This work was supported by the National Natural Science Foundation of China (82002130), Beijing Natural Science Foundation (7222059)&#160;and the CAMS Innovation Fund for Medical Sciences (2019-I2M-5-026).

Blood samples were obtained from patients with IM (n = 3), healthy EBV carriers (n = 3), and EBV-uninfected children (n = 3). Volunteers were recruited from Beijing Children&#39;s Hospital, Capital Medical University, and all studies were ethically approved. Ethical approval was obtained by the Ethics Committee of Beijing Children&#39;s Hospital, Capital Medical University (Approval Number: [2021]-E-056-Y). Informed consent of patients was waived as the study only used the remaining samples for clinical testing. All data were fully deidentified and anonymized to protect patient privacy.
1. Isolation of PBMCs from peripheral blood
<ol>
	<li>Collect fresh peripheral blood (2 mL) from patients with IM into K3EDTA tubes by standard venipuncture. 
	NOTE: The process needs to be rapid to maintain cell viability.</li>
	<li>Dilute peripheral blood to twofold volume with phosphate-buffered saline (PBS) and layer it on top of human lymphocyte separation medium (density: 1.077 &#177; 0.001 g/mL) in a 15 mL centrifuge tube. 
	NOTE: The volume ratio of blood, PBS, and separation medium was 1:1:1. Add the blood slowly to the separation medium, and centrifuge immediately to avoid blood settling into the separation medium.</li>
	<li>Centrifuge at 800 &#215; g for 20 min at room temperature. Transfer the middle layer (enriched PBMCs) to another 15 mL centrifuge tube. 
	NOTE: After centrifugation, at the bottom of the tube are erythrocytes, the middle layer is the separation medium, the top layer is plasma, and between the plasma layer and the separation liquid layer were the PBMCs (including lymphocytes and monocytes).</li>
	<li>Wash the PBMCs with 10 mL of PBS and centrifuge at 800 &#215; g for 20 min at room temperature; discard the supernatant carefully.</li>
	<li>Repeat the washing and centrifuging (step 1.4) 2 x. Resuspend the PBMCs with 1 mL of PBS in a 1.5 mL microcentrifuge tube and count the cells with a trypan blue-based, automated counter.</li>
</ol>
2. Isolation of CD14&#160;+ monocytes from PBMCs using CD14 microbeads
<ol>
	<li>Prepare a buffer solution containing 0.5% fetal bovine serum (FBS) and 2 mM EDTA in PBS (pH 7.2). Keep the buffer cold (2&#8722;8 &#176;C). 
	NOTE: Degas the buffer before use as air bubbles could block the column. Keep the cells cold to prevent capping of the antibodies on the cell surface and non-specific cell labeling.</li>
	<li>Centrifuge the PBMCs at 300 &#215; g for 10 min at room temperature. Discard the supernatant carefully. Resuspend the cells with 80 &#181;L of the buffer. Add 20 &#181;L of CD14 microbeads to the cell suspension. 
	NOTE: If there are &#8804;107 PBMCs, use the volume indicated above. If there are &#62;107 PBMCs, proportionally increase all reagent volumes and the total volume.</li>
	<li>Mix the CD14 microbeads and the cells well in the 1.5 mL microcentrifuge tube and incubate for 15 min in a 4 &#176;C refrigerator. Wash the PBMCs with 1 mL of buffer and centrifuge at 300 &#215; g for 10 min at room temperature. Discard the supernatant completely. Resuspend the cells with 500 &#181;L of the buffer. 
	NOTE: If there are &#8804;108 PBMCs, use the volume indicated above. If there are &#62;108 PBMCs, proportionally increase the buffer volume.</li>
	<li>Magnetic separation with columns:
	<ol>
		<li>Put the column on the magnetic bead separator, and wash the column with 3 mL of buffer. Add the cell suspension (from step 2.3) to the column.</li>
		<li>Collect the unlabeled cells that pass through the column into a 15 mL centrifuge tube and wash the column with 3 mL of buffer. Wash the column with 3 x 3 mL of buffer. Collect the total effluent in the 15 mL centrifuge tube.</li>
		<li>Place the column in a new 15 mL centrifuge tube. Add 5 mL of buffer to the column. Push the plunger firmly into the column to immediately flush out the magnetically labeled cells into the 15 mL centrifuge tube.</li>
		<li>Centrifuge the magnetically labeled cells at 300 &#215; g for 5 min and remove the supernatant. Resuspend the cells in 500 &#181;L of PBS in a 1.5 mL microcentrifuge tube for use in subsequent transcriptome sequencing.</li>
	</ol>
	</li>
</ol>
3. Separation of lymphocyte populations from PBMCs by fluorescently labeled antibody staining and FACS
<ol>
	<li>Centrifuge the unlabeled cells (step 2.4.2) at 300 &#215; g for 5 min and remove the supernatant. Resuspend the cells in 100 &#181;L of PBS in a 1.5 mL microcentrifuge tube.</li>
