Dendritic cells: sentinels of immunity and tolerance

Human and herpesvirus microRNAs in periodontal disease

Periodontitis is a multi-etiologic infection characterized clinically by pathologic loss of the periodontal ligament and alveolar bone. Herpesviruses and specific bacterial species are major periodontal pathogens that cooperate synergistically in producing severe periodontitis. Cellular immunity against herpesviruses and humoral immunity against bacteria are key periodontal host defenses. Genetic, epigenetic, and environmental factors are modifiers of periodontal disease severity. MicroRNAs are a class of noncoding, gene expression-based, posttranscriptional regulatory RNAs of great importance for maintaining tissue homeostasis. Aberrant expression of microRNAs has been associated with several medical diseases. Periodontal tissue cells and herpesviruses elaborate several microRNAs that are of current research interest. This review attempts to conceptualize the role of periodontal microRNAs in the pathogenesis of periodontitis. The diagnostic potential of salivary microRNAs is also addressed. Employment of microRNA technology in periodontics represents an interesting new preventive and therapeutic possibility.

Dendritic cells and their associated pro-inflammatory cytokines augment to the inflammatory milieu in vitiligo skin

BACKGROUND AND AIM

Vitiligo is a progressive, autoimmune, hypomelanotic acquired disorder of skin which is characterized by depigmentation. The initial immunological events of this diseases are still at enigma that includes breach of immune tolerance, and defect in antigen presentation. Hence, we aimed to explore role of Dendritic cells (DCs) and its associated cytokines in the pathogenesis of generalized vitiligo (GV) patients.

METHODOLOGY

For this case-control study, 20 active patients and controls were enrolled. Phenotypic characterization of myeloid and plasmacytoid DCs (mDCs, pDCs) were done by flow-cytometry. Primary culture of DCs was done by monocyte differentiation supplemented with rIL-4 and rGM-CSF. Functional analysis DCs related cytokines and co-stimulatory molecules (CD80, CD40) was done by ELISA and qPCR respectively. Tissue localization of DCs was evaluated by immunohistochemistry.

RESULT

The frequency of mDCs (0.3715% v/s 0.188%) and pDCs (0.2331% v/s 0.1156%) were elevated in patients as compared to controls. Circulatory level of IL-12, TNF-α were significantly higher whereas IFN-α was decreased in patients than controls. Similar results were obtained in the culture supernatants of patients. Relative mRNA expression profiling of co-stimulatory molecules (CD80, CD40) were found to be up regulated in patient's skin. Tissue localization of Langerhans cells (Langerin, CD1a⁺) were found to be significantly higher in patients.

CONCLUSION

Elevated frequency of mDCs and pDCs along with elevated levels of IL-12, TNF-α and CD80, CD40 may contribute in defective antigen presentation of DCs. Altered pro-inflammatory and anti-inflammatory cytokines along with tissue localization of Langerhans cells might be involved in the pathogenesis of GV. These DCs associated cytokines can be explored as a therapeutic target in future.

Tolerogenic Dendritic Cells and T-Regulatory Cells at the Clinical Trials Crossroad for the Treatment of Autoimmune Disease; Emphasis on Type 1 Diabetes Therapy

Tolerogenic dendritic cells and T-regulatory cells are two immune cell populations with the potential to prevent the onset of clinical stage type 1 diabetes, and manage the beginning of underlying autoimmunity, at the time-at-onset and onwards. Initial phase I trials demonstrated that the administration of a number of these cell populations, generated ex vivo from peripheral blood leukocytes, was safe. Outcomes of some of these trials also suggested some level of autoimmunity regulation, by the increase in the numbers of regulatory cells at different points in a network of immune regulation in vivo. As these cell populations come to the cusp of pivotal phase II efficacy trials, a number of questions still need to be addressed. At least one mechanism of action needs to be verified as operational, and through this mechanism biomarkers predictive of the underlying autoimmunity need to be identified. Efficacy in the regulation of the underlying autoimmunity also need to be monitored. At the same time, the absence of a common phenotype core among the different dendritic cell and T-regulatory cell populations, that have completed phase I and early phase II trials, necessitates a better understanding of what makes these cells tolerogenic, especially if a uniform phenotypic core cannot be identified. Finally, the inter-relationship of tolerogenic dendritic cells and T-regulatory cells for survival, induction, and maintenance of a tolerogenic state that manages the underlying diabetes autoimmunity, raises the possibility to co-administer, or even to serially-administer tolerogenic dendritic cells together with T-regulatory cells as a cellular co-therapy, enabling the best possible outcome. This is currently a knowledge gap that this review aims to address.

MicroRNAs and immunity in periodontal health and disease

MicroRNAs (miRNAs) are critical regulators of the host immune and inflammatory response against bacterial pathogens. In the present review, we discuss target genes, target gene functions, the potential regulatory role of miRNAs in periodontal tissues, and the potential role of miRNAs as biomarkers and therapeutics. In periodontal disease, miRNAs exert control over all aspects of innate and adaptive immunity, including the functions of neutrophils, macrophages, dendritic cells and T and B cells. Previous human studies have highlighted some key miRNAs that are dysregulated in periodontitis patients. In the present study, we mapped the major miRNAs that were altered in our reproducible periodontitis mouse model relative to control animals. The miRNAs that were upregulated as a result of periodontal disease in both human and mouse studies included miR-15a, miR-29b, miR-125a, miR-146a, miR-148/148a and miR-223, whereas miR-92 was downregulated. The association of individual miRNAs with unique aspects of periodontal disease and their stability in gingival crevicular fluid underscores their potential as markers for periodontal disease progression or healthy restitution. Moreover, miRNA therapeutics hold great promise for the future of periodontal therapy because of their ability to modulate the immune response to infection when applied in conjunction with synthetic antagomirs and/or relatively straightforward delivery strategies.

