The authors would like to thank Nancy Mora for her technical assistance.
This work was funded by research grants 48573-M and 168098 from Consejo Nacional de Ciencia y Tecnologia, Mexico, and by grants IN212308 and IN205311-2 from Direccion General de Asuntos del Personal Academico, Universidad Nacional Autonoma de Mexico, Mexico.

1. Isolation of Neutrophils (PMN) from Human Blood
<ol>
	<li>Use about 20 ml human blood with heparin (10 U/ml) as anticoagulant. Blood was collected from adult healthy volunteers by venopuncture. All experiments were done under approval of the Bioethics Committee at the Instituto de Investigaciones Biom&eacute;dicas - UNAM.</li>
	<li>Put 2 ml of 6% dextran T500 in PBS into a 15 ml conical centrifuge tube and add 10 ml of blood. Mix by inverting the tube two or three times and let it sit for 45 min to allow for erythrocyte sedimentation.</li>
	<li>In a fresh 15 ml conical centrifuge tube put 5 ml Ficoll-Paque.</li>
	<li>Take the leukocyte-rich plasma that formed above sedimented erythrocytes, and carefully pipette it on top of the Ficoll-Paque forming a second layer. Make sure there are two phases.</li>
	<li>Centrifuge at 516 x g for 20 min at 4 &deg;C. After centrifugation, at the interphase of plasma and Ficoll-Paque there is a layer of mononuclear cells. Neutrophils are at the bottom of the tube.</li>
	<li>Eliminate the supernatant, break the cell pellet by tapping the tube against a rack, and resuspend the cells by adding 10 ml of cold (4 &deg;C) PBS. Note: Resuspending the cells by pipetting up and down is not recommended since this is too damaging to the cells.</li>
	<li>Transfer the cell suspension to a 50 ml conical centrifuge tube and centrifuge at 290 x g for 5 min at 4 &deg;C.</li>
	<li>Break the cell pellet as before and add 10 ml of cold (4 &deg;C) hypotonic solution (0.2% NaCl, 1% BSA, 20 mM Hepes, pH = 7.4) to lyse erythrocytes. Mix by swirling the tube gently by hand for exactly one minute.</li>
	<li>Add 10 ml of cold (4 &deg;C) hypertonic solution (1.6% NaCl, 1% BSA, 20 mM HEPES, pH = 7.4), mix and count the cells using a hemocytometer (usually &gt;95% are PMN). 
	Note: Keep the tube with the cell suspension on ice while counting the cells.</li>
	<li>Centrifuge as before and resuspend PMN at 107 cell/ml in cold (4 &deg;C) PBS. Keep on ice. 
	Note: Neutrophils remain viable and functional at 4 &deg;C for about 6 to 8 hr.</li>
</ol>
2. Activating PMN
<ol>
	<li>Put 100 &mu;l of PMN suspension (1 x 107cell/ml) into a 1.5 ml Eppendorf tube. 
	Note: Sample tubes should be done at least in duplicates. Usual negative controls should include first antibody only, and secondary antibody only.</li>
	<li>Add the corresponding anti-integrin or anti-Fc receptor monoclonal antibody (mAb) at 10 &mu;g/ml and incubate on ice for 15 min.</li>
	<li>Wash PMN by adding 1 ml of cold (4 &deg;C) PBS, centrifuging at 1,743 x g (4,500 rpm) in a microcentrifuge, and aspirating the supernatant.</li>
	<li>Break the cell pellet by tapping the bottom of the tube against a rack, add 1 ml cold PBS, and wash two more times as in previous step. 
	Note: These washes remove unbound antibody.</li>
	<li>Resuspend PMN in same (initial) volume of warm (37 &deg;C) PBS containing 60 &mu;g/ml of F(ab')2 goat anti-mouse IgG. 
	Note: The secondary anti-mouse IgG antibody will bind to the first anti-receptor antibody and will cause crosslinking of the receptor.</li>
	<li>Incubate at 37 &deg;C for 1 to 20 min, depending on the nuclear factor of interest. For NF-&kappa;B usually 15 min, and for Elk-1 usually 5 min. 
	Note: Incubating the cells at 37 &deg;C induces receptor crosslinking, which cannot take place at 4 &deg;C.</li>
	<li>Add 1 ml cold PBS and centrifuge 3 min at 1,743 x g in microcentrifuge.</li>
	<li>Remove supernatant</li>
	<li>Freeze PMN immediately in dry-ice/ethanol bath and keep them there for 10 min.</li>
</ol>
3. Isolation and Fixation of Nuclei
<ol>
	<li>Resuspend frozen PMN pellet in 100 &mu;l cold (4 &deg;C) hypotonic buffer (10 mM HEPES, 10 mM KCl, 1.5 mM MgCl2, and 1 mM freshly-added DL-dithiothreitol [DTT]; pH = 7.9). It is recommended to take the tubes out of the dry-ice/ethanol bath one by one, and to wipe clean the bottom of the tube before adding the hypotonic buffer.</li>
	<li>Place on ice, and check for nuclei integrity by staining an aliquot of the nuclei suspension with trypan blue. Nuclei look round and blue. Intact PMN do not get stained, and cell debris appears as blue particles of irregular shape. 
	Note: If nuclei suspension contains many intact cells or debris, it is better to discard the preparation and repeat the procedure with another sample.</li>
	<li>Centrifuge nuclei at 775 x g (3,000 rpm) in microcentrifuge for 10 min inside a cold room. At this point nuclei are very fragile and extra care should be taken in keeping the samples cold and not centrifuging at excessive forces.</li>
	<li>Remove supernatant by very careful pipetting.</li>
	<li>Add 100 &mu;l of cold 4% paraformaldehyde in PBS to fix nuclei. 
	Note: The pellet is very loose and adding the buffer is enough to resuspend the nuclei. Pipetting up and down should be avoided.</li>
	<li>Incubate on ice for 20 min.</li>
	<li>Immunolabel nuclei for flow cytometry or keep them for up to 24 hr at 4 &deg;C.</li>
</ol>
4. Nuclei Immunolabeling for Flow Cytometry Analysis
<ol>
	<li>Centrifuge nuclei at 1,743 x g (4,500 rpm) in microcentrifuge for 1 min, and remove supernatant by very gentle pipetting.</li>
	<li>Add 100 &mu;l of cold (4 &deg;C) 0.1% Triton X-100, 4% paraformaldehyde in PBS to permeabilize nuclei. Incubate in ice for 10 min.</li>
	<li>Centrifuge permeabilized nuclei at 1,743 x g in microcentrifuge and carefully remove the supernatant. At this point nuclei pellets do not attach well at the bottom of the tube. It is recommended to centrifuge again if the pellet gets loose.</li>
	<li>Resuspend nuclei in 500 &mu;l of cold 4% fetal bovine serum (FBS) in PBS to block nonspecific binding sites, and incubate on ice for 20 min. Centrifuge nuclei at 1,743 x g for 3 min in microcentrifuge and carefully remove the supernatant.</li>
	<li>Resuspend nuclei in 100 &mu;l of cold PBS containing 4% FBS and 2.5 &mu;g/ml of the mAb against the nuclear factor of interest. Incubate on ice for 20 min. 
	Note: Usual negative controls should include anti-nuclear factor antibody only, and FITC-labeled secondary antibody only.</li>
	<li>Wash twice with 500 &mu;l of cold PBS with 4% FBS and centrifuging at 1743 x g for 3 min.</li>
	<li>Remove the supernatant very carefully, resuspend nuclei in 100 &mu;l of cold PBS containing 4% FBS and 10 &mu;g/ml of the corresponding FITC-labeled secondary antibody, and incubate on ice for 20 min.</li>
	<li>Wash nuclei twice with 500 &mu;l of cold PBS with 4% FBS as in previous step.</li>
	<li>Resuspend nuclei in 400 &mu;l of cold 4% paraformaldehyde in PBS. 
	Note: Nuclei are placed in paraformaldehyde to allow the sample to be stored for several days without contamination problems that can occur in the presence of serum.</li>
	<li>Analyze immediately by flow cytometry or store in the dark at 4 &deg;C for up to three days.</li>
</ol>
5. Flow Cytometry Analysis
<ol>
	<li>Analyze immunolabeled nuclei in a flow cytometer such a FACScan (Becton Dickinson; Franklin Lakes, NJ) or similar apparatus.</li>
	<li>Adjust acquisition settings to: FSC at log-scale at 10-1, SSC at log-scale at 196, and gate nuclei in a dot-plot.</li>
	<li>Acquire ten thousand nuclei per sample.</li>
	<li>Analyze fluorescence of FITC-stained nuclei through the FL-1 channel (506 nm) set at log-scale at 400.</li>
</ol>

