Modulate Dendritic Cells Maturation Research Articles

Human Dendritic Cell Maturation Is Modulated by Leishmania mexicana through Akt Signaling Pathway.

Dendritic cells (DC) along with macrophages are the main host cells of the intracellular parasite Leishmania. DC traverse a process of maturation, passing through an immature state with phagocytic ability to a mature one where they can modulate the immune response through the secretion of cytokines. Several studies have demonstrated that Leishmania inhibits DC maturation. Nevertheless, when cells are subjected to a second stimulus such as LPS/IFN-γ, they manage to mature. In the maturation process of DC, several signaling pathways have been implicated, importantly MAPK. On the other hand, Akt is a signaling pathway deeply involved in cell survival. Some Leishmania species have shown to activate MAPK and Akt in different cells. The aim of this work was to investigate the role of ERK and Akt in the maturation of monocyte-derived DC (moDC) infected with L. mexicana. moDC were infected with L. mexicana metacyclic promastigotes, and the phosphorylation of ERK and Akt, the expression of MHCII and CD86 and IL-12 transcript, and secretion were determined in the presence or absence of an Akt inhibitor. We showed that L. mexicana induces a sustained Akt and ERK phosphorylation, while the Akt inhibitor inhibits it. Moreover, the infection of moDC downregulates CD86 expression but not MHCII, and the Akt inhibitor reestablishes CD86 expression and 12p40 production. Thus, L. mexicana can modulate DC maturation though Akt signaling.

Mannose-Binding Lectin Reduces Oxidized Low-Density Lipoprotein Induced Vascular Endothelial Cells Injury by Inhibiting LOX1-ox-LDL Binding and Modulating Autophagy.

Objective: To investigate the role of mannose-binding lectin (MBL) in modulating autophagy and protecting endothelial cells (ECs) from oxidized low-density lipoprotein (ox-LDL)-induced injury. Methods: Serum MBL concentration and carotid intima-media thickness (cIMT) were measured in 94 obese and 105 healthy children. ECs were transfected with MBL over-expression plasmid, LOX1 was knocked-down to explore the protective role of MBL in ox-LDL induced ECs injury. Dendritic cells (DCs) were co-cultured with ECs, and inflammatory factors, DC maturation, and autophagy was assessed. WT and ApoE-/- mice were fed with a high fat diet (HFD) with or without MBL-adenovirus injection for 16 weeks and aortic vascular endothelial tissue was isolated, then atherosclerotic plaque, cell injury and autophagy were analyzed. Results: Serum MBL concentration in obese children was lower than healthy controls and was negatively correlated with cIMT. The uptake of ox-LDL was decreased in LOX1 knock-down ECs. MBL over-expression in vitro inhibited LOX1-ox-LDL binding. Both LOX1 knock-down and MBL over-expression can ameliorate EC autophagy and cell injury. MBL over-expression in vivo alleviated atherosclerotic plaque formation, influenced DC maturation and down-regulated IL-6, IL-12, and TNF-a levels. Conclusions: MBL exerts a protective role in ox-LDL-induced EC injury by modulating DC maturation and EC autophagy via inhibiting LOX1-ox-LDL binding.

Control of Dendritic Cell Function Within the Tumour Microenvironment.

The tumour microenvironment (TME) presents a major block to anti-tumour immune responses and to effective cancer immunotherapy. The inflammatory mediators such as cytokines, chemokines, growth factors and prostaglandins generated in the TME alter the phenotype and function of dendritic cells (DCs) that are critical for a successful adaptive immune response against the growing tumour. In this mini review we discuss how tumour cells and the surrounding stroma modulate DC maturation and trafficking to impact T cell function. Fibroblastic stroma and the associated extracellular matrix around tumours can also provide physical restrictions to infiltrating DCs and other leukocytes. We discuss interactions between the inflammatory TME and infiltrating immune cell function, exploring how the inflammatory TME affects generation of T cell-driven anti-tumour immunity. We discuss the open question of the relative importance of antigen-presentation site; locally within the TME versus tumour-draining lymph nodes. Addressing these questions will potentially increase immune surveillance and enhance anti-tumour immunity.

