OMIP-068: High-Dimensional Characterization of Global and Antigen-Specific B Cells in Chronic Infection

Comprehensive Immunophenotyping by Polychromatic Cytometry

The human immune system comprises a diverse array of cells involved in innate and adaptive immunity, and these immune cells coordinate immune responses against pathogens through intricate interactions. Multicolor flow cytometry is a powerful technique for qualitatively and quantitatively measuring the characteristics of immune cells, offering advantages, such as high-dimensional analysis, elucidation of cellular heterogeneity, understanding of pathogenesis, development of therapeutic strategies, and platform flexibility. Here, we demonstrate a new immunophenotyping panel that allows simultaneous evaluation of the characteristics of T and B cells. This panel enables tracking of changes in the immune status due to aging, environmental factors, pathogen infections, and vaccine administration. Additionally, it includes co-stimulatory molecules for assessing the activation state of immune cells and inhibitory checkpoint molecules for evaluating exhaustion status, thereby providing valuable insights into the features of human immune responses. These analyses contribute to understanding the pathophysiology of diseases and developing therapeutic strategies while offering crucial information for assessing the correlation of symptoms with infections and evaluating the efficacy of vaccines.

Side-by-Side Comparison of Compensation Beads Used in Polychromatic Flow Cytometry

Compensation or unmixing is essential in analyzing multiparameter flow cytometry data. Errors in data correction, either by compensation or unmixing, can completely change the outcome or mislead the researchers. Owing to limited cell numbers, researchers often use synthetic beads to generate the required single stains for the necessary calculation. In this study, the capacity of synthetic beads to influence data correction is evaluated. Corrected data for human peripheral blood cells were generated using cell-based compensation from the same cells or bead-based compensation to identify differences between the methods. These data suggest that correction with beads on full-spectrum and conventional cytometers does not always follow the basic flow compensation/unmixing expectations and alters the data. Overall, the best approach for bead-based correction for an experiment is to evaluate which beads and fluorochromes are most accurately compensated/unmixed.

OMIP-94: Twenty-four-color (thirty-marker) panel for deep immunophenotyping of immune cells in human peripheral blood

This newly established 24-color (30-marker) panel focuses on the characterization of the main human immune cell subtypes and was optimized for the analysis of human whole blood using a full spectrum flow cytometer. The panel covers all main leukocyte populations: neutrophils, eosinophils and basophils, monocytes (with additional subsets), dendritic cells, innate lymphoid cells and lymphocytes. As for lymphocytes, this panel includes CD4+ T helper, Treg cells, and CD8+ cytotoxic T cells. Further T cells subsets are included with special focus on invariant T cells: γδ T cells (including δ2TCR variant), invariant NKT cells and MAIT (mucosal-associated invariant T cells) cells. Additionally, total B cells (including Bregs and plasmocytes), NK cells, and NKT cells are included. For the overall check of activation status of the analyzed immune cells we used HLA-DR, CD38, CD57, CD69, PD-1, and CD94. In addition, we used CD62L, CD45RA, CD27, and CD39 to describe the differentiation status of these cells. The panel was designed to maximize the information that can be obtained from surface markers in order to avoid the need for fixation and permeabilization steps. The presented multimarker panel offers the possibility to discover new immune cell subtypes which in patients and in cohort studies may lead to the identification of altered immune phenotypes and might give a link to immune system based or to certain other diseases. This panel was developed for a full spectrum flow cytometer equipped with a minimum of three lasers. We developed this panel using healthy human fresh blood, however it was also successfully used for staining of isolated human peripheral blood mononuclear cells (PBMC).

Cured HCV patients with suboptimal hepatitis B vaccine response exhibit high self-reactive immune signatures

BACKGROUND AND RATIONALE

Chronic HCV infection induces lasting effects on the immune system despite viral clearance. It is unclear whether certain immune alterations are associated with vaccine responses in cured HCV patients.

APPROACH

Thirteen cured HCV patients received the standard 3-dose hepatitis B vaccine and were followed up at the 0, 1st, 6th, and 7th months (M0, M1, M6, and M7) after the first dose of vaccination. Thirty-three-color and 26-color spectral flow cytometry panels were used for high-dimensional immunophenotyping of the T-cell and B-cell subsets, respectively.

RESULTS

Compared to the healthy controls (HC), 17 of 43 (39.5%) immune cell subsets showed abnormal frequencies in cured HCV patients. Patients with cured HCV were further divided into high responders (HR, n = 6) and nonresponders (NR1, n = 7) based on the levels of hepatitis B surface antibodies at M1. Alterations in cell populations were more significant in NR1. Moreover, we found that high levels of self-reactive immune signatures, including Tregs, TD/CD8, IgD-only memory B, and autoantibodies, were associated with suboptimal hepatitis B vaccine responses.

