Mammalian and viral IL-10 enhance C-C chemokine receptor 5 but down-regulate C-C chemokine receptor 7 expression by myeloid dendritic cells: impact on chemotactic responses and in vivo homing ability

Breakdown in hepatic tolerance and its relation to autoimmune liver diseases

The liver is a complex immunological organ. It has both immunogenic and tolerogenic capacity. Tolerogenic potential of human liver with its protective firewalls is required to guard the body against the continuous influx of microbial product from the gut via the sinusoids and biliary tree. Immunotolerance and anergic state is maintained by a combined effort of both immune cells, parenchyma cells, epithelial and endothelial cells. Despite this, an unknown trigger can ignite the pathway towards breakdown in hepatic tolerance leading to autoimmune liver diseases. Understanding the initial stimulus which causes the hepatic immune system to switch from the regulatory arm towards self-reactive effector arm remains challenging. Dissecting this pathology using the current technological advances is crucial to develop curative immune based therapy in autoimmune liver diseases. We discuss the hepatic immune cells and non-immune cells which maintain liver tolerance and the evidence of immune system barrier breach which leads to autoimmune hepatitis, primary biliary cholangitis and primary sclerosing cholangitis.

Improving the synergistic combination of programmed death‐1/programmed death ligand‐1 blockade and radiotherapy by targeting the hypoxic tumour microenvironment

Immune checkpoint inhibition with PD‐1/PD‐L1 blockade is a promising area in the field of anti‐cancer therapy. Although clinical data have revealed success of PD‐1/PD‐L1 blockade as monotherapy or in combination with CTLA‐4 or chemotherapy, the combination with radiotherapy could further boost anti‐tumour immunity and enhance clinical outcomes due to the immunostimulatory effects of radiation. However, the synergistic combination of PD‐1/PD‐L1 blockade and radiotherapy can be challenged by the complex nature of the tumour microenvironment (TME), including the presence of tumour hypoxia. Hypoxia is a major barrier to the effectiveness of both radiotherapy and PD‐1/PD‐L1 blockade immunotherapy. Thus, targeting the hypoxic TME is an attractive strategy to enhance the efficacy of the combination. Addition of compounds that directly or indirectly reduce hypoxia, to the combination of PD‐1/PD‐L1 inhibitors and radiotherapy may optimize the success of the combination and improve therapeutic outcomes. In this review, we will discuss the synergistic combination of PD‐1/PD‐L1 blockade and radiotherapy and highlight the role of hypoxic TME in impeding the success of both therapies. In addition, we will address the potential approaches for targeting tumour hypoxia and how exploiting these strategies could benefit the combination of PD‐1/PD‐L1 blockade and radiotherapy.

Regulatory Macrophages and Tolerogenic Dendritic Cells in Myeloid Regulatory Cell-Based Therapies

Myeloid regulatory cell-based therapy has been shown to be a promising cell-based medicinal approach in organ transplantation and for the treatment of autoimmune diseases, such as type 1 diabetes, rheumatoid arthritis, Crohn’s disease and multiple sclerosis. Dendritic cells (DCs) are the most efficient antigen-presenting cells and can naturally acquire tolerogenic properties through a variety of differentiation signals and stimuli. Several subtypes of DCs have been generated using additional agents, including vitamin D3, rapamycin and dexamethasone, or immunosuppressive cytokines, such as interleukin-10 (IL-10) and transforming growth factor-beta (TGF-β). These cells have been extensively studied in animals and humans to develop clinical-grade tolerogenic (tol)DCs. Regulatory macrophages (Mregs) are another type of protective myeloid cell that provide a tolerogenic environment, and have mainly been studied within the context of research on organ transplantation. This review aims to thoroughly describe the ex vivo generation of tolDCs and Mregs, their mechanism of action, as well as their therapeutic application and assessment in human clinical trials.

Targeting hypoxia in the tumor microenvironment: a potential strategy to improve cancer immunotherapy

With the success of immune checkpoint inhibitors (ICIs), significant progress has been made in the field of cancer immunotherapy. Despite the long-lasting outcomes in responders, the majority of patients with cancer still do not benefit from this revolutionary therapy. Increasing evidence suggests that one of the major barriers limiting the efficacy of immunotherapy seems to coalesce with the hypoxic tumor microenvironment (TME), which is an intrinsic property of all solid tumors. In addition to its impact on shaping tumor invasion and metastasis, the hypoxic TME plays an essential role in inducing immune suppression and resistance though fostering diverse changes in stromal cell biology. Therefore, targeting hypoxia may provide a means to enhance the efficacy of immunotherapy. In this review, the potential impact of hypoxia within the TME, in terms of key immune cell populations, and the contribution to immune suppression are discussed. In addition, we outline how hypoxia can be manipulated to tailor the immune response and provide a promising combinational therapeutic strategy to improve immunotherapy.

Antigen-Specific Immunotherapy for Treatment of Autoimmune Liver Diseases

The liver is a critical organ in controlling immune tolerance. In particular, it is now clear that targeting antigens for presentation by antigen presenting cells in the liver can induce immune tolerance to either autoantigens from the liver itself or tissues outside of the liver. Here we review immune mechanisms active within the liver that contribute both to the control of infectious diseases and tolerance to self-antigens. Despite its extraordinary capacity for tolerance induction, the liver remains a target organ for autoimmune diseases. In this review, we compare and contrast known autoimmune diseases of the liver. Currently patients tend to receive strong immunosuppressive treatments and, in many cases, these treatments are associated with deleterious side effects, including a significantly higher risk of infection and associated health complications. We propose that, in future, antigen-specific immunotherapies are adopted for treatment of liver autoimmune diseases in order to avoid such adverse effects. We describe various therapeutic approaches that either are in or close to the clinic, highlight their mechanism of action and assess their suitability for treatment of autoimmune liver diseases.

Tumor microenvironment-related dendritic cell deficiency: a target to enhance tumor immunotherapy

Dendritic cells (DCs), as specialized antigen-presenting cells, are essential for the initiation of specific T cell responses in innate antitumor immunity and, in certain cases, support humoral responses to inhibit tumor development. Mounting evidence suggests that the DC system displays a broad spectrum of dysfunctional status in the tumor microenvironment (TME), which ultimately affects antitumor immune responses. DC-based therapy can restore the function of DCs in the TME, thus showing a promising potential in tumor therapy. In this review, we provide an overview of the DC deficiency caused by various factors in the TME and discuss proposed strategies to reverse DC deficiency and the applications of novel combinatorial DC-based therapy for immune normalization of the tumor.

Viral IL-10 promotes cell proliferation and cell cycle progression via JAK2/STAT3 signaling pathway in nasopharyngeal carcinoma cells

Epstein-Barr virus (EBV) is positively related to the morbidity of nasopharyngeal carcinoma (NPC) in Asia. After infection, EBV can produce several proteins, including viral interleukin-10 (vIL-10). But the mechanism by which vIL-10 contributes to NPC cell proliferation and cell cycle progression is not well understood. In this study, EBV negative and positive cell lines, and the JAK2/STAT3 signal pathway inhibitor AG490 were used to illustrate the role of vIL-10 in NPC. Cell proliferation and cell cycle were measured by CCK-8 and flow cytometry. The expression levels of related protein were measured by Western blotting. High concentrations of vIL-10 and IL-6 were found in the EBV positive patients. The expression level of IL-6 was positively related to the presence of concentration of vIL-10. vIL-10 can promote cancer cell proliferation and G1 to S phase transmission via upregulating the IL-6 protein level by activating the JAK2/STAT3 signal pathway. Furthermore, EBV can induce the formation of cytotoxic T cells, whereas vIL-10 can block the function of cytotoxic T cells. Taken together, these results suggest that vIL-10 promotes cell proliferation and cell cycle progression via JAK2/STAT3 signaling pathway in NPC.

