The authors thank Dr. Huq Muhammad Aminul for providing assistance in reviewing the manuscript.

This study was conducted in conformity with the Declaration of Helsinki and was approved by the institutional review boards of Aichi Medical University (2017-H341, 2019-H137). Written informed consent was obtained from each participant.
1. Reagent preparation
NOTE: To perform the sandwich ELISA assay, the reagents are prepared as described below.
<ol>
	<li>Coating buffer:
	<ol>
		<li>To make a 0.1 mol/L carbonate-bicarbonate buffer, weigh 10.6 g o...

<ol>
	<li>Sil, P., Yoo, D. G., Floyd, M., Gingerich, A., Rada, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+throughput+measurement+of+extracellular+DNA+release+and+quantitative+NET+formation+in+human+neutrophils+in+vitro.">High throughput measurement of extracellular DNA release and quantitative NET formation in human neutrophils in vitro.</a> Journal of Visualized Experiments. (112), e52779 (2016).</li><li>Yoo, D. G., Floyd, M., Winn, M., Moskowitz, S. M., Rada, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NET+formation+induced+by+Pseudomonas+aeruginosa+cystic+fibrosis+isolates+measured+as+release+of+myeloperoxidase-DNA+and+neutrophil+elastase-DNA+complexes.">NET formation induced by Pseudomonas aeruginosa cystic fibrosis isolates measured as release of myeloperoxidase-DNA and neutrophil elastase-DNA complexes.</a> Immunology Letters. 160 (2), 186-194 (2014).</li><li>Brinkmann, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neutrophil+extracellular+traps+kill+bacteria.">Neutrophil extracellular traps kill bacteria.</a> Science. 303 (5663), 1532-1535 (2004).</li><li>Papayannopoulos, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neutrophil+extracellular+traps+in+immunity+and+disease.">Neutrophil extracellular traps in immunity and disease.</a> Nature Reviews Immunology. 18, 134-147 (2018).</li><li>Chamardani, T. M., Amiritavassoli, S. <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+NETosis+for+treatment+purposes:+Friend+or+foe.">Inhibition of NETosis for treatment purposes: Friend or foe.</a> Molecular and Cellular Biochemistry. 477 (3), 673-688 (2022).</li><li>Rao, A. N., Kazzaz, N. M., Knight, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Do+neutrophil+extracellular+traps+contribute+to+the+heightened+risk+of+thrombosis+in+inflammatory+diseases.">Do neutrophil extracellular traps contribute to the heightened risk of thrombosis in inflammatory diseases.</a> World Journal of Cardiology. 7 (12), 829-842 (2015).</li><li>S&#248;rensen, O. E., 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=Neutrophil+extracellular+traps+-+The+dark+side+of+neutrophils.">Neutrophil extracellular traps - The dark side of neutrophils.</a> Journal of Clinical Investigation. 126 (5), 1612-1620 (2016).</li><li>Abrams, S. 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=A+novel+assay+for+neutrophil+extracellular+traps+(NETs)+formation+independently+predicts+disseminated+intravascular+coagulation+and+mortality+in+critically+ill+patients.">A novel assay for neutrophil extracellular traps (NETs) formation independently predicts disseminated intravascular coagulation and mortality in critically ill patients.</a> American Journal of Respiratory and Critical Care Medicine. 200 (7), 869-880 (2019).</li><li>Brinkmann, V., Goosmann, C., K&#252;hn, L. I., 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=Automatic+quantification+of+in+vitro+NET+formation.">Automatic quantification of in vitro NET formation.</a> Frontiers in Immunology. 3, 413 (2012).</li><li>Zhao, W., Fogg, D. K., Kaplan, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+image-based+quantitative+method+for+the+characterization+of+NETosis.">A novel image-based quantitative method for the characterization of NETosis.</a> Journal of Immunological Methods. 423, 104-110 (2015).</li><li>Masuda, 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=NETosis+markers:+Quest+for+specific,+objective,+and+quantitative+markers.">NETosis markers: Quest for specific, objective, and quantitative markers.</a> Clinica Chimica Acta. 459, 89-93 (2016).</li><li>Rada, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neutrophil+extracellular+traps.">Neutrophil extracellular traps.</a> Methods in Molecular Biology. 1982, 517-528 (2019).