<ol>
	<li>Sendo, F., 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=Regulation+of+neutrophil+apoptosis:+its+biological+significance+in+inflammation+and+the+immune+response.">Regulation of neutrophil apoptosis: its biological significance in inflammation and the immune response.</a> Human Cell. 9, 215-222 (1996).</li><li>Borregaard, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neutrophils,+from+marrow+to+microbes.">Neutrophils, from marrow to microbes.</a> Immunity. 33, 657-670 (2010).</li><li>Naussef, W. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+human+neutrophils+kill+and+degrade+microbes.+An+integrated+view.">How human neutrophils kill and degrade microbes. An integrated view.</a> Immunol. Rev. 219, 88-102 (2007).</li><li>Scapini, P., 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=The+neutrophil+as+a+cellular+source+of+chemokines.">The neutrophil as a cellular source of chemokines.</a> Immunol. Rev. 177, 195-203 (2000).</li><li>Hamilton, T., 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+type-+and+stimulus-specific+mechanisms+for+post-transcriptional+control+of+neutrophil+chemokine+gene+expression.">Cell type- and stimulus-specific mechanisms for post-transcriptional control of neutrophil chemokine gene expression.</a> J. Leukoc. Biol. 91, 377-383 (2012).</li><li>Simon, H. U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neutrophil+apoptosis+pathways+and+their+modifications+in+inflammation.">Neutrophil apoptosis pathways and their modifications in inflammation.</a> Immunol. Rev. 193, 101-110 (2003).</li><li>Akgul, C., Moulding, D. A., Edwards, S. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+control+of+neutrophil+apoptosis.">Molecular control of neutrophil apoptosis.</a> FEBS Lett. 487, 318-322 (2001).</li><li>Witko-Sarsat, V., Pederzoli-Ribeil, M., Hirsch, E., Sozzani, S., Cassatella, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulating+neutrophil+apoptosis:+new+players+enter+the+game.">Regulating neutrophil apoptosis: new players enter the game.</a> Trends Immunol. 32, 117-124 (2011).</li><li>Green, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Death+and+NF-&#954;B+in+T+cell+activation:+life+at+the+edge.">Death and NF-&#954;B in T cell activation: life at the edge.</a> Mol. Cell. 11, 551-552 (2003).</li><li>Papa, S., Zazzeroni, F., Pham, C. G., Bubici, C., Franzoso, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Linking+JNK+signaling+to+NF-&#954;B:+a+key+to+survival.">Linking JNK signaling to NF-&#954;B: a key to survival.</a> J. Cell Sci. 117, 5197-5208 (2004).</li><li>Valente, P., 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=TNF+increases+camptothecin-induced+apoptosis+by+inhibition+of+NF-&#954;B.">TNF increases camptothecin-induced apoptosis by inhibition of NF-&#954;B.</a> Eur. J. Cancer. 39, 1468-1477 (2003).</li><li>Choi, 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=Inhibition+of+NF-&#954;B+by+a+TAT-NEMO-binding+domain+peptide+accelerates+constitutive+apoptosis+and+abrogates+LPS-delayed+neutrophil+apoptosis.">Inhibition of NF-&#954;B by a TAT-NEMO-binding domain peptide accelerates constitutive apoptosis and abrogates LPS-delayed neutrophil apoptosis.</a> Blood. 102, 2259-2267 (2003).</li><li>Wang, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inhibition+of+neutrophil+apoptosis+by+type+1+IFN+depends+on+cross-talk+between+phosphoinositol+3-kinase,+protein+kinase+C-d,+and+NF-&#954;B+signaling+pathways.">Inhibition of neutrophil apoptosis by type 1 IFN depends on cross-talk between phosphoinositol 3-kinase, protein kinase C-d, and NF-&#954;B signaling pathways.</a> J. Immunol. 171, 1035-1041 (2003).</li><li>Schnoor, 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=Efficient+non-viral+transfection+of+THP-1+cells.">Efficient non-viral transfection of THP-1 cells.</a> J. Immunol. Meth. 344, 109-115 (2009).</li><li>Garcia-Garcia, E., Rosales, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nuclear+factor+activation+by+Fc&#947;R+in+human+peripheral+blood+neutrophils+detected+by+a+novel+flow+cytometry-based+method.">Nuclear factor activation by Fc&#947;R in human peripheral blood neutrophils detected by a novel flow cytometry-based method.</a> J. Immunol. Meth. 320, 104-118 (2007).</li><li>Garcia-Garcia, E., Nieto-Castaneda, G., Ruiz-Saldana, M., Mora, N., Rosales, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fc&#947;RIIA+and+Fc&#947;RIIIB+mediate+nuclear+factor+activation+through+separate+signaling+pathways+in+human+neuthophils.">Fc&#947;RIIA and Fc&#947;RIIIB mediate nuclear factor activation through separate signaling pathways in human neuthophils.</a> J. Immunol. 182, 4547-4556 (2009).</li></ol>