Small-molecule inhibitor sorafenib regulates immunoreactions by inducing survival and differentiation of bone marrow cells

Sorafenib has been used for the treatment of liver cancer. However, its clinical impact on human immunity system remains poorly known. Our previous study has shown that sorafenib modulates immunosuppressive cell populations in murine liver cancer models. Here, we continue to report that low doses of sorafenib promotes the survival of murine bone marrow cells (BMCs) in a dose-dependent manner by up-regulating the anti-apoptotic protein survivin. Sorafenib induces differentiation of BMCs into suppressive dendritic cells that inhibit autologous T-cell proliferation and stimulate CD4+ T cells to express increased IL-1β, IL-2, IL-4, IL-10, IFN-γ and TNF-α, and reduced levels of IL-6 and CD25, which indicates that sorafenib-induced dendritic cells represent a distinct cellular subset with unique properties. Taken together, our findings suggest that in addition to its anticancer effects, sorafenib has an immunoregulatory property that is apparent at low doses.

Piperlongumine Suppresses Dendritic Cell Maturation by Reducing Production of Reactive Oxygen Species and Has Therapeutic Potential for Rheumatoid Arthritis

Piperlongumine (PLM) is a natural product from the plant Piper longum that inhibits platelet aggregation, atherosclerosis plaque formation, and tumor cell growth. It has potential value in immunomodulation and the management of autoimmune diseases. In this study, we investigated the role of PLM in regulating the differentiation and maturation of dendritic cells (DCs), a critical regulator of immune tolerance, and evaluated its clinical effects in a rheumatoid arthritis mouse model. We found that PLM treatment reduced LPS-induced murine bone marrow-derived DC maturation, characterized by reduced expression of CD80/86, secretion of MCP-1, IL-12p70, IL-6, TNFα, IFN-γ, and IL-23, and reduced alloproliferation of T cells; however, PLM does not affect cell differentiation. Furthermore, PLM reduced intracellular reactive oxygen species (ROS) production by DCs and inhibited the activation of p38, JNK, NF-κB, and PI3K/Akt signaling pathways. Conversely, PLM increased the expression of GSTP1 and carbonyl reductase 1, two enzymes that counteract ROS effects. ROS inhibition by exogenous N-acetyl-l-cysteine suppressed DC maturation. PLM treatment improved the severity of arthritis and reduced in vivo splenic DC maturation, collagen-specific CD4(+) T cell responses, and ROS production in mice with collagen-induced arthritis. Taken together, these results suggest that PLM inhibits DC maturation by reducing intracellular ROS production and has potential as a therapeutic agent for rheumatoid arthritis.

miR-24, miR-30b, and miR-142-3p regulate phagocytosis in myeloid inflammatory cells

Micro-RNAs (miRNAs) are small noncoding RNAs that regulate various biological pathways. As their role in phagocytosis remains poorly understood, we investigated their impact on phagocytosis in myeloid inflammatory cells. Seven miRNAs (miR-24, -30b, -101, 142-3p, -652-3p, -652-5p, and -1275) that were differentially expressed during monocyte to macrophage (Mφ) and monocyte to dendritic cell (DC) differentiation were screened for their potential role in phagocytosis. Among these, overexpression of miR-24, miR-30b, and miR-142-3p in human monocyte-derived Mφ, DC, monocytes, and PBMCs significantly attenuate phagocytosis of Escherichia coli and Staphylococcus aureus, as well as the secretion of inflammatory mediators, including TNF-α, IL-6, and IL-12p40. miRNA-mediated changes in cytokine profiles were observed at transcriptional and/or posttranscriptional levels and importantly exhibit miRNA-specific impact. To examine the underlying mechanism, we monitored the expression of phagocytosis pathway-associated genes and identified several genes that were altered in Mφ and DC transfected with miR-24, miR-30b, and miR-142-3p mimics. Some of these genes with altered expression also harbor putative miRNA binding sites. We show that miR-142-3p directly regulates protein kinase Cα (PKCα), a key gene involved in phagocytosis. Interestingly, miR-142-3p and PKCα exhibit antagonistic expression during Mφ and DC differentiation. Short interfering RNA-mediated knockdown of PKCα in Mφ leads to reduced bacterial uptake, further highlighting the role of the gene in phagocytosis. Overall, these results demonstrate that miR-24, miR-30b, and miR-142-3p regulate phagocytosis and associated cytokine production in myeloid inflammatory cells through modulation of various genes involved in the pathway.

Inflammation and endometrial bleeding

Most of the key physiological processes in the human reproductive tract involve a significant inflammatory component. These processes include follicle development, ovulation, implantation, pregnancy, labor, postpartum, remodeling and menstruation. In this context, the term 'inflammation' usually means an influx of leukocytes ('immune cells'), often of different types, into a reproductive tract tissue. These examples of inflammation are not overtly associated with any infective process. There may also be evidence that these invading leukocytes have altered their functions to take on specific and relevant local regulatory roles. Specific sequential changes in different leukocytes can be demonstrated within human endometrium during the different phases of the normal menstrual cycle. Leukocytes are fairly sparse in numbers through the proliferative phase, but increase substantially into and through the secretory phase, so much so that around 40% of all stromal cells in the premenstrual phase are leukocytes, mainly uterine natural killer cells, a large granulated lymphocyte. Other leukocytes which play key roles in menstruation appear to be macrophages, mast cells, dendritic cells, neutrophils, eosinophils and regulatory T cells. Premenstrual withdrawal of progesterone increases the endometrial expression of inflammatory mediators, including IL-8 and MCP-1, which are believed to drive endometrial leukocyte recruitment at this time. Macrophages and neutrophils are rich sources of defensins and whey acid protein motif proteins, which play important roles in ensuring microbial protection while the epithelial barrier is disrupted. Mast cells are increasingly activated as the menstrual phase approaches, and leukocyte proteases trigger a cascade of matrix metalloproteinases and degradation of extracellular matrix. Dendritic cells and other antigen-presenting cells (e.g. macrophages) almost certainly facilitate clearance of cellular debris from the uterine cavity, and reduce the amount of viable cellular material transiting the Fallopian tubes. All of these processes are influenced or controlled by regulatory T cells. Many of these leukocytes also have the potential to release regulatory molecules which stimulate endometrial repair mechanisms. Increasing recent evidence also implicates disturbances of immune cells and their cytokine mediators in contributing to symptoms of abnormal uterine bleeding and pelvic pain. These recent findings all point towards the importance of the 'inflammatory process' in both normal and abnormal endometrial bleeding.

