Project description:Although much is known on the transcriptional profiles of dendritic cells (DCs) during maturation, the molecular switches critical for the acquisition of a tolerogenic program by DCs are still obscure. In the present study, we explored the gene expression pattern of CD8+ DCs purified from the mouse spleen and treated with interferon (IFN)-gamma. The cytokine, indeed, potentiates the tolerogenic potential of this DC subset via induction of the immunosuppressive tryptophan catabolism mediated by indoleamine 2,3-dioxygenase (IDO). By comparing the expression of the IFN-gamma-modulated genes in IDO+ versus IDO- murine DCs, we found a consistent and selective association of the IDO-competent phenotype with the down-modulation of the Tyrobp gene, encoding the adapter molecule DAP12. IFN-gamma-mediated down-modulation of this gene involved IFN consensus sequence binding protein (ICSBP), a transcription factor also known as IRF-8. While silencing of Tyrobp conferred IDO functional competence on IDO- DCs, silencing of Icsbp1 in IDO+ cells completely abolished IDO expression and function. In parallel, silencing of TYROBP conferred IDO competence on human IDO- DCs while silencing of IRF8 impaired IDO expression and activity in human IDO+ DCs. Therefore, the same small set of molecular switches controls IDO competence in murine and human DCs. Keywords: Time-course, treatment with agent (IFN-gamma)
Project description:Although much is known on the transcriptional profiles of dendritic cells (DCs) during maturation, the molecular switches critical for the acquisition of a tolerogenic program by DCs are still obscure. In the present study, we explored the gene expression pattern of CD8+ DCs purified from the mouse spleen and treated with interferon (IFN)-gamma. The cytokine, indeed, potentiates the tolerogenic potential of this DC subset via induction of the immunosuppressive tryptophan catabolism mediated by indoleamine 2,3-dioxygenase (IDO). By comparing the expression of the IFN-gamma-modulated genes in IDO+ versus IDO- murine DCs, we found a consistent and selective association of the IDO-competent phenotype with the down-modulation of the Tyrobp gene, encoding the adapter molecule DAP12. IFN-gamma-mediated down-modulation of this gene involved IFN consensus sequence binding protein (ICSBP), a transcription factor also known as IRF-8. While silencing of Tyrobp conferred IDO functional competence on IDO- DCs, silencing of Icsbp1 in IDO+ cells completely abolished IDO expression and function. In parallel, silencing of TYROBP conferred IDO competence on human IDO- DCs while silencing of IRF8 impaired IDO expression and activity in human IDO+ DCs. Therefore, the same small set of molecular switches controls IDO competence in murine and human DCs. Experiment Overall Design: Labeled cRNA extracted from a a total of 8 samples was hybridized to the Affymetrix GeneChip MG-U74Av2 which contains 12,488 probe sets . The 4 control samples included 2 replicates each of RNA extracted from cells incubated in medium for 4 and 16 hours. Treated samples included 2 replicates each of RNA extracted from cells incubated in IFN-gammas for 4 and 16 hours.
Project description:Infection with Chlamydia pneumoniae, a human respiratory pathogen, has been associated with various chronic diseases such as asthma, coronary heart disease and importantly atherosclerosis. Possibly because the pathogen can exist in a persistent form. TNF-a has been reported to induce chlamydial persitence in epithelial cell lines, however the mechanism of TNF-a-induced persistence has not been reported. Moreover, C. pneumoniae persistently infect human dendritic cells (DCs) and activate DCs to produce cytokines including TNF-a. Induction of chlamydial persistence by other cytokines such as IFN-g is known to be due to indoleamine 2,3-dioxygenase (IDO) activity. The present study therefore, investigated whether C. pneumoniae infection can induce IDO activity in dendritic cells, and whether the restriction of chlamydial growth in the DCs by TNF-a is IDO-dependent. Our data indicate that infection of DCs with C. pneumoniae resulted in the induction of IDO expression. Reporting on our use of anti-TNF-a antibody adalimumab and varying concentrations of TNF-a, we further demonstrate that IDO induction following infection of DCs with C. pneumoniae is TNF-a-dependent. The anti-chlamydial activity induced by TNF-a and the expression of chlamydial 16S rRNA gene, euo, groEL1, ftsk and tal genes was correlated with the induction of IDO. Addition of excess amounts of tryptophan to the DC cultures resulted in abrogation of the TNF-a-mediated chlamydial growth restriction. These findings suggest that infection of DCs by C. pneumoniae induces production of functional IDO, which subsequently causes depletion of tryptophan. This may represent a potential mechanism for DCs to restrict bacterial growth in chlamydial infections. Keywords: Chlamydia pneumoniae, Dendritic cells, TNF-a, Indoleamine 2,3-dioxygenase
Project description:Neutrophil granulocytes are the major cells involved in the Chlamydia trachomatis (C.trachomatis)-mediated inflammation and histopathology. A key gene in human intracellular antichlamydial defense is the tryptophan degrading enzyme indoleamine 2,3-dioxygenase (IDO), which limits the growth of the tryptophan auxotroph Chlamydia. Despite its importance, the role of IDO in the intracellular defense against Chlamydia in neutrophils has not yet been characterized. Affymetrix microarrays were used to obtain global gene expression data for monitoring the effect of C. trachomatis serovar D infection on the transcriptome of human neutrophil granulocytes.