The authors declare that they have no competing financial interests.

The purification method described here allows the isolation of unstimulated neutrophils (PMN) with purity greater than 95% (assessed by microscopic observation), in a short time. Sometimes neutrophils can be contaminated by erythrocytes if the latter are not lysed completely. This does not usually affect the technique, since erythrocytes and PMN can easily be distinguished as distinct cell populations by flow cytometry. Isolated PMN can then be stimulated by crosslinking particular receptors with specific monoclon...

Neutrophils are the most abundant leukocytes in peripheral blood 1. During inflammation and infection neutrophils are the first cells to appear at the affected site where they act as the first line of defense 2. Neutrophils possess several antimicrobial mechanisms 3 including phagocytosis, production of reactive oxygen species, release of lytic enzymes by degranulation, and production of proinflammatory cytokines 4,5. Neutrophils are short-lived cells that get rapidly activated through signaling from various cell surface receptors. Although neutrophils have been considered terminal cells due to their short life and because they undergo apoptosis unless activated during the inflammatory process 6, it is now clear that they can also modify their phenotype by changing the level of transcription of particular genes. The production of cytokines 5 and the inhibition of apoptosis 7,8 are two important activation-dependent cell functions regulated at the level of transcription in neutrophils. Nuclear factor &kappa;B (NF-&kappa;B) participates in the transcriptional control of cytokine production 4 and in the regulation of cell survival and apoptosis 9-11 in various cell types.
The signaling pathways that lead to nuclear factor activation are usually studied by reporter gene assays or by electrophoretic mobility shift assays (EMSA). However, because neutrophils are short-lived cells, the study of transcriptionally regulated responses in these cells cannot be performed with reporter gene assays, since there are no efficient techniques for neutrophil transfection. EMSA assays have been used in neutrophils to explore nuclear factor activation 12,13; however, this methodology is complicated and expensive because it involves the use of radioactive material. Nucleofection is another technique that has been used successfully to transfect monocytes 14. Thus, at least in theory, nuclear factor activation could be detected in neutrophils by transfection (despite low efficiency). However, this technique would be more expensive, time-consuming and probably less quantitative. Microscopic analysis of immunostained cells could also be used to detect nuclear factors in the nucleus. Indeed, we have detected NF-&kappa;B translocation into the nucleus this way 15. Unfortunately, this technique is also time-consuming, less quantitative, and subject to the observer's bias.
Here, we present a simple and efficient method that allows detection and quantification of nuclear factors in isolated and immunolabeled nuclei by flow cytometry. We describe techniques to isolate neutrophils from human peripheral blood, stimulate these cells via integrins or Fc receptors with anti-receptor antibodies, isolate and immunolabel nuclei, and analyze nuclei by flow cytometry (Figure 1). The method has been successfully used to detect NF-&kappa;B 15 and Elk-1 16 nuclear factors in neutrophil nuclei. The sensitivity of this method allows detection of small changes in nuclear factor levels in the nucleus. This method can also be used to analyze the level of transcription factors in nuclei from other cell types.

