Epigenetic Control of Ccr7 Expression in Distinct Lineages of Lung Dendritic Cells

Timothy P. Moran, Hideki Nakano, Hrisavgi D. Kondilis-Mangum, Paul A. Wade and Donald N. Cook
J Immunol November 15, 2014, 193 (10) 4904-4913; DOI: https://doi.org/10.4049/jimmunol.1401104

Abstract

Adaptive immune responses to inhaled allergens are induced following CCR7-dependent migration of precursor of dendritic cell (pre-DC)–derived conventional DCs (cDCs) from the lung to regional lymph nodes. However, monocyte-derived (moDCs) in the lung express very low levels of Ccr7 and consequently do not migrate efficiently to LN. To investigate the molecular mechanisms that underlie this dichotomy, we studied epigenetic modifications at the Ccr7 locus of murine cDCs and moDCs. When expanded from bone marrow precursors, moDCs were enriched at the Ccr7 locus for trimethylation of histone 3 lysine 27 (H3K27me3), a modification associated with transcriptional repression. Similarly, moDCs prepared from the lung also displayed increased levels of H3K27me3 at the Ccr7 promoter compared with migratory cDCs from that organ. Analysis of DC progenitors revealed that epigenetic modification of Ccr7 does not occur early during DC lineage commitment because monocytes and pre-DCs both had low levels of Ccr7-associated H3K27me3. Rather, Ccr7 is gradually silenced during the differentiation of monocytes to moDCs. Thus, epigenetic modifications of the Ccr7 locus control the migration and therefore the function of DCs in vivo. These findings suggest that manipulating epigenetic mechanisms might be a novel approach to control DC migration and thereby improve DC-based vaccines and treat inflammatory diseases of the lung.

Introduction

The migration of lung dendritic cells (DCs) to lymph nodes (LN) is critical for orchestrating adaptive immune responses against inhaled Ags or microbes (1–4). Mobilization of lung DCs to LN is dependent on the chemokine receptor CCR7 and its ligands, CCL19 and CCL21, which are produced in afferent lymphatic vessels and the T cell zones of LN (5). Under homeostatic conditions, CCR7-dependent migration of lung DCs to draining LN is important for the induction of regulatory T cells, which help maintain peripheral tolerance to innocuous environmental Ags (6). During infection or other inflammatory insults, migratory DCs become licensed to induce cytotoxic T cells or effector Th cell differentiation (7). These effector T cells not only assist with pathogen clearance but can also mediate maladaptive immune responses leading to inflammatory lung diseases such as asthma (3, 4, 8). Because migratory DCs play a central role in shaping immune responses in the lungs, manipulating Ccr7 expression is a potential strategy for either augmenting or suppressing adaptive immunity. However, such a strategy requires an improved understanding of the molecular mechanisms responsible for regulating Ccr7 expression.

As in other nonlymphoid tissues, DCs in the lungs are composed of two major lineages: conventional DCs (cDCs) and monocyte-derived DCs (moDCs) (9, 10). Lung cDCs arise from circulating progenitor cells referred to as precursor of DCs (pre-DC), which descend from the common DC progenitor in the bone marrow (BM) via a pathway dependent on Flt3 ligand (FL) (11). In contrast, lung-resident moDCs develop from emigrating peripheral blood monocytes independently of FL (10). There is growing evidence that DC functional specialization is dependent on their developmental lineage (12). In agreement with this, we recently reported that lung cDCs and moDCs differ significantly in their ability to express Ccr7 and migrate to regional LN (10). During steady-state conditions, Ccr7 is expressed at low levels in lung cDCs and is markedly upregulated by microbial products, such as LPS and polyinosinic:polycytidylic acid [poly (I:C)]. By contrast, moDCs in the lung fail to express Ccr7, even after treatment with these microbial products. Consequently, cDCs, but not moDCs can efficiently ferry Ag from the lung to regional LN. These findings are in agreement with studies showing that moDCs from other peripheral tissues, such as the skin and gut, also express low levels of Ccr7 and migrate poorly to LN (13, 14). Taken together, these studies suggest that the capacity for peripheral DCs to express Ccr7 and migrate to LN is regulated in a lineage-specific manner.

The unique transcriptional profiles of DC subsets are likely important for dictating their functional and migratory properties. Although the transcriptomes of DC subsets are clearly dependent on lineage-specific transcription factors (15), epigenetic mechanisms are also essential for regulating gene expression during DC development (16). Epigenetic mechanisms, which include DNA methylation and posttranslational modifications of histone tails, regulate gene expression by governing chromatin accessibility to the transcriptional machinery (17). Although epigenetic modifications of multiple genes have been well studied in the context of Th cell differentiation (18–20), remarkably little is known of epigenetic mechanisms that might be expected to influence DC development or function (16). In the current study, we investigated whether epigenetic modifications at the Ccr7 locus influence the migratory properties of different DC subsets. We found that moDCs have increased repressive histone modifications at the Ccr7 locus, which was associated with decreased Ccr7 expression and a nonmigratory phenotype. Surprisingly, these repressive epigenetic marks are not established during lineage commitment within the BM but rather during monocyte differentiation into moDCs in peripheral tissues. Our findings suggest that epigenetic modifications at the Ccr7 locus closely correlate with the migratory properties, and hence the functional roles, of nonlymphoid DC subsets. The transcriptional silencing of Ccr7 during moDC differentiation might also have implications for the development of effective DC-based vaccines for immunotherapy.

Materials and Methods

Mice

C57BL/6J and OT-II (C57BL/6-Tg(TcraTcrb)425Cbn/J) mice were purchased from The Jackson Laboratory (Bar Harbor, ME). Ccr7gfp reporter mice were generated in our laboratory and have been described previously (10). Mice were housed in specific pathogen-free conditions at the National Institute of Environmental Health Sciences (NIEHS) and used between 6 and 12 wk of age in accordance with guidelines provided by the Institutional Animal Care and Use Committees.

Flow cytometric analysis

Cells were incubated with a nonspecific-binding blocking reagent mixture of anti-mouse CD16/CD32 (2.4G2) and normal mouse and rat serum (Jackson ImmunoResearch Laboratories, West Grove, PA) for 5 min. For staining of surface Ags, cells were incubated with fluorochrome (allophycocyanin, allophycocyanin-Cy7, Alexa Fluor 488, Alexa Fluor 647, eFluor 450, eFluor 605 NC, FITC, PerCP-Cy5.5, or PE) or biotin-conjugated Abs against mouse CD3ε (145-2C11), CD11b (M1/70), CD11c (N418), CD14 (Sa2-8), CD19 (6D5), CD40 (1C10), CD49b (DX5), CD86 (GL1), CD88 (20/70), CD103 (M290), CD115 (AFS98), CD135 (A2F10), F4/80 (BM8), Ly-6C (AL-21), Ly-6G (1A8), MHC class II I-Ab (AFb.120), Sca-1 (D7), and TER-119 (BD Biosciences [San Jose, CA], BioLegend [San Diego, CA], and eBioscience [San Diego, CA]). Staining with biotinylated Abs was followed by fluorochrome-conjugated streptavidin. Stained cells were analyzed on a five-laser LSRII (BD Biosciences) or sorted on a five-laser ARIA-II flow cytometer (BD Biosciences), and the data were analyzed using FACS Diva (BD Bioscience) and FlowJo (Treestar, Ashland, OR) software. Dead cells were excluded based on their forward and side scatter or uptake of 7-aminoactinomycin D. Only single cells were analyzed.

