CD8+CXCR5+ T cells in tumor-draining lymph nodes are highly activated and predict better prognosis in colorectal cancer

Single-cell adhesive profiling in an optofluidic device elucidates CD8+ T lymphocyte phenotypes in inflamed vasculature-like microenvironments

Tissue infiltration by circulating leukocytes occurs via adhesive interactions with the local vasculature, but how the adhesive quality of circulating cells guides the homing of specific phenotypes to different vascular microenvironments remains undefined. We developed an optofluidic system enabling fluorescent labeling of photoactivatable cells based on their adhesive rolling velocity in an inflamed vasculature-mimicking microfluidic device under physiological fluid flow. In so doing, single-cell level multidimensional profiling of cellular characteristics could be characterized and related to the associated adhesive phenotype. When applied to CD8+ T cells, ligand/receptor expression profiles and subtypes associated with adhesion were revealed, providing insight into inflamed tissue infiltration capabilities of specific CD8+ T lymphocyte subsets and how local vascular microenvironmental features may regulate the quality of cellular infiltration. This methodology facilitates rapid screening of cell populations for enhanced homing capabilities under defined biochemical and biophysical microenvironments, relevant to leukocyte homing modulation in multiple pathologies.

Quercetin Limits Tumor Immune Escape through PDK1/CD47 Axis in Melanoma

Quercetin (3,3[Formula: see text],4[Formula: see text],5,7-pentahydroxyflavone) is a bioactive plant-derived flavonoid, abundant in fruits and vegetables, that can effectively inhibit the growth of many types of tumors without toxicity. Nevertheless, the effect of quercetin on melanoma immunology has yet to be determined. This study aimed to investigate the role and mechanism of the antitumor immunity action of quercetin in melanoma through both in vivo and in vitro methods. Our research revealed that quercetin has the ability to boost antitumor immunity by modulating the tumor immune microenvironment through increasing the percentages of M1 macrophages, CD8[Formula: see text] T lymphocytes, and CD4[Formula: see text] T lymphocytes and promoting the secretion of IL-2 and IFN-[Formula: see text] from CD8[Formula: see text] T cells, consequently suppressing the growth of melanoma. Furthermore, we revealed that quercetin can inhibit cell proliferation and migration of B16 cells in a dose-dependent manner. In addition, down-regulating PDK1 can inhibit the mRNA and protein expression levels of CD47. In the rescue experiment, we overexpressed PDK1 and found that the protein and mRNA expression levels of CD47 increased correspondingly, while the addition of quercetin reversed this effect. Moreover, quercetin could stimulate the proliferation and enhance the function of CD8[Formula: see text] T cells. Therefore, our results identified a novel mechanism through which CD47 is regulated by quercetin to promote phagocytosis, and elucidated the regulation of quercetin on macrophages and CD8[Formula: see text] T cells in the tumor immune microenvironment. The use of quercetin as a therapeutic drug holds potential benefits for immunotherapy, enhancing the efficacy of existing treatments for melanoma.

An angel or a devil? Current view on the role of CD8+ T cells in the pathogenesis of myasthenia gravis

BACKGROUND

Myasthenia gravis (MG) and the experimental autoimmune MG (EAMG) animal model are characterized by T-cell-induced and B-cell-dominated autoimmune diseases that affect the neuromuscular junction. Several subtypes of CD4+ T cells, including T helper (Th) 17 cells, follicular Th cells, and regulatory T cells (Tregs), contribute to the pathogenesis of MG. However, increasing evidence suggests that CD8+ T cells also play a critical role in the pathogenesis and treatment of MG.

MAIN BODY

Herein, we review the literature on CD8+ T cells in MG, focusing on their potential effector and regulatory roles, as well as on relevant evidence (peripheral, in situ, cerebrospinal fluid, and under different treatments), T-cell receptor usage, cytokine and chemokine expression, cell marker expression, and Treg, Tc17, CD3+CD8+CD20+ T, and CXCR5+ CD8+ T cells.

