Dendritic cell CD83: a therapeutic target or innocent bystander?

Evaluation of the cytotoxic and immunomodulatory effects of sonodynamic therapy in human pancreatic cancer spheroids

Sonodynamic therapy (SDT) exploits the energy generated by ultrasound (US) to activate sound-sensitive drugs (sonosensitizers), leading to the generation of reactive oxygen species (ROS) and cancer cell death. Two-dimensional (2D) and three-dimensional (3D) cultures of human pancreatic cancer BxPC-3 cells were chosen as the models with which to investigate the therapeutic effects of the US-activated sonosensitizer IR-780 as pancreatic cancer is still one of the most lethal types of cancer. The effects of SDT, including ROS production, cancer cell death and immunogenic cell death (ICD), were extensively investigated. When subjected to US, IR-780 triggered significant ROS production and caused cancer cell death after 24 h (p ≤ 0.01). Additionally, the activation of dendritic cells (DCs) led to an effective immune response against the cancer cells undergoing SDT-induced death. BxPC-3 spheroids were developed and studied extensively to validate the findings observed in 2D BxPC-3 cell cultures. An analysis of the pancreatic cancer spheroid section revealed significant SDT-induced cancer cell death after 48 h after the treatment (p ≤ 0.01), with this being accompanied by the presence of SDT-induced damage-associated molecular patterns (DAMPs), such as calreticulin (CRT) and high mobility group box 1 (HMGB1). In conclusion, the data obtained demonstrates the anticancer efficacy of SDT and its immunomodulatory potential via action as an ICD-inducer.

CD83 acts as immediate early response gene in activated macrophages and exhibits specific intracellular trafficking properties

Macrophages (MΦ) are remarkably plastic cells, which assume phenotypes in every shade between a pro-inflammatory classical activation, and anti-inflammatory or resolving activation. Therefore, elucidation of mechanisms involved in shaping MΦ plasticity and function is key to understand their role during immunological balance. The immune-modulating CD83 molecule is expressed on activated immune cells and various tissue resident MΦ, rendering it an interesting candidate for affecting MΦ biology. However, in-depth analyses of the precise kinetics and trafficking of CD83 within pro-inflammatory, LPS activated bone-marrow-derived MΦ have not been performed. In this study, we show that activation with LPS leads to a very fast and strong, but transient increase of CD83 expression on these cells. Its expression peaks within 2 h of stimulation and is thereby faster than the early activation antigen CD69. To trace the CD83 trafficking through MΦs, we employed multiple inhibitors, thereby revealing a de novo synthesis and transport of the protein to the cell surface followed by lysosomal degradation, all within 6 h. Moreover, we found a similar expression kinetic and trafficking in human monocyte derived MΦ. This places CD83 at a very early point of MΦ activation suggesting an important role in decisions regarding the subsequent cellular fate.

Monocyte Maturation Mediators Upregulate CD83, ICAM-1 and MHC Class 1 Expression on Ewing's Sarcoma, Enhancing T Cell Cytotoxicity

Ewing's sarcoma (EwS) is a pediatric solid tumor entity with low somatic mutational burden and a low rate of tumor-infiltrating T cells, indicating a low extent of immunogenicity. In EwS, immunogenicity may furthermore be significantly diminished by a predominantly M2 macrophage driven pro-tumorigenic tumor microenvironment. In the past, we demonstrated that CHM1319-specific TCR-transgenic T cells are able to control EwS growth in a preclinical mouse model as well as in a patient with metastatic disease. However, new adjuvant techniques to induce long lasting and curative CHM1319-specific TCR-transgenic T cell-mediated anti-tumor responses are needed. In this work, we sought to identify a technique to improve the cytotoxic effect of CHM1319-specific TCR-transgenic T cell by altering the immunogenic cell surface marker expression on EwS cell lines using different cytokines. We demonstrate that TNF, IL-6, IL-1β and PGE2 cause pro-immunogenic CD83, MHC class I and II as well as ICAM-1 upregulation in EwS cell lines. This observation was associated with significantly improved recognition and killing of the tumor cells by EwS-specific CHM1319/HLA-A*02:01-restricted TCR-transgenic T cells. Conclusively, we demonstrate that the induction of an inflammatory signature renders EwS more susceptible to adoptive T cell therapy. TNF, which is upregulated during inflammatory processes, is of particular translational interest as its secretion may be induced in the patients e.g., by irradiation and hyperthermia in the clinical setting. In future clinical protocols, this finding may be important to identify appropriate conditioning regimens as well as point of time for adoptive T cell-based immunotherapy in EwS patients.

Ragweed plants grown under elevated CO2 levels produce pollen which elicit stronger allergic lung inflammation

BACKGROUND

Common ragweed has been spreading as a neophyte in Europe. Elevated CO₂ levels, a hallmark of global climate change, have been shown to increase ragweed pollen production, but their effects on pollen allergenicity remain to be elucidated.

METHODS

Ragweed was grown in climate-controlled chambers under normal (380 ppm, control) or elevated (700 ppm, based on RCP4.5 scenario) CO₂ levels. Aqueous pollen extracts (RWE) from control- or CO₂ -pollen were administered in vivo in a mouse model for allergic disease (daily for 3-11 days, n = 5) and employed in human in vitro systems of nasal epithelial cells (HNECs), monocyte-derived dendritic cells (DCs), and HNEC-DC co-cultures. Additionally, adjuvant factors and metabolites in control- and CO₂ -RWE were investigated using ELISA and untargeted metabolomics.

RESULTS

In vivo, CO₂ -RWE induced stronger allergic lung inflammation compared to control-RWE, as indicated by lung inflammatory cell infiltrate and mediators, mucus hypersecretion, and serum total IgE. In vitro, HNECs stimulated with RWE increased indistinctively the production of pro-inflammatory cytokines (IL-8, IL-1β, and IL-6). In contrast, supernatants from CO₂ -RWE-stimulated HNECs, compared to control-RWE-stimulated HNECS, significantly increased TNF and decreased IL-10 production in DCs. Comparable results were obtained by stimulating DCs directly with RWEs. The metabolome analysis revealed differential expression of secondary plant metabolites in control- vs CO₂ -RWE. Mixes of these metabolites elicited similar responses in DCs as compared to respective RWEs.

CONCLUSION

Our results indicate that elevated ambient CO₂ levels elicit a stronger RWE-induced allergic response in vivo and in vitro and that RWE increased allergenicity depends on the interplay of multiple metabolites.

Robust CD8+ T-cell proliferation and diversification after mogamulizumab in patients with adult T-cell leukemia-lymphoma

Skin-related adverse events (AEs) occur frequently in adult T-cell leukemia-lymphoma (ATL) patients treated with mogamulizumab, a humanized anti-CCR4 monoclonal antibody. This study was undertaken to elucidate the mechanisms of mogamulizumab-induced skin-related AEs. We analyzed the T-cell receptor β chain repertoire in ATL patients' peripheral blood mononuclear cells (PBMCs) before and after mogamulizumab. Skin-related AEs were present in 16 patients and were absent in 8 patients. Additionally, we included 11 patients before and after chemotherapy without mogamulizumab. Immune-related gene expression in PBMCs before and after mogamulizumab was also assessed (n = 24). Mogamulizumab treatment resulted in CCR4+ T-cell depletion, and the consequent lymphopenia provoked homeostatic CD8+ T-cell proliferation, as evidenced by increased expressions of CD8B and CD8A, which were significantly greater in patients with skin-related AEs than in those without them. We hypothesize that proliferation is driven by the engagement of self-antigens, including skin-related antigens, in the face of regulatory T-cell depletion. Together with the observed activated antigen presentation function, this resulted in T-cell diversification that was significantly greater in patients with skin-related AEs than in those without. We found that the CD8+ T cells that proliferated and diversified after mogamulizumab treatment were almost entirely newly emerged clones. There was an inverse relationship between the degree of CCR4+ T-cell depletion and increased CD8+ T-cell proliferation and diversification. Thus, lymphocyte-depleting mogamulizumab treatment provokes homeostatic CD8+ T-cell proliferation predominantly of newly emerging clones, some of which could have important roles in the pathogenesis of mogamulizumab-induced skin-related AEs.