Generation and analysis of BM-elicited DCs

Marrow was collected from pulverized bones, and RBCs were lysed with 0.15 M ammonium chloride and 1 mM potassium bicarbonate. BM cells were then cultured in complete RPMI 1640 medium (RPMI 1640, 10% FBS [Gemini, West Sacramento, CA], penicillin/streptomycin, and 50 ng ml−1 2-ME) supplemented with either 100 ng ml−1 recombinant human FL to generate FL-DCs or 5 ng ml−1 GM-CSF and IL-4 (R&D Systems, Minneapolis, MN) to generate GM-DCs. Recombinant human FL was produced by the NIEHS Protein Expression Core Facility using previously described methods (21). Media was replaced every 3 d, at which time fresh cytokines were also added. In some experiments 100 ng ml−1 LPS (Sigma-Aldrich, St. Louis, MO) or 10 μg ml−1 poly(I:C) (InvivoGen, San Diego, CA) was added during the last 24 h of culture to induce DC maturation. Cells were harvested on day 8 and stained with biotinylated anti-CD11c Ab (eBioscience), followed by incubation with streptavidin Microbeads (Miltenyi, Auburn, CA), and finally isolated with an automated magnet-activated cell sorter to a purity of >90% CD11c+ cells. To assay T cell stimulating activity, BM-derived DCs were purified using MACS and then cultured with naive CD4+ OT-II cells (DC:T cell ratio = 1:2) in the presence of 10 nM OVA323–339 peptide (New England Peptide, Gardner, MA) as described previously (8). Proliferation was inferred from recovery of viable (trypan blue negative) T cells after 5 d of coculture. In some experiments, DCs were centrifuged onto glass slides and photographed using an Olympus BX51 microscope, DP70 digital camera, and DP software (Olympus, Center Valley, PA).

Preparation and analysis of lung DCs subsets

Lung DC subsets were isolated and purified by flow cytometry-based sorting as described previously (22). To induce activation of lung DCs in vivo, mice were anesthetized by isoflurane inhalation and given 0.1 μg LPS by oropharyngeal aspiration 16 h prior to lung DC isolation. In some experiments, purified DC subsets were cultured in complete RPMI 1640 medium containing 100 ng ml−1 LPS.

Purification of monocytes and pre-DCs from BM

Ly-6Chi monocytes (CD3−CD11b+CD11c−CD19−CD49b−CD115+F4/80hiI-A−Ly-6ChiLy-6G−Sca-1−TER119−) or pre-DCs (CD3−CD11b−CD11c+CD19−CD49b−I-A−CD135+Ly-6G−Sca-1−TER119−) from BM were enriched by MACS and then further purified by flow cytometry–based sorting. In some experiments, Ly-6Chi monocytes were cultured in complete RPMI 1640 medium supplemented with 5 ng ml−1 GM-CSF and IL-4 to generate moDCs. Culture medium was changed every 3 d with fresh cytokines added at that time.

Chemotaxis assays

LPS-matured, CD11c+ BM-elicited DCs (2 × 105) were added to the upper chamber of a Transwell insert (Corning, Corning, NY) with a 5 μm polycarbonate membrane. Various concentrations of CCL19 (R&D) were added to the bottom chamber. After a 2 h incubation at 37°C, migrated cells were collected from the bottom chamber and enumerated by flow cytometry using Accucount Beads (Spherotech, Lake Forest, IL) per the manufacturer’s instructions.

cDNA amplification and analysis

Total RNA was isolated from cells using an RNeasy kit (Qiagen, Valencia, CA) or TRIzol reagent (Life Technologies) and converted to cDNA with oligo dT and random hexamer primers using murine leukemia virus reverse transcriptase (Life Technologies, Grand Island, NY). PCR amplification was performed using primers listed in Supplemental Table I with Power SYBR Green PCR Master Mix (Life Technologies) and an Mx3000P quantitative PCR (QPCR) system (Agilent Technologies, Santa Clara, CA). The efficiency-corrected ΔCt for each gene was determined and normalized to Gapdh expression.

Chromatin immunoprecipitation

Native chromatin was prepared from cells by small-scale micrococcal nuclease digestion as previously described with modification (23). Briefly, CD11c+ BM-elicited DCs (4 × 106) or sorted lung DCs (0.2–1 × 106) were washed and incubated in lysis buffer containing 0.4% Nonidet P-40 for 10 min on ice. Nuclei were then washed and resuspended in digestion buffer containing 25 U/ml micrococcal nuclease (Worthington Biochemical, Lakewood, NJ) and incubated at 37°C for 5 min to generate mono- and dinucleosomes. The reaction was stopped by addition of 10 mM Tris-HCl (pH 8), 5 mM EDTA, and 10 mM sodium butyrate, and samples were incubated overnight at 4°C. After centrifugation, the supernatant was harvested and Triton X-100 was added to a concentration of 1% (v/v). For BM-elicited DC samples, chromatin was precleared with protein A–Sepharose/salmon sperm DNA (EMD Millipore, Billerica, MA) and then incubated overnight at 4°C with 2.5 μg of either anti-trimethylated H3 lysine 27 (anti-H3K27me3; Active Motif, Carlsbad, CA), anti-acetylated H3 lysine 27 (anti-H3K27ac; Active Motif), or nonspecific anti-rabbit IgG Ab (Santa Cruz Biotechnology, Dallas, TX). After incubation with protein A–Sepharose/salmon sperm DNA for 1 h, immunoprecipitates were washed vigorously, and DNA was purified. For lung DC samples, chromatin was immunoprecipitated with the above Abs using the MAGnify ChIP System (Life Technologies) per the manufacturer’s instructions. Bound and input fractions were quantified by QPCR using an MxP3000p QPCR system (Agilent Technologies) with Power SYBR Green PCR Master Mix (Life Technologies) and PCR primers listed in Supplemental Table I. PCR conditions were as follows: 10 min at 95°C; 15 s at 95°C and 60 s at 62°C for 40 cycles; and dissociation curve analysis to verify specific PCR product labeling. Analysis was performed using the efficiency-corrected ΔCt method, with amplification efficiency determined from a standard curve that was generated from genomic DNA. Data are presented as the signal from bound fractions normalized to the input fraction.

Statistics

Data are expressed as mean ± SD or SEM as indicated. Statistical differences between groups were calculated using a two-tailed Student t test, unless indicated otherwise. A p value < 0.05 was considered significant.

Results

BM-elicited conventional DCs, but not moDCs, express functional CCR7

Lung DCs are rare compared with many other cell types in that organ. Accordingly, we first used different culture conditions to generate cDCs and moDCs from BM progenitors ex vivo (Fig. 1A) (24). Because FL is required for cDC development, we cultured BM progenitors in the presence of this cytokine to generate cDCs (FL-DCs). To generate moDCs, we cultured progenitors with GM-CSF and IL-4 (GM-DCs). Light microscopic and flow cytometric analyses revealed that both cultures contained CD11chiI-Abhi DCs having similar morphologies, including the presence of dendrites (Fig. 1B, 1C). FL-DCs and GM-DCs were similarly responsive to maturation stimuli, as both upregulated expression of MHC class II and costimulatory molecules following LPS treatment (Fig. 1D). Furthermore, LPS treatment induced similar expression of Il6 and Il12b mRNA in FL-DCs and GM-DCs (data not shown). Importantly, LPS-matured FL-DCs and GM-DCs were equivalent in their ability to stimulate naive T cells (Fig. 1E). Thus, by these standard assays, FL-DCs and GM-DCs each displayed the characteristics of bona fide DCs. However, FL-DCs and GM-DCs differed considerably with regard to lineage-associated gene expression. Compared with GM-DCs, FL-DCs expressed significantly higher levels of mRNA for the cDC-specific transcription factor Zbtb46 (Fig. 1F) (25, 26). In contrast, activated GM-DCs highly expressed Nos2, consistent with a moDC phenotype (Fig. 1F) (27). On the basis of these observations, we concluded that FL-DCs and GM-DCs corresponded to cDCs and moDCs, respectively.

FIGURE 1.
FIGURE 1.

