Monocyte‐Derived Dendritic Cells: An Updated View on an Old Concept

Cardiovascular diseases (CVDs) are one of the leading causes of mortality worldwide.1 It has been so for decades, notwithstanding a wide array of – mostly preventive – treatment modalities targeting known risk factors, such as hyperlipidemia, type 2 diabetes mellitus, hypertension, or obesity. Recent technical and conceptual advances have unveiled important contributions of the immune system in the pathophysiology of a variety of CVDs such as atherosclerosis, ischemic stroke, chronic heart failure, and other myocardial conditions like myocardial ischemia and reperfusion, viral myocarditis, and cardiac transplantation.2–4 In many of these disorders, so-called danger-associated molecular patterns (DAMPs), released from necrotic tissue and dying cells, can lead to the activation of certain immune cell populations such as monocytes/ macrophages, granulocytes, and T cells, thus aggravating ongoing inflammatory processes at the lesion site. Dendritic cells (DCs) are key modulators of immunity, pivotal in directing innate and adaptive immune responses against microbial, viral, but also modified self-antigens present at the sites of injury. Given the tissue trauma underlying various CVDs, it is not surprising that recent observations have allocated a regulatory role for DCs in CVD-associated immune responses. Interestingly, nondiseased arteries of young individuals were seen to host a network of resident vascular DCs (CD1a+ S100+ lag+ CD31− CD83− CD86−),5 representing a phenotype related to Langerhans cells in the skin. In agreement, monocyte-derived CD11c+ CD68+ dendritic cells could be detected in the atherosclerosis-prone lesser curvature and aortic sinus in inbred atherosclerosis-susceptible (C57Bl/6), but not resistant mouse strains (balb/c).6 Murine vascular resident DCs express an immature phenotype with low expression of costimulatory molecules, and are present in the subendothelial space with occasional probing into the vascular lumen. DCs have …

Selective 5-Lipoxygenase Expression in Langerhans Cells and Impaired Dendritic Cell Migration in 5-LO-Deficient Mice Reveal Leukotriene Action in Skin

