Dendritic cell loss from nonlymphoid tissues after systemic administration of lipopolysaccharide, tumor necrosis factor, and interleukin 1

Nanospheres as the delivery vehicle: novel application of Toxoplasma gondii ribosomal protein S2 in PLGA and chitosan nanospheres against acute toxoplasmosis

Toxoplasma gondii (T. gondii) is a zoonotic disease that poses great harm to humans and animals. So far, no effective T. gondii vaccine has been developed to provide fully protection against such parasites. Recently, numerous researches have focused on the use of poly-lactic-co-glycolic acid (PLGA) and chitosan (CS) for the vaccines against T. gondii infections. In this study, we employed PLGA and CS as the vehicles for T. gondii ribosome protein (TgRPS2) delivery. TgRPS2-PLGA and TgRPS2-CS nanospheres were synthesized by double emulsion solvent evaporation and ionic gelation technique as the nano vaccines. Before immunization in animals, the release efficacy and toxicity of the synthesized nanospheres were evaluated in vitro. Then, ICR mice were immunized intramuscularly, and immune protections of the synthesized nanospheres were assessed. The results showed that TgRPS2-PLGA and TgRPS2-CS nanospheres could induce higher levels of IgG and cytokines, activate dendritic cells, and promote the expression of histocompatibility complexes. The splenic lymphocyte proliferation and the enhancement in the proportion of CD4+ and CD8+ T lymphocytes were also observed in immunized animals. In addition, two types of nanospheres could significantly inhabit the replications of T. gondii in cardiac muscles and spleen tissues. All these obtained results in this study demonstrated that the TgRPS2 protein delivered by PLGA or CS nanospheres provided satisfactory immunoprotective effects in resisting T. gondii, and such formulations illustrated potential as prospective preventive agents for toxoplasmosis.

Control of adaptive immunity by pattern recognition receptors

One of the most significant conceptual advances in immunology in recent history is the recognition that signals from the innate immune system are required for induction of adaptive immune responses. Two breakthroughs were critical in establishing this paradigm: the identification of dendritic cells (DCs) as the cellular link between innate and adaptive immunity and the discovery of pattern recognition receptors (PRRs) as a molecular link that controls innate immune activation as well as DC function. Here, we recount the key events leading to these discoveries and discuss our current understanding of how PRRs shape adaptive immune responses, both indirectly through control of DC function and directly through control of lymphocyte function. In this context, we provide a conceptual framework for how variation in the signals generated by PRR activation, in DCs or other cell types, can influence T cell differentiation and shape the ensuing adaptive immune response.

Immune System Acts on Orthodontic Tooth Movement: Cellular and Molecular Mechanisms

Orthodontic tooth movement (OTM) is a tissue remodeling process based on orthodontic force loading. Compressed periodontal tissues have a complicated aseptic inflammatory cascade, which are considered the initial factor of alveolar bone remodeling. Since skeletal and immune systems shared a wide variety of molecules, osteoimmunology has been generally accepted as an interdisciplinary field to investigate their interactions. Unsurprisingly, OTM is considered a good mirror of osteoimmunology since it involves immune reaction and bone remolding. In fact, besides bone remodeling, OTM involves cementum resorption, soft tissue remodeling, orthodontic pain, and relapse, all correlated with immune cells and/or immunologically active substance. The aim of this paper is to review the interaction of immune system with orthodontic tooth movement, which helps gain insights into mechanisms of OTM and search novel method to short treatment period and control complications.

Bromodomain Inhibitors Modulate FcγR-Mediated Mononuclear Phagocyte Activation and Chemotaxis

IgG antibodies form immune complexes (IC) that propagate inflammation and tissue damage in autoimmune diseases such as systemic lupus erythematosus. IgG IC engage Fcγ receptors (FcγR) on mononuclear phagocytes (MNP), leading to widespread changes in gene expression that mediate antibody effector function. Bromodomain and extra-terminal domain (BET) proteins are involved in governing gene transcription. We investigated the capacity of BET protein inhibitors (iBET) to alter IgG FcγR-mediated MNP activation. We found that iBET dampened IgG IC-induced pro-inflammatory gene expression and decreased activating FcγR expression on MNPs, reducing their ability to respond to IgG IC. Despite FcγR downregulation, iBET-treated macrophages demonstrated increased phagocytosis of protein antigen, IgG IC, and apoptotic cells. iBET also altered cell morphology, generating more amoeboid MNPs with reduced adhesion. iBET treatment impaired chemotaxis towards a CCL19 gradient in IC-stimulated dendritic cells (DC) in vitro, and inhibited IC-induced DC migration to draining lymph nodes in vivo, in a DC-intrinsic manner. Altogether, our data show that iBET modulates FcγR-mediated MNP activation and migration, revealing the therapeutic potential of BET protein inhibition in antibody-mediated diseases.

Immune cell behaviour and dynamics in the kidney - insights from in vivo imaging

The actions of immune cells within the kidney are of fundamental importance in kidney homeostasis and disease. In disease settings such as acute kidney injury, anti-neutrophil cytoplasmic antibody-associated vasculitis, lupus nephritis and renal transplant rejection, immune cells resident within the kidney and those recruited from the circulation propagate inflammatory responses with deleterious effects on the kidney. As in most forms of inflammation, intravital imaging - particularly two-photon microscopy - has been critical to our understanding of immune cell responses in the renal microvasculature and interstitium, enabling visualization of immune cell dynamics over time rather than statically. These studies have demonstrated differences in the recruitment and function of these cells from those in more conventional vascular beds, and provided a wealth of information on the actions of blood-borne immune cells such as neutrophils, monocytes and T cells, as well as kidney-resident mononuclear phagocytes, in a range of diseases affecting different kidney compartments. In particular, in vivo imaging has furthered our understanding of leukocyte function within the glomerulus in acute glomerulonephritis, and in the tubulointerstitium and interstitial microvasculature during acute kidney injury and following transplantation, revealing mechanisms of immune surveillance, antigen presentation and inflammation in the kidney.

Immune control of Mycobacterium tuberculosis is dependent on both soluble TNFRp55 and soluble TNFRp75

Tuberculosis presents a global health challenge, and tumour necrosis factor (TNF) signalling is required for host immunity against Mycobacterium tuberculosis (Mtb). TNF receptor shedding, however, compromises effective immunity by reducing bioactive TNF through the formation of inactive complexes. In this study, we first compared the effect of total soluble TNF receptors using a transgenic p55^ΔNS /p75^-/- murine strain on host protection during a low-dose aerosol Mtb H37Rv challenge. We report that the presence of membrane-bound TNFRp55 alone in the absence of TNFRp75 results in superior control of a primary Mtb infection where p55^ΔNS /p75^-/- hyperactive dendritic cells displayed an increased capacity to induce a hyperactive Mtb-specific CD4⁺ T-cell response. p55^ΔNS /p75^-/- dendritic cells expressed a higher frequency of MHCII and increased MFIs for both CD86 and MHCII, while CD4⁺ T cells had higher expression of CD44 and IFN-γ. Next, the relative contributions of soluble TNFRp55 and soluble TNFRp75 to host protection against either primary Mtb infection or during reactivation of latent tuberculosis were delineated by comparing the experimental outcomes of control C57BL/6 mice to transgenic p55^ΔNS /p75^-/- , p55^ΔNS and p75^-/- mouse strains. We found that soluble TNFRp55 is redundant for immune regulation during the chronic stages of a primary Mtb infection. However, TNFRp55 together with soluble TNFRp75 has a crucial role in immune regulation of reactivation of latent tuberculosis.

