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

Summary

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.

Abstract

Infectious mononucleosis (IM) is an acute syndrome mostly associated with primary Epstein–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.

Introduction

Epstein–Barr virus (EBV), a γ-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 2–6 weeks and t....

Protocol

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's Hospital, Capital Medical University, and all studies were ethically approved. Ethical approval was obtained by the Ethics Committee of Beijing Children'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.......

Discussion

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.......

Materials

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