We are grateful to Drs. Markus Manz and Irving Weissman for providing reagents. We also acknowledge the service provided by the Flow Cytometric Analysis and Cell Sorting Core Facility of the First and Second Core Laboratory at National Taiwan University College of Medicine and NTU hospital, respectively. This work was supported by the Ministry of Science and Technology, Taiwan (MOST 102-2320-B-002-030-MY3) and the National Health Research Institutes, Taiwan (NHRI-EX102-10256SI and NHRI-EX103-10256SI).

C57BL/6 wild-type mice were purchased from the National Laboratory Animal Center (NLAC), Taiwan. All mice were bred and kept under specific pathogen-free conditions. Protocols and animal use procedures were reviewed and approved by the Institutional Animal Care and Use Committee of National Taiwan University College of Medicine (Permit Number: 20120075). In addition, researchers made every effort to reduce the potential for pain, suffering, or distress in the animals while performing experiments. All procedures described were carried out at RT while wearing gloves.
1. Preparation of AC-6 Feeder cells
Note: The AC-6.21 (AC-6 in short) stromal cell line18 (provided by I. Weissman, Stanford University) should be maintained in RPMI supplemented with 15% heat-inactivated fetal bovine serum (FBS). To serve as feeder cells, AC-6 cells are &#947;-irradiated with 3,000 rad (30Gy) one day before the co-culture to prevent their proliferation. Note that AC-6 cells tend to lose their differentiation-supporting ability if left overcrowded during maintenance, or if their passage number is over 20.
<ol>
	<li>Wash AC-6 cells once with 1 ml Dulbecco&#39;s Phosphate-Buffered Saline (DPBS) and remove DPBS by aspiration. Treat AC-6 cells with 0.8 ml trypsin solution (0.05 % trypsin and 0.5 mM EDTA in DPBS) for 3-5 min at 37oC, 5% CO2 and then stop the reaction by diluting it with 10 volumes of culture medium to make single cell suspension.</li>
	<li>Seed AC-6 cells at 5.9x104 cells/well into 12-well plates and incubate at 37oC, 5% CO2 O/N. 
	Note: The density of AC-6 cells is very important as a lower density will favor cDC generation. Seeding at a density of 5.9x104 cells/well will allow AC-6 to reach confluency by the next day, which is optimal for derivation of pDCs from CLPs.</li>
	<li>Irradiate AC-6 cells at 3,000 rad (30 Gy) using &#947;-irradiator. 
	Note: The dose used to irradiate AC-6 is optimized to prevent the cells from proliferating and yet keep them viable long enough to provide the cytokines and cell-cell contact required for differentiation of DCs from CLPs.</li>
	<li>Aspirate medium and replace with 1 ml complete RPMI (RPMI with 10 % heat-inactivated FBS, 50 &#181;g/ml gentamycin and 50 &#181;M &#946;-mercaptoethanol).</li>
</ol>
2. Isolate BM Cells from Mice
<ol>
	<li>Sacrifice mice by CO2 asphyxiation and cervical dislocation. Place the mice on a dissection tray and sterilize with 70% ethanol. Make an incision at the mid-abdomen and remove the skin from the distal part of the mouse including the skin covering the lower extremities.</li>
	<li>Dissect mice in a semi-sterile hood. To release the femur and tibiae, clip the femur above and tibiae below the knee joint. Detach the muscles from the bones using scissors and place the bones in a 6 cm petri dish containing 5 ml complete RPMI.</li>
	<li>Move to a sterile culture hood. Fill a 3 ml syringe connected to a 27G needle with complete RPMI. Cut off both ends of the bones using scissors, and insert the 27G needle to flush the marrow out of the bones by gently injecting complete RPMI once from each end.</li>
	<li>Prepare a single cell suspension by gentle pipetting the cells up and down 3-5 times in the culture dish using the syringe without the needle.</li>
	<li>Centrifuge the cells for 5 min at 500 x g and decant the supernatant.</li>
	<li>Lyse red blood cells with 1 ml ACK buffer (150 mM NH4Cl, 10 mM KHCO3, 0.1 mM EDTA) incubating for 1 min and stopping the reaction by diluting with 10 volumes of complete RPMI. Allow cells to stand for 5 min in order to pellet down dead cell clumps and tissue debris by gravity. 