New peptide MY1340 revert the inhibition effect of VEGF on dendritic cells differentiation and maturation via blocking VEGF-NRP-1 axis and inhibit tumor growth in vivo

The development and clinical application of immunostimulatory therapy provides us a new and exciting strategy in cancer treatment of which the agents act on crucial receptors. Given the fact that Neuropilin-1(NRP-1) is essential for vascular endothelial growth factor (VEGF) to inhibit LPS-dependent maturation of dendritic cells (DCs), it may present a potentially meaningful target in cancer immunotherapy. To explore this hypothesis, we synthesized a novel polypeptide called MY1340 consist of 32 amino acids with the aim of targeting VEGF-NRP-1 axis. Pull-down assay coupled with liquid chromatography-tandem mass spectrometry analysis (LC-MS/MS) was firstly conducted to identify NRP-1 as a potential MY1340 interacting protein, and the interaction between them was further confirmed by western blot. The competitive enzyme-linked immunosorbent assay (ELISA) results revealed that MY1340 was able to inhibit the binding between NRP-1 and VEGF with IC₅₀ 7.42 ng/ml, better than that of Tuftsin, although a natural ligand reportedly specific for the NRP-1 receptor. The presence of VEGF significantly reduced the expression of human leukocyte antigen-DR (HLA-DR), CD86 and CD11C on DCs, and this effect was reverted by MY1340-augment p65 NF-κB and ERK1/2 phosphorylation. We also present evidence that MY1340 is remarkably efficacious in the treatment of mice bearing subcutaneous liver cancer and induced DC maturation in the tumor environment in vivo. Taken together, these results indicate that MY1340 may represent a potential efficient immune therapeutic compound within disease that are rich in VEGF.

Lycium barbarum Polysaccharide Promotes Maturation of Dendritic Cell via Notch Signaling and Strengthens Dendritic Cell Mediated T Lymphocyte Cytotoxicity on Colon Cancer Cell CT26-WT

Lycium barbarum polysaccharide (LBP) is the major function component of Lycium barbarum L. and has been previously reported to induce the phenotypic and functional maturation of dendritic cells (DCs) as well as activating T lymphocytes. In the current study, the immunologic cytotoxicity promoting effect of LBP was assessed and the underlying mechanism was explored. The impact of LBP on the phenotype, maturation, and immunogenicity of DCs was assessed. The activity of Notch pathway which is involved in the regulation of LBP on DCs was detected. Afterwards, the influence of LBP on cytotoxicity of DC-mediated cytotoxicity T lymphocytes (CTLs) to CT26-WT colon cancer cells was further assessed. Administration of LBP induced the phenotypic and functional maturation of DCs. After being subjected to LBP, the expression of Notch and Jagged and Notch targets Hes1 and Hes5 was all upregulated. The cytotoxicity of DC-mediated CTLs was strengthened by administration of LBP. Additionally, cytotoxicity of DC-mediated CTLs on CT26-WT colon cancer cells also increased with effector-target ratio. In conclusion, LBP could induce the phenotypic and functional maturation of DCs via Notch signaling and promote the cytotoxicity of DC-mediated CTLs, which could be employed as a promising adjuvant for cancer immunotherapy.

Dendritic Cells in the Immune System—History, Lineages, Tissues, Tolerance, and Immunity

The aim of this review is to provide a coherent framework for understanding dendritic cells (DCs). It has seven sections. The introduction provides an overview of the immune system and essential concepts, particularly for the nonspecialist reader. Next, the “History” section outlines the early evolution of ideas about DCs and highlights some sources of confusion that still exist today. The “Lineages” section then focuses on five different populations of DCs: two subsets of “classical” DCs, plasmacytoid DCs, monocyte-derived DCs, and Langerhans cells. It highlights some cellular and molecular specializations of each, and also notes other DC subsets that have been proposed. The following “Tissues” section discusses the distribution and behavior of different DC subsets within nonlymphoid and secondary lymphoid tissues that are connected by DC migration pathways between them. In the “Tolerance” section, the role of DCs in central and peripheral tolerance is considered, including their ability to drive the differentiation of different populations of regulatory T cells. In contrast, the “Immunity” section considers the roles of DCs in sensing of infection and tissue damage, the initiation of primary responses, the T-cell effector phase, and the induction of immunological memory. The concluding section provides some speculative ideas about the evolution of DCs. It also revisits earlier concepts of generation of diversity and clonal selection in terms of DCs driving the evolution of T-cell responses. Throughout, this review highlights certain areas of uncertainty and suggests some avenues for future investigation.

FcγRIIB and autoimmunity

Autoimmune diseases are characterized by adaptive immune responses against self-antigens, including humoral responses resulting in the production of autoantibodies. Autoantibodies generate inflammation by activating complement and engaging Fcγ receptors (FcγRs). The inhibitory receptor FcγRIIB plays a central role in regulating the generation of autoantibodies and their effector functions, which include activation of innate immune cells and the cellular arm of the adaptive immune system, via effects on antigen presentation to CD4 T cells. Polymorphisms in FcγRIIB have been associated with susceptibility to autoimmunity but protection against infections in humans and mice. In the last few years, new mechanisms by which FcγRIIB controls the adaptive immune response have been described. Notably, FcγRIIB has been shown to regulate germinal center B cells and dendritic cell migration, with potential impact on the development of autoimmune diseases. Recent work has also highlighted the implication of FcγRIIB on the regulation of the innate immune system, via inhibition of Toll-like receptor- and complement receptor-mediated activation. This review will provide an update on the role of FcγRIIB in adaptive immune responses in autoimmunity, and then focus on their emerging function in innate immunity.

Migration of dendritic cells to the lymph nodes and its enhancement to drive anti-tumor responses

Better prognoses associated with increased T cell infiltration of tumors, as seen with chimeric antigen receptor (CAR) T cell therapies and immune checkpoint inhibitors, portray the importance and potential of the immune system in controlling tumors. This has rejuvenated the field of cancer immunotherapy leading to an increasing number of immunotherapies developed for cancer patients. Dendritic Cells (DCs) vaccines represent an appealing option for cancer immunotherapy since DCs have the ability to circumvent tolerance to tumors by its adjuvant properties and to induce memory T cells that can become persistent after initial tumor clearance to engage potential metastatic tumors. In the past, DC-based cancer vaccines have elicited only poor clinical response in cancer patients, which can be attributed to complex and a multitude of issues associated with generation, implementing, delivery of DC vaccine and their potential interaction with effector cells. The current review mainly focuses on migration/trafficking of DCs, as one of the key issues that affect the success of DC-based cancer vaccines, and discusses strategies to enhance it for cancer immunotherapy. Additionally, impact of maturation, route of DC delivery and negative effects of tumor microenvironment (TME) on DC homing to LN are reviewed. Moreover, strategies to increase the expression of genes involved in Lymph node homing, preconditioning of the vaccination site, enhancing lymph node ability to attract and receive DCs, while limiting negative impact of TME on DC migration are discussed.