Optimal Tolerogenic Dendritic Cells in Type 1 Diabetes (T1D) Therapy: What Can We Learn From Non-obese Diabetic (NOD) Mouse Models?

Tolerogenic dendritic cells (tolDCs) are explored as a promising standalone or combination therapy in type 1 diabetes (T1D). The therapeutic application of tolDCs, including in human trials, has been tested also in other autoimmune diseases, however, T1D displays some unique features. In addition, unlike in several disease-induced animal models of autoimmune diseases, the prevalent animal model for T1D, the NOD mouse, develops diabetes spontaneously. This review compares evidence of various tolDCs approaches obtained from animal (mainly NOD) models of T1D with a focus on parameters of this cell-based therapy such as protocols of tolDC preparation, antigen-specific vs. unspecific approaches, doses of tolDCs and/or autoantigens, application schemes, application routes, the migration of tolDCs as well as their preventive, early pre-onset intervention or curative effects. This review also discusses perspectives of tolDC therapy and areas of preclinical research that are in need of better clarification in animal models in a quest for effective and optimal tolDC therapies of T1D in humans.

Transendothelial migration (TEM) of in vitro generated dendritic cell vaccine in cancer immunotherapy

Many efforts have been made to improve the efficacy of dendritic cell (DC) vaccines in DC-based cancer immunotherapy. One of these efforts is to deliver a DC vaccine more efficiently to the regional lymph nodes (rLNs) to induce stronger anti-tumor immunity. Together with chemotaxis, transendothelial migration (TEM) is believed to be a critical and indispensable step for DC vaccine migration to the rLNs after administration. However, the mechanism underlying the in vitro-generated DC TEM in DC-based cancer immunotherapy has been largely unknown. Currently, junctional adhesion molecules (JAMs) were found to play an important role in the TEM of in vitro generated DC vaccines. This paper reviews the TEM of DC vaccines and TEM-associated JAM molecules.

The -3279C>A and -924A>G polymorphisms in the FOXP3 Gene Are Associated With Viral Load and Liver Enzyme Levels in Patients With Chronic Viral Liver Diseases

The transcription factor FOXP3 is an essential marker of the development and activation of regulatory T cells (Tregs), which are cells specialized in the regulation and normal tolerance of the immune response. In the context of chronic viral liver diseases, Tregs participate in the maintenance of infections by promoting histopathological control and favor the immune escape of viral agents by suppressing the antiviral response. Single nucleotide polymorphisms (SNPs) may influence the function of FOXP3 in a number of pathological conditions. The present study sought to evaluate the influence of SNPs in the FOXP3 gene promoter region in patients with chronic viral liver diseases. Three SNPs (−3279C>A, −2383C>T, and −924A>G) were analyzed in groups of patients with chronic hepatitis C (CHC), active chronic hepatitis B (CHB-A), inactive chronic hepatitis B (CHB-I), and a healthy control group (CG) using real-time PCR. The frequencies of the polymorphic variants were compared between groups and correlated with liver histopathological characteristics and enzyme levels [i.e., alanine aminotransferase (ALT), aspartate aminotransferase (AST) and gamma-glutamyl transpeptidase (GGT)] obtained via biopsy and from the clinical records of the participating patients, respectively. For the −2338C>T SNP, no significant differences were found in the frequencies of variants between groups or in the histological findings. Significant associations between the polymorphisms and the CHB-I group were not established. The −3279C>A SNP was associated with altered viral loads (log₁₀) and GGT levels in CHC patients with advanced stages of inflammatory activity and liver fibrosis. The −924A>G SNP was associated with altered viral loads (log₁₀) and liver enzyme levels among CHB-A patients with milder inflammation and fibrosis. However, the frequencies of the −3279C>A and −924A>G polymorphisms were not directly associated with the histopathological profiles of the analyzed patients. These polymorphic variants may influence hepatic function in patients with chronic viral liver diseases but are not directly associated with the establishment of the degree of inflammatory activity and liver fibrosis.

Location, location, location: dendritic cell trafficking and transplant tolerance

PURPOSE OF REVIEW

Use or targeting of dendritic cells for therapeutic manipulation of immune responses is being pursued in the areas of cancer, autoimmune disease, and allograft rejection. There is, however, a dearth of information regarding the optimal route of cell delivery or target location for maximal therapeutic effect, particularly in the field of transplantation. Further, little attention has been given to the roles that conventional experimental/immunosuppressive modalities have on the migratory capacity of these important antigen-presenting cells.

RECENT FINDINGS

Current understanding of the role of dendritic cells in immunologic ignorance, graft rejection, or tolerance to alloantigen suggests their function is influenced by subset, secondary lymphoid tissue location, and the type of organ transplanted. It also has been determined recently that dendritic cell subsets probably utilize distinct migratory routes to secondary lymphoid tissues, further underscoring the importance of understanding dendritic cell trafficking for optimization of dendritic cell therapy protocols.

SUMMARY

Increased comprehension of the requirements for dendritic cell-T cell interactions to take place in specific secondary lymphoid tissues for the induction of rejection versus tolerance, with and without antirejection therapy, will facilitate the ease with which cell-based therapy can be designed and implemented in transplant recipients.

Viral IL-10 down-regulates the "MHC-I antigen processing operon" through the NF-κB signaling pathway in nasopharyngeal carcinoma cells

The HLA-I antigen processing machinery (APM) plays a crucial role in the anticancer immune response. The loss of surface expression of HLA-I molecules is particularly important as this enables tumor cells to evade recognition and lysis by cytotoxic T-lymphocytes. Transcriptional control of the APM genes is regulated by the nuclear factor kappa B (NF-κB). BCRFl is an Epstein-Barr virus homologue of human IL-10 (hIL-10) and is known as viral IL-10 (vIL-10). vIL-10 shares many immunosuppressive effects with hIL-10 but lacks the immunostimulatory effect of hIL-10. The aim of this study was to assess whether vIL-10 inhibits APM components (TAP-1, TAP-2, LMP-2, LMP-7 and HLA-I) through the NF-κB signaling pathway in nasopharyngeal carcinoma. This work demonstrated that vIL-10 inhibited NF-κB activation by blocking IKK phosphorylation and promoting the expression of IKB. TNF-α treatment led to a strong translocation of NF-κB p65, whereas pretreatment with vIL-10 before TNF-α treatment blocked NF-κB p65 translocation. vIL-10 also inhibited TNF-α-induced DNA-binding of NF-κB p65 in the nucleus. Furthermore, chromatin immunoprecipitation analysis demonstrated that NF-κB p65 could bind to the TAP-1, TAP-2, LMP-2, LMP-7 and HLA-I gene promoters, and after TNF-α stimulation, the down-regulation of TAP-1, TAP-2, LMP-2, LMP-7 and HLA-I transcription by vIL-10 correlated with the suppression of NF-κB in CNE-2 cells. Surprisingly, vIL-10 inhibits only TAP-1 and LMP-7 transcription in CNE-1 cells. Taken together, these results suggest that the inhibition of NF-κB activity may be an important mechanism for vIL-10 suppression of APM (TAP-1, TAP-2, LMP-2, LMP-7 and HLA-I) gene transcription in CNE-2 cells.

Hypoxia: a key player in antitumor immune response. A Review in the Theme: Cellular Responses to Hypoxia

The tumor microenvironment is a complex system, playing an important role in tumor development and progression. Besides cellular stromal components, extracellular matrix fibers, cytokines, and other metabolic mediators are also involved. In this review we outline the potential role of hypoxia, a major feature of most solid tumors, within the tumor microenvironment and how it contributes to immune resistance and immune suppression/tolerance and can be detrimental to antitumor effector cell functions. We also outline how hypoxic stress influences immunosuppressive pathways involving macrophages, myeloid-derived suppressor cells, T regulatory cells, and immune checkpoints and how it may confer tumor resistance. Finally, we discuss how microenvironmental hypoxia poses both obstacles and opportunities for new therapeutic immune interventions.