The role of dendritic cells in asthma

Article Figures and data Abstract Editor's evaluation Introduction Results Discussion Materials and methods Appendix 1 Data availability References Decision letter Author response Article and author information Metrics Abstract Transcription factors play a determining role in lineage commitment and cell differentiation. Interferon regulatory factor 8 (IRF8) is a lineage determining transcription factor in hematopoiesis and master regulator of dendritic cells (DC), an important immune cell for immunity and tolerance. IRF8 is prominently upregulated in DC development by autoactivation and controls both DC differentiation and function. However, it is unclear how Irf8 autoactivation is controlled and eventually limited. Here, we identified a novel long non-coding RNA transcribed from the +32 kb enhancer downstream of Irf8 transcription start site and expressed specifically in mouse plasmacytoid DC (pDC), referred to as lncIrf8. The lncIrf8 locus interacts with the lrf8 promoter and shows differential epigenetic signatures in pDC versus classical DC type 1 (cDC1). Interestingly, a sequence element of the lncIrf8 promoter, but not lncIrf8 itself, is crucial for mouse pDC and cDC1 differentiation, and this sequence element confers feedback inhibition of Irf8 expression. Taken together, in DC development Irf8 autoactivation is first initiated by flanking enhancers and then second controlled by feedback inhibition through the lncIrf8 promoter element in the +32 kb enhancer. Our work reveals a previously unrecognized negative feedback loop of Irf8 that orchestrates its own expression and thereby controls DC differentiation. Editor's evaluation Authors provide valuable evidence identifying a lncRNA transcribed specifically in the pDC subtype from the +32Kb promoter region which is also the region for the enhancer for Irf8 specifically in the cDC1 subtype. With convincing methodology, they provide in-depth analysis about the possible role of lncIrf8, and its promoter region and cross-talk with Irf8 promoter to identify that it is not the lncIRF8 itself but its promoter region that is crucial for pDC and cDC1 differentiation conferring feedback inhibition of Irf8 transcription. The work will be of interest to immunologists working on immune cell development. https://doi.org/10.7554/eLife.83342.sa0 Decision letter Reviews on Sciety eLife's review process Introduction Lineage-determining transcription factors (TF) are master regulators of gene programs that frequently initiate self-reinforcing loops by autoactivation. TF autoactivation is important for cells to pass restriction points during development (referred to as points of no return) and to enforce cellular identity. Molecular circuitries of autoactivation have been studied for several TF, such as GATA-binding factor 1 (GATA1), PU.1 (encoded by Spi1), CCAAT enhancer-binding protein α and ε (C/EBPα and ε; Graf and Enver, 2009; Loughran et al., 2020; Nishimura et al., 2000; Okuno et al., 2005; Theilgaard-Mönch et al., 2022). A further example is interferon regulatory factor 8 (IRF8), which shows autoactivation in cooperation with basic leucine zipper ATF-like transcription factor 3 (BATF3; Anderson et al., 2021; Grajales-Reyes et al., 2015). An important principle in nature is negative feedback control to avoid signal overshooting and toxicity. Negative feedback control applies also to lineage-determining TF; however, there is a paucity on our knowledge of the molecular mechanisms involved. IRF8 is a hematopoietic TF positioned at the center of the regulatory gene network for dendritic cell (DC) development (Anderson et al., 2021; Belz and Nutt, 2012; Chauvistré and Seré, 2020; Kim et al., 2020; Lin et al., 2015; Nutt and Chopin, 2020; Tamura et al., 2015; Verlander et al., 2022). IRF8 is a member of the interferon regulatory factor (IRF) family of TF. Initially members of this TF family were found to mediate the induction of interferon induced genes, but are now known to serve diverse functions in regulating the immune system (Honda and Taniguchi, 2006; Tamura et al., 2008). Irf8 knockout mice show abnormal development of classical DC type 1 (cDC1) and plasmacytoid DC (pDC) (Durai et al., 2019; Schiavoni et al., 2002; Sichien et al., 2016; Tsujimura et al., 2003). Irf8 is prominently upregulated during DC development by autoactivation (Grajales-Reyes et al., 2015; Lin et al., 2015), yet how Irf8 autoactivation is controlled and eventually limited, and the epigenetic mechanisms involved is largely unknown. Irf8 expression in hematopoietic cells is induced and maintained by enhancers located at –50 kb,+32 kb,+41 kb and +56 kb relative to Irf8 transcription start site (TSS) (Anderson et al., 2021; Bagadia et al., 2019; Durai et al., 2019; Grajales-Reyes et al., 2015; Murakami et al., 2021; Schönheit et al., 2013). Enhancers are cis-regulatory sequences with multiple TF binding sites that cooperatively bind TF and thereby activate transcription, as demonstrated by many studies including our work (Davidson et al., 1986; Long et al., 2016; Wildeman et al., 1986; Zenke et al., 1986). Enhancers regulate complex gene networks and can also produce non-coding RNA, referred to as enhancer RNA (eRNA). eRNA serve as an indicator for enhancer activity and some eRNA have an activity on their own and act in cis or trans to regulate cell fate decisions (Sartorelli and Lauberth, 2020; Statello et al., 2021). Enhancer-associated long non-coding RNA (lncRNA) represent a class of lncRNA transcribed from active enhancers. Thus, eRNA and enhancer-associated lncRNA provide opportunities to detect enhancer activity and to investigate enhancer function. DC are highly specialized immune cells that play a critical role in regulating innate and adaptive immune responses (Cabeza-Cabrerizo et al., 2021). DC develop from hematopoietic stem cells (HSC) via successive steps of lineage commitment and differentiation. More specifically, HSC develop into multipotent progenitors (MPP) that are committed to DC restricted common DC progenitors (CDP) and differentiate into classic DC (cDC) type 1 and type 2 (cDC1 and cDC2, respectively) and pDC (Anderson et al., 2021; Cabeza-Cabrerizo et al., 2021; Ginhoux et al., 2022; Nutt and Chopin, 2020; Rodrigues and Tussiwand, 2020). pDC were recently also shown to develop from lymphoid progenitors (Dress et al., 2019; Rodrigues et al., 2018; Rodrigues and Tussiwand, 2020). Differential expression of Irf8 regulates DC and monocyte specification in a dose-dependent manner (Cytlak et al., 2020; Murakami et al., 2021). Irf8 expression starts at the CDP stage, and is high in pDC and cDC1, which is attributed to the autoactivation of Irf8 during DC subsets specification (Grajales-Reyes et al., 2015; Lin et al., 