Unraveling the immunopathogenesis of glomerular disease

Immune-mediated damage to glomerular structures is largely responsible for the pathology associated with the majority of glomerular diseases. Therefore, a detailed understanding of the basic immune mechanisms responsible for glomerular damage is needed to inform the design of novel intervention strategies. Glomerular injury of immune origin is complex and involves both inflammatory and non-inflammatory processes driven by elements of the innate and adaptive immune system. This review summarizes the basic immune mechanisms that cause glomerular injury leading to the nephritic and nephrotic syndromes. A major focus of the review is to highlight the mechanisms by which antibodies cause glomerular injury through their interactions with glomerular cells, complement proteins, phagocytes bearing complement and Fcγ receptors, and dendritic cells expressing the neonatal receptor for IgG, FcRn.

Effects of inactivated porcine epidemic diarrhea virus on porcine monocyte-derived dendritic cells and intestinal dendritic cells

Porcine epidemic diarrhea (PED) is a serious infection in neonatal piglets. As the causative agent of PED, porcine epidemic diarrhea virus (PEDV) results in acute diarrhea and dehydration with high mortality rates in swine. Dendritic cells (DCs) are highly effective antigen-presenting cells to uptake and present viral antigens to T cells, which then initiate a distinct immune response. In this study, our results show that the expression of Mo-DCs surface markers such as SWC3a(+)CD1a(+), SWC3a(+)CD80/86(+) and SWC3a(+)SLA-II-DR(+) is increased after incubation with UV-PEDV for 24h. Mo-DCs incubated with UV-PEDV produce higher levels of IL-12 and INF-γ compared to mock-infected Mo-DCs. Interactions between Mo-DCs and UV-PEDV significantly stimulate T-cell proliferation in vitro. Consistent with these results, there is an enhancement in the ability of porcine intestinal DCs to activate T-cell proliferation in vivo. We conclude that UV-PEDV may be a useful and safe vaccine to trigger adaptive immunity.

Molecular Mechanisms of Nickel Allergy

Allergic contact hypersensitivity to metals is a delayed-type allergy. Although various metals are known to produce an allergic reaction, nickel is the most frequent cause of metal allergy. Researchers have attempted to elucidate the mechanisms of metal allergy using animal models and human patients. Here, the immunological and molecular mechanisms of metal allergy are described based on the findings of previous studies, including those that were recently published. In addition, the adsorption and excretion of various metals, in particular nickel, is discussed to further understand the pathogenesis of metal allergy.

Collagen I-induced dendritic cells activation is regulated by TNF-alpha production through down-regulation of IRF4

Previously we have shown that collagen I enhances the maturation and function of dendritic cells (DCs). Inflammatory mediators such as tumour necrosis factor (TNF)- alpha, interleukin (IL)-1 beta and lipopolysaccharide (LPS) are also known to activate DCs. Here we investigated the involvement of TNF-alpha on the collagen I-induced DCs activation. TNF-a neutralization inhibited collagen I-induced IL-12 secretions by DCs. Additionally, we observed suppression of collagen I-induced costimulatory molecules expression along with down-regulation of genes involved in DCs activation pathway. Furthermore, TNF- alpha inhibition upon collagen Istimulation up-regulated the expression of interferon regulatory transcription factor IRF4, when compared to collagen I only treated cells. Collectively, our data demonstrate that collagen I induce TNF- alpha production, which is crucial for the activation and function of DCs, through down-regulation of IRF4, and implicates the importance in development of anti- TNF-alpha therapeutics for several inflammatory diseases.

The Effect of Small Oligomeric Protein Aggregates on the Immunogenicity of Intravenous and Subcutaneous Administered Antibodies

The role of aggregates in the immunogenicity of biologics is a major concern. A recent US FDA guidance on the issue suggests that a gap in knowledge exists regarding the type and size of aggregates involved in the immunogenicity of biologics. Furthermore, the guidance suggests that current techniques cannot capture the crucial stages of protein aggregation. Using a protein unfolding model developed earlier, we generated and classified aggregates of two therapeutic antibodies based on size and conformation. The immunogenic potential of these aggregates were then tested in a murine model. Our findings show that small native-like oligomeric aggregates (<100 nm) are more immunogenic toward the native protein than monomer and large non-native aggregates in the micron-size range, irrespective of route of administration [intravenous (i.v.) vs. subcutaneous (s.c.)]. Those smaller oligomeric aggregates represented 5%-20% of the total protein concentration in the test formulations. Furthermore, in vitro data suggest that TNF-α production by bone marrow-derived dendritic cells could serve as a predictive marker for increased immunogenic risk of aggregates after s.c. administration. The use of orthogonal techniques such as fluorescence anisotropy and quasielastic light scattering may be useful to detect these oligomeric aggregates.

Dendritic cell interactions with Histoplasma and Paracoccidioides

Fungi are among the most common microbes encountered by humans. More than 100, 000 fungal species have been described in the environment to date, however only a few species cause disease in humans. Fungal infections are of particular importance to immunocompromised hosts in whom disease is often more severe, especially in those with impaired cell-mediated immunity such as individuals with HIV infection, hematologic malignancies, or those receiving TNF-α inhibitors. Nevertheless, environmental disturbances through natural processes or as a consequence of deforestation or construction can expose immunologically competent people to a large number of fungal spores resulting in asymptomatic acquisition to life-threatening disease. In recent decades, the significance of the innate immune system and more importantly the role of dendritic cells (DC) have been found to play a fundamental role in the resolution of fungal infections, such as in dimorphic fungi like Histoplasma and Paracoccidioides. In this review article the general role of DCs will be illustrated as the bridge between the innate and adaptive immune systems, as well as their specific interactions with these 2 dimorphic fungi.

Selective Dependence of Kidney Dendritic Cells on CX3CR1--Implications for Glomerulonephritis Therapy

As central regulators of the adaptive immune response, dendritic cells (DCs) are found in virtually all lymphatic and non-lymphatic organs. A compact network of DCs also spans the kidneys. DCs play a central role in maintenance of organ homeostasis as well as in induction of immune responses against invading pathogens. They can mediate protective or destructive functions in a context-dependent manner.We recently identified CX(3)CR1 as a kidney-specific "homing receptor" for DCs. There was a strong reduction of DCs in the kidneys of CX(3)CR1-deficient mice compared to controls. This reduction was not observed in other organs except the small intestine. As a possible underlying reason we found a strong expression of the CX(3)CR1 ligand fractalkine in the kidneys. Due to this CX(3)CR1-dependent reduction of DCs, especially in the renal cortex, a glomerulonephritis (GN) model was ameliorated in CX(3)CR1-deficient mice. In contrast, the immune defense against the most common renal infection, bacterial pyelonephritis (PN), was not significantly influenced by CX(3)CR1-deficiency. This was explained by the much smaller CX(3)CR1-dependency of medullary DCs, which recruit effector cells into the kidney during PN. Additionally, once neutrophils had been recruited by mechanisms distinct from CX(3)CR1, they carried out some of the functions of DCs.Taken together, we suggest CX(3)CR1 as a therapeutic target for GN treatment, as the absence of CX(3)CR1 selectively influences DCs in the kidney without rendering mice more susceptible towards bacterial kidney infections.