The suppression effect of dendritic cells maturation by adipose-derived stem cells through TGF-β1 related pathway

BackgroundOur previous studies demonstrated that adipose-derived stem cells (ASCs) could modulate regulatory T cells (Treg) and prolong hind-limb allotransplant survival in vitro and in vivo. Dendritic cells (DCs) play a pivotal role in innate and adaptive immunity. The aim of this study is to investigate the underlying mechanism of ASCs in modulating DC maturation. Materials and MethodsASCs were isolated from rodent adipose tissue, DCs were derived from the bone marrow, and CD4+ T cells were purified from splenocytes. DCs were co-cultured with ASCs to evaluate the suppressive effects of ASCs. CD4+ T-cells were co-cultured with DCs pre-treated with or without ASCs. The cell surface markers of DCs were analyzed by flow cytometry. T-cell proliferation was analyzed by the BrdU proliferation test. Tolerogenic cytokines and indoleamine 2,3-dioxygenase (IDO) expressions after different treatments were detected by quantitative real-time PCR, Western blotting, and ELISA analysis. ResultASCs suppressed DC maturation as evidenced by low expressions of CD80, CD86, and MHC-II. Also, ASC-treated mature DCs showed higher levels of TGF-β1, IL-10, and IDO expressions, as compared to that in matured DCs (mDCs) alone. ASC-treated mDCs co-cultured with CD4+ T cells revealed a significant higher percentage of Treg than mDC without treatment. The IDO level in ASC-treated mDCs and Treg induction effects were blocked by the ASCs pre-treated with TGF-β1 siRNAs, but not IL-10 siRNAs. ConclusionASC-modulated DC maturation correlated with TGF-β1 secretion, IDO expression, and Treg induction. ASCs could be used as a potential immunomodulatory strategy for clinical application in allotransplantation.

Lactobacillus rhamnosus GG-Derived Soluble Mediators Modulate Adaptive Immune Cells.

Probiotics and probiotic-related nutritional interventions have been described to have beneficial effects on immune homeostasis and gut health. In previous studies, Lactobacillus rhamnosus GG (LGG) soluble mediators (LSM) have been demonstrated to exert beneficial effects in preclinical models of allergic sensitization, bacterial infection, and intestinal barrier function. In the context of allergic diseases, differentiation of dendritic cells (DCs) and their interactions with T cell populations are crucial for driving tolerogenic responses. In this study, we set out to evaluate whether these LSM can modulate DC maturation and have an impact on prompting protective and/or tolerogenic T cell responses. Monocytes were isolated from PBMC of healthy blood donors and cultured in the presence of GM-CSF, IL-4, and LSM or unconditioned bacterial culture medium control (UCM) during 6 days to induce DC differentiation. Subsequently, these DCs were matured in the presence of TNF-α for 1 day and analyzed for their phenotype and ability to induce autologous T cell activation and differentiation to model recall antigens. After 7 days of co-culture, T cells were analyzed for activation and differentiation by flow cytometry of intracellular cytokines (IFN-γ, IL-2, IL-10, and IL-17A), activation markers (CD25), and Foxp3+ expression. LSM did not alter DC numbers or maturation status. However, these DCs did show improved capacity to induce a T cell response as shown by increased IL-2 and IFN-γ producing T cell populations upon stimulation with recall antigens. These enhanced recall responses coincided with enhanced Foxp3+ expression that was not observed when T cells were cultured in the presence of UCM-treated DCs. By contrast, the number of activated T cells (determined by CD25 expression) was only slightly increased. In conclusion, this study reveals that LSM can influence adaptive immune responses as shown by the modulation of DC functionality. These mechanisms might contribute to previous observed effects in animal models in vivo. Altogether, these results suggest that LSM may provide an alternative to live probiotics in case life bacteria may not be used because of health conditions, although further clinical testing is needed.

Myeloid deletion of SIRT1 suppresses collagen-induced arthritis in mice by modulating dendritic cell maturation.