	<li>Add 2 &#181;L of each labeled antibody (CD3, CD4, CD8, CD16, CD19, CD56) to the 100 &#181;L of cell suspension (the volumes and conjugated fluorophore information of antibodies are shown in Table 1), incubate on ice for 30 min, and protect from light.</li>
	<li>Wash the cells 2 x by adding 1 mL of PBS and centrifuging at 300 &#215; g for 5 min at room temperature. Resuspend the cells in 500 &#181;L of PBS in the 1.5 mL microcentrifuge tube. Vortex the cell suspension gently before acquiring data on a flow cell sorter cytometer.</li>
</ol>
4. Flow cytometry parameter setting
<ol>
	<li>Take 100 &#181;L of the cell suspension (see section 1) in 1.5 mL microcentrifuge tubes as required, and set up a negative control sample, a CD3 single-staining sample, a CD4 single-staining sample, a CD8 single-staining sample, a CD19 single-staining sample, and a CD56/CD16 staining sample.</li>
	<li>Add 2 &#181;L of the corresponding fluorescently labeled antibody per 100 &#181;L of the cell suspension and vortex. Incubate on ice for 30 min in the dark. Centrifuge for 5 min at 300 &#215; g and aspirate the supernatant. Resuspend the pellets with 500 &#181;L of PBS and vortex.</li>
	<li>Commission the sorting stream and delay the droplets using the fluorescent beads as follows:
	<ol>
		<li>Open the cell sorting system, run the power-on program, install the 85 &#181;m nozzle, and open the sorting stream. Set the sorting voltage to 4,500 V, and the Freq to 47.</li>
		<li>Adjust the parameters mainly by adjusting the main flow droplet breakpoint and the droplet delay according to the manufacturer&#39;s instructions12. Set up the first droplet breakpoint position (Drop1) to 275, and the Gap to 8 in the Breakoff window. Turn on the Sweet Spot automatic sorting mode to allow the cytometry to automatically determine the droplet amplitude value to stabilize the stream.</li>
		<li>Adjust the droplet delay to 30.31 in the Side Stream window by loading the fluorescent beads, ensuring that the beads achieve a side flow deflection of &#62;99% in either initial or fine tune mode.</li>
	</ol>
	</li>
	<li>Refer to the gating strategy shown in Figure 1 to perform gating as follows:
	<ol>
		<li>Using a forward scatter-area (FSC-A)/side scatter-area (SSC-A) dot plot, draw the polygon gate (P1) to identify the intact lymphocyte population.</li>
		<li>Using an FSC-A/FSC-height (FSC-H) dot plot, draw the polygon gate (P2) to identify the single cells and exclude doublets (Figure 1A).</li>
		<li>Using a CD19 FITC-A/CD3 PerCP-Cy5.5-A dot plot, draw the rectangular gate (P3) to select CD3+ T cells and CD19+ B cells (Figure 1A,B).</li>
		<li>Using a CD4 APC-Cy7-A/CD8 PE-A dot plot, draw a rectangular gate to select CD4+ T cells and CD8+ T cells (cells with a high fluorescence for these markers, respectively).</li>
		<li>Using a CD56/CD16 APC-A/SSC-A dot plot, draw a rectangular gate to select CD56+/CD16+ NK cells (Figure 1C).</li>
	</ol>
	</li>
	<li>Adjust instrumental parameters using the negative control sample:
	<ol>
		<li>Install the negative control tube onto the loading port and click Load in the Acquisition Dashboard. Select the Cytometer Settings in the software.</li>
		<li>In the Inspector window, click the Parameters tab, and adjust the voltages of FSC, SSC, and different fluorescent dyes; FSC: 231, SSC: 512, PE: 549, APC: 615, APC-Cyanine 7: 824, FITC: 555, PerCP-Cyanine 5.5: 663.</li>
	</ol>
	</li>
	<li>Adjust compensation using the single-stained samples13.
	<ol>
		<li>Load the single-stained tubes onto the cytometry sequentially andselect Cytometer Settings in the software. Click the Compensation tab to adjust the compensation. 
		&#8203;NOTE: The compensation reference of flow cytometry is shown in Table 2.</li>
	</ol>
	</li>
</ol>
5. Cell sorting and collecting data&#160;&#160;via flow cytometry
<ol>
	<li>Vortex the cell suspension (separated PBMCs according to sections 1&#8211;3) briefly to resuspend the cells before loading the tube into the cytometer. Keep the remaining tubes on ice.</li>
	<li>Add 200 &#181;L of FBS to four collection flow tubes to avoid sticking of the sorted cells to the tube wall and place them in the cytometer collection chamber.</li>
	<li>Collect CD3+CD4+ T cells, CD3+CD8+ T cells, CD3&#8722;CD19+ B cells, and CD3&#8722; CD56+/CD16+ NK cells separately from the sample of a patient with IM in the four flow tubes (Figure 2A).</li>
	<li>Centrifuge the separated cells at 300 &#215; g for 5 min and remove the supernatant. Add 200 &#181;L of RNA isolation reagent to the cells for transcriptome sequencing.</li>
	<li>Separate the immune cell subpopulations of samples from healthy EBV carriers and EBV-uninfected children according to the above steps (Figure 2B, C).</li>
</ol>