Immune complexes stimulate CCR7-dependent dendritic cell migration to lymph nodes

Antibodies are critical for defense against a variety of microbes, but they may also be pathogenic in some autoimmune diseases. Many effector functions of antibodies are mediated by Fcγ receptors (FcγRs), which are found on most immune cells, including dendritic cells (DCs)-important antigen-presenting cells that play a central role in inducing antigen-specific tolerance or immunity. Following antigen acquisition in peripheral tissues, DCs migrate to draining lymph nodes via the lymphatics to present antigen to T cells. Here we demonstrate that FcγR engagement by IgG immune complexes (ICs) stimulates DC migration from peripheral tissues to the paracortex of draining lymph nodes. In vitro, IC-stimulated mouse and human DCs showed greater directional migration in a chemokine (C-C) ligand 19 (CCL19) gradient and increased chemokine (C-C) receptor 7 (CCR7) expression. Using intravital two-photon microscopy, we observed that local administration of IC resulted in dermal DC mobilization. We confirmed that dermal DC migration to lymph nodes depended on CCR7 and increased in the absence of the inhibitory receptor FcγRIIB. These observations have relevance to autoimmunity because autoantibody-containing serum from humans with systemic lupus erythematosus (SLE) and from a mouse model of SLE also increased dermal DC migration in vivo, suggesting that this process may occur in lupus, potentially driving the inappropriate localization of autoantigen-bearing DCs.

Dendritic cells and macrophages in the kidney: a spectrum of good and evil

Renal dendritic cells (DCs) and macrophages represent a constitutive, extensive and contiguous network of innate immune cells that provide sentinel and immune-intelligence activity; they induce and regulate inflammatory responses to freely filtered antigenic material and protect the kidney from infection. Tissue-resident or infiltrating DCs and macrophages are key factors in the initiation and propagation of renal disease, as well as essential contributors to subsequent tissue regeneration, regardless of the aetiological and pathogenetic mechanisms. The identification, and functional and phenotypic distinction of these cell types is complex and incompletely understood, and the same is true of their interplay and relationships with effector and regulatory cells of the adaptive immune system. In this Review, we discuss the common and distinct characteristics of DCs and macrophages, as well as key advances that have identified the renal-specific functions of these important phagocytic, antigen-presenting cells, and their roles in potentiating or mitigating intrinsic kidney disease. We also identify remaining issues that are of priority for further investigation, and highlight the prospects for translational and therapeutic application of the knowledge acquired.

Boosting the MHC Class II-Restricted Tumor Antigen Presentation to CD4+ T Helper Cells: A Critical Issue for Triggering Protective Immunity and Re-Orienting the Tumor Microenvironment Toward an Anti-Tumor State

Although the existence of an immune response against tumor cells is well documented, the fact that tumors take off in cancer patients indicates that neoplastic cells can circumvent this response. Over the years many investigators have described strategies to rescue the anti-tumor immune response with the aim of creating specific and long-lasting protection against the disease. When exported to human clinical settings, these strategies have revealed in most cases a very limited, if any, positive outcome. We believe that the failure is mostly due to the inadequate triggering of the CD4+ T helper (TH) cell arm of the adaptive immunity, as TH cells are necessary to trigger all the immune effector mechanisms required to eliminate tumor cells. In this review, we focus on novel strategies that by stimulating MHC class II-restricted activation of TH cells generate a specific and persistent adaptive immunity against the tumor. This point is of critical importance for both preventive and therapeutic anti-tumor vaccination protocols, because adaptive immunity with its capacity to produce specific, long-lasting protection and memory responses is indeed the final goal of vaccination. We will discuss data from our as well as other laboratories which strongly suggest that triggering a specific and persistent anti-tumor CD4+ TH cell response stably modify not only the tumor microenvironment but also tumor-dependent extratumor microenvironments by eliminating and/or reducing the blood-derived tumor infiltrating cells that may have a pro-tumor growth function such as regulatory CD4+/CD25+ T cells and myeloid-derived-suppressor cells. Within this frame, therefore, we believe that the establishment of a pro-tumor environment is not the cause but simply the consequence of the tumor strategy to primarily counteract components of the adaptive cellular immunity, particularly TH lymphocytes.

Novel immunomodulators from hard ticks selectively reprogramme human dendritic cell responses

Hard ticks subvert the immune responses of their vertebrate hosts in order to feed for much longer periods than other blood-feeding ectoparasites; this may be one reason why they transmit perhaps the greatest diversity of pathogens of any arthropod vector. Tick-induced immunomodulation is mediated by salivary components, some of which neutralise elements of innate immunity or inhibit the development of adaptive immunity. As dendritic cells (DC) trigger and help to regulate adaptive immunity, they are an ideal target for immunomodulation. However, previously described immunoactive components of tick saliva are either highly promiscuous in their cellular and molecular targets or have limited effects on DC. Here we address the question of whether the largest and globally most important group of ticks (the ixodid metastriates) produce salivary molecules that specifically modulate DC activity. We used chromatography to isolate a salivary gland protein (Japanin) from Rhipicephalus appendiculatus ticks. Japanin was cloned, and recombinant protein was produced in a baculoviral expression system. We found that Japanin specifically reprogrammes DC responses to a wide variety of stimuli in vitro, radically altering their expression of co-stimulatory and co-inhibitory transmembrane molecules (measured by flow cytometry) and their secretion of pro-inflammatory, anti-inflammatory and T cell polarising cytokines (assessed by Luminex multiplex assays); it also inhibits the differentiation of DC from monocytes. Sequence alignments and enzymatic deglycosylation revealed Japanin to be a 17.7 kDa, N-glycosylated lipocalin. Using molecular cloning and database searches, we have identified a group of homologous proteins in R. appendiculatus and related species, three of which we have expressed and shown to possess DC-modulatory activity. All data were obtained using DC generated from at least four human blood donors, with rigorous statistical analysis. Our results suggest a previously unknown mechanism for parasite-induced subversion of adaptive immunity, one which may also facilitate pathogen transmission.