	Note: Do not stand more than 5 min as this will result in cell loss due to settling of viable cells.</li>
	<li>Slowly decant cell-containing supernatant to a new tube leaving debris behind in the original tube.</li>
	<li>Centrifuge for 5 min at 500 x g to pellet the cells, then remove and discard the supernatant.</li>
	<li>Resuspend total BM cells (typically 4-6 x 107 BM cells are obtained from one mouse) in 100 &#181;l FACS buffer (1x PBS+ 2% FBS+ 1mM EDTA).</li>
</ol>
3. FACS Analysis and Sorting of CLPs
<ol>
	<li>Add anti-CD16/32 (hybridoma supernant clone 2.4G2, 50 &#181;l/reaction or 1-2 &#181;g/reaction) into cells in FACS buffer (step 2.9) for 1-2 min in order to block Fc receptors. 
	Note: Anti-CD16/32 is also called Fc block, which is added to prevent non-specific binding of antibodies to cells expressing Fc receptors including granulocytes, monocytes, and B lymphocytes.</li>
	<li>Simultaneously stain cells with the following fluorescent dye-labeled antibodies (for 4x107 cells) for 15 min on ice, avoiding ambient light. Antibodies: PE-conjugated lineage markers (0.2 &#181;g each) including anti-CD3 (17A2), anti-CD8 (53-6.7), anti-B220 (RA3-6B2), anti-CD19 (eBio1D3), anti-CD11b (M1/70), anti-Gr-1 (RB6-8C5), anti-Thy1.1 (HIS51), anti-NK1.1 (PK136), anti-TER119 (TER-119), and anti-MHC-II (NIMR-4), 0.2 &#181;g anti-c-Kit-PerCP-Cy5.5 (2B8), 1 &#181;g anti-Sca-1-FITC (D7), 0.4 &#181;g anti-M-CSFR-APC (AFS98), and 0.2 &#181;g anti-IL-7R&#945;-PE-Cy7 (A7R34).</li>
	<li>Wash cells with 3 ml FACS buffer, and centrifuge for 5 min at 500 x g.</li>
	<li>Resuspend the cells in 300 &#181;l FACS buffer and filter cells through a 40 &#181;M cell strainer.</li>
	<li>Wash the tube with an additional 100 &#181;l FACS buffer to recover any remaining cells and filter into a sterile FACS sorting tube using the same cell strainer.</li>
	<li>Perform flow cytometric analysis immediately after the staining using appropriate filters and voltages for signal detection. Use 488 nm laser to detect the FITC-, PerCP-Cy5.5-labeled antibodies, 561 nm laser to detect the PE- and PE-Cy7-labelded antibodies and 633 nm laser to detect the APC-labeled antibody.</li>
	<li>Sort out CLPs according to the following markers lin-c-kitintSca-1intM-CSFR-IL-7R&#945;+ (as stained in step 3.2) using a cell sorter. Collect the sorted cells in a 15 ml tube containing 8 ml of complete RPMI as a cushion.</li>
	<li>Record the absolute number of sorted cells as shown by the cell sorter at the end of the run. Typically, 5x104 CLPs can be obtained from the BM of one mouse.</li>
</ol>
4. Coculture CLPs and AC-6
<ol>
	<li>Centrifuge the sorted cells from step 3.7 for 10 min at 500 x g, remove the supernatant and resuspend the cell pellet with enough complete RPMI to obtain a cell density around 5x104 cells/ml. Seed 500 cells/well into the 12-well plate containing feeder cells prepared in step 1.4.</li>
	<li>Add 100 ng/ml FL19 (hu-Flt3L-Ig generated in-house using an expression system provided by M. Manz, University Hospital Z&#252;rich, Switzerland) and incubate at 37oC, 5% CO2 with periodic visual monitoring of DC development under a microscope. 
	Note: Commercially available recombinant human FL or mouse FL can be used as a substitute for hu-Flt3L-Ig to support DC development.</li>
	<li>Collect the cells in the supernatant at day 12 and wash the wells once with 0.5 ml complete RPMI medium combining the resulting supernatants. Add 0.5 ml fresh medium and scrap the adherent cells with a cell scraper.</li>
	<li>Combine the cell-containing medium from both parts and centrifuge for 5 min at 500 x g.</li>
	<li>Decant supernatant and resuspend cells in 50 &#181;l FACS buffer. Add 50 &#181;l anti-CD16/32 hybridoma supernatant and incubate for 1-2 min to block Fc receptors.</li>
	<li>Enumerate and stain all the cells with the following antibodies (0.05 &#181;g each) anti-CD11c-APC (N418), anti-CD11b-FITC, and anti-B220-PE.</li>
	<li>Wash and centrifuge the cells as described in step 3.3.</li>
	<li>Resuspend the cells in 100 &#181;l FACS buffer, gate on CD11c+ and analyze for cDCs (CD11c+CD11b+B220-) and pDCs (CD11c+CD11b-B220+)17.</li>
</ol>