<ol>
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H., 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=Behavioral,+virology,+and+immunologic+factors+associated+with+acquisition+and+severity+of+primary+Epstein-Barr+virus+infection+in+university+students.">Behavioral, virology, and immunologic factors associated with acquisition and severity of primary Epstein-Barr virus infection in university students.</a> Journal of Infectious Diseases. 207 (1), 80-88 (2013).</li><li>Luzuriaga, K., Sullivan, J. 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Series B: Biological Sciences. 372 (1732), 20160270 (2017).</li><li>Zhong, H., 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=Whole+transcriptome+profiling+reveals+major+cell+types+in+the+cellular+immune+response+against+acute+and+chronic+active+Epstein-Barr+virus+infection.">Whole transcriptome profiling reveals major cell types in the cellular immune response against acute and chronic active Epstein-Barr virus infection.</a> Scientific Reports. 7 (1), 17775 (2017).</li><li>Fedyanina, O. 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(143), e58431 (2019).</li><li>Djaoud, Z., 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=Two+alternate+strategies+for+innate+immunity+to+Epstein-Barr+virus:+One+using+NK+cells+and+the+other+NK+cells+and+gammadelta+T+cells.">Two alternate strategies for innate immunity to Epstein-Barr virus: One using NK cells and the other NK cells and gammadelta T cells.</a> Journal of Experimental Medicine. 214 (6), 1827-1841 (2017).</li><li>Nakid-Cordero, C., Baron, M., Guihot, A., Vieillard, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Natural+killer+cells+in+post-transplant+lymphoproliferative+disorders.">Natural killer cells in post-transplant lymphoproliferative disorders.</a> Cancers. 13 (8), 1836 (2021).</li><li>Forrest, C., Hislop, A. D., Rickinson, A. B., Zuo, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proteome-wide+analysis+of+CD8++T+cell+responses+to+EBV+reveals+differences+between+primary+and+persistent+infection.">Proteome-wide analysis of CD8+ T cell responses to EBV reveals differences between primary and persistent infection.</a> PLoS Pathogens. 14 (9), 1007110 (2018).</li><li>Zamai, 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=Understanding+the+Synergy+of+NKp46+and+co-activating+signals+in+various+NK+cell+subpopulations:+paving+the+way+for+more+successful+NK-cell-based+immunotherapy.">Understanding the Synergy of NKp46 and co-activating signals in various NK cell subpopulations: paving the way for more successful NK-cell-based immunotherapy.</a> Cells. 9 (3), 753 (2020).</li><li>Lam, J. K. 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=Emergence+of+CD4++and+CD8++polyfunctional+T+cell+responses+against+immunodominant+lytic+and+latent+EBV+antigens+in+children+with+primary+EBV+infection.">Emergence of CD4+ and CD8+ polyfunctional T cell responses against immunodominant lytic and latent EBV antigens in children with primary EBV infection.</a> Frontiers In Microbiology. 9, 416 (2018).</li><li>Choi, I. 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=Signaling+by+the+Epstein-Barr+virus+LMP1+protein+induces+potent+cytotoxic+CD4(+)+and+CD8(+)+T+cell+responses.">Signaling by the Epstein-Barr virus LMP1 protein induces potent cytotoxic CD4(+) and CD8(+) T cell responses.</a> Proceedings of the National Academy of Sciences. 115 (4), 686-695 (2018).</li></ol>