2015). Interestingly, IRF8 can act as a transcriptional activator or repressor in hematopoiesis by interacting with different partner TF and binding to specific DNA sequences (Tamura et al., 2015). As an activator, IRF8 binds to its own promoter in DC differentiation, which is considered as the autoactivation capacity of Irf8 (Grajales-Reyes et al., 2015; Lin et al., 2015). For instance, IRF8 interacts with partner TF, such as PU.1, to initiate Irf8 autoactivation at the CDP stage (Grajales-Reyes et al., 2015). Inversely, IRF8 inhibits C/EBPα activity in neutrophil differentiation (Kurotaki et al., 2014). IRF8 also represses C/EBPβ to generate and maintain DC lineage-specific enhancer landscapes (Bornstein et al., 2014). In addition, IRF8 is important for the Myc-Mycl transition in DC differentiation (Anderson lll et al., 2021). IRF8 represses Myc expression in progenitors, while IRF8 at high levels interacts with PU.1 and drives Mycl expression (Anderson lll et al., 2021). All this emphasizes the central position of IRF8 in coordinating the gene network that regulates DC differentiation and function. During DC differentiation, the Irf8 gene locus shows high epigenetic dynamics, including histone modifications and TF binding identified by ChIP-seq (Chauvistré and Seré, 2020; Durai et al., 2019; Grajales-Reyes et al., 2015; Lin et al., 2015), chromatin accessibility measured by ATAC-seq (Kurotaki et al., 2019; Li et al., 2019), and three-dimensional chromatin structure remodeling determined by chromosome conformation capture (3 C) (Kurotaki et al., 2022; Schönheit et al., 2013). All this emphasizes the impact of epigenetic regulators on Irf8 gene activity in DC differentiation. Notably, Irf8 is flanked by multiple enhancers at –50 kb,+32 kb,+41 kb, and +56 kb that regulate Irf8 expression in hematopoietic cells (Anderson et al., 2021; Murakami et al., 2021). These four enhancers were found to be driven by PU.1, BATF3, E proteins and Runt-related transcription factor (RUNX)-core binding factor beta (CBFβ) (RUNX-CBFβ), respectively (Bagadia et al., 2019; Durai et al., 2019; Grajales-Reyes et al., 2015; Murakami et al., 2021; Schönheit et al., 2013). Chromatin conformation, particularly enhancer promoter interactions, provides a platform for TF-driven gene regulation and serves as a driving force for cell-fate determinations (Misteli and Finn, 2021; Oudelaar and Higgs, 2021; Stadhouders et al., 2019). Schönheit et al. demonstrated Irf8 promoter interactions with its upstream enhancers by quantitative 3 C (Schönheit et al., 2013). In this study PU.1 was found to regulate chromatin remodeling between the –50 kb enhancer and the Irf8 promoter in myeloid differentiation. In a recent study Kurotaki et al., 2022 determined the higher-order chromatin structure in DC progenitors, cDC1 and cDC2 on a genome-wide scale by Hi-C. In this study, reorganization of chromatin conformation at DC-specific gene loci was observed during cDC differentiation, and IRF8 was found to promote chromatin activation in DC progenitors leading to cDC lineage-specific gene expression. However, high resolution maps of the physical chromatin interactions of the Irf8 promoter with upstream and downstream enhancers in the full complement of DC subsets, including pDC, are required for understanding Irf8 regulation during DC differentiation. Frequently, chromatin data, including ATAC-seq and/or ChIP-seq data, are used to identify regulatory elements of gene transcription. Here we embarked on a different approach and searched for lncRNA, which by themselves might have regulatory functions or are indicative of enhancer activity. We identified a novel lncRNA transcribed from the Irf8 +32 kb enhancer, which is specifically expressed in pDC, referred to as lncIrf8. We found that the lncIrf8 promoter element but not lncIrf8 itself impacts pDC and cDC1 development. Thus, lncIrf8 acts as an indicator for the Irf8 +32 kb enhancer activity. Importantly, our study revealed a previously unrecognized negative feedback loop of Irf8 in DC differentiation. Irf8 first activates its expression by autoactivation via the +32 kb enhancer and second limits its own expression through the lncIrf8 promoter element in the +32 kb enhancer. Results lncIrf8 marks a pDC-specific Irf8 enhancer element Irf8 expression in DC development is subject to complex epigenetic regulation. Here, we used an integrated approach with RNA-seq, ATAC-seq, ChIP-seq and Capture-C to track the dynamics of gene expression, histone modification and chromatin conformation in the sequel MPP, CDP, pDC, cDC1, and cDC2 (Figure 1, Figure 1—figure supplements 1 and 2). Figure 1 with 3 supplements see all Download asset Open asset Irf8 epigenetic signatures and promoter-enhancer interaction maps during DC differentiation. (A) Gene expression and epigenetic signatures of Irf8 downstream region in MPP, CDP, pDC, all cDC, cDC1, and cDC2 are visualized by IGV browser. Gene expression was measured by RNA-seq, chromatin accessibility by ATAC-seq, H3K27ac and IRF8 binding by ChIP-seq. Positions of Irf8 3’ end, Irf8 enhancers, pDC specific lncIrf8 and cDC1 specific Tcons_00190258 lncRNA are indicated. For RNA-seq - and +strands are shown. Scale bar: 5 kb. (B) Physical interactions of Irf8 promoter with flanking sequences in MPP, CDP, pDC, cDC1, and cDC2 by nuclear-titrated (NuTi) Capture-C (turquoise), and CTCF binding by ChIP-seq in DC (Garber et al., 2012). Mean numbers of unique interactions normalized to a 300 kb region around the Irf8 promoter viewpoint (green triangle) and scaled by a factor of 1,000,000 are shown (n=2). The orientations of CTCF binding are indicated with blue and red arrows. Tcons_00190258 refers to the cDC1-specific lncRNA shown in (A). Scale bar: 100 kb. (C) Comparations of the chromatin interactions with Irf8 promoter in pDC, cDC1 and cDC2. Differential tracks were created by subtraction of the mean normalized tracks of (B). Pairwise comparisons are shown and color coded. Turquoise and orange tracks represent specific interactions with the Irf8 promoter in the indicated cell types. Scale bar: 100 kb. Purple bars and lines indicate the position of flanking enhancers relative to Irf8 TSS. The purple bars from left to right represent –50 kb, –34 kb, –26 kb, –16 kb,+27 kb,+32 kb,+38 kb,+41 kb,+47 kb,+56 kb and +62 kb enhancer, respectively (panels B and C). Irf8 +32 kb enhancer is highlighted by purple box. We performed de novo transcript assembly of the RNA-seq data and detected two previously unknown transcripts without coding potential downstream of Irf8: a pDC specific lncRNA (Tcons_00190250) in the following referred to as lncIrf8 and a cDC1 specific lncRNA (Tcons_00190258; Figure 1A and Figure 1—figure supplement 1). lncIrf8 and Tcons_00190258 show the same expression pattern