All microscopy was done at the W. M. Keck Microscopy Center with support of Nathaniel Peters and with support of NIH award S10OD016240. S.L.F. is supported by NIH K08AI119142 and R21AI130281. We thank Dr. Richard Flavell and Dr. Brad Cookson for caspase-1/11 deficient mice, and Dr. Brad Cookson for sharing laboratory facilities and equipment.

All animal procedures were approved and conducted under University of Washington Institutional Animal Care and Use Committee guidelines.
1. Harvest of Bone Marrow
<ol>
	<li>Aseptically remove the femur and tibia from a mouse and clean the bones using sterile instruments. Place the cleaned bones in Dulbecco Modified Eagle Medium (DMEM) + 5 mM HEPES + 0.2 mg/mL L-glutamine + 0.05 mM 2-mercaptoethanol + 50 mg/mL gentamicin sulfate + 10,000 U/mL penicillin/streptomycin + 10% fetal bovine serum (...

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	<li>Jorgensen, I., Miao, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pyroptotic+cell+death+defends+against+intracellular+pathogens.">Pyroptotic cell death defends against intracellular pathogens.</a> Immunol Rev. 265 (1), 130-142 (2015).</li><li>Guo, H., Callaway, J. B., Ting, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inflammasomes:+mechanism+of+action,+role+in+disease,+and+therapeutics.">Inflammasomes: mechanism of action, role in disease, and therapeutics.</a> Nat Med. 21 (7), 677-687 (2015).</li><li>Bergsbaken, T., Fink, S. L., Cookson, B. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pyroptosis:+host+cell+death+and+inflammation.">Pyroptosis: host cell death and inflammation.</a> Nat Rev Microbiol. 7 (2), 99-109 (2009).</li><li>Martinon, F., Burns, K., Tschopp, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+inflammasome:+a+molecular+platform+triggering+activation+of+inflammatory+caspases+and+processing+of+proIL-beta.">The inflammasome: a molecular platform triggering activation of inflammatory caspases and processing of proIL-beta.</a> Mol Cell. 10 (2), 417-426 (2002).</li><li>Fink, S. L., Cookson, B. 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S., Vakifahmetoglu-Norberg, H., Yuan, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Deubiquitination+of+NLRP3+by+BRCC3+critically+regulates+inflammasome+activity.">Deubiquitination of NLRP3 by BRCC3 critically regulates inflammasome activity.</a> Mol Cell. 49 (2), 331-338 (2013).</li><li>Song, 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=NLRP3+Phosphorylation+Is+an+Essential+Priming+Event+for+Inflammasome+Activation.">NLRP3 Phosphorylation Is an Essential Priming Event for Inflammasome Activation.</a> Mol Cell. 68 (1), 185-197 (2017).</li><li>Stutz, A., 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=NLRP3+inflammasome+assembly+is+regulated+by+phosphorylation+of+the+pyrin+domain.">NLRP3 inflammasome assembly is regulated by phosphorylation of the pyrin domain.</a> J Exp Med. 214 (6), 1725-1736 (2017).</li><li>Broz, P., Dixit, V. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inflammasomes:+mechanism+of+assembly,+regulation+and+signalling.">Inflammasomes: mechanism of assembly, regulation and signalling.</a> Nat Rev Immunol. 16 (7), 407-420 (2016).</li><li>Masumoto, 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=ASC,+a+novel+22-kDa+protein,+aggregates+during+apoptosis+of+human+promyelocytic+leukemia+HL-60+cells.">ASC, a novel 22-kDa protein, aggregates during apoptosis of human promyelocytic leukemia HL-60 cells.</a> J Biol Chem. 274 (48), 33835-33838 (1999).</li><li>Yamamoto, 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=ASC+is+essential+for+LPS-induced+activation+of+procaspase-1+independently+of+TLR-associated+signal+adaptor+molecules.">ASC is essential for LPS-induced activation of procaspase-1 independently of TLR-associated signal adaptor molecules.</a> Genes Cells. 9 (11), 1055-1067 (2004).</li><li>Miao, E. 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V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+death+and+cell+lysis+are+separable+events+during+pyroptosis.">Cell death and cell lysis are separable events during pyroptosis.</a> Cell Death Discov. , (2017).</li><li>Russo, H. 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=Active+Caspase-1+Induces+Plasma+Membrane+Pores+That+Precede+Pyroptotic+Lysis+and+Are+Blocked+by+Lanthanides.">Active Caspase-1 Induces Plasma Membrane Pores That Precede Pyroptotic Lysis and Are Blocked by Lanthanides.</a> J Immunol. 197 (4), 1353-1367 (2016).</li><li>Evavold, C. 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In this manuscript, we have presented two techniques to examine inflammasome activation and the consequence of caspase-1 activation following NLRP3 stimulation in murine bone marrow-derived macrophages. The first technique allows the researcher to determine the level of caspase-1 activation on a cellular basis using the fluorescent reporter FAM-YVAD-FMK. This reporter is highly specific for binding the caspase-1 family of enzymes, as seen by the absence of staining in caspase-1/11 deficient macrophages. Specificity was a...