The authors declare no conflicts of interest.

This protocol represents an efficient way to sort peripheral blood immune cell subpopulations. In this study, venous blood samples from patients with IM, healthy EBV carriers, and EBV-uninfected children were selected as the research objective. This work using the peripheral blood of patients of IM mainly focuses on analyzing and determining the proportions of different cell subsets through multi-color flow cytometry. Transcriptome sequencing is mainly used for the detection and analysis of a certain subpopulation of lym...

Epstein&#8211;Barr virus (EBV), a &#947;-herpesvirus also known as human herpes virus type 4, is ubiquitous in the human population and establishes lifelong latent infection in more than 90% of the adult population1. Most EBV primary infection occurs during childhood and adolescence, with a fraction of patients manifesting with infectious mononucleosis (IM)2, showing characteristic immunopathology, including an activated immune response with CD8+ T cells in blood and a transient proliferation of EBV-infected B cells in the oropharynx3. The course of IM may last for 2&#8211;6 weeks and the majority of the patients recover well4. However, some individuals develop persistent or recurrent IM-like symptoms with high morbidity and mortality, which is classified as chronic active EBV infection (CAEBV)5. In addition, EBV is an important oncogenic virus, which is closely related to a variety of malignancies, including epithelioid and lymphoid malignancies such asnasopharyngeal carcinoma, Burkitt&#39;s lymphoma, Hodgkin&#39;s lymphoma (HL), and T/NK cell lymphoma6. Although EBV has been studied for over 50 years, its pathogenesis and the mechanism by which it induces the proliferation of lymphocytes have not been fully elucidated.
Several studies have investigated the molecular signatures for the immunopathology of EBV infection by transcriptome sequencing. Zhong et al. analyzed whole-transcriptome profiling of peripheral blood mononuclear cells (PBMCs) from Chinese children with IM or CAEBV to find that CD8+ T cell expansion was predominantly found in the IM group7, suggesting that CD8+ T cells may play a major role in IM. Similarly, another study found lower proportions of EBV-specific cytotoxic T and CD19+ B cells and higher percentages of CD8+&#160;T cells in patients with IM caused by primary EBV infection than in patients with IM caused both by EBV reactivation and other agents8. B cells are first involved in IM because EBV receptors are presented on their surface. Al Tabaa et al. found that B cells were polyclonally activated and differentiated intoplasmablasts (CD19+, CD27+ and CD20&#8722;, and CD138&#8722; cells) and plasma cells (CD19+, CD27+ and CD20&#8722;, and CD138+) during IM9. Moreover, Zhong et al. found that&#160;monocyte markers CD14 and CD64 were upregulated in CAEBV, suggesting that monocytes may play an important role in the cellular immune response of CAEBV through antibody-dependent cellular cytotoxicity (ADCC) and hyperactive phagocytosis7. Alka&#160;et al. characterized the transcriptome of MACS sorted CD56dim CD16+ NK cells from four patients of IM or HL and found that NK cells from both IM and HL had downregulated innate immunity and chemokine signaling genes, which could be responsible for the hyporesponsiveness of NK cells10. In addition, Greenough et al. analyzed gene expression of sorted CD8+ T cells from 10 PBMCs of individuals with IM. They reported that a large proportion of CD8+ T cells in IM were virus-specific, activated, dividing, and primed to exert effector activities11. Both T cell-mediated, EBV-specific responses, and NK cell-mediated, nonspecific responses play essential roles during primary EBV infection. However, these studies only investigated the transcriptome results of the diverse mixture of immune cells or only a certain subpopulation of lymphocytes, which is not sufficient for the comprehensive comparison of the molecular characteristics and functions of different immune cell subpopulations in children with IM at the same disease state.
This paper describes a method that combines immunomagnetic beads and fluorescence-activated cell sorting (FACS) to isolate and analyze defined immune cell subpopulations of PBMCs (monocytes, CD4+ T cells, CD8+ T cells, B cells, and NK cells). Using this method, magnetic and fluorescently labeled cells can be purified using a magnetic separator and FACS or analyzed by flow cytometry. RNA can be extracted from the purified cells for transcriptome sequencing. This method will enable the characterization and gene expression of different immune cells in the same states of disease of individuals with IM, which will expand our understanding of the immunopathology of EBV infection.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>APC anti-human CD16</td>
			<td>Biolegend</td>
			<td>302012</td>
			<td>Fluorescent antibody&#160;</td>
		</tr>
		<tr>
			<td>APC anti-human CD56 (NCAM)</td>
			<td>Biolegend</td>
			<td>362504</td>
			<td>Fluorescent antibody&#160;</td>
		</tr>
		<tr>
			<td>APC/Cyanine7 anti-human CD4</td>
			<td>Biolegend</td>
			<td>344616</td>
			<td>Fluorescent antibody&#160;</td>
		</tr>
		<tr>
			<td>Automated cell counter</td>
			<td>BIO RAD</td>
			<td>TC20</td>
			<td>Cell count</td>
		</tr>
		<tr>
			<td>BD FACSAria fluorescence-activated&#160;flow&#160;cell&#160;sorter-cytometer (BD FACSAria II)</td>
			<td>Becton, Dickinson and Company</td>
			<td>644832</td>
			<td>Cell sort</td>
		</tr>
		<tr>
			<td>CD14 MicroBeads, human</td>
			<td>Miltenyi Biotec</td>
			<td>130-050-201</td>
			<td>microbeads</td>
		</tr>
		<tr>
			<td>Cell ctng slides</td>
			<td>BIO RAD</td>
			<td>1450016</td>
			<td>Cell count</td>
		</tr>
		<tr>
			<td>Centrifuge tubes</td>
			<td>Falcon</td>
			<td>35209715</td>
			<td>15 mL centrifuge tube</td>
		</tr>
		<tr>
			<td>EDTA (&#8805;99%, BioPremium)</td>
			<td>Beyotime</td>
			<td>ST1303</td>
			<td>EDTA</td>
		</tr>
		<tr>
			<td>Ethylene diamine tetra acetic acid (EDTA) anticoagulant tubes</td>
			<td>Becton, Dickinson and Company</td>
			<td>&#160;367862&#160;</td>
			<td>EDTA anticoagulant tubes</td>
		</tr>
		<tr>
			<td>FITC anti-human CD19</td>
			<td>Biolegend</td>
			<td>302206</td>
			<td>Fluorescent antibody&#160;</td>
		</tr>
		<tr>
			<td>Gibco Fetal Bovine Serum</td>
			<td>Thermo Fisher Scientific</td>
			<td>16000-044</td>
			<td>Fetal Bovine Serum</td>
		</tr>
		<tr>
			<td>&#160;High-speed&#160;centrifuge</td>
			<td>Sigma</td>
			<td>&#160;3K15</td>
			<td>Cell centrifugation for 15 mL centrifuge tube</td>
		</tr>
		<tr>
			<td>&#160;High-speed&#160;centrifuge</td>
			<td>Eppendorf</td>
			<td>5424R</td>
			<td>Cell centrifugation for 1.5 mL Eppendorf (EP) tube</td>
		</tr>
		<tr>
			<td>Human lymphocyte separation medium</td>
			<td>Dakewe</td>
			<td>DKW-KLSH-0100</td>
			<td>Ficoll-Paque</td>
		</tr>
		<tr>
			<td>LS&#160;Separation&#160;columns</td>
			<td>Miltenyi Biotec</td>
			<td>130-042-401</td>
			<td>Separation&#160;columns</td>
		</tr>
		<tr>
			<td>Microcentrifuge tubes</td>
			<td>Axygen</td>
			<td>MCT-150-C</td>
			<td>1.5 mL microcentrifuge tube</td>
		</tr>
		<tr>
			<td>MidiMACS Separator</td>
			<td>Miltenyi Biotec</td>
			<td>130-042-302</td>
			<td>Magnetic bead separator</td>
		</tr>
		<tr>
			<td>PE anti-human CD8</td>
			<td>Biolegend</td>
			<td>344706</td>
			<td>Fluorescent antibody&#160;</td>
		</tr>
		<tr>
			<td>PerCP/Cyanine5.5 anti-human CD3</td>
			<td>Biolegend</td>
			<td>344808</td>
			<td>Fluorescent antibody&#160;</td>
		</tr>
		<tr>
			<td>Phosphate Buffered Saline (PBS)</td>
			<td>BI</td>
			<td>02-024-1ACS</td>
			<td>PBS</td>
		</tr>
		<tr>
			<td>Polystyrene round bottom tubes</td>
			<td>Falcon</td>
			<td>352235</td>
			<td>5 mL tube for FACS flow cytometer</td>
		</tr>
		<tr>
			<td>TRIzol reagent</td>
			<td>Ambion</td>
			<td>15596024</td>
			<td>Lyse cells for RNA extraction</td>
		</tr>
		<tr>
			<td>Trypan Blue Staining Cell Viability Assay Kit</td>
			<td>Beyotime</td>
			<td>C0011</td>
			<td>Trypan Blue Staining</td>
		</tr>
	</tbody>
</table>