Increased CD83 expression of CD34-positive monocytes in donors during peripheral blood stem cell mobilization in humans

CD34-positive monocytes (CD34+mono) have recently been identified in grafts mobilized by granulocyte-colony stimulating factor. We analyzed transplant outcomes of 73 patients whose donor's peripheral blood cells were cryopreserved during mobilization. CD34+mono was detected more frequently in male donors (67% vs. 40%, P = 0.03), while the detection of CD34+mono in donors was not associated with the patient background. Although there was no significant difference in overall survival in the whole cohort, the detection of CD34+mono in donors were significantly associated with a decreased risk of non-relapse mortality (HR 0.23, P = 0.035). Fatal infectious events tended to be less frequent in donors with CD34+mono. Gene expression profile analyses of CD34+mono in humans revealed that the expressions of pro-inflammatory cytokines like IL6, CCL3, IL8, VEGFA, and IL1A were elevated in CD34+mono, and those cytokines were enriched in the immune response, especially against infectious pathogens in the gene ontology analyses. In addition, the expression of CD83 was specifically increased in CD34+mono. It might play a role of antigen presentation in the immune network, leading in a clinical benefit against infections. Further investigations will be required to confirm the biological functions and clinical roles of CD34+mono in transplantation.

CD83 orchestrates immunity toward self and non-self in dendritic cells

Dendritic cells (DCs) are crucial to balance protective immunity and autoimmune inflammatory processes. Expression of CD83 is a well-established marker for mature DCs, although its physiological role is still not completely understood. Using a DC-specific CD83-conditional KO (CD83ΔDC) mouse, we provide new insights into the function of CD83 within this cell type. Interestingly, CD83-deficient DCs produced drastically increased IL-2 levels and displayed higher expression of the costimulatory molecules CD25 and OX40L, which causes superior induction of antigen-specific T cell responses and compromises Treg suppressive functions. This also directly translates into accelerated immune responses in vivo. Upon Salmonella typhimurium and Listeria monocytogenes infection, CD83ΔDC mice cleared both pathogens more efficiently, and CD83-deficient DCs expressed increased IL-12 levels after bacterial encounter. Using the experimental autoimmune encephalomyelitis model, autoimmune inflammation was dramatically aggravated in CD83ΔDC mice while resolution of inflammation was strongly reduced. This phenotype was associated with increased cell influx into the CNS accompanied by elevated Th17 cell numbers. Concomitantly, CD83ΔDC mice had reduced Treg numbers in peripheral lymphoid organs. In summary, we show that CD83 ablation on DCs results in enhanced immune responses by dysregulating tolerance mechanisms and thereby impairing resolution of inflammation, which also demonstrates high clinical relevance.

CD83: Activation Marker for Antigen Presenting Cells and Its Therapeutic Potential

CD83 is a member of the immunoglobulin (Ig) superfamily and is expressed in membrane bound or soluble forms. Membrane CD83 (mCD83) can be detected on a variety of activated immune cells, although it is most highly and stably expressed by mature dendritic cells (DC). mCD83 regulates maturation, activation and homeostasis. Soluble CD83 (sCD83), which is elevated in the serum of patients with autoimmune disease and some hematological malignancies is reported to have an immune suppressive function. While CD83 is emerging as a promising immune modulator with therapeutic potential, some important aspects such as its ligand/s, intracellular signaling pathways and modulators of its expression are unclear. In this review we discuss the recent biological findings and the potential clinical value of CD83 based therapeutics in various conditions including autoimmune disease, graft-vs.-host disease, transplantation and hematological malignancies.

Avian coronavirus infection induces mannose-binding lectin production in dendritic cell precursors of chicken lymphoid organs

The aim of this immunocytochemical study was to compare mannose-binding lectin (MBL) production induced by avian coronavirus in the spleen and caecal tonsil (CT). One-day-old specific-pathogen-free (SPF) chickens were experimentally infected with six QX field isolates and the H120 vaccine strain. In the negative control birds, the spleen was MBL negative, while the CT showed scattered MBL-positive cells in close proximity and within the surface epithelium and germinal centre (GC)-like cell clusters. MBL was detectable in the ellipsoid-associated cells (EACs) and cell clusters in the periarterial lymphoid sheath (PALS) by 7 days post infection (dpi). In both organs, the MBL-positive cells occupy antigen-exposed areas, indicating that GC formation depends on resident precursors of dendritic cells. The majority of MBL-positive EACs express the CD83 antigen, providing evidence that coronavirus infection facilitated the maturation of dendritic cell precursors. Surprisingly, co-localisation of MBL and CD83 was not detectable in the CT. In the spleen (associated with circulation), the EACs producing MBL and expressing CD83 are a common precursor of both follicular (FDC) and interdigitating dendritic cells (IDC). In the CT (gut-associated lymphoid tissue, GALT) the precursors of FDC and IDC are MBL-producing cells and CD83-positive cells, respectively. In the CT the two separate precursors of lymphoid dendritic cells provide some 'autonomy' for the GALT.

Advance in Targeted Immunotherapy for Graft-Versus-Host Disease

Graft-versus-host disease (GVHD) is a serious and deadly complication of patients, who undergo hematopoietic stem cell transplantation (HSCT). Despite prophylactic treatment with immunosuppressive agents, 20–80% of recipients develop acute GVHD after HSCT. And the incidence rates of chronic GVHD range from 6 to 80%. Standard therapeutic strategies are still lacking, although considerable advances have been gained in knowing of the predisposing factors, pathology, and diagnosis of GVHD. Targeting immune cells, such as regulatory T cells, as well as tolerogenic dendritic cells or mesenchymal stromal cells (MSCs) display considerable benefit in the relief of GVHD through the deletion of alloactivated T cells. Monoclonal antibodies targeting cytokines or signaling molecules have been demonstrated to be beneficial for the prevention of GVHD. However, these remain to be verified in clinical therapy. It is also important and necessary to consider adopting individualized treatment based on GVHD subtypes, pathological mechanisms involved and stages. In the future, it is hoped that the identification of novel therapeutic targets and systematic research strategies may yield novel safe and effective approaches in clinic to improve outcomes of GVHD further. In this article, we reviewed the current advances in targeted immunotherapy for the prevention of GVHD.