<ol>
	<li>Hartwig, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fcgamma+receptor-mediated+antigen+uptake+by+lung+DC+contributes+to+allergic+airway+hyper-responsiveness+and+inflammation.">Fcgamma receptor-mediated antigen uptake by lung DC contributes to allergic airway hyper-responsiveness and inflammation.</a> Eur. J. Immunol. 40, 1284-1295 (2010).</li><li>Merad, M., Sathe, P., Helft, J., Miller, J., Mortha, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+dendritic+cell+lineage:+ontogeny+and+function+of+dendritic+cells+and+their+subsets+in+the+steady+state+and+the+inflamed+setting.">The dendritic cell lineage: ontogeny and function of dendritic cells and their subsets in the steady state and the inflamed setting.</a> Annu. Rev. Immunol. 31, 563-604 (2013).</li><li>Mildner, A., Jung, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+and+Function+of+Dendritic+Cell+Subsets.">Development and Function of Dendritic Cell Subsets.</a> Immunity. 40, 642-656 (2014).</li><li>Swiecki, M., Colonna, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unraveling+the+functions+of+plasmacytoid+dendritic+cells+during+viral+infections,+autoimmunity,+and+tolerance.">Unraveling the functions of plasmacytoid dendritic cells during viral infections, autoimmunity, and tolerance.</a> Immunol. Rev. 234, 142-162 (2010).</li><li>Liu, Y. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=IPC:+professional+type+1+interferon-producing+cells+and+plasmacytoid+dendritic+cell+precursors.">IPC: professional type 1 interferon-producing cells and plasmacytoid dendritic cell precursors.</a> Annu. Rev. Immunol. 23, 275-306 (2005).</li><li>Merad, M., Manz, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dendritic+cell+homeostasis.">Dendritic cell homeostasis.</a> Blood. 113, 3418-3427 (2009).</li><li>Ghosh, H. S., Cisse, B., Bunin, A., Lewis, K. L., Reizis, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Continuous+expression+of+the+transcription+factor+e2-2+maintains+the+cell+fate+of+mature+plasmacytoid+dendritic+cells.">Continuous expression of the transcription factor e2-2 maintains the cell fate of mature plasmacytoid dendritic cells.</a> Immunity. 33, 905-916 (2010).</li><li>Karsunky, H., Merad, M., Cozzio, A., Weissman, I. L., Manz, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flt3+ligand+regulates+dendritic+cell+development+from+Flt3++lymphoid+and+myeloid-committed+progenitors+to+Flt3++dendritic+cells+in+vivo.">Flt3 ligand regulates dendritic cell development from Flt3+ lymphoid and myeloid-committed progenitors to Flt3+ dendritic cells in vivo.</a> J. Exp. Med. 198, 305-313 (2003).</li><li>Manz, M. G., Traver, D., Miyamoto, T., Weissman, I. L., Akashi, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dendritic+cell+potentials+of+early+lymphoid+and+myeloid+progenitors.">Dendritic cell potentials of early lymphoid and myeloid progenitors.</a> Blood. 97, 3333-3341 (2001).</li><li>D'Amico, A., Wu, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+early+progenitors+of+mouse+dendritic+cells+and+plasmacytoid+predendritic+cells+are+within+the+bone+marrow+hemopoietic+precursors+expressing+Flt3.">The early progenitors of mouse dendritic cells and plasmacytoid predendritic cells are within the bone marrow hemopoietic precursors expressing Flt3.</a> J. Exp. Med. 198, 293-303 (2003).</li><li>Sathe, P., Vremec, D., Wu, L., Corcoran, L., Shortman, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Convergent+differentiation:+myeloid+and+lymphoid+pathways+to+murine+plasmacytoid+dendritic+cells.">Convergent differentiation: myeloid and lymphoid pathways to murine plasmacytoid dendritic cells.</a> Blood. 121, 11-19 (2013).</li><li>Shigematsu, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plasmacytoid+dendritic+cells+activate+lymphoid-specific+genetic+programs+irrespective+of+their+cellular+origin.">Plasmacytoid dendritic cells activate lymphoid-specific genetic programs irrespective of their cellular origin.</a> Immunity. 21, 43-53 (2004).</li><li>Reizis, B., Bunin, A., Ghosh, H. S., Lewis, K. L., Sisirak, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plasmacytoid+dendritic+cells:+recent+progress+and+open+questions.">Plasmacytoid dendritic cells: recent progress and open questions.</a> Annu. Rev. Immunol. 29, 163-183 (2011).</li><li>Inaba, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Generation+of+large+numbers+of+dendritic+cells+from+mouse+bone+marrow+cultures+supplemented+with+granulocyte/macrophage+colony-stimulating+factor.">Generation of large numbers of dendritic cells from mouse bone marrow cultures supplemented with granulocyte/macrophage colony-stimulating factor.</a> J. Exp. Med. 176, 1693-1702 (1992).</li><li>Naik, S. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+plasmacytoid+and+conventional+dendritic+cell+subtypes+from+single+precursor+cells+derived+in+vitro+and+in+vivo.">Development of plasmacytoid and conventional dendritic cell subtypes from single precursor cells derived in vitro and in vivo.</a> Nat. Immunol. 8, 1217-1226 (2007).</li><li>Onai, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+clonogenic+common+Flt3+M-CSFR++plasmacytoid+and+conventional+dendritic+cell+progenitors+in+mouse+bone+marrow.">Identification of clonogenic common Flt3+M-CSFR+ plasmacytoid and conventional dendritic cell progenitors in mouse bone marrow.</a> Nat. Immunol. 8, 1207-1216 (2007).</li><li>Chen, Y. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+type+I+IFN-Flt3+ligand+axis+augments+plasmacytoid+dendritic+cell+development+from+common+lymphoid+progenitors.">A type I IFN-Flt3 ligand axis augments plasmacytoid dendritic cell development from common lymphoid progenitors.</a> J. Exp. Med. 210, 2515-2522 (2013).</li><li>Whitlock, C. A., Tidmarsh, G. F., Muller-Sieburg, C., Weissman, I. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bone+marrow+stromal+cell+lines+with+lymphopoietic+activity+express+high+levels+of+a+pre-B+neoplasia-associated+molecule.">Bone marrow stromal cell lines with lymphopoietic activity express high levels of a pre-B neoplasia-associated molecule.</a> Cell. 48, 1009-1021 (1987).</li><li>Onai, N., Obata-Onai, A., Tussiwand, R., Lanzavecchia, A., Manz, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Activation+of+the+Flt3+signal+transduction+cascade+rescues+and+enhances+type+I+interferon-producing+and+dendritic+cell+development.">Activation of the Flt3 signal transduction cascade rescues and enhances type I interferon-producing and dendritic cell development.</a> J. Exp. Med. 203, 227-238 (2006).</li><li>Szilvassy, S. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Leukemia+inhibitory+factor+upregulates+cytokine+expression+by+a+murine+stromal+cell+line+enabling+the+maintenance+of+highly+enriched+competitive+repopulating+stem+cells.">Leukemia inhibitory factor upregulates cytokine expression by a murine stromal cell line enabling the maintenance of highly enriched competitive repopulating stem cells.</a> Blood. 87, 4618-4628 (1996).</li><li>Arcanjo, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biochemical+characterization+of+heparan+sulfate+derived+from+murine+hemopoietic+stromal+cell+lines:+a+bone+marrow-derived+cell+line+S17+and+a+fetal+liver-derived+cell+line+AFT024.">Biochemical characterization of heparan sulfate derived from murine hemopoietic stromal cell lines: a bone marrow-derived cell line S17 and a fetal liver-derived cell line AFT024.</a> J. Cell. Biochem. 87, 160-172 (2002).</li><li>Onai, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+clonogenic+progenitor+with+prominent+plasmacytoid+dendritic+cell+developmental+potential.">A clonogenic progenitor with prominent plasmacytoid dendritic cell developmental potential.</a> Immunity. 38, 943-957 (2013).</li><li>Whitlock, C. A., Muller-Sieburg, C. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-term+B-lymphoid+cultures+from+murine+bone+marrow+establishment+and+cloning+by+using+stromal+cell+line+AC+6.21.">Long-term B-lymphoid cultures from murine bone marrow establishment and cloning by using stromal cell line AC 6.21.</a> Methods Mol. Biol. 75, 231-248 (1997).</li><li>Chen, Y. -. L., Chang, S., Chen, T. -. T., Lee, C. -. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient+Generation+of+Plasmacytoid+Dendritic+Cell+from+Common+Lymphoid+Progenitors+by+Flt3+Ligand.">Efficient Generation of Plasmacytoid Dendritic Cell from Common Lymphoid Progenitors by Flt3 Ligand.</a> PLoS ONE. 10 (8), e0135217 (2015).</li></ol>