Inflammasome-mediated inflammation is a critical component of the defense against pathogenic organisms1, but also underlies the etiology of many diseases2. The inflammatory response to a wide range of infections is triggered by cytosolic detection of pathogen associated molecular patterns (PAMPs) or damage associated molecular patterns (DAMPs). Pattern recognition receptors (PRR), including members of the NOD-like receptor (NLR) family, oligomerize upon the detection of these PAMPs and DAMPs. This triggers the formation of a multi-protein complex termed the inflammasome, which contains the PRR, the adaptor protein Apoptosis-associated speck-like protein containing a C-terminal caspase-recruitment domain (CARD) (ASC), and the pro-form of caspase-13,4. This complex allows proximity-induced auto-activation of caspase-1. Active caspase-1 then leads to a set of events that are characteristic of the inflammatory cell death pathway pyroptosis. These events include: the cleavage and release of the inflammatory cytokines IL-1&#946; and IL-18, lysosome exocytosis with release of lysosomal contents into the extracellular space, nuclear condensation, and gasdermin D cleavage. The released N-terminal domain of gasdermin D inserts into the plasma membrane, forming pores that cause plasma membrane rupture and release of inflammatory contents, in addition to taking away a protective niche for pathogen replication5,6,7.
Here, we focus on the well-studied NLRP3 inflammasome. The activation of the NLRP3 inflammasome occurs through a two-step process8. The first &#34;priming&#34; step occurs through the recognition by Toll-like receptors (TLR) of a microbial product. This is replicated in the laboratory setting by using LPS to stimulate TLR4. This stimulation upregulates NLRP3 and pro-IL-1&#946; through NF-kB signaling. Priming additionally licenses NLRP3 through non-transcriptional mechanisms by inducing its deubiquitination9,10 and phosphorylation or dephosphorylation of specific residues11,12.
The second signal for NLRP3 activation is thought to involve mitochondrial factors, reactive oxygen species, potassium efflux and calcium signaling, although a unifying mechanism for NLRP3 activation remains elusive8. Activated NLRP3 oligomerizes through interactions between its NACHT domains, and recruits ASC via binding of the pyrin (PYD) domains13. In each cell, these macromolecular complexes form a single microscopically visible focus. ASC was originally identified as a 22 KDa protein that forms a &#34;speck&#34; during the apoptosis of human leukemia cells, and named apoptosis-associated speck-like protein containing a CARD14. It was later determined that ASC recruits pro-caspase-1 through the interaction of the CARD of ASC with the CARD of pro-caspase-1, forming the inflammasome15.
Not all NLRs require the presence of ASC to induce caspase-1 activation. Unlike NLRP3, NLRC4 and NLRP1b have CARD domains and can directly recruit pro-caspase-1 via CARD-CARD interactions to induce caspase-1 activation. In the absence of ASC, active caspase-1 remains diffuse throughout the cytosol and does not form a single focus. This diffuse active caspase-1 is sufficient to induce pyroptotic cell death, but is unable to process pro-IL-1&#946;13,16.
In this manuscript, we will discuss two ways to assess inflammasome activation. The first uses the fluorescent activity probe, FAM-YVAD-FMK, which binds the caspase-1 family of proteases. This family includes caspase-1, but also mouse caspase-11 and human caspase-4 and caspase-5. By using macrophages from caspase-1/11 deficient mice in all experiments, the specificity of this probe will be addressed. This method can be combined with antibody labeling of inflammasome components, which we will also describe. Microscopic visualization allows for the identification of individual cells containing active caspase-1 and oligomerized ASC. Using this method, researchers will be able to determine where in the inflammasome formation cascade their manipulations of the host cell or the pathogenic organism under study have an effect. For example, one can distinguish whether a given intervention prevents the recruitment of ASC to the NLRP3 complex or targets the subsequent recruitment and activation of caspase-117. Examining outcomes of caspase-1 activation such as IL-1&#946; secretion would not be able to distinguish between these two possibilities. Also, the secretion of IL-1&#946; could be altered without altering the cells ability to activate caspase-1 and undergo pyroptotic cell death16.
The second method measures the release of lactate dehydrogenase (LDH) into the cell supernatant, which occurs during pyroptotic macrophage lysis following caspase-1 activation as described above. This second method is a population-based approach as the release of LDH in the entire well is measured. This simple approach allows for the rapid analysis (30 min of incubation time) of samples to determine if there is caspase-1-mediated cell death and can be performed in a 96-well plate format.
These methods are complementary, each with different advantages, and both are easily amenable to modifications. For example, macrophage treatment with targeted small molecular weight compounds prior to inflammasome stimulation can be used to investigate the role certain proteins may have on controlling inflammatory responses.