FOXO1 regulates dendritic cell activity through ICAM-1 and CCR7

The transcription factor FOXO1 regulates cell function and is expressed in dendritic cells (DCs). We investigated the role of FOXO1 in activating DCs to stimulate a lymphocyte response to bacteria. We show that bacteria induce FOXO1 nuclear localization through the MAPK pathway and demonstrate that FOXO1 is needed for DC activation of lymphocytes in vivo. This occurs through FOXO1 regulation of DC phagocytosis, chemotaxis, and DC-lymphocyte binding. FOXO1 induces DC activity by regulating ICAM-1 and CCR7. FOXO1 binds to the CCR7 and ICAM-1 promoters, stimulates CCR7 and ICAM-1 transcriptional activity, and regulates their expression. This is functionally important because transfection of DCs from FOXO1-deleted CD11c.Cre(+)FOXO1(L/L) mice with an ICAM-1-expressing plasmid rescues the negative effect of FOXO1 deletion on DC bacterial phagocytosis and chemotaxis. Rescue with both CCR7 and ICAM-1 reverses impaired DC homing to lymph nodes in vivo when FOXO1 is deleted. Moreover, Ab production following injection of bacteria is significantly reduced with lineage-specific FOXO1 ablation. Thus, FOXO1 coordinates upregulation of DC activity through key downstream target genes that are needed for DCs to stimulate T and B lymphocytes and generate an Ab defense to bacteria.

Dendritic cells subsets mediated immune response during Plasmodium berghei ANKA and Plasmodium yoelii infection

The roles of dendritic cells (DCs) in mediating immunity against Plasmodium infection have been extensively investigated, but immune response during pathogenesis of malaria is still poorly understood. In the present study, we compared the splenic DCs phenotype and function during P. berghei ANKA (PbA) or P. yoelii (P. yoelii) infection in Swiss mice. We observed that PbA-infected mice developed more myeloid and mature DCs capable of secreting IL-12, while P. yoelii-infected mice had more plasmacytoid and immature DCs secreting higher levels of IL-10. Expression of FoxP3, IL-17, TGF-β and IL-6 were also different between these two infections. Thus, these results suggest that the phenotypic and functional subsets of splenic DCs are key factors for regulating immune responses to PbA and P. yoelii infections.

Generation and in vivo evaluation of IL10-treated dendritic cells in a nonhuman primate model of AAV-based gene transfer

Preventing untoward immune responses against a specific antigen is a major challenge in different clinical settings such as gene therapy, transplantation, or autoimmunity. Following intramuscular delivery of recombinant adeno-associated virus (rAAV)-derived vectors, transgene rejection can be a roadblock to successful clinical translation. Specific immunomodulation strategies potentially leading to sustained transgene expression while minimizing pharmacological immunosuppression are desirable. Tolerogenic dendritic cells (TolDC) are potential candidates but have not yet been evaluated in the context of gene therapy, to our knowledge. Following intramuscular delivery of rAAV-derived vectors expressing an immunogenic protein in the nonhuman primate model, we assessed the immunomodulating potential of autologous bone marrow-derived TolDC generated in the presence of IL10 and pulsed with the transgene product. TolDC administered either intradermally or intravenously were safe and well tolerated. While the intravenous route showed a modest ability to modulate host immunity against the transgene product, intradermally delivery resulted in a robust vaccination of the macaques when associated to intramuscular rAAV-derived vectors-based gene transfer. These findings demonstrate the critical role of TolDC mode of injection in modulating host immunity. This study also provides the first evidence of the potential of TolDC-based immunomodulation in gene therapy.

An autologous in situ tumor vaccination approach for hepatocellular carcinoma. 1. Flt3 ligand gene transfer increases antitumor effects of a radio-inducible suicide gene therapy in an ectopic tumor model

Hepatocellular carcinoma (HCC) often presents as a diffuse or multifocal tumor making it difficult to control by surgery or radiation. Radio-inducible herpes simplex virus thymidine kinase (HSV-TK) gene therapy has been shown to enhance local tumor control after radiation therapy (RT), while limiting the expression of the transgene in the irradiated tumor tissues. To prevent liver tumor recurrence and control systemic disease while limiting the potential bystander toxicity of HSV-TK therapy, we proposed to stimulate endogenous dendritic cell (DC) proliferation with systemic adenovirus Flt3 ligand (Adeno-Flt3L) gene therapy, followed by primary tumor radiation therapy combined with a radio-inducible HSV-TK gene therapy. We hypothesized that adenovirus-expressing Flt3L gene therapy will stimulate DC proliferation, allowing the upregulated DCs to locally harness tumor antigens released from HSV-TK/RT-treated HCC cells, thereby converting irradiated tumors to an autologous in situ tumor vaccine in mice with primary liver tumors. To test this hypothesis, an expression vector of HSV-TK was constructed under the control of a radio-inducible promoter early-growth response (Egr-TK) and a recombinant adenovirus-expressing human Flt3L was constructed. The Adeno-Flt3L [10(9) plaque forming units (pfu)] was administered intravenously on days 1 and 8 after radiation therapy. The murine hepatoma cell line (BNL1ME) was stably transfected by Egr-TK or Egr-Null (encoding no therapeutic gene). Palpable tumors in BALB/c mice were treated with a localized dose of 25 Gy of radiation followed by ganciclovir (GCV, 100 mg/kg, 14 days). Four treatment cohorts were compared: Egr-Null/GCV + RT + Adeno-LacZ; Egr-Null/GCV + RT + Adeno-Flt3L; Egr-TK/GCV + RT + Adeno-LacZ; and Egr-TK/GCV + RT + Adeno-Flt3L. There was no primary tumor regression in the Egr-Null tumors after radiation therapy alone. In contrast, Egr-TK tumors had nearly complete tumor regression for 3 weeks after radiation therapy (P < 0.01), however, long-term follow-up demonstrated primary tumor recurrence and death secondary to pulmonary metastasis. Flt3L expression was confirmed by serum bioassay (mean = 88 ng/mL) in these animals and Western blotting of tissue culture medium in Adeno-Flt3L-infected BaF/huFlt3L cells. Radiation therapy with Adeno-Flt3L gene therapy effectively retarded primary tumor growth when compared to radiation therapy alone. The trimodality therapy (Egr-TK/GCV + RT + Adeno-Flt3L) was the most efficacious with 40% complete tumor regression (>100 days) and <20% pulmonary metastases, indicating the development of sustained antitumor immune response. These studies provide a rationale for triple modality therapies with radiation-inducible HSV-TK gene therapy and Adeno-Flt3L when used in combination with primary tumor radiation therapy for improved local and systemic control of HCC.

B-cell modulation of dendritic-cell function: signals from the far side

An appropriate immune response against a specific pathogen requires finely orchestrated interactions between the various cell populations within the immune system. At the same time, immunological tolerance to self must be maintained. DCs play an essential role in achieving these dual requisites. They coordinate adaptive immunity by integrating signals directly emanating from both infectious agents and cells of the immune system. Many such signals, especially those from innate cells and T cells, have been extensively characterized. In contrast, little is known about how B cells modulate function of DCs. B cells produce a variety of cytokines, including IL-10 and IL-6, which are known to influence DC function. In addition, Igs constitute the major secretory products of terminally differentiated B cells (plasma cells). DCs express various types of receptors for binding Ig, such as Fc receptors and C-type lectin receptors. In accordance, Igs can regulate DC function depending on the receptors engaged. Here, we review the emerging immunomodulatory role of cytokines and Ig secreted by B cells. We discuss the evidence for how these B-cell-derived factors may shape the adaptive immune response by directly acting on DCs.