Project description:Dendritic cells (DCs) are pivotal drivers of anti-tumor immunity, but many of the DCs in tumors appear dysfunctional or immunosuppressive. Using mouse models, we found that robustly immunogenic DCs can arise by differentiation from immature myeloid precursor cells during inflammation. In tumors, however, differentiation of these inflammatory DCs was blocked by a cell-intrinsic signaling pathway created by Bruton’s Tyrosine Kinase (BTK) and the tryptophan-degrading enzyme indoleamine 2,3-dioxygenase (IDO).
Project description:Dendritic cells (DCs) are pivotal drivers of anti-tumor immunity, but many of the DCs in tumors appear dysfunctional or immunosuppressive. Using mouse models, we found that robustly immunogenic DCs can arise by differentiation from immature myeloid precursor cells during inflammation. In tumors, however, differentiation of these inflammatory DCs was blocked by a cell-intrinsic signaling pathway created by Bruton’s Tyrosine Kinase (BTK) and the tryptophan-degrading enzyme indoleamine 2,3-dioxygenase (IDO).
Project description:Dendritic cells (DCs) are pivotal drivers of anti-tumor immunity, but many of the DCs in tumors appear dysfunctional or immunosuppressive. Using mouse models, we found that robustly immunogenic DCs can arise by differentiation from immature myeloid precursor cells during inflammation. In tumors, however, differentiation of these inflammatory DCs was blocked by a cell-intrinsic signaling pathway created by Bruton’s Tyrosine Kinase (BTK) and the tryptophan-degrading enzyme indoleamine 2,3-dioxygenase (IDO).
Project description:Immunity to Mycobacterium tuberculosis in humans and in mice requires interferon gamma (IFNγ). Wheras IFNγ has been studied extensively for its effects on macrophages in tuberculosis, we determined that protective immunity to tuberculosis also requires IFNγ-responsive non-hematopoietic cells. Bone marrow chimeric mice with IFNγ-unresponsive lung epithelial and endothelial cells exhibited earlier mortality and higher bacterial burdens than control mice, under-expressed indoleamine-2,3-dioxygenase (Ido1) in lung endothelium and epithelium and over-expressed interleukin-17 (IL-17) with massive neutrophilic inflammation in the lungs. We also found that the products of IDO catabolism of tryptophan selectively inhibit IL-17 production by Th17 cells, by inhibiting the action of IL-23. These results reveal a previously-unsuspected role for IFNγ responsiveness in non-hematopoietic cells in regulation of immunity to M. tuberculosis, and reveal a mechanism for IDO inhibition of Th17 cell responses.
Project description:Activated T cells polarize mesenchymal stromal cells (MSCs) to a proinflammatory Th1 phenotype which likely has an important role in amplifying the immune response in the tumor microenvironment. We investigated the role of interferon gamma (IFN-g) and tumor necrosis factor alpha (TNF-a), two factors produced by activated T cells, in MSC polarization. Gene expression and culture supernatant analysis showed that TNF-a and IFN-g stimulated MSCs expressed distinct sets of proinflammatory factors. The combination of IFN-g and TNF-a was synergistic and induced a transcriptome most similar to that found in MSCs stimulation with activated T cells and similar to that found in the inflamed tumor microenvironment; a Th1 phenotype with the expression of the immunosuppressive factors IL-4, IL-10, CD274/PD-L1 and indoleamine 2,3 dioxygenase (IDO). Single cell qRT-PCR analysis showed that the combination of IFN-g and TNF-a polarized uniformly to this phenotype. The combination of IFN-g and TNF-a results in the synergist uniform polarization of MSCs toward a primarily Th1 phenotype. The stimulation of MSCs by IFN-g and TNF-a released from activated tumor infiltrating T cells is likely responsible for the production of many factors that characterize the tumor microenvironment.
Project description:Early acute rejection of human allografts is mediated by circulating alloreactive host effector memory T cells (TEM). TEM infiltration typically occurs across graft post-capillary venules and involves sequential interactions with graft-derived endothelial cells (ECs) and pericytes (PCs). While the role of ECs in allograft rejection has been extensively studied, contributions of PCs to this process are largely unknown. This study aimed to characterize the effects and mechanisms of interactions between human PCs and allogeneic TEM. We report that unstimulated PCs, like ECs, can directly present alloantigen to TEM but while IFN-γ-activated ECs (γ-ECs) show increased ability to stimulate alloreactive T cells, IFN-γ-activated PCs (γ-PCs) instead suppress TEM proliferation but not cytokine production or signaling. RNA sequencing analysis of PCs, γ-PCs, ECs, and γ-ECs reveal induction of indoleamine 2,3-dioxygenase 1 (IDO1) in γ-PCs to significantly higher levels than in γ-ECs that correlates with tryptophan depletion in vitro. Consistently, shRNA knockdown of IDO1 markedly reduces -PC-mediated immunoregulatory effects. Adoptively transferred T cells induced PC expression of IDO1 in allogeneic human skin grafts on immunodeficient mice. We conclude that immunosuppressive properties of human PCs are not intrinsic but instead result from IFN-γ-induced IDO1-mediated tryptophan depletion.