</li><li>Kano, H., Huq, M. A., Tsuda, M., Noguchi, H., Takeyama, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sandwich+ELISA+for+circulating+myeloperoxidase-+and+neutrophil+elastase-DNA+complexes+released+from+neutrophil+extracellular+traps.">Sandwich ELISA for circulating myeloperoxidase- and neutrophil elastase-DNA complexes released from neutrophil extracellular traps.</a> Advanced Techniques in Biology &amp; Medicine. 5 (1), 1000196 (2016).</li><li>Prevel, R., 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=Plasma+markers+of+neutrophil+extracellular+trap+are+linked+to+survival+but+not+to+pulmonary+embolism+in+COVID-19-related+ARDS+patients.">Plasma markers of neutrophil extracellular trap are linked to survival but not to pulmonary embolism in COVID-19-related ARDS patients.</a> Frontiers in Immunology. 13, 851497 (2022).</li><li>Schechter, M. C., 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=et+al.+extracellular+trap+(NET)+levels+in+human+plasma+are+associated+with+active+TB.">et al. extracellular trap (NET) levels in human plasma are associated with active TB.</a> PLoS One. 12, e0182587 (2017).</li><li>Papayannopoulos, V., Metzler, K. D., Hakkim, A., 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=Neutrophil+elastase+and+myeloperoxidase+regulate+the+formation+of+neutrophil+extracellular+traps.">Neutrophil elastase and myeloperoxidase regulate the formation of neutrophil extracellular traps.</a> Journal of Cell Biology. 191 (3), 677-691 (2010).</li><li>Gupta, S., Chan, W., Zaal, K. J., Kaplan, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+high-throughput+real-time+imaging+technique+to+quantify+NETosis+and+distinguish+mechanisms+of+cell+death+in+human+neutrophils.">A high-throughput real-time imaging technique to quantify NETosis and distinguish mechanisms of cell death in human neutrophils.</a> Journal of Immunology. 200 (2), 869-879 (2018).</li><li>Li, M., Lin, C., Leso, A., Nefedova, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantification+of+citrullinated+histone+H3+bound+DNA+for+detection+of+neutrophil+extracellular+traps.">Quantification of citrullinated histone H3 bound DNA for detection of neutrophil extracellular traps.</a> Cancers. 12 (11), 3424 (2020).</li><li>Th&#229;lin, C., 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=Quantification+of+citrullinated+histones:+Development+of+an+improved+assay+to+reliably+quantify+nucleosomal+H3Cit+in+human+plasma.">Quantification of citrullinated histones: Development of an improved assay to reliably quantify nucleosomal H3Cit in human plasma.</a> Journal of Thrombosis and Haemostasis. 18 (10), 2732-2743 (2020).</li><li>Li, 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=PAD4+is+essential+for+antibacterial+innate+immunity+mediated+by+neutrophil+extracellular+traps.">PAD4 is essential for antibacterial innate immunity mediated by neutrophil extracellular traps.</a> Journal of Experimental Medicine. 207 (9), 1853-1862 (2010).</li><li>Zuo, Y., 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+extracellular+traps+in+COVID-19.">Neutrophil extracellular traps in COVID-19.</a> JCI Insight. 5 (11), e138999 (2020).</li><li>Masso-Silva, J. 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=Increased+peripheral+blood+neutrophil+activation+phenotypes+and+neutrophil+extracellular+trap+formation+in+critically+ill+Coronavirus+disease+2019+(COVID-19)+patients:+A+case+series+and+review+of+the+literature.">Increased peripheral blood neutrophil activation phenotypes and neutrophil extracellular trap formation in critically ill Coronavirus disease 2019 (COVID-19) patients: A case series and review of the literature.</a> Clinical Infectious Diseases. 74 (3), 479-489 (2022).</li><li>Gong, F. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+potential+biomarkers+and+immune+features+of+sepsis+using+bioinformatics+analysis.">Identification of potential biomarkers and immune features of sepsis using bioinformatics analysis.</a> Mediators of Inflammation. 2020, 3432587 (2020).</li><li>Almansa, R., 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=Transcriptomic+correlates+of+organ+failure+extent+in+sepsis.">Transcriptomic correlates of organ failure extent in sepsis.</a> Journal of Infection. 70 (5), 445-456 (2015).</li></ol>