<table>
	<tbody>
		<tr>
			<td>E-MEM</td>
			<td>ATCC</td>
			<td>30-2003</td>
			<td>For growing L929 cells</td>
		</tr>
		<tr>
			<td>NCRC clone 929 (L929)&#160;</td>
			<td>ATCC</td>
			<td>CCL-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Fixation/Permeabilization Kit</td>
			<td>BD Biosciences</td>
			<td>554714</td>
			<td>Includes fixation and permeabilization solution, and wash buffer.&#160; Proprietary formulations. Contains 4.2% formaldehyde</td>
		</tr>
		<tr>
			<td>Glycine</td>
			<td>Biorad</td>
			<td>161-0718</td>
			<td></td>
		</tr>
		<tr>
			<td>Cytotox96 Nonradioactive cytotoxicity assay</td>
			<td>Fisher Scientific</td>
			<td>PR-G1780</td>
			<td>Includes Substrate Mix and Assay Buffer; Proprietary formulations. Stop solution is 1 M Acetic acid</td>
		</tr>
		<tr>
			<td>FAM-YVAD-FMK</td>
			<td>Immunocytochemistry Technologies</td>
			<td>98</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM, high glucose, no glutamine</td>
			<td>Invitrogen</td>
			<td>11960044</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM, high glucose, no glutamine, no phenol red</td>
			<td>Invitrogen</td>
			<td>31053028</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s PBS, no calcium, no magnesium</td>
			<td>Invitrogen</td>
			<td>14190144</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum, qualified, US origin</td>
			<td>Invitrogen</td>
			<td>26140079</td>
			<td>Heat inactivated at 55&#176;C for 50 min</td>
		</tr>
		<tr>
			<td>Gentamicin</td>
			<td>Invitrogen</td>
			<td>15750060</td>
			<td></td>
		</tr>
		<tr>
			<td>ProLong Gold Mounting Medium</td>
			<td>Invitrogen</td>
			<td>p36934</td>
			<td>Proprietary formulation. Curing mounting medium. Hardens to refractory index of 1.46</td>
		</tr>
		<tr>
			<td>goat anti-mouse ALEXA555</td>
			<td>Invitrogen</td>
			<td>A-21422</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES (Ultra Pure)</td>
			<td>Invitrogen</td>
			<td>11344041</td>
			<td></td>
		</tr>
		<tr>
			<td>L-Glutamine</td>
			<td>Invitrogen</td>
			<td>21051024</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin</td>
			<td>Invitrogen</td>
			<td>15140122</td>
			<td></td>
		</tr>
		<tr>
			<td>TO-PRO-3 Iodide</td>
			<td>Invitrogen</td>
			<td>T3605</td>
			<td>far-red fluorescent nucleic acid stain&#160;</td>
		</tr>
		<tr>
			<td>C57BL/6J mouse</td>
			<td>Jackson Laboratoy</td>
			<td>000664</td>
			<td></td>
		</tr>
		<tr>
			<td>caspase-1/11-/- mouse</td>
			<td>Jackson Laboratory</td>
			<td>016621</td>
			<td></td>
		</tr>
		<tr>
			<td>Leica SP8X Confocal Microscope</td>
			<td>Leica</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ultrapure LPS from Salmonella minnesota R595 (Re)</td>
			<td>List Biologicals</td>
			<td>434</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-ASC clone 2EI-7</td>
			<td>Millipore-Sigma</td>
			<td>04-417</td>
			<td></td>
		</tr>
		<tr>
			<td>beta-mercapto-ethanol</td>
			<td>Millipore-Sigma</td>
			<td>M6250-10ML</td>
			<td></td>
		</tr>
		<tr>
			<td>DMSO</td>
			<td>Millipore-Sigma</td>
			<td>D2650-5X10ML</td>
			<td></td>
		</tr>
		<tr>
			<td>EDTA</td>
			<td>Millipore-Sigma</td>
			<td>E5391</td>
			<td></td>
		</tr>
		<tr>
			<td>Spectramax M3 plate reader</td>
			<td>Molecular Devices</td>
			<td>5000414</td>
			<td></td>
		</tr>
	</tbody>
</table>

detection of inflammasome activation and pyroptotic cell death in murine bone marrow-derived macrophages

