This work was supported by the National Natural Science Foundation of China (grant numbers 81430099 and 31500704), International Cooperation and Exchange Projects (grant number 2014DFA32950), and the research program of Beijing University of Chinese Medicine (grant numbers BUCM-2019-JCRC006 and 2019-JYB-TD013).

All experimental procedures were reviewed and approved by the Beijing University of Chinese Medicine Animal Care and Use Committee.
NOTE: C57BL/6 mice (7-8 weeks old) were used.
1. Neutrophil isolation
<ol>
	<li>Acquisition of peritoneal exudate cells
	<ol>
		<li>Prepare fresh 10% proteose peptone solution in ddH2O. Calculate the volume needed according to the number of mice. 
		NOTE: Set the number of mice as N, (2N+1) mL of solution must be disso...

<ol>
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S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+Neutrophil+Chemotaxis.">Analysis of Neutrophil Chemotaxis.</a> Adhesion Protein Protocols. , 23-35 (2007).</li><li>Margraf, A., Ley, K., Zarbock, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neutrophil+Recruitment:+From+Model+Systems+to+Tissue-Specific+Patterns.">Neutrophil Recruitment: From Model Systems to Tissue-Specific Patterns.</a> Trends in Immunology. 40 (7), 613-634 (2019).</li><li>Bardoel, B. W., Kenny, E. F., Sollberger, G., Zychlinsky, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+balancing+act+of+neutrophils.">The balancing act of neutrophils.</a> Cell Host &amp; Microbe. 15 (5), 526-536 (2014).</li><li>Wright, H. L., Moots, R. 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H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+improved+chamber+for+direct+visualisation+of+chemotaxis.">An improved chamber for direct visualisation of chemotaxis.</a> PLoS One. 5 (12), e15309 (2010).</li><li>Walheim, C. C., Zanin, J. P., de Bellard, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+trunk+neural+crest+cell+migration+using+a+modified+Zigmond+chamber+assay.">Analysis of trunk neural crest cell migration using a modified Zigmond chamber assay.</a> Journal of Visualized Experiments. (59), e3330 (2012).</li><li>Liew, P. X., Kubes, P. <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's+Role+During+Health+and+Disease.">The Neutrophil's Role During Health and Disease.</a> Physiological Reviews. 99 (2), 1223-1248 (2019).</li><li>Ley, 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=Neutrophils:+New+insights+and+open+questions.">Neutrophils: New insights and open questions.</a> Science Immunology. 3 (30), eaat4579 (2018).</li><li>Tillack, K., Breiden, P., Martin, R., Sospedra, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=T+lymphocyte+priming+by+neutrophil+extracellular+traps+links+innate+and+adaptive+immune+responses.">T lymphocyte priming by neutrophil extracellular traps links innate and adaptive immune responses.</a> Journal of Immunology. 188 (7), 3150-3159 (2012).