Culturing BM precursors with FL or GM-CSF/IL-4 yields DCs that resemble conventional or moDCs, respectively. (A) Schematic protocol for the generation and maturation of BM-elicited DCs using FL (FL-DCs) or GM-CSF/IL-4 (GM-DCs). (B) Representative light micrographs of cytospin preparations of FL- or GM-DCs. (C) Representative cytograms depicting surface I-Ab and CD11c expression on FL- and GM-DCs after maturation with LPS. (D) Histograms depicting I-Ab, CD40, and CD86 expression on unstimulated (shaded histograms) or LPS-matured (bold lines) DCs. Data are from a single experiment, representative of two. (E) Stimulation of naive CD4+ OT-II cells by LPS-matured FL- or GM-DCs in the presence or absence of OVA323–339 peptide. Bar graphs represent the mean ± SD of viable T cells (duplicate samples). Data are from a single experiment, representative of two. (F) Zbtb46 and Nos2 mRNA expression by MACS-purified CD11c+ FL- and GM-DCs. Bar graphs represent the mean ± SD of mRNA amounts in arbitrary units (AU) after normalization to Gapdh mRNA. Data are from a single experiment, representative of two.

Ccr7gfp reporter mice are a convenient resource for assaying Ccr7 expression in DCs (10). Using these mice as a source of BM, we compared Ccr7gfp expression in FL-DCs and GM-DCs. Following LPS stimulation, FL-DCs rapidly upregulated Ccr7gfp (Fig. 2A, 2B). In contrast, GM-DCs expressed very low levels of Ccr7gfp following LPS treatment (Fig. 2A, 2B). Similar results were observed when FL-DCs and GM-DCs were stimulated with the TLR3 ligand poly(I:C) (Fig. 2B). To confirm that the GFP fluorescence correlated with functional CCR7 protein, we studied the abilities of FL-DCs and GM-DCs to undergo chemotaxis in response to CCL19. FL-DCs migrated very efficiently to various concentrations of CCL19, confirming that they expressed functional CCR7 (Fig. 2C). Conversely, GM-DCs migrated poorly to CCL19 (Fig. 2C), which was consistent with their low expression of Ccr7gfp. Thus, although FL-DCs and GM-DCs were similar in many measures of DC function, only FL-DCs expressed functional CCR7 at high levels.

FIGURE 2.
FIGURE 2.

BM-elicited cDCs, but not moDCs, express functional CCR7. (A) Analysis of Ccr7gfp fluorescence in CD11c+ FL- or GM-DCs generated from wild-type (gray histograms) or Ccr7gfp reporter mice (bold lines) after LPS maturation. The percentage of cells expressing Ccr7gfp is indicated on each plot. (B) Comparison of Ccr7gfp expression by CD11c+ FL- or GM-DCs after stimulation with either media alone, 100 ng ml−1 LPS, or 10 μg ml−1 poly(I:C) for 24 h. Bar graphs represent the mean ± SD of duplicate samples. Data are from a single experiment, representative of two. (C) Chemotaxis of LPS-matured FL- or GM-DCs in response to the indicated concentrations of the CCR7 ligand, CCL19. Symbols represent the mean ± SD of duplicate samples. Data are from a single experiment, representative of three.

The Ccr7 locus is enriched for repressive histone modifications in BM-elicited moDCs

The inability of GM-DCs to express Ccr7 despite having otherwise normal responsiveness to LPS (Fig. 1D) suggested that the Ccr7 locus in these cells might be inaccessible to transcriptional activators. It is well established that histone modifications help govern chromatin accessibility to the transcriptional machinery, thereby regulating gene expression (17). In particular, trimethylation of lysine 27 on histone 3 (H3K27me3), which is primarily mediated by the polycomb repressive complex 2 (PRC2), is associated with transcriptional repression in various cells including DCs and macrophages (28, 29). Analysis of available chromatin immunoprecipitation (ChIP)-sequencing data obtained from the Encyclopedia of DNA Elements (ENCODE) project (30) revealed that the Ccr7 promoter is enriched for H3K27me3 in tissues that generally lack CCR7 expression (Fig. 3A), suggesting that H3K27me3 might also be associated with Ccr7 repression in moDCs. Therefore, using ChIP-QPCR assays, we investigated H3K27me3 modifications at the Ccr7 promoter in LPS-stimulated FL-DCs and GM-DCs. We found that the Ccr7 promoter is significantly enriched for H3K27me3 in GM-DCs but not FL-DCs (Fig. 3B). GM-DCs also had similar enrichment of H3K27me3 at the first intron of Ccr7. To exclude the possibility that our findings at the Ccr7 locus were due to a widespread nonspecific increase in H3K27me3 in GM-DCs, we studied a distant locus containing the Magea2 gene. No significant differences were seen in H3K27me3 at that locus, indicating that repressive histone marks were preferentially increased at the Ccr7 locus (Fig. 3B). The level of H3K27me3 at the Ccr7 promoter was inversely related to Ccr7 mRNA expression, consistent with transcriptional repression of Ccr7 (Fig. 3C). Similar differences in Ccr7-associated H3K27me3 were observed in unstimulated DCs, indicating that the repressive histone marks were established prior to DC activation (Supplemental Fig. 1A). Because histone acetylation has been associated with transcriptional activation in human DCs (28), we also analyzed H3K27 acetylation at the Ccr7 locus. We did not find significant differences in Ccr7-associated H3K27 acetylation between FL- and GM-DCs (Supplemental Fig. 1B), suggesting that Ccr7 expression was predominantly regulated by repressive histone marks. Taken together, these findings suggest that lineage-specific repressive histone modifications help govern Ccr7 expression in BM-elicited DCs.

FIGURE 3.
FIGURE 3.

The Ccr7 locus is enriched for repressive histone modifications in BM-elicited moDCs. (A) Structure of the Ccr7 locus, including relative amounts of H3K27me3 in chromatin from the indicated organs of adult C57BL/6 mice (available through the Encyclopedia of DNA Elements [ENCODE] project and analyzed using the University of California Santa Cruz Genome Browser web site). The location of primers designed to amplify the Ccr7 promoter and first intron are indicated by rectangles. (B) ChIP-QPCR analysis of the Ccr7 promoter, Ccr7 first intron, or Magea2 locus in LPS-matured FL- or GM-DCs following immunoprecipitation with either anti-H3K27me3 (▪) or nonspecific IgG (□) Abs. Bar graphs represent the mean ± SD of triplicate samples after normalization to input DNA. Data are from a single experiment, representative of two. (C) Ccr7 mRNA in mature FL- or GM-DCs. Bar graphs represent the mean ± SD of duplicate samples after normalization to Gapdh mRNA. Data are from a single experiment, representative of two. ***p < 0.001. AU, arbitrary unit.

Nonmigratory lung-resident moDCs have increased levels of Ccr7-associated H3K27me3

Having established that the Ccr7 locus is associated with repressive histone marks in moDCs expanded from BM progenitors, we next investigated whether similar repressive histone marks are associated with Ccr7 in lung-resident moDCs. Lung-resident DCs can be phenotypically divided into CD103+ or CD11bhi DCs. CD103+ DCs arise from pre-DC precursors and thus represent a pure population of cDCs (10). By contrast, CD11bhi DCs contain a mixture of FL-dependent cDCs and FL-independent moDCs, with the latter cells having a higher display level of CD14 (10). However, because some CD11bhi DCs express intermediate levels of CD14, this molecule cannot reliably distinguish cDCs from moDCs. CD64 expression is reported to discriminate between cDCs and moDCs (3, 31), but we recently found that display levels of a different marker, CD88, is a more reliable marker to distinguish CD11bhi moDCs from CD11bhi cDCs (H. Nakano, T.P. Moran, K. Nakano, C.D. Bortner, and D.N. Cook, submitted for publication). To confirm that CD88 can also distinguish nonmigratory moDCs from migratory cDCs, we isolated lung-resident DCs from Ccr7gfp reporter mice by flow cytometric cell sorting (Fig. 4A). As expected, all lung-resident DC subsets expressed low levels of Ccr7gfp immediately after isolation from naive mice (Fig. 4B). Stimulation with LPS resulted in significant induction of Ccr7gfp in CD103+ and CD11bhiCD88lo DCs (Fig. 4B). In contrast, CD11bhiCD88hi DCs expressed very low levels of Ccr7gfp after activation, which is consistent with their monocytic lineage (Fig. 4B). All lung DC subsets expressed high levels of CD86 after LPS stimulation (data not shown), indicating normal responsiveness to TLR4 ligands. Analysis of Ccr7 mRNA in wild-type mice confirmed that this gene is more highly expressed in activated CD103+ cDCs and CD11bhiCD88lo cDCs compared with CD11bhiCD88hi moDCs (Fig. 4C). Thus, CD88 display can identify nonmigratory CD11bhi moDCs in the lung.

