Cyclosporin A-treated Dendritic Cells may affect the outcome of organ transplantation by decreasing CD4+CD25+ regulatory T cell proliferation

http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602010000300010&lng=es&nrm=isoOne of the mechanisms for generation of tolerance involves immature dendritic cells (DCs) and a subpopulation of regulatory CD4+ CD25+ T lymphocytes (TREG). The purpose of this work was to analyze how Cyclosporine A (CsA), a widely used immunosuppressive drug, may affect TREG proliferation. Purified and activated murine DCs obtained from bone marrow precursors differentiated with rGMCSF were co-cultured with purified CFSE-labeled TREG from OTII mice, and their phenotype and proliferation analyzed by flow cytometry. Our data indicate that DCs differentiated in the presence of CsA show an altered phenotype, with a lower expression of MHC-II and a lower activating capacity. Additionally, these CsA-treated DCs show decreased production of IL-2 and IL-12 and increased IL-10 secretion when stimulated with LPS, indicating an effect on the polarization of the immune response. Interestingly, CsA-treated DCs show an anti-tolerogenic effect since they reduce the proliferation of TREG cells from 72 to 47%. Further inhibition to a 24% of TREG proliferation was obtained as a direct effect of CsA on TREG. In conclusion, the anti-tolerogenic effect of CsA should be considered in the planning of immunosuppression in the context of clinical transplantation

P2X7 receptor is essential for cross-dressing of bone marrow-derived dendritic cells

T cell activation requires the processing and presentation of antigenic peptides in the context of a major histocompatibility complex (MHC complex). Cross-dressing is a non-conventional antigen presentation mechanism, involving the transfer of preformed peptide/MHC complexes from whole cells, such as apoptotic cells (ACs) to the cell membrane of professional antigen-presenting cells (APCs), such as dendritic cells (DCs). This is an essential mechanism for the induction of immune response against viral antigens, tumors, and graft rejection, which until now has not been clarified. Here we show for first time that the P2X7 receptor (P2X7R) is crucial to induce cross-dressing between ACs and Bone-Marrow DCs (BMDCs). In controlled ex vivo assays, we found that the P2X7R in both ACs and BMDCs is required to induce membrane and fully functional peptide/MHC complex transfer to BMDCs. These findings show that acquisition of ACs-derived preformed antigen/MHC-I complexes by BMDCs requires P2X7R expression.Fil: Barrera Avalos, Carlos. Universidad de Santiago de Chile; ChileFil: Briceño, Pedro. Universidad de Chile; ChileFil: Valdés, Daniel. Universidad de Santiago de Chile; ChileFil: Imarai, Mónica. Universidad de Santiago de Chile; ChileFil: Leiva Salcedo, Elías. Universidad de Santiago de Chile; ChileFil: Rojo, Leonel E.. Universidad de Santiago de Chile; ChileFil: Milla, Luis A.. Universidad de Santiago de Chile; ChileFil: Huidobro Toro, Juan Pablo. Universidad de Santiago de Chile; ChileFil: Robles Planells, Claudia. Universidad de Santiago de Chile; ChileFil: Escobar, Alejandro. Universidad de Chile; ChileFil: Di Virgilio, Francesco. Università di Ferrara; ItaliaFil: Moron, Victor Gabriel. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Bioquímica Clínica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones en Bioquímica Clínica e Inmunología; ArgentinaFil: Sauma, Daniela. Universidad de Chile; ChileFil: Acuña Castillo, Claudio. Universidad de Santiago de Chile; Chil

IRE1α Activation in Bone Marrow-Derived Dendritic Cells Modulates Innate Recognition of Melanoma Cells and Favors CD8+ T Cell Priming

The IRE1α/XBP1s signaling pathway is an arm of the unfolded protein response (UPR) that safeguards the fidelity of the cellular proteome during endoplasmic reticulum (ER) stress, and that has also emerged as a key regulator of dendritic cell (DC) homeostasis. However, in the context of DC activation, the regulation of the IRE1α/XBP1s axis is not fully understood. In this work, we report that cell lysates generated from melanoma cell lines markedly induce XBP1s and certain members of the UPR such as the chaperone BiP in bone marrow derived DCs (BMDCs). Activation of IRE1α endonuclease upon innate recognition of melanoma cell lysates was required for amplification of proinflammatory cytokine production and was necessary for efficient cross-presentation of melanoma-associated antigens without modulating the MHC-II antigen presentation machinery. Altogether, this work provides evidence indicating that ex-vivo activation of the IRE1α/XBP1 pathway in BMDCs enhances CD8+ T cell specific responses against tumor antigens

Retinoic Acid as a Modulator of T Cell Immunity

Vitamin A, a generic designation for an array of organic molecules that includes retinal, retinol and retinoic acid, is an essential nutrient needed in a wide array of aspects including the proper functioning of the visual system, maintenance of cell function and differentiation, epithelial surface integrity, erythrocyte production, reproduction, and normal immune function. Vitamin A deficiency is one of the most common micronutrient deficiencies worldwide and is associated with defects in adaptive immunity. Reports from epidemiological studies, clinical trials and experimental studies have clearly demonstrated that vitamin A plays a central role in immunity and that its deficiency is the cause of broad immune alterations including decreased humoral and cellular responses, inadequate immune regulation, weak response to vaccines and poor lymphoid organ development. In this review, we will examine the role of vitamin A in immunity and focus on several aspects of T cell biology such as T helper cell differentiation, function and homing, as well as lymphoid organ development. Further, we will provide an overview of the effects of vitamin A deficiency in the adaptive immune responses and how retinoic acid, through its effect on T cells can fine-tune the balance between tolerance and immunity