<table border="1">
<tbody>
 <tr>
 <td></td>
 <td></td>
 <td></td>
 <td>REAGENTS</td>
 </tr>
 <tr>
 <td >Heparin </td>
 <td >PiSA (Mexico)</td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td >Dextran T500</td>
 <td >Pharmacosmos A/S (Holbaek, Denmark) </td>
 <td>T1-Dextran T500</td>
 <td></td>
 </tr>
 <tr>
 <td >Ficoll-Paque</td>
 <td >Pharmacia</td>
 <td>17-0320-01 </td>
 <td></td>
 </tr>
 <tr>
 <td >Sodium chloride </td>
 <td >Sigma</td>
 <td>S7653 </td>
 <td></td>
 </tr>
 <tr>
 <td >Sodium phosphate monobasic</td>
 <td >Sigma</td>
 <td>S9638</td>
 <td></td>
 </tr>
 <tr>
 <td >Sodium phosphate dibasic</td>
 <td >Sigma</td>
 <td>S9390</td>
 <td></td>
 </tr>
 <tr>
 <td >Bovine serum albumin (BSA)</td>
 <td >Sigma</td>
 <td>A2153</td>
 <td>Cohn Fraction V</td>
 </tr>
 <tr>
 <td >HEPES</td>
 <td >Sigma</td>
 <td>H3375 </td>
 <td></td>
 </tr>
 <tr>
 <td >Potassium chloride</td>
 <td >Sigma</td>
 <td>P9541 </td>
 <td></td>
 </tr>
 <tr>
 <td >Magnesium chloride anhydrous </td>
 <td >Sigma</td>
 <td>M8266 </td>
 <td></td>
 </tr>
 <tr>
 <td >DL-dithiothreitol (DTT) </td>
 <td >Sigma</td>
 <td>D9163</td>
 <td></td>
 </tr>
 <tr>
 <td >Trypan Blue (0.4 % solution)</td>
 <td >Sigma</td>
 <td>T8154</td>
 <td></td>
 </tr>
 <tr>
 <td >Paraformaldehyde</td>
 <td >Sigma</td>
 <td>P6148 </td>
 <td></td>
 </tr>
 <tr>
 <td >Triton X-100 </td>
 <td >Sigma</td>
 <td>X100</td>
 <td></td>
 </tr>
 <tr>
 <td >Fetal bovine serum (FBS)</td>
 <td >GIBCO</td>
 <td>10437-028</td>
 <td></td>
 </tr>
 <tr>
 <td >Monoclonal antibody IV.3</td>
 <td >Medarex (Annandale, NJ) </td>
 <td>025-1 </td>
 <td>Human-specific anti-FcRII (CD32) </td>
 </tr>
 <tr>
 <td >Monoclonal antibody 3G8</td>
 <td >Medarex (Annandale, NJ) </td>
 <td>028-2 </td>
 <td>Human-specific anti-FcRIII (CD16) </td>
 </tr>
 <tr>
 <td >Monoclonal antibody TS2/16</td>
 <td >Dana Farber Cancer Research Institute (Boston, MA) </td>
 <td>Donated by Dr. Martin Hemler </td>
 <td>Human-specific anti-&beta;1 integrin (CD29)</td>
 </tr>
 <tr>
 <td >Monoclonal antibody IB4</td>
 <td >University of California, San Francisco </td>
 <td>Donated by Dr. Eric J. Brown </td>
 <td>Human-specific anti-&beta;2 integrin (CD18)</td>
 </tr>
 <tr>
 <td >F(ab')2 goat anti-mouse IgG </td>
 <td >Cappel (Aurora, OH)</td>
 <td>55468</td>
 <td></td>
 </tr>
 <tr>
 <td>FITC-conjugated F(ab')2 goat anti-mouse IgG</td>
 <td >Cappel (Aurora, OH)</td>
 <td>55522</td>
 <td></td>
 </tr>
 <tr>
 <td>FITC-conjugated F(ab')2 goat anti-rabbit IgG</td>
 <td >Cappel (Aurora, OH)</td>
 <td>55665</td>
 <td></td>
 </tr>
 <tr>
 <td>Anti-NF-&kappa;B p50</td>
 <td >Santa Cruz Biotechnology (Santa Cruz, CA)</td>
 <td>sc-114</td>
 <td>Rabbit polyclonal antibody</td>
 </tr>
 <tr>
 <td>Anti-NF-&kappa;B p65</td>
 <td >Santa Cruz Biotechnology (Santa Cruz, CA)</td>
 <td>sc-109</td>
 <td>Rabbit polyclonal antibody</td>
 </tr>
 <tr>
 <td></td>
 <td></td>
 <td></td>
 <td>EQUIPMENT</td>
 </tr>
 <tr>
 <td>15-ml centrifuge tube</td>
 <td >Corning</td>
 <td>430791</td>
 <td></td>
 </tr>
 <tr>
 <td>50-ml centrifuge tube</td>
 <td >Corning</td>
 <td>430291</td>
 <td></td>
 </tr>
 <tr>
 <td>Centrifuge, Sorvall Tabletop</td>
 <td >Dupont Instruments</td>
 <td>RT 6000D</td>
 <td></td>
 </tr>
 <tr>
 <td>pH-meter</td>
 <td >Corning</td>
 <td>340</td>
 <td></td>
 </tr>
 <tr>
 <td>Pipetman pipette P-20</td>
 <td >Gilson </td>
 <td>F123600</td>
 <td></td>
 </tr>
 <tr>
 <td>Pipetman pipette P-200</td>
 <td >Gilson </td>
 <td>F123601</td>
 <td></td>
 </tr>
 <tr>
 <td>Pipetman pipette P-1000</td>
 <td >Gilson </td>
 <td>F123602</td>
 <td></td>
 </tr>
 <tr>
 <td>Hemocytometer</td>
 <td >Fisher Scientific</td>
 <td>0267110</td>
 <td></td>
 </tr>
 <tr>
 <td>Microscope</td>
 <td >Nikon </td>
 <td>Eclipse E600</td>
 <td></td>
 </tr>
 <tr>
 <td>Inverted microscope</td>
 <td >Nikon </td>
 <td>TMS</td>
 <td></td>
 </tr>
 <tr>
 <td>Water Bath Incubator</td>
 <td >Fisher Scientific </td>
 <td>2IS-M</td>
 <td></td>
 </tr>
 <tr>
 <td>Microcentrifuge</td>
 <td >Eppendorf</td>
 <td>5414C</td>
 <td></td>
 </tr>
 <tr>
 <td>Microcentrifuge</td>
 <td >Eppendorf</td>
 <td>5418</td>
 <td></td>
 </tr>
 <tr>
 <td>Flow Cytometer</td>
 <td >Becton Dickinson (Franklin Lakes, NJ) </td>
 <td>FACScalibur </td>
 <td></td>
 </tr>
 </tbody>
</table>