FIGURE 4.
FIGURE 4.

Nonmigratory lung-resident moDCs have increased levels of Ccr7-associated H3K27me3. (A) Gating strategy for flow cytometry–based sorting of lung-resident DC subsets from wild-type or Ccr7gfp reporter mice. (B) Analysis of Ccr7gfp expression on sorted lung-resident DCs before (shaded histograms) or after (bold lines) ex vivo stimulation with 100 ng ml−1 LPS for 24 h. Data are from a single experiment, representative of two. (C) Ccr7 mRNA expression in lung-resident DCs isolated from mice 16 h post-LPS inhalation. Bar graphs represent the mean ± SEM (after normalization to Gapdh mRNA) of combined data from two independent experiments. (D) ChIP-QPCR analysis of the Ccr7 promoter or Hoxc10 locus (reference gene) in lung-resident DCs after immunoprecipitation with either anti-H3K27me3 (▪) or nonspecific IgG (□) Abs. Bar graphs represent the mean ± SEM (after normalization to input DNA) of combined data from three independent experiments. ***p < 0.001. Auto, autofluorescence; AU, arbitrary unit.

Using CD88 as a marker for moDCs, we purified migratory CD103+ and CD11bhiCD88lo cDCs, as well as nonmigratory CD11bhiCD88hi moDCs, from the lungs of LPS-treated mice. Chromatin was prepared from each DC subset and analyzed for Ccr7-associated H3K27me3. Compared with CD103+ DCs and CD11bhiCD88lo cDCs, CD11bhiCD88hi moDCs had significantly elevated levels of H3K27me3 at the Ccr7 promoter (Fig. 4D). The amount of Ccr7-associated H3K27me3 was inversely related to the expression of this gene, consistent with transcriptional silencing of Ccr7 in CD11bhiCD88hi moDCs (Fig. 4C). Levels of H3K27me3 at a distant locus (Hoxc10) were similar among all DC subsets, confirming that the epigenetic differences seen at the Ccr7 promoter are not due to a nonspecific genomewide increase of H3K27me3 in lung moDCs (Fig. 4D). Overall, these findings indicate that the nonmigratory status of lung-resident moDCs is associated with repressive histone modifications at the Ccr7 promoter.

BM monocytes have low levels of Ccr7-associated H3K27me3

Our observation that cDCs and moDCs have disparate levels of Ccr7-associated H3K27me3 is consistent with lineage-specific epigenetic repression of Ccr7 expression. This prompted us to investigate whether the divergence in H3K27me3 at the Ccr7 locus in cDCs and moDCs occurs during lineage commitment. Monocyte-DC progenitors can give rise to both monocytes and pre-DCs (32). We therefore compared histone modifications in the latter two types of progenitor cells following their purification from BM. Unexpectedly, monocytes and pre-DCs had similar amounts of H3K27me3 at the Ccr7 promoter (Fig. 5A), and these amounts were much lower than that seen for either BM-elicited or lung moDCs (Figs. 3B, 4D). Thus, differentiation of monocyte-DC progenitors to monocytes in the BM is not immediately accompanied by epigenetic repression of Ccr7.

FIGURE 5.
FIGURE 5.

Monocytes and their immediate progeny have low levels of H3K27me3 at the Ccr7 promoter. (A) ChIP-QPCR analysis of the Ccr7 promoter or Hoxc10 locus (reference gene) in monocytes (mono) or pre-DCs following immunoprecipitation with either anti-H3K27me3 (▪) or nonspecific IgG (□) Abs. Bar graphs represent the mean ± SEM (after normalization to input DNA) of combined data from three independent experiments. (B) Gating strategy for purifying lung-resident CD11bhiCD88hi moDCs and Ly-6ChiCD11bhi inflammatory DCs (infDCs) from LPS-treated lungs. The cytogram depicts CD88 and Ly-6C expression after gating on CD11chiAutofluorescence−I-AbhiCD11bhi lung cells. (C) ChIP-QPCR analysis of the Ccr7 promoter or Hoxc10 locus (reference gene) in Ly-6Chi infDCs or CD88hi moDCs. Bar graphs represent the mean ± SEM (after normalization to input DNA) of combined data from three independent experiments. *p < 0.05.

Epigenetic repression of the Ccr7 promoter is gradually established during monocyte differentiation into DCs

The similar amounts of H3K27me3 at the Ccr7 locus of monocytes and pre-DCs suggested that this epigenetic modification is acquired after monocytes enter peripheral tissues and differentiate into moDCs. We first investigated whether monocyte emigration into pulmonary tissues triggers epigenetic repression of Ccr7. Airway exposure to LPS results in the recruitment of Ly-6Chi monocytes to the lungs, which rapidly differentiate into Ly-6ChiCD11bhi inflammatory DCs (33). Inflammatory DCs also express CD88 but can be distinguished from lung-resident moDCs by their high-level expression of Ly-6C (Fig. 5B). ChIP-QPCR analysis of inflammatory DCs revealed that they had significantly lower levels of Ccr7-associated H3K27me3 compared with lung-resident moDCs (Fig. 5C). Indeed, inflammatory DCs and BM monocytes had similar low levels of H3K27me3 at the Ccr7 locus (Fig. 5A, 5C). Thus, extravasation of monocytes into the lung parenchyma does not immediately result in epigenetic repression of Ccr7.

We next investigated whether epigenetic repression of Ccr7 is established during the later stages of monocyte differentiation into moDCs. We have previously shown that only a very small percentage of adoptively transferred monocytes enter the lungs and differentiate into resident moDCs (10). Therefore, it was not possible to accurately track the fate of large numbers of monocytes in the lung for an extended period. As an alternative approach, we purified Ly-6Chi monocytes from BM and followed epigenetic changes at the Ccr7 promoter during ex vivo differentiation of these cells into moDCs (34). As expected, during 6 d of culture in the presence of GM-CSF and IL-4, monocytes differentiated into CD11chiI-Abhi moDCs (Fig. 6A). As we had seen previously with BM progenitors cultured under these same conditions, monocyte-derived cells failed to express Ccr7, even after their stimulation with LPS (Fig. 6B). During ex vivo moDC differentiation, we observed a significant increase in Ccr7-associated H3K27me3 (Fig. 6C). In contrast, the level of H3K27me3 at the Hoxc10 locus remained stable during the culture period (Fig. 6C), indicating the observed changes at the Ccr7 locus were not due to a genomewide increase in H3K27me3. Consistent with this, we did not detect increased expression of the PRC2 core subunits EZH2, EED, SUZ12, and RbAp48 during moDC differentiation (Supplemental Fig. 2). Overall, these findings suggest that epigenetic silencing of Ccr7 occurs in a specific and gradual manner during the differentiation of monocytes into lung-resident moDCs.

FIGURE 6.
FIGURE 6.

Epigenetic repression of the Ccr7 promoter is gradually established during monocyte differentiation to moDCs. (A–C) Ly-6Chi monocytes sorted from the BM of wild-type (A and C) or Ccr7gfp reporter mice (B) were cultured in the presence of GM-CSF and IL-4 for 6 d. Cells were analyzed by flow cytometry (A and B) or ChIP-QPCR (C) at the indicated time points. (A) Cytograms showing CD11c and I-Ab expression on monocytes at the indicated time points during culture. Data are from a single experiment, representative of two. (B) Cytograms depict Ccr7gfp expression by monocytes at the indicated time points during culture. Cells were treated with 100 ng ml−1 LPS for 24 h prior to flow cytometric analysis. Data are from a single experiment, representative of two. (C) Quantification of H3K27me3 by ChIP-QPCR analysis of the Ccr7 promoter or Hoxc10 locus (reference gene) during monocyte differentiation into moDCs. Bar graphs represent the mean ± SEM (after normalization to input DNA) of combined data from two independent experiments. The line graph depicts the mean ratio (± SEM) of Ccr7-associated H3K27me3 to Hoxc10-associated H3K27me3. **p < 0.01.