Mechanisms of dendritic cell lysosomal killing of Cryptococcus

Cryptococcus neoformans is an opportunistic pulmonary fungal pathogen that disseminates to the CNS causing fatal meningitis in immunocompromised patients. Dendritic cells (DCs) phagocytose C. neoformans following inhalation. Following uptake, cryptococci translocate to the DC lysosomal compartment and are killed by oxidative and non-oxidative mechanisms. DC lysosomal extracts kill cryptococci in vitro; however, the means of antifungal activity remain unknown. Our studies determined non-oxidative antifungal activity by DC lysosomal extract. We examined DC lysosomal killing of cryptococcal strains, anti-fungal activity of purified lysosomal enzymes, and mechanisms of killing against C. neoformans. Results confirmed DC lysosome fungicidal activity against all cryptococcal serotypes. Purified lysosomal enzymes, specifically cathepsin B, inhibited cryptococcal growth. Interestingly, cathepsin B combined with its enzymatic inhibitors led to enhanced cryptococcal killing. Electron microscopy revealed structural changes and ruptured cryptococcal cell walls following treatment. Finally, additional studies demonstrated that osmotic lysis was responsible for cryptococcal death.

Cellular MRI as a suitable, sensitive non-invasive modality for correlating in vivo migratory efficiencies of different dendritic cell populations with subsequent immunological outcomes

The clinical application of dendritic cells (DC) as adjuvants in immunotherapies such as the cell-based cancer vaccine continues to gain interest. The overall efficacy of this emerging immunotherapy, however, remains low. Studies suggest the stage of maturation and activation of ex vivo-prepared DC immediately prior to patient administration is critical to subsequent DC migration in vivo, which ultimately affects overall vaccine efficacy. While it is possible to generate mature and activated DC ex vivo using various stimulatory cocktails, in the case of cancer patients, the qualitative and quantitative assessment of which DC stimulatory cocktail works most effectively to enhance subsequent DC migration in vivo is difficult. Thus, a non-invasive imaging modality capable of monitoring the real-time migration of DC in long-term studies is required. In this paper, we address whether cellular magnetic resonance imaging (MRI) is sufficiently sensitive to quantitatively detect differences in the migratory abilities of two different DC preparations: untreated (resting) versus ex vivo matured in a mouse model. In order to distinguish our ex vivo-generated DC of interest from surrounding tissues in magnetic resonance (MR) images, DC were labeled in vitro with the superparamagnetic iron oxide (SPIO) nanoparticle FeREX®. Characterization of DC phenotype and function following addition of a cytokine maturation cocktail and the toll-like receptor ligand CpG, both in the presence and in the absence of SPIO, were also carried out. Conventional histological techniques were used to verify the quantitative data obtained from MR images. This study provides important information relevant to tracking the in vivo migration of ex vivo-prepared and stimulated DC.

Berberine induces dendritic cell apoptosis and has therapeutic potential for rheumatoid arthritis

OBJECTIVE

To investigate the effects of berberine on dendritic cell (DC) apoptosis and its potential as a therapeutic agent in rheumatoid arthritis (RA).

METHODS

Bone marrow (BM)-derived myeloid DCs (MDCs) and plasmacytoid DCs (PDCs) were generated by culturing BM cells with granulocyte-macrophage colony-stimulating factor/interleukin-4 or flt3L, respectively. Splenic DCs, T cells, and B cells were purified using a magnetic-activated cell sorting system. In vitro apoptosis was assessed by annexin V/propidium iodide or Hoechst 33258 staining. The in vivo effects of berberine were examined in mice with collagen-induced arthritis (CIA). Immune responses against type II collagen (CII) were determined by assaying serum antibody levels, lymphocyte proliferation, and cytokine production. The proportions of DCs and apoptosis of different immune cell subsets in spleens and lymph nodes were analyzed by flow cytometry and immunohistochemistry after subset-specific surface marker labeling and TUNEL staining.

RESULTS

Exposure of MDCs to berberine during BM cell differentiation reduced cell recovery by inducing apoptosis. Sensitivity to berberine-induced apoptosis was acquired starting on day 3 of DC differentiation, and mature DCs were more sensitive to berberine than immature DCs. Murine peritoneal macrophages, RAW 264.7 cells, and Jurkat cells were insensitive to berberine-induced apoptosis. Splenic DCs were more sensitive to berberine than T and B cells. Susceptibility of PDCs to berberine-induced apoptosis was similar to that of MDCs. In mice with CIA, berberine treatment ameliorated arthritis, suppressed CII-specific immune responses, and selectively increased the incidence of apoptosis in DCs within spleens and lymph nodes.

CONCLUSION

These findings show that berberine selectively induces apoptosis in DCs. Berberine may thus represent a novel therapeutic agent for RA.

Functional characterization of peripheral blood dendritic cells and monocytes in systemic lupus erythematosus

With the purpose of contributing to a better knowledge of the APCs functional activity in SLE, we evaluated the distribution and functional ability to produce pro-inflammatory cytokines (TNF-α, IL-1β, IL-6 and IL-12) of peripheral blood (PB) monocytes and DC (tDC), particularly myeloid (mDC) and CD14(-/low)CD16(+) DC subpopulations comparing them with those obtained from healthy individuals. The study was performed in 34 SLE patients with diverse disease activity scores (SLEDAI) and 13 healthy age- and sex-matched controls (NC). Our results show an overall decrease in absolute number and relative frequency of tDC in SLE patients with active disease when compared to those with inactive disease and NC, although this decrease did not seem to have an effect on the distribution of PB DC subsets. The monocytes number in SLE patients was similar to those found in NC, whereas a higher frequency of monocytes producing cytokines as well as the amount of each cytokine per cell found without stimulation was particularly observed in those patients with active disease. After stimulation, we observed a higher frequency of IL-12-producing monocytes in active SLE patients. On the other hand, we found among DCs higher frequencies of cytokine-producing CD14(-/low)CD16(+) DCs and a higher amount of cytokines produced per cell, particularly in active disease. These findings support an increased production of inflammatory cytokines by APCs in active SLE, mostly associated with alterations in CD14(-/low)CD16(+) DC subset homeostasis that might contribute to explain the dynamic role of these cells in disease pathogenesis.