a simple and efficient method to detect nuclear factor activation in human neutrophils by flow cytometry

Neutrophils are the most abundant leukocytes in peripheral blood. These cells are the first to appear at sites of inflammation and infection, thus becoming the first line of defense against invading microorganisms. Neutrophils possess important antimicrobial functions such as phagocytosis, release of lytic enzymes, and production of reactive oxygen species. In addition to these important defense functions, neutrophils perform other tasks in response to infection such as production of proinflammatory cytokines and inhibition of apoptosis. Cytokines recruit other leukocytes that help clear the infection, and inhibition of apoptosis allows the neutrophil to live longer at the site of infection. These functions are regulated at the level of transcription. However, because neutrophils are short-lived cells, the study of transcriptionally regulated responses in these cells cannot be performed with conventional reporter gene methods since there are no efficient techniques for neutrophil transfection. Here, we present a simple and efficient method that allows detection and quantification of nuclear factors in isolated and immunolabeled nuclei by flow cytometry. We describe techniques to isolate pure neutrophils from human peripheral blood, stimulate these cells with anti-receptor antibodies, isolate and immunolabel nuclei, and analyze nuclei by flow cytometry. The method has been successfully used to detect NF-&kappa;B and Elk-1 nuclear factors in nuclei from neutrophils and other cell types. Thus, this method represents an option for analyzing activation of transcription factors in isolated nuclei from a variety of cell types.

The purification method described here usually provides unstimulated neutrophils (PMN) with purity greater than 95% (Figure 1A). Isolated PMN can then be stimulated by crosslinking particular receptors with specific monoclonal antibodies. We have stimulated PMN through Fc receptors and integrins (Figure 1B). Once stimulated, PMN are lysed and nuclei are isolated with high yields. Nuclei are then immunolabeled for a particular nuclear factor, such as the nuclear factor &kappa;B (NF-&...

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A Simple and Efficient Method to Detect Nuclear Factor Activation in Human Neutrophils by Flow Cytometry

Neutrophils are the most abundant leukocytes in blood. Neutrophils possess transcriptionally regulated functions such as production of proinflammatory cytokines and inhibition of apoptosis. These functions can be studied with the method presented here, which allows detection and quantification of nuclear factors by flow cytometry in isolated nuclei

Neutrophils  are the most abundant leukocytes in peripheral blood. These cells are the first  to appear at sites of inflammation and infection, thus ...

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17.7K Views.  University of Alberta. Neutrophils are the most abundant leukocytes in blood. Neutrophils possess transcriptionally regulated functions such as production of proinflammatory cytokines and inhibition of apoptosis. These functions can be studied with the method presented here, which allows detection and quantification of nuclear factors by flow cytometry in isolated nuclei

Video: A Simple and Efficient Method to Detect Nuclear Factor Activation in Human Neutrophils by Flow Cytometry

Quantitative Assessment of Immune Cells in the Injured Spinal Cord Tissue by Flow Cytometry:  a Novel Use for a Cell Purification Method

Detection of immune cells in the injured central nervous system (CNS) using morphological or histological techniques has not always provided true quantitative analysis of cellular inflammation. Flow cytometry is a quick alternative method to quantify immune cells in the injured brain or spinal cord tissue. Historically, flow cytometry has been used to quantify immune cells collected from blood or dissociated spleen or thymus, and only a few studies have attempted to quantify immune cells in the injured spinal cord by flow cytometry using fresh dissociated cord tissue. However, the dissociated spinal cord tissue is concentrated with myelin debris that can be mistaken for cells and reduce cell count reliability obtained by the flow cytometer. We have advanced a cell preparation method using the OptiPrep gradient system to effectively separate lipid/myelin debris from cells, providing sensitive and reliable quantifications of cellular inflammation in the injured spinal cord by flow cytometry. As described in our recent study (Beck &amp; Nguyen et al., Brain. 2010 Feb; 133 (Pt 2): 433-47), the OptiPrep cell preparation had increased sensitivity to detect cellular inflammation in the injured spinal cord, with counts of specific cell types correlating with injury severity. Critically, novel usage of this method provided the first characterization of acute and chronic cellular inflammation after SCI to include a complete time course for polymorphonuclear leukocytes (PMNs, neutrophils), macrophages/microglia, and T-cells over a period ranging from 2 hours to 180 days post-injury (dpi), identifying a surprising novel second phase of cellular inflammation. Thorough characterization of cellular inflammation using this method may provide a better understanding of neuroinflammation in the injured CNS, and reveal an important multiphasic component of neuroinflammation that may be critical for the design and implementation of rational therapeutic treatment strategies, including both cell-based and pharmacological interventions for SCI.

