tumor-transplantation-for-assessing-dynamics-tumor-infiltrating-cd8-t

Tumor Transplantation for Assessing the Dynamics of Tumor-Infiltrating CD8<sup>+</sup> T Cells in Mice

T cell-mediated immunity plays a crucial role in immune responses against tumors, with cytotoxic T lymphocytes (CTLs) playing the leading role in ...

draining-lymph-node-metastasis-model-for-assessing-dynamics-antigen

Draining Lymph Node Metastasis Model for Assessing the Dynamics of Antigen-Specific CD8<sup>+</sup> T Cells During Tumorigenesis

Tumor antigen-specific CD8+ T cells from draining lymph nodes gain an accumulating importance in mounting anti-tumor immune response during tumorigenesis. ...

The General Hospital of Western Theater Command

Chongqing Medical University

During viral infection, virus-specific follicular helper T cells provide important help to cognate B cells for their survival, consecutive proliferation and mutation and eventual differentiation into memory B cells and antibody-secreting plasma cells. Similar to Tfh cells generated in other conditions, the differentiation of virus-specific Tfh cells can also be characterized as a process involved multiple factors and stages, however, which also exhibits distinct features. Here, we mainly focus on the current understanding of Tfh fate commitment, functional maturation, lineage maintenance and memory transition and formation in the context of viral infection.

Molecular Basis of the Differentiation and Function of Virus Specific Follicular Helper CD4 T Cells.

Epigenetic modifications to histones dictate the differentiation of naïve CD4 T cells into different subsets of effector T helper (T) cells. The histone methyltransferase enhancer of zeste homolog 2 (EZH2) has been implicated in the mechanism regulating the differentiation of T1, T2 and regulatory T (T) cells. However, whether and how EZH2 regulates follicular helper T (T) cell differentiation remain unknown. Using a mouse model of acute lymphocytic choriomeningitis virus (LCMV) infection, we observed abundant EZH2 expression and associated H3K27me3 modifications preferentially in the early committed virus-specific T cells compared to those in T1 cells. Ablation of EZH2 in LCMV-specific CD4 T cells leads to a selective impairment of early T cell fate commitment, but not late T differentiation or memory T maintenance. Mechanistically, EZH2 specifically stabilizes the chromatin accessibility of a cluster of genes that are important for T fate commitment, particularly B cell lymphoma 6 (Bcl6), and thus directs T cell commitment. Therefore, we identified the chromatin-modifying enzyme EZH2 as a novel regulator of early T differentiation during acute viral infection.

The histone methyltransferase EZH2 primes the early differentiation of follicular helper T cells during acute viral infection.

Follicular helper T cells (TFH cells), known as the primary "helpers" of the germinal center (GC) reaction, promote the humoral immune response to defend against various pathogens. Under conditions of infection by different types of pathogens, many shared transcription factors (TFs), such as Bcl-6, TCF-1, and Maf, are selectively enriched in pathogen-specific TFH cells, orchestrating TFH cell differentiation and function. In addition, TFH cells also coexpress environmentally associated TFs as their conventional T cell counterparts (such as T-bet, GATA-3, or ROR-γt, which are expressed in Th1, Th2, or Th17 cells, respectively). These features likely indicate both the lineage-specificity and environmental adaption of the TFH cell responses. However, the extent to which the TFH cell response relies on these environmentally specific TFs is not completely understood. Here, we found that T-bet was specifically expressed in Type I TFH cells but not Type II TFH cells. While dispensable for the early fate commitment of TFH cells, T-bet was essential for the maintenance of differentiated TFH cells, promoting their proliferation, and inhibiting their apoptosis during acute viral infection. Microarray analysis showed both similarities and differences in transcriptome dependency on T-bet in TFH and TH1 cells, suggesting the distinctive role of T-bet in TFH cells. Collectively, our findings reveal an important and specific supporting role for T-bet in type I TFH cell response, which can help us gain a deeper understanding of TFH cell subsets.

The Transcription Factor T-Bet Is Required for Optimal Type I Follicular Helper T Cell Maintenance During Acute Viral Infection.