The type III histone deacetylase silent information regulator 1 (SIRT1) is an enzyme that is critical for the modulation of immune and inflammatory responses. However, the data on its role in rheumatoid arthritis (RA) are limited and controversial. To better understand how SIRT1 regulates adaptive immune responses in RA, we evaluated collagen-induced arthritis (CIA) in myeloid cell-specific SIRT1 knockout (mSIRT1 KO) and wild-type (WT) mice. Arthritis severity was gauged on the basis of clinical, radiographic and pathologic scores. Compared with their WT counterparts, the mSIRT1 KO mice exhibited less severe arthritis, which was less destructive to the joints. The expression levels of inflammatory cytokines, matrix metalloproteinases and ROR-γT were also reduced in the mSIRT1 KO mice compared with the WT mice and were paralleled by reductions in the numbers of Th1 and Th17 cells and CD80- or CD86-positive dendritic cells (DCs). In addition, impaired DC maturation and decreases in the Th1/Th17 immune response were observed in the mSIRT1 KO mice. T-cell proliferation was also investigated in co-cultures with antigen-pulsed DCs. In the co-cultures, the DCs from the mSIRT1 KO mice showed decreases in T-cell proliferation and the Th1/Th17 immune response. In this study, myeloid cell-specific deletion of SIRT1 appeared to suppress CIA by modulating DC maturation. Thus, a careful investigation of DC-specific SIRT1 downregulation is needed to gauge the therapeutic utility of agents targeting SIRT1 in RA.

Bacillus amyloliquefaciens SQR9 induces dendritic cell maturation and enhances the immune response against inactivated avian influenza virus

The objective of this study was to evaluate the stimulatory effects of Bacillus amyloliquefaciens SQR9 on dendritic cells (DCs) and to verify its ability to enhance the immune response by modulating DC maturation. The results demonstrated that B. amyloliquefaciens SQR9 can adhere to the nasal epithelium and be taken up by DCs in the nasal mucosa, thereby inducing DC maturation and resulting in increased CD80, CD86, CD40 and MHCII expression and cytokine secretion. The frequencies of CD4+ and CD8+ T cells and CD69+ memory T cells were increased in spleens after nasal immunization with virus plus B. amyloliquefaciens SQR9 compared to immunization with inactivated H9N2 AIV alone. Moreover, the levels of sIgA in the nasal cavity, the trachea, and the lung and the levels of IgG, IgG1, and IgG2a in serum were significantly increased in mice administered WIV plus SQR9 compared to mice administered H9N2 WIV alone. The results of this study demonstrated that B. amyloliquefaciens SQR9 can stimulate DC maturation to effectively induce an immune response. In conclusion, an effective immune response may result from the uptake of H9N2 by DCs in the nasal mucosa, thereby stimulating DC maturation and migration to cervical lymph nodes to initiate immune response.

Gut bacteria modulation of antigen presenting cells in a mouse model of autoimmune diabetes. (THER5P.915)

Abstract T1D is an autoimmune disease whereby the beta cells of the pancreas are destroyed, resulting in the inability to self-regulate blood glucose. While genetics play a role, the contribution of environmental factors such as gut bacteria have also been implicated. Notably, it was shown that the oral administration of L. johnsonii N6.2 (LjN6.2) conveyed diabetes resistance to diabetes prone rodents while a second strain, Lactobacillus reuteri TD1, had no effect. However, the exact mechanisms of microbiota action on diabetes prevention remain poorly understood. As it has been shown that defective antigen presentation by dendritic cells (DC) contributes to T1D progression, we tested the hypothesis that gut flora can serve to modulate DC maturation. We observed that the administration of LjN6.2 to NOD leukocytes in vitro mediated increases in CD11c+MHCII+ DC. Moreover, LjN6.2 facilitated enhanced myeloid dendritic cell maturation denoted by the increase in number of CD8alo DEC205lo that were comparable to levels present in NOR mice. In addition, LjN6.2 also increased IL6 production. This study highlights the role of gut bacteria in autoimmunity as a critical component for T1D therapeutic strategies and might be used to extrapolate treatment approaches in humans in the future.

THU0471 Myeloid Deletion of SIRT1 Suppresses Collagen-Induced Arthritis in Mice by Modulating Dendritic Cell Function

ObjectivesThe type III histone deacetylase SIRT1 is a critical molecule in the modulation of immune and inflammatory response through the deacetylation of various histones and non-histone proteins. However, there are...