Quantification of cellular inflammation in the injured/pathological CNS by flow cytometry is complicated by lipid/myelin debris that can have similar size and granulation to cells, decreasing sensitivity/accuracy. We have advanced a cell preparation method to remove myelin debris and improve cell detection by flow cytometry in the injured spinal cord.

Detection of immune cells in the injured central nervous system (CNS) using morphological or histological techniques has not always provided true ...

A Simple and Efficient Method to Isolate Macrophages from Mixed Primary Cultures of Adult Liver Cells

Kupffer cells are liver-specific resident macrophages and play an important role in the physiological and pathological functions of the liver1-3. Although the isolation methods of liver macrophages have been well-described4-6, most of these methods require sophisticated equipment, such as a centrifugal elutriator and technical skills. Here, we provide a novel method to obtain liver macrophages in sufficient number and purity from mixed primary cultures of adult rat liver cells, as schematically illustrated in Figure 1.
After dissociation of the liver cells by two-step perfusion method7,8,a fraction mostly composed of parenchymal hepatocytes is prepared and seeded into T75 tissue culture flasks with culture medium composed of DMEM and 10% FCS.Parenchymal hepatocytes lose the epithelial cell morphology within a few days in culture, degenerate or transform into fibroblast-like cells (Figure 2). As the culture proceeds, around day 6, phase contrast-bright, round macrophage-like cells start to proliferate on the fibroblastic cell sheet (Figure 2). The growth of the macrophage-like cells continue and reach to maximum levels around day 12, covering the cell sheet on the flask surface. By shaking of the culture flasks, macrophages are readily suspended into the culture medium. Subsequent transfer and short incubation in plastic dishes result in selective adhesion of macrophages(Figure 3), where as other contaminating cells remain suspended. After several rinses with PBS, attached macrophages are harvested. More than 106 cells can be harvested repeatedly from the same T75 tissue culture flask at two to three day intervals for more than two weeks(Figure 3).The purities of the isolated macrophages were 95 to 99%, as evaluated by flow cytometry or immunocytochemistry with rat macrophage-specific antibodies (Figure 4).The isolated cells show active phagocytosis of polystylene beads (Figure 5), proliferative response to recombinant GM-CSF, secretion of inflammatory/anti-inflammatory cytokines upon stimulation with LPS, and formation of multinucleated giant cells9.
In conclusion, we provide a simple and efficient method to obtain liver macrophages in sufficient number and purity without complex equipment and skills.This method might be applicable to other mammalian species.

A novel method to obtain macrophages from primary culture of rat liver cells is described. This method utilizes the proliferation of macrophages in the culture, followed by shaking of culture flasks and purification by selective attachment to plastic dishes. This technique efficiently provides liver macrophages without complex equipment and skills.

Kupffer cells are liver-specific resident macrophages and play an important role in the physiological and pathological functions of the liver1-3. Although ...

Human In Vitro Suppression as Screening Tool for the Recognition of an Early State of Immune Imbalance

Regulatory T cells (Tregs) are critical mediators of immune tolerance to self-antigens. In addition, they are crucial regulators of the immune response following an infection. Despite efforts to identify unique surface marker on Tregs, the only unique feature is their ability to suppress the proliferation and function of effector T cells. While it is clear that only in vitro assays can be used in assessing human Treg function, this becomes problematic when assessing the results from cross-sectional studies where healthy cells and cells isolated from subjects with autoimmune diseases (like Type 1 Diabetes-T1D) need to be compared. There is a great variability among laboratories in the number and type of responder T cells, nature and strength of stimulation, Treg:responder ratios and the number and type of antigen-presenting cells (APC) used in human in vitro suppression assays. This variability makes comparison between studies measuring Treg function difficult. The Treg field needs a standardized suppression assay that will work well with both healthy subjects and those with autoimmune diseases. We have developed an in vitro suppression assay that shows very little intra-assay variability in the stimulation of T cells isolated from healthy volunteers compared to subjects with underlying autoimmune destruction of pancreatic &beta;-cells. The main goal of this piece is to describe an in vitro human suppression assay that allows comparison between different subject groups. Additionally, this assay has the potential to delineate a small loss in nTreg function and anticipate further loss in the future, thus identifying subjects who could benefit from preventive immunomodulatory therapy1. Below, we provide thorough description of the steps involved in this procedure. We hope to contribute to the standardization of the in vitro suppression assay used to measure Treg function. In addition, we offer this assay as a tool to recognize an early state of immune imbalance and a potential functional biomarker for T1D.

Human In Vitro Suppression as Screening Tool for the Recognition of an Early State of Immune Imbalance

Tregs are potent suppressors of the immune system. There is a lack of unique surface markers to define them, hence, definitions of Tregs are primarily functional. Here we describe an optimized in vitro assay capable of identifying immune imbalance in subjects at risk to develop T1D.