separation of immune cell subpopulations in peripheral blood samples from children with infectious mononucleosis

Infectious mononucleosis (IM) is an acute syndrome mostly associated with primary Epstein&#8211;Barr virus (EBV) infection. The main clinical symptoms include irregular fever, lymphadenopathy, and significantly increased lymphocytes in peripheral blood. The pathogenic mechanism of IM is still unclear; there is no effective treatment method for it, with mainly symptomatic therapies being available. The main question in EBV immunobiology is why only a small subset of infected individuals shows severe clinical symptoms and even develop EBV-associated malignancies, whilemost individuals are asymptomatic for life with the virus.
B cells are first involved in IM because EBV receptors are presented on their surface. Natural killer (NK) cells are cytotoxic innate lymphocytes that are important for killing EBV-infected cells. The proportion of CD4+ T cells decreases while that of CD8+ T cells expands dramatically during acute EBV infection, and the persistence of CD8+ T cells is important for lifelong control of IM. Those immune cells play important roles in IM, and their functions need to be identified separately. For this purpose, monocytes are separated first from peripheral blood mononuclear cells (PBMCs) of IM individuals using CD14 microbeads, a column, and a magnetic separator.
The remaining PBMCs are stained with peridinin-chlorophyll-protein (PerCP)/Cyanine 5.5 anti-CD3, allophycocyanin (APC)/Cyanine 7 anti-CD4, phycoerythrin (PE) anti-CD8, fluorescein isothiocyanate (FITC) anti-CD19, APC anti-CD56, and APC anti-CD16 antibodies to sort CD4+ T cells, CD8+ T cells, B cells, and NK cells using a flow cytometer. Furthermore, transcriptome sequencing of five subpopulations was performed to explore their functions and pathogenic mechanisms in IM.

Reference of the gating strategy 
The gating strategy used to sort the four lymphocyte subpopulations is shown in Figure 1. Briefly, lymphocytes are selected (P1) on a dot plot showing the granulosity (SSC-A) versus size (FSC-A). Then, single cells are selected (P2) on a dot plot showing the size (FSC-A) versus forward scatter (FSC-H), while doublet cells are excluded. CD3+ T cells (P3) and CD19+ B cells (Figure 1B) ar...

Watch this Scientific Journal Video about Separation of Immune Cell Subpopulations in Peripheral Blood Samples from Children with Infectious Mononucleosis at JoVE.com

Separation of Immune Cell Subpopulations in Peripheral Blood Samples from Children with Infectious Mononucleosis

We describe a method combining immunomagnetic beads and fluorescence-activated cell sorting to isolate and analyze defined immune cell subpopulations of peripheral blood mononuclear cells (monocytes, CD4+ T cells, CD8+ T cells, B cells, and natural killer cells). Using this method, magnetic and fluorescently labeled cells can be purified and analyzed.

Infectious mononucleosis (IM) is an acute syndrome mostly associated with primary Epstein&#8211;Barr virus (EBV) infection. The main clinical symptoms ...

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Research

JoVE Journal

Immunology and Infection

2.3K Views.  Capital Medical University, National Center for Children's Health. We describe a method combining immunomagnetic beads and fluorescence-activated cell sorting to isolate and analyze defined immune cell subpopulations of peripheral blood mononuclear cells (monocytes, CD4+ T cells, CD8+ T cells, B cells, and natural killer cells). Using this method, magnetic and fluorescently labeled cells can be purified and analyzed.

Video: Separation of Immune Cell Subpopulations in Peripheral Blood Samples from Children with Infectious Mononucleosis

Enumeration of Major Peripheral Blood Leukocyte Populations for Multicenter Clinical Trials Using a Whole Blood Phenotyping Assay