Discussion

The migration of DCs to lung-draining LN is critical for shaping nascent immune responses to inhaled Ags (1, 3, 10). Given that the DC network is composed of populations with distinct functional roles, it is not surprising that only certain subsets possess the ability to express Ccr7 and migrate to regional LN. We have previously demonstrated that the developmental lineage of DCs is important for determining their migratory potential (10). In the current study, we investigated whether epigenetic mechanisms might contribute to lineage-specific Ccr7 expression. We found that in BM-elicited or lung moDCs, the Ccr7 promoter is enriched for the repressive histone mark H3K27me3. Consequently, Ccr7 induction is transcriptionally repressed in moDCs but not cDCs. The repressive histone modifications are not established during lineage commitment in the BM but are formed during monocyte differentiation into moDCs in the periphery. Our results suggest that a combination of lineage-specific epigenetic mechanisms and cues within the tissue microenvironment help determine the migratory capacity, and consequently the functional role, of lung DC subsets. The nonmigratory status of moDCs suggests that they do not function during Ag sensitization, which is thought to require DC migration, but rather during the effector phase of immune responses within the lung. Indeed, a recent report found that moDCs were largely responsible for Ag presentation and proinflammatory cytokine secretion in the lungs during allergen challenge (3). Whether lung moDCs are more efficient than cDCs at stimulating effector or memory T cells is an important question for future studies.

Although there has been recent progress in identifying the transcriptional profiles of different DC subtypes (9, 12, 35), little is known regarding the epigenetic mechanisms regulating gene expression in DCs. This is in contrast to Th cell differentiation, where epigenetic changes at lineage-specific genes have been well documented (36). Epigenetic mechanisms are likely responsible for regulating several aspects of DC immunobiology. For example, DCs treated with histone deacetylase inhibitors have altered expression of proinflammatory cytokines and costimulatory molecules, arguing that dynamic changes in histone modifications are important during DC maturation (37). Furthermore, heritable epigenetic changes have been shown to influence DC function during adaptive immune responses. Splenic DCs from offspring of allergen-sensitized mothers had altered genomic DNA methylation patterns, which was associated with a Th2-skewing phenotype when compared with DCs from pups of naive mothers (38). The current study provides further insight into how epigenetic changes can influence DC function, specifically through regulation of their migration. By epigenetically silencing the Ccr7 gene, moDCs assume a nonmigratory phenotype within the lung.

Unexpectedly, we found that epigenetic repression of Ccr7 is not established early during DC lineage commitment, but rather during monocyte differentiation into moDCs. Using an ex vivo model for generating moDCs from BM monocytes, we observed a gradual but specific increase in H3K27me3 at the Ccr7 promoter. It is possible that ex vivo generation of moDCs from monocytes does not accurately reflect in vivo differentiation of moDCs in the lung. However, ex vivo–generated and lung-resident moDCs had comparable surface marker phenotypes and histone modifications at the Ccr7 locus, suggesting that they undergo similar differentiation pathways. Improvements in cellular fate-mapping and ChIP analyses using small cell numbers will help facilitate future epigenetic studies of lung-resident moDCs and other rare cell types.

Interestingly, we observed low levels of H3K27me3 at the Ccr7 locus in monocytes, implying that Ccr7 retains the potential to be expressed in these cells or their progeny. This might explain contradicting reports that monocyte-derived APCs in the colon can express Ccr7 and migrate to LN (39). Furthermore, epidermal Langerhans cells—which are derived from monocytes (40)—are reported to express Ccr7 and traffic to skin-draining LN (41). It is conceivable that tissue-specific factors can regulate epigenetic silencing of the Ccr7 locus in monocyte-derived APCs. Although the identity of these factors is unknown, several cytokines can modulate Ccr7 expression in activated DCs, including thymic stromal lymphopoietin (42), IL-33 (43), and type I IFNs (44). In addition, our studies with BM-elicited moDCs and ex vivo–cultured monocytes suggest a role of GM-CSF and FL in determining epigenetic modifications at the Ccr7 locus. The observation that GM-CSF may lead to epigenetic repression of Ccr7 in monocytes has significant implications for DC-based immunotherapies because this cytokine is frequently used to generate DCs from peripheral blood monocytes in humans. Because LN homing by DCs is considered necessary for optimal stimulation of Ag-specific T cells (45), understanding how GM-CSF and FL influence the migratory potential of DCs will be essential for designing effective DC vaccines.

Although our studies demonstrate that Ccr7-associated H3K27me3 increases during monocyte differentiation into moDCs, the mechanisms by which occurs are currently unclear. Because trimethylation of H3K27 is mediated by the chromatin modification complex PRC2, we studied expression of genes encoding its core subunits (EZH2, EED, SUZ12, and RbAp48) during monocyte differentiation to moDCs (46). We found that expression of these genes generally decreased during moDC development (Supplemental Fig. 2), which is consistent with the previously reported decrease in Ezh2 expression during cellular differentiation (47). Therefore, it is likely that the increased Ccr7-associated H3K27me3 results from a selective recruitment of PRC2 to the Ccr7 locus by specific DNA-binding proteins or transcription factors (48). Identification of such factors should further our understanding of how the Ccr7 locus is regulated in moDCs.

Although our observations suggest that H3K27me3 leads to silencing of Ccr7 in moDCs, demonstrating direct causality is difficult. It is possible to inhibit H3K27me3 by targeting the histone methyltransferase EZH2, but this can affect multiple aspects of cell differentiation and survival (49). Not surprisingly, we found that the EZH2 inhibitor 3-deazaneplanocin A interfered with DC development from BM progenitors and monocytes, thus precluding any specific studies on Ccr7 expression (T.P. Moran, unpublished observations). Strategies that specifically inhibit EZH2 activity at the Ccr7 locus will be important for addressing this issue. It is also likely that H3K27me3 is but one of many mechanisms involved with regulating Ccr7 expression. Monocytes and monocyte-derived Ly-6Chi inflammatory DCs have low levels of Ccr7-associated H3K27me3, yet they do not express Ccr7 after stimulation with LPS (Fig. 6A) (10). This implies that in addition to a receptive chromatin configuration at the Ccr7 promoter, lineage-specific transcription factors are also necessary for driving gene expression. Several transcription factors have been reported to regulate Ccr7 expression, including NF-κB (50), peroxisome proliferator-activated receptor γ (51), Runx3 (52), liver X receptor (53), and IFN regulatory factor 4 (54). The migratory properties of cDCs and moDCs may be dependent on differential expression of these transcription factors. Additional epigenetic mechanisms, such as DNA methylation and noncoding RNAs, might also regulate Ccr7 expression. The Ccr7 promoter does not contain any CpG islands, but it is possible that DNA methylation in upstream enhancers or intronic regions may influence Ccr7 expression. Noncoding RNAs that inhibit CCR7 production have been described in human T lymphocytes and breast cancer cells (55, 56) but not in APCs. Future studies will help clarify the relative contribution of lineage-specific transcription factors and other epigenetic marks to Ccr7 regulation.

Overall, our findings suggest that by controlling Ccr7 expression, lineage-specific epigenetic mechanisms can influence the function of specific DC subsets. Identifying the endogenous and cell-intrinsic factors that direct Ccr7-specific epigenetic changes will likely uncover pathways that can be targeted to modulate DC migration. In turn, the ability to manipulate the migratory properties of DCs represents a novel strategy for improving DC-based immunotherapies and for treating immune-mediated diseases.

Disclosures

The authors have no financial conflicts of interest.