CD83 Antibody Inhibits Human B Cell Responses to Antigen as well as Dendritic Cell-Mediated CD4 T Cell Responses

Anti-CD83 Ab capable of Ab-dependent cellular cytotoxicity can deplete activated CD83+ human dendritic cells, thereby inhibiting CD4 T cell-mediated acute graft-versus-host disease. As CD83 is also expressed on the surface of activated B lymphocytes, we hypothesized that anti-CD83 would also inhibit B cell responses to stimulation. We found that anti-CD83 inhibited total IgM and IgG production in vitro by allostimulated human PBMC. Also, Ag-specific Ab responses to immunization of SCID mice xenografted with human PBMC were inhibited by anti-CD83 treatment. This inhibition occurred without depletion of all human B cells because anti-CD83 lysed activated CD83+ B cells by Ab-dependent cellular cytotoxicity and spared resting (CD83-) B cells. In cultured human PBMC, anti-CD83 inhibited tetanus toxoid-stimulated B cell proliferation and concomitant dendritic cell-mediated CD4 T cell proliferation and expression of IFN-γ and IL-17A, with minimal losses of B cells (<20%). In contrast, the anti-CD20 mAb rituximab depleted >80% of B cells but had no effect on CD4 T cell proliferation and cytokine expression. By virtue of the ability of anti-CD83 to selectively deplete activated, but not resting, B cells and dendritic cells, with the latter reducing CD4 T cell responses, anti-CD83 may be clinically useful in autoimmunity and transplantation. Advantages might include inhibited expansion of autoantigen- or alloantigen-specific B cells and CD4 T cells, thus preventing further production of pathogenic Abs and inflammatory cytokines while preserving protective memory and regulatory cells.

SV-BR-1-GM, a Clinically Effective GM-CSF-Secreting Breast Cancer Cell Line, Expresses an Immune Signature and Directly Activates CD4+ T Lymphocytes

Targeted cancer immunotherapy with irradiated, granulocyte–macrophage colony-stimulating factor (GM-CSF)-secreting, allogeneic cancer cell lines has been an effective approach to reduce tumor burden in several patients. It is generally assumed that to be effective, these cell lines need to express immunogenic antigens coexpressed in patient tumor cells, and antigen-presenting cells need to take up such antigens then present them to patient T cells. We have previously reported that, in a phase I pilot study (ClinicalTrials.gov NCT00095862), a subject with stage IV breast cancer experienced substantial regression of breast, lung, and brain lesions following inoculation with clinical formulations of SV-BR-1-GM, a GM-CSF-secreting breast tumor cell line. To identify diagnostic features permitting the prospective identification of patients likely to benefit from SV-BR-1-GM, we conducted a molecular analysis of the SV-BR-1-GM cell line and of patient-derived blood, as well as a tumor specimen. Compared to normal human breast cells, SV-BR-1-GM cells overexpress genes encoding tumor-associated antigens (TAAs) such as PRAME, a cancer/testis antigen. Curiously, despite its presumptive breast epithelial origin, the cell line expresses major histocompatibility complex (MHC) class II genes (HLA-DRA, HLA-DRB3, HLA-DMA, HLA-DMB), in addition to several other factors known to play immunostimulatory roles. These factors include MHC class I components (B2M, HLA-A, HLA-B), ADA (encoding adenosine deaminase), ADGRE5 (CD97), CD58 (LFA3), CD74 (encoding invariant chain and CLIP), CD83, CXCL8 (IL8), CXCL16, HLA-F, IL6, IL18, and KITLG. Moreover, both SV-BR-1-GM cells and the responding study subject carried an HLA-DRB3*02:02 allele, raising the question of whether SV-BR-1-GM cells can directly present endogenous antigens to T cells, thereby inducing a tumor-directed immune response. In support of this, SV-BR-1-GM cells (which also carry the HLA-DRB3*01:01 allele) treated with yellow fever virus (YFV) envelope (Env) 43–59 peptides reactivated YFV-DRB3*01:01-specific CD4⁺ T cells. Thus, the partial HLA allele match between SV-BR-1-GM and the clinical responder might have enabled patient T lymphocytes to directly recognize SV-BR-1-GM TAAs as presented on SV-BR-1-GM MHCs. Taken together, our findings are consistent with a potentially unique mechanism of action by which SV-BR-1-GM cells can act as APCs for previously primed CD4⁺ T cells.

The Role of Dendritic Cell Maturation in the Induction of Insulin-Dependent Diabetes Mellitus

Dendritic cells (DCs) are the dominant class of antigen-presenting cells in humans and are largely responsible for the initiation and guidance of innate and adaptive immune responses involved in maintenance of immunological homeostasis. Immature dendritic cells (iDCs) phagocytize pathogens and toxic proteins and in endosomal vesicles degrade them into small fragments for presentation on major histocompatibility complex (MHC) II receptor molecules to naïve cognate T cells (Th0). In addition to their role in stimulation of immunity, DCs are involved in the induction and maintenance of immune tolerance toward self-antigens. During activation, the iDCs become mature. Maturation begins when the DCs cease taking up antigens and begin to migrate from their location in peripheral tissues to adjacent lymph nodes or the spleen where during their continued maturation the DCs present stored antigens on surface MHCII receptor molecules to naive Th0 cells. During antigen presentation, the DCs upregulate the biosynthesis of costimulatory receptor molecules CD86, CD80, CD83, and CD40 on their plasma membrane. These activated DC receptor molecules bind cognate CD28 receptors presented on the Th0 cell membrane, which triggers DC secretion of IL-12 or IL-10 cytokines resulting in T cell differentiation into pro- or anti-inflammatory T cell subsets. Although basic concepts involved in the process of iDC activation and guidance of Th0 cell differentiation have been previously documented, they are poorly defined. In this review, we detail what is known about the process of DC maturation and its role in the induction of insulin-dependent diabetes mellitus autoimmunity.

Soluble CD83 Inhibits T Cell Activation by Binding to the TLR4/MD-2 Complex on CD14+ Monocytes

The transmembrane protein CD83, expressed on APCs, B cells, and T cells, can be expressed as a soluble form generated by alternative splice variants and/or by shedding. Soluble CD83 (sCD83) was shown to be involved in negatively regulating the immune response. sCD83 inhibits T cell proliferation in vitro, supports allograft survival in vivo, prevents corneal transplant rejection, and attenuates the progression and severity of autoimmune diseases and experimental colitis. Although sCD83 binds to human PBMCs, the specific molecules that bind sCD83 have not been identified. In this article, we identify myeloid differentiation factor-2 (MD-2), the coreceptor within the TLR4/MD-2 receptor complex, as the high-affinity sCD83 binding partner. TLR4/MD-2 mediates proinflammatory signal delivery following recognition of bacterial LPSs. However, altering TLR4 signaling can attenuate the proinflammatory cascade, leading to LPS tolerance. Our data show that binding of sCD83 to MD-2 alters this signaling cascade by rapidly degrading IL-1R-associated kinase-1, leading to induction of the anti-inflammatory mediators IDO, IL-10, and PGE2 in a COX-2-dependent manner. sCD83 inhibited T cell proliferation, blocked IL-2 secretion, and rendered T cells unresponsive to further downstream differentiation signals mediated by IL-2. Therefore, we propose the tolerogenic mechanism of action of sCD83 to be dependent on initial interaction with APCs, altering early cytokine signal pathways and leading to T cell unresponsiveness.