Homeobox Transcription Factor VentX Regulates Differentiation and Maturation of Human Dendritic Cells

Dendritic cells (DCs) are specialized antigen presentation cells that play critical roles in the initiation and regulation of immune responses. The molecular determinants of DC differentiation and maturation are target of extensive investigation. VentX is a human homeobox transcriptional factor that regulates proliferation and differentiation of hematopoietic cells. In the current study, we report that ablation of VentX expression in monocytes significantly impaired their differentiation into DCs. Conversely, overexpression of VentX in monocytic THP1 cells accelerated their differentiation toward DCs. We showed that VentX regulates DC differentiation, in part, through modulating IL6 expression. Clinically, we found that VentX expression was elevated in intestinal lamina propria DCs (LPDCs) of inflamed mucosa from inflammatory bowel disease patients. Knockdown experiments suggested that VentX is essential for the maturation of LPDCs. In addition, corticosteroid treatment markedly decreased VentX expression in LPDCs and enforced expression of VentX counteracted the effects of corticosteroid on DCs maturation. Our data suggest that VentX is a critical transcriptional regulator of DC differentiation and maturation, and a potential target of immune regulation and therapy.

Alterations of costimulatory molecules and instructive cytokines expressed by dendritic cells in the microenvironment of an endogenous mouse lymphoma.

Costimulatory surface molecules and instructive cytokines expressed by dendritic cells (DCs) determine the outcome of an immune response. In malignant disease, DCs are often functionally compromised. In most tumors studied so far, the deficient induction of effective T cell responses has been associated with a blockade of DC maturation, but little has been known on DCs infiltrating malignant B cell lymphoma. Here, we investigated for the first time the phenotypic and functional status of DCs in B cell lymphoma, and we analyzed the network of DCs, tumor cells, natural killer (NK) cells and cytokines present in the tumor micromilieu. Therefor, we used an endogenous myc-transgenic mouse lymphoma model, because transplanted tumor cells foster an IFN-γ-driven Th1 antitumor response rather than an immunosuppressive environment, which is observed in autochthonous neoplasias. Lymphoma-infiltrating DCs showed a mature phenotype and a Th2-inducing cytokine pattern. This situation is in contrast to most human malignancies and mouse models described. Cellular contacts between DCs and tumor cells, which involved CD62L on the lymphoma, caused upregulation of costimulatory molecules, whereas IL-10 primarily derived from lymphoma cells induced an IL-12/IL-10 shift in DCs. Thus, alteration of costimulatory molecules and instructive cytokines was mediated by distinct mechanisms. Normal NK cells were able to additionally modulate DC maturation but this effect was absent in the lymphoma environment where IFN-γ production by NK cells was severely impaired. These data are relevant for establishing novel immunotherapeutic approaches against B cell lymphoma.

Direct Type I IFN but Not MDA5/TLR3 Activation of Dendritic Cells Is Required for Maturation and Metabolic Shift to Glycolysis after Poly IC Stimulation

Author SummaryImmune responses are orchestrated by a specialized cell type called dendritic cells (DCs). In order to achieve durable and robust immunity, DCs need to undergo an intricate differentiation process known as maturation. This process is poorly understood at the moment. Poly IC, which mimics viral RNA and is an agonist for the viral pattern recognition receptors (PRRs) that signal “danger” to the immune system, can induce full maturation of DCs and it has been shown that this requires type I IFN signaling. In this study we set out to examine the specific signals provided by direct PRR or IFN stimulation that are required for DC maturation. We found to our surprise that type I IFN can regulate almost all steps of the DC's maturation process without requiring direct PRR involvement. We also show that type I IFN regulates several metabolic switches essential for preservation of DC integrity: it stimulates the expression of the hypoxia-inducible factor 1α (Hif1α), which controls the metabolic shift from oxidative phosphorylation (used by resting cells to generate energy) to aerobic glycolysis, a less efficient but faster energy-producing process. This metabolic shift was required to meet increased energy demands of activated DCs and to prevent their premature death, thus sustaining an immune response to viral infection.