</li><li>Puga, I., 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=B+cell-helper+neutrophils+stimulate+the+diversification+and+production+of+immunoglobulin+in+the+marginal+zone+of+the+spleen.">B cell-helper neutrophils stimulate the diversification and production of immunoglobulin in the marginal zone of the spleen.</a> Nature Immunology. 13 (2), 170-180 (2011).</li><li>Strzepa, A., Pritchard, K. A., Dittel, B. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Myeloperoxidase:+A+new+player+in+autoimmunity.">Myeloperoxidase: A new player in autoimmunity.</a> Cellular Immunology. 317, 1-8 (2017).</li><li>Momohara, S., Kashiwazaki, S., Inoue, K., Saito, S., Nakagawa, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Elastase+from+polymorphonuclear+leukocyte+in+articular+cartilage+and+synovial+fluids+of+patients+with+rheumatoid+arthritis.">Elastase from polymorphonuclear leukocyte in articular cartilage and synovial fluids of patients with rheumatoid arthritis.</a> Clinical Rheumatology. 16 (2), 133-140 (1997).</li><li>Swamydas, M., Luo, Y., Dorf, M. E., Lionakis, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+of+Mouse+Neutrophils.">Isolation of Mouse Neutrophils.</a> Current Protocols in Immunology. 110 (1), 3.20.1-3.20.15 (2015).</li><li>Luo, Y., Dorf, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+of+Mouse+Neutrophils.">Isolation of Mouse Neutrophils.</a> Current Protocols in Immunology. 22 (1), 3.20.1-3.20.6 (1997).</li><li>Carlson, 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=Human+neutrophil+lipocalin+is+a+unique+marker+of+neutrophil+inflammation+in+ulcerative+colitis+and+proctitis.">Human neutrophil lipocalin is a unique marker of neutrophil inflammation in ulcerative colitis and proctitis.</a> Gut. 50 (4), 501-506 (2002).</li><li>Nathan, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neutrophils+and+immunity:+challenges+and+opportunities.">Neutrophils and immunity: challenges and opportunities.</a> Nature Reviews Immunology. 6 (3), 173-182 (2006).</li><li>Zhang, S., 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=Tanshinone+IIA+ameliorates+chronic+arthritis+in+mice+by+modulating+neutrophil+activities.">Tanshinone IIA ameliorates chronic arthritis in mice by modulating neutrophil activities.</a> Clinical and Experimental Immunology. 190 (1), 29-39 (2017).</li><li>Forster, R., Sozzani, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Emerging+aspects+of+leukocyte+migration.">Emerging aspects of leukocyte migration.</a> European Journal of Immunology. 43 (6), 1404-1406 (2013).</li><li>Hu, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neutrophil-Mediated+Delivery+of+Dexamethasone+Palmitate-Loaded+Liposomes+Decorated+with+a+Sialic+Acid+Conjugate+for+Rheumatoid+Arthritis+Treatment.">Neutrophil-Mediated Delivery of Dexamethasone Palmitate-Loaded Liposomes Decorated with a Sialic Acid Conjugate for Rheumatoid Arthritis Treatment.</a> Pharmaceutical Research. 36 (7), 97 (2019).</li></ol>