in pDC and cDC1, respectively, in BM and spleen (Figure 1—figure supplement 3), as revealed by reanalyzing scRNA-seq and bulk RNA-seq data (Pang et al., 2022; Rodrigues et al., 2018). lncIrf8 is transcribed within an enhancer region located 32 kb downstream of the Irf8 TSS labeled by H3K27ac and H3K4me1 and occupied by DC differentiation-associated TF, such as IRF8 and PU.1 (Figure 1A and Figure 1—figure supplement 1). This region is largely devoid of H3K9me3, a chromatin modification frequently associated with heterochromatin, indicating an open chromatin configureuration in DC (Figure 1—figure supplement 1). In addition, sequences of this region have been implicated in DC development and referred to as +32 kb enhancer (Durai et al., 2019). Thus, we proceeded to study lncIrf8 in detail. ATAC-seq analysis revealed further details of the lncIrf8 region in CDP, pDC, cDC1 and cDC2 (Figure 1A, Figure 2A and Figure 1—figure supplement 1). In cDC1 the prominent ATAC-seq and IRF8 peaks mark the cDC1 specific +32 kb enhancer (Durai et al., 2019). In pDC the ATAC-seq peak is smaller and shifted further towards downstream but aligns well with the valley in the prominent H3K27ac peak. This ATAC-seq peak marks the lncIrf8 promoter and aligns with p300 (Durai et al., 2019) and H3K4me3 (Figure 2A and Figure 1—figure supplement 1). All this indicates that this chromatin region is open and transcriptionally active in pDC, enabling lncIrf8 transcription. Figure 2 with 4 supplements see all Download asset Open asset IncIrf8 promoter KO compromises pDC and cDC1 development in vitro. (A) Genomic anatomy of lncIrf8 locus determined by 3’ and 5’ RACE PCR. Blue box, exon 2 and 3 (48 bp and 468 bp, respectively). The 1010 bp intron and polyA tail are shown. Data of RNA-seq, ATAC-seq, ChIP-seq of H3K27ac (enhancer mark) and H3K4me3 (active promoter mark, near TSS) are visualized by IGV browser for the indicated cell populations (pDC, all cDC, cDC1 and cDC2). Grey box, lncIrf8 promoter KO region; open box, cDC1 specific +32 kb enhancer by Durai et al., 2019. Irf8 +32 kb enhancer based on the H3K27ac enhancer mark is indicated with a purple line. Scale bar: 1 kb. (B) Gene expression of lncIrf8 and Irf8 in lncIrf8 promoter KO and control at day 0, 5, and 7 of Flt3L directed DC differentiation. Gene expression was determined by RT-qPCR and normalized to GAPDH. n=4. (C) Representative flow cytometry analysis of Flt3L directed DC differentiation of lncIrf8 promoter KO HoxB8 MPP and control (Lutz et al., 2022; Xu et al., 2022). pDC, all cDC, cDC1, and cDC2 were gated as in Figure 2—figure supplement 1E and are shown. Bar diagrams depict quantification of pDC, cDC1 and cDC2 normalized to living single cells on DC differentiation day 0, 3, 5, 7, and 9. n=6–7. (D) Representative phase-contrast microscopy images of lncIrf8 promoter KO HoxB8 MPP and control on day 7 of Flt3L directed DC differentiation. Scale bar: 200 μm. (E) Representative flow cytometry analysis of spontaneous DC differentiation of lncIrf8 promoter KO HoxB8 MPP and control with growth factors but without E2 (Lutz et al., 2022; Xu et al., 2022) at day 8. Gr1+ monocytes and CD11c+ DC are shown. Quantification of Gr1+ monocytes of living single cells on day 3, 6, 8, and 10 of spontaneous DC differentiation. n=6, lncIrf8 promoter KO; n=4, control. Empty gRNA vector or non-targeting gRNA vector HoxB8 MPP were used as controls. Data represent mean ± SD of at least three independent experiments with different HoxB8 MPP clones of lncIrf8 promoter KO and control without deletion. *p<0.05, **p<0.01, ***p<0.001, multiple t-tests. Data that have no difference (p>0.05) are not labeled. Next, we determined the chromatin conformation of the Irf8 locus and the lncIrf8 region. We generated interaction profiles by nuclear-titrated (NuTi) Capture-C in MPP, CDP, pDC, cDC1, and cDC2 (Figure 1—figure supplement 2A and B) using Irf8 promoter as viewpoint. The Irf8 promoter shows multiple interactions with regions spanning up to ~100 kb upstream and downstream of Irf8 (Figure 1B and Figure 1—figure supplement 1). In pDC, the Irf8 promoter interactions are stronger with the upstream sequences than with downstream sequences (Figure 1C and Figure 1—figure supplement 2C). In cDC1 Irf8 promoter interactions are more confined to the regions downstream of Irf8 compared to MPP, CDP and pDC (Figure 1C and Figure 1—figure supplement 2C). This suggests that upstream and downstream sequences of Irf8 gene are involved in differentially regulating Irf8 expression and controlling the development of pDC and cDC1, respectively. The CCCTC-binding factor (CTCF) is important for regulation of chromatin conformation through loop extrusion (Sanborn et al., 2015) and we therefore visualized CTCF binding sites in the Irf8 locus in DC (Garber et al., 2012). Interestingly, most of the Irf8 flanking enhancers (Durai et al., 2019; Grajales-Reyes et al., 2015; Murakami et al., 2021; Schönheit et al., 2013) are located within convergent CTCF binding sites upstream and downstream of the Irf8 gene (Figure 1B and Figure 1—figure supplement 1). There are also multiple interactions within this region without convergent CTCF binding sites, suggesting interactions with Irf8 promoter in a CTCF independent manner, such as by TF binding, active histone modifications and gene transcription (Figure 1B and Figure 1—figure supplement 1; Owens et al., 2022). Surprisingly, in pDC H3K27ac at the lncIrf8 promoter is high, but this locus shows less interactions with the Irf8 promoter in pDC compared to CDP, cDC1 and cDC2 (Figure 1C and Figure 1—figure supplement 2C). In addition, in pDC the IRF8 protein occupancy at the lncIrf8 promoter is low and much higher in cDC (Figure 1A and Figure 1—figure supplement 1; Durai et al., 2019; Grajales-Reyes et al., 2015). These observations warrant further studies and we thus proceeded to investigate the lncIrf8 locus in detail. lncIrf8 promoter KO compromises pDC and cDC1 development First, we annotated lncIrf8. Our de-novo transcript assembly of RNA-seq data revealed different isoforms of lncIrf8, with the most prominent isoform comprising exon 2 and 3 (Figure 1A, Figure 2A and Figure 1—figure supplement 1). Additionally, 3' end and 5' end RACE PCR confirmed the anatomy of this lncIrf8 isoform: two exons, one intron, and a polyA tail (Figure 2A). As expected lncIrf8 is not conserved across species (data not shown), which is in line with the general characteristics of lncRNA. Then second, we deleted 300 bp in the lncIrf8 promoter by CRISPR/Cas9 editing in conditionally immortalized HoxB8 MPP (Figure 2A and Figure 2—figure supplement 1A–D). The lncIrf8 promoter is located in the Irf8 +32 kb enhancer region and is in close proximity to the cDC1 specific +32 kb enhancer (Durai et al., 2019; Figure 