Immune regulatory cells in umbilical cord blood and their potential roles in transplantation tolerance

Umbilical cord blood (UCB) is a source of primitive hematopoietic stem (HSC) and progenitor cells, that served as an alternative to bone marrow (BM) for effective transplantation therapy. Success of HSC transplantation (HSCT) is limited in part by graft-versus-host disease (GVHD), graft rejection and delayed immune reconstitution, which all relate to immunological complications. GVHD after UCB transplantation is lower compared to that of BM HSCT. This may relate to the tolerogenic nature of T cells, mononuclear cells (MNCs) and especially immune regulatory cells existing in UCB. UCB contains limiting numbers of HSC or CD34(+) cell dose for adult patients resulting in delayed engraftment after UCB transplantation (UCBT). This needs to be improved for optimal transplantation outcomes. Approaches have been undertaken to promote HSC engraftment, including co-infusion of multiple units of UCB cells. These new methods however added additional immunological complications. Herein, we describe current knowledge on features of UCB immune cells, including regulatory T cells (Tregs) and mesenchymal stem/stromal cells (MSCs) and their potential future usage to reduce GVHD.

Dendritic cell-based therapy in Type 1 diabetes mellitus

Dendritic cell (DC) immunotherapy is a clinical reality. Despite two decades of considerable data demonstrating the feasibility of using DCs to prolong transplant allograft survival and to prevent autoimmunity, only now are these cells entering clinical trials in humans. Type 1 diabetes is the first autoimmune disorder to be targeted for treatment in humans using autologous-engineered DCs. This review will highlight the role of DCs in autoimmunity and the manner in which they have been engineered to treat these disorders in rodent models, either via the induction of immune hyporesponsiveness, which may be cell- and/or antigen-specific, or indirectly by upregulation of other immune cell networks.

Human dendritic cell antigen presentation and chemotaxis are inhibited by intrinsic 25-hydroxy vitamin D activation

The immunomodulatory effects of vitamin D have primarily been investigated using the biologically active form 1,25-dihydroxy vitamin D3 (1,25-D3). It was recently demonstrated that dendritic cells (DC) are able to convert the inactive 25-hydroxy vitamin D3 (25-D3) into the active form via 1 alpha-hydroxylase. In this study, we set out to examine the possible consequences of this conversion on adaptive immune functions. Human monocyte-derived DC were matured by lipopolysaccharide (LPS) in the presence or absence of 25-D3. Subsequently, the conversion of 25-D3 into 1,25-D3, and the effects on surface marker expression, cytokine production, antigen-presenting capacity and chemotaxis of the DC were examined. 25-D3 was clearly converted into 1,25-D3 in the DC cultures and the process was accompanied by a reduced expression of CD80 (p<0.01), CD83 (p<0.01), CD86 (p=0.02), and HLA-DR (p=0.02). Also, the levels of the pro-inflammatory cytokines tumour necrosis factor (TNF) alpha (p=0.02) and interleukin (IL) 12 (p<0.01) were reduced. Interestingly, however, the CD14 expression (p<0.01) and the production of IL-1 beta (p<0.01) and IL-6 (p<0.01) increased. Thus, 25-D3 affected the delicate interplay between anti- and pro-inflammatory cytokines produced by the DC. Concurrently, 25-D3 reduced DC capacity to induce proliferation of antigen-specific T cells and DC chemotaxis towards chemokine (CC) ligand 21. This indicates that 25-D3 has a regulating function following intrinsic 1 alpha-hydroxylation, a mechanism that potentially has an immunomodulatory effect in vivo.

Functional impairment of human myeloid dendritic cells during Schistosoma haematobium infection

Chronic Schistosoma infection is often characterized by a state of T cell hyporesponsiveness of the host. Suppression of dendritic cell (DC) function could be one of the mechanisms underlying this phenomenon, since Schistosoma antigens are potent modulators of dendritic cell function in vitro. Yet, it remains to be established whether DC function is modulated during chronic human Schistosoma infection in vivo. To address this question, the effect of Schistosoma haematobium infection on the function of human blood DC was evaluated. We found that plasmacytoid (pDC) and myeloid DC (mDC) from infected subjects were present at lower frequencies in peripheral blood and that mDC displayed lower expression levels of HLA-DR compared to those from uninfected individuals. Furthermore, mDC from infected subjects, but not pDC, were found to have a reduced capacity to respond to TLR ligands, as determined by MAPK signaling, cytokine production and expression of maturation markers. Moreover, the T cell activating capacity of TLR-matured mDC from infected subjects was lower, likely as a result of reduced HLA-DR expression. Collectively these data show that S. haematobium infection is associated with functional impairment of human DC function in vivo and provide new insights into the underlying mechanisms of T cell hyporesponsiveness during chronic schistosomiasis.

Development of dendritic cell-based immunotherapy for autoimmunity

Dendritic cells are professional antigen-presenting cells that maintain immune tolerance to self-antigens by deleting or controlling the pathogenicity of auto-reactive T-cells. Dendritic cell-based immunotherapies show great promise for the restoration of tolerance in autoimmune disease. Dendritic cells can be modified ex vivo to induce stable tolerogenic function and be used as cellular 'vaccines' or they can be targeted in vivo with sophisticated antigen delivery systems. Tolerogenic dendritic cells induce antigen-specific T-cell tolerance in vivo and have therapeutic effects in animal models of autoimmunity. The current challenge is to bring tolerogenic dendritic cell therapy to the clinic.

Cellular cardiomyoplasty: what have we learned?