Dendritic cells (DC) are specialised cells of the vertebrate immune system. DC can sense different types of infectious agents and parasites, and both trigger and help regulate the specific types of immunity needed to eliminate them. We have discovered that the largest and globally most important group of hard ticks produce a unique family of proteins in their saliva that selectively targets DC, radically altering functions that would otherwise induce robust immune responses; these proteins also prevent DC developing from precursor cells. The production of these salivary molecules may help to explain two highly unusual features of these hard ticks compared with other blood-feeding parasites: their ability to feed continuously on their vertebrate hosts for considerable lengths of time (7 days or more) without eliciting potentially damaging immune responses, and their capacity to transmit possibly the greatest variety of pathogens of any type of invertebrate.

The role of the e3 ligase cbl-B in murine dendritic cells

Dendritic cells (DCs) are potent antigen-presenting cells with a promising potential in cancer immunotherapy. Cbl proteins are E3 ubiquitin ligases and have been implicated in regulating the functional activity of various immune cells. As an example, c-Cbl negatively affects DC activation. We here describe that another member of the Cbl-protein family (i.e. Cbl-b) is highly expressed in murine bone-marrow-derived DCs (BMDCs). Differentiation of cblb−/− bone marrow mononuclear cells into classical BMDCs is unaltered, except enhanced induction of DEC-205 (CD205) expression. When tested in mixed-lymphocyte reaction (MLR), cblb−/− BMDCs exhibit increased allo-stimulatory capacity in vitro. BMDCs were next in vitro stimulated by various toll like receptor (TLR)-agonists (LPS, Poly(I:C), CpG) and exposed to FITC-labeled dextran. Upon TLR-stimulation, cblb−/− BMDCs produce higher levels of proinflammatory cytokines (IL-1α, IL-6 and TNF-α) and exhibit a slightly higher level of FITC-dextran uptake. To further characterize the functional significance of cblb−/− BMDCs we tested them in antigen-specific T cell responses against ovalbumin (OVA) protein and peptides, activating either CD8⁺ OT-I or CD4⁺ OT-II transgenic T cells. However, cblb−/− BMDCs are equally effective in inducing antigen-specific T cell responses when compared to wildtype BMDCs both in vitro and in vivo. The migratory capacity into lymph nodes during inflammation was similarly not affected by the absence of Cbl-b. In line with these observations, cblb−/− peptide-pulsed BMDCs are equally effective vaccines against OVA-expressing B16 tumors in vivo when compared to wildtype BMDCs. We conclude that in contrast to c-Cbl, Cbl-b plays only a limited role in the induction of Ag-specific T cell responses by murine BMDCs in vitro and in vivo.

Schedule-dependent therapeutic efficacy of L19mTNF-α and melphalan combined with gemcitabine

L19-tumor necrosis factor alpha (L19mTNF-α; L), a fusion protein consisting of mouse TNFα and the human antibody fragment L19 directed to the extra domain-B (ED-B) of fibronectin, is able to selectively target tumor vasculature and to exert a long-lasting therapeutic activity in combination with melphalan (M) in syngeneic mouse tumor models. We have studied the antitumor activity of single L19mTNF-α treatment in combination with melphalan and gemcitabine (G) using different administration protocols in two histologically different murine tumor models: WEHI-164 fibrosarcoma and K7M2 osteosarcoma. All responding mice showed significant reduction in myeloid-derived suppressor cells (MDSCs) and an increase in CD4⁺ and CD8⁺ T cells in the tumor infiltrates, as well as significant reduction in regulatory T cells (Treg) at the level of draining lymph nodes. What is important is that all cured mice rejected tumor challenge up to 1 year after therapy. Targeted delivery of L19mTNF-α synergistically increases the antitumor activity of melphalan and gemcitabine, but optimal administration schedules are required. This study provides information for designing clinical studies using L19mTNF-α in combination with chemotherapeutic drugs.

Targeted delivery of L19mTNF-α synergistically increases the antitumor activity of melphalan and gemcitabine, but optimal administration schedule requires a pretreatment with L19mTNF-α otherwise an antagonistic effect could occur. This study provides information for designing clinical studies using L19mTNF-α in combination with chemotherapeutic drugs.

Rapid interferon-gamma release from natural killer cells induced by a streptococcal commensal

Interferon-gamma (IFN-γ) is a critical cytokine for the initiation of immune responses against a variety of infectious agents and malignancies. We found that a range of Gram-positive and Gram-negative bacteria stimulated the rapid release (<24 h) of IFN-γ from murine leukocytes. Using fluorescence activated cell sorting and cd1d(-/-) and rag1(-/-) mice, we determined that dendritic cells (DCs) and natural killer (NK) cells were primarily responsible for IFN-γ release by Streptococcus salivarius, a Gram-positive commensal, previously noted to possess potent interleukin-12 (IL-12)-inducing potential. IFN-γ release from NK cells required DC:NK membrane contact and IL-12/IL-18 expression, but was independent of lymphocyte function-associated antigen-1-mediated interactions. IFN-γ release in response to bacteria was maintained in mice deficient for Toll-like receptor (TLR)-2 and TLR-4, suggesting that bacteria activate antigen-presenting cells via multiple, redundant pathways. Together, our results suggest that Gram-positive bacteria may be useful in driving NK cell activation and T helper 1 polarization and have the potential for development as effective adjuvants.

Potentiating functional antigen-specific CD8⁺ T cell immunity by a novel PD1 isoform-based fusion DNA vaccine

Understanding and identifying new ways of mounting an effective CD8⁺ T cell immune response is important for eliminating infectious pathogens. Although upregulated programmed death-1 (PD1) in chronic infections (such as HIV-1 and tuberculosis) impedes T cell responses, blocking this PD1/PD-L pathway could functionally rescue the "exhausted" T cells. However, there exists a number of PD1 spliced variants with unknown biological function. Here, we identified a new isoform of human PD1 (Δ42PD1) that contains a 42-nucleotide in-frame deletion located at exon 2 domain found expressed in peripheral blood mononuclear cells (PBMCs). Δ42PD1 appears to function distinctly from PD1, as it does not engage PD-L1/PD-L2 but its recombinant form could induce proinflammatory cytokines. We utilized Δ42PD1 as an intramolecular adjuvant to develop a fusion DNA vaccine with HIV-1 Gag p24 antigen to immunize mice, which elicited a significantly enhanced level of anti-p24 IgG1/IgG2a antibody titers, and important p24-specific and tetramer⁺CD8⁺ T cells responses that lasted for ≥7.5 months. Furthermore, p24-specific CD8⁺ T cells remain functionally improved in proliferative and cytolytic capacities. Importantly, the enhanced antigen-specific immunity protected mice against pathogenic viral challenge and tumor growth. Thus, this newly identified PD1 variant (Δ42PD1) amplifies the generation of antigen-specific CD8⁺ T cell immunity when used in a DNA vaccine.