B-cell follicle represents a functionally dynamic microstructure within second lymphoid tissues, predominantly consisting of B cells, follicular T cells and DCs. Through intimate interactions with cognate B cells, follicular helper T cells (Tfh) initiate and facilitate germinal center (GC) reactions by providing signals required for producing high-affinity antibodies, as well as for the generation of long-lived antibody-secreting plasma cells and memory B cells. Concomitantly, germinal center reaction needs to be fine controlled to avoid autoimmunity or B-cell malignancies. Among immune cells residing in follicles, follicular regulatory T cells (Tfr), converted from naïve Treg cells, are specifically assigned to repress excessive GC responses by suppressing Tfh and GC B cells within GC structure. Hence, through Yin and Yang (positive and negative) regulation of GC reaction, Tfh cells play concert with Tfr cells in maintaining immune homeostasis. Besides CD4 T cells, a small portion of CXCR5 expressing CD8 T cells, regarded as follicular cytotoxic T cells (Tfc), could migrate into B cell follicles during chronic viral infection and several types of cancers, and this population exhibit lower level of exhaustion than its CXCR5 counterparts. Besides, Tfc cells demonstrate a stem-cell like phenotype during chronic infection which could further differentiate into terminally differentiated CXCR5CD8 T cells. Collectively, in this review, we will discuss the recent advances in our understanding of the ontology and differentiation of B-cell follicle resident Tfh, Tfr and Tfc cells.

T cell immune response within B-cell follicles.

Human monoclonal antibodies block the binding of SARS-CoV-2 spike protein to angiotensin converting enzyme 2 receptor.

During tumorigenesis, tumor infiltrating regulatory T (Treg) cells restrict the function of effector T cells in tumor microenvironment and thereby promoting tumor growth. The anti-tumor activity of effector T cells can be therapeutically unleashed, and is now being exploited for the treatment of various types of human cancers. However, the immune suppressive function of Treg cells remains a major hurdle to broader effectiveness of tumor immunotherapy. In this article, we reported that the deletion of Bcl6 specifically in Treg cells led to stunted tumor growth, which was caused by impaired Treg cell responses. Notably, Bcl6 is essential in maintaining the lineage stability of Treg cells in tumor microenvironment. Meanwhile, we found that the absence of follicular regulatory T (Tfr) cells, which is a result of Bcl6 deletion in Foxp3 cells, was dispensable for tumor control. Importantly, the increased Bcl6 expression in Treg cells is associated with poor prognosis of human colorectal cancer and lymph node metastasis of skin melanoma. Furthermore, Bcl6 deletion in Treg cells exhibits synergistic effects with immune checkpoint blockade therapy. Collectively, these results indicate that Bcl6 actively participates in regulating Treg cell immune responses during tumorigenesis and can be exploited as a therapeutic target of anti-tumor immunity.

Bcl6 Preserves the Suppressive Function of Regulatory T Cells During Tumorigenesis.

COVID-19 patients exhibit differential disease severity after SARS-CoV-2 infection. It is currently unknown as to the correlation between the magnitude of neutralizing antibody (NAb) responses and the disease severity in COVID-19 patients. In a cohort of 59 recovered patients with disease severity including severe, moderate, mild, and asymptomatic, we observed the positive correlation between serum neutralizing capacity and disease severity, in particular, the highest NAb capacity in sera from the patients with severe disease, while a lack of ability of asymptomatic patients to mount competent NAbs. Furthermore, the compositions of NAb subtypes were also different between recovered patients with severe symptoms and with mild-to-moderate symptoms. These results reveal the tremendous heterogeneity of SARS-CoV-2-specific NAb responses and their correlations to disease severity, highlighting the needs of future vaccination in COVID-19 patients recovered from asymptomatic or mild illness.

Disease severity dictates SARS-CoV-2-specific neutralizing antibody responses in COVID-19.

