Function Of Immature Dendritic Cells Research Articles

Effect of Selenium and Peroxynitrite on Immune Function of Immature Dendritic Cells in Humans.

BackgroundSelenium and peroxynitrite are known to support the growth and activity of immune cells, including T cells, B cells and macrophages. However, the role of these factors in the immune function of human immature dendritic cells (imDCs) is not clear.Material/MethodsMonocytes from a mixture of blood samples were isolated using Ficoll density gradient centrifugation and purified with immunomagnetic beads before being induced into imDCs. Cells then either received no treatment (control group), or treatment with sodium selenite (Na2SeO3, Se), 3-morpholinosydnonimine (SIN1, which decomposes into peroxynitrite), or Se+SIN1. Cell viability, migration, and antiphagocytic abilities, oxidative stress, and protein expression of extracellular signal-regulated kinases (ERK) and MMP2 were assessed using a CCK8 assay, cell counter and flow cytometry, microplate spectrophotometer, and Western blot analysis, respectively.ResultsViability of imDCs was unaffected by 0.1 μmol/L of Na2SeO3, although 1 mmol/L of SIN1 decreased it significantly (P<0.05). Chemotactic migration and antiphagocytic abilities were inhibited and enhanced, respectively, by treatment with Na2SeO3 and SIN1 (P<0.05). Activities of superoxide dismutase and glutathione peroxidase were increased by Na2SeO3 and Se+SIN1 (P<0.001). Glutathione content decreased with exposure to Na2SeO3 and SIN1 (P<0.05), but increased after treatment with Se+SIN1 (P<0.05). Levels of reactive oxygen species only increased with SIN1 treatment (P<0.05). Treatment with Na2SeO3, SIN1 and Se+SIN1 increased ERK phosphorylation and decreased MMP2 protein expression (P<0.05).ConclusionsSelenium and peroxynitrite can influence immune function in imDCs by regulating levels of reactive oxygen species or glutathione to activate ERK and promote antigen phagocytosis, as well as by decreasing MMP2 expression to inhibit chemotactic migration.

Induction of antigen-specific immune tolerance using biodegradable nanoparticles containing antigen and dexamethasone.

PurposeDexamethasone (Dex) has long been used as a potent immunosuppressive agent in the treatment of inflammatory and autoimmune diseases, despite serious side effects. In the present study, Dex and model antigen ovalbumin (OVA) were encapsulated with poly(lactic-co-glycolic acid) to deliver Dex and OVA preferentially to phagocytic cells, reducing systemic side effects of Dex. The OVA-specific immune tolerance-inducing activity of the nanoparticles (NPs) was examined.MethodsPolymeric NPs containing OVA and Dex (NP[OVA+Dex]) were prepared by the water-in-oil-in-water double emulsion solvent evaporation method. The effects of NP[OVA+Dex] on the maturation and function of immature dendritic cells (DCs) were examined in vitro. Furthermore, the OVA-specific immune tolerizing effects of NP[OVA+Dex] were confirmed in mice that were intravenously injected or orally fed with the NPs.ResultsImmature DCs treated in vitro with NP[OVA+Dex] did not mature into immunogenic DCs but instead were converted into tolerogenic DCs. Furthermore, profoundly suppressed generation of OVA-specific cytotoxic T cells and production of OVA-specific IgG were observed in mice injected with NP[OVA+Dex], whereas regulatory T cells were concomitantly increased. Feeding of mice with NP[OVA+Dex] also induced OVA-specific immune tolerance.ConclusionThe present study demonstrates that oral feeding as well as intravenous injection of poly(lactic-co-glycolic acid) NPs encapsulating both antigen and Dex is a useful means of inducing antigen-specific immune tolerance, which is crucial for the treatment of autoimmune diseases.

Cotransfection with IL-10 and TGF-β1 into immature dendritic cells enhances immune tolerance in a rat liver transplantation model

Dendritic cells transfected with interleukin (IL)-10 and transforming growth factor-β1 (TGF-β1) enhance T cell immunity and tolerance. However, no quantitative studies have investigated the suppressive functions of immature dendritic cells (imDC) cotransfected with IL-10 and TGF-β1. The effects of imDC cotransfected with IL-10 and TGF-β1 (IL-10-TGF-β1-imDC) on immune tolerance induction in a rat transplantation model were investigated. In addition, effects of IL-10-TGF-β1-imDC relative to IL-10-transfected imDC (IL-10-imDC) and TGF-β1-transfected imDC (TGF-β1-imDC) were compared. The infusion of IL-10-TGF-β1-imDC into recipients prolonged liver graft survival, which was sustained for >90 days. IL-12 serum levels decreased, whereas alanine transaminase and total bilirubin slightly increased in rats infused with IL-10-TGF-β1-imDC compared with the IL-10-imDC and TGF-β1-imDC groups. Furthermore, a higher percentage of terminal transferase-mediated UTP nick end-labeling-positive cells was observed, and histological analysis of the allografts indicated a rejection activity index of mild acute rejection. Our results suggest infusion of IL-10 and TGF-β1 cotransfected imDC induces alloantigen-specific T cell hyporesponsiveness, inhibits antigen-specific immunological responses to liver allografts, prolongs liver allograft survival, and enhances the immune tolerance. This approach may provide a promising alternative for enhancing donor-specific tolerance during liver transplantation.