Rho-family GTPase Cdc42 controls migration of Langerhans cells in vivo

Epidermal Langerhans cells (LCs) of the skin represent the prototype migratory dendritic cell (DC) subtype. In the skin, they take up Ag, migrate to the draining lymph nodes, and contribute to Ag transport and immunity. Different depletion models for LCs have revealed contrasting roles and contributions of this cell type. To target the migratory properties of DCs, we generated mice lacking the Rho-family GTPase Cdc42 specifically in DCs. In these animals, the initial seeding of the epidermis with LCs is functional, resulting in slightly reduced Langerhans cell numbers. However, Cdc42-deficient LCs fail to leave the skin in steady state as well as upon stimulation, as they do not enter the skin-draining afferent lymph vessels. Similarly, also other Cdc42-deficient migratory DC subsets fail to home properly to the corresponding draining lymph nodes. We used this novel mouse model, in which LCs are locked out, to demonstrate that these cells contribute substantially to priming of Ag-specific CD4 and CD8 T cell responses upon epicutaneous immunization, but could not detect a role in the induction of contact hypersensitivity to various doses of hapten.

Atopic dermatitis results in intrinsic barrier and immune abnormalities: implications for contact dermatitis

Atopic dermatitis (AD), as well as irritant contact dermatitis (ICD) and allergic contact dermatitis (ACD), are common skin diseases. These diseases are characterized by skin inflammation mediated by activated innate immunity or acquired immune mechanisms. Although AD, ICD, and ACD can be encountered in pure forms by allergists and dermatologists, patients with AD often present with increased frequency of ICD and ACD. Although a disturbed barrier alone could potentiate immune reactivity in patients with AD through increased antigen penetration, additional immune mechanisms might explain the increased susceptibility of atopic patients to ICD and ACD. This review discusses cellular pathways associated with increased skin inflammation in all 3 conditions and presents mechanisms that might contribute to the increased rate of ICD and ACD in patients with AD.

Isolation of functional dendritic cells from murine kidneys for immunological characterization

AIM

The kidney is a complex organ, requiring the contributions of multiple cell types to perform its various functions. Within this system the dendritic cell has been demonstrated to play a key role in maintaining the immunological balance of the kidney. In this methods paper we aim to identify the best method for isolating murine renal dendritic cells.

METHODS

The efficiency of isolating dendritic cells from enzymatically digested renal parenchyma by density centrifugation, MACS and FACS was compared.

RESULTS

Density centrifugation enriched dendritic cells by only approximately two fold. However, MACS and FACS resulted in a much higher purity (80% versus 95% respectively).

CONCLUSIONS

Although FACS gave the highest purity, MACS is the optimal method for isolating dendritic cells given cost and time factors. Isolation of a homogeneous population of renal dendritic cells will enable the molecular and functional dissection of these cells in both homeostasis and disease models.

Strategies to alleviate original antigenic sin responses to influenza viruses

Original antigenic sin is a phenomenon wherein sequential exposure to closely related influenza virus variants reduces antibody (Ab) response to novel antigenic determinants in the second strain and, consequently, impairs the development of immune memory. This could pose a risk to the development of immune memory in persons previously infected with or vaccinated against influenza. Here, we explored strategies to overcome original antigenic sin responses in mice sequentially exposed to two closely related hemagglutinin 1 neuraminidase 1 (H1N1) influenza strains A/PR/8/34 and A/FM/1/47. We found that dendritic cell-activating adjuvants [Bordetella pertussis toxin (PT) or CpG ODN or a squalene-based oil-in-water nanoemulsion (NE)], upon administration during the second viral exposure, completely protected mice from a lethal challenge and enhanced neutralizing-Ab titers against the second virus. Interestingly, PT and NE adjuvants when administered during the first immunization even prevented original antigenic sin in subsequent immunization without any adjuvants. As an alternative to using adjuvants, we also found that repeated immunization with the second viral strain relieved the effects of original antigenic sin. Taken together, our studies provide at least three ways of overcoming original antigenic sin.

Collagen I enhances functional activities of human monocyte-derived dendritic cells via discoidin domain receptor 2

We evaluated the involvement of collagen and their discoidin domain receptors (DDRs), DDR1 and DDR2, on the activation of human monocyte-derived dendritic cells (hDCs). DDR2 was markedly expressed on mature hDCs in comparison to immature ones. Collagen I enhanced the release of IL-12p40, TNF-α and IFN-γ by hDCs. Additionally, hDCs exhibited enhanced expression of costimulatory molecules, and potent functional activities which, in turn, has therapeutic value. Interestingly, DDR2 depletion showed decrease in capacity of hDCs to stimulate T cells proliferation, whereas DDR1 silencing had no significant affect. These data demonstrate that DDR2 enhances hDCs activation and contributes to their functional activities. In addition, application of collagen I treated dendritic cells (DCs) vaccine reduced tumor burden giving longer survival in melanoma mice. Our study suggests that collagen I may enhance functional activities of DCs in immune response.

Maturation of murine bone marrow-derived dendritic cells induced by Radix Glycyrrhizae polysaccharide

Radix Glycyrrhizae polysaccharide (GP), the most important component of Radix Glycyrrhizae, has been reported to have many immunopharmacological activities. However, the mechanism by which GP affects dendritic cells (DCs) has not been elucidated. In this study, we investigated the effect of GP on murine bone marrow-derived DCs and the potential pathway through which GP exerts this effect. Mononuclear cells (MNCs) were isolated from murine bone marrow and induced to become DCs by culturing with GM-CSF and IL-4. Six days later, DCs were divided into three groups: control group, GP group and LPS group. After 48 h of treatment, phenotypic figures and antigen uptake ability were determined by FACS analysis. The proliferation of DC-stimulated allogenic CD3+ T cells was detected by WST-1. IL-12 p70 and IFN-γ, which are secreted by DCs and CD3+ T cells respectively, were quantified by ELISA. Additionally, IL-12 p40 mRNA expression was determined by real-time PCR. Alterations in TLR4-related signaling pathways were examined by performing an antibody neutralization experiment. Treatment of DCs with GP resulted in the enhanced expression of the cell surface molecules CD80, CD86 and MHC I-A/I-E. GP also increased the production of IL-12 p70 by DCs in a time-dependent manner. The endocytosis of FITC-dextran by DCs was suppressed by GP administration. Furthermore, GP-treated DCs enhanced both the proliferation and IFN-γ secretion of allogenic CD3+ T cells. Finally, the effects of GP on DCs were partially reduced by using inhibitors of TLR4, NF-κB, p38 MAPK or JNK. In conclusion, GP can induce the maturation of DCs, and does so, in part, by regulating a TLR4-related signaling pathway.