Cryopreservation of peripheral blood leukocytes is widely used to preserve cells for immune response evaluations in clinical trials and offers many advantages for ease and standardization of immunological assessments, but detrimental effects of this process have been observed on some cell subsets, such as granulocytes, B cells, and dendritic cells 1-3. Assaying fresh leukocytes gives a more accurate picture of the in vivo state of the cells, but is often difficult to perform in the context of large clinical trials. Fresh cell assays are dependent upon volunteer commitments and timeframes and, if time-consuming, their application can be impractical due to the working hours required of laboratory personnel. In addition, when trials are conducted at multiple centers, laboratories with the resources and training necessary to perform the assays may not be located in sufficient proximity to clinical sites. To address these issues, we have developed an 11-color antibody staining panel that can be used with Trucount tubes (Becton Dickinson; San Jose, CA) to phenotype and enumerate the major leukocyte populations within the peripheral blood, yielding more robust cell-type specific information than assays such as a complete blood count (CBC) or assays with commercially-available panels designed for Trucount tubes that stain for only a few cell types. The staining procedure is simple, requires only 100 &mu;l of fresh whole blood, and takes approximately 45 minutes, making it feasible for standard blood-processing labs to perform. It is adapted from the BD Trucount tube technical data sheet (<a href="http://www.bdbiosciences.com/external_files/is/doc/tds/Package_Inserts_CE/live/web_enabled/23-3483-06_PI_Trucount tubes_CE_EN.pdf" target="_blank">version 8/2010</a>). The staining antibody cocktail can be prepared in advance in bulk at a central assay laboratory and shipped to the site processing labs. Stained tubes can be fixed and frozen for shipment to the central assay laboratory for multicolor flow cytometry analysis. The data generated from this staining panel can be used to track changes in leukocyte concentrations over time in relation to intervention and could easily be further developed to assess activation states of specific cell types of interest. In this report, we demonstrate the procedure used by blood-processing lab technicians to perform staining on fresh whole blood and the steps to analyze these stained samples at a central assay laboratory supporting a multicenter clinical trial. The video details the procedure as it is performed in the context of a clinical trial blood draw in the HIV Vaccine Trials Network (HVTN).

In this report, we demonstrate the staining and analysis steps of a phenotyping assay performed on fresh whole blood to enumerate major innate and adaptive leukocyte populations. We emphasize considerations for performing these procedures in the context of a multicenter clinical trial.

Cryopreservation of peripheral blood leukocytes is widely used to preserve cells for immune response evaluations in clinical trials and offers many ...

Isolation of Precursor B-cell Subsets from Umbilical Cord Blood

Umbilical cord blood is highly enriched for hematopoietic progenitor cells at different lineage commitment stages. We have developed a protocol for isolating precursor B-cells at four different stages of differentiation. Because genes are expressed and epigenetic modifications occur in a tissue specific manner, it is vital to discriminate between tissues and cell types in order to be able to identify alterations in the genome and the epigenome that may lead to the development of disease. This method can be adapted to any type of cell present in umbilical cord blood at any stage of differentiation.	
This method comprises 4 main steps. First, mononuclear cells are separated by density centrifugation. Second, B-cells are enriched using biotin conjugated antibodies that recognize and remove non B-cells from the mononuclear cells. Third the B-cells are fluorescently labeled with cell surface protein antibodies specific to individual stages of B-cell development. Finally, the fluorescently labeled cells are sorted and individual populations are recovered. The recovered cells are of sufficient quantity and quality to be utilized in downstream nucleic acid assays.

Here we describe a protocol for isolating subsets of precursor B-cells from umbilical cord blood. A sufficient quantity and quality of nucleic acids may be extracted from the cells and used in subsequent assays utilizing DNA or RNA.

Umbilical cord blood is highly enriched for hematopoietic progenitor cells at different lineage commitment stages. We have developed a protocol for ...

An In vitro Model to Study Immune Responses of Human Peripheral Blood Mononuclear Cells to Human Respiratory Syncytial Virus Infection

Human respiratory syncytial virus (HRSV) infections present a broad spectrum of disease severity, ranging from mild infections to life-threatening bronchiolitis. An important part of the pathogenesis of severe disease is an enhanced immune response leading to immunopathology.	Here, we describe a protocol used to investigate the immune response of human immune cells to an HRSV infection. First, we describe methods used for culturing, purification and quantification of HRSV. Subsequently, we describe a human in vitro model in which peripheral blood mononuclear cells (PBMCs) are stimulated with live HRSV. This model system can be used to study multiple parameters that may contribute to disease severity, including the innate and adaptive immune response. These responses can be measured at the transcriptional and translational level. Moreover, viral infection of cells can easily be measured using flow cytometry. Taken together, stimulation of PBMC with live HRSV provides a fast and reproducible model system to examine mechanisms involved in HRSV-induced disease.

An In vitro Model to Study Immune Responses of Human Peripheral Blood Mononuclear Cells to Human Respiratory Syncytial Virus Infection

Human respiratory syncytial virus (HRSV) can cause severe bronchiolitis in young infants. Part of the pathogenesis of severe HRSV disease is caused by the host immune response. Stimulation of primary human immune cells with HRSV provides a fast and reproducible model system to study activation of inflammatory pathways and infection.

Human respiratory syncytial  virus (HRSV) infections present a broad spectrum of disease severity, ranging  from mild infections to life-threatening ...

Detection of Fluorescent Nanoparticle Interactions with Primary Immune Cell Subpopulations by Flow Cytometry

Engineered nanoparticles are endowed with very promising properties for therapeutic and diagnostic purposes. This work describes a fast and reliable method of analysis by flow cytometry to study nanoparticle interaction with immune cells. Primary immune cells can be easily purified from human or mouse tissues by antibody-mediated magnetic isolation. In the first instance, the different cell populations running in a flow cytometer can be distinguished by the forward-scattered light (FSC), which is proportional to cell size, and the side-scattered light (SSC), related to cell internal complexity. Furthermore, fluorescently labeled antibodies against specific cell surface receptors permit the identification of several subpopulations within the same sample. Often, all these features vary when cells are boosted by external stimuli that change their physiological and morphological state. Here, 50 nm FITC-SiO2 nanoparticles are used as a model to identify the internalization of nanostructured materials in human blood immune cells. The cell fluorescence and side-scattered light increase after incubation with nanoparticles allowed us to define time and concentration dependence of nanoparticle-cell interaction. Moreover, such protocol can be extended to investigate Rhodamine-SiO2 nanoparticle interaction with primary microglia, the central nervous system resident immune cells, isolated from mutant mice that specifically express the Green Fluorescent Protein (GFP) in the monocyte/macrophage lineage. Finally, flow cytometry data related to nanoparticle internalization into the cells have been confirmed by confocal microscopy.