Restoring blood flow, improving perfusion, reducing clinical symptoms, and augmenting ventricular function are the goals after acute myocardial infarction. Other than cardiac transplantation, no standard clinical procedure is available to restore damaged myocardium. Since we first reported cellular cardiomyoplasty in 1989, successful outcomes have been confirmed by experimental and clinical studies, but definitive long-term efficacy requires large-scale placebo-controlled double-blind randomized trials. On meta-analysis, stem cell-treated groups had significantly improved left ventricular ejection fraction, reduced infarct scar size, and decreased left ventricular end-systolic volume. Fewer myocardial infarctions, deaths, readmissions for heart failure, and repeat revascularizations were additional benefits. Encouraging clinical findings have been reported using satellite or bone marrow stem cells, but understanding of the benefit mechanisms demands additional studies. Adult mammalian ventricular myocardium lacks adequate regeneration capability, and cellular cardiomyoplasty offers a new way to overcome this; the poor retention and engraftment rate and high apoptotic rate of the implanted stem cells limit outcomes. The ideal type and number of cells, optimal timing of cell therapy, and ideal cell delivery method depend on determining the beneficial mechanisms. Cellular cardiomyoplasty has progressed rapidly in the last decade. A critical review may help us to better plan the future direction.

Immune responses of human immature dendritic cells can be modulated by the recombinant Aspergillus fumigatus antigen Aspf1

Invasive aspergillosis is a significant cause of morbidity and mortality in patients after stem cell transplantation, in solid organ transplant recipients, and in patients with hematological malignancies. The interactions between human immature dendritic cells (iDCs) and Aspergillus fumigatus antigens are widely uncharacterized. We analyzed the immune response of iDCs to different recombinant A. fumigatus antigens (Aspf1 and Crf1). One of these antigens, the 18-kDa RNase Aspf1, triggered the increased level of expression of genes encoding proinflammatory cytokines and chemokines, and augmented the activation of NFkappaB and the apoptosis of iDCs. Furthermore, by fluorescence microscopy, we could demonstrate that in the first 3 h a major portion of Aspf1 accumulates on the cell surface. Finally, we could show an increased segregation of cytokines and chemokines after the stimulation of iDCs by an Aspf1 deletion mutant strain of A. fumigatus.

Effect of tissue-specific promoters and microRNA recognition elements on stability of transgene expression after hydrodynamic naked plasmid DNA delivery

Intravenous hydrodynamic injections into the liver and skeletal muscle have increased the efficacy of naked DNA delivery to a level that makes therapeutically relevant gene transfer attainable. Although there are no concerns about the immunogenicity of the delivered DNA itself, transgene products that are foreign to the host can trigger an immune response and hamper the therapeutic effect. Our goal was to determine whether and to what extent some known preventive measures are applicable to these delivery methods in order to achieve longterm expression of foreign proteins in immunocompetent mice. We designed plasmid DNA vectors that expressed a marker gene under the control of either a ubiquitous or a tissue-specific promoter. We also included microRNA (miR) target sites in the transcripts in order to silence expression in antigen-presenting cells (APCs). The constructs were delivered either into muscle or liver, using outbred ICR and inbred C57BL=6 mice. The data suggest that firefly luciferase, a potent immunogen, triggered a uniform immune response only in outbred ICR mice, and only when expressed from a ubiquitous promoter. This response could not be prevented by including APC-specific miR target sites in the transcript. In contrast, the probability of immune rejection in ICR mice could be significantly diminished by using tissue-specific promoters, and under these circumstances, the silencing of transgene expression in APCs did confer some benefits. After a single hydrodynamic injection, inbred mice did not reject luciferase under any of the tested conditions for at least 8 weeks. To test whether they became tolerized, they were challenged with a second boost of a cytomegalovirus promoter-driven luciferase construct. This triggered a strong immune response, suggesting that luciferase-reactive cells from the animals' T and B cell repertoire had not been eliminated. This secondary reaction could not be prevented by silencing expression in APCs. In conclusion, for the clinical application of hydrodynamic naked DNA delivery the use of tissue-specific promoters in combination with silencing expression in APCs will increase the probability of long-term expression, but the most desirable outcome, the establishment of transgene tolerance, appears unlikely to be achieved by any of these measures.

Apicidin, the Histone Deacetylase Inhibitor, Suppresses TH1 Polarization of Murine Bone Marrow-Derived Dendritic Cells

Apicidin is a fungal metabolite shown to exhibit anti-proliferative, anti-invasive, and anti-inflammatory properties by the inhibition of histone deacetylase (HDAC). However, the effects of apicidin on the maturation and immunostimulatory function of dendritic cells (DCs) remain unknown. In this study, we investigated whether apicidin modulates surface molecule expression, cytokine production, endocytosis capacity, and underlying signaling pathways in murine bone marrow-derived DCs. We observed that apicidin significantly attenuated surface molecule expression in LPS-stimulated DCs, suppressed production of interleukin (IL)-12 and proinflammatory cytokines (IL-6 and TNF-α) by DCs, and reduced IFN-γ production by T cells. The apicidin-treated DCs were found to be highly efficient in antigen capture via mannose receptor-mediated endocytosis. Apicidin also inhibited LPS-induced MAPK activation and NF-κB nuclear translocation in DCs. Moreover, the apicidin-treated DCs were incapable of inducing Th1 responses and normal cell-mediated immune responses. These novel findings not only provide new insights into the immunopharmacological role of apicidin in terms of its effects on DCs, but also broaden current perspectives of the immunopharmacological functions of apicidin, and have implications for the development of therapeutic adjuvants for the treatment of DC-related acute and chronic diseases.

Transplantation of bone marrow transduced to express self-antigen establishes deletional tolerance and permanently remits autoimmune disease

Autoimmune diseases are incurable. We have hypothesized that these diseases can be cured by the transplantation of bone marrow (BM) stem cells that have been genetically engineered to express self-Ag. Here we have tested this hypothesis in experimental autoimmune encephalomyelitis (EAE) induced by the self-Ag myelin oligodendrocyte glycoprotein (MOG). We show that, in mice, transplantation of BM genetically modified to express MOG prevented the induction and progression of EAE, and combined with antecedent corticosteroid treatment, induced long-term remission of established disease. Mice remained resistant to EAE development upon subsequent rechallenge with MOG. Transfer of BM from these mice rendered recipients resistant to EAE. Splenocytes from these mice failed to proliferate or produce IL-17, IFN-gamma, and GM-CSF in response to MOG(35-55) peptide stimulation and they failed to produce MOG autoantibody. Mechanistically, we demonstrated in vivo reduction in development of CD4(+) MOG(35-55)-specific thymocytes, indicative of clonal deletion with no evidence for selection of Ag-specific regulatory T cells. These findings validate our hypothesis that transplantation of genetically modified BM expressing disease-causative self-Ag provides a curative approach by clonal deletion of disease-causative self-reactive T cells.