Regulatory myeloid cells in transplantation

Regulatory myeloid cells (RMC) are emerging as novel targets for immunosuppressive (IS) agents and hold considerable promise as cellular therapeutic agents. Herein, we discuss the ability of regulatory macrophages, regulatory dendritic cells, and myeloid-derived suppressor cells to regulate alloimmunity, their potential as cellular therapeutic agents, and the IS agents that target their function. We consider protocols for the generation of RMC and the selection of donor- or recipient-derived cells for adoptive cell therapy. Additionally, the issues of cell trafficking and antigen (Ag) specificity after RMC transfer are discussed. Improved understanding of the immunobiology of these cells has increased the possibility of moving RMC into the clinic to reduce the burden of current IS agents and to promote Ag-specific tolerance. In the second half of this review, we discuss the influence of established and experimental IS agents on myeloid cell populations. IS agents believed historically to act primarily on T cell activation and proliferation are emerging as important regulators of RMC function. Better insights into the influence of IS agents on RMC will enhance our ability to develop cell therapy protocols to promote the function of these cells. Moreover, novel IS agents may be designed to target RMC in situ to promote Ag-specific immune regulation in transplantation and to usher in a new era of immune modulation exploiting cells of myeloid origin.

Dendritic cell-based approaches for therapeutic immune regulation in solid-organ transplantation

To avoid immune rejection, allograft recipients require drug-based immunosuppression, which has significant toxicity. An emerging approach is adoptive transfer of immunoregulatory cells. While mature dendritic cells (DCs) present donor antigen to the immune system, triggering rejection, regulatory DCs interact with regulatory T cells to promote immune tolerance. Intravenous injection of immature DCs of either donor or host origin at the time of transplantation have prolonged allograft survival in solid-organ transplant models. DCs can be treated with pharmacological agents before injection, which may attenuate their maturation in vivo. Recent data suggest that injected immunosuppressive DCs may inhibit allograft rejection, not by themselves, but through conventional DCs of the host. Genetically engineered DCs have also been tested. Two clinical trials in type-1 diabetes and rheumatoid arthritis have been carried out, and other trials, including one trial in kidney transplantation, are in progress or are imminent.

IL-10 conditioning of human skin affects the distribution of migratory dendritic cell subsets and functional T cell differentiation

In cancer patients pervasive systemic suppression of Dendritic Cell (DC) differentiation and maturation can hinder vaccination efficacy. In this study we have extensively characterized migratory DC subsets from human skin and studied how their migration and T cell-stimulatory abilities were affected by conditioning of the dermal microenvironment through cancer-related suppressive cytokines. To assess effects in the context of a complex tissue structure, we made use of a near-physiological skin explant model. By 4-color flow cytometry, we identified migrated Langerhans Cells (LC) and five dermis-derived DC populations in differential states of maturation. From a panel of known tumor-associated suppressive cytokines, IL-10 showed a unique ability to induce predominant migration of an immature CD14(+)CD141(+)DC-SIGN(+) DC subset with low levels of co-stimulatory molecules, up-regulated expression of the co-inhibitory molecule PD-L1 and the M2-associated macrophage marker CD163. A similarly immature subset composition was observed for DC migrating from explants taken from skin overlying breast tumors. Whereas predominant migration of mature CD1a(+) subsets was associated with release of IL-12p70, efficient Th cell expansion with a Th1 profile, and expansion of functional MART-1-specific CD8(+) T cells, migration of immature CD14(+) DDC was accompanied by increased release of IL-10, poor expansion of CD4(+) and CD8(+) T cells, and skewing of Th responses to favor coordinated FoxP3 and IL-10 expression and regulatory T cell differentiation and outgrowth. Thus, high levels of IL-10 impact the composition of skin-emigrated DC subsets and appear to favor migration of M2-like immature DC with functional qualities conducive to T cell tolerance.

Cell therapy using tolerogenic dendritic cells in transplantation

Organ transplantation is the main alternative to the loss of vital organ function from various diseases. However, to avoid graft rejection, transplant patients are treated with immunosuppressive drugs that have adverse side effects. A new emerging approach to reduce the administration of immunosuppressive drugs is to co-treat patients with cell therapy using regulatory cells. In our laboratory, as part of a European project, we plan to test the safety of tolerogenic dendritic cell (TolDC) therapy in kidney transplant patients. In this mini-review, we provide a brief summary of the major protocols used to derive human TolDC, and then focus on the granulocyte macrophage-TolDC generated by our own team. Proof of safety of TolDC therapy in the clinic has already been demonstrated in patients with diabetes. However, in transplantation, DC therapy will be associated with the administration of immunosuppressive drugs, and interactions between drugs and DC are possible. Finally, we will discuss the issue of DC origin, as we believe that administration of autologous TolDC is more appropriate, as demonstrated by our experiments in animal models.

Tumor associated regulatory dendritic cells

Immune effector and regulatory cells in the tumor microenvironment are key factors in tumor development and progression as the pathogenesis of cancer vitally depends on the multifaceted interactions between various microenvironmental stimuli provided by tumor-associated immune cells. Immune regulatory cells participate in all stages of cancer development from the induction of genomic instability to the maintenance of intratumoral angiogenesis, proliferation and spreading of malignant cells, and formation of premetastatic niches in distal tissues. Dendritic cells in the tumor microenvironment serve as a double-edged sword and, in addition to initiating potent anti-tumor immune responses, may mediate genomic damage, support neovascularization, block anti-tumor immunity and stimulate cancerous cell growth and spreading. Regulatory dendritic cells in cancer may directly and indirectly maintain antigen-specific and non-specific T cell unresponsiveness by controlling T cell polarization, MDSC and Treg differentiation and activity, and affecting specific microenvironmental conditions in premalignant niches. Understanding the mechanisms involved in regulatory dendritic cell polarization and operation and revealing pharmacological means for harnessing these pathways will provide additional opportunities for modifying the tumor microenvironment and improving the efficacy of different therapeutic approaches to cancer.

Induction of pathogenic cytotoxic T lymphocyte tolerance by dendritic cells: a novel therapeutic target

IMPORTANCE OF THE FIELD

Dendritic cells (DCs) have an important role, both direct and indirect, in controlling the expansion and function of T cells. Of the different subsets of T cells, cytotoxic T lymphocytes (CTLs/CD8(+) T cells) have been implicated in the pathogenesis and development of many diseases, including various forms of autoimmunity and transplant rejection. It may therefore be of therapeutic benefit to control the function of CTL in order to modulate disease processes and to ameliorate disease symptoms. Currently, pharmacological approaches have been employed to either directly or indirectly modulate the function of T cells. However, these treatment strategies have many limitations. Many experimental data have suggested that it is possible to alter CTL activity through manipulation of DC.

AREAS COVERED IN THIS REVIEW

Novel strategies that condition DCs to influence disease outcome through manipulation of CTL activity, both directly and indirectly. This includes the modulation of co-stimulation, negative co-stimulation, as well as manipulation of the cytokine milieu during CTL generation. Furthermore, DCs may also impact CTL activity through effects on effector and regulatory cells, along with manipulation of bioenergetic regulation, apoptotic-cell mediated tolerance and through the generation of exosomes. The implications of related interventions in the clinical arena are in turn considered.

WHAT THE READER WILL GAIN

Insight into such indirect methods of controlling CTL activity allows for an understanding of how disease-specific T cells may be regulated, while also sparing other aspects of adaptive immunity for normal physiological function. Such an approach towards the treatment of disease represents an innovative therapeutic target in the clinical arena.