Inflammasomes are innate immune signaling platforms that are required for the successful control of many pathogenic organisms, but also promote inflammatory and autoinflammatory diseases. Inflammasomes are activated by cytosolic pattern recognition receptors, including members of the NOD-like receptor (NLR) family. These receptors oligomerize upon the detection of microbial or damage-associated stimuli. Subsequent recruitment of the adaptor protein ASC forms a microscopically visible inflammasome complex, which activates caspase-1 through proximity-induced auto-activation. Following the activation, caspase-1 cleaves pro-IL-1&#946; and pro-IL-18, leading to the activation and secretion of these pro-inflammatory cytokines. Caspase-1 also mediates the inflammatory form of cell death termed pyroptosis, which features the loss of membrane integrity and cell lysis. Caspase-1 cleaves gasdermin D, releasing the N-terminal fragment which forms plasma membrane pores, leading to osmotic lysis.
In vitro, the activation of caspase-1 can be determined by labeling bone marrow-derived macrophages with the caspase-1 activity probe FAM-YVAD-FMK and by labeling the cells with antibodies against the adaptor protein ASC. This technique allows the identification of inflammasome formation and caspase-1 activation in individual cells using fluorescence microscopy. Pyroptotic cell death can be detected by measuring the release of cytosolic lactate dehydrogenase into the medium. This procedure is simple, cost effective and performed in a 96-well plate format, allowing adaptation for screening. In this manuscript, we show that activation of the NLRP3 inflammasome by nigericin leads to the co-localization of the adaptor protein ASC and active caspase-1, leading to pyroptosis.

To detect caspase-1 activation following the exposure to nigericin, the cells were processed as described in the protocol section. We combined both FAM-YVAD-FMK and ASC antibody labeling in order to show that ASC and active caspase-1 co-localize following NLRP3-mediated inflammasome activation. Figure 1A shows that wild type macrophages exposed to 5 &#956;M nigericin have formation of an ASC focus in the perinuclear region. These foci also contain active casp...

Watch this Scientific Journal Video about Detection of Inflammasome Activation and Pyroptotic Cell Death in Murine Bone Marrow-derived Macrophages at JoVE.com

Detection of Inflammasome Activation and Pyroptotic Cell Death in Murine Bone Marrow-derived Macrophages

We describe the detection of NLRP3 inflammasome activation on cellular basis using fluorescence microscopy and staining for active caspase-1 and the adaptor, ASC. A lactate dehydrogenase release assay is presented to detect pyroptotic lysis on a population basis. These techniques can be adapted to study many aspects of inflammasome biology.

Inflammasomes are innate immune signaling platforms that are required for the successful control of many pathogenic organisms, but also promote ...