Acknowledgments

We thank Carl Bortner and Maria Sifre of the NIEHS Flow Cytometry Center for help with cell sorting, the NIEHS Protein Expression Core Facility for production of recombinant human FL, Ligon Perrow for mouse colony management, Komal Patel for technical assistance, Thomas Randall for bioinformatics consultation, and Michael Fessler and Harriet Kinyamu for critical review of the manuscript.

Footnotes

  • This work was supported by National Institutes of Health Grant 5 T32 AI 007062-34 and by the Intramural Research Program of the National Institutes of Health and the National Institute on Environmental Health Sciences.

  • The online version of this article contains supplemental material.

  • Abbreviations used in this article:

    BM
    bone marrow
    cDC
    conventional DC
    ChIP
    chromatin immunoprecipitation
    DC
    dendritic cell
    FL
    Flt3 ligand
    H3K27me3
    histone 3 lysine 27 trimethylation
    LN
    lymph node
    moDC
    monocyte-derived DC
    NIEHS
    National Institute of Environmental Health Sciences
    poly (I:C)
    polyinosinic:polycytidylic acid
    PRC2
    polycomb repressive complex 2
    pre-DC
    precursor of DC
    QPCR
    quantitative PCR.

  • Received June 5, 2014.
  • Accepted September 8, 2014.