Effects of gliadin stimulation on bone marrow-derived dendritic cells from HLA-DQ8 transgenic MICE

BACKGROUND AND AIM

Gliadin presentation by HLA-DQ2/8 molecules to T cells plays a crucial role in triggering the inflammatory cascade in coeliac disease. We aimed to study the immunological effects of gliadin stimulation on dendritic cells (DCs) from HLA-DQ8 transgenic and BALB/c mice.

METHODS

Bone marrow-derived DCs were stimulated with alpha-chymotrypsin-digested gliadin or ovoalbumin (100 microg/ml). Modification of DC maturation, through HLA-DQ8 and MHC class II expression, and activation, by CD80 and CD86, was assessed by flow cytometry. The ability of pulsed and unpulsed DCs to prime T cells was evaluated by mixed leucocyte reaction. The expression of interleukin-4, -10, -12p70 and interferon-alpha, as well as of Toll-like receptor-4, -7, -8, -9 was determined by ELISA and real-time RT-PCR, respectively.

RESULTS

Gliadin stimulation induced DC maturation (p<0.001 in BALB/c, p<0.01 in DQ8) but not activation, whereas ovoalbumin upregulated all markers (p<0.01 for maturation and p<0.001 for activation in both DC populations). No increase of T proliferation was elicited by pulsed DCs with respect to unpulsed DCs. Only in DQ8 DCs, gliadin induced Toll-like receptor-4 (p<0.001), -7 (p<0.001), -8 (p<0.005) expression and interferon-alpha (p<0.001) secretion.

CONCLUSION

Gliadin resulted unable to activate DC, but stimulated Toll-like receptor expression and interferon-alpha secretion.

Dendritic cell microvilli: a novel membrane structure associated with the multifocal synapse and T-cell clustering

Polarizing effects of productive dendritic cell (DC)-T-cell interactions on DC cytoskeleton have been known in some detail, but the effects on DC membrane have been studied to a lesser extent. We found that T-cell incubation led to DC elongation and segregation of characteristic DC veils to the broader pole of the cell. On the opposite DC pole, we observed a novel membrane feature in the form of bundled microvilli. Each villus was approximately 100 nm in diameter and 600 to 1200 nm long. Microvilli exhibited high density of antigen-presenting molecules and costimulatory molecules and provided the physical basis for the multifocal immune synapse we observed during human DC and T-cell interactions. T cells preferentially bound to this site in clusters often contained both CD4(+) and CD8(+) T cells.

Toward a cure for type 1 diabetes mellitus: diabetes-suppressive dendritic cells and beyond

Insulin has been the gold standard therapy for diabetes since its discovery and commercial availability. It remains the only pharmacologic therapy for type 1 diabetes (T1D), an autoimmune disease in which autoreactive T cells specifically kill the insulin-producing beta cells. Nevertheless, not even molecularly produced insulin administered four or five times per day can provide a physiologic regulation able to prevent the complications that account for the morbidity and mortality of diabetic patients. Also, insulin does not eliminate the T1D hallmark: beta-cell-specific autoimmunity. In other words, insulin is not a 'cure'. A successful cure must meet the following criteria: (i) it must either replace or maintain the functional integrity of the natural, insulin-producing tissue, the endocrine islets of Langerhans' and, more specifically, the insulin-producing beta cells; (ii) it must, at least, control the autoimmunity or eliminate it altogether; and (iii) it must be easy to apply to a large number of patients. Criterion 1 has been partially realized by allogeneic islet transplantation. Criterion 2 has been partially realized using monoclonal antibodies specific for T-cell surface proteins. Criterion 3 has yet to be realized, given that most of the novel therapies are currently quasi-patient-specific. Herein, we outline the current status of non-insulin-based therapies for T1D, with a focus on cell-based immunomodulation which we propose can achieve all three criteria illustrated above.

Antigen presenting cells treated in vitro by macrophage colony-stimulating factor and autoantigen protect mice from autoimmunity

Macrophage colony-stimulating factor (M-CSF) is a critical cytokine in the development of monocytic lineage and may have immunoregulatory properties. Here we show that peritoneal antigen presenting cells (APCs) treated with M-CSF produced decreased levels of proinflammatory cytokines IFN-gamma, TNF-alpha and IL-12. These APCs treated with M-CSF+autoantigen peptide significantly suppressed antigen-specific T cell proliferation, induced regulatory CD4(+) and CD8(+) T cells in vitro and in vivo, and significantly suppressed experimental autoimmune encephalomyelitis (EAE). Thus, in vitro treatment of APCs with M-CSF+autoantigen can be a novel therapeutic option for autoimmune diseases.

The effect of dendritic cells on the retinal cell transplantation

The potential of bone marrow cell-derived immature dendritic cells (myeloid iDCs) in modulating the efficacy of retinal cell transplantation therapy was investigated. (1) In vitro, myeloid iDCs but not BMCs enhanced the survival and proliferation of embryonic retinal cells, and the expression of various neurotrophic factors by myeloid iDCs was confirmed with RT-PCR. (2) In subretinal transplantation, neonatal retinal cells co-transplanted with myeloid iDCs showed higher survival rate compared to those transplanted without myeloid iDCs. (3) CD8 T-cells reactive against donor retinal cells were significantly increased in the mice with transplantation of retinal cells alone. These results suggested the beneficial effects of the use of myeloid iDCs in retinal cell transplantation therapy.