The adaptive immunity that protects patients from coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is not well characterized. In particular, the asymptomatic patients have been found to induce weak and transient SARS-CoV-2 antibody responses, but the underlying mechanisms remain unknown; meanwhile, the protective immunity that guide the recovery of these asymptomatic patients is elusive. Here, we characterized SARS-CoV-2-specific B-cell and T-cell responses in 10 asymptomatic patients and 64 patients with other disease severity (mild, n = 10, moderate, n = 32, severe, n = 12) and found that asymptomatic or mild symptomatic patients failed to mount virus-specific germinal center (GC) B cell responses that result in robust and prolonged humoral immunity, assessed by GC response indicators including follicular helper T (T) cell and memory B cell responses as well as serum CXCL13 levels. Alternatively, these patients mounted potent virus-specific T1 and CD8 T cell responses. In sharp contrast, patients of moderate or severe disease induced vigorous virus-specific GC B cell responses and associated T responses; however, the virus-specific T1 and CD8 T cells were minimally induced in these patients. These results, therefore, uncovered the protective immunity in asymptomatic patients and also revealed the strikingly dichotomous and incomplete humoral and cellular immune responses in COVID-19 patients with different disease severity, providing important insights into rational design of effective COVID-19 vaccines.

The dichotomous and incomplete adaptive immunity in COVID-19 patients with different disease severity.

Follicular regulatory T cells (Tfrs), a specialized subset of regulatory T cells (Tregs), have a particular role in the control of follicular helper T cell-driven germinal center (GC) responses. Following differentiation signals similar to those received by follicular helper T cells (Tfhs), Tfrs gain expression of characteristic chemokine receptors and transcription factors, such as CXCR5 and Bcl-6, allowing them to migrate into the B-cell follicle and perform in situ suppression. Thus, together with Tfhs, Tfrs help maintaining an optimized GC-reaction. However, the mechanism underlying the Treg-to-Tfr transition remains obscure. Here, we established a highly reproducible protocol for investigating the differentiation of Tregs into Tfrs by constructing spleen-chimeric mice combined with retrovirus transduction. We demonstrated that using this strategy, over 4 folds of Tregs could differentiate into Tfrs in Bcl-6 overexpression group compared to control counterparts (Migr1), and Bcl-6 could efficiently promote Tfr differentiation during acute viral infection. Hence, this method provides us an easy access to investigate the factors that regulate the differentiation program that converts Tregs into Tfrs, which will enhance our understanding of the networks regulating GC-reaction and shed new light on the molecular basis of immune homeostasis.

ArticleTotal : 2	Year
Publication title	2021
Publication title	2024

Article	Year
Molecular Basis of the Differentiation and Function of Virus Specific Follicular Helper CD4 T Cells. Frontiers in immunology\| PubMed ID: 30828337	2019
The histone methyltransferase EZH2 primes the early differentiation of follicular helper T cells during acute viral infection. Cellular & molecular immunology\| PubMed ID: 30842630	2019
The Transcription Factor T-Bet Is Required for Optimal Type I Follicular Helper T Cell Maintenance During Acute Viral Infection. Frontiers in immunology\| PubMed ID: 30984183	2019
T cell immune response within B-cell follicles. Advances in immunology\| PubMed ID: 31699216	2019
Human monoclonal antibodies block the binding of SARS-CoV-2 spike protein to angiotensin converting enzyme 2 receptor. Cellular & molecular immunology\| PubMed ID: 32313207	2020
Bcl6 Preserves the Suppressive Function of Regulatory T Cells During Tumorigenesis. Frontiers in immunology\| PubMed ID: 32477338	2020
Disease severity dictates SARS-CoV-2-specific neutralizing antibody responses in COVID-19. Signal transduction and targeted therapy\| PubMed ID: 32879307	2020
The dichotomous and incomplete adaptive immunity in COVID-19 patients with different disease severity. Signal transduction and targeted therapy\| PubMed ID: 33686064	2021
A novel strategy to investigate the factors regulating the Treg to Tfr transition during acute viral infection. Journal of immunological methods\| PubMed ID: 35398062	2022
Tumor-specific memory CD8 T cells are strictly resident in draining lymph nodes during tumorigenesis. Cellular & molecular immunology\| PubMed ID: 36859455	2023
Author Correction: Tumor-specific memory CD8 T cells are strictly resident in draining lymph nodes during tumorigenesis. Cellular & molecular immunology\| PubMed ID: 37225839	2023

Qizhao Huang

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