The Lack of Maturation of Ebola Virus-Infected Dendritic Cells Results from the Cooperative Effect of at Least Two Viral Domains

Ebola virus (EBOV) infections are characterized by deficient T lymphocyte responses, T lymphocyte apoptosis, and lymphopenia in the absence of direct infection of T lymphocytes. In contrast, dendritic cells (DC) are infected but fail to mature appropriately, thereby impairing the T cell response. We investigated the contributions of EBOV proteins in modulating DC maturation by generating recombinant viruses expressing enhanced green fluorescent protein and carrying mutations affecting several potentially immunomodulating domains. They included envelope glycoprotein (GP) domains, as well as innate response antagonist domains (IRADs) previously identified in the VP24 and VP35 proteins. GP expressed by an unrelated vector, but not the wild-type EBOV, was found to strongly induce DC maturation, and infections with recombinant EBOV carrying mutations disabling GP functional domains did not restore DC maturation. In contrast, each of the viruses carrying mutations disabling any IRAD in VP35 induced a dramatic upregulation of DC maturation markers. This was dependent on infection, but not interaction with GP. Disabling of IRADs also resulted in up to a several hundredfold increase in secretion of cytokines and chemokines. Furthermore, these mutations induced formation of homotypic DC clusters, which represent close correlates of their maturation and presumably facilitate transfer of antigen from migratory DC to lymph node DC. Thus, an individual IRAD is insufficient to suppress DC maturation; rather, the suppression of DC maturation and the "immune paralysis" observed during EBOV infections results from a cooperative effect of two or more individual IRADs.

β-catenin regulates innate and adaptive immunity in mouse liver ischemia-reperfusion injury

Dendritic cells (DCs) are critical mediators of immune responses that integrate signals from the innate immune system to orchestrate adaptive host immunity. This study was designed to investigate the role and molecular mechanisms of STAT3-induced β-catenin in the regulation of DC function and inflammatory responses in vitro and in vivo. STAT3 induction in lipopolysaccharide (LPS)-stimulated mouse bone marrow-derived DCs (BMDCs) triggered β-catenin activation by way of GSK-3β phosphorylation. The activation of β-catenin inhibited phosphatase and tensin homolog delete on chromosome 10 (PTEN) and promoted the phosphoinositide 3-kinase (PI3K)/Akt pathway, which in turn down-regulated DC maturation and function. In contrast, knockdown of β-catenin increased PTEN/TLR4 (Toll-like receptor 4), interferon regulatory factor-3 (IRF3), nuclear factor kappa B (NF-κB) activity, and proinflammatory cytokine programs in response to LPS stimulation. In a mouse model of warm liver ischemia and reperfusion injury (IRI), disruption of β-catenin signaling increased the hepatocellular damage, enhanced hepatic DC maturation/function, and PTEN/TLR4 local inflammation in vivo. These findings underscore the role of β-catenin to modulate DC maturation and function at the innate-adaptive interface. Activation of β-catenin triggered PI3K/Akt, which in turn inhibited TLR4-driven inflammatory response in a negative feedback regulatory mechanism. By identifying the molecular pathways by which β-catenin regulates DC function, our findings provide the rationale for novel therapeutic approaches to manage local inflammation and injury in IR-stressed liver.

Salmonella enterica Serovar Typhi Plasmid Impairs Dendritic Cell Responses to Infection

Salmonella enterica serovar Typhi (S. typhi) evades from innate immunity by expression of a variety of pathogenic factors. The "pR(ST98)" plasmid of S. typhi is involved in multidrug-resistant and virulence of S. typhi. However, its exact effect on host cell function remains elusive. Dendritic cells (DCs) play an important role in shaping immune response against Salmonella. For the purpose of investigation whether pR(ST98) might target DCs involved in adaptive immune response, murine DCs were infected with S. typhi wild type and mutant strains. S. typhi stimulation resulted in up-regulation of costimulatory molecules on DCs. S. typhi wild type resulted in decreased up-regulation of CD40, CD80, and CD86 expression. Experiments with S. typhi pR(ST98) mutant (S. typhi-Δ-pR(ST98)) and S. typhi-Δ-pR(ST98) with a complemented plasmid encoding pR(ST98) (S. typhi-c-pR(ST98)) revealed that pR(ST98) accounts for inhibition of surface molecule expression and functional maturity. S. typhi-Δ-pR(ST98) gave maximal levels of IL-12 and IFN-γ release compared with wild type S. typhi or the complemented strains. In contrast to IL-12 and IFN-γ, IL-10 secretion by S. typhi-Δ-pR(ST98)-infected DCs was significantly lower than induction by S. typhi wild type. This indicates that immunity in response to pR(ST98) is skewed away from a protective Th1 response. Moreover, infection with S. typhi-Δ-pR(ST98) induced autophagy in DCs. We herein demonstrate S. typhi pR(ST98) plays essential roles in modulating DCs maturation, activation, inflammatory responses, and autophagy. Together, these data prove that pR(ST98) targets functions of DCs that are required for T-cell activation. This might contribute to evasion of adaptive immune responses by S. typhi.