2A and Figure 2—figure supplement 2). The 300 bp deletion comprises the H3K4me3 promoter mark and is confined to open chromatin identified by ATAC-seq and positioned in the valley of the H3K27ac mark (Figure 2A). Additionally, it contains binding sites for IRF8, PU.1, and BATF3 TF, which are important for DC development (Figure 2A and Figure 2—figure supplement 2B). Generation of a precise deletion requires clonal cell populations, which is hardly achieved in somatic cells due to their limited lifespan. Therefore, we developed a Mx-Cas9-GFP system of conditionally immortalized HoxB8 MPP, which upon differentiation faithfully recapitulate DC development (Figure 2—figure supplement 1A, B; Xu et al., 2022). HoxB8 MPP were obtained from bone marrow of Mx-Cas9-GFP mice by infection with the estrogen (E2) inducible These MPP an and potential and into all DC subsets in and in et al., 2022). of gRNA lncIrf8 promoter in Mx-Cas9-GFP HoxB8 MPP and induction of by interferon generated lncIrf8 promoter KO of with were further studied and to DC differentiation (Figure Figure 2—figure supplement and Figure 2—figure supplement lncIrf8 promoter KO lncIrf8 expression during DC differentiation compared to control without deletion (Figure 2B). Surprisingly, Irf8 expression was also which points to a cross-talk of the lncIrf8 promoter element with the Irf8 lncIrf8 promoter KO also impacts DC subsets, CD11c+ pDC and cDC subsets cDC1 and cDC2 were (Figure and Figure 2—figure supplement of pDC and cDC1 were while cDC2 were (Figure 2C). lncIrf8 promoter KO cDC2 and some cells and were more compared to control without which multiple DC subsets (Figure and Figure 2—figure supplement lncIrf8 promoter KO also the differentiation of progenitors upon E2 from (Figure 1—figure supplement 2A and Figure 2—figure supplement lncIrf8 promoter KO a in cells compared to control (Figure 2—figure supplement lncIrf8 promoter KO higher of Gr1+ monocytes (Figure Figure 2—figure supplement and of all DC subsets CD11c+ pDC, cDC1, and cDC2 (Figure 2—figure supplement compared to control without deletion. The lncIrf8 promoter element is in close proximity to the cDC1 specific +32 kb enhancer previously in mice by Durai et al., and thus we generated the cDC1 specific +32 kb enhancer KO following the same as for the lncIrf8 promoter of clones with of cDC1 +32 kb enhancer were to DC differentiation and further (Figure 2—figure supplement to lncIrf8 promoter cDC1 specific +32 kb enhancer KO lncIrf8 expression and also Irf8 expression during DC differentiation (Figure 2—figure supplement The cDC1 +32 kb enhancer KO also the of cDC1 in Flt3L directed DC differentiation, while cDC2 were (Figure 2—figure supplement of pDC were also at day however, this was not These observations are in line with studies in mice that cDC1 +32 kb enhancer KO cDC1 differentiation and left pDC and cDC2 largely (Durai et al., 2019; Murakami et al., 2021). In addition, cDC1 +32 kb enhancer KO higher of Gr1+ monocytes upon spontaneous DC differentiation by of E2 (Figure 2—figure supplement and thus a as the lncIrf8 promoter KO upon spontaneous DC differentiation (Figure the novel of the lncIrf8 promoter we proceeded to investigate the impact of the lncIrf8 promoter KO on DC differentiation in in We lncIrf8 promoter KO and control HoxB8 MPP into mice (Figure supplement DC in bone marrow and spleen were by flow cytometry on day 7 and cell (Figure 3, Figure supplement 1A, In bone lncIrf8 promoter KO cells into Gr1+ and of all DC subsets were observed on day 7 for lncIrf8 promoter KO cells compared to control (Figure In of cell populations from lncIrf8 promoter KO and control were to bone including of all DC subsets for lncIrf8 promoter KO (Figure HoxB8 cells were largely at day cell (Figure and Figure Figure 3 with 1 supplement see all Download asset Open asset lncIrf8 promoter KO comprises pDC and cDC1 development in upon cell (A) Representative flow cytometry analysis of lncIrf8 promoter KO and control HoxB8 MPP in BM at day 7 cell details see Figure supplement 1A, cell populations were gated from cells and Gr1+ pDC, cDC1 and cDC2 are shown. Quantification of Gr1+ CD11c+ pDC, cDC1, and cDC2 of living single cells in BM on day 7 and cell Representative flow cytometry analysis of lncIrf8 promoter KO and control HoxB8 MPP in spleen at day 7 cell was as in (A). Quantification of Gr1+ CD11c+ pDC, cDC1 and cDC2 on day 7 and cell Data represent mean ± SD from 3 to 4 *p<0.05, **p<0.01, ***p<0.001, multiple t-tests. Data that have no difference (p>0.05) are not labeled. Thus, lncIrf8 promoter KO pDC and cDC1 development both in and in lncIrf8 acts as an indicator of Irf8 +32 kb enhancer activity in pDC of lncIrf8 promoter and thus of lncIrf8 expression pDC and cDC1 development in and in The lncIrf8 promoter is located within Irf8 +32 kb enhancer (Durai et al., 2019) and thus it was important to lncIrf8 itself a role in regulating pDC and cDC1 development. this we lncIrf8 in MPP and lncIrf8 in lncIrf8 promoter KO MPP and its impact on DC development (Figure 4 and Figure supplement 1). Figure 4 with 1 supplement see all Download asset Open asset lncIrf8 pDC and cDC1 development and B) of lncIrf8 in HoxB8 MPP and of and A polyA signal for transcription was at the 3’ end of lncIrf8 and (C) Gene expression of lncIrf8 and Irf8 in and HoxB8 MPP on day 0, 3, 5, and 7 of Flt3L directed DC differentiation Gene expression was by RT-qPCR and normalized to GAPDH. (D) Representative flow cytometry of DC subsets at day 5 and of Flt3L directed DC differentiation of and HoxB8 Quantification of pDC and cDC1 of living single cells on Flt3L directed DC differentiation day 0, 3, 5, 7, and is shown. for pDC and cDC1 was as in Figure 2—figure supplement (E) of DC subsets of (D) at day 0, 3, 5, 7, and of DC differentiation. high and low Data represent mean ± SD of at least three independent experiments with different HoxB8 MPP clones of and *p<0.05, **p<0.01, ***p<0.001, multiple t-tests. Data that have no difference (p>0.05) are not labeled. lncIrf8 was into a polyA An signal et al., 2015) was at the 3’ end of lncIrf8 to avoid transcripts than lncIrf8 Figure The vector was used as control. lncIrf8 clones were generated by (Figure supplement and to DC differentiation. As expected lncIrf8 expression was in cells compared to while there were no in Irf8 expression between the two during DC differentiation (Figure there were no in the of pDC, cDC1, and cDC2 between cells and controls (Figure and Figure supplement indicating that lncIrf8 no on Irf8 expression and DC differentiation. further this we performed a lncIrf8 in lncIrf8 promoter KO lncIrf8 was in lncIrf8 promoter KO MPP by vector and cells were to DC differentiation (Figure supplement lncIrf8 RNA was expressed and cells in response to Flt3L