TAKE HOME MESSAGE

There are numerous innovative methods for using DCs to control CTL responses. Manipulation of this interaction is thus an attractive avenue for the treatment of disease, particularly those of immune dysregulation, such as seen in autoimmunity and transplantation. With the number of studies moving into clinical stages constantly increasing, further advances and successes in this area are inevitable.

Actobiotics as a novel method for cytokine delivery

Interleukin-10 (IL-10) is central in immune downregulation, but so far its use in inflammatory diseases remains cumbersome. For treatment of inflammatory bowel disease, adequate amounts of IL-10 must reach the intestinal lining. Systemic injection of a pharmacologically active doses of recombinant human (rh) IL-10 results in very low mucosal levels of protein and severe toxicity and side effects. In animal models, topical and active delivery of IL-10 by ingestion of recombinant Lactococcus lactis (L. lactis) was shown to be a valuable alternative. Starting thereof we have developed a novel pharmaceutical platform. Our expertise and TopAct (topical and active) delivery technology allows use of recombinant L. lactis- ActoBiotics- in clinical practice. Here we discuss the development of recombinant L. lactis for intestinal delivery of rhIL-10 in humans.

In vitro maturation and migration of immature dendritic cells after chemokine receptor 7 transfection

Dendritic cells are specialized antigen-presenting cells that regulate immunity and tolerance. Chemokine receptor 7 (CCR7), which is expressed by mature dendritic cells, mediates the migration of the cells to secondary lymphoid organs and thus regulates immune responses. It has been demonstrated that immature dendritic cells can induce immune tolerance, but they do not express CCR7 and cannot migrate to secondary lymphoid organs. We transfected immature dendritic cells with a recombinant adenovirus carrying the CCR7 gene to obtain immature dendritic cells with the ability to migrate. The maturity of the cells was monitored by scanning electron microscopy and flow cytometry. In addition, we assessed the ability of cells to migrate and the function of the cells using in vitro chemotactic and mixed leukocyte reaction assays. The results showed that immature dendritic cells became semi-mature, exhibiting a mild upregulation of co-stimulatory molecular expression and a few dendritic processes. Immunofluorescence assay and Western blotting indicated that CCR7 protein expression increased significantly in immature dendritic cells following CCR7 gene transfection. The in vitro chemotactic assay showed a significantly enhanced ability to migrate in response to CCL19 following CCR7 gene transfection. Moreover, transfected cells showed an enhanced ability to stimulate allogeneic T cell proliferation in vitro, but their ability was significantly weaker than that of mature dendritic cells. Interleukin-10 inhibited the differentiation and maturation of immature dendritic cells. It is concluded that, following CCR7 gene transfection, immature dendritic cells exhibit an enhanced ability to migrate and some of the characteristics of mature cells. Thus, these cells are of potential clinical significance in studies of immune tolerance induction during skin grafting after severe burns.

Immune tolerance: what is unique about the liver

The 'liver tolerance effect' mediates local and systemic tolerance to self and foreign antigens and has been attributed to specialized resident cells expressing anti-inflammatory mediators and inhibitory cell surface ligands for T cell activation. Non-parenchymal liver cells responsible for the tolerogenic properties of the liver are the resident dendritic cells (DCs), which comprise myeloid as well as plasmacytoid DCs, liver sinusoidal endothelial cells (LSECs), Kupffer cells (KCs) as well as hepatic stellate cells (HSCs), also known as Ito cells. These cells mediate immunosuppression by production of anti-inflammatory cytokines such as IL-10 and TGFbeta as well as by expression of the negative co-stimulator for T cell activation programmed cell death ligand-1 (PD-L1). An interesting observation in this context is that knockout of IL-10 or PD-L1 (or the receptor PD-1) does not necessarily result in inflammatory liver damage whereas transgenic inhibition of TGFbeta signaling induces liver disease in mice resembling chronic cholangitis. However, depending on the mouse model and on the type of injury, e.g. autoimmune disease, allograft rejection or viral infection, IL-10 or TGFbeta and/or PD-1 as well as cytotoxic T lymphocyte antigen-4 (CTLA-4) contribute to the immunosuppressive mechanisms of CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs), which seem to be converted in the liver from infiltrating conventional naïve CD4(+) T cells and/or effector CD4(+) T cells to control the disease. Finally, hepatocytes also contribute to the 'liver tolerance effect' by expression of MHC class II molecules, probably low levels of co-stimulatory molecules and high levels of the co-inhibitory molecule PD-L1.

Dendritic cells and chemokine-directed migration in transplantation: where are we headed?

The role of dendritic cells (DC) in transplantation is often overshadowed by the more prominent roles of T and B cells, which interact directly with and, in the absence of immunosuppressive therapy, destroy the allograft. It has become increasingly recognized, however, that these potent antigen-presenting cells exert control over the immune response and regulate the balance between tolerance and immunity to transplanted organs and tissues. The role that chemokines play in influencing DC function with impact on regulation of immune responses against the graft is only beginning to be understood. This article considers how the manipulation of DC trafficking during an alloimmune response can affect graft outcome.

Divergent effects of hypoxia on dendritic cell functions

Dendritic cells (DCs) are professional antigen-presenting cells (APCs) that patrol tissues to sense danger signals and activate specific immune responses. In addition, they also play a role in inflammation and tissue repair. Here, we show that oxygen availability is necessary to promote full monocyte-derived DC differentiation and maturation. Low oxygen tension (hypoxia) inhibits expression of several differentiation and maturation markers (CD1a, CD40, CD80, CD83, CD86, and MHC class II molecules) in response to lipopolysaccharide (LPS), as well as their stimulatory capacity for T-cell functions. These events are paralleled by impaired up-regulation of the chemokine receptor CCR7, an otherwise necessary event for the homing of mature DCs to lymph nodes. In contrast, hypoxia strongly up-regulates production of proinflammatory cytokines, particularly TNFalpha and IL-1beta, as well as the inflammatory chemokine receptor CCR5. Subcutaneous injection of hypoxic DCs into the footpads of mice results in defective DC homing to draining lymph nodes, but enhanced leukocyte recruitment at the site of injection. Thus, hypoxia uncouples the promotion of inflammatory and tissue repair from sentinel functions in DCs, which we suggest is a safeguard mechanism against immune reactivity to damaged tissues.

Phenotypic and functional characterization of mature dendritic cells from pediatric cancer patients

BACKGROUND

Dendritic cells (DCs) are the most potent antigen-presenting cells of the immune system. Clinical trials have demonstrated that mature DCs loaded with tumor-associated antigens can induce tumor-specific immune responses. Theoretically, pediatric patients are excellent candidates for immunotherapy since their immune system is more potent compared to adults. We studied whether sufficient amounts of mature monocyte-derived DCs can be cultured from peripheral blood of pediatric cancer patients.

PROCEDURE

DCs from 15 pediatric patients with an untreated primary tumor were cultured from monocytes and matured with clinical grade cytokines. Phenotype and function were tested with flow cytometry, mixed lymphocyte reaction (MLR), and an in vitro migration assay. DCs of children with a solid tumor were compared with monocyte-derived DCs from age-related non-malignant controls.

RESULTS

Ex vivo-generated monocyte-derived DCs from pediatric patients can be generated in numbers sufficient for DC vaccination trials. Upon cytokine stimulation the DCs highly upregulate the expression of the maturation markers CD80, CD83, and CD86. The mature DCs are six times more potent in inducing T cell proliferation compared to immature DCs. Furthermore, mature DCs, but not immature DCs, express the chemokine receptor CCR7 and have the capacity to migrate in vitro.

CONCLUSIONS

These data indicate that mature DCs can be generated ex vivo to further optimize DC-vaccination trials in pediatric cancer patients.