References

  1. ↵
    1. Vermaelen K. Y.,
    2. I. Carro-Muino,
    3. B. N. Lambrecht,
    4. R. A. Pauwels
    . 2001. Specific migratory dendritic cells rapidly transport antigen from the airways to the thoracic lymph nodes. J. Exp. Med. 193: 51–60.
    OpenUrlAbstract/FREE Full Text
    1. Hintzen G.,
    2. L. Ohl,
    3. M. L. del Rio,
    4. J. I. Rodriguez-Barbosa,
    5. O. Pabst,
    6. J. R. Kocks,
    7. J. Krege,
    8. S. Hardtke,
    9. R. Förster
    . 2006. Induction of tolerance to innocuous inhaled antigen relies on a CCR7-dependent dendritic cell-mediated antigen transport to the bronchial lymph node. J. Immunol. 177: 7346–7354.
    OpenUrlAbstract/FREE Full Text
  3. ↵
    1. Plantinga M.,
    2. M. Guilliams,
    3. M. Vanheerswynghels,
    4. K. Deswarte,
    5. F. Branco-Madeira,
    6. W. Toussaint,
    7. L. Vanhoutte,
    8. K. Neyt,
    9. N. Killeen,
    10. B. Malissen,
    11. et al
    . 2013. Conventional and monocyte-derived CD11b+ dendritic cells initiate and maintain T helper 2 cell-mediated immunity to house dust mite allergen. Immunity 38: 322–335.
    OpenUrlCrossRefPubMed
  4. ↵
    1. GeurtsvanKessel C. H.,
    2. M. A. Willart,
    3. L. S. van Rijt,
    4. F. Muskens,
    5. M. Kool,
    6. C. Baas,
    7. K. Thielemans,
    8. C. Bennett,
    9. B. E. Clausen,
    10. H. C. Hoogsteden,
    11. et al
    . 2008. Clearance of influenza virus from the lung depends on migratory langerin+CD11b‑ but not plasmacytoid dendritic cells. J. Exp. Med. 205: 1621–1634.
    OpenUrlAbstract/FREE Full Text
  5. ↵
    1. Förster R.,
    2. A. C. Davalos-Misslitz,
    3. A. Rot
    . 2008. CCR7 and its ligands: balancing immunity and tolerance. Nat. Rev. Immunol. 8: 362–371.
    OpenUrlCrossRefPubMed
  6. ↵
    1. Broggi A.,
    2. I. Zanoni,
    3. F. Granucci
    . 2013. Migratory conventional dendritic cells in the induction of peripheral T cell tolerance. J. Leukoc. Biol. 94: 903–911.
    OpenUrlAbstract/FREE Full Text
  7. ↵
    1. Lambrecht B. N.,
    2. H. Hammad
    . 2012. Lung dendritic cells in respiratory viral infection and asthma: from protection to immunopathology. Annu. Rev. Immunol. 30: 243–270.
    OpenUrlCrossRefPubMed
  8. ↵
    1. Nakano H.,
    2. M. E. Free,
    3. G. S. Whitehead,
    4. S. Maruoka,
    5. R. H. Wilson,
    6. K. Nakano,
    7. D. N. Cook
    . 2012. Pulmonary CD103+ dendritic cells prime Th2 responses to inhaled allergens. Mucosal Immunol. 5: 53–65.
    OpenUrlCrossRefPubMed
  9. ↵
    1. Satpathy A. T.,
    2. X. Wu,
    3. J. C. Albring,
    4. K. M. Murphy
    . 2012. Re(de)fining the dendritic cell lineage. Nat. Immunol. 13: 1145–1154.
    OpenUrlCrossRefPubMed
  10. ↵
    1. Nakano H.,
    2. J. E. Burgents,
    3. K. Nakano,
    4. G. S. Whitehead,
    5. C. Cheong,
    6. C. D. Bortner,
    7. D. N. Cook
    . 2013. Migratory properties of pulmonary dendritic cells are determined by their developmental lineage. Mucosal Immunol. 6: 678–691.
    OpenUrlCrossRefPubMed
  11. ↵
    1. Liu K.,
    2. M. C. Nussenzweig
    . 2010. Origin and development of dendritic cells. Immunol. Rev. 234: 45–54.
    OpenUrlCrossRefPubMed
  12. ↵
    1. Merad M.,
    2. P. Sathe,
    3. J. Helft,
    4. J. Miller,
    5. A. Mortha
    . 2013. The dendritic cell lineage: ontogeny and function of dendritic cells and their subsets in the steady state and the inflamed setting. Annu. Rev. Immunol. 31: 563–604.
    OpenUrlCrossRefPubMed
  13. ↵
    1. Bogunovic M.,
    2. F. Ginhoux,
    3. J. Helft,
    4. L. Shang,
    5. D. Hashimoto,
    6. M. Greter,
    7. K. Liu,
    8. C. Jakubzick,
    9. M. A. Ingersoll,
    10. M. Leboeuf,
    11. et al
    . 2009. Origin of the lamina propria dendritic cell network. Immunity 31: 513–525.
    OpenUrlCrossRefPubMed
  14. ↵
    1. Tamoutounour S.,
    2. M. Guilliams,
    3. F. Montanana Sanchis,
    4. H. Liu,
    5. D. Terhorst,
    6. C. Malosse,
    7. E. Pollet,
    8. L. Ardouin,
    9. H. Luche,
    10. C. Sanchez,
    11. et al
    . 2013. Origins and functional specialization of macrophages and of conventional and monocyte-derived dendritic cells in mouse skin. Immunity 39: 925–938.
    OpenUrlCrossRefPubMed
  15. ↵
    1. Murphy K. M.
    2013. Transcriptional control of dendritic cell development. Adv. Immunol. 120: 239–267.
    OpenUrlCrossRefPubMed
  16. ↵
    1. Kim H. P.,
    2. Y. S. Lee,
    3. J. H. Park,
    4. Y. J. Kim
    . 2013. Transcriptional and epigenetic networks in the development and maturation of dendritic cells. Epigenomics 5: 195–204.
    OpenUrlCrossRefPubMed
  17. ↵
    1. Kondilis-Mangum H. D.,
    2. P. A. Wade
    . 2013. Epigenetics and the adaptive immune response. Mol. Aspects Med. 34: 813–825.
    OpenUrlCrossRefPubMed
  18. ↵
    1. Lee D. U.,
    2. S. Agarwal,
    3. A. Rao
    . 2002. Th2 lineage commitment and efficient IL-4 production involves extended demethylation of the IL-4 gene. Immunity 16: 649–660.
    OpenUrlCrossRefPubMed
    1. Avni O.,
    2. D. Lee,
    3. F. Macian,
    4. S. J. Szabo,
    5. L. H. Glimcher,
    6. A. Rao
    . 2002. T(H) cell differentiation is accompanied by dynamic changes in histone acetylation of cytokine genes. Nat. Immunol. 3: 643–651.
    OpenUrlCrossRefPubMed
  20. ↵
    1. Wei G.,
    2. L. Wei,
    3. J. Zhu,
    4. C. Zang,
    5. J. Hu-Li,
    6. Z. Yao,
    7. K. Cui,
    8. Y. Kanno,
    9. T. Y. Roh,
    10. W. T. Watford,
    11. et al
    . 2009. Global mapping of H3K4me3 and H3K27me3 reveals specificity and plasticity in lineage fate determination of differentiating CD4+ T cells. Immunity 30: 155–167.
    OpenUrlCrossRefPubMed
  21. ↵
    1. Verstraete K.,
    2. S. Koch,
    3. S. Ertugrul,
    4. I. Vandenberghe,
    5. M. Aerts,
    6. G. Vandriessche,
    7. C. Thiede,
    8. S. N. Savvides
    . 2009. Efficient production of bioactive recombinant human Flt3 ligand in E. coli. Protein J. 28: 57–65.
    OpenUrlCrossRefPubMed
  22. ↵
    1. Nakano H.,
    2. D. N. Cook
    . 2013. Pulmonary antigen presenting cells: isolation, purification, and culture. Methods Mol. Biol. 1032: 19–29.
    OpenUrlCrossRefPubMed
  23. ↵
    1. Carabana J.,
    2. A. Watanabe,
    3. B. Hao,
    4. M. S. Krangel
    . 2011. A barrier-type insulator forms a boundary between active and inactive chromatin at the murine TCRβ locus. J. Immunol. 186: 3556–3562.
    OpenUrlAbstract/FREE Full Text
  24. ↵
    1. Xu Y.,
    2. Y. Zhan,
    3. A. M. Lew,
    4. S. H. Naik,
    5. M. H. Kershaw
    . 2007. Differential development of murine dendritic cells by GM-CSF versus Flt3 ligand has implications for inflammation and trafficking. J. Immunol. 179: 7577–7584.
    OpenUrlAbstract/FREE Full Text
  25. ↵
    1. Satpathy A. T.,
    2. W. Kc,
    3. J. C. Albring,
    4. B. T. Edelson,
    5. N. M. Kretzer,
    6. D. Bhattacharya,
    7. T. L. Murphy,
    8. K. M. Murphy
    . 2012. Zbtb46 expression distinguishes classical dendritic cells and their committed progenitors from other immune lineages. J. Exp. Med. 209: 1135–1152.
    OpenUrlAbstract/FREE Full Text
  26. ↵
    1. Meredith M. M.,
    2. K. Liu,
    3. G. Darrasse-Jeze,
    4. A. O. Kamphorst,
    5. H. A. Schreiber,
    6. P. Guermonprez,
    7. J. Idoyaga,
    8. C. Cheong,
    9. K. H. Yao,
    10. R. E. Niec,
    11. M. C. Nussenzweig
    . 2012. Expression of the zinc finger transcription factor zDC (Zbtb46, Btbd4) defines the classical dendritic cell lineage. J. Exp. Med. 209: 1153–1165.
    OpenUrlAbstract/FREE Full Text
  27. ↵
    1. Patenaude J.,
    2. M. D’Elia,
    3. G. Côté-Maurais,
    4. J. Bernier
    . 2011. LPS response and endotoxin tolerance in Flt-3L‑induced bone marrow-derived dendritic cells. Cell. Immunol. 271: 184–191.
    OpenUrlCrossRefPubMed
  28. ↵
    1. Tserel L.,
    2. R. Kolde,
    3. A. Rebane,
    4. K. Kisand,
    5. T. Org,
    6. H. Peterson,
    7. J. Vilo,
    8. P. Peterson
    . 2010. Genome-wide promoter analysis of histone modifications in human monocyte-derived antigen presenting cells. BMC Genomics 11: 642.
    OpenUrlCrossRefPubMed
  29. ↵
    1. Barski A.,
    2. S. Cuddapah,
    3. K. Cui,
    4. T.-Y. Roh,
    5. D. E. Schones,
    6. Z. Wang,
    7. G. Wei,
    8. I. Chepelev,
    9. K. Zhao
    . 2007. High-resolution profiling of histone methylations in the human genome. Cell 129: 823–837.
    OpenUrlCrossRefPubMed
  30. ↵
    1. Bernstein B. E.,
    2. E. Birney,
    3. I. Dunham,
    4. E. D. Green,
    5. C. Gunter,
    6. M. Snyder,
    7. ENCODE Project Consortium
    . 2012. An integrated encyclopedia of DNA elements in the human genome. Nature 489: 57–74.
    OpenUrlCrossRefPubMed
  31. ↵
    1. Schlitzer A.,
    2. N. McGovern,
