This work was supported by a grant from the&#160;Natural Sciences and Engineering Research Council of Canada (NSERC, grant no 298515-2011).&#160;AL is the recipient of a Ph.D. scholarship from the Natural Sciences and Engineering Research Council of Canada (NSERC),&#160;and MS was supported from a grant from the Canadian Institutes of Health Research (CIHR, grant no. MOP123246).

All procedures were performed in accordance with the Canadian Council on Animal Care guidelines after approval by the institutional Animal Care Committee of the Centre de recherche du Centre Hospitalier de l&#8217;Universit&#233; de Montr&#233;al (CRCHUM).
1. Isolation, Identification, and Culture of Murine Peritoneal Macrophages
<ol>
	<li>Prepare 3.8% brewer&#8217;s thioglycollate medium. To do so, suspend 38 g of thioglycollate medium in 1,000 ml of distilled water. Bring solution to boil to dissolve the medium completely. Sterilize by autoclaving at 121 &#176;C for 15 min. Store up to 3 months in the dark, at RT18. 
	&#8203;NOTE: Discard if turbidity develops which indicates a bacterial contamination. The solution can be kept for up to one year in the dark if kept sterile.</li>
	<li>Using 1 ml syringes attached to 23 G needles, inject 1 ml of 3.8% Brewer thioglycollate medium into the peritoneal cavity of each mouse and wait for 3 days. Use new syringe and needle for each mouse.</li>
	<li>Anesthetize mice by intraperitoneal injection of sodium pentobarbital (100 mg/kg) and euthanize mice by cervical dislocation. Confirm proper anesthetization by checking the respiratory rate. Usually rapid respirations indicate that the mouse is not deeply anaesthetized.</li>
	<li>Wash the abdomen of each mouse with 70% ethanol. Using a scissor, perform a lateral incision along the bottom midline of the peritoneum.</li>
	<li>Using a forceps, pull back the abdominal skin to expose the transparent peritoneal skin. Using 5 ml syringes attached to 20 G needles, inject 5 ml of cold DPBS into the peritoneal cavity of each mouse.</li>
	<li>Perform a gentle massage on the peritoneal cavity and then aspirate the fluid carefully without puncturing any organ. Remove the needle and dispense the peritoneal fluid into 50 ml conical centrifuge tubes.</li>
	<li>Centrifuge for 10 min at 400 x g in a refrigerated centrifuge. Cells must stay cold during the whole procedure. Discard supernatant and resuspend cell pellet in RPMI medium 1640.</li>
	<li>Using a hemocytometer, count cells&#160;and adjust to cell density to 1 x 106&#160;cells/ml.&#160;</li>
	<li>Characterize the phenotype of isolated cells by flow cytometry using 1 x 106 cells per mouse and antibodie against F4/80 (a surface antigen&#160;expressed on macrophages).</li>
</ol>
2. Cell Treatments
<ol>
	<li>Directly, after isolation, add 1 x 106&#160;cells into each well. Leave the murine peritoneal macrophages to adhere into the 6-well plates by culturing them for 1 to 2 hr at 37 &#176;C. Remove non-adherent cells by gently washing 3 times with warm PBS.</li>
	<li>Subsequently, culture cells in 900 &#181;l serum-free DMEM for 24 hr in the presence of the following TLR ligands: (Pam3CSK4-TLR1/2 (0.5 mg/ml); Poly(I:C)-TLR3 (10 mg/ml); LPS-TLR4 (100 ng/ml); Flagellin-TLR5 (100 ng/ml); FSL1-TLR6/2 (100 ng/ml); ssRNA40-TLR7 (1 &#181;g/ml); ODN1826-TLR9 (1 &#181;M). 
	NOTE: Prepare for each ligand a 10x stock solution. Add 100 &#181;l of the latter to each well, thus performing a 10-fold dilution.</li>
</ol>
3. RNA Isolation
<ol>
	<li>Remove all medium and lyse cells directly in the six-well plates by adding 1 ml TRIzol to each well and passing the cell lysate several times through a pipette. Incubate the homogenised samples for 5 to 10 min at RT, to allow the complete dissociation of nucleoprotein complexes.</li>
	<li>Transfer lysate into 1.5 ml RNase- and DNase-free microcentrifuge tubes. Add 0.2 ml chloroform per 1ml TRIzol. Shake tubes vigorously by hand for 15 sec and incubate them at RT for 5 to 10 min. Centrifuge at 12,000 x g for 15 min at 4 &#176;C. Observe the mixture separating into a lower red phase (phenol-chloroform), an interphase and a colorless upper aqueous phase. RNA remains exclusively in the aqueous phase.</li>
	<li>Transfer carefully the upper aqueous phase to a fresh tube without disturbing the interphase. Precipitate the RNA from it by mixing with 0.5 ml of isopropyl alcohol. Incubate samples at RT for 10 min and centrifuge at 12,000 x g for 10 min at 4 &#176;C. The RNA precipitates forming a white pellet on the side and bottom of the tube.</li>
	<li>Remove supernatant. Wash the RNA pellet once with 1 ml of 75% ethanol. Mix the samples by vortexing and centrifuge at 7,500 x g for 5 min at 4 &#176;C. Briefly dry the RNA (air dry for 10 min). Dissolve RNA in 0.1 ml DEPC (RNAse free water) and incubate for 10 min at 55 &#176;C.</li>
	<li>Quantify RNA using a spectrophotometer. To do so, dilute samples 100 times in DEPC water and read at wavelengths of 260 nm. The RNA concentration will then be: OD260 x 40 ng/ul x dilution factor.</li>
	<li>Equalize RNA concentrations and synthesize&#160;cDNA as per manufacturer&#8217;s instructions using RT-PCR System for First-Strand cDNA Synthesis Kit. As per manufacturer&#8217;s instructions, measure gene mRNA levels by real-time PCR (45 cycles) in a Real-Time DNA detection system. Normalize gene expression levels with two housekeeping gene for example &#946;-actin and GAPDH. 
	NOTE: Normalize RNA concentration to 500 &#181;g/ml and use 0.5 &#181;g for cDNA synthesis.</li>
</ol>

