628,086 research outputs found

    MCSF drives regulatory DC development in stromal co-cultures supporting hematopoiesis

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    Background: Splenic stroma overlaid with hematopoietic progenitors supports in vitro hematopoiesis with production of dendritic-like cells. Co-cultures of murine lineage-depleted bone marrow over the 5G3 stromal line produce two populations of cells, characterised as CD11b+CD11c+MHC-II− dendritic-like ‘L-DC’, and CD11b+CD11c+ MHC-II+ cells, resembling conventional dendritic cells (cDC). To date, the functional capacity of these two subsets has not been clearly distinguished. Results: Here we show both the L-DC and cDC-like subsets can be activated and induce proliferation of OT-I CD8+ T cells, being strong inducers of IL-2 and IFN-γ production. Both subsets lack ability to induce proliferation of OT-II CD4+ T cells. The cDC-like population is shown here to resemble regulatory DC in that they induce FoxP3 expression and IL10 production in OT-II CD4+ T cells, in line with their function as regulatory DC. L-DC did not activate or induce the proliferation of CD4+ T cells and did not induce FoxP3 expression in CD4+ T cells. L-DC can be distinguished from cDClike cells through their superior endocytic capacity and expression of 4-1BBL, F4/80 and Sirp-α. A comparison of gene expression by the two subsets was consistent with L-DC having an activated or immunostimulatory DC phenotype, while cDC-like cells reflect myeloid dendritic cells with inflammatory and suppressive properties, also consistent with functional characteristics as regulatory DC. When a Transwell membrane was used to prevent hematopoietic cell contact with stroma, only cDC-like cells and not L-DC were produced, and cell production was dependent on M-CSF production by stroma. Conclusion: Co-cultures of hematopoietic progenitors over splenic stroma produce two distinct subsets of dendritic-like cells. These are here distinguished phenotypically and through gene expression differences. While both resemble DC, there are functionally distinct. L-DC activate CD8+ but not CD4+ T cells, while the cDC-like population induce regulatory T cells, so reflecting regulatory DC. The latter can be enriched through Transwell co-cultures with cell production dependent on M-CSF. Keywords: Hematopoiesis, Dendritic cell, Regulatory dendritic cells, Regulatory T cellsThis work was supported by project grant #585443 to HO from the National Health and Medical Research Council of Australia. SP was supported by a graduate scholarship from the Royal Thai Government. PP was supported by an Australian National University Graduate Scholarship

    Cyclin kinase inhibitor p21: a mediator of immune tolerance: direct and indirect evidence

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    *Background:* Uncontrolled proliferation of T-cells is considered a barrier to the induction of transplantation tolerance by T regulatory cells. Therefore, cyclin kinase inhibitor p21, one of the most potent inhibitors of cell proliferation, may exert an important role in the induction/generation of T regulatory cells.
*Methods:* CD4^+^CD25^+^ and CD4^+^CD25^-^ cells were isolated from normal healthy blood donors (n=6), p21^-/-^ mice (n=9) and wild type mice (n=9). Proliferation with and without cyclosporine was quantified by ^3^H-thymidine uptake assay (expressed as counts per minute) and FoxP3 mRNA was studied by real-time quantitative RT-PCR. 
*Results:* The difference in proliferation (p<0.003) among CD4^+^CD25^+^ (15236 ± 1190) and CD4^+^CD25^-^ (50317 ± 974) T cells were proportionately similar to the difference in proliferation (p<0.001) of lymphocytes from wild type (28206 ± 2812) and p21^-/-^ mice (49624 ± 2164), proliferation of CD4^+^CD25^-^ and p21 deficient cells was resistant to cyclosporine. The number of T regulatory cells in p21^-/-^ mice were significantly (p<0.002) lower (2.6 ± 0.8%) than wild type mice (14.5 ± 1.6%,) and similar to CD4^+^CD25^-^ T cells, CD4^+^25^+^ T cells from p21^-/-^ mice lacked FoxP3 gene expression. T lymphocytes from wild type inhibited the proliferation of T lymphocytes from p21^-/-^ mice similar to the effect of CD4^+^CD25^+^ T cells on the proliferation of CD4^+^CD25^-^ cells. 
*Conclusions:* Presence of the p21 creates a milieu favorable for immune tolerance and consistent with antiproliferative and immunosuppressive effect of CD4^+^CD25^+^ T-regulatory cells. These findings support the notion that p21 could be used clinically in controlling allo-immune activation to achieve prolongation of graft survival