Detailed protocols of highly-purified neutrophils from peripheral blood7, bone marrow and tissues18 have been available for a long time. Here we adopt a method of isolating neutrophils from peritoneal fluid19 in which mature neutrophils remain inactivated for further anti-inflammatory and antioxidant studies.
We used the air pouch experiment to explore the LPS-induced infiltration of neutrophils in vivo. This method has be...

Neutrophils are the most abundant white blood cell and account for 50&#8722;70% of the whole white blood cell population in humans1. Neutrophils are one of the primary responders during acute inflammation. Neutrophils can be recruited to inflammation sites via the guidance of cytokines and chemokines released by tissue-resident cells2,3,4, which is mediated by the interactions between cell adhesion molecules on the surface of neutrophils and vascular endothelium cells5. Neutrophils are fundamental to host defense and play a role in pathologic inflammatory reactions due to their powerful capacity to damage tissue via the release of reactive oxygen species (ROS) and other tissue-damaging molecules3,6.
Previous studies have described several neutrophil isolation protocols from mice or humans. Oh et al. demonstrated a density gradient separation method to isolate human neutrophils from whole human blood7. However, the isolation of sufficient neutrophils from mouse blood is difficult because of the small blood volume. Alternatively, large numbers of pure and viable mouse neutrophils can be elicited from mouse peritoneal fluid, and these purified neutrophils can be used ex vivo to examine several aspects of cellular functions ex vivo, including neutrophil infiltration, migration, chemotaxis, oxidative burst, cytokine and neutrophil extracellular trap (NET) production8. Transwell assays9 or Zigmond chamber assays10,11 can be used to evaluate neutrophil migration in vitro. The air pouch model is used to evaluate the migration and infiltration of neutrophils in vivo. The subcutaneous air pouch model is a convenient in vivo animal model to study the migration of inflammatory cells.
Traditionally, neutrophils were considered as pathogen eliminators in acute phases of inflammation. However, recent findings have shown that neutrophils are complicated cells that perform a significant variety of specialized functions. Neutrophils can regulate many processes such as acute injury and repair, tumorigenesis, autoimmune response, and chronic inflammation12,13. Neutrophils also modulate adaptive immune responses and can regulate B cells and T cells14,15. Substantial shortage of neutrophils leads to mortality or severe immunodeficiency in humans and neutrophil depletion in mice leads to fatality, while excessive activation or recruitment of neutrophils in organs causes several immune diseases, such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE)6. Neutrophils are the most abundant cells in the synovial fluid of RA patients. Neutrophils produce excessive amounts of myeloperoxidase (MPO) and neutrophil elastase (NE) via degradation, which exacerbates cartilage erosion. MPO is a peroxidase enzyme mainly expressed in the granules of neutrophils16. NE is associated with articular cartilage destruction17. MPO and NE could be used to evaluate the status of neutrophil migration and infiltration in the tissue of RA patients.
This article provides three conventional methods to evaluate the migration of normal neutrophils induced both in vivo and in vitro, as well as the infiltration of pathological neutrophils in a mouse joint-specific inflammation model.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.1% Fast Green Solution</td>
			<td>Solarbio</td>
			<td>8348b</td>