The overall goals of this protocol are to examine inflammasome activation at the single cell level via fluorescence microscopy and to measure lysis during pyroptosis by a lactate dehydrogenase, or LDH release assay. This method can help answer key questions in the inflammasome field, such as how is Caspase-1 activation regulated. The main advantage of these techniques is that they allow the user to examine multiple steps of the inflammasome activation and pyroptosis pathways.Demonstrating the procedure will be Andreas den Hartigh, a research scientist from my laboratory. Begin by replacing the medium from LPS-primed bone marrow derived macrophages seeded on glass coverslips with 290 microliters of DMEM 5 medium, supplemented with five micromolar nigericin and five millimolar glycine, per well. Return the 24-well plate to the cell culture incubator for 60 minutes at 37 degrees Celsius and 5%carbon dioxide, adding 10 microliters of 30X FAM-YVAD-FMK after the first 15 minutes.At the end of the incubation, wash the cells with one milliliter of cold PBS per well, three times for five minutes per wash and fix the cells with 250 microliters of 2%paraformaldehyde per well for 30 minutes on ice protected from light, labeling the cells with an appropriate fluorescence nuclear dye during the last five minutes. At the end of the incubation, wash the cells three times with cold PBS as just demonstrated and load each slide with seven microliters of anti-fade mounting medium. Place a coverslip onto each slide and allow the mounting medium to harden overnight before sealing the coverslips with nail polish.To image the cells by fluorescence confocal microscopy, place the untreated control slide onto the microscope stage and manually focus on the cells. Using the microscope look up table settings, adjust the offset until no positive probe staining is observed in the untreated cells. Next, using a nigericin treated sample, locate a field that contains cells that are both positive and negative for the probe staining and adjust the imaging plane of the probe channel to the plane that has the highest intensity of positive staining.Then adjust the gain until the foci are visible in the cells with condensed nuclei and obtain images of five randomly selected fields per slide at a 100X total magnification. For immunofluorochemical analysis of the nigericin treated cells, wash the prop-labeled cells as just demonstrated and incubate the cells in 250 microliters of fixation and permeabilization solution per well for 30 minutes on ice, protected from light. Wash the macrophages three more times with fresh wash buffer and label the cells with 250 microliters of primary antibody against a ptosis associated speck-like protein containing a C-terminal caspase-recruitment domain, or ASC, per well, for one hour on ice.Wash the cells at the end of the incubation and label the samples with 250 microliters of the appropriate fluorescence dye conjugated secondary antibody for another hour on ice, adding four microliters of an appropriate fluorescence nuclear staining dye during the last five minutes. After washing the cells three times in cold wash buffer, mount coverslips onto the slides with seven microliters of anti-fade mounting medium, as demonstrated, and image the macrophages by fluorescence confocal microscopy. To perform an LDH release assay, add 50 microliters of DMEM 5 medium supplemented with 10 micromolar nigericin to each experimental well and 50 microliters of DMEM 5 to the spontaneous and 100%lysis control wells for 60 minutes at 37 degrees Celsius and 5%carbon dioxide.After 30 minutes, add 10 microliters of 10X lysis buffer to the 100%lysis control wells and add 10 microliters of medium to the other wells. At the end of the incubation, centrifuge the plate and transfer 50 microliters of supernatant from each well to clear, flat-bottomed plate. Next, add 50 microliters of freshly thawed and prepared substrate to each well for a 30 minute incubation in the dark, checking the plate after 15 minutes to confirm that the signal will not exceed the detection limit of the plate reader.At the end of the incubation, add 50 microliters of stop solution to each well and measure the OD490 on an appropriate plate reader to allow calculation of the percentage of cell lysis per well. While type macrophages exposed to nigericin demonstrate the formation of an ASC focus in the perinuclear region that also contain active Caspase-1, indicating that these cells are undergoing pyroptosis. While macrophages from Caspase-111 deficient mice also generate an ASC focus, these cells do not have any active Caspase-1 associated with this focus, as indicated by the absence of FAM-YVAD-FMK staining.Nor are the nuclei of these cells condensed, indicating an absence of pyroptotic cell death. Further, a large percentage of wild type macrophages undergo cell death after nigericin exposure, as measured by LDH release analysis of their culture supernatants, while macrophages deficient in Caspase-1 do not release LDH into the supernatant, indicating that the cells are still intact. After watching this video, you should have a good understanding of how to visualize inflammasome formation by fluorescence microscopy and to determine the level of cell lysis by measuring LDH release.This procedure can be modified for the use of other inflammasome stimuli or interventions that alter inflammasome activation or pyroptosis.

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Research

JoVE Journal

Immunology and Infection

10.4K Views.  University of Washington. The overall goals of this protocol are to examine inflammasome activation at the single cell level via fluorescence microscopy and to measure lysis during pyroptosis by a lactate dehydrogenase, or LDH release assay. This method can help answer key questions in the inflammasome field, such as how is Caspase-1 activation regulated. The main advantage of these techniques is that they allow the user to examine multiple steps of the inflammasome activation and pyroptosis pathways.Demonstrat...

Video: Detection of Inflammasome Activation and Pyroptotic Cell Death in Murine Bone Marrow-derived Macrophages

Toxoplasma gondii Cyst Wall Formation in Activated Bone Marrow-derived Macrophages and Bradyzoite Conditions

Toxoplasma gondii is an obligate intracellular parasite that can invade any nucleated cell of warm-blooded animals. During infection, T. gondii disseminates as a fast replicating form called the tachyzoite. Tachyzoites convert into a slow-growing encysted form called the bradyzoite by a signaling process that is not well characterized. Within animals, bradyzoite cysts are found in the central nervous system and muscle tissue and represent the chronic stage of infection. Conversion to bradyzoites can be simulated in tissue culture by CO2 starvation, using medium with high a pH, or the addition of interferon gamma (IFN&gamma;). Bradyzoites are characterized by the presence of a cyst wall, to which the lectin Dolichos biflorus agglutinin (DBA) binds. Fluorescently labeled DBA is used to visualize the cyst wall in parasites grown in human foreskin fibroblasts (HFFs) that have been exposed to low CO2 and high pH medium. Similarly, parasites residing in murine bone marrow-derived macrophages (BMMs) display a cyst wall detectable by DBA after the BMMs are activated with IFN&gamma; and lipopolysaccharide (LPS). This protocol will demonstrate how to induce conversion of T. gondii to bradyzoites using a high pH growth medium with low CO2 and activation of BMMs. Host cells will be cultured on coverslips, infected with tachyzoites and either activated with addition of IFN&gamma; and LPS (BMMs) or exposed to a high pH growth medium (HFFs) for three days. Upon completion of infections, host cells will be fixed, permeabilized, and blocked. Cyst walls will be visualized using rhodamine DBA with fluorescence microscopy.