Cloning and characterization of recombinant rhesus macaque IL-10/Fc(ala-ala) fusion protein: a potential adjunct for tolerance induction strategies

The powerful anti-inflammatory and immunosuppressive activities of IL-10 make it attractive for supplemental therapy in translational tolerance induction protocols. This is bolstered by reports of IL-10-mediated inhibition of innate immunity, association of human stem cell and nonhuman primate (NHP) islet allograft tolerance with elevated serum IL-10, and evidence that systemic IL-10 therapy enhanced pig islets survival in mice. IL-10 has not been examined as adjunctive immunosuppression in NHP. To enable such studies, we cloned and expressed rhesus macaque (RM) IL-10 fused to a mutated hinge region of human IgG1 Fc to generate IL-10/Fc(ala-ala). RM IL-10/Fc(ala-ala) was purified to approximately 98% homogeneity by affinity chromatography and shown to be endotoxin-free (<0.008 EU/microg protein). The biological activity of IL-10/Fc(ala-ala) was demonstrated by (1) costimulation of the mouse mast cell line, MC/9 proliferation in a dose-dependent fashion, (2) suppression of LPS-induced septic shock in mice and (3) abrogation of LPS-induced secretion of proinflammatory cytokines/chemokines in vitro and in vivo in NHP. Notably, RM IL-10/Fc(ala-ala) had significantly greater potency than human IL-10/Fc(ala-ala) and exhibited a circulating half-life of approximately 14 days. The availability of this reagent will facilitate definitive studies to determine whether supplemental therapy with RM IL-10/Fc(ala-ala) can influence tolerance outcomes in NHP.

TGF-beta insensitive dendritic cells: an efficient vaccine for murine prostate cancer

Dendritic cells (DCs) are highly potent initiators of the immune response, but DC effector functions are often inhibited by immunosuppressants such as transforming growth factor beta (TGF-beta). The present study was conducted to develop a treatment strategy for prostate cancer using a TGF-beta-insensitive DC vaccine. Tumor lysate-pulsed DCs were rendered TGF-beta insensitive by dominant-negative TGF-beta type II receptor (TbetaRIIDN), leading to the blockade of TGF-beta signals to members of the Smad family, which are the principal cytoplasmic intermediates involved in the transduction of signals from TGF-beta receptors to the nucleus. Expression of TbetaRIIDN did not affect the phenotype of transduced DCs. Phosphorylated Smad-2 was undetectable and expression of surface co-stimulatory molecules (CD80/CD86) were upregulated in TbetaRIIDN DCs after antigen and TGF-beta1 stimulation. Vaccination of C57BL/6 tumor-bearing mice with the TbetaRIIDN DC vaccine induced potent tumor-specific cytotoxic T lymphocyte responses against TRAMP-C2 tumors, increased serum IFN-gamma and IL-12 level, inhibited tumor growth and increased mouse survival. Furthermore, complete tumor regression occurred in two vaccinated mice. These results demonstrate that blocking TGF-beta signals in DC enhances the efficacy of DC-based vaccines.

Retinoid-related orphan receptor gamma controls immunoglobulin production and Th1/Th2 cytokine balance in the adaptive immune response to allergen

The retinoid-related orphan receptors (ROR) comprise a distinct subfamily of nuclear receptors with the capacity to act as both repressors and activators of transcription. RORgamma, the most recently identified member of the ROR family, has been shown to be important for the development of normal lymphocyte compartments as well as organogenesis of some lymphoid organs. In this report, we examine the capacity of RORgamma-deficient mice to develop an adaptive immune response to Ag using OVA-induced inflammation in mice as a model for allergic airway disease. In sham-treated mice lacking RORgamma, low-grade pulmonary inflammation was observed and characterized by the perivascular accumulation of B and T lymphocytes, increased numbers of inflammatory cells in the lung lavage fluid, and polyclonal Ig activation. Following sensitization and challenge, the capacity of these animals to develop the allergic phenotype was severely impaired as evidenced by attenuated eosinophilic pulmonary inflammation, reduced numbers of CD4+ lymphocytes, and lower Th2 cytokines/chemokine protein and mRNA expression in the lungs. IFN-gamma and IL-10 production was markedly greater in splenocytes from RORgamma-deficient mice following in vitro restimulation with OVA compared with wild-type splenocytes, and a shift toward a Th1 immune response was observed in sensitized/challenged RORgamma-deficient animals in vivo. These data reveal a critical role for RORgamma in the regulation of Ig production and Th1/Th2 balance in adaptive immunity.

Cure of chronic viral infection by neutralizing antibody treatment

Persistent infections can pose severe health risks. In many cases individuals fail to clear the virus and consequently chronic infection, often associated with severe immunopathology, occurs. For some chronic infections it is known that systemic IL-10 production can be increased. However, it is unclear, whether IL-10 affects the outcome of infection, amount of immunopathology and could be the actual cause for persistence. Conventional interferons (IFN) or anti-viral immunotherapies attempting to augment anti-viral immunity directly in persistent infected individuals have failed to affect the outcome so far, but lowering the viral antigenic load has clear beneficial effects. Therefore, approaching the problem from a different angle is important. The use of neutralizing antibodies is one of the most successful methods to interfere with receptor-ligand interactions in vivo. Optimal designs of therapeutic antibody treatment regimen are important in order to achieve maximal effects with minimal duration of immunosuppression or hyperactivation. In this review we reflect on the effects of a short time administration of a neutralizing cytokine receptor antibody treatment of a chronic infection resulting in the establishment of anti-viral immune responses and viral clearance and speculate on the potential mechanisms involved in this successful therapeutic treatment.

Intratumoral cytokines/chemokines/growth factors and tumor infiltrating dendritic cells: friends or enemies?

The tumor microenvironment consists of a variable combination of tumor cells, stromal fibroblasts, endothelial cells and infiltrating leukocytes, such as macrophages, T lymphocytes, and dendritic cells. A variety of cytokines, chemokines and growth factors are produced in the local tumor environment by different cells accounting for a complex cell interaction and regulation of differentiation, activation, function and survival of multiple cell types. The interaction between cytokines, chemokines, growth factors and their receptors forms a comprehensive network at the tumor site, which is primary responsible for overall tumor progression and spreading or induction of antitumor immune responses and tumor rejection. Although the general thought is that dendritic cells are among the first cells migrating to the tumor site and recognizing tumor cells for the induction of specific antitumor immunity, the clinical relevance of dendritic cells at the site of the tumor remains a matter of debate regarding their role in the generation of successful antitumor immune responses in human cancers. While several lines of evidence suggest that intratumoral dendritic cells play an important role in antitumor immune responses, understanding the mechanisms of dendritic cell/tumor cell interaction and modulation of activity and function of different dendritic cell subtypes at the tumor site is incomplete. This review is limited to discussing the role of intratumoral cytokine network in the understanding immunobiology of tumor-associated dendritic cells, which seems to possess different regulatory functions at the tumor site.

Involvement of leptin signaling in the survival and maturation of bone marrow-derived dendritic cells

Previous studies demonstrated that lymphocyte development is impaired in leptin receptor (Ob-R)-deficient db/db mice. However, it remains unclear whether or not leptin signaling plays a physiological role in dendritic cell (DC) development and function. In this study, we first detected Ob-R expression in murine DC. Using db/db mice at a pre-diabetic stage, we demonstrate that the total number of DC generated from bone marrow (BM) cultures is significantly lower than in WT controls. Similarly, selective blockade of leptin with a soluble mouse Ob-R chimera (Ob-R:Fc) inhibited DC generation in wild-type BM cultures. The reduced DC yield in db/db BM culture was attributed to significantly increased apoptosis, which was associated with dysregulated expression of Bcl-2 family genes. Moreover, db/db DC displayed markedly reduced expression of co-stimulatory molecules and a Th2-type cytokine profile, with a poor capacity to stimulate allogeneic T cell proliferation. Consistent with their impaired DC phenotype and function, db/db DC showed significantly down-regulated activities of the PI3K/Akt pathway as well as STAT-3 and IkappaB-alpha. In conclusion, our findings demonstrate the involvement of leptin signaling in DC survival and maturation.