			<td>Transfer 20 mg of fast grene FCF in one vial into another 100 mL beaker. Add 20 mL of H2O into the beaker and dissolve the stain by stirring to make 0.1% fast green solution, and filter it using a Nalgene PES 75mm filter</td>
		</tr>
		<tr>
			<td>0.1% Safranin O Staining Solution</td>
			<td>Solarbio</td>
			<td>8348a</td>
			<td>Transfer 20 mg of safranin O stain in one vial into a 100 ml beaker. Add 20 mL of H2O into the beaker and dissolve the stain by stirring to make 0.1% safranin O staining solution, and filter it using a Nalgene PES 75mm filter</td>
		</tr>
		<tr>
			<td>0.5 M Ethylenediaminetetraacetic acid solution (EDTA), pH 8.0</td>
			<td>Sigma</td>
			<td>324506</td>
			<td>Sterile</td>
		</tr>
		<tr>
			<td>100% Ethanol</td>
			<td>Beijing Chemical Works</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>100% Methanol</td>
			<td>Beijing Chemical Works</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>15 mL Conical Polypropylene Centrifuge Tube</td>
			<td>Falcon</td>
			<td>14-959-53A</td>
			<td></td>
		</tr>
		<tr>
			<td>23 G x 1 1/4&#34; Needle</td>
			<td>BD</td>
			<td>305120</td>
			<td></td>
		</tr>
		<tr>
			<td>26 G x 3/8&#34; Needle</td>
			<td>BD</td>
			<td>305110</td>
			<td></td>
		</tr>
		<tr>
			<td>3% bovine serum albumin (BSA)</td>
			<td></td>
			<td></td>
			<td>Dissolve 0.3 g BSA in 10 mL PBS</td>
		</tr>
		<tr>
			<td>3% H2O2</td>
			<td></td>
			<td></td>
			<td>Mix 1 mL 30% H2O2 with methanol with 9 mL methanol</td>
		</tr>
		<tr>
			<td>3,3&#39;-diaminobenzidine (DAB) kit</td>
			<td>ZSGB-BIO</td>
			<td>ZLI-9018</td>
			<td></td>
		</tr>
		<tr>
			<td>30 G x 1/2&#34; Needle</td>
			<td>BD</td>
			<td>305106</td>
			<td></td>
		</tr>
		<tr>
			<td>30% H2O2</td>
			<td>Beijing Chemical Works</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>5 mL Syringe</td>
			<td>BD</td>
			<td>Z683574</td>
			<td></td>
		</tr>
		<tr>
			<td>50 mL Conical Polypropylene Centrifuge Tube</td>
			<td>Falcon</td>
			<td>14-432-22</td>
			<td></td>
		</tr>
		<tr>
			<td>50% Ethanol</td>
			<td></td>
			<td></td>
			<td>Mix 500 mL 100% ethanol with 500 mL dH2O</td>
		</tr>
		<tr>
			<td>54.8% Percoll</td>
			<td></td>
			<td></td>
			<td>Mix 2.74 mL SIP with 2.26 mL 1&#215;PBS, stand still</td>
		</tr>
		<tr>
			<td>70% Ethanol</td>
			<td></td>
			<td></td>
			<td>Mix 700 mL 100% ethanol with 300 mL dH2O</td>
		</tr>
		<tr>
			<td>70.2% Percoll</td>
			<td></td>
			<td></td>
			<td>Mix 3.51 mL SIP with 1.49 mL 1&#215;PBS, stand still</td>
		</tr>
		<tr>
			<td>80% Ethanol</td>
			<td></td>
			<td></td>
			<td>Mix 800 mL 100% ethanol with 200 mL dH2O</td>
		</tr>
		<tr>
			<td>95% Ethanol</td>
			<td></td>
			<td></td>
			<td>Mix 950 mL 100% ethanol with 50 mL dH2O</td>
		</tr>
		<tr>
			<td>Acid Alcohol Superfast Differentiation Solution</td>
			<td>Beyotime</td>
			<td>C0165S</td>
			<td></td>
		</tr>
		<tr>
			<td>ANTIBODIES</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-Myeloperoxidase Antibody</td>
			<td>Abcam</td>
			<td>ab208670</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-Neutrophil Elastase Antibody</td>
			<td>Abcam</td>
			<td>ab21595</td>
			<td></td>
		</tr>
		<tr>
			<td>Automatic Hematology Analyzer</td>
			<td>Sysmex</td>
			<td>XS-800i</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin (BSA)</td>
			<td>VWR</td>
			<td>0332-100G</td>
			<td></td>
		</tr>
		<tr>
			<td>Complete Freund&#39;s Adjuvant, 10 mg/ml</td>
			<td>sigma</td>
			<td>1002036152</td>
			<td></td>
		</tr>
		<tr>
			<td>Cover Slip</td>
			<td>CITOGLAS</td>
			<td>10212432C</td>
			<td></td>
		</tr>
		<tr>
			<td>Dial Thickness Gauge</td>
			<td>Mitutoyo</td>
			<td>7301</td>
			<td></td>
		</tr>
		<tr>