CONCLUSIONS

Further studies on CD8+ T cells in MG are necessary to determine, among others, the real pattern of the Vβ gene usage of autoantigen-specific CD8+ cells in patients with MG, real images of the physiology and function of autoantigen-specific CD8+ cells from MG/EAMG, and the subset of autoantigen-specific CD8+ cells (Tc1, Tc17, and IL-17+IFN-γ+CD8+ T cells). There are many reports of CD20-expressing T (or CD20 + T) and CXCR5+ CD8 T cells on autoimmune diseases, especially on multiple sclerosis and rheumatoid arthritis. Unfortunately, up to now, there has been no report on these T cells on MG, which might be a good direction for future studies.

Immune checkpoint status and exhaustion-related phenotypes of CD8+ T cells from the tumor-draining regional lymph nodes in breast cancer

BACKGROUND

Functional status of T cells determines the responsiveness of cancer patients to immunotherapeutic interventions. Even though T cell-mediated immunity is inaugurated in the tumor-adjacent lymph nodes, peripheral blood has been routinely sampled for testing the immunological assays. The purpose of this study is to determine the immune checkpoint molecule expression and the exhaustion-related phenotype of cytotoxic T cells in the regional lymph nodes from breast cancer patients.

PATIENTS AND METHODS

Multicolor immunophenotyping was used to determine the expression of PD-1, TIM-3, LAG3, CTLA-4, CCR7, CD45RO, CD127, CD25, CXCR5, and ICOS molecules on CD3+ CD4- CD56- CD8+ cytotoxic T cells freshly obtained from the lymph nodes and the peripheral blood samples of the breast cancer patients. The results were assessed together with the clinical data.

RESULTS

A population of cytotoxic T cells was noted with high PD-1 and CXCR5 expression in the lymph nodes of the breast cancer patients. Co-expression of PD-1, CXCR5, TIM-3, and ICOS indicated a follicular helper T cell (Tfh)-like, exhaustion-related immunophenotype in these cytotoxic T cells. Only a minor population with CTLA-4 and LAG3 expression was noted. The PD-1+ CXCR5+ cytotoxic T cells largely displayed CD45RO+ CCR7+ central memory markers. The amount of CXCR5-expressing PD-1- cytotoxic T cells was elevated in the lymph nodes of the patients.

CONCLUSION

The regional lymph nodes of breast cancer patients harbor Tfh-like exhausted cytotoxic T lymphocytes with high PD-1 and TIM-3 checkpoint molecule expression. The immunological conditions in the regional lymph nodes should be implicated for immune checkpoint immunotherapy (ICI) of cancer.

Exploring the potential mechanisms of Yi-Yi-Fu-Zi-Bai-Jiang-San therapy on the immune-inflamed phenotype of colorectal cancer via combined network pharmacology and bioinformatics analyses

BACKGROUND

The development and progression of colorectal cancer (CRC) is closely associated with its complex tumor microenvironment (TME). Assessment of the modified pattern of immune cell infiltration (ICI) will help increase knowledge regarding the characteristics of TME infiltration. Yi-Yi-Fu-Zi-Bai-Jiang-San (YYFZBJS) has been shown to have positive effects on the regulation of the immune microenvironment of CRC. However, its pharmacological targets and molecular mechanisms remain to be elucidated.

METHODS

Network pharmacological analysis was used to identify the target of YYFZBJS in the TME of CRC. Patients with the immune-inflamed phenotype (IIP) were identified using CRC samples from The Cancer Genome Atlas (TCGA) database. Consensus genes were identified by intersecting YYFZBJS targets, CRC disease targets and differentially expressed genes in the CRC microenvironment. Then, least absolute shrinkage and selection operator (LASSO) Cox analyses were used to identify a prognostic signature from the consensus genes. Cytoscape software was further used to build a unique herb-compound-target network diagram of the important components of YYFZBJS and prognostic gene targets. In addition, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis was performed using the prognostic gene sets to explore the molecular mechanism of the prognostic genes in drug therapy for CRC IIP patients. Finally, single-cell analysis was performed to validate the expression of the prognostic genes in the TME of CRC using the TISCH2 database.