Chronic Ethanol Consumption Impairs Cellular Immune Responses Against HCV NS5 Protein Due to Dendritic Cell Dysfunction

Sex differences in cancer susceptibility and mortality are well documented. In general, men have a higher cancer incidence and poorer outcomes when compared to women. Of immunologic relevance, and in contrast to cancer, women account for almost 80% of the autoimmune cases reported. These findings suggest male sex is a ‘risk factor’ for cancer but protective against autoimmunity and also highlight the potential involvement of sex hormones in regulating the immune response. Several recent publications have put a spotlight on androgen-mediated immune regulation and its impact on anti-tumor immunity. Guan and colleagues demonstrated that blockade of sex hormones in prostate tumor-bearing mice resulted in improved adaptive immune responses via direct modulation of CD8+ T cell-intrinsic androgen receptor signaling. Androgen-deprivation led to increased interferon gamma (IFNγ) expression by T cells and improved overall anti-tumor immunity. Additionally, others have shown using non-reproductive cancer mouse models (melanoma, bladder, colon and liver) that androgen receptor signaling promotes T cell exhaustion, and inhibits the activity and stemness of anti-tumor CD8+ T cells. Importantly, there is a clear role for androgen-mediated immune regulation in non-reproductive human cancer given a recent publication showing improved progression-free survival and overall survival in female versus male melanoma patients who were treated with neoadjuvant BRAF/MEK-targeted therapy. Follow-up preclinical mouse models showed significantly higher expression of the androgen receptor in tumors of both male and female BRAF/MEK-treated mice versus control and pharmacological inhibition of androgen receptor signaling improved responses to BRAF/MEK-targeted therapy in both male and female mice. Taken together, these publications stress the importance of understanding androgen-mediated immune control in both male and female cancer patients and the broad applicability of this signaling pathway in tissues including, but also beyond, the reproductive tract. There is mounting evidence to support a role androgen signaling in T cell biology. However, professional antigen presenting cells such as dendritic cells (DCs) are an essential part of generating robust anti-tumor T cell immunity were not addressed in these studies. Notably, DCs have been reported to be sensitive to androgens. Castration studies in mice found that removal of testosterone increased antigen presentation and expression of co-stimulatory molecules on DCs. In addition, hypogonadal men are at elevated risk of developing autoimmunity. Isolation of DCs from these patients showed a significant increase in DC maturation. HIV infected DCs derived from males produced significantly less type I interferon compared to female patients, resulting in weaker CD8 T cell responses against the virus. These data establish that androgens can shape DC function, yet they fall short in identifying the mechanisms of how androgens regulate DCs and the impact this may have on anti-tumor immunity. In our initial interrogation of a single-cell RNA sequencing dataset of human prostate cancer patients, we found that human tumors with low androgen receptor activity had increased IFNγ pathway activity and that IFNγ activity was positively associated with an increase in antigen presentation. Importantly, IFNγ is a cytokine that strongly induces antigen processing and presentation by antigen presenting cells and androgen deprivation therapy increases T cell derived IFNγ in tumor bearing mice suggesting that androgen receptor activity may also regulate antigen presentation. Furthermore, our analysis showed that elevated androgen receptor activity correlated with lower antigen presentation, conceivably through suppression of DC function. We hypothesized that inhibition of androgen receptor-mediated suppression of DC function would improve antigen presentation and anti-tumor T cell responses. Here we demonstrate using a B16 melanoma model that male and female DCs, both bone marrow-derived and those sorted from murine steady-state skin and melanoma tumors, express androgen receptor. Interestingly, there is a striking upregulation of androgen receptor expression specifically on type 1 conventional DCs (cDC1s) following uptake of tumor-derived antigen in vivo. cDC1s are a subset of DC that is particularly specialized in cross-presentation of exogenous antigens on MHCI. In this way, cDC1s are dominant drivers of CD8+ T cell responses and, via this function, have been shown to be essential for anti-tumor immunity. Further by inhibiting androgen receptor signaling in vitro using the clinically relevant inhibitor, enzalutamide, we find that bone marrow-derived DCs have increased phagocytic activity as shown by fluorescent bead uptake. Next, we injected male mice with B16 melanoma tumors and, after allowing the tumors to establish, we treated them with degarelix to reduce testosterone levels and enzalutamide to further inhibit androgen receptor signaling. On day 15 we sacrificed the mice, measured the tumors and interrogated DC function by flow cytometry. Strikingly, we found that inhibition of androgen receptor signaling in vivo significantly increased tumor-derived antigen uptake by cDC1s and, importantly, this correlated with improved tumor control as seen by significantly smaller tumors upon androgen receptor inhibition. These data provide insight into the regulation of DCs within the tumor microenvironment and how suppressing inhibitory hormone molecules may lead to better antigen presentation and more effective downstream T cell responses. Cancer immunotherapy is designed to generate an autoimmune-like response against an individual’s cancer. Given the striking sexual dimorphism in both autoimmunity and cancer, there is a clear and pressing need to investigate the impact of sex hormones on the effectiveness and function of cancer immunotherapy. And while myeloid cell targeted therapies and DC-based anti-tumor vaccines hold great promise for boosting anti-tumor T cells responses, current clinical use and efficacy has been limited pointing to an urgent need for improved vaccine and therapeutic design. This will rely on a better understanding of DC activation in this context. Our data indicates that there is a role for androgen receptor signaling in DC function and highlights the potential impact of DC-intrinsic androgen receptor inhibition on optimal DC vaccine design and the generation of more productive DC targeted immunotherapies. Citation Format: Kasidy Brown, Fanny Polesso, Victoria Schuster, Amy Moran, Megan Ruhland. Dendritic cell intrinsic androgen receptor signaling reduces dendritic cell function and anti-tumor immunity. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr NG01.

