Sca-1 expression defines different developmental stages of mouse PDC that show functional heterogeneity in the endosomal but not lysosomal TLR9 response
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ABSTRACT: Plasmacytoid dendritic cells (PDC) play an important role in innate and adaptive immunity and were shown to be identical to previously described natural IFN-α-producing cells (NIP). Here, we describe two functionally distinct PDC subpopulations that are characterized by the differential expression of stem cell antigen-1 (Sca-1; Ly-6A/E). Sca-1- PDC are mainly found in the bone marrow, appear first during development, show a higher proliferative activity and represent the more precursor phenotype. Sca-1+ PDC are mostly located in secondary lymphoid organs and show higher expression of MHC class II molecules. Sca-1- PDC give rise to a Sca-1+ subset upon activation or in response to tissue-specific factors. Interestingly, in contrast to Sca-1- PDC, Sca-1+ PDC are defective in type I IFN production upon endosomal TLR9 stimulation, whereas lysosomal signaling via TLR9 is functional in both subsets. Gene expression analysis revealed that osteopontin (Opn) is strongly upregulated in Sca-1- PDC. This data provides evidence for the molecular basis of the observed functional heterogeneity, as the intracellular isoform of Opn couples TLR9 signaling to IFN-α expression. Taken together, our results indicate that Sca-1- PDC are an early developmental stage of PDC with distinct innate functions representing the true murine NIP.
Project description:Plasmacytoid dendritic cells (PDC) play an important role in innate and adaptive immunity and were shown to be identical to previously described natural IFN-M-NM-1-producing cells (NIP). Here, we describe two functionally distinct PDC subpopulations that are characterized by the differential expression of stem cell antigen-1 (Sca-1; Ly-6A/E). Sca-1- PDC are mainly found in the bone marrow, appear first during development, show a higher proliferative activity and represent the more precursor phenotype. Sca-1+ PDC are mostly located in secondary lymphoid organs and show higher expression of MHC class II molecules. Sca-1- PDC give rise to a Sca-1+ subset upon activation or in response to tissue-specific factors. Interestingly, in contrast to Sca-1- PDC, Sca-1+ PDC are defective in type I IFN production upon endosomal TLR9 stimulation, whereas lysosomal signaling via TLR9 is functional in both subsets. Gene expression analysis revealed that osteopontin (Opn) is strongly upregulated in Sca-1- PDC. This data provides evidence for the molecular basis of the observed functional heterogeneity, as the intracellular isoform of Opn couples TLR9 signaling to IFN-M-NM-1 expression. Taken together, our results indicate that Sca-1- PDC are an early developmental stage of PDC with distinct innate functions representing the true murine NIP. The dataset comprises eight samples divided into two sample groups consisting of Sca-1(-) and Sca-1(+) PDCs collected from in vitro culture of differentiated bone marrow precursor cells using mFlt3-L
Project description:Type I interferons (IFN) are crucial mediators of human innate and adaptive immunity and are massively produced from plasmacytoid dendritic cells (pDC). IRF7 is a critical regulator of type I IFN production when pathogens are detected by TLR7/9 in pDC. However, hyperactivation of pDC can cause life-threatening autoimmune diseases. To avoid the deleterious effects of aberrant pDC activation, tight regulation of IRF7 is required. Nonetheless, the detailed mechanisms of how IRF7 transcription is regulated in pDC are still elusive. To this end, we identified the global gene expression changes after stimulation of human primary pDC with the TLR9 agonist CpGB. We identified that the transcription factor MYC is prominently upregulated upon CpGB engagement in pDC. Moreover, when we knocked down MYC in the pDC-like cell line GEN2.2, production of interferon-stimulated genes (ISGs) was dramatically increased and was further enhanced by CpGB. Interestingly, MYC is shown to be recruited to the IRF7 promoter region through interaction with NCOR2/HDAC3 for its repression, and HDAC3 inhibition enhanced IRF7 expression and IFNβ production. Interestingly, activation of TLR9-mediated NF-kB and MAPK and nuclear translocation of IRF7 were greatly enhanced by MYC depletion. Pharmaceutical inhibition of MYC recovered IRF7 expression, further confirming the negative role of MYC in the antiviral response by pDC. Furthermore, the inverse correlation of MYC and IRF7 was validated in psoriasis skin sample datasets. Therefore, our results identify the novel immunomodulatory role of MYC in human pDC and may add to our understanding of aberrant pDC function in autoimmune diseases.