<ol>
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F., Ponka, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Non-heme+induction+of+heme+oxygenase-1+does+not+alter+cellular+iron+metabolism.">Non-heme induction of heme oxygenase-1 does not alter cellular iron metabolism.</a> J Biol Chem. 282 (14), 10480-10486 (2007).</li><li>Hershko, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Storage+iron+regulation.">Storage iron regulation.</a> Prog Hematol. 10, 105-148 (1977).</li><li>Collins, H. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Withholding+iron+as+a+cellular+defence+mechanism--friend+or+foe.">Withholding iron as a cellular defence mechanism--friend or foe.</a> Eur J Immunol. 38 (7), 1803-1806 (2008).</li><li>Noyes, W. D., Bothwell, T. H., Finch, C. 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M., Baviello, G., Vlassara, H., Mitsuhashi, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glycation+products+in+aged+thioglycollate+medium+enhance+the+elicitation+of+peritoneal+macrophages.">Glycation products in aged thioglycollate medium enhance the elicitation of peritoneal macrophages.</a> J Immunol Methods. 201 (2), 183-188 (1997).</li><li>Layoun, A., Santos, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bacterial+cell+wall+constituents+induce+hepcidin+expression+in+macrophages+through+MyD88+signaling.">Bacterial cell wall constituents induce hepcidin expression in macrophages through MyD88 signaling.</a> Inflammation. 35 (4), 1500-1506 (2012).</li><li>Oppenheim, J. J., Yang, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alarmins:+chemotactic+activators+of+immune+responses.">Alarmins: chemotactic activators of immune responses.</a> Curr Opin Immunol. 17 (4), 359-365 (2005).</li><li>Akira, S., Uematsu, S., Takeuchi, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pathogen+recognition+and+innate+immunity.">Pathogen recognition and innate immunity.</a> Cell. 124 (4), 783-801 (2006).</li><li>Lang, R., Patel, D., Morris, J. J., Rutschman, R. L., Murray, P. 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The authors have no competing financial interests.

Macrophages are crucial for survival and provide a tempting target to manipulate the host for immunological objectives. The discovery of TLRs and other recognition molecules have conducted the macrophages to the centre of immunological debate. Macrophages respond to a variety of stimuli, including cytokines, damage-associated molecular pattern molecules (DAMPs)20 and molecules associated with groups of pathogens (PAMPs)21. These different stimuli responses represent the course of macrophages activat...

The reticuloendothelial phagocytic system is composed of cells in various tissues and organs such as bone marrow, blood, liver and spleen. Macrophages are extensively distributed around the body, where they notably participate in innate and adaptive immune responses to control and clear infections. In addition to their role in host defense, macrophages also play an important role in wound healing and in maintaining tissue homeostasis1,2. Furthermore, macrophages are not only important to immune function but also actively participate in iron homeostasis3. In the body, approximately 80% of iron is present in hemoglobin within erythrocytes, which when senescent are phagocytosed by macrophages4. Daily, these macrophages recycle 25 mg of erythrocyte-derived iron and provide its transport into the plasma5. Moreover, during infection and inflammation, pro-inflammatory macrophages sequester serum iron to reduce iron availability to pathogens, at both the systemic and local levels6-8. As well, studies have shown that macrophages and mainly hepatocytes produce an antimicrobial peptide named hepcidin that is considered the master&#160;regulator of&#160;iron&#160;metabolism9,10. Hepcidin is mainly increased by inflammatory stimuli and is partially responsible for iron sequestration in macrophage upon chronic inflammation11-13.&#160;As hepcidin expression in macrophages is not very well understood, we studied the possible role of Toll-like receptors (TLRs) in this regulation. The TLRs&#160;are primarily found on&#160;macrophages and play a central role in&#160;their activation. In addition, LPS induced hepcidin expression in the liver is dependent on TLR413. Therefore, to execute our study, we used a method based on the isolation of murine peritoneal macrophages.
Macrophage cell lines are broadly used in macrophage studies; nonetheless extended culture can provoke gene loss and decreased immune functions in these cell lines. Thus, isolation of macrophages from peritoneal cavity is crucial.
The mouse peritoneal cavity presents an ideal site to harvest macrophages13-15. Isolated murine peritoneal macrophages are convenient for several studies regarding their immunological function. However, the number of macrophages in the peritoneum is insufficient for extensive studies and is estimated around 1 x 106 macrophages per mouse. Thus, to raise macrophage output, a sterile eliciting agent such as thioglycollate was injected into the peritoneal cavity preceding the cell harvest. After thioglycollate injection, the yield of macrophages per mouse was increased by 10-fold. Despite the increase in macrophages yield, Brewer&#8217;s thioglycollate medium acts as an irritant that induces an inflammatory response, resulting in the recruitment of macrophages, which may but not necessary affect gene expression. Hence, a control group consisting of non-treated macrophages must be included in each experiment. In our hands, hepcidin expression which is highly stimulated by inflammation was not detected in non-treated thioglycollate elicited peritoneal macrophages. Moreover, studies have shown that Brewer&#8217;s thioglycollate recruits numerous macrophages, but does not activate them16. On the other hand, Brewer&#8217;s thioglycollate elicited macrophages showed an increase in lysosomal enzyme but a decrease in&#160;killing ingested microorganisms17. However, the phagocytic capacity was not affected when compared with non-elicited macrophages16.
Once cultured in dishes, the peritoneal macrophages become adherent, therefore allowing their separation from other type of cells isolated from the peritoneal cavity. Subsequently, the isolated macrophages were challenged with different TLRs agonists. Finally, mRNA was extracted&#160;from the cultured&#160;cells and gene expression was analysed using quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR).