All the data generated and/or analyzed during this study are included in this published article. The authors declare that they have no competing interests.

We have described a sandwich ELISA method in which MPO or NE binds to one site of the capture antibody during the initial incubation of samples containing MPO-DNA or NE-DNA complexes. After washing, the &#34;sandwich&#34; is completed by incubating the samples with a peroxidase-associated anti-DNA monoclonal antibody. After the removal of unbound secondary antibody, the bound peroxidase conjugate is detected by the addition of a chromogenic ABTS peroxidase substrate, which yields a soluble end-product that can be read sp...

This article outlines a method to quantify neutrophil extracellular trap (NET) formation in biological fluids by using sandwich enzyme-linked immunosorbent assay (ELISA) to detect complexes of myeloperoxidase (MPO) and neutrophil elastase (NE) with DNA1,2. NETs are composed of a DNA backbone decorated with antimicrobial proteases originating from neutrophil granules3,4. Both MPO-DNA and NE-DNA complexes are important and specific components of NETs and are released into the extracellular space as breakdown products of NETs3,4. 
Besides their important physiological role in antimicrobial defense3, NETs also have various pathological effects4,5, including the promotion of thrombogenesis6 and the worsening of sepsis7. Accordingly, NETs have been gaining attention recently. Nevertheless, the in vivo quantification of NETs has proven challenging because of the lack of a sensitive, reliable quantitative assay method. 
A few methods are available, including the direct measurement of NETs by fluorescence microscopy8,9 and flow cytometry10 and the indirect measurement of circulating cell-free DNA, nucleosomes, and citrullinated histone H3, but each method has its own advantages and limitations11. Although the immunofluorescence microscopic method is specific to NETs and clearly shows the localization and degree of NET formation, samples are limited to biopsy tissue and secreted materials. Moreover, this method needs to be performed by skilled researchers and requires a long time for results to be obtained. Measuring circulating levels of NET-related components by flow cytometry is easy and provides results quickly; however, the method is not specific to NETs12.
We13 and others1,2 have developed a highly sensitive and reliable assay to measure the circulating NET components, MPO-conjugated or NE-conjugated DNA, in human plasma with a modified ELISA technique that uses specific antibodies for MPO or NE as the capture antibodies and a DNA-specific detection antibody. This assay can also be used ex vivo to identify NET components in cell culture supernatants released by activated neutrophils in response to phorbol 12-myristate 13-acetate (PMA) stimulation.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1-Step Polymorphs</td>
			<td>Accurate Chemical and Scientific Corporation</td>
			<td>AN221725</td>
			<td>Isolation of PMN&#39;s from human blood.</td>
		</tr>
		<tr>
			<td>96-well microtiter plate</td>
			<td>Thermo Fisher Scientific</td>
			<td>467466</td>
			<td>flat bottom</td>
		</tr>
		<tr>
			<td>ABTS buffer solution</td>