Human group X secreted phospholipase A2 induces dendritic cell maturation through lipoprotein-dependent and -independent mechanisms

ObjectiveIncreased secreted phospholipase A2 (sPLA2) activity has been documented in several inflammatory disorders. Among sPLA2s, the human group X (hGX)-sPLA2 has the highest catalytic activity towards phosphatidylcholine (PC), the major phospholipid of cell membranes and blood lipoproteins. hGX-sPLA2 has been detected in human atherosclerotic lesions, indicating that sPLA2s are an important link between lipids and inflammation, both involved in atherosclerosis. The presence of dendritic cells (DC), the most potent antigen presenting cells, in atherosclerotic lesions has raised the question about their role in disease progression. Methods and resultsIn this study, we show that hGX-sPLA2-treated LDL induces human monocyte-derived DC maturation, resulting in a characteristic mature DC phenotype and enhanced DC ability to activate IFNγ secretion from T cells. hGX-sPLA2 phospholipolysis of LDL produces high levels of lipid mediators, such as lysophosphatidylcholine (LPC) and free fatty acids (FFAs), which also modulate DC maturation. The major molecular species of LPC containing a palmitic or stearic acid esterified in the sn-1 position induce DC maturation, whereas the FFAs can positively or negatively modulate DC maturation depending on their nature. hGX-sPLA2 added alone can also activate DC in vitro through the hydrolysis of the DC membrane phospholipids leading, however, to a different cytokine profile secretion pattern than the one observed with hGX-sPLA2-phospholipolysed LDL. ConclusionhGX-sPLA2 secreted in inflamed tissues can contribute to local DC maturation, resulting in pro-Th1 cells, through the production of various lipid mediators from hydrolysis of either LDL and/or cell plasma membrane.

Downregulation of CD40 Signal and Induction of TGF-β by Phosphatidylinositol Mediates Reduction in Immunogenicity Against Recombinant Human Factor VIII

Factor VIII (FVIII) is an important coagulation cofactor and its deficiency causes Hemophilia A, a bleeding disorder. Replacement therapy using recombinant FVIII is currently the first line of therapy for Hemophilia A, but the development of neutralizing antibody is a major clinical complication for this therapy. Recently, it has been shown that FVIII associated with phosphatidylinositol (PI)-containing lipidic nanoparticles reduced development of neutralizing antibodies in Hemophilia A mice (Peng A, Straubinger RM, Balu-Iyer SV. 2010. AAPS J 12(3):473-481). Here, we investigated the underlying mechanism of this reduction in antibody response in culturing conditions. In vitro, PI interfered with the processing of FVIII by cultured dendritic cells (DC), resulting in a reduction in the upregulation of phenotypic costimulatory signal CD40. Furthermore, PI increased secretion of regulatory cytokines Transforming Growth Factor β1 and Interleukin 10 (IL-10) but reduced the secretion of proinflammatory cytokines IL-6 and IL-17. The data suggest that PI reduces immunogenicity of FVIII by modulating DC maturation and inducing secretion of regulatory cytokines.

PE_PGRS Antigens ofMycobacterium tuberculosisInduce Maturation and Activation of Human Dendritic Cells