Mouse splenic dendritic cell (DC) subsets possess distinct antigen-presentation abilities. CD8(+) DC are specialized in cross-presentation of antigens to CD8(+) T cells, whereas CD8(-) DC are more efficient in antigen presentation to CD4(+) T cells. In this study, we examined the capacity of CD8(+) and CD8(-) DC subsets to present fungal antigens in MHC class I and II molecules to CD8(+) and CD4(+) T cells, respectively. We used ovalbumin-expressing Saccharomyces cerevisiae (yeast-OVA) as a fungal model system. Both CD8(+) and CD8(-) DC subsets phagocytosed yeast in equal amounts and uptake was mediated via dectin-1. In addition, both DC subsets induced similar OVA-specific CD4(+) T cell proliferation after incubation with yeast-OVA. However, the induction of OVA-specific CD8(+) T cell activation was largely restricted to the CD8(-) DC subset. Furthermore, only CD8(-) DC produced cytokines such as IL-10 and TNF-alpha and increased IL-23p19 and IL-23p40 mRNA levels in response to yeast. Our results strongly suggest that DC subsets have different functions in the elicitation of adaptive immune responses in vivo.

Dendritic cells (DCs) are antigen-presenting cells essential for the induction of adaptive immune responses. Their unprecedented ability to present antigens to T cells has made them excellent targets for vaccine development. In the last years, a new technology based on antigen delivery directly to different DC subsets through the use of hybrid monoclonal antibodies (mAbs) to DC surface receptors fused to antigens of interest opened new perspectives for the induction of robust immune responses. Normally, the hybrid mAbs are administered with adjuvants that induce DC maturation. In this work, we targeted an antigen to the CD8α+ or the CD8α− DC subsets in the presence of CpG oligodeoxinucleotides (ODN) or bacterial flagellin, using hybrid αDEC205 or αDCIR2 mAbs, respectively. We also accessed the role of toll-like receptors (TLRs) 5 and 9 signaling in the induction of specific humoral and cellular immune responses. Wild-type and TLR5 or TLR9 knockout mice were immunized with two doses of the hybrid αDEC205 or αDCIR2 mAbs, as well as with an isotype control, together with CpG ODN 1826 or flagellin. A chimeric antigen containing the Plasmodium vivax 19 kDa portion of the merozoite surface protein (MSP119) linked to the Pan-allelic DR epitope was fused to each mAb. Specific CD4+ T cell proliferation, cytokine, and antibody production were analyzed. We found that CpG ODN 1826 or flagellin were able to induce CD4+ T cell proliferation, CD4+ T cells producing pro-inflammatory cytokines, and specific antibodies when the antigen was targeted to the CD8α+ DC subset. On the other hand, antigen targeting to CD8α− DC subset promoted specific antibody responses and proliferation, but no detectable pro-inflammatory CD4+ T cell responses. Also, specific antibody responses after antigen targeting to CD8α+ or CD8α− DCs were reduced in the absence of TLR9 or TLR5 signaling, while CD4+ T cell proliferation was mainly affected after antigen targeting to CD8α+ DCs and in the absence of TLR9 signaling. These results extend our understanding of the modulation of specific immune responses induced by antigen targeting to DCs in the presence of different adjuvants. Such knowledge may be useful for the optimization of DC-based vaccines.

Dendritic cells (DC) are the only antigen-presenting cells that can activate naïve T lymphocytes and initiate a primary immune response. They are also thought to have a role in immune tolerance. DC traffic from the blood to peripheral tissue where they become activated. They then present antigen and the costimulating signals necessary to initiate an immune response. In this study, we investigated the number, subsets, and activation pattern of circulating and intestinal DC from patients with clinically mild ulcerative colitis (UC) or Crohn's disease. Patients were recruited, if they were not taking immunosuppressive therapy, and were assessed for clinical severity of their disease using for UC, the Clinical Activity Index, and for Crohn's disease, the Crohn's Disease Activity Index. Blood CD11c+ and CD11c- DC subsets, expression of costimulatory antigens, CD86 and CD40, and the early differentiation/activation antigen, CMRF44, were enumerated by multicolor flow cytometry of lineage negative (lin- = CD3-, CD19-, CD14-, CD16-) HLA-DR+ DC. These data were compared with age-matched healthy and the disease control groups of chronic noninflammatory GI diseases (cGI), acute noninflammatory GI diseases (aGI), and chronic non-GI inflammation (non-GI). In addition, cryostat sections of colonoscopic biopsies from healthy control patients and inflamed versus noninflamed gut mucosa of inflammatory bowel disease (IBD) patients were examined for CD86+ and CD40+ lin- cells. Twenty-one Crohn's disease and 25 UC patients, with mean Crohn's Disease Activity Index of 98 and Clinical Activity Index of 3.1, and 56 healthy controls, five cGI, five aGI, and six non-GI were studied. CD11c+ and CD11c- DC subsets did not differ significantly between Crohn's, UC, and healthy control groups. Expression of CD86 and CD40 on freshly isolated blood DC from Crohn's patients appeared higher (16.6%, 31%) and was significantly higher in UC (26.6%, 46.3%) versus healthy controls (5.5%, 25%) (p = 0.004, p = 0.012) and non-GI controls (10.2%, 22.8%) (p = 0.012, p = 0.008), but not versus cGI or aGI controls. CD86+ and CD40+ DC were also present in inflamed colonic and ileal mucosa from UC and Crohn's patients but not in noninflamed IBD mucosa or normal mucosa. Expression of the CMRF44 antigen was low on freshly isolated DC, but it was upregulated after 24-h culture on DC from all groups, although significantly less so on DC from UC versus Crohn's or healthy controls (p = 0.024). The CMRF44+ antigen was mainly associated with CD11c+ DC, and in UC was inversely related to the Clinical Activity Index (r = -0.69, p = 0.0002). There is upregulation of costimulatory molecules on blood DC even in very mild IBD but surprisingly, there is divergent expression of the differentiation/activation CMRF44 antigen. Upregulation of costimulatory molecules and divergent expression of CMRF44 in blood DC was also apparent in cGI and aGI but not in non-GI or healthy controls, whereas intestinal CD86+ and CD40+ DC were found only in inflamed mucosa from IBD patients. Persistent or distorted activation of blood DC or divergent regulation of costimulatory and activation antigens may have important implications for gut mucosal immunity and inflammation.

Allergic asthma has been mainly attributed to T helper type 2 (Th2) and proinflammatory responses but many cellular processes remain elusive. There is increasing evidence for distinct roles for macrophage and dendritic cell (DC) subsets in allergic airway inflammation (AAI). At the same time, there are various mouse models for allergic asthma that have been of utmost importance in identifying key inflammatory pathways in AAI but that differ in the allergen and/or route of sensitization. It is unclear whether and how the accumulation and activation of specialized macrophage and DC subsets depend on the experimental model chosen for analyses. In our study, we employed high-parameter spectral flow cytometry to comprehensively assess the accumulation and phenotypic alterations of different macrophage- and DC-subsets in the lung in an OVA- and an HDM-mediated mouse model of AAI. We observed subset-specific as well as model-specific characteristics with respect to cell numbers and functional marker expression. Generally, alveolar as opposed to interstitial macrophages showed increased MHCII surface expression in AAI. Between the models, we observed significantly increased numbers of alveolar macrophages, CD103+ DC and CD11b+ DC in HDM-mediated AAI, concurrent with significantly increased airway interleukin-4 but decreased total serum IgE levels. Further, increased expression of CD80 and CD86 on DC was exclusively detected in HDM-mediated AAI. Our study demonstrates a model-specific involvement of macrophage and DC subsets in AAI. It further highlights spectral flow cytometry as a valuable tool for their comprehensive analysis under inflammatory conditions in the lung.