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>C57BL/6 mice</td>
			<td>Charles River Laboratories, Inc. (Wilmington, MA, USA)</td>
			<td>475</td>
			<td></td>
		</tr>
		<tr>
			<td>Thioglycollate</td>
			<td>Sigma-Aldrich, (St. Louis, MO)</td>
			<td>19032-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>70% ethanol</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>10% sodium pentobarbital (Used for mice anesthesia (80 mg/kg, i.p.))</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#8217;s phosphate-buffered saline (DPBS), placed on ice and will serve to harvest macrophages</td>
			<td>WISENT INC Canada (QC)</td>
			<td>311-425-CL</td>
			<td></td>
		</tr>
		<tr>
			<td>RPMI medium 1640 (Supplement with penicillin, streptomycin, L-glutamine, and 10 % fetal calf serum).</td>
			<td>WISENT INC Canada (QC)</td>
			<td>350-000-CL</td>
			<td></td>
		</tr>
		<tr>
			<td>1 and 5 ml syringes</td>
			<td>BD USA (NJ)</td>
			<td>309659</td>
			<td></td>
		</tr>
		<tr>
			<td>Six-well plates</td>
			<td>Corning Incorporated (NY, USA)</td>
			<td>MCT-150-C</td>
			<td></td>
		</tr>
		<tr>
			<td>Bacterial lipoprotein Pam3CSK4 (0.5 mg/ml)</td>
			<td>InvivoGen (San Diego, USA)</td>
			<td>TLRL-pm25</td>
			<td></td>
		</tr>
		<tr>
			<td>Polyionosine&#8211;polycytidylic acid (Poly(I:C)) (10 mg/ml)</td>
			<td>InvivoGen (San Diego, USA)</td>
			<td>TLRL-PIC</td>
			<td></td>
		</tr>
		<tr>
			<td>LPS from Escherichia coli 055:B5 (100 ng/ml)</td>
			<td>InvivoGen (San Diego, USA)</td>
			<td>L2880</td>
			<td></td>
		</tr>
		<tr>
			<td>Purified flagellin from Salmonella typhimurium (100 ng/ml)</td>
			<td>InvivoGen (San Diego, USA)</td>
			<td>TLR-FLIC-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Lipoprotein synthetic FSL1 (100 ng/ml)</td>
			<td>InvivoGen (San Diego, USA)</td>
			<td>TLR-FSL</td>
			<td></td>
		</tr>
		<tr>
			<td>ssRNA derived from the HIV-1 long terminal repeat ssRNA40 (1 &#956;g/ml)</td>
			<td>InvivoGen (San Diego, USA)</td>
			<td>TLR-LRNA-40</td>
			<td></td>
		</tr>
		<tr>
			<td>Type B CpG oligonucleotide ODN1826 (1 &#956;M)</td>
			<td>InvivoGen (San Diego, USA)</td>
			<td>11B16-MM</td>
			<td></td>
		</tr>
		<tr>
			<td>TRIZOL</td>
			<td>Invitrogen, (Burlington, ON, Canada)</td>
			<td>15596-026</td>
			<td></td>
		</tr>
		<tr>
			<td>20g and 23g needles</td>
			<td>BD USA (NJ)</td>
			<td>305175</td>
			<td></td>
		</tr>
		<tr>
			<td>Scissor</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Forceps</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>50 ml conical tubes placed on ice</td>
			<td>Sarstedt (Newton, MA, USA)</td>
			<td>62.547.205</td>
			<td></td>
		</tr>
		<tr>
			<td>Red Blood Cells Lysis Buffer</td>
			<td>Sigma-Aldrich, (St. Louis, MO)</td>