Authors have nothing to disclose.

Here we describe an in vitro culture system for the robust generation of DCs, and pDCs in particular, from a small number of CLPs. The uniqueness of this culture system is due to the use of AC-6 cells, a stromal cell line, as feeders. This approach has been shown to provide not only the cytokines, such as IL-7, SCF, M-CSF and FL20, but also the cell-cell contact21 necessary to support DC development. AC-6 cells have been used previously to facilitate the study of in vitro DC develo...

Dendritic cells (DCs) are professional antigen-presenting cells that play an important role in controlling immune responses1. While DCs are heterogeneous, they can be broadly classified into two populations, conventional DCs (cDCs) and plasmacytoid DCs (pDCs)2,3. In addition to lymphoid organs, cDCs and pDCs are also found in tissues including lung, intestine, and skin2. The morphology of cDCs and pDCs differs, with cDCs exhibiting dendrite-like projections and the shape of pDCs being more plasma cell-like. In addition, the common mouse DC marker, CD11c, is more highly expressed on cDCs than on pDCs. Moreover, cDCs can be further divided into CD11b+CD24- cDCs and CD11b-CD24+ cDCs, both of which express higher levels of MHC class II and costimulatory molecules than do pDCs2. Mature pDCs, on the other hand, have been shown to selectively express Siglec-H and BST24. Functionally, cDCs are better antigen presenting cells than are pDCs; however, pDCs can produce a vast amount of type I interferon upon virus infection or inflammatory stimulation5.
Both cDCs and pDCs are short-lived, and therefore, must be constantly replenished from progenitors within the bone marrow (BM)6,7. Adoptive transfer of common myeloid progenitors (CMPs) and common lymphoid progenitors (CLPs) into lethally-irradiated mice demonstrates that cDCs and pDCs can be generated from both lineages8-10. However, there is a subset of pDCs that express RAG1/2 and possess rearranged D-J segments at the IgH locus11,12. These cells also share molecular similarities with B lymphocytes, including expression of the B220 marker, nucleic acid-sensing receptors (TLR7/TLR9), and transcription factors (Spib and Bcl11a)13, features all believed to be signatures of the lymphoid lineage. Therefore, CLPs may be good choices for in vitro generation of pDCs because of lineage similarity.
While the frequency of both cDCs and pDCs in humans and mice is very low6, DCs, particularly cDCs, can be generated in vitro from BM or progenitors in the presence of cytokines, such as GM-CSF11,14 or Flt3 ligand (FL) using feeder-free systems 11,15,16. Unfortunately, however, it is not possible to produce large numbers of pDCs in vitro using FL11,15,16. Previously we demonstrated that pDCs can be efficiently generated in vitro from CLPs using the AC-6 feeder system17. The advantage of using the AC-6 stromal cell line in the culture system is that it provides cell-cell contact and secretion of cytokines that support the generation of large numbers of pDCs from CLPs. Although production with this system is quite robust, careful replication of the procedures described below is required in order to ensure efficient generation of pDCs.