			<td>Sigma-Aldrich Merck</td>
			<td>11 204 530 001</td>
			<td>Contains sodium perborate, citric acid, and disodium hydrogen phosphate.&#160;</td>
		</tr>
		<tr>
			<td>ABTS tablets</td>
			<td>Sigma-Aldrich Merck</td>
			<td>11 204 521 001&#160;</td>
			<td>Each tablet contains 5 mg ABTS substrate and 60 mg vehicle substances.</td>
		</tr>
		<tr>
			<td>Adhesive plastic cover, Axygen</td>
			<td>Thermo Fisher Scientific</td>
			<td>14222348</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-MPO antibody</td>
			<td>Sigma-Aldrich Merck</td>
			<td>&#160;07-496-I</td>
			<td>Store at 2-8 &#176;C. stable for 1 year. Host species is rabbit.</td>
		</tr>
		<tr>
			<td>Anti-NE antibody, clone AHN-10</td>
			<td>Sigma-Aldrich Merck</td>
			<td>MABS461</td>
			<td>Store at 2-8 &#176;C. stable for 1 year. Host species is mouse.</td>
		</tr>
		<tr>
			<td>Bovine serum albumin</td>
			<td>Biomedical Science</td>
			<td>BR-220700081</td>
			<td>Albumin from bovine fraction V. Store at 2&#8211;8 &#176;C. stable for 2 year.</td>
		</tr>
		<tr>
			<td>DNase I</td>
			<td>New England BioLabs</td>
			<td>M0303M</td>
			<td>Store at -20 &#176;C</td>
		</tr>
		<tr>
			<td>IgG, rabbit, Isotype Control</td>
			<td>GENETEX, Inc.</td>
			<td>GTX35035</td>
			<td>Store as concentrated solution at 2&#8211;8 &#176;C.</td>
		</tr>
		<tr>
			<td>IgG1, mouse Isotype Control, clone Ci4</td>
			<td>Merck&#160;</td>
			<td>MABC002</td>
			<td>Store as concentrated solution at 2&#8211;8 &#176;C.</td>
		</tr>
		<tr>
			<td>Lithium heparin blood collection tube</td>
			<td>Becton Dickinson and Company</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Microplate mixer</td>
			<td>As one corporation</td>
			<td>NS-P</td>
			<td></td>
		</tr>
		<tr>
			<td>Microplate Reader</td>
			<td>Molecular Devices</td>
			<td>SpectraMax 190&#160;</td>
			<td>Any microplate plate reader capable of reading wavelengths from 405&#8211;490 nm can use.</td>
		</tr>
		<tr>
			<td>Microplate reader application</td>
			<td>Molecular Devices</td>
			<td>SoftMax pro</td>
			<td></td>
		</tr>
		<tr>
			<td>Peroxidase-conjugated anti-DNA antibody, Cell death Detection ELISA</td>
			<td>Roche Diagnostics</td>
			<td>1154467500</td>
			<td>&#160;bottle 2. Store at 2&#8211;8 &#176;C. stable for 1 year.</td>
		</tr>
		<tr>
			<td>Phorbol 12-myristate 13-acetate</td>
			<td>Sigma-Aldrich Merck</td>
			<td>P8139</td>
			<td>Activation of PMN&#39;s from human blood.</td>
		</tr>
		<tr>
			<td>Phosphate buffered solution</td>
			<td>Takara Bio</td>
			<td>T9181</td>
			<td>Store at room temperature. Stable for 6 months.</td>
		</tr>
		<tr>
			<td>SigmaPlot v14.5</td>
			<td>&#160;Systat Software Inc. San Jose, CA, USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium azide</td>
			<td>Fujifilm Wako Chemicals</td>
			<td>190-14901</td>
			<td>Store at room temperature.</td>
		</tr>
		<tr>
			<td>t-Octylphenoxypolyethoxyethanol, Polyethylene glycol tert-octylphenyl ether</td>
			<td>Fujifilm Wako Chemicals</td>
			<td>9002-93-1</td>
			<td>Store at room temperature.</td>
		</tr>
	</tbody>
</table>

quantifying myeloperoxidase-dna and neutrophil elastase-dna complexes from neutrophil extracellular traps by using a modified sandwich elisa