			<td>R7757-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Refrigerated centrifuge</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Hemocytometer</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>F4/80 antibody</td>
			<td>BIO-RAD ( CA, USA)</td>
			<td>MCA497APC</td>
			<td></td>
		</tr>
		<tr>
			<td>CD16/CD32 antibodies</td>
			<td>Pharmingen, {Mississauga, ON, CA)</td>
			<td>553141</td>
			<td></td>
		</tr>
		<tr>
			<td>Flow Cytometer</td>
			<td>Coulter Epics Elite counter, Coulter, (Hialeah, FL,USA)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Six-well plates</td>
			<td>Corning Incorporated (NY, USA)</td>
			<td>MCT-150-C</td>
			<td></td>
		</tr>
		<tr>
			<td>Bacterial lipoprotein Pam3CSK4 (0.5 mg/ml)</td>
			<td>InvivoGen (San Diego, USA)</td>
			<td>TLRL-pm25</td>
			<td></td>
		</tr>
		<tr>
			<td>Polyionosine&#8211;polycytidylic acid (Poly(I:C)) (10 mg/ml)</td>
			<td>InvivoGen (San Diego, USA)</td>
			<td>TLRL-PIC</td>
			<td></td>
		</tr>
		<tr>
			<td>LPS from Escherichia coli 055:B5 (100 ng/ml)</td>
			<td>InvivoGen (San Diego, USA)</td>
			<td>L2880</td>
			<td></td>
		</tr>
		<tr>
			<td>Purified flagellin from Salmonella typhimurium (100 ng/ml)</td>
			<td>InvivoGen (San Diego, USA)</td>
			<td>TLR-FLIC-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Lipoprotein synthetic FSL1 (100 ng/ml)</td>
			<td>InvivoGen (San Diego, USA)</td>
			<td>TLR-FSL</td>
			<td></td>
		</tr>
		<tr>
			<td>ssRNA derived from the HIV-1 long terminal repeat ssRNA40 (1 &#956;g/ml)</td>
			<td>InvivoGen (San Diego, USA)</td>
			<td>TLR-LRNA-40</td>
			<td></td>
		</tr>
		<tr>
			<td>Type B CpG oligonucleotide ODN1826 (1 &#956;M)</td>
			<td>InvivoGen (San Diego, USA)</td>
			<td>11B16-MM</td>
			<td></td>
		</tr>
		<tr>
			<td>TRIZOL</td>
			<td>Invitrogen, (Burlington, ON, Canada)</td>
			<td>15596-026</td>
			<td></td>
		</tr>
		<tr>
			<td>1.5 ml Eppendorf tubes</td>
			<td>Axygen Scietific (CA,USA)</td>
			<td>3516</td>
			<td></td>
		</tr>
		<tr>
			<td>Chloroform</td>
			<td>Fisher Scientific (ON, Canada)</td>
			<td>UN1888</td>
			<td></td>
		</tr>
		<tr>
			<td>Isopropyl alcohol</td>
			<td>JT Baker (PA, USA)</td>
			<td>70566</td>
			<td></td>
		</tr>
		<tr>
			<td>75% ethanol (in DEPC treated water)</td>
			<td>Commercial Alchohols (QC, Canada)</td>
			<td>17394</td>
			<td></td>
		</tr>
		<tr>
			<td>0.01% diethyl pyrocarbonate (DEPC) treated water (let stand overnight and autoclave)</td>
			<td>Sigma-Aldrich, (St. Louis, MO)</td>
			<td>216.542.8</td>
			<td></td>
		</tr>
		<tr>
			<td>Omniscript RT-PCR system</td>
			<td>Qiagen, (Mississauga, ON, Canada)</td>
			<td>205113</td>
			<td></td>
		</tr>
		<tr>
			<td>Rotor Gene 3000</td>
			<td>Montreal Biotech, (Kirkland, QC, Canada)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>QuantiTect SYBR Green I PCR kits</td>
			<td>Qiagen, (Mississauga, ON, Canada)</td>
			<td>204141</td>
			<td></td>
		</tr>
	</tbody>
</table>