Altered heme-mediated modulation of dendritic cell function in sickle cell alloimmunization

Transfusions are the main treatment for patients with sickle cell disease. However, alloimmunization remains a major life-threatening complication for these patients, but the mechanism underlying pathogenesis of alloimmunization is not known. Given the chronic hemolytic state characteristic of sickle cell disease, resulting in release of free heme and activation of inflammatory cascades, we tested the hypothesis that anti-inflammatory response to heme is compromised in alloimmunized sickle patients, increasing their risk of alloimmunization. Heme-exposed monocyte-derived dendritic cells from both non-alloimmunized sickle patients and healthy donors inhibited priming of pro-inflammatory CD4(+) type 1 T cells, and exhibited significantly reduced levels of the maturation marker CD83. In contrast, in alloimmunized patients, heme did not reverse priming of pro-inflammatory CD4(+) cells by monocyte-derived dendritic cells or their maturation. Furthermore, heme dampened NF-κB activation in non-alloimmunized, but not in alloimmunized monocyte-derived dendritic cells. Heme-mediated CD83 inhibition depended on Toll-like receptor 4 but not heme oxygenase 1. These data suggest that extracellular heme limits CD83 expression on dendritic cells in non-alloimmunized sickle patients through a Toll-like receptor 4-mediated pathway, involving NF-κB, resulting in dampening of pro-inflammatory responses, but that in alloimmunized patients this pathway is defective. This opens up the possibility of developing new therapeutic strategies to prevent sickle cell alloimmunization.

Thymic CD4 T cell selection requires attenuation of March8-mediated MHCII turnover in cortical epithelial cells through CD83

Deficiency of CD83 in thymic epithelial cells (TECs) dramatically impairs thymic CD4 T cell selection. CD83 can exert cell-intrinsic and -extrinsic functions through discrete protein domains, but it remains unclear how CD83's capacity to operate through these alternative functional modules relates to its crucial role in TECs. In this study, using viral reconstitution of gene function in TECs, we found that CD83's transmembrane domain is necessary and sufficient for thymic CD4 T cell selection. Moreover, a ubiquitination-resistant MHCII variant restored CD4 T cell selection in Cd83(-/-) mice. Although during dendritic cell maturation CD83 is known to stabilize MHCII through opposing the ubiquitin ligase March1, regulation of March1 did not account for CD83's TEC-intrinsic role. Instead, we provide evidence that MHCII in cortical TECs (cTECs) is targeted by March8, an E3 ligase of as yet unknown physiological substrate specificity. Ablating March8 in Cd83(-/-) mice restored CD4 T cell development. Our results identify CD83-mediated MHCII stabilization through antagonism of March8 as a novel functional adaptation of cTECs for T cell selection. Furthermore, these findings suggest an intriguing division of labor between March1 and March8 in controlling inducible versus constitutive MHCII expression in hematopoietic antigen-presenting cells versus TECs.

Targeting membrane proteins for antibody discovery using phage display

A critical factor in the successful isolation of new antibodies by phage display is the presentation of a correctly folded antigen. While this is relatively simple for soluble proteins which can be purified and immobilized onto a plastic surface, membrane proteins offer significant challenges for antibody discovery. Whole cell panning allows presentation of the membrane protein in its native conformation, but is complicated by a low target antigen density, high background of irrelevant antigens and non-specific binding of phage particles to cell surfaces. The method described here uses transient transfection of alternating host cell lines and stringent washing steps to address each of these limitations. The successful isolation of antibodies from a naive scFv library is described for three membrane bound proteins; human CD83, canine CD117 and bat CD11b.

Malaria-derived hemozoin exerts early modulatory effects on the phenotype and maturation of human dendritic cells

Plasmodium falciparum (P. falciparum)-induced effects on the phenotype of human dendritic cells (DC) could contribute to poor induction of long-lasting protective immunity against malaria. DC ability to present antigens to naïve T cells, thus initiating adaptive immune responses depends on complex switches in chemokine receptors, production of soluble mediators and expression of molecules enabling antigen-presentation and maturation. To examine the cellular basis of these processes in the context of malaria, we performed detailed analysis of early events following exposure of human monocyte-derived DC to natural hemozoin (nHZ) and the synthetic analog of its heme core, β-hematin. DC exposed to either molecule produced high levels of the inflammatory chemokine MCP-1, showed continuous high expression of the inflammatory chemokine receptor CCR5, no upregulation of the lymphoid homing receptor CCR7 and no cytoskeletal actin redistribution with loss of podosomes. DC partially matured as indicated by increased expression of major histocompatibility complex (MHC) class II and CD86 following nHZ and β-hematin exposure, however there was a lack in expression of the maturation marker CD83 following nHZ but not β-hematin exposure. Overall our data demonstrate that exposure to nHZ partially impairs the capacity of DC to mature, an effect in part differential to β-hematin.

Cellular and molecular mechanisms in graft-versus-host disease

Graft-versus-host disease is a complication in patients undergoing hematopoietic stem cell transplantation. Graft-versus-host disease includes acute graft-versus-host disease and chronic graft-versus-host disease. Host APCs (e.g., dendritic cells and macrophages), effector T cells (e.g., Th1, Th17, and abnormal Th17:regulatory T cell ratio), B cells, and NK cells are implicated in graft-versus-host disease physiopathology. Proinflammation cytokines (e.g., IL-17, IL-1β, and TNF-α) are increased in graft-versus-host disease . Costimulatory molecules play an important role in inducing graft-versus-host disease . Pattern-recognition receptors, such as TLRs and nucleotide-binding oligomerization domain-like receptors, are critically involved in the pathogenesis of graft-versus-host disease . Complement system C3 mediates Th1/Th17 polarization in human T cell activation and skin graft-versus-host disease. Accumulation of CD26 T cells in graft-versus-host disease target organs was found. As a therapeutic target, soluble CD83 molecules or antibodies have been demonstrated to have therapeutic effects against graft-versus-host disease, and signaling molecules promote the inflammatory and immune process of graft-versus-host disease . These immune cells and molecules could be the predictors of graft-versus-host disease development and the drug targets of the treatments for graft-versus-host disease. This article focuses on major advances on cellular and molecular mechanisms in graft-versus-host disease.

In vitro and in vivo studies of the immunomodulatory effect of Echinacea purpurea on dendritic cells

BACKGROUND

Extracts of Echinacea have been used traditionally for the treatment of diverse types of infections and wounds. They have become very familiar immunostimulant herbal medicine. However, the specific immunomodulatory effect of Echinacea remains to be elucidated.

AIM

In our study, the effect of Echinacea purpurea extract on the generation of immature DCs from monocytes was described, as well as its effect on DC differentiation. In addition, an in vivo experiment was conducted to investigate whether treatment of mice with extracts derived from E. purpurea has immunomodulatory effect on murine splenic DCs.

METHODS

Immature DCs were generated by incubating peripheral blood monocytes with cytokine cocktail (GM-CSF + IL-4) and matured by tumor necrosis factor-α (TNF-α). The cells were randomized to 5 groups to investigate E. purpurea effect in different stages. Phenotypic analysis of cell marker CD83-expressed on DCs was performed by flow cytometry. Mice were randomly divided into 3 groups; control, E. purpurea treated and E. purpurea-TNF-α treated group. The murine splenic DCs were isolated and phenotyped for CD83 and CD11c by flow cytometry.

RESULTS

Treatment of monocytes with E. purpurea prior to addition of the maturation factor TNF-α resulted in a significant decrease in the yield of DC expressing CD83. On the other hand, immature DCs generated in the culture in the presence of GM-CSF and IL-4, when treated simultaneously with E. purpurea and TNF-α, exhibited an insignificant change in the yield of CD83-expressing DCs compared with untreated control. The in vivo experiments showed that splenic DCs obtained from mice treated with E. purpurea with or without TNF-α did not exhibit significant changes in CD83 or CD11c compared with those obtained from control mice.