<table>
	<tbody>
		<tr>
			<td>Anti-mouse Ly6g/Ly6c (PE), clone RB6-8C5</td>
			<td>Biolegend</td>
			<td>108408</td>
			<td>linage marker</td>
		</tr>
		<tr>
			<td>Anti-mouse NK1.1 (PE), clone PK136</td>
			<td>Biolegend</td>
			<td>108708</td>
			<td>linage marker</td>
		</tr>
		<tr>
			<td>Anti-mouse&#160; CD11b (PE), cloneM1/70</td>
			<td>Biolegend</td>
			<td>101208</td>
			<td>linage marker</td>
		</tr>
		<tr>
			<td>Anti-mouse CD19 (PE), clone eBio1D3</td>
			<td>Biolegend</td>
			<td>115508</td>
			<td>linage marker</td>
		</tr>
		<tr>
			<td>Anti-mouse B220 (PE), clone RA3-6B2</td>
			<td>Biolegend</td>
			<td>103208</td>
			<td>linage marker/FACS</td>
		</tr>
		<tr>
			<td>Anti-mouse CD3 (PE), clone 17A2</td>
			<td>Biolegend</td>
			<td>100308</td>
			<td>linage marker</td>
		</tr>
		<tr>
			<td>Anti-mouse CD8a (PE), clone 53-6.7</td>
			<td>Biolegend</td>
			<td>100707</td>
			<td>linage marker</td>
		</tr>
		<tr>
			<td>Anti-mouse MHC-II (PE), clone NIMR-4</td>
			<td>Biolegend</td>
			<td>107608</td>
			<td>linage marker</td>
		</tr>
		<tr>
			<td>Anti-mouse Ter119 (PE), clone TER-119</td>
			<td>Biolegend</td>
			<td>116208</td>
			<td>linage marker</td>
		</tr>
		<tr>
			<td>Anti-mouse Thy1.1 (PE), clone HIS51</td>
			<td>eBioscience</td>
			<td>12-0900-83</td>
			<td>linage marker</td>
		</tr>
		<tr>
			<td>Anti-mouse M-CSFR (APC), clone AFS98</td>
			<td>Biolegend</td>
			<td>135510</td>
			<td>FACS</td>
		</tr>
		<tr>
			<td>Anti-mouse c-Kit (PerCP/Cy5.5), clone 2B8</td>
			<td>Biolegend</td>
			<td>105824</td>
			<td>FACS</td>
		</tr>
		<tr>
			<td>Anti-mouse Sca-1 (FITC), clone D7</td>
			<td>Biolegend</td>
			<td>108106</td>
			<td>FACS</td>
		</tr>
		<tr>
			<td>Anti-mouse IL-7Ra (PE/Cy7), clone A7R34</td>
			<td>Biolegend</td>
			<td>135014</td>
			<td>FACS</td>
		</tr>
		<tr>
			<td>Anti-mouse CD11c (PerCP/Cy5.5), clone N418</td>
			<td>Biolegend</td>
			<td>117328</td>
			<td>FACS</td>
		</tr>
		<tr>
			<td>Anti-mouse CD11b (FITC), clone M1/70</td>
			<td>Biolegend</td>
			<td>101206</td>
			<td>FACS</td>
		</tr>
		<tr>
			<td>FACSAria III</td>
			<td>BD Biosciences</td>
			<td></td>
			<td>Cell sorter</td>
		</tr>
		<tr>
			<td>FACS sorting tube&#160;</td>
			<td>BD Biosciences</td>
			<td>352054</td>
			<td></td>
		</tr>
		<tr>
			<td>FlowJo</td>
			<td>FlowJo LLC</td>
			<td></td>
			<td>Flow analysis sofrware</td>
		</tr>
	</tbody>
</table>

in vitro generation of murine plasmacytoid dendritic cells from common lymphoid progenitors using the ac-6 feeder system

Plasmacytoid dendritic cells (pDCs) are powerful type I interferon (IFN-I) producing cells that are activated in response to infection or during inflammatory responses. Unfortunately, study of pDC function is hindered by their low frequency in lymphoid organs, and existing methods for in vitro DC generation predominantly favor the production of cDCs over pDCs. Here we present a unique approach to efficiently generate pDCs from common lymphoid progenitors (CLPs) in vitro. Specifically, the protocol described details how to purify CLPs from bone marrow and generate pDCs by coculturing with &#947;-irradiated AC-6 feeder cells in the presence of Flt3 ligand. A unique characteristic of this culture system is that the CLPs migrate underneath the AC-6 cells and become cobblestone area-forming cells, a critical step for expanding pDCs. Morphologically distinct DCs, namely pDCs and cDCs, were generated after approximately 2 weeks with a composition of 70-90% pDCs under optimal conditions. Typically, the number of pDCs generated by this method is roughly 100-fold of the number of CLPs seeded. Therefore, this is a novel system with which to robustly generate the large numbers of pDCs required to facilitate further studies into the development and function of these cells.

A total of 4-6x107 BM cells are typically isolated from femurs and tibiae of one 6-8 wk-old, wild-type C57BL/6 mouse. To sort out CLPs, total BM cells are stained with PE-conjugated antibodies against lineage markers (CD3, CD8, B220, CD19, CD11b, Gr-1, Thy1.1, NK1.1, TER119, and MHC-II), anti-c-Kit-PerCP/Cy5.5, anti-Sca-1-FITC, anti-M-CSFR-APC and anti-IL-7R&#945;-PE/Cy7, analyzed and sorted with a cell sorter. The sorting strategy for CLP is shown in Figure 1. Typically, 5x104 CLPs...

Watch this Scientific Journal Video about In Vitro Generation of Murine Plasmacytoid Dendritic Cells from Common Lymphoid Progenitors using the AC-6 Feeder System at JoVE.com

In Vitro Generation of Murine Plasmacytoid Dendritic Cells from Common Lymphoid Progenitors using the AC-6 Feeder System

In this study we present an in vitro culture system that can efficiently generate pDCs by co-culturing common lymphoid progenitors with AC-6 feeder cells in the presence of Flt3 ligand.

In Vitro Generation of Murine Plasmacytoid Dendritic Cells from Common Lymphoid Progenitors using the AC-6 Feeder System

Plasmacytoid dendritic cells (pDCs) are powerful type I interferon (IFN-I) producing cells that are activated in response to infection or during ...

in-vitro-generation-murine-plasmacytoid-dendritic-cells-from-common

Research

JoVE Journal

Immunology and Infection

8.3K vistas.  National Taiwan University College of Medicine. In this study we present an in vitro culture system that can efficiently generate pDCs by co-culturing common lymphoid progenitors with AC-6 feeder cells in the presence of Flt3 ligand. 