isolation of murine peritoneal macrophages to carry out gene expression analysis upon toll-like receptors stimulation

During infection and inflammation, circulating monocytes leave the bloodstream and migrate into tissues, where they differentiate into macrophages. Macrophages express surface Toll-like receptors (TLRs), which recognize molecular patterns conserved through evolution in a wide range of microorganisms. TLRs play a central role in macrophage activation which is usually associated with gene expression alteration. Macrophages are critical in many diseases and have emerged as attractive targets for therapy. In the following protocol, we describe a procedure to isolate murine peritoneal macrophages using Brewer&#8217;s thioglycollate medium. The latter will boost monocyte migration into the peritoneum, accordingly this will raise macrophage yield by 10-fold. Several studies have been carried out using bone marrow, spleen or peritoneal derived macrophages. However, peritoneal macrophages were shown to be more mature upon isolation and are more stable in their functionality and phenotype. Thus, macrophages isolated from murine peritoneal cavity present an important cell population that can serve in different immunological and metabolic studies. Once isolated, macrophages were stimulated with different TLR ligands and consequently&#160;gene expression was evaluated.

We first characterized the isolated murine peritoneal macrophages by flow cytometry. To do so, we used (F4/80) antibodies that specifically recognize markers only expressed by macrophages. This characterization is required to determine the percentage of isolated macrophage and to distinguish them among cells obtained during the isolation process. As shown in (Figure 1), the percentage of cells expressing the antigen F4/80 was consistently found to be above 95%. Next, to study&#160;gene expression in macr...

Watch this Scientific Journal Video about Isolation of Murine Peritoneal Macrophages to Carry Out Gene Expression Analysis Upon Toll-like Receptors Stimulation at JoVE.com

Isolation of Murine Peritoneal Macrophages to Carry Out Gene Expression Analysis Upon Toll-like Receptors Stimulation

We describe here a simple protocol to isolate murine peritoneal macrophages. This procedure is followed by RNA extraction to carry out gene expression analysis upon Toll-like receptors stimulation.

During infection and inflammation, circulating monocytes leave the bloodstream and migrate into tissues, where they differentiate into macrophages. ...

isolation-murine-peritoneal-macrophages-to-carry-out-gene-expression

Research

JoVE Journal

Immunology and Infection

36.0K Views.  Institut du cancer de Montréal. We describe here a simple protocol to isolate murine peritoneal macrophages. This procedure is followed by RNA extraction to carry out gene expression analysis upon Toll-like receptors stimulation.

Video: Isolation of Murine Peritoneal Macrophages to Carry Out Gene Expression Analysis Upon Toll-like Receptors Stimulation

Isolation of Mouse Peritoneal Cavity Cells

The peritoneal cavity is a membrane-bound and fluid-filled abdominal cavity of mammals, which contains the liver, spleen, most of the gastro-intestinal tract and other viscera. It harbors a number of immune cells including macrophages, B cells and T cells. The presence of a high number of na&iuml;ve macrophages in the peritoneal cavity makes it a preferred site for the collection of na&iuml;ve tissue resident macrophages (1). The peritoneal cavity is also important to the study of B cells because of the presence of a unique peritoneal cavity-resident B cell subset known as B1 cells in addition to conventional B2 cells. B1 cells are subdivided into B1a and B1b cells, which can be distinguished by the surface expression of CD11b and CD5. B1 cells are an important source of natural IgM providing early protection from a variety of pathogens (2-4). These cells are autoreactive in nature (5), but how they are controlled to prevent autoimmunity is still not understood completely. On the contrary, CD5+ B1a cells possess some regulatory properties by virtue of their IL-10 producing capacity (6). Therefore, peritoneal cavity B1 cells are an interesting cell population to study because of their diverse function and many unaddressed questions associated with their development and regulation. The isolation of peritoneal cavity resident immune cells is tricky because of the lack of a defined structure inside the peritoneal cavity. Our protocol will describe a procedure for obtaining viable immune cells from the peritoneal cavity of mice, which then can be used for phenotypic analysis by flow cytometry and for different biochemical and immunological assays.

The peritoneal cavity in mammals contains different immune cell populations crucial for innate immune responses. An efficient isolation method is required for biochemical and functional analyses of these cells. Here we provide a comprehensive method for the isolation of peritoneal cavity cells in the mouse.

The peritoneal cavity is a membrane-bound and fluid-filled abdominal cavity of mammals, which contains the liver, spleen, most of the gastro-intestinal ...

Detection of  Neu1 Sialidase Activity in Regulating TOLL-like Receptor Activation

Mammalian Toll-like receptors (TLRs) are a family of receptors that recognize pathogen-associated molecular patterns. Not only are TLRs crucial sensors of microbial (e.g., viruses, bacteria and parasite) infections, they also play an important role in the pathophysiology of infectious diseases, inflammatory diseases, and possibly in autoimmune diseases. Thus, the intensity and duration of TLR responses against infectious diseases must be tightly controlled. It follows that understanding the structural integrity of sensor receptors, their ligand interactions and signaling components is essential for subsequent immunological protection. It would also provide important opportunities for disease modification through sensor manipulation. Although the signaling pathways of TLR sensors are well characterized, the parameters controlling interactions between the sensors and their ligands still remain poorly defined. We have recently identified a novel mechanism of TLR activation by its natural ligand, which has not been previously observed 1,2. It suggests that ligand-induced TLR activation is tightly controlled by Neu1 sialidase activation. We have also reported that Neu1 tightly regulates neurotrophin receptors like TrkA and TrkB 3, which involve Neu1 and matrix metalloproteinase-9 (MMP-9) cross-talk in complex with the receptors 4. The sialidase assay has been initially use to find a novel ligand, thymoquinone, in the activation of Neu4 sialidase on the cell surface of macrophages, dendritic cells and fibroblast cells via GPCR G&alpha;i proteins and MMP-9 5. For TLR receptors, our data indicate that Neu1 sialidase is already in complex with TLR-2, -3 and -4 receptors, and is induced upon ligand binding to either receptor. Activated Neu1 sialidase hydrolyzes sialyl &alpha;-2,3-linked &beta;-galactosyl residues distant from ligand binding to remove steric hinderance to TLR-4 dimerization, MyD88/TLR4 complex recruitment, NFkB activation and pro-inflammatory cell responses. In a collaborative report, Neu1 sialidase has been shown to regulate phagocytosis in macrophage cells 6. Taken together, the sialidase assay has provided us with powerful insights to the molecular mechanisms of ligand-induced receptor activation. Although the precise relationship between Neu1 sialidase and the activation of TLR, Trk receptors has yet to be fully elucidated, it would represent a new or pioneering approach to cell regulation pathways.