    3. P. Teo,
    4. T. Zelante,
    5. K. Atarashi,
    6. D. Low,
    7. A. W. Ho,
    8. P. See,
    9. A. Shin,
    10. P. S. Wasan,
    11. et al
    . 2013. IRF4 transcription factor-dependent CD11b+ dendritic cells in human and mouse control mucosal IL-17 cytokine responses. Immunity 38: 970–983.
    OpenUrlCrossRefPubMed
  32. ↵
    1. Fogg D. K.,
    2. C. Sibon,
    3. C. Miled,
    4. S. Jung,
    5. P. Aucouturier,
    6. D. R. Littman,
    7. A. Cumano,
    8. F. Geissmann
    . 2006. A clonogenic bone marrow progenitor specific for macrophages and dendritic cells. Science 311: 83–87.
    OpenUrlAbstract/FREE Full Text
  33. ↵
    1. Shi C.,
    2. E. G. Pamer
    . 2011. Monocyte recruitment during infection and inflammation. Nat. Rev. Immunol. 11: 762–774.
    OpenUrlCrossRefPubMed
  34. ↵
    1. Cheong C.,
    2. I. Matos,
    3. J. H. Choi,
    4. D. B. Dandamudi,
    5. E. Shrestha,
    6. M. P. Longhi,
    7. K. L. Jeffrey,
    8. R. M. Anthony,
    9. C. Kluger,
    10. G. Nchinda,
    11. et al
    . 2010. Microbial stimulation fully differentiates monocytes to DC-SIGN/CD209+ dendritic cells for immune T cell areas. Cell 143: 416–429.
    OpenUrlCrossRefPubMed
  35. ↵
    1. Miller J. C.,
    2. B. D. Brown,
    3. T. Shay,
    4. E. L. Gautier,
    5. V. Jojic,
    6. A. Cohain,
    7. G. Pandey,
    8. M. Leboeuf,
    9. K. G. Elpek,
    10. J. Helft,
    11. et al
    . 2012. Deciphering the transcriptional network of the dendritic cell lineage. Nat. Immunol. 13: 888–899.
    OpenUrlCrossRefPubMed
  36. ↵
    1. Kanno Y.,
    2. G. Vahedi,
    3. K. Hirahara,
    4. K. Singleton,
    5. J. J. O’Shea
    . 2012. Transcriptional and epigenetic control of T helper cell specification: molecular mechanisms underlying commitment and plasticity. Annu. Rev. Immunol. 30: 707–731.
    OpenUrlCrossRefPubMed
  37. ↵
    1. Bode K. A.,
    2. K. Schroder,
    3. D. A. Hume,
    4. T. Ravasi,
    5. K. Heeg,
    6. M. J. Sweet,
    7. A. H. Dalpke
    . 2007. Histone deacetylase inhibitors decrease Toll-like receptor-mediated activation of proinflammatory gene expression by impairing transcription factor recruitment. Immunology 122: 596–606.
    OpenUrlCrossRefPubMed
  38. ↵
    1. Mikhaylova L.,
    2. Y. Zhang,
    3. L. Kobzik,
    4. A. V. Fedulov
    . 2013. Link between epigenomic alterations and genome-wide aberrant transcriptional response to allergen in dendritic cells conveying maternal asthma risk. PLoS One 8: e70387.
    OpenUrlCrossRefPubMed
  39. ↵
    1. Zigmond E.,
    2. C. Varol,
    3. J. Farache,
    4. E. Elmaliah,
    5. A. T. Satpathy,
    6. G. Friedlander,
    7. M. Mack,
    8. N. Shpigel,
    9. I. G. Boneca,
    10. K. M. Murphy,
    11. et al
    . 2012. Ly6Chi monocytes in the inflamed colon give rise to proinflammatory effector cells and migratory antigen-presenting cells. Immunity 37: 1076–1090.
    OpenUrlCrossRefPubMed
  40. ↵
    1. Merad M.,
    2. M. G. Manz,
    3. H. Karsunky,
    4. A. Wagers,
    5. W. Peters,
    6. I. Charo,
    7. I. L. Weissman,
    8. J. G. Cyster,
    9. E. G. Engleman
    . 2002. Langerhans cells renew in the skin throughout life under steady-state conditions. Nat. Immunol. 3: 1135–1141.
    OpenUrlCrossRefPubMed
  41. ↵
    1. Ohl L.,
    2. M. Mohaupt,
    3. N. Czeloth,
    4. G. Hintzen,
    5. Z. Kiafard,
    6. J. Zwirner,
    7. T. Blankenstein,
    8. G. Henning,
    9. R. Förster
    . 2004. CCR7 governs skin dendritic cell migration under inflammatory and steady-state conditions. Immunity 21: 279–288.
    OpenUrlCrossRefPubMed
  42. ↵
    1. Kitajima M.,
    2. S. F. Ziegler
    . 2013. Cutting edge: identification of the thymic stromal lymphopoietin-responsive dendritic cell subset critical for initiation of type 2 contact hypersensitivity. J. Immunol. 191: 4903–4907.
    OpenUrlAbstract/FREE Full Text
  43. ↵
    1. Besnard A. G.,
    2. D. Togbe,
    3. N. Guillou,
    4. F. Erard,
    5. V. Quesniaux,
    6. B. Ryffel
    . 2011. IL-33-activated dendritic cells are critical for allergic airway inflammation. Eur. J. Immunol. 41: 1675–1686.
    OpenUrlCrossRefPubMed
  44. ↵
    1. Parlato S.,
    2. S. M. Santini,
    3. C. Lapenta,
    4. T. Di Pucchio,
    5. M. Logozzi,
    6. M. Spada,
    7. A. M. Giammarioli,
    8. W. Malorni,
    9. S. Fais,
    10. F. Belardelli
    . 2001. Expression of CCR-7, MIP-3β, and Th-1 chemokines in type I IFN-induced monocyte-derived dendritic cells: importance for the rapid acquisition of potent migratory and functional activities. Blood 98: 3022–3029.
    OpenUrlAbstract/FREE Full Text
  45. ↵
    1. MartIn-Fontecha A.,
    2. S. Sebastiani,
    3. U. E. Höpken,
    4. M. Uguccioni,
    5. M. Lipp,
    6. A. Lanzavecchia,
    7. F. Sallusto
    . 2003. Regulation of dendritic cell migration to the draining lymph node: impact on T lymphocyte traffic and priming. J. Exp. Med. 198: 615–621.
    OpenUrlAbstract/FREE Full Text
  46. ↵
    1. O’Meara M. M.,
    2. J. A. Simon
    . 2012. Inner workings and regulatory inputs that control Polycomb repressive complex 2. Chromosoma 121: 221–234.
    OpenUrlCrossRefPubMed
  47. ↵
    1. Ezhkova E.,
    2. H. A. Pasolli,
    3. J. S. Parker,
    4. N. Stokes,
    5. I. H. Su,
    6. G. Hannon,
    7. A. Tarakhovsky,
    8. E. Fuchs
    . 2009. Ezh2 orchestrates gene expression for the stepwise differentiation of tissue-specific stem cells. Cell 136: 1122–1135.
    OpenUrlCrossRefPubMed
  48. ↵
    1. Kim J.,
    2. H. Kim
    . 2012. Recruitment and biological consequences of histone modification of H3K27me3 and H3K9me3. ILAR J. 53: 232–239.
    OpenUrlAbstract/FREE Full Text
  49. ↵
    1. Tan J.,
    2. X. Yang,
    3. L. Zhuang,
    4. X. Jiang,
    5. W. Chen,
    6. P. L. Lee,
    7. R. K. Karuturi,
    8. P. B. Tan,
    9. E. T. Liu,
    10. Q. Yu
    . 2007. Pharmacologic disruption of Polycomb-repressive complex 2-mediated gene repression selectively induces apoptosis in cancer cells. Genes Dev. 21: 1050–1063.
    OpenUrlAbstract/FREE Full Text
  50. ↵
    1. Höpken U. E.,
    2. H. D. Foss,
    3. D. Meyer,
    4. M. Hinz,
    5. K. Leder,
    6. H. Stein,
    7. M. Lipp
    . 2002. Up-regulation of the chemokine receptor CCR7 in classical but not in lymphocyte-predominant Hodgkin disease correlates with distinct dissemination of neoplastic cells in lymphoid organs. Blood 99: 1109–1116.
    OpenUrlAbstract/FREE Full Text
  51. ↵
    1. Angeli V.,
    2. H. Hammad,
    3. B. Staels,
    4. M. Capron,
    5. B. N. Lambrecht,
    6. F. Trottein
    . 2003. Peroxisome proliferator-activated receptor γ inhibits the migration of dendritic cells: consequences for the immune response. J. Immunol. 170: 5295–5301.
    OpenUrlAbstract/FREE Full Text
  52. ↵
    1. Fainaru O.,
    2. D. Shseyov,
    3. S. Hantisteanu,
    4. Y. Groner
    . 2005. Accelerated chemokine receptor 7-mediated dendritic cell migration in Runx3 knockout mice and the spontaneous development of asthma-like disease. Proc. Natl. Acad. Sci. USA 102: 10598–10603.
    OpenUrlAbstract/FREE Full Text
  53. ↵
    1. Villablanca E. J.,
    2. L. Raccosta,
    3. D. Zhou,
    4. R. Fontana,
    5. D. Maggioni,
    6. A. Negro,
    7. F. Sanvito,
    8. M. Ponzoni,
    9. B. Valentinis,
    10. M. Bregni,
    11. et al
    . 2010. Tumor-mediated liver X receptor-α activation inhibits CC chemokine receptor-7 expression on dendritic cells and dampens antitumor responses. Nat. Med. 16: 98–105.
    OpenUrlCrossRefPubMed
  54. ↵
    1. Bajaña S.,
    2. K. Roach,
    3. S. Turner,
    4. J. Paul,
    5. S. Kovats
    . 2012. IRF4 promotes cutaneous dendritic cell migration to lymph nodes during homeostasis and inflammation. J. Immunol. 189: 3368–3377.
    OpenUrlAbstract/FREE Full Text
  55. ↵
    1. Kim S. J.,
    2. J. Y. Shin,
    3. K. D. Lee,
    4. Y. K. Bae,
    5. K. W. Sung,
    6. S. J. Nam,
    7. K. H. Chun
    . 2012. MicroRNA let-7a suppresses breast cancer cell migration and invasion through downregulation of C-C chemokine receptor type 7. Breast Cancer Res. 14: R14.
    OpenUrlCrossRefPubMed
  56. ↵
    1. Smigielska-Czepiel K.,
    2. A. van den Berg,
    3. P. Jellema,
    4. I. Slezak-Prochazka,
    5. H. Maat,
    6. H. van den Bos,
    7. R. J. van der Lei,
    8. J. Kluiver,
    9. E. Brouwer,
    10. A. M. Boots,
    11. B. J. Kroesen
    . 2013. Dual role of miR-21 in CD4+ T-cells: activation-induced miR-21 supports survival of memory T-cells and regulates CCR7 expression in naive T-cells. PLoS One 8: e76217.
    OpenUrlCrossRefPubMed
View Abstract
Back to top

In this issue

Print
Download PDF
Article Alerts
Email Article
Citation Tools

Jump to section