Cure of chronic viral infection and virus-induced type 1 diabetes by neutralizing antibodies

The use of neutralizing antibodies is one of the most successful methods to interfere with receptor-ligand interactions in vivo. In particular blockade of soluble inflammatory mediators or their corresponding cellular receptors was proven an effective way to regulate inflammation and/or prevent its negative consequences. However, one problem that comes along with an effective neutralization of inflammatory mediators is the general systemic immunomodulatory effect. It is therefore important to design a treatment regimen in a way to strike at the right place and at the right time in order to achieve maximal effects with minimal duration of immunosuppression or hyperactivation. In this review we reflect on two examples of how short time administration of such neutralizing antibodies can block two distinct inflammatory consequences of viral infection. First, we review recent findings that blockade of IL-10/IL-10R interaction can resolve chronic viral infection and second, we reflect on how neutralization of the chemokine CXCL10 can abrogate virus-induced type 1 diabetes.

Design of bifunctional siRNAs: Combining immunostimulation and gene-silencing in one single siRNA molecule

Active suppression of T lymphocyte activation can limit the efficacy of immune surveillance and immunotherapy. Here we have explored the possibility of designing bifunctional small interfering RNAs (siRNAs) capable of inducing innate immunity through Toll-like receptors and simultaneously inhibiting the expression of immunosuppressive factors. Using interleukin (IL) 10 as a model, we found that liposomal delivery of IL10 siRNAs could efficiently activate the expression of cytokines (e.g. TNF-alpha, IL6, and IL12) and interferons (e.g. IFN-alpha) in peripheral blood mononuclear cells (PBMCs) and immature monocyte-derived dendritic cells (iMoDCs). Moreover, the designed siRNAs inhibited IL10 gene expression. Transfection of iMoDCs with either chemically or in vitro transcribed IL10 siRNAs induced their differentiation into mature MoDCs (mMoDCs) characterized by the expression of costimulatory molecules CD80/CD86 and the chemokine receptor CCR7. Lipid delivery of either chemically synthesized or T7-transcribed immunostimulatory siRNAs induced cytokine production. However, in contrast to chemically synthesized siRNAs, electroporation of in vitro transcribed siRNAs also induced cytokine production in iMoDCs. Interestingly, IL10 siRNA-transfected iMoDCs were capable for enhancing the response of allogeneic T cells, providing support for the rational design of bifunctional siRNAs as immune modulating therapy.

Differential effects of immunosuppressive drugs on chemokine receptor CCR7 in human monocyte-derived dendritic cells: selective upregulation by rapamycin

BACKGROUND

Appropriate recruitment of dendritic cells (DC) at sites of inflammation and migration to secondary lymphoid organs is of critical importance for the initiation of Ag-specific immune responses. The proper localization of DC in selected tissues is guided primarily by the coordinated expression of chemokine receptors (CKR). Here we show that immunosuppressive drugs have divergent effects on the modulation of CKR in maturing DC.

METHODS AND RESULTS

Dexamethazone (DEX) and IL-10 inhibited human DC migration to CCL19 in vitro and mouse DC migration to lymph nodes (LN) in vivo, by impairing CCR7 expression. The calcineurin inhibitors cyclosporine A (CsA) and tacrolimus (FK506) were characterized by the inability to modulate CKR expression and migratory activity. Rapamycin (RAPA) increased DC migration to CCL19 in vitro and to LN in vivo by enhancing CCR7 expression. This effect could be mediated, in LPS-maturing DC, by the inhibition of autocrine IL-10 production. The in vivo data obtained with ex vivo RAPA treated DC were confirmed in a model of in vivo drug administration in mice, suggesting a potential clinical relevance.

CONCLUSIONS

These findings demonstrate that immunosuppressive agents differently modulate the CKR switch associated with maturing DC; in particular, RAPA selectively up-regulates CCR7 and enhances the migration of differentiated DC to regional LN. This study contributes to a better understanding of the role of immunosuppressive therapy on DC migration, a potentially relevant check point of immunosuppressive treatment.

Preferential involvement of Tim-3 in the regulation of hepatic CD8+ T cells in murine acute graft-versus-host disease

Tim-3, a member of the T cell Ig mucin (TIM) family regulates effector Th1 responses. We examined Tim-3 and its ligand expression as well as the effects of anti-Tim-3 mAb treatment in a murine model of acute graft-vs-host disease (aGVHD). In mice with aGVHD, Tim-3 expression was markedly up-regulated on splenic and hepatic CD4+ and CD8+ T cells, dendritic cells (DCs), and macrophages, and this was especially dramatic in hepatic CD8+ T cells. Both donor- and host-derived CD8+ T cells induced similar levels of Tim-3. Tim-3 ligand expression was also up-regulated in splenic T cells, DCs, and macrophages, but not in the hepatic lymphocytes. The administration of anti-Tim-3 mAbs accelerated aGVHD, as demonstrated by body weight loss, reduction in total splenocyte number, and infiltration of lymphocytes in the liver. IFN-gamma expression by splenic and hepatic CD4+ and CD8+ T cells was significantly augmented by anti-Tim-3 mAb treatment. In addition, the cytotoxicity against host alloantigen by donor CD8+ T cells was enhanced. These results demonstrate that the anti-Tim-3 treatment in aGVHD augmented the activation of effector T cells expressing IFN-gamma or exerting cytotoxicity. Our results suggest that Tim-3 may play a crucial role in the regulation of CD8+ T cells responsible for the maintenance of hepatic homeostasis and tolerance.

Immunomodulation of the melanoma sentinel lymph node: a novel adjuvant therapeutic option

Cutaneous melanoma is the most aggressive type of skin cancer. Paradoxically, melanoma is also the most immunogenic tumour identified to date: tumour-reactive T cells are detectable both in the blood and in tumour-draining lymph nodes (TDLN) of melanoma patients and their frequency can be increased by specific vaccination. However, early melanoma development is accompanied by impaired immune effector functions in the initial TDLN, the sentinel lymph node (SLN). Most notably, a reduced frequency and activation state of dendritic cells (DC) interferes with the uptake and presentation of tumour-associated antigens (TAA) to specific anti-tumour cytotoxic T-lymphocytes (CTL) and T helper cells (Th). These impaired immune effector functions may contribute to the early metastatic events that are associated with this tumour type. Since complete surgical excision at an early stage remains the only curative treatment option (adjuvant therapy options are limited and show no survival benefits), immunopotentiation of the SLN to jump-start or boost tumour specific immunity in early stage melanoma may be a valuable adjuvant treatment option that can be generally applied with minimal discomfort to the patient. Early clinical studies indicate that local Granulocyte/Macrophage-Colony Stimulating Factor (GM-CSF) or Cytosine-phosphate-Guanine (CpG) administration leads to activation of different DC subsets and conditions the SLN microenvironment to be more conducive to the generation of T-cell-mediated anti-tumour immunity.