Toxoplasma gondii Cyst Wall Formation in Activated Bone Marrow-derived Macrophages and Bradyzoite Conditions

Toxoplasma gondii converts to a cyst form in response to environmental stresses, which can be mimicked in tissue culture models. This video demonstrates techniques to examine cyst wall formation by activating bone marrow-derived macrophages or changing growth medium pH in fibroblast cells.

Toxoplasma gondii is an obligate intracellular parasite that can invade any nucleated cell of warm-blooded animals. During infection, T. gondii ...

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 ...

Investigation of Macrophage Polarization Using Bone Marrow Derived Macrophages

The article describes a readily easy adaptive in vitro model to investigate macrophage polarization. In the presence of GM-CSF/M-CSF, hematopoietic stem/progenitor cells from the bone marrow are directed into monocytic differentiation, followed by M1 or M2 stimulation. The activation status can be tracked by changes in cell surface antigens, gene expression and cell signaling pathways.

The article describes a readily easy adaptive in vitro model to investigate macrophage polarization. In the presence of GM-CSF/M-CSF, hematopoietic stem/progenitor cells from the bone marrow are directed into monocytic differentiation, followed by M1 or M2 stimulation. The activation status can be tracked by changes in cell surface antigens, gene expression and cell signaling pathways.

The article describes a readily easy adaptive in vitro model to investigate macrophage polarization. In the presence of GM-CSF/M-CSF, hematopoietic ...

Bone Marrow-derived Macrophage Production

Macrophages are critical components of the innate and adaptive immune responses, and they are the first line of defense against foreign invaders because of their powerful microbicidal activities. Macrophages are widely distributed throughout the body and are present in the lymphoid organs, liver, lungs, gastrointestinal tract, central nervous system, bone, and skin. Because of their repartition, they participate in a wide range of physiological and pathological processes. Macrophages are highly versatile cells that are able to recognize microenvironmental alterations and to maintain tissue homeostasis. Numerous pathogens have evolved mechanisms to use macrophages as Trojan horses to survive, replicate in, and infect both humans and animals and to propagate throughout the body. The recent explosion of interest in evolutionary, genetic, and biochemical aspects of host-pathogen interactions has renewed scientific attention regarding macrophages. Here, we describe a procedure to isolate and cultivate macrophages from murine bone marrow that will provide large numbers of macrophages for studying host-pathogen interactions as well as other processes.

Macrophages have long been recognized as a critical component of the innate and adaptive immune responses. The recent explosion of knowledge pertaining to evolutionary, genetic, and biochemical aspects of the interaction between macrophages and microbes has renewed scientific attention to macrophages. This article describes a method to differentiate macrophages from mouse bone marrow.

Macrophages are critical components of the innate and adaptive immune responses, and they are the first line of defense against foreign invaders because ...

Isolation and Intravenous Injection of Murine Bone Marrow Derived Monocytes

As a subtype of leukocytes and progenitors of macrophages, monocytes are involved in many important processes of organisms and are often the subject of various fields in biomedical science. The method described below is a simple and effective way to isolate murine monocytes from heterogeneous bone marrow.
Bone marrow from the femur and tibia of Balb/c mice is harvested by flushing with phosphate buffered saline (PBS). Cell suspension is supplemented with macrophage-colony stimulating factor (M-CSF) and cultured on ultra-low attachment surfaces to avoid adhesion-triggered differentiation of monocytes. The properties and differentiation of monocytes are characterized at various intervals. Fluorescence activated cell sorting (FACS), with markers like CD11b, CD115, and F4/80, is used for phenotyping. At the end of cultivation, the suspension consists of 45%&#177; 12% monocytes. By removing adhesive macrophages, the purity can be raised up to 86%&#177; 6%. After the isolation, monocytes can be utilized in various ways, and one of the most effective and common methods for in vivo delivery is intravenous tail vein injection. 
This technique of isolation and application is important for mouse model studies, especially in the fields of inflammation or immunology. Monocytes can also be used therapeutically in mouse disease models.