Video: In Vitro Generation of Murine Plasmacytoid Dendritic Cells from Common Lymphoid Progenitors using the AC-6 Feeder System

Generation and Labeling of Murine Bone Marrow-derived Dendritic Cells with Qdot Nanocrystals for Tracking Studies

Dendritic cells (DCs) are professional antigen presenting cells (APCs) found in peripheral tissues and in immunological organs such as thymus, bone marrow, spleen, lymph nodes and Peyer's patches 1-3. DCs present in peripheral tissues sample the organism for the presence of antigens, which they take up, process and present in their surface in the context of major histocompatibility molecules (MHC). Then, antigen-loaded DCs migrate to immunological organs where they present the processed antigen to T lymphocytes triggering specific immune responses. One way to evaluate the migratory capabilities of DCs is to label them with fluorescent dyes 4.
Herewith we demonstrate the use of Qdot fluorescent nanocrystals to label murine bone marrow-derived DC. The advantage of this labeling is that Qdot nanocrystals possess stable and long lasting fluorescence that make them ideal for detecting labeled cells in recovered tissues. To accomplish this, first cells will be recovered from murine bone marrows and cultured for 8 days in the presence of granulocyte macrophage-colony stimulating factor in order to induce DC differentiation. These cells will be then labeled with fluorescent Qdots by short in vitro incubation. Stained cells can be visualized with a fluorescent microscopy. Cells can be injected into experimental animals at this point or can be into mature cells upon in vitro incubation with inflammatory stimuli. In our hands, DC maturation did not determine loss of fluorescent signal nor does Qdot staining affect the biological properties of DCs. Upon injection, these cells can be identified in immune organs by fluorescent microscopy following typical dissection and fixation procedures.

Dendritic cells uptake antigens and migrate towards immune organs to present processed antigens to T cells. Qdot nanocrystal labeling provides a long-lasting and stable fluorescent signal. This allows tracking of dendritic cells to different organs by fluorescent microscopy.

Dendritic cells (DCs) are professional antigen presenting cells (APCs) found in peripheral tissues and in immunological organs such as thymus, bone ...

Isolating And Immunostaining Lymphocytes and Dendritic Cells from Murine Peyer's Patches

Peyer's patches (PPs) are integral components of the gut-associated lymphoid tissues (GALT) and play a central role in intestinal immunosurveillance and homeostasis. Particulate antigens and microbes in the intestinal lumen are continuously sampled by PP M cells in the follicle-associated epithelium (FAE) and transported to an underlying network of dendritic cells (DCs), macrophages, and lymphocytes. In this article, we describe protocols in which murine PPs are (i) dissociated into single cell suspensions and subjected to flow cytometry and (ii) prepared for cryosectioning and immunostaining. For flow cytometry, PPs are mechanically dissociated and then filtered through 70 &mu;m membranes to generate single cell suspensions free of epithelial cells and large debris. Starting with 20-25 PPs (from four mice), this quick and reproducible method yields a population of &gt;2.5 x 106 cells with &gt;90% cell viability. For cryosectioning, freshly isolated PPs are immersed in Optimal Cutting Temperature (OCT) medium, snap-frozen in liquid nitrogen, and then sectioned using a cryomicrotome. Tissue sections (5-12 &mu;m) are air-dried, fixed with acetone or methanol, and then subjected to immunolabeling.

Isolating And Immunostaining Lymphocytes and Dendritic Cells from Murine Peyer&#039;s Patches

There is an increasing interest in understanding the immunological functions of specific subpopulations of cells in Peyer's patches (PPs), the primary inductive sites of gut-associated lymphoid tissues. Here we outline parallel protocols for preparing PP single cell preparations for flow cytometric analysis and PP cryosections for immunostaining.

Peyer's  patches (PPs) are integral components of the gut-associated lymphoid tissues  (GALT) and play a central role in intestinal immunosurveillance and ...

Generation of a Novel Dendritic-cell Vaccine Using Melanoma and Squamous Cancer Stem Cells

We identified cancer stem cell (CSC)-enriched populations from murine melanoma D5 syngeneic to C57BL/6 mice and the squamous cancer SCC7 syngeneic to C3H mice using ALDEFLUOR/ALDH as a marker, and tested their immunogenicity using the cell lysate as a source of antigens to pulse dendritic cells (DCs). DCs pulsed with ALDHhigh CSC lysates induced significantly higher protective antitumor immunity than DCs pulsed with the lysates of unsorted whole tumor cell lysates in both models and in a lung metastasis setting and a s.c.&#160;tumor growth setting, respectively. This phenomenon was due to CSC vaccine-induced humoral as well as cellular anti-CSC responses. In particular, splenocytes isolated from the host subjected to CSC-DC vaccine produced significantly higher amount of IFN&#947; and GM-CSF than splenocytes isolated from the host subjected to unsorted tumor cell lysate pulsed-DC vaccine. These results support the efforts to develop an autologous CSC-based therapeutic vaccine for clinical use in an adjuvant setting.

Evaluated in syngeneic immunocompetent hosts, cancer stem cell (CSC) based dendritic cell (DC) vaccine demonstrated significantly higher antitumor immunity than traditional DC vaccines pulsed with heterogeneous bulk tumor cells.

We identified cancer stem cell (CSC)-enriched populations from murine melanoma D5 syngeneic to C57BL/6 mice and the squamous cancer SCC7 syngeneic to C3H ...

Assessing the Development of Murine Plasmacytoid Dendritic Cells in Peyer's Patches Using Adoptive Transfer of Hematopoietic Progenitors

This protocol details a method to analyze the ability of purified hematopoietic progenitors to generate plasmacytoid dendritic cells (pDC) in intestinal Peyer&#39;s patch (PP). Common dendritic cell progenitors (CDPs, lin- c-kitlo CD115+ Flt3+) were purified from the bone marrow of C57BL6 mice by FACS and transferred to recipient mice that lack a significant pDC population in PP; in this case, Ifnar-/- mice were used as the transfer recipients. In some mice, overexpression of the dendritic cell growth factor Flt3 ligand (Flt3L) was enforced prior to adoptive transfer of CDPs, using hydrodynamic gene transfer (HGT) of Flt3L-encoding plasmid. Flt3L overexpression expands DC populations originating from transferred (or endogenous) hematopoietic progenitors. At 7-10 days after progenitor transfer, pDCs that arise from the adoptively transferred progenitors were distinguished from recipient cells on the basis of CD45 marker expression, with pDCs from transferred CDPs being CD45.1+ and recipients being CD45.2+. The ability of transferred CDPs to contribute to the pDC population in PP and to respond to Flt3L was evaluated by flow cytometry of PP single cell suspensions from recipient mice. This method may be used to test whether other progenitor populations are capable of generating PP pDCs. In addition, this approach could be used to examine the role of factors that are predicted to affect pDC development in PP, by transferring progenitor subsets with an appropriate knockdown, knockout or overexpression of the putative developmental factor and/or by manipulating circulating cytokines via HGT. This method may also allow analysis of how PP pDCs affect the frequency or function of other immune subsets in PPs. A unique feature of this method is the use of Ifnar-/- mice, which show severely depleted PP pDCs relative to wild type animals, thus allowing reconstitution of PP pDCs in the absence of confounding effects from lethal irradiation.

