpha). Two distinct DC populations were identified in patients as well as in controls. The majority of DC expressed CD11c and a minority also CD123. Most of the DC generated from both patients and controls exhibited a mature phenotype indicated by CD83 and major histocompatibility complex (MHC) class II expression, as well as by a characteristic morphology. Less than 1% of DC exhibited CD14. CLL DC had a similar expression of accessory molecules (CD54, CD80 and CD86) as control DC. The mean fluorescence intensity of CD80 and MHC class I molecules was significantly higher on CLL DC than on control DC (P < 0.05). At the gene level (real-time polymerase chain reaction) the expression of IL-10 was higher in CLL (P = 0.028) than in control DC. IL-1 beta and IL-12p(35) transcripts were also more abundant in CLL than in control DC but did not reach statistical significance. The expression of IL-4 and TNF-alpha was similar to that of control DC. The interferon gamma (IFN-gamma) gene expression level in CLL DC was decreased compared with control DC. DC of CLL patients had a similar capacity to stimulate in mixed leucocyte reaction as well as to present a recall antigen (PPD) as control DC. Thus, DC of CLL patients seem to have a normal function and may serve as antigen preserving cells for presentation of tumour antigens in a therapeutic vaccination approach. The mechanisms behind the observed increase in some surface molecules and the abnormal cytokine profile of CLL DC is not clear but might indicate pre-activation of DC in vivo, which may have a regulatory role in the pathobiology of CLL.

Rapid secretion of interleukin-1beta by microvesicle shedding

The proinflammatory cytokine interleukin-1beta (IL-1beta) is a secreted protein that lacks a signal peptide and does not follow currently known pathways of secretion. Its efficient release from activated immune cells requires a secondary stimulus such as extracellular ATP acting on P2X(7) receptors. We show that human THP-1 monocytes shed microvesicles from their plasma membrane within 2-5 s of activation of P2X(7) receptors. Two minutes after such stimulation, the released microvesicles contained bioactive IL-1beta, which only later appeared in the vesicle-free supernatant. We conclude that microvesicle shedding is a major secretory pathway for rapid IL-1beta release from activated monocytes and may represent a more general mechanism for secretion of similar leaderless secretory proteins.

CD8(+) T lymphocytes induce polarized exocytosis of secretory lysosomes by dendritic cells with release of interleukin-1beta and cathepsin D

We recently reported that human dendritic cells release the leaderless secretory protein interleukin-1beta (IL-1beta) following specific interaction with alloreactive T lymphocytes. To clarify the molecular mechanism underlying this secretion, this study investigated the intracellular trafficking of IL-1beta in dendritic cells and the signal(s) regulating its release. Results show that a fraction of the intracellular IL-1beta precursor colocalizes with the hydrolase cathepsin D in endolysosomes of dendritic cells; secretion of both proteins is elicited by stimuli that induce intracellular calcium increases. Alloreactive CD8(+) T lymphocytes generate a Ca(++) influx in dendritic cells followed by enrichment in endolysosomes containing IL-1beta and cathepsin D beneath the membrane in contact with T cells. These events result in polarized exocytosis of secretory lysosomes, mediated by microtubules, with release of IL-1beta and cathepsin D toward the interacting CD8(+) T cell.