Analysis of nanoparticle interaction with defined subpopulations of immune cells by flow cytometry.

Engineered nanoparticles are endowed with very promising properties for therapeutic and diagnostic purposes. This work describes a fast and reliable ...

Rapid Identification of Gram Negative Bacteria from Blood Culture Broth Using MALDI-TOF Mass Spectrometry

An important role of the clinical microbiology laboratory is to provide rapid identification of bacteria causing bloodstream infection. Traditional identification requires the sub-culture of signaled blood culture broth with identification available only after colonies on solid agar have matured. MALDI-TOF MS is a reliable, rapid method for identification of the majority of clinically relevant bacteria when applied to colonies on solid media. The application of MALDI-TOF MS directly to blood culture broth is an attractive approach as it has potential to accelerate species identification of bacteria and improve clinical management. However, an important problem to overcome is the pre-analysis removal of interfering resins, proteins and hemoglobin&#160;contained in blood culture specimens which, if not removed, interfere with the MS spectra and can result in insufficient or low discrimination identification scores. In addition it is necessary to concentrate bacteria to develop spectra of sufficient quality. The presented method describes the concentration, purification, and extraction of Gram negative bacteria allowing for the early identification of bacteria from a signaled blood culture broth.

The application of matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry (MS) directly to blood culture broth expedites the identification of bacteria. The presented method is a rapid and reliable method for identification of Gram negative bacteria directly from blood culture broth.

An important role of the clinical microbiology laboratory is to provide rapid identification of bacteria causing bloodstream infection. Traditional ...

Detecting Glycogen in Peripheral Blood Mononuclear Cells with Periodic Acid Schiff Staining

Periodic acid Schiff (PAS) staining is an immunohistochemical technique used on muscle biopsies and as a diagnostic tool for blood samples. Polysaccharides such as glycogen, glycoproteins, and glycolipids stain bright magenta making it easy to enumerate positive and negative cells within the tissue. In muscle cells PAS staining is used to determine the glycogen content in different types of muscle cells, while in blood cell samples PAS staining has been explored as a diagnostic tool for a variety of conditions. Blood contains a proportion of white blood cells that belong to the immune system. The notion that cells of the immune system possess glycogen and use it as an energy source has not been widely explored. Here, we describe an adapted version of the PAS staining protocol that can be applied on peripheral blood mononuclear immune cells from human venous blood. Small cells with PAS-positive granules and larger cells with diffuse PAS staining were observed. Treatment of samples with amylase abrogates these patterns confirming the specificity of the stain. An alternate technique based on enzymatic digestion confirmed the presence and amount of glycogen in the samples. This protocol is useful for hematologists or immunologists studying polysaccharide content in blood-derived lymphocytes.

Periodic acid Schiff staining is a technique that visualizes the polysaccharide content of tissues. This article demonstrates periodic acid Schiff staining protocol adapted for use on peripheral blood mononuclear cells purified from human venous blood. Such samples are enriched for lymphocytes and other white blood cells of the immune system.

Periodic acid Schiff (PAS) staining is an immunohistochemical technique used on muscle biopsies and as a diagnostic tool for blood samples. ...

Generation of Human Alloantigen-specific T Cells from Peripheral Blood

The study of human T lymphocyte biology often involves examination of responses to activating ligands. T cells recognize and respond to processed peptide antigens presented by MHC (human ortholog HLA) molecules through the T cell receptor (TCR) in a highly sensitive and specific manner. While the primary function of T cells is to mediate protective immune responses to foreign antigens presented by self-MHC, T cells respond robustly to antigenic differences in allogeneic tissues. T cell responses to alloantigens can be described as either direct or indirect alloreactivity. In alloreactivity, the T cell responds through highly specific recognition of both the presented peptide and the MHC molecule. The robust oligoclonal response of T cells to allogeneic stimulation reflects the large number of potentially stimulatory alloantigens present in allogeneic tissues. While the breadth of alloreactive T cell responses is an important factor in initiating and mediating the pathology associated with biologically-relevant alloreactive responses such as graft versus host disease and allograft rejection, it can preclude analysis of T cell responses to allogeneic ligands. To this end, this protocol describes a method for generating alloreactive T cells from naive human peripheral blood leukocytes (PBL) that respond to known peptide-MHC (pMHC) alloantigens. The protocol applies pMHC multimer labeling, magnetic bead enrichment and flow cytometry to single cell in vitro culture methods for the generation of alloantigen-specific T cell clones. This enables studies of the biochemistry and function of T cells responding to allogeneic stimulation.

This article describes a method for the generation and propagation of human T cell clones that specifically respond to a defined alloantigen. This protocol can be adapted for cloning human T cells specific for a variety of peptide-MHC ligands.

The study of human T lymphocyte biology often involves examination of responses to activating ligands. T cells recognize and respond to processed peptide ...