Assessing the Development of Murine Plasmacytoid Dendritic Cells in Peyer&#039;s Patches Using Adoptive Transfer of Hematopoietic Progenitors

This protocol describes experimental procedures to assess the differentiation of plasmacytoid dendritic cells in Peyer&#8217;s patch from common dendritic cell progenitors, using techniques involving FACS-mediated cell isolation, hydrodynamic gene transfer, and flow analysis of immune subsets in Peyer&#8217;s patch.

This protocol details a method to analyze the ability of purified hematopoietic progenitors to generate plasmacytoid dendritic cells (pDC) in intestinal ...

Assessing the Innate Sensing of HIV-1 Infected CD4+ T Cells by Plasmacytoid Dendritic Cells Using an Ex vivo Co-culture System.

HIV-1 innate sensing requires direct contact of infected CD4+ T cells with plasmacytoid dendritic cells (pDCs). In order to study this process, the protocols described here use freshly isolated human peripheral blood mononuclear cells (PBMCs) or plasmacytoid dendritic cells (pDCs) to sense infections in either T cell line (MT4) or heterologous primary CD4+ T cells. In order to ensure proper sensing, it is essential that PBMC are isolated immediately after blood collection and that optimal percentage of infected T cells are used. Furthermore, multi-parametric flow cytometric staining can be used to confirm that PBMC samples contain the different cell lineages at physiological ratios. A number of controls can also be included to evaluate viability and functionality of pDCs. These include, the presence of specific surface markers, assessing cellular responses to known agonist of Toll-Like Receptors (TLR) pathways, and confirming a lack of spontaneous type-I interferon (IFN) production. In this system, freshly isolated PBMCs or pDCs are co-cultured with HIV-1 infected cells in 96 well plates for 18-22 hr. Supernatants from these co-cultures are then used to determine the levels of bioactive type-I IFNs by monitoring the activation of the ISGF3 pathway in HEK-Blue IFN-&#945;/&#946; cells. Prior and during co-culture conditions, target cells can be subjected to flow cytometric analysis to determine a number of parameters, including the percentage of infected cells, levels of specific surface markers, and differential killing of infected cells. Although, these protocols were initially developed to follow type-I IFN production, they could potentially be used to study other imuno-modulatory molecules released from pDCs and to gain further insight into the molecular mechanisms governing HIV-1 innate sensing.

Assessing the Innate Sensing of HIV-1 Infected CD4+ T Cells by Plasmacytoid Dendritic Cells Using an Ex vivo Co-culture System.

Unlike cell-free HIV-1 particles, infected CD4+ T cells are effectively sensed by plasmacytoid dendritic cells (pDCs). This manuscript describes a method where peripheral blood mononuclear cells (PBMCs) or isolated pDCs are co-cultured with HIV-1 infected T cells to evaluate innate sensing by pDCs as assessed by release of type-I IFN.

HIV-1 innate sensing requires direct contact of infected CD4+ T cells with plasmacytoid dendritic cells (pDCs). In order to study this process, the ...

Generation and Identification of GM-CSF Derived Alveolar-like Macrophages and Dendritic Cells From Mouse Bone Marrow

Macrophages and dendritic cells (DCs) are innate immune cells found in tissues and lymphoid organs that play a key role in the defense against pathogens. However, they are difficult to isolate in sufficient numbers to study them in detail, therefore, in vitro models have been developed. In vitro cultures of bone marrow-derived macrophages and dendritic cells are well-established and valuable methods for immunological studies. Here, a method for culturing and identifying both DCs and macrophages from a single culture of primary mouse bone marrow cells using the cytokine granulocyte macrophage colony-stimulating factor (GM-CSF) is described. This protocol is based on the established procedure first developed by Lutz et al. in 1999 for bone marrow-derived DCs. The culture is heterogeneous, and MHCII and fluoresceinated hyaluronan (FL-HA) are used to distinguish macrophages from immature and mature DCs. These GM-CSF derived macrophages provide a convenient source of in vitro derived macrophages that closely resemble alveolar macrophages in both phenotype and function.

Bone marrow cells cultured with granulocyte macrophage colony stimulating factor (GM-CSF) generate a heterogeneous culture containing macrophages and dendritic cells (DCs). This method highlights using MHCII and hyaluronan (HA) binding to differentiate macrophages from the DCs in the GM-CSF culture. Macrophages in this culture have many similarities to alveolar macrophages.

Macrophages and dendritic cells (DCs) are innate immune cells found in tissues and lymphoid organs that play a key role in the defense against pathogens. ...