Project description:Type I interferons (IFN) are crucial mediators of human innate and adaptive immunity and are massively produced from plasmacytoid dendritic cells (pDC). IRF7 is a critical regulator of type I IFN production when pathogens are detected by TLR7/9 in pDC. However, hyperactivation of pDC can cause life-threatening autoimmune diseases. To avoid the deleterious effects of aberrant pDC activation, tight regulation of IRF7 is required. Nonetheless, the detailed mechanisms of how IRF7 transcription is regulated in pDC are still elusive. To this end, we identified the global gene expression changes after stimulation of human primary pDC with the TLR9 agonist CpGB. We identified that the transcription factor MYC is prominently upregulated upon CpGB engagement in pDC. Moreover, when we knocked down MYC in the pDC-like cell line GEN2.2, production of interferon-stimulated genes (ISGs) was dramatically increased and was further enhanced by CpGB. Interestingly, MYC is shown to be recruited to the IRF7 promoter region through interaction with NCOR2/HDAC3 for its repression, and HDAC3 inhibition enhanced IRF7 expression and IFNβ production. Interestingly, activation of TLR9-mediated NF-kB and MAPK and nuclear translocation of IRF7 were greatly enhanced by MYC depletion. Pharmaceutical inhibition of MYC recovered IRF7 expression, further confirming the negative role of MYC in the antiviral response by pDC. Furthermore, the inverse correlation of MYC and IRF7 was validated in psoriasis skin sample datasets. Therefore, our results identify the novel immunomodulatory role of MYC in human pDC and may add to our understanding of aberrant pDC function in autoimmune diseases.
Project description:Type I interferons (IFN) are crucial mediators of human innate and adaptive immunity and are massively produced from plasmacytoid dendritic cells (pDC). IRF7 is a critical regulator of type I IFN production when pathogens are detected by TLR7/9 in pDC. However, hyperactivation of pDC can cause life-threatening autoimmune diseases. To avoid the deleterious effects of aberrant pDC activation, tight regulation of IRF7 is required. Nonetheless, the detailed mechanisms of how IRF7 transcription is regulated in pDC are still elusive. To this end, we identified the global gene expression changes after stimulation of human primary pDC with the TLR9 agonist CpGB. We identified that the transcription factor MYC is prominently upregulated upon CpGB engagement in pDC. Moreover, when we knocked down MYC in the pDC-like cell line GEN2.2, production of interferon-stimulated genes (ISGs) was dramatically increased and was further enhanced by CpGB. Interestingly, MYC is shown to be recruited to the IRF7 promoter region through interaction with NCOR2/HDAC3 for its repression, and HDAC3 inhibition enhanced IRF7 expression and IFNβ production. Interestingly, activation of TLR9-mediated NF-kB and MAPK and nuclear translocation of IRF7 were greatly enhanced by MYC depletion. Pharmaceutical inhibition of MYC recovered IRF7 expression, further confirming the negative role of MYC in the antiviral response by pDC. Furthermore, the inverse correlation of MYC and IRF7 was validated in psoriasis skin sample datasets. Therefore, our results identify the novel immunomodulatory role of MYC in human pDC and may add to our understanding of aberrant pDC function in autoimmune diseases.