Here we present a protocol that generates large amounts of murine monocytes from heterogeneous bone marrow for translational applications. In comparison to others, this new method helps reduce the number of sacrificed animals and lowers costs by avoiding expensive methods such as high gradient magnetic cell separation (MACS).

As a subtype of leukocytes and progenitors of macrophages, monocytes are involved in many important processes of organisms and are often the subject of ...

Metabolic Characterization of Polarized M1 and M2 Bone Marrow-derived Macrophages Using Real-time Extracellular Flux Analysis

Specific metabolic pathways are increasingly being recognized as critical hallmarks of macrophage subsets. While LPS-induced classically activated M1 or M(LPS) macrophages are pro-inflammatory, IL-4 induces alternative macrophage activation and these so-called M2 or M(IL-4) support resolution of inflammation and wound healing. Recent evidence shows the crucial role of metabolic reprogramming in the regulation of M1 and M2 macrophage polarization. 
In this manuscript, an extracellular flux analyzer is applied to assess the metabolic characteristics of naive, M1 and M2 polarized mouse bone marrow-derived macrophages. This instrument uses pH and oxygen sensors to measure the extracellular acidification rate (ECAR) and oxygen consumption rate (OCR), which can be related to glycolytic and mitochondrial oxidative metabolism. As such, both glycolysis and mitochondrial oxidative metabolism can be measured in real-time in one single assay.
Using this technique, we demonstrate here that inflammatory M1 macrophages display enhanced glycolytic metabolism and reduced mitochondrial activity. Conversely, anti-inflammatory M2 macrophages show high mitochondrial oxidative phosphorylation (OXPHOS) and are characterized by an enhanced spare respiratory capacity (SRC). 
The presented functional assay serves as a framework to investigate how particular cytokines, pharmacological compounds, gene knock outs or other interventions affect the macrophage&#8217;s metabolic phenotype and inflammatory status.

Metabolic reprogramming is a characteristic and prerequisite for M1 and M2 macrophage polarization. This manuscript describes an assay for the measurement of fundamental parameters of glycolysis and mitochondrial function in mouse bone marrow-derived macrophages. This tool can be applied to investigate how particular factors affect the macrophage&#8217;s metabolism and phenotype.

Specific metabolic pathways are increasingly being recognized as critical hallmarks of macrophage subsets. While LPS-induced classically activated M1 or ...

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 ...

An In Vivo Mouse Model to Measure Na&#239;ve CD4 T Cell Activation, Proliferation and Th1 Differentiation Induced by Bone Marrow-derived Dendritic Cells

Quantification of na&#239;ve CD4 T cell activation, proliferation, and differentiation to T helper 1 (Th1) cells is a useful way to assess the role played by T cells in an immune response. This protocol describes the in vitro differentiation of bone marrow (BM) progenitors to obtain granulocyte macrophage colony-stimulating factor (GM-CSF) derived-dendritic cells (DCs). The protocol also describes the adoptive transfer of ovalbumin peptide (OVAp)-loaded GM-CSF-derived DCs and na&#239;ve CD4 T cells from OTII transgenic mice in order to analyze the in vivo activation, proliferation, and Th1 differentiation of the transferred CD4 T cells. This protocol circumvents the limitation of purely in vivo methods imposed by the inability to specifically manipulate or select the studied cell population. Moreover, this protocol allows studies in an in vivo environment, thus avoiding alterations to functional factors that may occur in vitro and including the influence of cell types and other factors only found in intact organs. The protocol is a useful tool for generating changes in DCs and T cells that modify adaptive immune responses, potentially providing important results to understand the origin or development of numerous immune associated diseases.

An &lt;em&gt;In Vivo&lt;/em&gt; Mouse Model to Measure Na&amp;#239;ve CD4 T Cell Activation, Proliferation and Th1 Differentiation Induced by Bone Marrow-derived Dendritic Cells

Here, we present a protocol for the in vivo determination of na&#239;ve CD4 T cell (T cell) activation, proliferation, and Th1 differentiation induced by GM-CSF bone marrow (BM)-derived dendritic cells (DCs). In addition, this protocol describes BM and T-cell isolation, DC generation, and DC and T-cell adoptive transfer.

Quantification of na&#239;ve CD4 T cell activation, proliferation, and differentiation to T helper 1 (Th1) cells is a useful way to assess the role played ...

