Thanks to Brad Lackford for assistance optimizing some of the techniques described in this manuscript.

1. Maintenance of Macrophage Cell Lines
<ol>
	<li>Grow RAW264.7 and J774A.1 cell lines in DMEM supplemented with 10% fetal bovine serum (FBS) at 37 &#186;C in the presence of 5% CO2. To help maintain sterility, add 1% penicillin/streptomycin (pen/strep) to the media (although this is not strictly necessary).</li>
	<li>Critical step: Ensure that the macrophages are growing in a healthy state for efficient transfection and siRNA-induced gene knockdown. Use cells between passages 3 and 10 after...

<ol>
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V., 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+novel+genes+that+mediate+innate+immunity+using+inbred+mice.">Identification of novel genes that mediate innate immunity using inbred mice.</a> Genetics. 183, 1535-1544 (2009).</li><li>Raschke, W. C., Baird, S., Ralph, P., Nakoinz, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+macrophage+cell+lines+transformed+by+Abelson+leukemia+virus.">Functional macrophage cell lines transformed by Abelson leukemia virus.</a> Cell. 15, 261-267 (1978).</li><li>Ralph, P., Moore, M. A., Nilsson, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lysozyme+synthesis+by+established+human+and+murine+histiocytic+lymphoma+cell+lines.">Lysozyme synthesis by established human and murine histiocytic lymphoma cell lines.</a> The Journal of experimental medicine. , 1528-1533 (1976).</li><li>Zumbansen, M., 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=First+siRNA+library+screening+in+hard-to-transfect+HUVEC+cells.">First siRNA library screening in hard-to-transfect HUVEC cells.</a> Journal of RNAi and gene silencing. 6, 354-360 (2010).</li><li>Lu, Y. C., Yeh, W. C., Ohashi, P. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=LPS/TLR4+signal+transduction+pathway.">LPS/TLR4 signal transduction pathway.</a> Cytokine. 42, 145-151 (2008).</li><li>Aliprantis, A. O., 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=Cell+activation+and+apoptosis+by+bacterial+lipoproteins+through+toll-like+receptor-2.">Cell activation and apoptosis by bacterial lipoproteins through toll-like receptor-2.</a> Science. 285, 736-739 (1999).</li><li>Alexopoulou, L., Holt, A. C., Medzhitov, R., Flavell, R. 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Numerous studies have been published in which individual genes have been targeted by siRNA in murine macrophages. While lipid-mediated transfection has been used to deliver siRNA to macrophage cell lines on an individual basis, these methods suffer from potential effects on viability, limited gene knockdown, and variability from gene to gene. To develop more robust assays that could be used to target genes in medium- or high-throughput fashion, we optimized techniques using the Amaxa nucleofector 96-well shuttle system, ...

In this protocol, we describe efficient methods to inhibit genes in mouse macrophage cell lines using siRNAs and monitor the effects of these treatments on the innate immune response. These procedures are performed in 96-well format, allowing for RNAi screens in medium- or high-throughput fashion.
In response to infection, humans mount an immediate innate immune response and a slower but more specific adaptive immune response. This rapid innate immune response involves the recruitment and activation of phagocytic innate immune cells including macrophages1. Classically activated macrophages are involved in acute inflammatory responses and produce antimicrobial proteins and compounds, cytokines and chemokines, and present antigens2,3. Alternatively activated macrophages play a role in regulating immunity, maintaining tolerance, tissue repair, and wound healing4-8. Because of their wide array of functions, macrophages can play a role in numerous diseases including atherosclerosis, arthritis, and cancer9. Thus, the study of macrophages has been a key area of research for some time in a wide variety of disease fields.
Despite their importance in the innate immune response, macrophages can be challenging cells to work with. In particular, it is difficult to obtain efficient transfection using lipid reagents in macrophages without associated toxicity10,11. Moreover, even when siRNA is efficiently delivered to macrophages, the robustness of RNAi-induced gene knockdown often can be fairly moderate and can vary from gene to gene.
To overcome these technical challenges, we have optimized transfection and knockdown techniques12-16 in two mouse macrophage cell lines, RAW264.717 and J774A.118. This approach uses the Amaxa Nucleofector 96-well Shuttle System for transfection; this system uses a combination of specialized reagents and electroporation to transfect cells in 96-well format19. Following transfection, we describe methods to maximize cell recovery and viability and to maximize subsequent siRNA-induced gene knockdown. To illustrate the utility of this approach, we describe a protocol for siRNA delivery to these macrophage cell lines, stimulate these cells with lipopolysaccharide (LPS), and monitor the innate immune response at the level of production of several pro-inflammatory cytokines. We provide sample data in which we target the Toll-like receptor (TLR) family, whose members sense LPS and other pathogen associated molecular patterns (PAMPs), to regulate innate immunity.