Certain stimuli, such as microorganisms, cause neutrophils to release neutrophil extracellular traps (NETs), which are basically web-like structures composed of DNA with granule proteins, such as myeloperoxidase (MPO) and neutrophil elastase (NE), and cytoplasmic and cytoskeletal proteins. Although interest in NETs has increased recently, no sensitive, reliable assay method is available for measuring NETs in clinical settings. This article describes a modified sandwich enzyme-linked immunosorbent assay to quantitatively measure two components of circulating NETs, MPO-DNA and NE-DNA complexes, which are specific components of NETs and are released into the extracellular space as breakdown products of NETs. The assay uses specific monoclonal antibodies for MPO or NE as the capture antibodies and a DNA-specific detection antibody. MPO or NE binds to one site of the capture antibody during the initial incubation of samples containing MPO-DNA or NE-DNA complexes. This assay shows good linearity and high inter-assay and intra-assay precision. We used it in 16 patients with COVID-19 with accompanying acute respiratory distress syndrome and found that the plasma concentrations of MPO-DNA and NE-DNA were significantly higher than in the plasma obtained from healthy controls. This detection assay is a reliable, highly sensitive, and useful method for investigating the characteristics of NETs in human plasma and culture supernatants.

This method used a sandwich ELISA with anti-MPO, anti-NE, and anti-DNA monoclonal antibodies to measure MPO-associated and NE-associated DNA (Figure 1). In this method, the wells of a microtiter plate were coated with an MPO-specific or NE-specific monoclonal antibody to capture DNA-associated MPO and DNA-associated NE, as well as non-DNA-associated MPO and NE. To calculate the intra-assay coefficient of variability (CV), duplicate measurements were performed within the same plate for 30 sam...

Watch this Scientific Journal Video about Quantifying Myeloperoxidase-DNA and Neutrophil Elastase-DNA Complexes from Neutrophil Extracellular Traps by Using a Modified Sandwich ELISA at JoVE.com

Quantifying Myeloperoxidase-DNA and Neutrophil Elastase-DNA Complexes from Neutrophil Extracellular Traps by Using a Modified Sandwich ELISA

We present a protocol for a modified sandwich enzyme-linked immunosorbent assay technique to quantitatively measure two components of neutrophil extracellular trap remnants, myeloperoxidase conjugated-DNA and neutrophil elastase conjugated-DNA complexes,derived from activated neutrophils.

Certain stimuli, such as microorganisms, cause neutrophils to release neutrophil extracellular traps (NETs), which are basically web-like structures ...