    Regulatory T Cells

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    Immunologic self-tolerance is critically dependent on the induction but also on the downregulation of immune responses. Though ignored and neglected for many years, suppressor T cells, now renamed regulatory T cells (Tregs), play an important role in the negative regulation of immune responses. Several subsets of Tregs have been described. Naturally occurring CD4+CD25+ Tregs are important in the prevention of autoimmune diseases. Type 1 Tregs, another subtype of Treg that is inducible, exert their suppressive activity primarily via the release of IL-10. Detailed knowledge about the phenotype and mode of action of these cells will significantly increase our understanding of the pathogenesis of autoimmune diseases and will also help to identify new therapeutic strategies

    Regulatory T cells

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    Mdivi-1, a mitochondrial fission inhibitor, modulates T helper cells and suppresses the development of experimental autoimmune encephalomyelitis.

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    BACKGROUND: Unrestrained activation of Th1 and Th17 cells is associated with the pathogenesis of multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE). While inactivation of dynamin-related protein 1 (Drp1), a GTPase that regulates mitochondrial fission, can reduce EAE severity by protecting myelin from demyelination, its effect on immune responses in EAE has not yet been studied. METHODS: We investigated the effect of Mdivi-1, a small molecule inhibitor of Drp1, on EAE. Clinical scores, inflammation, demyelination and Drp1 activation in the central nervous system (CNS), and T cell responses in both CNS and periphery were determined. RESULTS: Mdivi-1 effectively suppressed EAE severity by reducing demyelination and cellular infiltration in the CNS. Mdivi-1 treatment decreased the phosphorylation of Drp1 (ser616) on CD4+ T cells, reduced the numbers of Th1 and Th17 cells, and increased Foxp3+ regulatory T cells in the CNS. Moreover, Mdivi-1 treatment effectively inhibited IFN-γ+, IL-17+, and GM-CSF+ CD4+ T cells, while it induced CD4+ Foxp3+ regulatory T cells in splenocytes by flow cytometry. CONCLUSIONS: Together, our results demonstrate that Mdivi-1 has therapeutic potential in EAE by modulating the balance between Th1/Th17 and regulatory T cells

    FOXP3 interacts with hnRNPF to modulate pre-mRNA alternative splicing

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    FOXP3 promotes the development and function of regulatory T cells mainly through regulating the transcription of target genes. RNA alternative splicing has been implicated in a wide range of physiological and pathophysiological processes. We report here that FOXP3 associates with heterogeneous nuclear ribonucleoprotein (hnRNP) F through the exon 2-encoded region of FOXP3 and the second quasi-RNA recognition motif (qRRM) of hnRNPF. FOXP3 represses the ability of hnRNPF to bind to its target pre-mRNA and thus modulates RNA alternative splicing. Furthermore, overexpression of mouse hnRNPF in in vitro-differentiated regulatory T cells (Tregs) reduced their suppressive function. Thus, our studies identify a novel mechanism by which FOXP3 regulates mRNA alternative splicing to modulate the function of regulatory T cells

    Differential Responses of Human Regulatory T Cells (Treg) and Effector T Cells to Rapamycin