CONCLUSION

Our findings suggest that the immunomodulatory mechanisms of E. purpurea impact generation fate of DCs rather than differentiation stages. The results obtained in the in vivo study utilizing murine splenic DCs supported those observed in vitro.

Toscana virus infects dendritic and endothelial cells opening the way for the central nervous system

Toscana virus (TOSV) is a Phlebovirus responsible for human neurological infections in endemic Mediterranean areas. The main viral target is the central nervous system, with viremia as a way of dissemination throughout the host. This study was aimed at understanding the spread of TOSV in the host by identifying the cell population infected by the virus and the vehicle to the organs. In vivo studies provided evidence that endothelial cells are infected by TOSV, indicating their potential role in the diffusion of the virus following viremic spread. These results were further confirmed in vitro. Human peripheral mononuclear blood cells were infected with TOSV; only monocyte-derived dendritic cells were identified as susceptible to TOSV infection. Productive viral replication was then observed in human monocyte-derived dendritic cells (moDCs) and in human endothelial cells by recovery of the virus from a cell supernatant. Interleukin-6 was produced by both cell types upon TOSV infection, mostly by endothelial cells, while moDCs particularly expressed TNF-α, which is known to induce a long-lasting decrease in endothelial cell barrier function. These cells could therefore be implicated in the spread of the virus in the host and in the infection of tissues that are affected by the disease, such as the central nervous system. The identification of in vitro and in vivo TOSV cell targets is an important tool for understanding the pathogenesis of the infection, providing new insight into virus-cell interaction for improved knowledge and control of this viral disease.

The expression and characterization of functionally active soluble CD83 by Pichia pastoris using high-density fermentation

CD83 is a highly glycosylated type I transmembrane glycoprotein that belongs to the immunoglobulin superfamily. CD83 is upregulated during dendritic cell (DC) maturation, which is critical for the initiation of adaptive immune responses. The soluble isoform of CD83 (sCD83) is encoded by alternative splicing from full-length CD83 mRNA and inhibits DC maturation, which suggests that sCD83 acts as a potential immune suppressor. In this study, we developed a sound strategy to express functional sCD83 from Pichia pastoris in extremely high-density fermentation. Purified sCD83 was expressed as a monomer at a yield of more than 200 mg/L and contained N-linked glycosylation sites that were characterized by PNGase F digestion. In vitro tests indicated that recombinant sCD83 bound to its putative counterpart on monocytes and specifically blocked the binding of anti-CD83 antibodies to cell surface CD83 on DCs. Moreover, sCD83 from yeast significantly suppressed ConA-stimulated PBMC proliferation. Therefore, sCD83 that was expressed from the P. pastoris was functionally active and may be used for in vivo and in vitro studies as well as future clinical applications.

Differential effects of estradiol on carotid artery inflammation when administered early versus late after surgical menopause

OBJECTIVE

The aim of this study was to determine the effects of estrogen therapy (ET) on carotid artery inflammation when initiated early and late relative to surgical menopause.

METHODS

Female cynomolgus macaques consuming atherogenic diets were ovariectomized and randomized to control or oral estradiol (E2; human equivalent dose of 1 mg/d micronized E2) initiated at 1 month (early menopause, n = 24) or 54 months (late menopause, n = 40) after ovariectomy. The treatment period was 8 months. Carotid artery expression of the markers of monocyte/macrophages (CD68 and CD163), dendritic cells (CD83), natural killer cells (neural cell adhesion molecule-1), and interferon-γ was significantly lower in E2-treated animals in the early menopause group but not in the late menopause group (P < 0.05). In contrast, carotid artery transcripts for T-cell markers (CD3, CD4, CD8, and CD25), interleukin-10, type I collagen, monocyte chemoattractant protein-1, matrix metalloproteinase-9, and tumor necrosis factor-α were lower in E2-treated monkeys regardless of menopausal stage (P < 0.05).

CONCLUSIONS

ET initiated soon after menopause inhibits macrophage accumulation in the carotid artery, an effect that is not observed when E2 is administered after several years of estrogen deficiency. No evidence for pro-inflammatory effects of late ET is observed. The results provide support for the timing hypothesis of postmenopausal ET with implications for the interpretation of outcomes in the Women's Health Initiative.

Production and characterization of human soluble CD83 fused with the fragment crystallizable region of human IgG1 in Pichia pastoris

The cell surface protein CD83 belongs to the immunoglobulin superfamily and is highly expressed on mature dendritic cells. The soluble form of CD83, sCD83, is a potential immune suppressor. In a previous study, recombinant soluble CD83 was expressed in Escherichia coli, resulting in a lack of functional glycosylation. Although eukaryotic cell systems for producing sCD83 offer the advantages of protein processing, folding, and posttranslational modification, these systems are complicated, expensive, and produce low levels of protein. To obtain more efficient expression of sCD83, we expressed human sCD83 fused with fragment crystallizable region of human IgG1 (hIgG1 Fc) in Pichia pastoris. Under the optimal conditions (time of induction, 48 h; inoculum density (OD600), 80; concentration of methanol, 3.0 %; pH 7.0-8.0; concentration of casamino acid, 5.0 %), the purified human sCD83-hIgG1 Fc (hsCD83-Ig) fusion protein existed as dimers at 25-30 mg/L culture. Treatment with PNGase F showed that purified hsCD83-Ig was modified by N-linked glycosylation. Moreover, the hsCD83-Ig expressed in the P. pastoris system could suppress lymphocyte proliferation in ConA-stimulated and one-way mixed lymphocyte reaction systems. Thus, hsCD83-Ig expressed in P. pastoris is functional and may be used in experimental therapies for graft rejection, graft-versus-host disease, and autoimmune diseases.

In vivo confocal microscopy and histopathology of the conjunctiva in trachomatous scarring and normal tissue: a systematic comparison

AIM

To compare in vivo confocal microscopy (IVCM) with the histopathological examination of tissue and cellular changes in normal and diseased conjunctiva.

METHODS

Participants underwent clinical examination and IVCM of the tarsal conjunctiva. A biopsy of the upper tarsal conjunctiva was collected and stained with tinctorial stains and by immunohistochemical staining for CD45 and CD83. Connective tissue scarring, inflammatory cell density and the presence of dendritiform cells were quantitatively assessed in a masked manner by both IVCM and histological assessments for comparative analysis.

RESULTS

Thirty-four participants with severe trachomatous conjunctival scarring and 33 participants with healthy conjunctiva were recruited. The IVCM connective tissue scarring score was strongly associated with the histological grading of scarring (p<0.001). There was limited evidence of an association between the IVCM inflammatory cell infiltrate and the histological inflammatory cell grade (p=0.05). We did not find any evidence to support the hypothesis that dendritiform cells seen with IVCM are mature, conventional dendritic cells.

CONCLUSIONS

The results show that IVCM can be used to robustly quantitate connective tissue scarring and also has a role in measuring the inflammatory cell infiltrate. The discordance between IVCM dendritiform cells and immunohistochemical dendritic cells may be a result of study limitations or may be because these dendritiform structures represent another cell type, such as fibroblasts, rather than dendritic cells.

Targeting CD83 for the treatment of graft-versus-host disease

Graft-versus-host disease (GVHD) is a common and often fatal complication of bone marrow transplantation. Antigen-presenting cells from donor and recipient play a critical role in the initiation and maintenance of GVHD. CD83, which is expressed in activated lymphocytes and dendritic cells, is regarded as a marker of mature dendritic cells. Targeting CD83 using soluble CD83 molecules or antibodies has been demonstrated to have therapeutic effects against GVHD in preclinical models. Understanding the biological function of CD83 and the underlying mechanisms through which targeting CD83 attenuates GVHD is likely to greatly improve current treatments and provide new methods for the treatment of GVHD.