A postmigrational switch among skin-derived dendritic cells to a macrophage-like phenotype is predetermined by the intracutaneous cytokine balance

Migration of dendritic cells (DC) to secondary lymphoid organs under proinflammatory conditions coincides with their maturation and acquisition of T cell stimulatory abilities. In contrast, impaired activation of DC, e.g., in tumor-conditioned environments, may hamper their activation and possibly their subsequent migration to lymph nodes, leading to either immunological tolerance or ignorance, respectively. In this study, the influence of cytokines in the peripheral skin microenvironment on the activation state of migrating cutaneous DC was assessed using an ex vivo human skin explant model. We observed a phenotypic shift from mature CD83(+) DC to immature CD14(+) macrophage-like cells within 7 days subsequent to migration from unconditioned skin. These macrophage-like cells displayed a poor T cell stimulatory ability and lacked expression of CCR7, thus precluding their migration to paracortical T cell areas in the lymph nodes. The balance of suppressive and stimulatory cytokines during the initiation of migration decided the postmigrational fate of DC with IL-10 accelerating and GM-CSF and IL-4 preventing the phenotypic switch, which proved irreversible once established. These observations indicate that, in immunosuppressed environments, a postmigrational DC-to-macrophage shift may hinder T cell activation, but also that it may be prevented by prior conditioning of the tissue microenvironment by GM-CSF and/or IL-4.

Cure of chronic viral infection and virus-induced type 1 diabetes by neutralizing antibodies

The use of neutralizing antibodies is one of the most successful methods to interfere with receptor-ligand interactions in vivo. In particular blockade of soluble inflammatory mediators or their corresponding cellular receptors was proven an effective way to regulate inflammation and/or prevent its negative consequences. However, one problem that comes along with an effective neutralization of inflammatory mediators is the general systemic immunomodulatory effect. It is, therefore, important to design a treatment regimen in a way to strike at the right place and at the right time in order to achieve maximal effects with minimal duration of immunosuppression or hyperactivation. In this review, we reflect on two examples of how short time administration of such neutralizing antibodies can block two distinct inflammatory consequences of viral infection. First, we review recent findings that blockade of IL-10/IL-10R interaction can resolve chronic viral infection and second, we reflect on how neutralization of the chemokine CXCL10 can abrogate virus-induced type 1 diabetes.

The limitation of IL-10-exposed dendritic cells in the treatment of experimental autoimmune myasthenia gravis and myasthenia gravis

Dendritic cells (DC) are highly specialized antigen presenting cells that play critical roles as instigators and regulators of immune responses including B cell function, antibody synthesis and isotype switch. In this study, we compared immunotherapeutic effect of IL-10-treated DC (IL-10-DC) via both intraperitoneal (i.p.) and subcutaneous (s.c.) delivery in rats with incipient experimental autoimmune myasthenia gravis (EAMG). Spleen DC were isolated from onset of EAMG on day 39 post-immunization, exposed in vitro to IL-10, and then injected into incipient EAMG at dose of 1 x 10(6) cells/rat on day 5 after immunization. Intraperitoneal administration of IL-10-DC suppressed clinical scores, anti-acetylcholine receptors (AChR) antibody secreting cells, antigen-specific IL-10/IFN-gamma production and T cell proliferation compared to control EAMG rats. Importantly, IL-10-DC, if given by s.c. route, failed to ameliorate clinical sign of EAMG. Simultaneously, T cell proliferation, anti-AChR antibody secreting cells and IL-10/IFN-gamma production had no alteration, as compared to control EAMG rats. Both in vitro and in vivo experiments showed that treatment of IL-10 inhibited the migration of DC toward MIP-3beta and lymph node, indicating that in vitro manipulation of DC with IL-10 alters the migration of DC that influences the therapeutic effect in the treatment of autoimmune diseases. In MG patients, neither the improvement of clinical symptom nor the alteration of immunological parameter was observed through s.c. delivery of IL-10-DC, suggesting the limitation of IL-10-DC in the treatment of MG patients.

Dendritic cell fusion vaccines for cancer immunotherapy

The use of tumour vaccines is being explored as a means of generating effective antitumour immune responses in patients with cancer. Dendritic cells (DCs) are the most potent antigen-presenting cells that are essential for initiating primary immune responses. As such, DCs are being studied as a platform for the design of cancer vaccines. DCs loaded with tumour antigens or whole tumour cell derivatives stimulate tumour-specific immunity. A promising vaccine strategy involves the fusion of DCs with whole tumour cells. DC/tumour fusions express a broad array of tumour antigens, including those yet to be identified, in the context of DC-mediated costimulation. Animal models have demonstrated that vaccination with fusion cells is protective against tumour challenge and results in the regression of established metastatic disease. In vitro human studies have demonstrated that DC/tumour fusions potently stimulate antitumour immunity and lysis of autologous tumour cells. Vaccination of cancer patients with DC/tumour fusions is being studied in Phase I/II clinical trials. Preliminary results demonstrate that generation of a vaccine is feasible and that vaccination is associated with minimal toxicity. Immunological and clinical responses have been found in a subset of patients.

TGF-beta in cancer and as a therapeutic target

Cancer develops through a series of genetic changes leading to malignant transformation. Numerous gene and pathways involved in stages of progression to frank malignancy have been elucidated. These genetic changes result in aberrations in fundamental cellular processes controlling proliferation, apoptosis, differentiation and genomic stability. Metastasis is the hallmark of malignancy. The process of metastasis is extremely complex and involves steps including dissemination of tumor cells from the primary tumor through the vascular and lymphatic system and growth selectively in distant tissues and organs. Transforming growth factor-beta which is a growth suppressive cytokine in many normal situations becomes an active and important participant in malignant disease including angiogenesis, extracellular matrix deposition, immuno-suppression and metastasis growth promotion. Transforming growth factor-beta and its receptors are targets for antibody therapeutics and small molecule kinase inhibitors.

The liver as an immunological organ

The liver is a unique anatomical and immunological site in which antigen-rich blood from the gastrointestinal tract is pressed through a network of sinusoids and scanned by antigen-presenting cells and lymphocytes. The liver's lymphocyte population is selectively enriched in natural killer and natural killer T cells which play critical roles in first line immune defense against invading pathogens, modulation of liver injury and recruitment of circulating lymphocytes. Circulating lymphocytes come in close contact to antigens displayed by endothelial cells, Kupffer cells and liver resident dendritic cells in the sinusoids. Circulating lymphocytes can also contact hepatocytes directly, because the sinusoidal endothelium is fenestrated and lacks a basement membrane. This unique anatomy of the liver may facilitate direct or indirect priming of lymphocytes, modulate the immune response to hepatotrophic pathogens and contribute to some of the unique immunological properties of this organ, particularly its capacity to induce antigen-specific tolerance.

Immunosuppressive and Trafficking Properties of Donor Splenic and Bone Marrow Dendritic Cells

BACKGROUND

Infusion of donor dendritic cells (DC) has been shown to prolong allograft survival in a number of models. However, many regimens that utilize donor DC do not consistently produced tolerance or long-term allograft survival. We hypothesized that one factor limiting the therapeutic effect of donor DC is their relative inability to traffic to recipient peripheral lymph nodes and inhibit the function of resident alloreactive T cells.

METHODS

Donor strain DC isolated from the spleens or bone marrow of Flt3L-treated mice were transferred intravenously into recipients at the time of skin grafting. Where indicated, recipients were treated with an anti-CD40L antibody and CTLA4-Ig.

RESULTS

Infusion of donor DC together with costimulatory blockade promoted donor-specific prolongation of skin allograft survival in mice. Perhaps due to their more immature phenotype, bone marrow DC trafficked more effectively to the spleen, bone marrow, and thymus and were associated with significantly longer allograft survival than were splenic DC. Neither population of DC trafficked well to peripheral lymph nodes. Consistent with our hypothesis, splenic but not lymph node T cells from DC-treated recipients displayed donor-specific hyporesponsiveness in vitro.

CONCLUSION

These data suggest that one factor contributing to rejection following treatment with donor DC plus costimulation blockade is the persistence of donor-reactive T cells within the recipient's secondary lymphoid structures. Strategies to improve DC trafficking to these structures may enhance their therapeutic effect.