Regulatory T cells (Tregs) are critical mediators of immune tolerance to self-antigens. In addition, they are crucial regulators of the immune response ...

Examination of Thymic Positive and Negative Selection by Flow Cytometry

A healthy immune system requires that T cells respond to foreign antigens while remaining tolerant to self-antigens. Random rearrangement of the T cell receptor (TCR) &alpha; and &beta; loci generates a T cell repertoire with vast diversity in antigen specificity, both to self and foreign. Selection of the repertoire during development in the thymus is critical for generating safe and useful T cells. Defects in thymic selection contribute to the development of autoimmune and immunodeficiency disorders1-4. 
T cell progenitors enter the thymus as double negative (DN) thymocytes that do not express CD4 or CD8 co-receptors. Expression of the &alpha;&beta;TCR and both co-receptors occurs at the double positive (DP) stage. Interaction of the &alpha;&beta;TCR with self-peptide-MHC (pMHC) presented by thymic cells determines the fate of the DP thymocyte. High affinity interactions lead to negative selection and elimination of self-reactive thymocytes. Low affinity interactions result in positive selection and development of CD4 or CD8 single positive (SP) T cells capable of recognizing foreign antigens presented by self-MHC5.
Positive selection can be studied in mice with a polyclonal (wildtype) TCR repertoire by observing the generation of mature T cells. However, they are not ideal for the study of negative selection, which involves deletion of small antigen-specific populations. Many model systems have been used to study negative selection but vary in their ability to recapitulate physiological events6. For example, in vitro stimulation of thymocytes lacks the thymic environment that is intimately involved in selection, while administration of exogenous antigen can lead to non-specific deletion of thymocytes7-9. Currently, the best tools for studying in vivo negative selection are mice that express a transgenic TCR specific for endogenous self-antigen. However, many classical TCR transgenic models are characterized by premature expression of the transgenic TCR&alpha; chain at the DN stage, resulting in premature negative selection. Our lab has developed the HYcd4 model, in which the transgenic HY TCR&alpha; is conditionally expressed at the DP stage, allowing negative selection to occur during the DP to SP transition as occurs in wildtype mice10.
Here, we describe a flow cytometry-based protocol to examine thymic positive and negative selection in the HYcd4 mouse model. While negative selection in HYcd4 mice is highly physiological, these methods can also be applied to other TCR transgenic models. We will also present general strategies for analyzing positive selection in a polyclonal repertoire applicable to any genetically manipulated mice.

We present a flow cytometry-based method to examine T cell development in vivo using genetically manipulated mice on a wildtype or T cell receptor transgenic background.

A healthy immune system requires that T cells respond to foreign  antigens while remaining tolerant to self-antigens. Random rearrangement of the  T cell ...

Studying Interactions of Staphylococcus aureus with Neutrophils by Flow Cytometry and Time Lapse Microscopy

We present methods to study the effect of phenol soluble modulins (PSMs) and other toxins produced and secreted by Staphylococcus aureus on neutrophils. To study the effects of the PSMs on neutrophils we isolate fresh neutrophils using density gradient centrifugation. These neutrophils are loaded with a dye that fluoresces upon calcium mobilization. The activation of neutrophils by PSMs initiates a rapid and transient increase in the free intracellular calcium concentration. In a flow cytometry experiment this rapid mobilization can be measured by monitoring the fluorescence of a pre-loaded dye that reacts to the increased concentration of free Ca2+. Using this method we can determine the PSM concentration necessary to activate the neutrophil, and measure the effects of specific and general inhibitors of the neutrophil activation.	
	To investigate the expression of the PSMs in the intracellular space, we have constructed reporter fusions of the promoter of the PSM&alpha; operon to GFP. When these reporter strains of S. aureus are phagocytosed by neutrophils, the induction of expression can be observed using fluorescence microscopy.

Studying Interactions of Staphylococcus aureus with Neutrophils by Flow Cytometry and Time Lapse Microscopy

We present methods to study the effect of PSMs and other toxins secreted by Staphylococcus aureus on neutrophils using flow cytometry and fluorescence microscopy.

We present methods to study the effect of phenol soluble modulins (PSMs)  and other toxins produced and secreted by Staphylococcus  aureus on neutrophils. ...

A Simple and Rapid Protocol to Non-enzymatically Dissociate Fresh Human Tissues for the Analysis of Infiltrating Lymphocytes

The ability of malignant cells to evade the immune system, characterized by tumor escape from both innate and adaptive immune responses, is now accepted as an important hallmark of cancer. Our research on breast cancer focuses on the active role that tumor infiltrating lymphocytes play in tumor progression and patient outcome. Toward this goal, we developed a methodology for the rapid isolation of intact lymphoid cells from normal and abnormal tissues in an effort to evaluate them proximate to their native state. Homogenates prepared using a mechanical dissociator show both increased viability and cell recovery while preserving surface receptor expression compared to enzyme-digested tissues. Furthermore, enzymatic digestion of the remaining insoluble material did not recover additional CD45+ cells indicating that quantitative and qualitative measurements in the primary homogenate likely genuinely reflect infiltrating subpopulations in the tissue fragment. The lymphoid cells in these homogenates can be easily characterized using immunological (phenotype, proliferation, etc.) or molecular (DNA, RNA and/or protein) approaches. CD45+ cells can also be used for subpopulation purification, in vitro expansion or cryopreservation. An additional benefit of this approach is that the primary tissue supernatant from the homogenates can be used to characterize and compare cytokines, chemokines, immunoglobulins and antigens present in normal and malignant tissues. This protocol functions extremely well for human breast tissues and should be applicable to a wide variety of normal and abnormal tissues.