Inhibition of dendritic cell maturation by the tumor microenvironment correlates with the survival of colorectal cancer patients following bevacizumab treatment

Development of bevacizumab has improved survival in colorectal cancer, however, currently there are no biomarkers that predict response to bevacizumab and it is unknown how it influences the immune system in colorectal cancer patients. Dendritic cells are important for the induction of an antitumor immune response; however tumors are capable of disabling dendritic cells and escaping immune surveillance. The aim of this study was to assess the numbers of CD11c+ cells infiltrating tumor tissue and to examine the effects of tumor conditioned media (TCM) and bevacizumab conditioned media (BCM) on dendritic cell maturation and correlate our findings with patient survival. colorectal cancer explant tissues were cultured with or without bevacizumab, to generate BCM and TCM, which were used to treat dendritic cells. CD80, CD86, CD83, CD54, HLA-DR, and CD1d expression was measured by flow cytometry. Interleukin (IL)-10 and IL-12p70 were measured by ELISA. The Cox proportional hazards model was used to associate survival with dendritic cell inhibition. TCM and BCM inhibited lipopolysaccharide (LPS)-induced dendritic cell maturation and IL-12p70 secretion (P < 0.0001), while increasing IL-10 secretion (P = 0.0033 and 0.0220, respectively). Inhibition of LPS-induced CD1d (P = 0.021, HR = 1.096) and CD83 (P = 0.017, HR = 1.083) by TCM and inhibition of CD1d (P = 0.017, HR = 1.067), CD83 (P = 0.032, HR = 1.035), and IL-12p70 (P = 0.037, HR = 1.036) by BCM was associated with poor survival in colorectal cancer patients. CD11c expression was elevated in tumor tissue compared with normal tissue (P < 0.001), but this did not correlate with survival. In conclusion, TCM and BCM inhibit dendritic cells, and this inhibition correlates with survival of colorectal cancer patients receiving bevacizumab.

Dendritic cells and their role in tumor immunosurveillance

Dendritic cells (DCs) comprise a heterogeneous population of cells that play a key role in initiating, directing and regulating adaptive immune responses, including those critically involved in tumor immunosurveillance. As a riposte to the central role of DCs in the generation of antitumor immune responses, tumors have developed various mechanisms which impair the immunostimulatory functions of DCs or even instruct them to actively contribute to tumor growth and progression. In the first part of this review we discuss general aspects of DC biology, including their origin, subtypes, immature and mature states, and functional plasticity which ensures a delicate balance between active immune response and immune tolerance. In the second part of the review we discuss the complex interactions between DCs and the tumor microenvironment, and point out the challenges faced by DCs during the recognition of tumor Ags. We also discuss the role of DCs in tumor angiogenesis and vasculogenesis.

A CD83-like molecule in sea bass (Dicentrarchus labrax): molecular characterization and modulation by viral and bacterial infection

The CD83 cell surface marker is an important and intriguing component of immune system. It is considered the best marker for mature human dendritic cells, but it is also important for thymic development of T cells, and it also plays a role as a regulator of peripheral B-cell function and homeostasis. A CD83-like molecule was identified in sea bass (Dicentrarchus labrax) by EST sequencing of a thymus cDNA library; the CD83 cDNA is composed of 816 bp and the mature CD83 peptide consists of 195 amino acids, with a putative signal peptide of 18 amino acids and two possible N-glycosylation sites. The comparison of sea bass CD83 sequence with its homologues in other fish species and mammals shows some differences, with two cysteine residues conserved from fish to mammals and a high variability both in the total number of cysteines and in mature CD83 sequence polypeptide length. Basal transcripts levels of CD83 mRNA are highest in liver, followed by thymus. The in vitro treatment of head kidney leukocytes with LPS resulted in a down-regulation on CD83 mRNA leves both after 4 and 24 h, whereas with poly I:C an up-regulation after 4h followed by a down-regulation at 24 h was observed. An in vivo infection of sea bass juveniles with nodavirus induced an increase of CD83 expression on head kidney leukocytes both after 6 and 24 h and a decrease after 72 h. On the other hand, an in vivo infection with Photobacterium damselae bacteria induced a decrease of CD83 transcript levels after 6 and 24 h and an increase after 72 h. These findings suggest in sea bass CD83 expression could be modulated by viral and bacterial immune response.

In vitrocomparison of commensal, probiotic and pathogenic strains ofEnterococcus faecalis

In vivostudies have provided evidence that micro-organisms have important roles in immunological, digestive and respiratory functions, conferring health benefits on the host. Severalin vitromethods have been advised for the initial screening of microbes with potential health effects. The objective of the present study was to employ suchin vitromethodology to characterise different strains ofEnterococcus faecalis. The characteristics of a commercial product marketed as a probiotic, Symbioflor-1 (Symbiopharm), were compared with the characteristics of both pathogenic and commensal strains. Tolerance towards low pH and viability after exposure to human gastric and duodenal juices were assayed. Symbioflor-1 was the most susceptible strain to these treatments when compared with the otherE. faecalisstrains. Furthermore, Symbioflor-1 exhibited the lowest adhesion capacity to intestinal epithelial cells (IEC) and mucus. Competitive binding studies using heparin indicated that glycosaminoglycans might be involved in the adhesion to IEC, but also that differences in these putative bacteria–host interactions do not cause the relative low adhesion capacity of Symbioflor-1. Maturation of dendritic cells (DC) after exposure to bacteria was assayed as an indication of an immunomodulatory effect. All strains induced a moderate elevation of the DC maturation markers CD83 and CD86; however, no strain-specific differences were detected. Correlations betweenin vitroandin vivostudies are discussed. Althoughin vitroassaying is a rational starting point for the selection of microbes with a potential health benefit, it is emphasised that human clinical trials are the definite tool for establishing probiotic status.

Development and characterization of mouse monoclonal antibodies reactive with chicken CD83

This study was carried out to develop and characterize mouse monoclonal antibodies (mAbs) against chicken CD83 (chCD83), a membrane-bound glycoprotein belonging to the immunoglobulin superfamily that is primarily expressed on mature dendritic cells (DCs). A recombinant chCD83/IgG4 fusion protein containing the extracellular region of chCD83 was expressed in Chinese Hamster Ovary (CHO) cells and isolated from the spent cell culture medium by protein G affinity chromatography. The extracellular region of the chCD83 protein was purified and used to immunize mice. A cell fusion was performed, from which 342 hybridomas were screened for mAbs to chCD83. Two mAbs, chCD83-159 and chCD83-227, stained the greatest percentage of chCD83-transfected CHO cells and were selected for further characterization. By flow cytometry, both mAbs reacted with a chicken macrophage cell line, HD11. Both mAbs also recognized a single 53 kDa protein on Western blots of lysates from lipopolysaccharide-stimulated spleen mononuclear cells or unstimulated HD11 cells. Immunostaining of chicken secondary lymphoid organs identified chCD83(+) cells with morphologic and subtissue localization properties comparable to mammalian DCs. In vitro stimulation of spleen mononuclear cells with concanavalin A (Con A) decreased the percentage of chCD83(+) cells compared with cells treated with medium alone. Interestingly, spleen cells treated with Con A in the presence of chCD83-227 mAb exhibited decreased percentage of MHCII(+) cells compared with cells treated with an isotype-matched negative control mAb. These chCD83 mAbs may be useful for future investigations of chicken immune cell maturation and mechanisms of action.