			<td>Eppendorf Microtubes, 1.5 mL</td>
			<td>Sigma</td>
			<td>Z606340</td>
			<td></td>
		</tr>
		<tr>
			<td>Foetal Bovine Serum (FBS) Premium</td>
			<td>PAN</td>
			<td>P30-1302</td>
			<td></td>
		</tr>
		<tr>
			<td>Gas Anesthesia System</td>
			<td>ZS Dichuang</td>
			<td>ZS-MV-IV</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat Anti-Rabbit IgG H&#38;L (HRP)</td>
			<td>PPLYGEN</td>
			<td>C1309</td>
			<td>This is the secondary antibody used in the immunohistochemical staining.</td>
		</tr>
		<tr>
			<td>Hank&#39;s Balanced Salt Solution (HBSS)</td>
			<td>Biological Industries, Beth HaEmek, Israel</td>
			<td>02-016-1A</td>
			<td>Sterile</td>
		</tr>
		<tr>
			<td>Hematoxylin Staining Solution</td>
			<td>ZSGB-BIO</td>
			<td>ZLI-9609</td>
			<td></td>
		</tr>
		<tr>
			<td>Lipopolysaccharide (LPS)</td>
			<td>Sigma</td>
			<td>L3012</td>
			<td></td>
		</tr>
		<tr>
			<td>MEDIA AND SUPPLEMENTS</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Modified Safranin O-fast Green FCF Cartilage Stain Kit</td>
			<td>Solarbio</td>
			<td>G1371</td>
			<td></td>
		</tr>
		<tr>
			<td>N-formyl-Met-Leu-Phe (fMLP)</td>
			<td>Sigma</td>
			<td>47729</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin Streptomycin Solution, 100&#215;</td>
			<td>Invitrogen</td>
			<td>1514022</td>
			<td></td>
		</tr>
		<tr>
			<td>Percoll</td>
			<td>GE Healthcare</td>
			<td>10245207</td>
			<td>Density gradient medium</td>
		</tr>
		<tr>
			<td>Permeabilization Buffer</td>
			<td></td>
			<td></td>
			<td>Mix 100 &#956;L Triton X-100 with 1 L dH2O to get 0.01% Triton X-100</td>
		</tr>
		<tr>
			<td>Phosphate Buffer Saline (PBS), 1&#215;</td>
			<td></td>
			<td></td>
			<td>Mix 90% ddH2O with 10% (v/v) 10&#215;PBS, autoclaved</td>
		</tr>
		<tr>
			<td>Phosphate Buffer Saline (PBS), 10&#215;</td>
			<td></td>
			<td></td>
			<td>Dissolve 16 g NaCl, 0.4 g KCl, 2.88 g Na2HPO4&#183;2H2O, 0.48 g KH2PO4 (anhydrous) in 200 mL ddH2O, adjust pH 7.4, autoclaved</td>
		</tr>
		<tr>
			<td>PLASTIC WARES AND EQUIPMENTS</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>POWDER</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Proteose Peptone</td>
			<td>Oxoid</td>
			<td>1865317</td>
			<td></td>
		</tr>
		<tr>
			<td>Retrieval Buffer</td>
			<td></td>
			<td></td>
			<td>Mix 18 mL retrieval buffer A with 82 mL retrieval buffer B, add dH2O to 1000 mL, adjust pH to 6.0</td>
		</tr>
		<tr>
			<td>Retrieval Buffer A Stock for IHC</td>
			<td></td>
			<td></td>
			<td>Dissolve 4.2 g citric acid (C6H5O7&#183;H2O) in 200 mL dH2O</td>
		</tr>
		<tr>
			<td>Retrieval Buffer B Stock for IHC</td>
			<td></td>
			<td></td>
			<td>Dissolve 5.88 g trisodium citrate dihydrate (C6H5Na3O7&#183;2H20) in 200 mL dH2O</td>
		</tr>
		<tr>
			<td>Roswell Park Memorial Institute (RPMI)-1640 medium</td>
			<td>Sigma</td>
			<td>R8758</td>
			<td></td>
		</tr>
		<tr>
			<td>RPMI-1640 Complete Medium</td>
			<td></td>
			<td></td>
			<td>RPMI-1640 medium is supplemented with 10% FBS and 1% penicillin/streptomycin.</td>
		</tr>
		<tr>
			<td>Shu Rui U40 Disposable Sterile Insulin Injection Needle 1 mL</td>
			<td>BD</td>
			<td>328421</td>
			<td></td>
		</tr>
		<tr>
			<td>Slide</td>
			<td>CITOGLAS</td>
			<td>10127105P-G</td>
			<td></td>
		</tr>
		<tr>
			<td>SOLUTION</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Stock Isotonic Percoll (SIP)</td>
			<td></td>
			<td></td>
			<td>Mix 90% (v/v) of percoll with 10% (v/v) 10&#215;PBS, stand still for 20 min</td>
		</tr>
		<tr>
			<td>Wash Buffer in Air Pouch Assay</td>
			<td></td>
			<td></td>
			<td>Dilute 0.5M EDTA to 10mM with HBSS</td>
		</tr>
		<tr>
			<td>Xylene</td>
			<td>Beijing Chemical Works</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