CONCLUSIONS

Our data suggest that cured HCV patients exhibit persistent perturbations in the adaptive immune system, among which highly self-reactive immune signatures may contribute to a suboptimal hepatitis B vaccine response.

Deep Immunophenotyping of Human Whole Blood by Standardized Multi-parametric Flow Cytometry Analyses

Immunophenotyping is proving crucial to understanding the role of the immune system in health and disease. High-throughput flow cytometry has been used extensively to reveal changes in immune cell composition and function at the single-cell level. Here, we describe six optimized 11-color flow cytometry panels for deep immunophenotyping of human whole blood. A total of 51 surface antibodies, which are readily available and validated, were selected to identify the key immune cell populations and evaluate their functional state in a single assay. The gating strategies for effective flow cytometry data analysis are included in the protocol. To ensure data reproducibility, we provide detailed procedures in three parts, including (1) instrument characterization and detector gain optimization, (2) antibody titration and sample staining, and (3) data acquisition and quality checks. This standardized approach has been applied to a variety of donors for a better understanding of the complexity of the human immune system.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43657-022-00092-9.

Adenoid lymphocyte heterogeneity in pediatric adenoid hypertrophy and obstructive sleep apnea

Introduction

Adenoid hypertrophy is the main cause of obstructive sleep apnea in children. Previous studies have suggested that pathogenic infections and local immune system disorders in the adenoids are associated with adenoid hypertrophy. The abnormalities in the number and function of various lymphocyte subsets in the adenoids may play a role in this association. However, changes in the proportion of lymphocyte subsets in hypertrophic adenoids remain unclear.

Methods

To identify patterns of lymphocyte subsets in hypertrophic adenoids, we used multicolor flow cytometry to analyze the lymphocyte subset composition in two groups of children: the mild to moderate hypertrophy group (n = 10) and the severe hypertrophy group (n = 5).

Results

A significant increase in naïve lymphocytes and a decrease in effector lymphocytes were found in severe hypertrophic adenoids.

Discussion

This finding suggests that abnormal lymphocyte differentiation or migration may contribute to the development of adenoid hypertrophy. Our study provides valuable insights and clues into the immunological mechanism underlying adenoid hypertrophy.

Analysis of Antigen-Specific T and B Cells for Monitoring Immune Protection Against SARS-CoV-2

Immunological memory is the basis of protection against most pathogens. Long-living memory T and B cells able to respond to specific stimuli, as well as persistent antibodies in plasma and in other body fluids, are crucial for determining the efficacy of vaccination and for protecting from a second infection by a previously encountered pathogen. Antigen-specific cells are represented at a very low frequency in the blood, and indeed, they can be considered "rare events" present in the memory T-cell pool. Therefore, such events should be analyzed with careful attention. In the last 20 years, different methods, mostly based upon flow cytometry, have been developed to identify such rare antigen-specific cells, and the COVID-19 pandemic has given a dramatic impetus to characterize the immune response against the virus. In this regard, we know that the identification, enumeration, and characterization of SARS-CoV-2-specific T and B cells following infection and/or vaccination require i) the use of specific peptides and adequate co-stimuli, ii) the use of appropriate inhibitors to avoid nonspecific activation, iii) the setting of appropriate timing for stimulation, and iv) the choice of adequate markers and reagents to identify antigen-specific cells. Optimization of these procedures allows not only determination of the magnitude of SARS-CoV-2-specific responses but also a comparison of the effects of different combinations of vaccines or determination of the response provided by so-called "hybrid immunity," resulting from a combination of natural immunity and vaccine-generated immunity. Here, we present two methods that are largely used to monitor the response magnitude and phenotype of SARS-CoV-2-specific T and B cells by polychromatic flow cytometry, along with some tips that can be useful for the quantification of these rare events. © 2023 Wiley Periodicals LLC. Basic Protocol 1: Identification of antigen-specific T cells Basic Protocol 2: Identification of antigen-specific B cells.

Increased death and exhaustion of CD69high T cells and NK cells are associated with PD-1 antibody application in the in vitro co-culture system

Background

The application of PD-1 monoclonal antibody (mAb) helps to treat non-small cell lung cancer, but acquired resistance has emerged in clinical practice. We tested the hypothesis that acquired resistance of anti-PD-1 immunotherapy is linked to death and exhaustion of activated T and NK cell.