Fluorescence-activated Cell Sorting for Purification of Plasmacytoid Dendritic Cells from the Mouse Bone Marrow

Fluorescence-activated cell sorting (FACS) is a technique to purify specific cell populations based on phenotypes detected by flow cytometry. This method enables researchers to better understand the characteristics of a single cell population without the influence of other cells. Compared to other methods of cell enrichment, such as magnetic-activated cell sorting (MCS), FACS is more flexible and accurate for cell separation due to the ability of phenotype detection by flow cytometry. In addition, FACS is usually capable of separating multiple cell populations simultaneously, which improves the efficiency and diversity of experiments. Although FACS has some limitations, it has been broadly used to purify cells for functional studies in both in vitro and in vivo settings. Here we report a protocol using fluorescence-activated cell sorting to isolate a very rare population of immune cells, plasmacytoid dendritic cells (pDC), with high purity from the bone marrow of lupus-prone mice for in vitro functional studies of pDC.

We report a protocol using fluorescence-activated cell sorting to isolate plasmacytoid dendritic cells (pDC) with high purity from the bone marrow of lupus-prone mice for functional studies of pDC.

Fluorescence-activated cell sorting (FACS) is a technique to purify specific cell populations based on phenotypes detected by flow cytometry. This method ...

Generation of Human Monocyte-derived Dendritic Cells from Whole Blood

Dendritic cells (DCs) recognize foreign structures of different pathogens, such as viruses, bacteria, and fungi, via a variety of pattern recognition receptors (PRRs) expressed on their cell surface and thereby activate and regulate immunity. 
The major function of DCs is the induction of adaptive immunity in the lymph nodes by presenting antigens via MHC I and MHC II molecules to na&#239;ve T lymphocytes. Therefore, DCs have to migrate from the periphery to the lymph nodes after the recognition of pathogens at the sites of infection. For in vitro experiments or DC vaccination strategies, monocyte-derived DCs are routinely used. These cells show similarities in physiology, morphology, and function to conventional myeloid dendritic cells. They are generated by interleukin 4 (IL-4) and granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulation of monocytes isolated from healthy donors. Here, we demonstrate how monocytes are isolated and stimulated from anti-coagulated human blood after peripheral blood mononuclear cell (PBMC) enrichment by density gradient centrifugation. Human monocytes are differentiated into immature DCs and are ready for experimental procedures in a non-clinical setting after 5 days of incubation.

Here, we demonstrate how monocytes are isolated by magnetic bead separation from peripheral blood mononuclear cells after density gradient centrifugation of human anti-coagulated blood. Following incubation for 5 days, human monocytes are differentiated into immature dendritic cells and are ready for experimental procedures in a non-clinical setting.

Dendritic cells (DCs) recognize foreign structures of different pathogens, such as viruses, bacteria, and fungi, via a variety of pattern recognition ...

A Novel Feeder-free System for Mass Production of Murine Natural Killer Cells In Vitro

Natural killer (NK) cells belong to the innate immune system and are a first-line anti-cancer immune defense; however, they are suppressed in the tumor microenvironment and the underlying mechanism is still largely unknown. The lack of a consistent and reliable source of NK cells limits the research progress of NK cell immunity. Here, we report an in vitro system that can provide high quality and quantity of bone marrow-derived murine NK cells under a feeder-free condition. More importantly, we also demonstrate that siRNA-mediated gene silencing successfully inhibits the E4bp4-dependent NK cell maturation by using this system. Thus, this novel in vitro NK cell differentiating system is a biomaterial solution for immunity research.

A Novel Feeder-free System for Mass Production of Murine Natural Killer Cells In Vitro

Here, we present a protocol to mass-produce gene-silencing murine NK cells by using a feeder-free differentiation system for mechanistic study in vitro and in vivo.

Natural killer (NK) cells belong to the innate immune system and are a first-line anti-cancer immune defense; however, they are suppressed in the tumor ...

Generation of Large Numbers of Myeloid Progenitors and Dendritic Cell Precursors from Murine Bone Marrow Using a Novel Cell Sorting Strategy

Cultures of monocyte-derived dendritic cells (moDC) generated from mouse bone marrow using Granulocyte-Macrophage Colony Stimulating Factor (GM-CSF) have recently been recognized to be more heterogeneous than previously appreciated. These cultures routinely contain moDC as well monocyte-derived macrophages (moMac), and even some less developed cells such as monocytes. The goal of this protocol is to provide a consistent method for identification and separation of the many cell types present in these cultures as they develop, so that their specific functions may be further investigated. The sorting strategy presented here separates cells first into four populations based on expression of Ly6C and CD115, both of which are expressed transiently by cells as they develop in GM-CSF-driven culture. These four populations include Common myeloid progenitors or CMP (Ly6C-, CD115-), granulocyte/macrophage progenitors or GMP (Ly6C+, CD115-), monocytes (Ly6C+, CD115+), and monocyte-derived macrophages or moMac (Ly6C-, CD115+). CD11c is also added to the sorting strategy to distinguish two populations within the Ly6C-, CD115- population: CMP (CD11c-) and moDC (CD11c+). Finally, two populations may be further distinguished within the Ly6C-, CD115+ population based on the level of MHC class II expression. MoMacs express lower levels of MHC class II, while a monocyte-derived DC precursor (moDP) expresses higher MHC class II. This method allows for the reliable isolation of several developmentally distinct populations in numbers sufficient for a variety of functional and developmental analyses. We highlight one such functional readout, the differential responses of these cell types to stimulation with Pathogen-Associated Molecular Patterns (PAMPs).

Here we provide a method for identifying and isolating large numbers of GM-CSF driven myeloid cells using high speed cell sorting. Five distinct populations (Common myeloid progenitors, granulocyte/macrophage progenitors, monocytes, monocyte-derived macrophages, and monocyte-derived DCs) can be identified based on Ly6C and CD115 expression.

Cultures of monocyte-derived dendritic cells (moDC) generated from mouse bone marrow using Granulocyte-Macrophage Colony Stimulating Factor (GM-CSF) have ...