Immunoregulatory dendritic cells to prevent and reverse new-onset Type 1 diabetes mellitus

Herein, the authors provide an overview of where dendritic cells lie in the immunopathology of autoimmune Type 1 diabetes mellitus and how dendritic cell-based therapy may be usefully translated to treat and reverse the disease. The immunopathology of Type 1 diabetes mellitus offers a number of windows at which immunotherapy can be applied to delay, stop and even reverse the autoimmune processes, especially in light of the recent antibody-based accomplishment of improvement in residual beta-cell mass function. As in almost all cell-specific inflammatory processes, dendritic cells are central regulators of diabetes onset and progression. This realisation, along with accumulating data confirming a role for dendritic cells in maintaining and inducing tolerance in multiple therapeutic settings, has prompted a line of investigation to identify the most effective embodiments of dendritic cells for diabetes immunotherapy.

The cross-talk between dendritic and regulatory T cells: good or evil?

Immune responses against pathogens require fine regulation to avoid excessive inflammation, which could be harmful to the host. Moreover, the immune system must be tolerant to nonpathogenic antigens to prevent allergy, autoimmunity, and transplant rejection. There is accumulating evidence that interactions between dendritic cells (DC) and regulatory T (Treg) cells play a crucial role in the balance between immune response and tolerance. Communications between these cells are complex, bidirectional, and mediated by soluble or cell surface molecules. The maturation status of DC, which may be influenced by different microenvironmental factors, is considered as an important checkpoint for the induction of peripheral tolerance through modifications of the activation status of T cells. Moreover, several lines of experimental evidence suggest that different subsets or the functional status of DC are also involved in the promotion of Treg cell differentiation. A better knowledge of the regulatory mechanisms of the immune response induced or inhibited by DC via their interactions with Treg cells could be relevant for the development of new, immunotherapeutic approaches.

Reduced number and function of peripheral dendritic cells in coeliac disease

Dendritic cells (DC) play a pivotal role in shaping the immune response in both physiological and pathological conditions. In peripheral blood at least two subsets, the myeloid and plasmacytoid, have been described as having different T stimulatory functions and a variable degree of maturation. Certainly, antigen presentation plays a crucial role in the pathogenesis of coeliac disease and circulating immune cells are thought to reflect the state of immune response within the gut. Therefore, we aimed to investigate the quantitative and phenotypical modifications of peripheral blood DC, together with their functional properties, in this pathological condition. Blood samples from 11 untreated patients before and after a course of gluten-free diet, 27 treated patients and 14 controls underwent flow-cytometric analysis, while immunomagnetically sorted DC from the CD patients and eight human leucocyte antigen (HLA)-DQ2/8(+) bone marrow donors were used to evaluate maturation status through the CD83 expression, cytokine profile for interleukin (IL)-6, IL-10, IL-12 and interferon (IFN)-alpha by enzyme-linked immunosorbent assay (ELISA), and functional properties by mixed leucocyte reaction before and after pulsing with digested gliadin. We found that in both untreated and treated patients, a significant reduction of the entire DC population, mainly the plasmacytoid subset, in comparison to healthy controls was observed. In active disease, an impaired allogenic lymphocyte reaction and a significant reduction of IFN-alpha production, paralleled by the presence of a more immature status, were also demonstrated. All the latter modifications have been reverted by pulsing DC with digested gliadin.

Oxymetazoline modulates proinflammatory cytokines and the T-cell stimulatory capacity of dendritic cells

Abstract:  The nasal decongestant oxymetazoline (OMZ) is frequently used in the topical treatment of rhinitis/sinusitis. As proinflammatory cytokines play a critical role in the development and maintenance of local inflammation, the aim of this study was to investigate the influence of OMZ on immune cells in order to diminish the mucosal infiltration of the nose. Peripheral blood mononuclear cells (PBMC) from buffy coats of healthy volunteers were isolated and stimulated in the presence or absence of OMZ. In addition, monocyte‐derived dendritic cells (DC) were generated and different concentrations of OMZ were added. DC phenotype and their T‐cell stimulatory properties were analysed. The vasoactive substance OMZ showed a concentration dependent inhibitory effect on T‐cell activation as well as a dominant effect on T‐cell stimulatory properties of DC. Low concentrations of OMZ inhibited the proliferation of polyclonally activated T cells. In addition, secretion of proinflammatory mediators such as the cytokines interleukin‐1β (IL‐1β), tumor necrosis factor‐α (TNF α), IL‐6 and IL‐8 were inhibited in the presence of physiological doses of OMZ. Interestingly, the addition of IL‐6 to DC‐T‐cell co‐culture was able to completely restore T‐cell proliferation. In conclusion, these findings indicate that the anti‐inflammatory properties of OMZ are partially mediated by the inhibition of proinflammatory cytokines as well as reduced T‐cell stimulatory capacity of DC resulting in a repressed stimulation of T cells. Therefore, the therapeutic benefit of OMZ can be explained in part by its immunomodulating effects in the topical treatment of nasal inflammation.

Transplantation of bone marrow genetically engineered to express proinsulin II protects against autoimmune insulitis in NOD mice

BACKGROUND

Type 1 diabetes (T1D) is a T-cell-dependent autoimmune disease resulting from destructive inflammation (insulitis) of the insulin-producing pancreatic beta-cells. Transgenic expression of proinsulin II by a MHC class II promoter or transfer of bone marrow from these transgenic mice protects NOD mice from insulitis and diabetes. We assessed the feasibility of gene therapy in the NOD mouse as an approach to treat T1D by ex vivo genetic manipulation of normal hematopoietic stem cells (HSCs) with proinsulin II followed by transfer to recipient mice.

METHODS

HSCs were isolated from 6-8-week-old NOD female mice and transduced in vitro with retrovirus encoding enhanced green fluorescent protein (EGFP) and either proinsulin II or control autoantigen. Additional control groups included mice transferred with non-manipulated bone marrow and mice which did not receive bone marrow transfer. EGFP-sorted or non-sorted HSCs were transferred into pre-conditioned 3-4-week-old female NOD mice and insulitis was assessed 8 weeks post-transfer.

RESULTS

Chimerism was established in all major lymphoid tissues, ranging from 5-15% in non-sorted bone marrow transplants to 20-45% in EGFP-sorted bone marrow transplants. The incidence and degree of insulitis was significantly reduced in mice receiving proinsulin II bone marrow compared to controls. However, the incidence of sialitis in mice receiving proinsulin II bone marrow and control mice was not altered, indicating protection from insulitis was antigen specific.