The loss of renal dendritic cells and activation of host adaptive immunity are long-term effects of ischemia/reperfusion injury following syngeneic kidney transplantation

Ischemia/reperfusion injury associated with kidney transplantation induces profound acute injury, influences early graft function and affects long-term graft outcomes. To determine whether renal dendritic cells play any role during initial innate ischemia/reperfusion injury and the subsequent development of adaptive immune responses, we studied the behavior and function of renal graft and host infiltrating dendritic cells during early and late phases of renal ischemia/reperfusion injury. Wild type to GFP-transgenic rat kidney transplantation was performed with and without 24 hours cold storage. Ischemia/reperfusion injury in cold stored grafts resulted in histopathological changes of interstitial fibrosis and tubular atrophy by 10 weeks accompanied by upregulation of mRNAs of mediators of interstitial fibrosis and inflammation. In normal rat kidneys we identified two populations of renal dendritic cells, predominant CD103⁻CD11b/c⁺ and minor CD103⁺CD11b/c⁺ cells. After transplantation without cold storage, grafts maintained CD103⁻ but not CD103⁺ GFP-negative renal dendritic cells for 10 weeks. In contrast, both cell subsets disappeared from cold stored grafts, which associated with a significant GFP-expressing host CD11b/c⁺ cell infiltration that included CD103⁺ dendritic cells with a TNF-α producing phenotype. These changes in graft/host dendritic cell populations were associated with progressive infiltration of host CD4⁺ T cells with effector/effector-memory phenotypes and IFN-γ secretion. Thus, renal graft ischemia/reperfusion injury causes graft dendritic cell loss and was associated with progressive host dendritic cell and T cell recruitment. Renal resident dendritic cells might function as a protective regulatory network.

The renal mononuclear phagocytic system

The renal mononuclear phagocytic system, conventionally composed of macrophages (Mø) and dendritic cells (DCs), plays a central role in health and disease of the kidney. Overlapping definitions of renal DCs and Mø, stemming from historically separate research tracks and the lack of experimental tools to specifically study the roles of these cells in vivo, have generated confusion and controversy, however, regarding their immunologic function in the kidney. This brief review provides an appraisal of the current state of knowledge of the renal mononuclear phagocytic system interpreted from the perspective of immunologic function. Physical characteristics, ontogeny, and known functions of the main subsets of renal mononuclear phagocytes as they relate to homeostasis, surveillance against injury and infection, and immune-mediated inflammatory injury and repair within the kidney are described. Gaps and inconsistencies in current knowledge are used to create a roadmap of key questions to be answered in future research.

The Burkholderia pseudomallei Δasd mutant exhibits attenuated intracellular infectivity and imparts protection against acute inhalation melioidosis in mice

Burkholderia pseudomallei, the cause of serious and life-threatening diseases in humans, is of national biodefense concern because of its potential use as a bioterrorism agent. This microbe is listed as a select agent by the CDC; therefore, development of vaccines is of significant importance. Here, we further investigated the growth characteristics of a recently created B. pseudomallei 1026b Δasd mutant in vitro, in a cell model, and in an animal model of infection. The mutant was typified by an inability to grow in the absence of exogenous diaminopimelate (DAP); upon single-copy complementation with a wild-type copy of the asd gene, growth was restored to wild-type levels. Further characterization of the B. pseudomallei Δasd mutant revealed a marked decrease in RAW264.7 murine macrophage cytotoxicity compared to the wild type and the complemented Δasd mutant. RAW264.7 cells infected by the Δasd mutant did not exhibit signs of cytopathology or multinucleated giant cell (MNGC) formation, which were observed in wild-type B. pseudomallei cell infections. The Δasd mutant was found to be avirulent in BALB/c mice, and mice vaccinated with the mutant were protected against acute inhalation melioidosis. Thus, the B. pseudomallei Δasd mutant may be a promising live attenuated vaccine strain and a biosafe strain for consideration of exclusion from the select agent list.

Recruitment of bone marrow-derived valve interstitial cells is a normal homeostatic process

Advances in understanding of the maintenance of the cardiac valves during normal cardiac function and response to injury have led to several novel findings, including that there is contribution of extra-cardiac cells to the major cellular population of the valve: the valve interstitial cell (VIC). While suggested to occur in human heart studies, we have been able to experimentally demonstrate, using a mouse model, that cells of bone marrow hematopoietic stem cell origin engraft into the valves and synthesize collagen type I. Based on these initial findings, we sought to further characterize this cell population in terms of its similarity to VICs and begin to elucidate its contribution to valve homeostasis. To accomplish this, chimeric mice whose bone marrow was repopulated with enhanced green fluorescent protein (EGFP) expressing total nucleated bone marrow cells were used to establish a profile of EGFP(+) valve cells in terms of their expression of hematopoietic antigens, progenitor markers, fibroblast- and myofibroblast-related molecules, as well as their distribution within the valves. Using this profile, we show that normal (non-irradiated, non-transplanted) mice have BM-derived cell populations that exhibit identical morphology and phenotype to those observed in transplanted mice. Collectively, our findings establish that the engraftment of bone marrow-derived cells occurs as part of normal valve homeostasis. Further, our efforts demonstrate that the use of myeloablative irradiation, which is commonly employed in studies involving bone marrow transplantation, does not elicit changes in the bone marrow-derived VIC phenotype in recipient mice.

Perfluorocarbon particle size influences magnetic resonance signal and immunological properties of dendritic cells

The development of cellular tracking by fluorine (¹⁹F) magnetic resonance imaging (MRI) has introduced a number of advantages for following immune cell therapies in vivo. These include improved signal selectivity and a possibility to correlate cells labeled with fluorine-rich particles with conventional anatomic proton (¹H) imaging. While the optimization of the cellular labeling method is clearly important, the impact of labeling on cellular dynamics should be kept in mind. We show by ¹⁹F MR spectroscopy (MRS) that the efficiency in labeling cells of the murine immune system (dendritic cells) by perfluoro-15-crown-5-ether (PFCE) particles increases with increasing particle size (560>365>245>130 nm). Dendritic cells (DC) are professional antigen presenting cells and with respect to impact of PFCE particles on DC function, we observed that markers of maturation for these cells (CD80, CD86) were also significantly elevated following labeling with larger PFCE particles (560 nm). When labeled with these larger particles that also gave an optimal signal in MRS, DC presented whole antigen more robustly to CD8+ T cells than control cells. Our data suggest that increasing particle size is one important feature for optimizing cell labeling by PFCE particles, but may also present possible pitfalls such as alteration of the immunological status of these cells. Therefore depending on the clinical scenario in which the ¹⁹F-labeled cellular vaccines will be applied (cancer, autoimmune disease, transplantation), it will be interesting to monitor the fate of these cells in vivo in the relevant preclinical mouse models.

Chicken CCR6 and CCR7 are markers for immature and mature dendritic cells respectively

In mammals, the CC chemokine receptors 6 and 7 (CCR6 and CCR7) play important roles in controlling the trafficking of dendritic cells (DC). CCR6 is expressed primarily on immature DC in the periphery and plays a role in the recruitment of immature DC to sites of potential antigen entry. On encountering pathogens, DC mature and migrate to secondary lymphoid organs where they present pathogen antigen to T cells to initiate specific adaptive immune responses. Maturation involves down-regulation of CCR6 but up-regulation of CCR7. To investigate the role of these two chemokine receptors in the function of DC in the chicken, a full-length chicken CCR7 (chCCR7) cDNA was cloned. Chicken CCR6 (chCCR6) was already available (Munoz et al., 2009). ChCCR7 shows the typical secondary structure of a seven-transmembrane G protein-coupled receptor and has 66% and 64% amino acid identity with human and mouse CCR7, respectively. Like its mammalian orthologues, chCCR7 mRNA was highly expressed in most lymphoid tissues (with the exception of the Harderian gland) and also in some non-lymphoid tissues (especially the heart, lung, skin and small intestine). Both chCCR6 and chCCR7 were expressed at the mRNA level in immature chicken bone marrow-derived dendritic cells (chBM-DC), as measured by real-time quantitative RT-PCR. After DC maturation following stimulation with LPS or CD40L, expression levels of chCCR6 mRNA were down-regulated, whereas those of chCCR7 were up-regulated, suggesting that these two chemokine receptors play a similar role in the trafficking of chicken DC as they do in mammals and that they act as markers of immature (chCCR6) and mature (chCCR7) DC.