The sialidase assay is a simple technical approach that will elucidate novel molecular mechanism(s) of TLR sensors of microbial infections and involvement in inflammatory diseases at the receptor level on the cell surface of live macrophages.

Mammalian Toll-like receptors (TLRs) are a family of receptors that recognize pathogen-associated molecular patterns. Not only are TLRs crucial sensors of ...

Quantitative Imaging of Lineage-specific Toll-like Receptor-mediated Signaling in Monocytes and Dendritic Cells from Small Samples of Human Blood

Individual variations in immune status determine responses to infection and contribute to disease severity and outcome. Aging is associated with an increased susceptibility to viral and bacterial infections and decreased responsiveness to vaccines with a well-documented decline in humoral as well as cell-mediated immune responses1,2. We have recently assessed the effects of aging on Toll-like receptors (TLRs), key components of the innate immune system that detect microbial infection and trigger antimicrobial host defense responses3. In a large cohort of healthy human donors, we showed that peripheral blood monocytes from the elderly have decreased expression and function of certain TLRs4 and similar reduced TLR levels and signaling responses in dendritic cells (DCs), antigen-presenting cells that are pivotal in the linkage between innate and adaptive immunity5. We have shown dysregulation of TLR3 in macrophages and lower production of IFN by DCs from elderly donors in response to infection with West Nile virus6,7. 
Paramount to our understanding of immunosenescence and to therapeutic intervention is a detailed understanding of specific cell types responding and the mechanism(s) of signal transduction. Traditional studies of immune responses through imaging of primary cells and surveying cell markers by FACS or immunoblot have advanced our understanding significantly, however, these studies are generally limited technically by the small sample volume available from patients and the inability to conduct complex laboratory techniques on multiple human samples. ImageStream combines quantitative flow cytometry with simultaneous high-resolution digital imaging and thus facilitates investigation in multiple cell populations contemporaneously for an efficient capture of patient susceptibility. Here we demonstrate the use of ImageStream in DCs to assess TLR7/8 activation-mediated increases in phosphorylation and nuclear translocation of a key transcription factor, NF-&kappa;B, which initiates transcription of numerous genes that are critical for immune responses8. Using this technology, we have also recently demonstrated a previously unrecognized alteration of TLR5 signaling and the NF-&kappa;B pathway in monocytes from older donors that may contribute to altered immune responsiveness in aging9.

We describe use of ImageStream technology (<a href="http://www.amnis.com/" target="_blank">www.amnis.com</a>), which combines quantitative flow cytometry with simultaneous high-resolution digital imaging, to quantify cellular mechanisms of primary immune cells from well-defined patient cohorts. Our studies provide a blueprint for translational investigations to quantify lineage specific cellular responses in small samples from subject cohorts.

Individual variations in immune status determine responses to infection and contribute to disease severity and outcome.  Aging is associated with an ...

Isolation, Processing and Analysis of Murine Gingival Cells

We have developed a technique to precisely isolate and process murine gingival tissue for flow cytometry and molecular studies. The gingiva is a unique and important tissue to study immune mechanisms because it is involved in host immune response against oral biofilm that might cause periodontal diseases. Furthermore, the close proximity of the gingiva to alveolar bone tissue enables also studying bone remodeling under inflammatory conditions. Our method yields large amount of immune cells that allows analysis of even rare cell populations such as Langerhans cells and T regulatory cells as we demonstrated previously 1. Employing mice to study local immune responses involved in alveolar bone loss during periodontal diseases is advantageous because of the availability of various immunological and experimental tools. Nevertheless, due to their small size and the relatively inconvenient access to the murine gingiva, many studies avoided examination of this critical tissue. The method described in this work could facilitate gingival analysis, which hopefully will increase our understating on the oral immune system and its role during periodontal diseases.

This study describes an efficient technique to isolate and process gingival tissues from the mouse oral cavity in order to produce a single-cell culture. The resulting cells can be further used for flow cytometry analysis and molecular studies.

We have developed a technique to precisely isolate and process murine gingival tissue for flow cytometry and molecular studies. The gingiva is a unique ...

Use of Shigella flexneri to Study Autophagy-Cytoskeleton Interactions

Shigella flexneri is an intracellular pathogen that can escape from phagosomes to reach the cytosol, and polymerize the host actin cytoskeleton to promote its motility and dissemination. New work has shown that proteins involved in actin-based motility are also linked to autophagy, an intracellular degradation process crucial for cell autonomous immunity. Strikingly, host cells may prevent actin-based motility of S. flexneri by compartmentalizing bacteria inside &#8216;septin cages&#8217; and targeting them to autophagy. These observations indicate that a more complete understanding of septins, a family of filamentous GTP-binding proteins, will provide new insights into the process of autophagy. This report describes protocols to monitor autophagy-cytoskeleton interactions caused by S. flexneri in vitro using tissue culture cells and in vivo using zebrafish larvae. These protocols enable investigation of intracellular mechanisms that control bacterial dissemination at the molecular, cellular, and whole organism level.