A Semi-automated Approach to Preparing Antibody Cocktails for Immunophenotypic Analysis of Human Peripheral Blood

Immunophenotyping of peripheral blood by flow cytometry determines changes in the frequency and activation status of peripheral leukocytes during disease and treatment. It has the potential to predict therapeutic efficacy and identify novel therapeutic targets. Whole blood staining utilizes unmanipulated blood, which minimizes artifacts that can occur during sample preparation. However, whole blood staining must also be done on freshly collected blood to ensure the integrity of the sample. Additionally, it is best to prepare antibody cocktails on the same day to avoid potential instability of tandem-dyes and prevent reagent interaction between brilliant violet dyes. Therefore, whole blood staining requires careful standardization to control for intra and inter-experimental variability.
Here, we report deployment of an automated liquid handler equipped with a two-dimensional (2D) barcode reader into a standard process of making antibody cocktails for flow cytometry. Antibodies were transferred into 2D barcoded tubes arranged in a 96 well format and their contents compiled in a database. The liquid handler could then locate the source antibody vials by referencing antibody names within the database. Our method eliminated tedious coordination for positioning of source antibody tubes. It provided versatility allowing the user to easily change any number of details in the antibody dispensing process such as specific antibody to use, volume, and destination by modifying the database without rewriting the scripting in the software method for each assay.
A proof of concept experiment achieved outstanding inter and intra- assay precision, demonstrated by replicate preparation of an 11-color, 17-antibody flow cytometry assay. These methodologies increased overall throughput for flow cytometry assays and facilitated daily preparation of the complex antibody cocktails required for the detailed phenotypic characterization of freshly collected anticoagulated peripheral blood.

Whole blood Immunophenotyping is indispensable for monitoring the human immune system. However, the number of reagents required and the instability of specific fluorochromes in premixed cocktails necessitates daily reagent preparation. Here we show that semi-automated preparation of staining antibody cocktail helps establish reliable immunophenotyping by minimizing variability in reagent dispensing.

Immunophenotyping of peripheral blood by flow cytometry determines changes in the frequency and activation status of peripheral leukocytes during disease ...

Isolating Lymphocytes from the Mouse Small Intestinal Immune System

The intestinal immune system plays an essential role in maintaining the barrier function of the gastrointestinal tract by generating tolerant responses to dietary antigens and commensal bacteria while mounting effective immune responses to enteropathogenic microbes. In addition, it has become clear that local intestinal immunity has a profound impact on distant and systemic immunity. Therefore, it is important to study how an intestinal immune response is induced and what the immunologic outcome of the response is. Here, a detailed protocol is described for the isolation of lymphocytes from small intestine inductive sites like the gut-associated lymphoid tissue Peyer&#39;s patches and the draining mesenteric lymph nodes and effector sites like the lamina propria and the intestinal epithelium. This technique ensures isolation of a large numbers of lymphocytes from small intestinal tissues with optimal purity and viability and minimal cross compartmental contamination within acceptable time constraints. The technical capability to isolate lymphocytes and other immune cells from intestinal tissues enables the understanding of immune responses to gastrointestinal infections, cancers, and inflammatory diseases.

Here we describe a detailed protocol for the isolation of lymphocytes from the inductive sites including the gut-associated lymphoid tissue Peyer&#39;s patches and the draining mesenteric lymph nodes, and the effector sites including the lamina propria and the intestinal epithelium of the small intestinal immune system.

The intestinal immune system plays an essential role in maintaining the barrier function of the gastrointestinal tract by generating tolerant responses to ...

Rapid, Safe, and Simple Manual Bedside Nucleic Acid Extraction for the Detection of Virus in Whole Blood Samples

The rapid diagnosis of an infection is essential for the outbreak management, risk containment, and patient care. We have previously shown a method for the rapid bedside inactivation of the Ebola virus during blood sampling for safe nucleic acid (NA) tests by adding a commercial lysis/binding buffer directly into the vacuum blood collection tubes. Using this bedside inactivation approach, we have developed a safe, rapid, and simplified bedside NA extraction method for the subsequent detection of a virus in lysis/binding buffer-inactivated whole blood. The NA extraction is directly performed in the blood collection tubes and requires no equipment or electricity. 
After the blood is collected into the lysis/binding buffer, the contents are mixed by flipping the tube by hand, and the mixture is incubated for 20 min at room temperature. Magnetic glass particles (MGPs) are added to the tube, and the contents are mixed by flipping the collection tube by hand. The MGPs are then collected on the side of the blood collection tube using a magnetic holder or a magnet and a rubber band. The MGPs are washed three times, and after the addition of elution buffer directly into the collection tube, the NAs are ready for NA tests, such as qPCR or isothermal loop amplification (LAMP), without the removal of the MGPs from the reaction. The NA extraction method is not dependent on any laboratory facilities and can easily be used anywhere (e.g., in field hospitals and hospital isolation wards). When this NA extraction method is combined with LAMP and a portable instrument, a diagnosis can be obtained within 40 min of the blood collection.

Here, we present a protocol for the rapid virus nucleic acid extraction from the virus-inactivated whole blood. The extraction is performed directly in the blood collection tubes and requires no equipment or electricity. The method is not dependent on laboratory facilities and can be used anywhere (e.g., in field hospitals).

The rapid diagnosis of an infection is essential for the outbreak management, risk containment, and patient care. We have previously shown a method for ...