This protocol describes the rapid non-enzymatic dissociation of fresh human tissue fragments for qualitative and quantitative assessment of CD45+ cells (lymphocytes/leukocytes) present in various normal and malignant human tissues. Additionally, the supernatant obtained from the primary tissue homogenate can be collected and stored for further analysis or experimentation.

The ability of malignant cells to evade the immune system, characterized by tumor escape from both innate and adaptive immune responses, is now accepted ...

A Simple and Efficient Approach to Construct Mutant Vaccinia Virus Vectors

The CRISPR-associated endonuclease Cas9 can edit particular genomic loci directed by a single guide RNA (gRNA). The CRISPR/Cas9 system has been successfully employed for editing genomes of various organisms. Here we describe a protocol for editing the vaccinia virus (VV) genome in the cytoplasm of VV-infected CV-1 cells using the RNA-guided Cas9. RNA-guided Cas9 induces double-stranded DNA breaks facilitating homologous recombination efficiently and specifically in the targeted site of VV and a transgene can be incorporated into these sites by homologous recombination. By using a site-specific homologous vector with transgene(s), a N1L gene-deleted VV with the red fluorescence protein (RFP) gene incorporated in this region was generated with a successful recombination efficiency 10 times greater than that obtained from the conventional homologous recombination method. This protocol demonstrates successful use of RNA-guided Cas9 system to generate mutant VVs with enhanced efficiency.

Vaccinia virus (VV) has been widely used in biomedical research and the improvement of human health. This article describes a simple, highly efficient method to edit the VV genome using a CRISPR-Cas9 system.

The CRISPR-associated endonuclease Cas9 can edit particular genomic loci directed by a single guide RNA (gRNA). The CRISPR/Cas9 system has been ...

Live Imaging of Antifungal Activity by Human Primary Neutrophils and Monocytes in Response to A. fumigatus

Aspergillus fumigatus is an opportunistic fungal pathogen causing invasive infections in immunocompromised hosts with a high case-fatality rate. Research investigating immunological responses against A. fumigatus has been limited by the lack of consistent and reliable assays for measuring the antifungal activity of specific immune cells in vitro. A new method is described to assess the antifungal activity of primary monocytes and neutrophils from human donors against A. fumigatus using FLuorescent Aspergillus REporter (FLARE) conidia. These conidia contain a genetically encoded dsRed reporter, which is constitutively expressed by live FLARE conidia, and are externally labeled with Alexa Fluor 633, which is resistant to degradation within the phagolysosome, thus allowing a distinction between live and dead A. fumigatus conidia. Video microscopy and flow cytometry are subsequently used to visualize the interaction between conidia and innate immune cells, assessing fungicidal activity whilst also providing a wealth of information on phagocyte migration, phagocytosis and the inhibition of fungal growth. This novel technique has already provided exciting new insights into the host-pathogen interaction of primary immune cells against A. fumigatus. It is important to note the laboratory setup required to perform this assay, including the necessary microscopy and flow cytometry facilities, and the capacity to work with human donor blood and genetically manipulated fungi. However, this assay is capable of generating large amounts of data and can reveal detailed insights into the antifungal response. This protocol has successfully been used to study the host-pathogen interaction of primary immune cells against A. fumigatus.
It is important to note the laboratory setup required to perform this assay, including the necessary microscopy and flow cytometry facilities, and the capacity to work with human donor blood and genetically manipulated fungi. However, this assay is capable of generating large amounts of data and can reveal detailed insights into the antifungal response. This protocol has successfully been used to study the host-pathogen interaction of primary immune cells against A. fumigatus.

Live Imaging of Antifungal Activity by Human Primary Neutrophils and Monocytes in Response to A. fumigatus

Here, we describe a protocol to assess antifungal activity of primary human immune cells in real-time using fluorescent Aspergillus reporter conidia in conjunction with live-cell video microscopy and flow cytometry. Generated data provide insight into host cell-Aspergillus interactions such as fungicidal activity, phagocytosis, cell migration and inhibition of fungal growth.

Aspergillus fumigatus is an opportunistic fungal pathogen causing invasive infections in immunocompromised hosts with a high case-fatality rate. Research ...

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 ...

Characterization of Human Monocyte Subsets by Whole Blood Flow Cytometry Analysis

Monocytes are key contributors in various inflammatory disorders and alterations to these cells, including their subset proportions and functions, can have pathological significance. An ideal method for examining alterations to monocytes is whole blood flow cytometry as the minimal handling of samples by this method limits artifactual cell activation. However, many different approaches are taken to gate the monocyte subsets leading to inconsistent identification of the subsets between studies. Here we demonstrate a method using whole blood flow cytometry to identify and characterize human monocyte subsets (classical, intermediate, and non-classical). We outline how to prepare the blood samples for flow cytometry, gate the subsets (ensure contaminating cells have been removed), and determine monocyte subset expression of surface markers &#8212; in this example M1 and M2 markers. This protocol can be extended to other studies that require a standard gating method for assessing monocyte subset proportions and monocyte subset expression of other functional markers.

Here we present a protocol for characterizing monocyte subsets by whole blood flow cytometry. This includes outlining how to gate the subsets and assess their expression of surface markers and giving an example of the assessment of the expression of M1 (inflammatory) and M2 markers (anti-inflammatory).

Monocytes are key contributors in various inflammatory disorders and alterations to these cells, including their subset proportions and functions, can ...