Food allergy affects approximately 6% of children and is the leading cause of hospitalization for anaphylactic reactions in westernized countries. Crucial in the establishment of allergy is the activation of dendritic cells (DC) leading to T helper 2-mediated responses. We, therefore, investigated whether changes in DC subsets precede the establishment of food allergy, and which DC subsets have functional relevance during allergic sensitization in a mouse model. Changes in DC populations in the intestine were analysed after exposure to cholera toxin alone and in combination with peanut extract (PE) as an allergen. To study the functional role of DC subsets in relation to food allergy, we used expansion of DC in vivo by treatment with Flt3L. Sensitization to PE in this mouse model was accompanied by a shift in DC subsets in intestinal tissues towards more CD11b(+) DC and less CD103(+) DC. No significant changes in the plasmacytoid DC (pDC) numbers were observed. Flt3L treatment, resulting in the expansion of all DC subtypes, inhibited allergic manifestations in our model, including Th2 cytokine production, PE-specific IgE and PE-induced mast cell degranulation. pDC depletion reversed Flt3L-induced inhibition of IgE responses and mast cell degranulation. conclusions and clinical relevance: The establishment of food allergy is accompanied by profound changes in DC subsets in the intestine towards more inflammatory CD11b(+) DC. In addition, expansion of DC numbers by Flt3L, in particular pDC, inhibits the establishment of allergic manifestations in the intestine. These findings are of relevance for understanding the role of DC subsets early during the process of allergic sensitization, and may lead to new therapeutic or prophylactic opportunities to prevent food allergy.

The cytokine thymic stromal lymphopoietin (TSLP) is produced by epithelia exposed to the contact sensitizer dibutyl phthalate (DBP), and it is critical for the induction of Th2 immune responses by DBP-FITC. TSLP is thought to act on dendritic cells (DC), but the precise DC subsets involved in the response to TSLP remain to be fully characterized. In this study we show that a subset of CD326(lo)CD103(lo)CD11b(lo) dermal DC, which we termed "triple-negative (TN) DC," is highly responsive to TSLP. In DBP-FITC-treated mice, TN DC upregulated expression of CD86 and rapidly migrated to the draining lymph node to become the most abundant skin-derived DC subset at 24 and 48 h after sensitization. None of these responses was observed in TSLPR-deficient mice. In contrast, TN DC numbers were not increased after treatment with the allergen house dust mite or the bacteria Escherichia coli and bacillus Calmette-Guérin, which increased other DC subsets. In vivo, treatment with rTSLP preferentially increased the numbers of TN DC in lymph nodes. In vitro, TN DC responded to rTSLP treatment with a higher level of STAT5 phosphorylation compared with other skin-derived DC subsets. The TN DC subset shared the morphology, phenotype, and developmental requirements of conventional DC, depending on FLT3 expression for their optimal development from bone marrow precursors, and CCR7 for migration to the draining lymph node. Thus, TN DC represent a dermal DC subset that should be considered in future studies of TSLP-dependent contact sensitization and skin immune responses.

Epigenetic Regulation Of Dendritic Cell Migration

&lt;div&gt;Abstract&lt;p&gt;Melanoma exerts immune-suppressive effects to facilitate tumor progression and metastatic spread. We studied these effects on dendritic cell (DC) and T-cell subsets in 36 melanoma sentinel lymph node (SLN) from 28 stage I–III melanoma patients and determined their clinical significance. Four conventional DC subsets, plasmacytoid DCs, and CD4&lt;sup&gt;+&lt;/sup&gt;, CD8&lt;sup&gt;+&lt;/sup&gt;, and regulatory T cells (Tregs), were analyzed by flow cytometry. We correlated these data to clinical parameters and determined their effect on local and distant melanoma recurrence, with a median follow-up of 75 months. In stage I and II melanoma, increased Breslow thickness (i.e., invasion depth of the primary melanoma) was associated with progressive suppression of skin-derived migratory CD1a&lt;sup&gt;+&lt;/sup&gt; DC subsets. In contrast, LN-resident DC subsets and T cells were only affected once metastasis to the SLN had occurred. In stage III patients, increased CD4:CD8 ratios in concert with the accumulation of Tregs resulted in decreased CD8:Treg ratios. On follow-up, lower frequencies of migratory DC subsets proved related to local melanoma recurrence, whereas reduced maturation of LN-resident DC subsets was associated with distant recurrence and melanoma-specific survival. In conclusion, melanoma-mediated suppression of migratory DC subsets in the SLN precedes local spread, whereas suppression of LN-resident DC subsets follows regional spread and precedes further melanoma dissemination to distant sites. This study offers a rationale to target migratory as well as LN-resident DC subsets for early immunotherapeutic interventions to prevent melanoma recurrence and spread. &lt;i&gt;Cancer Immunol Res; 5(11); 969–77. ©2017 AACR&lt;/i&gt;.&lt;/p&gt;&lt;/div&gt;

Dendritic cells (DCs) are a heterogeneous population of professional antigen-presenting cells which play a key role in orchestrating immune defenses. Most of the information gained on human DC biology was derived from studies conducted with DCs generated in vitro from peripheral blood CD14(+) monocytes (MoDCs) or from CD34(+) hematopoietic progenitors. Recent advances in the field revealed that these types of in vitro-derived DCs strikingly differ from the DC subsets that are naturally present in human lymphoid organs, in terms of global gene expression, of specialization in the sensing of different types of danger signals, and of the ability to polarize T lymphocytes toward different functions. Major efforts are being made to better characterize the biology and the functions of lymphoid organ-resident DC subsets in humans, as an essential step for designing innovative DC-based vaccines against infections or cancers. However, this line of research is hampered by the low frequency of certain DC subsets in most tissues, their fragility, and the complexity of the procedures necessary for their purification. Hence, there is a need for robust procedures allowing large-scale in vitro generation of human DC subsets, under conditions allowing their genetic or pharmacological manipulation, to decipher their functions and their molecular regulation. Human CD141(+)CLEC9A(+)XCR1(+) DCs constitute a very interesting DC subset for the design of immunotherapeutic treatments against infections by intracellular pathogens or against cancer, because these cells resemble mouse professional cross-presenting CD8α(+)Clec9a(+)Xcr1(+) DCs. Human XCR1(+) DCs have indeed been reported by several teams to be more efficient than other human DC subsets for cross-presentation, in particular of cell-associated antigens but also of soluble antigens especially when delivered into late endosomes or lysosomes. However, human XCR1(+) DCs are the rarest and perhaps the most fragile of the human DC subsets and hence the most difficult to study ex vivo. Here, we describe a protocol allowing simultaneous in vitro generation of human MoDCs and XCR1(+) DCs, which will undoubtedly be extremely useful to better characterize the functional specialization of human XCR1(+) DCs and to identify its molecular bases.