Functional characterization of the HuR:CD83 mRNA interaction

Maturation of dendritic cells (DC) is characterized by expression of CD83, a surface protein that appears to be necessary for the effective activation of naïve T-cells and T-helper cells by DC. Lately it was shown that CD83 expression is regulated on the posttranscriptional level by interaction of the shuttle protein HuR with a novel posttranscriptional regulatory RNA element (PRE), which is located in the coding region of the CD83 transcript. Interestingly, this interaction commits the CD83 mRNA to efficient nuclear export via the CRM1 pathway. To date, however, the structural basis of this interaction, which potentially involves three distinct RNA recognition motifs (RRM1–3) in HuR and a complex three-pronged RNA stem-loop element in CD83 mRNA, has not been investigated in detail. In the present work we analyzed this interaction in vitro and in vivo using various HuR- and CD83 mRNA mutants. We are able to demonstrate that both, RRM1 and RRM2 are crucial for binding, whereas RRM3 as well as the HuR hinge region contributed only marginally to this protein∶RNA interaction. Furthermore, mutation of uridine rich patches within the PRE did not disturb HuR:CD83 mRNA complex formation while, in contrast, the deletion of specific PRE subfragments from the CD83 mRNA prevented HuR binding in vitro and in vivo. Interestingly, the observed inhibition of HuR binding to CD83 mRNA does not lead to a nuclear trapping of the transcript but rather redirected this transcript from the CRM1- towards the NXF1/TAP-specific nuclear export pathway. Thus, the presence of a functional PRE permits nucleocytoplasmic trafficking of the CD83 transcript via the CRM1 pathway.

CD83 increases MHC II and CD86 on dendritic cells by opposing IL-10-driven MARCH1-mediated ubiquitination and degradation

Effective vaccine adjuvants must induce expression of major histocompatibility (MHC) class II proteins and the costimulatory molecule CD86 on dendritic cells (DCs). However, some adjuvants elicit production of cytokines resulting in adverse inflammatory consequences. Development of agents that selectively increase MHC class II and CD86 expression without triggering unwanted cytokine production requires a better understanding of the molecular mechanisms influencing the production and degradation of MHC class II and CD86 in DCs. Here, we investigate how CD83, an immunoglobulin protein expressed on the surface of mature DCs, promotes MHC class II and CD86 expression. Using mice with an N-ethyl-N-nitrosourea-induced mutation eliminating the transmembrane (TM) region of CD83, we found that the TM domain of CD83 enhances MHC class II and CD86 expression by blocking MHC class II association with the ubiquitin ligase MARCH1. The TM region of CD83 blocks interleukin 10-driven, MARCH1-dependent ubiquitination and degradation of MHC class II and CD86 in DCs. Exploiting this posttranslational pathway for boosting MHC class II and CD86 expression on DCs may provide an opportunity to enhance the immunogenicity of vaccines.

Prevention of chronic renal allograft rejection by soluble CD83

BACKGROUND

Recombinant human soluble CD83 had previously exhibited significant immunosuppressive properties that involved interference with dendritic cell maturation in both mouse and humans, inhibition of autoimmunity in mice, and induction of antigen-specific mouse cardiac allograft tolerance when used in combination with other immunosuppressive drugs. Our current research focus turned to examining the effects of peritransplant soluble CD83 (sCD83) administration on prevention of chronic renal allograft rejection.

METHODS

Fisher344-to-Lewis orthotopic rat renal transplants were performed with sequential recipient killing on postoperative days (PODs) 2, 14, and 140 to examine both the acute and chronic effects of peritransplant sCD83 treatment in rat recipients.

RESULTS

Recipients treated with sCD83 exhibited a marked decrease in IgM and IgG deposition in the graft and antidonor antibody levels in the circulation, as early as POD14 and persisting until POD140. sCD83 treatment also reduced the infiltration of T cells and monocytes into the graft tissue and inhibited intragraft expression of MyD88 and inflammatory cytokine levels during the observation period. sCD83-treated grafts demonstrated normal histology beyond POD140, including dramatic reductions in tubular atrophy and interstitial fibrosis compared with untreated recipients.

CONCLUSION

We have demonstrated that peritransplant treatment with recombinant sCD83 attenuates both innate and adaptive immune responses and leads to prevention of chronic rejection in a rat renal transplant model. Because sCD83 is of human origin, the therapeutic approach used in our rodent transplant model holds significant promise for clinical transplantation.

On the role of dendritic cells in the pathogenesis of vitiligo

The authors give the results of immunohistochemistry studies of the skin of 16 healthy volunteers and 16 patients suffering from vulgar vitiligo with the determination of the contents of immature (CD1a+) and mature (CD83+) subpopulations of dendritic cells (DCs) as well as CD4+ and CD8+ lymphocytes in the epidermis and perivascular infiltrates of the derma. They revealed an increased quantity of CD1a+ and CD83+ DCs in areas of depigmented, peripheral and perifocal normally pigmented skin of vitiligo foci. DCs with the CD1a+ phenotype were revealed both in the epidermis and in the derma while DCs with the CD83+ phenotype were revealed in the derma only. A higher quantity of CD4+ and CD8+ lymphocytes than in healthy volunteers was also revealed along with the increased contents of DCs in all three areas of vitiligo foci. The authors established a strong correlation between the quantity of CD83+ DCs and CD4+ lymphocytes in the depigmentation zone (r=0.84; Р

Mycobacterium bovis bacillus Calmette-Guerin treated human cord blood monocyte-derived dendritic cells polarize naïve T cells into a tolerogenic phenotype in newborns

BACKGROUND

As one of the first infectious challenges of life, the impact of neonatal Mycobacterium bovis bacillus Calmette-Guerin (BCG) vaccination on the polarization of neonatal T helper subset has not been well defined.

METHODS

We investigated the effect of BCG-treated cord blood (CB) dendritic cells (DCs) on naïve CD4+ T cells polarization compared with that of adult blood DCs.

RESULTS

BCG-treated CB DCs had significantly lower expression of CD83 and a higher ratio of CD47/Fas than BCG-treated adult blood DCs. BCG induced significantly lower IL-12 but relatively higher IL-10 production from CB DCs than adult blood DCs. Moreover, in comparison with BCG-treated adult blood DCs, BCG-treated CB DCs induced higher IL-10 production and cytotoxic T-lymphocyte antigen 4 (CTLA-4) expression, and lower interferon-gamma (IFN-gamma) production from naïve CD4+ T cells. On the other hand, lipopolysaccharide-treated CB DCs had similar capacity as prime naïve CD4+ T cells did to produce higher IFN-gamma, lower IL-10 production, and CTLA-4 expression compared with their adult counterparts.

CONCLUSION

These results suggested that BCG-treated CB DCs might be semi-mature DCs which polarize naïve T cells into a tolerogenic T cell phenotype in newborns.