<table border="0" cellpadding="0" cellspacing="0" >
	<tbody>
		<tr >
			<td >Amaxa nucleofector 96-well shuttle system</td>
			<td>Lonza</td>
			<td>AAM-1001S</td>
		<td></td></tr>
		<tr >
			<td >Amaxa SF cell line 96-well nucleofector kit</td>
			<td>Lonza</td>
			<td>V4SC-2096</td>
		<td></td></tr>
		<tr >
			<td >RAW264.7 mouse macrophage cell line</td>
			<td>ATCC</td>
			<td>TIB-71</td>
		<td></td></tr>
		<tr >
			<td >J774A.1 mouse macrophage cell line</td>
			<td>ATCC</td>
			<td>TIB-67</td>
		<td></td></tr>
		<tr >
			<td >siGenome smartpool siRNA</td>
			<td>Dharmacon</td>
			<td>varies depending on gene</td>
		<td></td></tr>
		<tr >
			<td >Non-targeting control siRNA pool</td>
			<td>Dharmacon</td>
			<td>D-001206-13-20</td>
		<td></td></tr>
		<tr >
			<td >Block-iT fluorescent oligo for electrooration</td>
			<td>Invitrogen</td>
			<td>13750062</td>
		<td></td></tr>
		<tr >
			<td >Ultrapure E. coli O111:B4 LPS</td>
			<td>List Biological Laboratories</td>
			<td>421</td>
		<td></td></tr>
		<tr >
			<td >DMEM, high glucose</td>
			<td>Invitrogen</td>
			<td>11995-065</td>
		<td></td></tr>
		<tr >
			<td >RPM1-1640</td>
			<td>Invitrogen</td>
			<td>11875-093</td>
		<td></td></tr>
		<tr >
			<td >Penicillin-Streptomycin Solution (Pen/Strep)</td>
			<td>Fisher</td>
			<td>SV30010</td>
		<td></td></tr>
		<tr >
			<td >0.25% Trypsin-EDTA</td>
			<td>Invitrogen</td>
			<td>25200072</td>
		<td></td></tr>
		<tr >
			<td >96 well tissue culture plates</td>
			<td>Fisher</td>
			<td>07-200-89 </td>
		<td></td></tr>
		<tr >
			<td >96 well round bottom sterile plates (not coated)</td>
			<td>Fisher</td>
			<td>07-200-745</td>
		<td></td></tr>
		<tr >
			<td >Mouse IL-6 Duoset ELISA kit</td>
			<td>R&#38;D Biosystems</td>
			<td>DY406</td>
		<td></td></tr>
		<tr >
			<td >Mouse TNFa Duoset ELISA kit</td>
			<td>R&#38;D Biosystems</td>
			<td>DY410</td>
		<td></td></tr>
		<tr >
			<td >Fluorescein diacetate</td>
			<td>Sigma-Aldrich</td>
			<td>F7378</td>
		<td></td></tr>
		<tr >
			<td >RLT Bufer</td>
			<td>Qiagen</td>
			<td>79216</td>
		<td></td></tr>
		<tr >
			<td >Rneasy mini kit</td>
			<td>Qiagen</td>
			<td>74134</td>
		<td></td></tr>
		<tr >
			<td >Vybrant Phagocytosis Assay Kit</td>
			<td>Invitrogen</td>
			<td>V-6694</td>
		<td></td></tr>
	</tbody>
</table>

using rna-interference to investigate the innate immune response in mouse macrophages

Macrophages are key phagocytic innate immune cells. When macrophages encounter a pathogen, they produce antimicrobial proteins and compounds to kill the pathogen, produce various cytokines and chemokines to recruit and stimulate other immune cells, and present antigens to stimulate the adaptive immune response. Thus, being able to efficiently manipulate macrophages with techniques such as RNA-interference (RNAi) is critical to our ability to investigate this important innate immune cell. However, macrophages can be technically challenging to transfect and can exhibit inefficient RNAi-induced gene knockdown. In this protocol, we describe methods to efficiently transfect two mouse macrophage cell lines (RAW264.7 and J774A.1) with siRNA using the Amaxa Nucleofector 96-well Shuttle System and describe procedures to maximize the effect of siRNA on gene knockdown. Moreover, the described methods are adapted to work in 96-well format, allowing for medium and high-throughput studies. To demonstrate the utility of this approach, we describe experiments that utilize RNAi to inhibit genes that regulate lipopolysaccharide (LPS)-induced cytokine production.

To demonstrate the efficiency of transfection using this approach, we monitored uptake of FITC-labeled siRNA using a flow cytometer (Figure 1).
To illustrate the utility of our approach for monitoring the innate immune response, we transfected siRNAs targeting known innate immune regulatory genes into the RAW264.7 macrophage cell line, stimulated the cells with LPS, and then monitored production of the pro-inflammatory cytokines IL-6 and TNF&#945;. Different TLRs recognize dif...

Watch this Scientific Journal Video about Using RNA-interference to Investigate the Innate Immune Response in Mouse Macrophages at JoVE.com

Using RNA-interference to Investigate the Innate Immune Response in Mouse Macrophages

In this protocol, we describe methods to efficiently transfect murine macrophage cell lines with siRNAs using the Amaxa Nucleofector 96-well Shuttle System, stimulate the macrophages with lipopolysaccharide, and monitor the effects on inflammatory cytokine production.

Macrophages are key phagocytic innate immune cells.  When macrophages encounter a pathogen, they produce antimicrobial proteins and compounds to kill the ...

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Immunology and Infection

10.5K Views.  National Jewish Health and University of Colorado School of Medicine. In this protocol, we describe methods to efficiently transfect murine macrophage cell lines with siRNAs using the Amaxa Nucleofector 96-well Shuttle System, stimulate the macrophages with lipopolysaccharide, and monitor the effects on inflammatory cytokine production.