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    Background: The immunosuppressive drug rapamycin (RAPA) promotes the expansion of CD4+ CD25highFoxp3+ regulatory\ud T cells via mechanisms that remain unknown. Here, we studied expansion, IL-2R-c chain signaling, survival pathways and resistance to apoptosis in human Treg responding to RAPA.\ud Methodology/Principal Findings: CD4+CD25+ and CD4+CD25neg T cells were isolated from PBMC of normal controls (n = 21)\ud using AutoMACS. These T cell subsets were cultured in the presence of anti-CD3/CD28 antibodies and 1000 IU/mL IL-2 for 3 to 6 weeks. RAPA (1–100 nM) was added to half of the cultures. After harvest, the cell phenotype, signaling via the PI3K/ mTOR and STAT pathways, expression of survival proteins and Annexin V binding were determined and compared to values obtained with freshly-separated CD4+CD25high and CD4+CD25neg T cells. Suppressor function was tested in co-cultures with autologous CFSE-labeled CD4+CD25neg or CD8+CD25neg T-cell responders. The frequency and suppressor activity of Treg were increased after culture of CD4+CD25+ T cells in the presence of 1–100 nM RAPA (p,0.001). RAPA-expanded Treg were largely CD4+CD25highFoxp3+ cells and were resistant to apoptosis, while CD4+CD25neg T cells were sensitive. Only Treg upregulated anti-apoptotic and down-regulated pro-apoptotic proteins. Treg expressed higher levels of the PTEN protein than CD4+CD25neg cells. Activated Treg6RAPA preferentially phosphorylated STAT5 and STAT3 and did not utilize the PI3K/ mTOR pathway.\ud Conclusions/Significance: RAPA favors Treg expansion and survival by differentially regulating signaling, proliferation and sensitivity to apoptosis of human effector T cells and Treg after TCR/IL-2 activation

    Immunity to self co-generates regulatory T cells

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    Immune responses to self are kept in check by tolerance mechanisms, including suppression by regulatory T cells (Tregs). The defective generation of Tregs specific for self-antigens may lead to autoimmune disease. We identified a novel population of human CD4^+^ Tregs, characterized by high surface expression of CD52, which is co-generated in response to autoantigen. Blood CD4^+^CD52^hi^ T cells were generated preferentially in response to low-dose autoantigen and suppressed proliferation and interferon-[gamma] production by other T cells. Depletion of resting CD4^+^CD52^hi^ T cells enhanced the T-cell response to autoantigen. CD4^+^CD52^hi^ Tregs were neither derived from nor distinguished by markers of conventional resting CD4^+^CD25^+^ Tregs. In response to the pancreatic islet autoantigens glutamic acid decarboxylase, the generation of CD4^+^CD52^hi^ Tregs was impaired in individuals with and at-risk for type 1 diabetes, compared to healthy controls and individuals with type 2 diabetes. CD4^+^CD52^hi^ Tregs co-generated to self-antigen may therefore contribute to immune homeostasis and protect against autoimmune disease

    The role of T regulatory lymphocytes in lymphoma

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    T regulatory cells play a crucial role in immunological unresponsiveness to selfantigens and in suppressing excessive immune responses deleterious to the host. T regulatory cells are produced in the thymus as a functionally mature subpopulation of T cells. They can be induced from naive T cells in the periphery and express their marker as a forkhead/winged helix transcription factor called FoxP3. In patients with lymphomas where T regulatory cells serve as suppressor anti-tumor cytotoxicity, decreased numbers of T regulatory cells are associated with a favorable prognosis. In contrast, in patients with lymphomas where T regulatory cells function as anti-tumor cytotoxic agents, enhanced numbers of T regulatory cells are associated with a favorable prognosis. Tumors actively promote the accumulation of these cells through several mechanisms that involve activation of naturally occurring T regulatory cells as well as conversion of non-T regulatory cells into T regulatory cells. Tumor-derived prostaglandin E2 can increase T regulatory cell activity and induce a regulatory phenotype in CD4+CD25+T cells. On the other hand, a balance between T regulatory and Th17 cells is essential for maintaining homeostasis of anti-tumor immunity. Accelerating processes such as increasing the amounts of IL-6 or IL-17 can enhance FoxP3 T regulatory cell expression and result in a lymphoma or inactivation of T cell CD4+. This effect is the reason for malignancy and a reduction in anti-tumor immune response. In this systematic review we intend to analyze this relationship. We have collected and analyzed the majority of recently published articles on the role of T regulatory cells as a review article