Mycobacterium tuberculosis, the causative agent of pulmonary tuberculosis, infects one-third of the world's population. Activation of host immune responses for containment of mycobacterial infections involves participation of innate immune cells, such as dendritic cells (DCs). DCs are sentinels of the immune system and are important for eliciting both primary and secondary immune responses to pathogens. In this context, to understand the molecular pathogenesis of tuberculosis and host response to mycobacteria and to conceive prospective vaccine candidates, it is important to understand how cell wall Ags of M. tuberculosis and, in particular, the proline-glutamic acid_polymorphic guanine-cytosine-rich sequence (PE_PGRS) family of proteins modulate DC maturation and function. In this study, we demonstrate that two cell wall-associated/secretory PE_PGRS proteins, PE_PGRS 17 (Rv0978c) and PE_PGRS 11 (Rv0754), recognize TLR2, induce maturation and activation of human DCs, and enhance the ability of DCs to stimulate CD4(+) T cells. We further found that PE_PGRS protein-mediated activation of DCs involves participation of ERK1/2, p38 MAPK, and NF-kappaB signaling pathways. Priming of human DCs with IFN-gamma further augmented PE_PGRS 17 or PE_PGRS 11 Ag-induced DC maturation and secretion of key proinflammatory cytokines. Our results suggest that by activating DCs, PE_PGRS proteins, important mycobacterial cell wall Ags, could potentially contribute in the initiation of innate immune responses during tuberculosis infection and hence regulate the clinical course of tuberculosis.

Induction of regulatory dendritic cells by topical application of NF-κB decoy oligodeoxynucleotides

Dendritic cells (DC) have a key role in inducing an immune response, but DC in different maturation states are responsible for inducing tolerance. Topical application of nuclear factor (NF)-κB decoy oligodeoxynucleotides (ODN) induces antigen-specific peripheral tolerance in delayed-type hypersensitivity (DTH) to ovalbumin (OVA) by expanding CD4 +CD25 + regulatory T cells and by inhibiting DC migration. Herein we describe how topical NF-κB decoy ODN modulate DC maturation with respect to their migration, phenotype, and cytokine profiles. Topical application of NF-κB decoy ODN after OVA sensitization delayed the migration of Langerhans cells (LC) into draining lymph nodes, and morphologically mature LC remained in the peripheral tissue 2 days longer than in OVA-sensitized mice without application of NF-κB decoy ODN. During migration, NF-κB decoy-treated DC preferentially expressed inhibitory B7 molecules (i.e., B7-H1, B7-DC, and B7-H3) compared to OVA-sensitized DC without NF-κB decoy ODN, whereas co-stimulatory molecules (MHC class II, B7-1 and B7-2) were upregulated. Adoptive transfer of NF-κB decoy-treated DC inhibited DTH induction in prophylactic and therapeutic experiments. Inhibition of DTH by DC transfer was antigen-specific in vivo. This decoy ODN strategy might be useful for regulating immunity through DC.

The maturation of murine bone marrow-derived dendritic cells by tumor lysate uptake in vitro is not essential for cancer immunotherapy

Immunization of dendritic cells (DC) pulsed with tumor antigen can activate tumor-specific cytotoxic T lymphocytes (CTL) which are responsible for protection from tumor challenge and regression of established metastatic tumor. It has been hypothesized that tumor lysate contains factors that may modulate DC maturation. In this study, we examined whether the uptake of tumor lysate (MCA-102 fibrosarcoma) could modulate DC phenotypes in vitro and whether the administration in vivo of tumor lysate-pulsed DC (TP-DC) could elicit efficient tumor specific immune responses followed by a regression of established tumor burdens. It was investigated the uptake of tumor lysate by DC by means of flow cytometry and fluorescent microscope. Murine bone marrow-derived DC efficiently phagocytosed tumor lysate and after the uptake, the phenotype of TP-DC was surprisingly comparable to unpulsed-DC (UP-DC), exhibiting lower levels of CD80 (< 51%), CD86 (< 43 %), and MHC class II (< 59%). Also, TP-DC did not enhance secretion of IL-12p70 (UP- vs. TP; 54.5 ± 6.4 vs. 50.5 ± 4.8 pg/ml, respectively), contrary to those activated with LPS (113.6 ± 16.8 pg/ml). However, TP-DC vaccination in vivo increased the IFN-? production from splenocytes higher than that of UP-DC (TP- vs. UP-DC; 41029 ± 1523 vs. 4752 ± 590 pg/ml, respectively). Furthermore, the administration of TP-DC enhanced specific T cell responses against MCA-102 fibrosarcoma. These results demonstrate that augmentation of DC phenotype and function in vitro is not necessarily a prerequisite for TP-DC vaccination to successfully promote anti-tumor immunity in vivo.