Neuronal expression of Cd36, Cd44, and Cd83 antigen transcripts maps to distinct and specific murine brain circuits

Cells recruited by the innate immune response rely on surface-expressed molecules in order to receive signals from the local environment and to perform phagocytosis, cell adhesion, and others processes linked to host defense. Hundreds of surface antigens designated through a cluster of differentiation (CD) number have been used to identify particular populations of leukocytes. Surprisingly, we verified that the genes that encode Cd36 and Cd83 are constitutively expressed in specific neuronal cells. For instance, Cd36 mRNA is expressed in some regions related to circuitry involved in pheromone responses and reproductive behavior. Cd44 expression, reanalyzed and detailed here, is associated with the laminar formation and midline thalamic nuclei in addition to striatum, extended amygdala, and a few hypothalamic, cortical, and hippocampal regions. A systemic immune challenge was able to increase Cd44 expression quickly in the area postrema and motor nucleus of the vagus but not in regions presenting expressive constitutive expression. In contrast to Cd36 and Cd44, Cd83 message was widely distributed from the olfactory bulb to the brain stem reticular formation, sparing the striatopallidum, olivary region, and cerebellum. Its pattern of expression nevertheless remained strongly associated with hypothalamic, thalamic, and hindbrain nuclei. Unlike the other transcripts, Cd83 mRNA was rapidly modulated by restraint stress. Our results indicate that these molecules might play a role in specific neural circuits and present functions other than those attributed to leukocyte biology. The data also suggest that these surface proteins, or their associated mRNA, could be used to label neurons in specific circuits/regions.

Modulating dendritic cells (DC) from immunogenic to tolerogenic responses: a novel mechanism of AZA/6-MP

Azathioprine (Aza), 6-Mercaptopurine (6-MP) and 6-Thioguanine (6-TG) are thiopurine drugs widely used as immunosuppressants/anti-inflammatory agents in organ transplantation and chemotherapy. Aza is well tolerated and effective in modifying the course of MS. Here we investigated the action of 6-MP on human dendritic cells (DCs). We described for the first time that 6-MP impairs in vitro differentiation of DCs, has an inhibitory effect during DC activation processes inducing a functionally less immunogenic phenotype. Moreover, 6-MP significantly reduces DC IL-23 production and CCR7 expression, at the same time induces IL-10 augmentation. All these findings add a novel action mechanism in Aza immune modulation.

Etanercept impairs maturation of human monocyte-derived dendritic cells by inhibiting the autocrine TNFalpha-mediated signaling

The success of anti-tumor necrosis factor alpha (TNFalpha) therapies has led to increased interest as to the mechanisms and consequences of TNFalpha blockade. The aim of the study was to examine the effects of TNFalpha blockade by etanercept on lipopolysaccharide (LPS) or peptidoglycan (PG)-induced maturation of human monocyte-derived dendritic cells (MDDCs). MDDCs grown from peripheral blood of healthy donors were stimulated by LPS or PG with/without the presence of etanercept. Concentrations of TNFalpha in cell supernatants were assessed by ELISA, while the cells were stained with monoclonal antibodies to CD83, CD80, CD86, CD11c, CD40, HLA-DR, and annexin-V and acquired using a flow cytometer. Etanercept significantly decreased the stimulated cell surface expression of HLA-DR, CD80, CD86, CD40 and CD83 on MDDCs in all examined samples. Etanercept in the same dose, but denatured to loss of specificity for TNFalpha, failed to change any of the aforementioned markers. In the presence of etanercept, concentrations of TNFalpha in cell supernatants were decreased by 53% on average, with a range of 25%-87%. Etanercept impaired the stimulated maturation of MDDCs by neutralizing the induced TNFalpha, produced by the same MDDCs after antigenic stimulation. The reported data confirms that TNFalpha blockade may have a direct effect on DCs, with a wide spectrum of potential secondary effects downstream. The data also suggests the presence of TNFalpha-mediated autocrine signaling, serving to accelerate or catalyze the maturation process of MDDCs.

Release and clinical significance of soluble CD83 in chronic lymphocytic leukemia

Soluble CD83 (sCD83), a potent immunosuppressive agent, circulates at elevated levels in some chronic lymphocytic leukemia (CLL) patients. We report that CLL patients with elevated plasma sCD83 levels had significantly shorter (P=0.038) treatment free survival. Culture of CLL cells with solid phase CD83 mAb+IL-4 significantly increases sCD83 release (23-117-fold, P=0.013) and ligation of normal donor PBMC with solid phase CD83 mAb alone induces similar significant increases in sCD83 release (P=0.003). RT-PCR analysis detected the presence of a transcript for sCD83 in 2/3 CLL samples. These results suggest sCD83 release may play a regulatory role in CLL progression.

Impact of alpha-defensins1-3 on the maturation and differentiation of human monocyte-derived DCs. Concentration-dependent opposite dual effects

alpha-defensins1-3 are potent antimicrobial molecules that also link innate and adaptive immunity, depending on the concentration range. However, their effects on the biology of human DCs remain largely unknown. We analyzed the impact of different concentrations of alpha-defensins1-3 on the maturation and differentiation of monocyte-derived DCs (MDDCs). Low doses of alpha-defensins1-3 up-regulated CD83, CD86 and HLA-DR expression, increased TNF-alpha, IL-1beta, IL-12p40, IL-10 and IL-8 secretion, and slightly augmented allostimulatory capacity. By contrast, high doses down-regulated CD86 and HLA-DR expression, TNF-alpha, IL-1beta, IL-12p40 and IL-10 secretion and allostimulatory capacity, whereas strongly up-regulated IL-8. Furthermore, during the MDDC differentiation process, high doses of alpha-defensins1-3 affected CD14, CD11c and CD86 expression and strongly up-regulated IL-8. Results suggest that alpha-defensins1-3 might modulate the maturation and differentiation of MDDCs in vivo and therefore could be of special interest in the field of vaccine development.

Generation of functionally mature dendritic cells from elutriated monocytes using polyinosinic : polycytidylic acid and soluble CD40 ligand for clinical application

Despite the increasing use of dendritic cell (DC) vaccination in clinical trials, optimal conditions for the generation of functionally mature DCs remain to be established. The current standard DC maturation protocol for clinical trials has been used as an inflammatory cytokine cocktail [tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6 and prostaglandin E(2)], but this cocktail induced insufficient maturation of DCs derived from elutriated monocytes when cultured in X-VIVO 15. The aim of this study was to define effective combinations of stimulators for generating functionally mature DCs from elutriated monocytes under current good manufacturing practice conditions. We compared the functional capacity of DCs in response to all possible pairwise combinations of four different classes of stimuli: TNF-alpha, peptidoglycan, polyinosinic : polycytidylic acid [poly(I:C)] and soluble CD40 ligand (CD40L). Maturation status of DCs stimulated with combination of four stimuli was similar to that of the cytokine cocktail as assessed by the cell surface phenotype. However, only the combination of poly(I:C) + CD40L induced complete functional activation of the whole DC population, assessing IL-12p70 production, allostimulatory activity, migratory response to CCL19 and T helper 1-polarizing capacity. Thus, the protocol based on the combination of poly(I:C) and CD40L is more effective for the induction of clinical-grade DCs from elutriated monocytes than the standard cytokine cocktail.

CD83 regulates lymphocyte maturation, activation and homeostasis

The transmembrane CD83 molecule, a conserved member of the immunoglobulin superfamily, is known as one of the most characteristic cell surface markers for fully matured dendritic cells (DCs) in the peripheral circulation. An essential role for CD83 on murine DCs has not been found; however, evidence shows that its function primarily lies in the regulation of T- and B-lymphocyte maturation and in the regulation of their peripheral responses. Here, we review evidence for a role of CD83 in central lymphocyte maturation and novel, sometimes contradictory findings, regarding the function of CD83 in peripheral immune responses.