Methods

The co-culture system of HCC827 cells and peripheral mononuclear cells (PBMCs) was established to evaluate the effect of PD-1 mAb on the death rate and exhaustion of T and NK cell. The predisposing role of CD69 for death and exhaustion was validated by using PHA-activated PBMCs of CD69^low NSCLC patients. The 10-colour/three laser flow cytometer was used to test related markers for cell activation, death and exhaustion.

Results

We found that PD-1 mAb increase the death and exhaustion of T cells and NK cells in a dose-dependent way when PBMCs from NSCLC patients whose the percentages of CD69⁺ cells in peripheral blood T cells were greater than 5% (CD69^high NSCLC patients). By analyzing PBMCs from healthy volunteers and CD69^low NSCLC patients, we found that T cells and NK cells can be induced to die by PD-1 mAb after PHA activation, and had a tendency to raise the rate of cell exhaustion.

Conclusions

Our findings imply that increased death and exhaustion of CD69^high T cells and NK cells are associated with ineffective anti-PD-1 immunotherapy in lung cancer. The CD69 expression of T cells and NK cells may be developed as a potential predictor for acquired resistance of anti-PD-1 immunotherapy. These data may provide ideas to guide individualized medication of PD-1 mAb in NSCLC patients.

Comprehensive phenotyping of human peripheral blood B lymphocytes in pathological conditions

Several diseases are associated with alterations of the B-cell compartment. Knowing how to correctly identify by flow cytometry the distribution of B-cell populations in the peripheral blood is important to help in the early diagnosis. In the accompanying article we describe how to identify the different B-cell subsets in the peripheral blood of healthy donors. Here we show a few examples of diseases that cause dysregulation of the B-cell compartment.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (third edition)

The third edition of Flow Cytometry Guidelines provides the key aspects to consider when performing flow cytometry experiments and includes comprehensive sections describing phenotypes and functional assays of all major human and murine immune cell subsets. Notably, the Guidelines contain helpful tables highlighting phenotypes and key differences between human and murine cells. Another useful feature of this edition is the flow cytometry analysis of clinical samples with examples of flow cytometry applications in the context of autoimmune diseases, cancers as well as acute and chronic infectious diseases. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid. All sections are written and peer-reviewed by leading flow cytometry experts and immunologists, making this edition an essential and state-of-the-art handbook for basic and clinical researchers.

Characterising the Phenotypic Diversity of Antigen-Specific Memory B Cells Before and After Vaccination

The diversity of B cell subsets and their contribution to vaccine-induced immunity in humans are not well elucidated but hold important implications for rational vaccine design. Prior studies demonstrate that B cell subsets distinguished by immunoglobulin (Ig) isotype expression exhibit divergent activation-induced fates. Here, the antigen-specific B cell response to tetanus toxoid (TTd) booster vaccination was examined in healthy adults, using a dual-TTd tetramer staining flow cytometry protocol. Unsupervised analyses of the data revealed that prior to vaccination, IgM-expressing CD27⁺ B cells accounted for the majority of TTd-binding B cells. 7 days following vaccination, there was an acute expansion of TTd-binding plasmablasts (PB) predominantly expressing IgG, and a minority expressing IgA or IgM. Frequencies of all PB subsets returned to baseline at days 14 and 21. TTd-binding IgG⁺ and IgA⁺ memory B cells (MBC) exhibited a steady and delayed maximal expansion compared to PB, peaking in frequencies at day 14. In contrast, the number of TTd-binding IgM⁺IgD⁺CD27⁺ B cells and IgM-only CD27⁺ B cells remain unchanged following vaccination. To examine TTd-binding capacity of IgG⁺ MBC and IgM⁺IgD⁺CD27⁺ B cells, surface TTd-tetramer was normalised to expression of the B cell receptor-associated CD79b subunit. CD79b-normalised TTd binding increased in IgG⁺ MBC, but remained unchanged in IgM⁺IgD⁺CD27⁺ B cells, and correlated with the functional affinity index of plasma TTd-specific IgG antibodies, following vaccination. Finally, frequencies of activated (PD-1⁺ICOS⁺) circulating follicular helper T cells (cT_FH), particularly of the CXCR3^-CCR6^- cT_FH2 cell phenotype, at their peak expansion, strongly predicted antigen-binding capacity of IgG⁺ MBC. These data highlight the phenotypic and functional diversity of the B cell memory compartment, in their temporal kinetics, antigen-binding capacities and association with cT_FH cells, and are important parameters for consideration in assessing vaccine-induced immune responses.