Notch Signalling Regulates Cytokine Production by CD8+ and CD4+ T Cells

The Notch signalling pathway regulates several aspects of cellular differentiation such as T lineage commitment and effector functions on peripheral T cells; however, there is limited information regarding Notch receptor expression on different T cell subsets and the putative role of the different receptors on T cell effector function. Here, we studied the protein expression of Notch receptors on murine T cells in vitro and in vivo and analysed the role of the Notch pathway in cytokine production by CD4+ and CD8+ T cells. We found that resting CD4+ and CD8+ T cells do not express Notch receptors, but they upregulate Notch 1 and Notch 2 shortly after in vitro and in vivo activation. Using a γ-secretase inhibitor, which blocks Notch signalling through all Notch receptors, we demonstrated that the Notch pathway regulates IL-10 production by CD4+ T cells and IFN-γ and IL-17 production by CD8+ T cells. These results suggest that Notch 1 and 2 are expressed by CD4+ and CD8+ T cells and repr

Inhibition of InsP3R with Xestospongin B reduces mitochondrial respiration and induces selective cell death in T cell acute lymphoblastic leukemia cells

International audienceT-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy whose chemoresistance and relapse persist as a problem despite significant advances in its chemotherapeutic treatments. Mitochondrial metabolism has emerged as an interesting therapeutic target given its essential role in maintaining bioenergetic and metabolic homeostasis. T-ALL cells are characterized by high levels of mitochondrial respiration, making them suitable for this type of intervention. Mitochondrial function is sustained by a constitutive transfer of calcium from the endoplasmic reticulum to mitochondria through the inositol 1,4,5-trisphosphate receptor (InsP3R), making T-ALL cells vulnerable to its inhibition. Here, we determine the bioenergetic profile of the T-ALL cell lines CCRF-CEM and Jurkat and evaluate their sensitivity to InsP3R inhibition with the specific inhibitor, Xestospongin B (XeB). Our results show that T-ALL cell lines exhibit higher mitochondrial respiration than non-malignant cells, which is blunted by the inhibition of the InsP3R. Prolonged treatment with XeB causes T-ALL cell death without affecting the normal counterpart. Moreover, the combination of XeB and glucocorticoids significantly enhanced cell death in the CCRF-CEM cells. The inhibition of InsP3R with XeB rises as a potential therapeutic alternative for the treatment of T-ALL

Differential regulation of Notch ligands in dendritic cells upon interaction with T helper cells

The Notch signalling pathway has recently been linked to T helper 1 (Th1)/T helper 2 (Th2) cell polarization via a mechanism involving differential expression of Notch ligands, Delta-like and Jagged, in antigen-presenting cells. However, whether stimuli other than pathogen-derived factors are involved in the regulation of Notch ligand expression in dendritic cells (DCs) remains unknown. Here, we address the effect of T helper cells (Th1 and Th2) on Delta-like 4 and Jagged 2 expression in bone marrow-derived DCs. We demonstrate that both Th1 and Th2 cells induce Delta-like 4 mRNA expression in DCs, in a process that is, in part, mediated by CD40 signalling. In contrast, only Th2 cells induce a significant increase in Jagged 2 mRNA levels in DCs. Additionally, we show that IL-4, a hallmark Th2 cytokine, plays a role in Jagged 2 expression, as evidenced by the fact that cholera toxin, a Th2-promoting stimulus, induces Jagged 2 mRNA expression in DCs only in the presence of IL-4. Finally

Alloreactive Regulatory T Cells Allow the Generation of Mixed Chimerism and Transplant Tolerance

Artículo de publicación ISIThe induction of donor-specific transplant tolerance is one of the main goals of modern immunology. Establishment of a mixed chimerism state in the transplant recipient has proven to be a suitable strategy for the induction of long-term allograft tolerance; however, current experimental recipient preconditioning protocols have many side effects, and are not feasible for use in future therapies. In order to improve the current mixed chimerism induction protocols, we developed a non-myeloablative bone-marrow transplant (NM-BMT) protocol using retinoic acid (RA)-induced alloantigen-specific Tregs, clinically available immunosuppressive drugs, and lower doses of irradiation. We demonstrate that RA-induced alloantigen-specific Tregs in addition to a NM-BMT protocol generates stable mixed chimerism and induces tolerance to allogeneic secondary skin allografts in mice. Therefore, the establishment of mixed chimerism through the use of donor-specific Tregs rather than non-specific immunosuppression could have a potential use in organ transplantation.FONDECY

IRE1α Activation in Bone Marrow-Derived Dendritic Cells Modulates Innate Recognition of Melanoma Cells and Favors CD8+ T Cell Priming

The IRE1α/XBP1s signaling pathway is an arm of the unfolded protein response (UPR) that safeguards the fidelity of the cellular proteome during endoplasmic reticulum (ER) stress, and that has also emerged as a key regulator of dendritic cell (DC) homeostasis. However, in the context of DC activation, the regulation of the IRE1α/XBP1s axis is not fully understood. In this work, we report that cell lysates generated from melanoma cell lines markedly induce XBP1s and certain members of the UPR such as the chaperone BiP in bone marrow derived DCs (BMDCs). Activation of IRE1α endonuclease upon innate recognition of melanoma cell lysates was required for amplification of proinflammatory cytokine production and was necessary for efficient cross-presentation of melanoma-associated antigens without modulating the MHC-II antigen presentation machinery. Altogether, this work provides evidence indicating that ex-vivo activation of the IRE1α/X