detecting migration and infiltration of neutrophils in mice

Neutrophils are a major member of the innate immune system and play pivotal roles in host defense against pathogens and pathologic inflammatory reactions. Neutrophils can be recruited to inflammation sites via the guidance of cytokines and chemokines. Overwhelming infiltration of neutrophils can lead to indiscriminate tissue damage, such as in rheumatoid arthritis (RA). Neutrophils isolated from peritoneal exudate respond to a defined chemoattractant, N-formyl-Met-Leu-Phe (fMLP), in vitro in Transwell or Zigmond chamber assays. The air pouch experiment can be used to evaluate the chemotaxis of neutrophils towards lipopolysaccharide (LPS) in vivo. The adjuvant-induced arthritis (AA) mouse model is frequently used in RA research, and immunohistochemical staining of joint sections with anti-myeloperoxidase (MPO) or anti-neutrophil elastase (NE) antibodies is a well-established method to measure neutrophil infiltration. These methods can be used to discover promising therapies targeting neutrophil migration.

Peritoneal exudate cells were collected from lavage fluid of mice. Cells were resuspended in 1 mL of RPMI-1640 complete medium, layered onto a two-step (54.8%/70.2%) discontinuous density gradient (Figure 1A), and centrifuged at 1,500 x g for 30 min. Neutrophils (&#8805;95%, ~1 x 107 neutrophils/mouse) were recovered from the lower interface (Figure 1B).
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Watch this Scientific Journal Video about Detecting Migration and Infiltration of Neutrophils in Mice at JoVE.com

Detecting Migration and Infiltration of Neutrophils in Mice

Here, we present three methods to assess neutrophil migration and infiltration both in vivo and in vitro. These methods can be used to discover promising therapeutics targeting neutrophil migration.

Neutrophils are a major member of the innate immune system and play pivotal roles in host defense against pathogens and pathologic inflammatory reactions. ...

This method tries to describe three frequently used methods for evaluating the migration of normal neutrophils in vivo and in vitro as well as the infiltration of pathological neutrophils in mouse arthritis model. We think this method could be useful for other researchers in this field. This protocol contains the methodological details to evaluate the migration capacity of neutrophils in the inflammation sites by using air pouch assay and adjuvant-induced arthritis.The implications of this technique extend towards the arthritis therapy by comparing the model group with the treatment group. This method could provide insight into inflammatory disease and can be applied to inflammatory bowel disease. Demonstrating the procedure will be Qingyi Lu and Haixu Jiang, post-graduate students from our lab.After anesthetization of the mice on day zero, use a 0.22 micron filter attached to a five milliliter syringe to obtain a three milliliter volume of sterilized air. Lift the back skin of the anesthetized mouse with tweezers and subcutaneously use a 26 gauge by 3/8 inch needle to inject three milliliters of the sterilized air. After treatment, remove the mice from the breathing unit and place them into a well set cage.Monitor the mice to ensure they are alive until they start to move around. On day three, inject an additional three milliliters of sterilized air into the previously established air pocket to sustain the air pouch. On day six, inject different treatments into the air pouch.Inject one milliliter of PBS as a negative control and inject one milliliter of one microgram per milliliter LPS as the positive control to induce local inflammation. After six hours, sacrifice the mice. For each air pouch, inject one milliliter of wash buffer to wash the air pouch and collect the inflammatory exudate in a 15 milliliter centrifuge tube.Then wash the air pouch with two milliliters of wash buffer twice and collect the inflammatory exudate in the same centrifuge tube. Centrifuge at 100 times g for 10 minutes at room temperature. Discard the supernatant and resuspend the cells in one milliliter of wash buffer.Count the cells to quantify the neutrophil ratio using the automatic hematology analyzer. Suspend complete Freund's adjuvant by vortexing at least five seconds, then draw 100 microliters of suspension into an insulin injector. After anesthetizing, mark the chosen paw and inject 20 microliters of complete Freund's adjuvant from the injector into four periarticular spots on the ankle joint space.Put the processed mice in the new chamber. Monitor the mice to ensure that they are breathing until they regain the ability to move. Every three days, use a pocket thickness gauge to measure the ankle joint diameter.Also, assess arthritis severity by arthritis scoring criterion. Zero is normal. No evidence of erythema and swelling.One is the mildest arthritis. Erythema and mild swelling confined to the tarsals or ankle joint. Two is the moderate arthritis.Erythema and mild swelling extending from the ankle to the tarsals. Three is the severe arthritis. Erythema and moderate swelling extending from the ankle to metatarsal joints.Four is the most severe arthritis. Erythema and severe swelling encompass the ankle, foot, and digits, or ankylosis of the limb. After