CONCLUSIONS

We show for the first time that ex vivo genetic manipulation of HSCs to express proinsulin II followed by transplantation to NOD mice can establish molecular chimerism and protect from destructive insulitis in an antigen-specific manner.

Tissue homeostasis and cancer

Epithelial cells are known to release an important amount of cytokines capable to modulate immune system functions. On the other hand, immune system cells can release cytokines, which play an important role in the control of the growth of epithelial cells. In this paper, we stand the hypothesis that a mutual (reciprocal) growth regulation exists between epithelial cells and immune system. We propose a model describing plausible cytokine circuits that may regulate (inhibit) both epithelial growth and epithelial inflammation. In addition, we describe how dysfunction of these circuits could lead to tumoral growth, excessive inflammation or both. A failure in the regulation of epithelial growth by the immune system could give rise to a neoplasm, and a failure in the regulation of the immune system by the epithelium could give rise to inflammatory or autoimmune diseases. This model may satisfactorily explain the link between inflammation and cancer.

Modeling regulation mechanisms in the immune system

We develop a mathematical framework for modeling regulatory mechanisms in the immune system. The model describes dynamics of key components of the immune network within two compartments: lymph node and tissue. We demonstrate using numerical simulations that our system can eliminate virus-infected cells, which are characterized by a tendency to increase without control (in absence of an immune response), while tolerating normal cells, which are characterized by a tendency to approach a stable equilibrium population. We experiment with different combinations of T cell reactivities that lead to effective systems and conclude that slightly self-reactive T cells can exist within the immune system and are controlled by regulatory cells. We observe that CD8+ T cell dynamics has two phases. In the first phase, CD8+ cells remain sequestered within the lymph node during a period of proliferation. In the second phase, the CD8+ population emigrates to the tissue and destroys its target population. We also conclude that a self-tolerant system must have a mechanism of central tolerance to ensure that self-reactive T cells are not too self-reactive. Furthermore, the effectiveness of a system depends on a balance between the reactivities of the effector and regulatory T cell populations, where the effectors are slightly more reactive than the regulatory cells.

Development of a secondary autoimmune disorder after hematopoietic stem cell transplantation for autoimmune diseases: role of conditioning regimen used

Patients undergoing autologous hematopoietic stem cell transplantation (auto-HSCT) for autoimmune disease may have an added propensity to develop a second autoimmune disorder, given the genetic predisposition to autoimmunity. Therefore, we undertook a retrospective analysis of all patients who have undergone auto-HSCT for an autoimmune disease in our institution to determine the occurrence of a second autoimmune disorder and possible risk factors. In all, 155 patients underwent auto-HSCT for various autoimmune diseases; of those patients, 6 manifested a distinct secondary autoimmune disease at a median of 8.5 months (range, 2-30 months) after auto-HSCT. There were 2 patients with systemic lupus erythematosus, conditioned with a regimen containing antithymocyte globulin (ATG), who developed factor VIII inhibitors with severe bleeding. There were 4 patients (2 with multiple sclerosis, one each with lupus and systemic sclerosis) who received an alemtuzumab-containing conditioning regimen who developed autoimmune cytopenias. Among the 155 patients, the frequency of secondary autoimmune complications was 16.0% with alemtuzumab (4/25), 1.9% for ATG (2/102), and 0% for conditioning regimens without lympho-depleting antibodies (0/28)-a difference that was found to be significantly higher with alemtuzumab exposure (P = .011). In contrast, sex, type of ATG used, and CD34-selection of peripheral blood stem cells were not found to be significantly associated with development of a secondary autoimmune disorder.

Estrogen-mediated immunomodulation involves reduced activation of effector T cells, potentiation of treg cells, and enhanced expression of the PD-1 costimulatory pathway

Estrogen (E2)-induced immunomodulation involves dual effects on antigen-presenting cells (APC) and CD4(+)CD25(+) regulatory T cells (Treg) but not a direct effect on effector T cells. In this report, we further investigated the effects of E2 on APC and Treg function. We found that E2 treatment in vivo strongly reduced recovery of APC from the peritoneal cavity and inhibited induction of the inflammatory cytokines interleukin (IL)-12 and interferon-gamma but enhanced secretion of IL-10. Moreover, E2-conditioned bone marrow-derived dendritic cells (BM-DC) could both enhance Treg activity and directly inhibit responder T cells in the absence of Treg cells. We examined whether this E2-induced inhibitory activity of BM-DC might involve costimulation through the recently described PD-1 pathway. Both E2 and pregnancy markedly enhanced PD-1 expression in several types of APC, including macrophages, B cells, and especially dendritic cells (DC). Similarly to E2-induced enhancement of FoxP3 expression and experimental autoimmune encephalomyelitis protection, E2-induced enhancement of PD-1(+) cells was also mediated through estrogen receptor alpha (Esr1) in DC and macrophages but not in B cells. Based on antibody inhibition studies, PD-1 interaction with its ligands, PDL-1 and especially PDL-2, could mediate either positive or negative regulatory signaling in both mature and immature E2-conditioned DC, depending, respectively, on a relatively high (10:1) or low (1:1) ratio of T cells:BM-DC. These novel findings indicate that E2-induced immunomodulation is mediated in part through potentiation in BM-DC of the PD-1 costimulatory pathway.

Attenuated alloreactivity of dendritic cells engineered with surface-modified microspheres carrying a plasmid encoding interleukin-10

In the present study, we investigated MS(O10H6) as a carrier system to introduce a plasmid encoding murine interleukin-10 (pIL-10) to modulate alloreactivity of dendritic cells (DC). Results indicate that MS(O10H6) formed stable and protective nano-sized particles with pIL-10. Gene-modified DC elicited weak proliferation of allogeneic CD4 and CD8 T cells in vitro. Using cell-embedded Matrigel as a surrogate graft, we also showed that DC transfected with MS(O10H6) complexed with pIL-10 suppressed host cell infiltration in vivo. These data demonstrate that the self-assembled system of MS(O10H6) is an effectual delivery vehicle for plasmid-based modulation of DC-dependent allogeneic T cell responses.