Project description:Human rhinoviruses (HRV) are usually innocuous viruses; however, they can trigger serious consequences in certain individuals, especially in the setting of deficient interferon (IFN) synthesis. Plasmacytoid dendritic cells (pDC) are key IFN producing cells, though we know little about the mechanisms by which pDC regulate HRV-induced immune responses. Herein we used gene expression microarrays to examine HRV-induced mRNA in blood mononuclear cells from healthy people, in combination with pDC depletion to assess whether observed expression patterns were pDC dependent. As expected, pDC depletion led to a major reduction in HRV-induced IFN-α release, and this was associated with profound differences in gene expression between intact PBMC and pDC depleted PBMC. pDC depletion led to major changes in upstream regulators, with 70-80% of the HRV activated genes appearing to be pDC dependent. PCR validation experiments confirmed changes seen in the microarrays, specifically the extent to which the following differentially expressed genes were highly pDC dependent: the transcription factor IRF7, both IL-27 chains (IL-27 and EBI3), the alpha chain of the IL-15 receptor (IL-15RA) and the IFN stimulated gene IFI27. IL-6, IFN-γ and IL-27 protein synthesis were also highly pDC dependent. Supplementing pDC-depleted cultures with either recombinant IFN-γ, IL-15, IL-27 or IL-6 was able to restore the IFN-α response, thereby compensating for the absence of pDC. Though pDC comprise only a minority population of migratory leukocytes, our findings highlight the extent to which these cells are able to exert a profound effect on the immune response to HRV.
Project description:Robust type I interferon (IFN-alpha/beta) production in plasmacytoid dendritic cells (pDCs) is critical for anti-viral immunity. Here we demonstrated a role for the mammalian target of rapamycin (mTOR) pathway in regulating interferon production by pDCs. Inhibition of mTOR or the ‘downstream’ mediators of mTOR p70S6K1,2 kinases during pDC activation via Toll-like receptor 9 (TLR9) blocked the interaction of TLR9 with the adaptor MyD88 and the subsequent activation of interferon response factor 7 (IRF7), resulting in impaired IFN-alpha production. Microarray analysis confirmed that inhibition of mTOR by the immunosuppressive drug rapamycin suppressed anti-viral and anti-inflammatory gene expression. Consistent with this, targeting rapamycin-encapsulated microparticles to antigen-presenting cells in vivo resulted in a diminution of IFN-alpha production in response to CpG DNA or the yellow fever vaccine virus strain 17D. Thus, mTOR signaling plays a critical role in TLR-mediated IFN-alpha responses by pDCs. CpGA is a TLR9 agonist. pDCs were isolated from mouse spleen or human PBMC. The effect of rapamycin on pDCs IFN-alpha production as induced by TLR ligands was studied. The mechanism of rapamycin effect was dissected in RAW cell line.
Project description:Robust type I interferon (IFN-alpha/beta) production in plasmacytoid dendritic cells (pDCs) is critical for anti-viral immunity. Here we demonstrated a role for the mammalian target of rapamycin (mTOR) pathway in regulating interferon production by pDCs. Inhibition of mTOR or the ‘downstream’ mediators of mTOR p70S6K1,2 kinases during pDC activation via Toll-like receptor 9 (TLR9) blocked the interaction of TLR9 with the adaptor MyD88 and the subsequent activation of interferon response factor 7 (IRF7), resulting in impaired IFN-alpha production. Microarray analysis confirmed that inhibition of mTOR by the immunosuppressive drug rapamycin suppressed anti-viral and anti-inflammatory gene expression. Consistent with this, targeting rapamycin-encapsulated microparticles to antigen-presenting cells in vivo resulted in a diminution of IFN-alpha production in response to CpG DNA or the yellow fever vaccine virus strain 17D. Thus, mTOR signaling plays a critical role in TLR-mediated IFN-alpha responses by pDCs. CpGA is a TLR9 agonist.