sacrificing the mouse, remove the skin and part of the muscle from the hind leg with tweezers and scissors.Spray the joint with 70%ethanol and remove the rest of the muscles using a paper towel. Fix the ankle joint in 4%paraformaldehyde for two days at room temperature. Then decalcify the joint in 10%EDTA for one month at room temperature and change the medium weekly.After one month, place the tissue in a marked mold with certain volume of liquid paraffin at approximately 60 degrees Celsius to embed the tissue. Cool briefly. Set the thickness on the microtome at four micrometers and cut slices.Then float the sections in a 43 degree Celsius water bath for a short time to expand the sections. Mount the sections onto slides and put the slides into the oven at 70 degrees Celsius for two hours. For future use, conserve the slides at minus 20 degrees Celsius.Next, place the slides in a rack and perform washes in xylene and ethanol according to the manuscript to rehydrate at room temperature. Lastly, wash in running tap water for three minutes. Then stain in 0.1%fast green solution for five minutes.Rinse in 1%acetic acid for 10 seconds and stain in 0.1%Safranin O staining solution for 20 minutes. After that, immerse the slides in the xylene and ethanol washing solutions according to the manuscript. Mount the tissue sections onto the object stage and observe the tissues under a microscope.To visualize neutrophils, perform immunohistochemical staining by first baking the paraffin sections for two hours at 78 degrees Celsius. Place the slides in a rack and perform the xylene, ethanol, water, and PBS washes according to the manuscript to rehydrate at room temperature. Then add one drop of permeabilization buffer to cover the tissue.Incubate the sections in a humidity controlled tray at 37 degrees Celsius for 10 minutes. After that, rinse the slides in PBS for three minutes three times. Avoid rinsing the tissue directly.Next, perform heat-induced antigen epitope retrieval. Arrange the slides in a rack. Immerse the slides in the pressure boiler filled with retrieval buffer.Put the pressure boiler in the microwave oven and set the microwave oven at 600 watts and heat the slides for 10 minutes. After boiling, keep the slides in the boiler to cool to 90 degrees Celsius. Take out the slides and rinse them in PBS for three minutes three times.To quench endogenous peroxidase activity, immerse the slides in freshly prepared 3%hydrogen peroxide at room temperature for 15 minutes. Rinse slides in PBS for three minutes three times. Outline a large circle around the sample with a hydrophobic pen.Avoid touching the sample. Add onto the sample 50 to 100 microliters of 3%bovine serum albumin to block and place the samples in a humidity controlled chamber at 37 degrees Celsius for 60 minutes. Then remove the blocking solution.Add 50 microliters of PBS diluted primary antibody to each section quickly. Incubate the slides in a humidity controlled tray at four degrees Celsius overnight. On the second day, take out the tray and let it stand at room temperature for 30 minutes.Then rinse the slides in PBS for three minutes three times. Add 50 microliters of PBS diluted secondary antibodies to the tissues. Incubate slides in a humidity controlled tray at 37 degrees Celsius for 30 minutes.Then rinse the slides in PBS for three minutes three times. Develop in diluted DAB solution for five minutes. Avoid the development of a dark color caused by overreaction of the DAB.Rinse the slides in distilled water. Counterstain the slides in hematoxylin for 10 seconds and rinse the slides in tap water for five minutes. Rinse in acid alcohol super fast differentiation solution for three seconds, then rinse in tap water for 10 minutes.Immerse the slides in the ethanol and xylene washes at room temperature according to the manuscript. Fix the coverslip with mounting solution. Observe the tissue under a microscope.In this study, air pouch experiments were performed to investigate the neutrophil recruitment stimulated by LPS in vivo. The leukocyte subsets in the air pouch exudates were much higher than in the control. Compared with the control group, the adjuvant-induced arthritis group showed significant edema in the paw.The ankle joint diameter increased and the arthritis score rose consistently. Cartilage damage is the representative syndrome of rheumatoid arthritis. CFA challenge induced a large amount of leukocyte infiltration, significant cartilage erosion, and synovial hyperplasia.MPO in any expression levels are representative markers of neutrophil infiltration which were significantly upregulated in the joint section. Make sure that the air is injected into the skin, but not into the muscle. We can also investigate the formation of neutrophil extracellular traps by immunohistochemical staining of the ankle joint tissue sections with anti-p84 or These methods can be used to study other inflammatory diseases such as inflammatory bowel disease.

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JoVE Journal

Biology

11.6K 조회수.  Beijing University of Chinese Medicine. 이 방법은 생체 내 및 시험관에서 정상적인 호중구의 이동뿐만 아니라 마우스 관절염 모델에서 병리학 호중구의 침투를 평가하기위한 세 가지 자주 사용되는 방법을 설명하려고합니다. 우리는이 방법이이 분야의 다른 연구자를 위해 유용 할 수 있다고 생각합니다. 이 프로토콜은 공기 파우치 분석및 보조 유발 관절염을 사용하여 염증 부위의 호중구의 이동 능력을 평가하는...