A novel DC therapy with manipulation of MKK6 gene on nickel allergy in mice

Background

Although the activation of dermal dendritic cells (DCs) or Langerhans cells (LCs) via p38 mitogen-activated protein kinase (MAPK) plays a crucial role in the pathogenesis of metal allergy, the in vivo molecular mechanisms have not been identified and a possible therapeutic strategy using the control of dermal DCs or LCs has not been established. In this study, we focused on dermal DCs to define the in vivo mechanisms of metal allergy pathogenesis in a mouse nickel (Ni) allergy model. The effects of DC therapy on Ni allergic responses were also investigated.

Methods and Finding

The activation of dermal DCs via p38 MAPK triggered a T cell-mediated allergic immune response in this model. In the MAPK signaling cascade in DCs, Ni potently phosphorylated MAP kinase kinase 6 (MKK6) following increased DC activation. Ni-stimulated DCs could prime T cell activation to induce Ni allergy. Interestingly, when MKK6 gene-transfected DCs were transferred into the model mice, a more pronounced allergic reaction was observed. In addition, injection of short interfering (si) RNA targeting the MKK6 gene protected against a hypersensitivity reaction after Ni immunization. The cooperative action between T cell activation and MKK6-mediated DC activation by Ni played an important role in the development of Ni allergy.

Conclusions

DC activation by Ni played an important role in the development of Ni allergy. Manipulating the MKK6 gene in DCs may be a good therapeutic strategy for dermal Ni allergy.

Hepatitis B virus surface antigen can activate dendritic cells and modulate T helper type immune response

Hepatitis B virus surface antigen (HBsAg) is a major antigen of hepatitis B virus (HBV). Dendritic cells (DC) of HBV carriers have been reported to exhibit functional impairment. In this study, the role of HBsAg on mice bone marrow-derived dendritic cells and immune responses in vivo was studied. The immune modulatory function of HBsAg was explored by using mice bone marrow-derived dendritic cells in vitro and also by examining an ovalbumin (OVA) specific immune response in vivo. Treatment of dendritic cells with HBsAg resulted in enhanced cell surface expression of cluster of differentiation (CD) 80, CD83, CD86, and major histocompatibility complex (MHC) class II, and enhanced production of interleukin (IL)-12 p40 and IL-12 p70. Treatment of dendritic cells with HBsAg resulted in decreased T cell secretion of IL-5 by OVA stimulation. In addition, the results showed stronger OVA-specific immunoglobulin (Ig) M and weaker IgG responses in mice sera when they had been immunized with OVA and co-injected with HBsAg. It was also found that the mice exhibited significant enhancement of anti-OVA IgG2a antibody (Ab), as well as marked inhibition of IgG1 Ab production. In cellular immune responses, IL-5 production was significantly decreased and interferon (IFN)-γ increased in the group co-injected with HBsAg. On the other hand, the induction of lymphoproliferative response to OVA stimulation in spleen cells was decreased in the HBsAg co-injected group. These results demonstrate that HBsAg can affect the differentiation of T helper (Th) cells, which might provide a strategy for improving its prophylactic and therapeutic efficacy.

Combination approaches to immunotherapy: the radiotherapy example

The marquee cell of the immune response, the T lymphocyte, is exquisitely sensitive to ionizing radiation. Moreover, the majority of cells of the hematopoietic lineage, with their high turnover and radiation sensitivity, are effectively ablated by relatively low radiation doses, such that total-body irradiation is an effective immunosuppressive therapy. Despite and sometimes because of these facts, the immune system may underlie some portion of the therapeutic effects of radiation. In this review, we will discuss these processes, and go on to discuss current therapies combining radiation therapy with immunotherapy for the treatment of cancer.

Early myeloid dendritic cell dysregulation is predictive of disease progression in simian immunodeficiency virus infection

Myeloid dendritic cells (mDC) are lost from blood in individuals with human immunodeficiency virus (HIV) infection but the mechanism for this loss and its relationship to disease progression are not known. We studied the mDC response in blood and lymph nodes of simian immunodeficiency virus (SIV)-infected rhesus macaques with different disease outcomes. Early changes in blood mDC number were inversely correlated with virus load and reflective of eventual disease outcome, as animals with stable infection that remained disease-free for more than one year had average increases in blood mDC of 200% over preinfection levels at virus set-point, whereas animals that progressed rapidly to AIDS had significant loss of mDC at this time. Short term antiretroviral therapy (ART) transiently reversed mDC loss in progressor animals, whereas discontinuation of ART resulted in a 3.5-fold increase in mDC over preinfection levels only in stable animals, approaching 10-fold in some cases. Progressive SIV infection was associated with increased CCR7 expression on blood mDC and an 8-fold increase in expression of CCL19 mRNA in lymph nodes, consistent with increased mDC recruitment. Paradoxically, lymph node mDC did not accumulate in progressive infection but rather died from caspase-8-dependent apoptosis that was reduced by ART, indicating that increased recruitment is offset by increased death. Lymph node mDC from both stable and progressor animals remained responsive to exogenous stimulation with a TLR7/8 agonist. These data suggest that mDC are mobilized in SIV infection but that an increase in the CCR7-CCL19 chemokine axis associated with high virus burden in progressive infection promotes exodus of activated mDC from blood into lymph nodes where they die from apoptosis. We suggest that inflamed lymph nodes serve as a sink for mDC through recruitment, activation and death that contributes to AIDS pathogenesis.

Myeloid dendritic cells (mDC) are essential innate immune system cells that are lost from blood in human immunodeficiency virus infection through an ill-defined mechanism. We studied the kinetics of the mDC response in blood and lymph nodes of rhesus macaques infected with the closely related simian immunodeficiency virus. We found that differences in the number of blood mDC correlated with eventual disease outcome, as at virus set-point mDC were increased in blood in animals remaining disease free but lost from blood in animals that progressed rapidly to AIDS. mDC loss was linked to an increase in the chemokine axis responsible for mDC recruitment to lymph nodes; however, mDC did not accumulate in tissues but rather died from apoptosis. Lymph node mDC remained responsive to stimulation with a TLR7/8 agonist during infection. Importantly, mDC dysregulation was partially reversed by antiretroviral therapy. These data indicate that chronic mDC recruitment, activation and death within lymph nodes precede development of disease in SIV infected monkeys and may play a role in AIDS pathogenesis.