NETs have attracted recent attention, but quantifying NETs in vivo has proven challenging. This protocol provides a desirable, highly sensitive, and valuable method for investigating the characteristics of NETs in clinical settings. This technique should extend to evaluate the severity of sepsis or septic ARDS, acute respiratory distress syndrome.It is widely accepted that regulating dumps or damage-associated molecular patterns is a key to improving the clinical condition of sepsis. The greatest advantage of this method includes the accurate quantification of circulating NET remnants like myeloperoxidase-DNA and neutrophil elastase-DNA in a short time. It is advisable to spin the samples before assay and avoid repeated thawing.It is important to follow the incubation times as given in the protocol. Begin by diluting freshly isolated polymorphonuclear neutrophils to 10, 000 cells per milliliter in phenol red-free RPMI 1640. Sieve them in 35-millimeter culture dishes.To induce neutrophil extracellular traps or NETs, first stimulate the polymorphonuclear neutrophils with 25 nanomolar PMA. Then partially digest the extracellular traps by adding 0.6 micrograms per milliliter of DNase I, and incubate the mixture for 50 minutes at room temperature. Now, add five-millimolar EDTA to stop the DNase activity, and collect the medium containing the synthesized NETs.Centrifuge to remove the cell debris. Collect the supernatants from four healthy controls. Mix store them at minus 80 degrees Celsius for further use.Pipette 100 microliters of diluted anti-myeloperoxidase containing 0.05 micrograms of the antibody into an ELISA plate. Now, cover the plate with an adhesive plastic cover to prevent sample evaporation, and incubate the sample overnight at four degrees Celsius to allow the binding of the capture antibodies. The next day, discard the diluted antibody solution from the wells, and pipette 300 microliters of wash solution into each well.Tap the plate dry on a paper towel to remove the excess PBS. Block each well of the plate with 200 microliters of the blocking buffer. Cover it with an adhesive plastic cover, and obstruct the wells by incubating it.After discarding the blocking solution from the wells and washing the plate three to four times, tap it dry on a paper towel. Next, pipette 25 microliters of plasma into all wells except the blank. And dilute it with 75 microliters of PBS, making the final well volume 100 microliters.Then add 100 microliters of PBS to the blank well. Mix the samples by placing the plate on a shaker for 10 seconds at 250 rpm at room temperature. Add two microliters of 100 full diluted DNase I to all wells, and place the sealed plate on the shaker for 10 seconds to thoroughly mix the samples.Incubate for 15 minutes at room temperature. Add one microliter of 0.5 molar EDTA to each well to stop the DNase reaction. Then place the sealed plate on the shaker for 15 seconds to thoroughly mix the samples.Finally, incubate the plate overnight at four degrees Celsius to allow the protein components of the NETs to attach to the capture antibodies. The next day, discard the solution from the wells. After multiple well washes, pipette 100 microliters of the diluted peroxidase-conjugated anti-DNA detection antibody into each well.Incubate the plate for 1 1/2 hours, and then discard the solution in the wells. After washing the wells thrice, pipette 100 microliters of ABTS substrate solution into each well, and incubate the sealed plate on a shaker in the dark. Stop the reaction by adding 50 microliters of two-molar sulfuric acid.Mix the well contents by carefully tapping the plate sides. Next, connect the microplate reader to the computer and launch the software application. From the status bar, create a new experiment and name it.Then set the plate reading parameters by selecting Absorbance as the read type, Endpoint as the read mode, and two as the wavelengths. Next, set lambda one as 405 nanometers, lambda two as 490 nanometers. Now, select the Off status for both Automix and Blanking while keeping the AutoCalibration as On.Then select Read entire plate under Strips.Finally, set the Column Wavelength Priority with Normal as the Carriage Speed, and then select Off under AutoRead. Place the plate well into the instrument drawer and close it. Click on Read so that the plate is read immediately.Read the absorbance of each well at 405 nanometers, and perform automatic subtraction of the assay medium absorbance from all unknown samples. Reliable standard calibration curves were obtained for both MPO-DNA and NE-DNA when the absorbance values did not exceed 0.93 and 0.9, respectively. The highest OD was obtained when 0.6 micrograms per milliliter of DNase I was applied.The inter-assay variability coefficients for the complexes in healthy controls were 1.871 and 0.987, respectively, while the COVID-19 patients showed variability coefficients of 2.532 and 2.010, respectively. The mean inter-assay variability coefficients for MPO-DNA and NE-DNA were 6.524 and 4.389, respectively. The capture antibodies'specificity to the MPO-DNA and NE-DNA complexes showed that the iso-type control antibodies reacted little to the complexes.The percentage of both complexes was higher in the plasma from patients with COVID-19 relative to the healthy controls. DNase digestion time should be optimized, otherwise excessive digestion will reduce the absorbance.

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Immunology and Infection

2.8K vues.  University of Science and Technology Chittagong (USTC). Les TNE ont récemment attiré l’attention, mais la quantification des TNE in vivo s’est avérée difficile. Ce protocole fournit une méthode souhaitable, très sensible et précieuse pour étudier les caractéristiques des TNE en milieu clinique. Cette technique devrait s’étendre à l’évaluation de la sévérité de la septicémie ou du SDRA septique, du syndrome de détresse respiratoire aiguë.Il est largement admis que la régulation des décharges ou des modèles moléc...