Use of Shigella flexneri to Study Autophagy-Cytoskeleton Interactions

To counteract pathogen dissemination, host cells reorganize their cytoskeleton to compartmentalize bacteria and induce autophagy. Using Shigella infection of tissue culture cells, host and pathogen determinants underlying this process are identified and characterized. Using zebrafish models of Shigella infection, the role of discovered molecules and mechanisms are investigated in vivo.

Shigella flexneri is an intracellular pathogen that can escape from phagosomes to reach the cytosol, and polymerize the host actin cytoskeleton to promote ...

Legionella pneumophila Outer Membrane Vesicles: Isolation and Analysis of Their Pro-inflammatory Potential on Macrophages

Bacteria are able to secrete a variety of molecules via various secretory systems. Besides the secretion of molecules into the extracellular space or directly into another cell, Gram-negative bacteria can also form outer membrane vesicles (OMVs). These membrane vesicles can deliver their cargo over long distances, and the cargo is protected from degradation by proteases and nucleases. 
Legionella pneumophila (L. pneumophila) is an intracellular, Gram-negative pathogen that causes a severe form of pneumonia. In humans, it infects alveolar macrophages, where it blocks lysosomal degradation and forms a specialized replication vacuole. Moreover, L. pneumophila produces OMVs under various growth conditions. To understand the role of OMVs in the infection process of human macrophages, we set up a protocol to purify bacterial membrane vesicles from liquid culture. The method is based on differential ultracentrifugation. The enriched OMVs were subsequently analyzed with regard to their protein and lipopolysaccharide (LPS) amount and were then used for the treatment of a human monocytic cell line or murine bone marrow-derived macrophages. The pro-inflammatory responses of those cells were analyzed by enzyme-linked immunosorbent assay. Furthermore, alterations in a subsequent infection were analyzed. To this end, the bacterial replication of L. pneumophila in macrophages was studied by colony-forming unit assays. 
Here, we describe a detailed protocol for the purification of L. pneumophila OMVs from liquid culture by ultracentrifugation and for the downstream analysis of their pro-inflammatory potential on macrophages.

Legionella pneumophila Outer Membrane Vesicles: Isolation and Analysis of Their Pro-inflammatory Potential on Macrophages

Here, we describe the purification of Legionella pneumophila (L. pneumophila) outer membrane vesicles (OMVs) from liquid cultures. These purified vesicles are then used for the treatment of macrophages to analyze their pro-inflammatory potential.

Bacteria are able to secrete a variety of molecules via various secretory systems. Besides the secretion of molecules into the extracellular space or ...

Isolation of Salmonella typhimurium-containing Phagosomes from Macrophages

Salmonella typhimurium is a facultative intracellular bacterium that causes gastroenteritis in humans. After invasion of the lamina propria, S. typhimurium bacteria are quickly detected and phagocytized by macrophages, and contained in vesicles known as phagosomes in order to be degraded. Isolation of S. typhimurium-containing phagosomes have been widely used to study how S. typhimurium infection alters the process of phagosome maturation to prevent bacterial degradation. Classically, the isolation of bacteria-containing phagosomes has been performed by sucrose gradient centrifugation. However, this process is time-consuming, and requires specialized equipment and a certain degree of dexterity. Described here is a simple and quick method for the isolation of S. typhimurium-containing phagosomes from macrophages by coating the bacteria with biotin-streptavidin-conjugated magnetic beads. Phagosomes obtained by this method can be suspended in any buffer of choice, allowing the utilization of isolated phagosomes for a broad range of assays, such as protein, metabolite, and lipid analysis. In summary, this method for the isolation of S. typhimurium-containing phagosomes is specific, efficient, rapid, requires minimum equipment, and is more versatile than the classical method of isolation by sucrose gradient-ultracentrifugation.

Isolation of Salmonella typhimurium-containing Phagosomes from Macrophages

We describe here a simple and quick method for the isolation of Salmonella typhimurium-containing phagosomes from macrophages by coating the bacteria with biotin and streptavidin.

Salmonella typhimurium is a facultative intracellular bacterium that causes gastroenteritis in humans. After invasion of the lamina propria, S. ...