Project description:Plasmacytoid dendritic cells (pDCs) can be activated by the endosomal TLRs, and contribute to the pathogenesis of systemic lupus erythematosus (SLE) by producing type I IFNs. Thus, blocking TLR-mediated pDC activation may represent a useful approach for the treatment of SLE. In an attempt to identify a therapeutic target for blocking TLR signaling in pDCs, we investigated the contribution of Bruton's tyrosine kinase (Btk) to the activation of pDCs by TLR7 and TLR9 stimulation by using a selective Btk inhibitor RN486. Stimulation of TLR7 and 9 with their respective agonist, namely, gardiquimod and type A CpG ODN2216, resulted in the activation of human pDCs, as demonstrated by the expression of activation markers (CD69, CD40, and CD86), elevated production of IFN-alpha and other inflammatory cytokines, as well as up-regulation of numerous genes including IFN-alpha-inducible genes and activation of interferon regulatory factor 7 (IRF7) and NF-kB. RN486 inhibited all of these events induced by TLR9, but not TLR7 stimulation, with a nanomolar potency for inhibiting type A CpG ODN2216-mediated production of cytokines (e.g., IC50=386 nM for inhibiting IFN-alpha). Our data reveal Btk as an important regulatory enzyme in the TLR9 pathway, and a potential therapeutic target for SLE and other TLR-driven diseases. pDCs from healthy donors (n=4) were treated with gardiquimod (TLR7 agonist) or ODN 2216 (TLR9 agonist) with or without BTK inhibitor for 3 hours.
Project description:Plasmacytoid dendritic cells (pDCs) are key components of the innate immune response that are capable of synthesizing and rapidly releasing vast amounts of type I interferons (IFNs), particularly IFN-alpha. Here we investigated whether pDCs, often regarded as a mere source of IFN, discriminate between various functionally discrete stimuli and to what extent this reflects differences in pDC responses other than IFN-alpha release. To examine the ability of pDCs to differentially respond to various doses of intact and infectious HIV, hepatitis C virus, and H1N1 influenza virus, whole-genome gene expression analysis, enzyme-linked immunosorbent assays, and flow cytometry were used to investigate pDC responses at the transcriptional, protein, and cellular levels. Our data demonstrate that pDCs respond differentially to various viral stimuli with significant changes in gene expression, including those involved in pDC activation, migration, viral endocytosis, survival, or apoptosis. In some cases, the expression of these genes was induced even at levels comparable to that of IFN-alpha. Interestingly, we also found that depending on the viral entity and the viral titer used for stimulation, induction of IFN-alpha gene expression and the actual release of IFN-alpha are not necessarily temporally coordinated. In addition, our data suggest that high-titer influenza A (H1N1) virus infection can stimulate rapid pDC apoptosis.
Project description:Plasmacytoid dendritic cells (pDC) are the major source of type I interferons (IFN-I) during viral infections, in response to triggering of endosomal Toll Like Receptors (TLR) 7 or 9 by viral single-stranded RNA or unmethylated CpG DNA, respectively. IFN-I production in pDC occurs in specialized endosomes encompassing preformed signaling complexes of TLR7 or 9 with their adaptor molecule MyD88 and the transcription factor interferon regulatory factor 7 (IRF7). The triggering of TLR leads to IRF7 phosphorylation, nuclear translocation and binding to the promoters of the genes encoding IFN-I to initiate their transcription. pDC express uniquely high levels of IRF7 at steady state and this expression is further enhanced by positive IFN-I feedback signaling during viral infections. However, the specific cell-intrinsic roles of MyD88 versus IFN-I signaling in pDC responses to a viral infection have not been rigorously dissected. To achieve this aim, we generated mixed bone marrow chimera mice (MBMC) allowing to rigorously compare the gene expression profiles of WT versus Ifnar1-KO or MyD88-KO pDC isolated from the same animals at steady state or after infection with the mouse cytomegalovirus (MCMV). Our results indicate that, in vivo during MCMV infection, pDC undergo a major transcriptional reprogramming, under combined instruction of IFN-I, IFN-γ and direct TLR triggering. However, these different stimuli drive specific, largely distinct, gene expression programs. We rigorously determined which gene modules require cell-intrinsic IFN-I signaling for their induction in pDC during a physiological viral infection in vivo. We delineated non-redundant versus shared versus antagonistic responses with IFN-γ. We demonstrated that cell-intrinsic IFN-I responsiveness is dispensable for induction of the expression of all IFN-I/III genes and many cytokines or chemokines in pDC during MCMV infection, contrary to MyD88 signaling.