Immune function of immature dendritic cells modified with transforming growth factor-β1

Objective To assess the biological functions of transforming growth factor-β1 (TGF-β1 ) in rat bone marrow-derived dendritic cells (DCs).Methods In the in vitro study,rat bone marrowderived imature dendritic cells (imDCs) and mature DCS (mDCs) were obtained after primary culture of bone marrow cells in RPMI 1640 medium with different cytokines.We used imDCs transfected with plasmid vectors encoding TGF-β1,imDCs transfected with plasmid vectors encoding enhanced GFP ( eGFP),untransfected imDCs,and un-transfected mDCs.The latter three kinds of imDCS were used as controls.CD86,CD80,and MHC class Ⅱ were compared by using flow cytometry and immuocytochemistry,and T lymphocyte proliferation was observed under mixed lymphocyte reaction.The biological functions of TGF-β1were assessed in rat bone marrow-derived DCs between two groups.Results The expression of TGF-β1 in imDCs transfected with TGF-β1 genes was (252.75 ± 11.31 ) μg/L,which was higher than in imDC group (35.18 ±6.17) μg/L,vector only imDC group (33.67 ±4.61 ) μg/L and mDC group ( 11.19 ±2.29)μg/L.The expression of MHC class Ⅱ,CD80 and CD86 in imDCs transfected with TGF-β1 genes was lower than the other three groups.These results suggest that the expression of MHC class Ⅱ,CD80 and CD86 can be significantly down-regulated,especially in imDCs transfected with TGF-β1.Strong allergenic T lymphocytes proliferation was induced in mDCs,and imDCs transfected with TGF-β1gene showed lower capability in stimulating T lymphocyte proliferation than the other groups.Conclusion The present study demonstrated that TGF-β1 gene can be successfully transferred to imDCs through plasmid vectors.The use of plasmid vectors encoding TGF-β1 gene can inhibit multiple immunological functions of imDCs and enhance their tolerogenicity. Key words: Dendritic cells; Immue tolerance; TGF-β1 ; Gene transfection

The immunogenicity of dendritic cell-derived exosomes

Exosome production represents an alternate endocytic pathway for secretion. Multivesicular endosomes (MVE) fuse with the plasma membrane expelling internal vesicles or exosomes from cells. Exosome production has been recently described for immune cells including B cells, dendritic cells (DC), mast cells, macrophages and T cells. Exosomes derived from some DC populations stimulate T lymphocyte proliferation in vitro and have potent capacity to generate anti-tumour immune responses in vivo. These reported studies have involved in vitro grown mature DC expanded from precursors with cytokines. However, immature DC produce higher numbers of exosomes than mature DC and this is thought to be due to a reduction in endocytosis as DC mature, associated with reduced reformation of MVE and reduced exosome formation. This lab pioneered a method to generate immature DC in spleen long-term cultures (LTC). DC produced in cultures represent immature myeloid DC, highly endocytic but with weak capacity to stimulate T cells. LTC-DC produce exosomes and contain many MVE. This prompted a study of immunogenic potential with a view to the potential use of exosomes in vaccination and immunotherapy. DC produced in cultures represent immature myeloid DC, highly endocytic but with weak capacity to stimulate T cells. Exosomes were isolated by differential centrifugation from LTC-DC and shown by marker expression to arise by budding from the LAMP-1 + limiting endosomal membrane of MVE. These LTC-derived exosomes appear however to lack immunostimulatory markers like CD86, CD40, MHC-I and MHC-II. While LTC-DC can stimulate antigen-specific proliferation of CD4 + T cells, exosome preparations derived from antigen-pulsed DC were unable to stimulate purified naïve T cells in vitro. They were however found to weakly activate allogeneic CD8 + T cells in vitro. Tumour antigen-pulsed LTC-DC or their exosomes could induce a protective response in mice against growth of a transplanted tumour but could not induce a response to clear an existing tumour. Exosomes derived from immature DC can modulate immune responses, but do not function in direct T cell activation in vitro. Modulation of immune responses by exosomes produced by immature DC may be dependent on the presence of other antigen presenting DC subsets in the animal. The possible function of immature DC and their exosomes in maintenance of tolerance and in the induction of immunity is discussed.

The Impact of Extracellular Acidosis on Dendritic Cell Function

Dendritic cells (DCs) are the most efficient antigen-presenting cells. They are activated in the periphery by conserved pathogen molecules and by inflammatory mediators produced by a variety of cell types in response to danger signals. It is widely appreciated that inflammatory responses in peripheral tissues are usually associated with the development of acidic microenvironments. Surprisingly, there are relatively few studies directed to analyze the effect of extracellular acidosis on the immune response. We focus on the influence of extracellular acidosis on the function of immature DCs. The results presented here show that acidosis activates DCs. It increases the acquisition of extracellular antigens for MHC class I-restricted presentation and the ability of antigen-pulsed DCs to induce both specific CD8+ CTL and B-cell responses. These findings may have important implications to our understanding of the mechanisms through which DCs sense the presence of infection or inflammation in nonlymphoid tissues.

Immature, but not inactive: the tolerogenic function of immature dendritic cells.

The induction of antigen-specific T cell tolerance and its maintenance in the periphery is critical for the prevention of autoimmunity. Recent evidence shows that dendritic cells (DC) not only initiate T cell responses, but are also involved in silencing of T cell immune responses. The functional activities of DC are mainly dependent on their state of activation and differentiation, that is, terminally differentiated mature DC can efficiently induce the development of T effector cells, whereas immature DC are involved in maintenance of peripheral tolerance. The means by which immature DC maintain peripheral tolerance are not entirely clear, however, their functions include the induction of anergic T cells, T cells with regulatory properties as well as the generation of T cells that secrete immunomodulatory cytokines. This review summarizes the current knowledge about the immunoregulatory role of immature DC that might act as guardians for the induction and maintenance of T cell tolerance in the periphery.