Using Phylogenetic Analysis to Investigate Eukaryotic Gene Origin

Phylogenetic analysis uses nucleotide or amino acid sequences or other parameters, such as domain sequences and three-dimensional structure, to construct a tree to show the evolutionary relationship among different taxa (classification units) at the molecular level. Phylogenetic analysis can also be used to investigate domain relationships within an individual taxon, particularly for organisms that have undergone substantial change in morphology and physiology, but for which researchers lack fossil evidence due to the organisms&#39; long evolutionary history or scarcity of fossilization.
In this text, a detailed protocol is described for using the phylogenetic method, including amino acid sequence alignment using Clustal Omega, and subsequent phylogenetic tree construction using both Maximum Likelihood (ML) of Molecular Evolutionary Genetics Analysis (MEGA) and Bayesian Inference via MrBayes. To investigate the origin of eukaryotic Sugars Will Eventually be Exported Transporters (SWEET) genes, 228 SWEETs including 35 SWEET proteins from unicellular eukaryotes and 57 SemiSWEET proteins from prokaryotes were analyzed. Interestingly, SemiSWEETs were found in prokaryotes, but SWEETs were found in eukaryotes. Two phylogenetic trees constructed using theoretically distinct methods have consistently&#160;suggested that the first eukaryotic SWEET gene might stem from the fusion of a bacterial SemiSWEET gene and an archaeal SemiSWEET gene.&#160;It is worth noting that one should be cautious to draw a conclusion based only on phylogenetic analysis, although it is useful to explain the underlying relationship between different taxa, which is difficult or even impossible to discern through experimental means.

A method of constructing a phylogenetic tree based on sequence homology of SWEETs from eukaryotes and SemiSWEETs from prokaryotes is described. Phylogenetic analysis is a useful tool for explaining the evolutionary relatedness between homologous proteins or genes from different organism groups.

Phylogenetic analysis uses nucleotide or amino acid sequences or other parameters, such as domain sequences and three-dimensional structure, to construct ...

Assessment of Antibody-based Drugs Effects on Murine Bone Marrow and Peritoneal Macrophage Activation

Macrophages are phagocytic innate immune cells, which initiate immune responses to pathogens and contribute to healing and tissue restitution. Macrophages are equally important in turning off inflammatory responses. We have shown that macrophages stimulated with intravenous immunoglobulin (IVIg) can produce high amounts of the anti-inflammatory cytokine, interleukin 10 (IL-10), and low levels of pro-inflammatory cytokines in response to bacterial lipopolysaccharides (LPS). IVIg is a polyvalent antibody, primarily immunoglobulin Gs (IgGs), pooled from the plasma of more than 1,000 blood donors. It is used to supplement antibodies in patients with immune deficiencies or to suppress immune responses in patients with autoimmune or inflammatory conditions. Infliximab, a therapeutic anti-tumor necrosis factor alpha (TNF&#945;) antibody, has also been shown to activate macrophages to produce IL-10 in response to inflammatory stimuli. IVIg and other antibody-based biologics can be tested to determine their effects on macrophage activation. This paper describes methods for derivation, stimulation, and assessment of murine bone marrow macrophages activated by antibodies in vitro and murine peritoneal macrophages activated with antibodies in vivo. Finally, we demonstrate the use of western blotting to determine the contribution of specific cell signaling pathways to anti-inflammatory macrophage activity. These protocols can be used with genetically modified mice, to determine the effect of a specific protein(s) on anti-inflammatory macrophage activation. These techniques can also be used to assess whether specific biologics may act by changing macrophages to an IL-10-producing anti-inflammatory activation state that reduces inflammatory responses in vivo. This can provide information on the role of macrophage activation in the efficacy of biologics during disease models in mice, and provide insight into a potential new mechanism of action in people. Conversely, this may caution against the use of specific antibody-based biologics to treat infectious disease, particularly if macrophages play an important role in host defense against that infection.

Antibody-based drugs have revolutionized treatment for inflammatory diseases. In addition to having direct effects on specific targets, antibodies can activate macrophages to become anti-inflammatory. This protocol describes how anti-inflammatory macrophage activation can be assessed in vitro, using mouse bone marrow macrophages, and in vivo, using peritoneal macrophages.

Macrophages are phagocytic innate immune cells, which initiate immune responses to pathogens and contribute to healing and tissue restitution. Macrophages ...

Isolation and In Vitro Culture of Murine and Human Alveolar Macrophages

Alveolar macrophages are terminally differentiated, lung-resident macrophages of prenatal origin. Alveolar macrophages are unique in their long life and their important role in lung development and function, as well as their lung-localized responses to infection and inflammation. To date, no unified method for identification, isolation, and handling of alveolar macrophages from humans and mice exists. Such a method is needed for studies on these important innate immune cells in various experimental settings. The method described here, which can be easily adopted by any laboratory, is a simplified approach to harvesting alveolar macrophages from bronchoalveolar lavage fluid or from lung tissue and maintaining them in vitro. Because alveolar macrophages primarily occur as adherent cells in the alveoli, the focus of this method is on dislodging them prior to harvest and identification. The lung is a highly vascularized organ, and various cell types of myeloid and lymphoid origin inhabit, interact, and are influenced by the lung microenvironment. By using the set of surface markers described here, researchers can easily and unambiguously distinguish alveolar macrophages from other leukocytes, and purify them for downstream applications. The culture method developed herein supports both human and mouse alveolar macrophages for in vitro growth, and is compatible with cellular and molecular studies.

Isolation and In Vitro Culture of Murine and Human Alveolar Macrophages

This communication describes methodologies for isolation and culture of alveolar macrophages from humans and murine models for experimental purposes.

Alveolar macrophages are terminally differentiated, lung-resident macrophages of prenatal origin. Alveolar macrophages are unique in their long life and ...