Isolation and In vitro Culture of Bone Marrow-Derived Macrophages for the Study of NO-Redox Biology

Macrophages are derived from hematopoietic progenitor cells throughout the body, are central to inflammatory processes, and participate in innate and adaptive immune responses. In vitro study of macrophages can be undertaken by ex vivo culture from the peritoneum or through differentiation of myeloid bone marrow progenitor cells to form bone marrow-derived macrophages (BMDMs). A common approach to macrophage differentiation from precursors involves the use of conditioned media from L929 cells (LCM). This media is easy to self-produce but suffers from batch variability, and its constituents are undefined. Similarly, Foetal Bovine Serum (FBS) is used to support growth but contains a vast mixture of undefined molecules that may vary between batches. These methods are not adequate for the study of nitric oxide biology and redox mechanisms as they both contain substantial amounts of small molecules that either interfere with redox mechanisms or supplement levels of cofactors, such as tetrahydrobiopterin (BH4), required for the production of NO from inducible nitric oxide synthase (iNOS). In this report, we present an optimized protocol allowing for control of the NO-redox environment by reducing the levels of exogenous biopterin while maintaining conditions suitable for cell growth and differentiation. Tight control of culture media composition helps ensure experimental reproducibility and facilitates accurate interpretation of results. In this protocol, BMDMs were obtained from a GTP cyclohydrolase (GCH)- deficient mouse model. Culture of BMDMs was performed with media containing either (i) conditioned LCM, or (ii) recombinant M-CSF and GM-CSF to produce minimal artifacts while obtaining BH4 and NO-deficient culture conditions - thus allowing for the reproducible study of NO-redox biology and immunometabolism in vitro.

Isolation and In vitro Culture of Bone Marrow-Derived Macrophages for the Study of NO-Redox Biology

This protocol has been established to culture tetrahydrobiopterin (BH4)- and inducible nitric oxide synthase (iNOS)-deficient primary murine macrophages to study NO-redox biology. The study focuses on reducing potential contamination of BH4 and other artifacts found in traditional isolation and culture methods which may confound experimental outcomes and interpretation of results.

Macrophages are derived from hematopoietic progenitor cells throughout the body, are central to inflammatory processes, and participate in innate and ...

Evaluation of Caspase Activation to Assess Innate Immune Cell Death

Innate immunity provides the critical first line of defense in response to pathogens and sterile insults. A key mechanistic component of this response is the initiation of innate immune programmed cell death (PCD) to eliminate infected or damaged cells and propagate immune responses. However, excess PCD is associated with inflammation and pathology. Therefore, understanding the activation and regulation of PCD is a central aspect of characterizing innate immune responses and identifying new therapeutic targets across the disease spectrum.
This protocol provides methods for characterizing innate immune PCD activation by monitoring caspases, a family of cysteine-dependent proteases that are often associated with diverse PCD pathways, including&#160;apoptosis,&#160;pyroptosis, necroptosis, and PANoptosis. Initial reports characterized caspase-2, caspase-8, caspase-9, and caspase-10 as initiator caspases and caspase-3, caspase-6, and caspase-7 as effector caspases in apoptosis, while later studies found the inflammatory caspases, caspase-1, caspase-4, caspase-5, and caspase-11, drive pyroptosis. It is now known that there is extensive crosstalk between the caspases and other innate immune and&#160;cell death molecules across the previously defined PCD pathways, identifying a key knowledge gap in the mechanistic understanding of innate immunity and PCD and&#160;leading to the characterization of PANoptosis. PANoptosis is a unique innate immune inflammatory PCD pathway regulated by PANoptosome complexes, which integrate components, including caspases,&#160;from other cell death pathways.
Here, methods for assessing the activation of caspases in response to various stimuli are provided. These methods allow for the characterization of PCD pathways both in vitro and in vivo, as activated caspases undergo proteolytic cleavage that can be visualized by western blotting using optimal antibodies and blotting conditions. A protocol and western blotting workflow have been established that allow for the assessment of the activation of multiple caspases from the same cellular population, providing a comprehensive characterization of the PCD processes. This method can be applied across research areas in development, homeostasis, infection, inflammation, and cancer to evaluate PCD pathways throughout cellular processes in health and disease.

This protocol describes a comprehensive method for assessing caspase activation (caspase-1, caspase-3, caspase-7, caspase-8, caspase-9, and caspase-11) in response to both in vitro and in vivo (in mice) models of infection, sterile insults, and cancer to determine the initiation of cell death pathways, such as pyroptosis, apoptosis, necroptosis, and PANoptosis.

Innate immunity provides the critical first line of defense in response to pathogens and sterile insults. A key mechanistic component of this response is ...