RESULTS

A total of 284 IIP patients were identified from 480 patients with CRC. A total of 35 consensus genes were identified as targets of YYFZBJS in the TME of CRC patients. An eleven-gene prognostic signature, including PIK3CG, C5AR1, PRF1, CAV1, HPGDS, PTGS2, SERPINE1, IDO1, TGFB1, CXCR2 and MMP9, was identified from the consensus genes, with areas under the receiver operating characteristic (ROC) curve (AUCs) values of 0.84 and 0.793 for the training and test cohorts, respectively. In the herb-compound-target network, twenty-four compounds were shown to interact with the 11 prognostic genes, which were significantly enriched in the IL-17 signaling, arachidonic acid metabolism and metabolic pathways. Single-cell analysis of the prognostic genes confirmed that their abnormal expression was associated with the TME of CRC.

CONCLUSION

This study organically integrated network pharmacology and bioinformatics analyses to identify prognostic genes in CRC IIP patients from the targets of YYFZBJS. Although this data mining work was limited to the study of mechanisms related to prognosis based on the immune microenvironment, the methodology provides new perspectives in the search for novel therapeutic targets of traditional Chinese medicines (TCMs) and accurate diagnostic indicators of cancers targeted by TCMs.

CD8 T-cell subsets: heterogeneity, functions, and therapeutic potential

CD8 T cells play crucial roles in immune surveillance and defense against infections and cancer. After encountering antigenic stimulation, naïve CD8 T cells differentiate and acquire effector functions, enabling them to eliminate infected or malignant cells. Traditionally, cytotoxic T cells, characterized by their ability to produce effector cytokines and release cytotoxic granules to directly kill target cells, have been recognized as the constituents of the predominant effector T-cell subset. However, emerging evidence suggests distinct subsets of effector CD8 T cells that each exhibit unique effector functions and therapeutic potential. This review highlights recent advancements in our understanding of CD8 T-cell subsets and the contributions of these cells to various disease pathologies. Understanding the diverse roles and functions of effector CD8 T-cell subsets is crucial to discern the complex dynamics of immune responses in different disease settings. Furthermore, the development of immunotherapeutic approaches that specifically target and regulate the function of distinct CD8 T-cell subsets holds great promise for precision medicine.

Lymph node metastasis and tumor-educated immune tolerance: Potential therapeutic targets against distant metastasis

Lymph node metastasis has been shown to positively associated with the prognosis of many cancers. However, in clinical treatment, lymphadenectomy is not always successful, suggesting that immune cells in the tumor and sentinel lymph nodes still play a pivotal role in tumor immunosuppression. Recent studies had shown that tumors can tolerate immune cells through multiple strategies, including tumor-induced macrophage reprogramming, T cells inactivation, production of B cells pathogenic antibodies and activation of regulatory T cells to promote tumor colonization, growth, and metastasis in lymph nodes. We reviewed the bidirectional effect of immune cells on anti-tumor or promotion of cancer cell metastasis during lymph node metastasis, and the mechanisms by which malignant cancer cells modify immune cells to create a more favorable environment for the growth and survival of cancer cells. Research and treatment strategies focusing on the immune system in lymph nodes and potential immune targets in lymph node metastasis were also be discussed.

Deep immunophenotyping reveals circulating activated lymphocytes in individuals at risk for rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease with currently no universally highly effective prevention strategies. Identifying pathogenic immune phenotypes in 'At-Risk' populations prior to clinical disease onset is crucial to establishing effective prevention strategies. Here, we applied mass cytometry to deeply characterize the immunophenotypes in blood from At-Risk individuals identified through the presence of serum antibodies to citrullinated protein antigens (ACPA) and/or first-degree relative (FDR) status (n=52), as compared to established RA (n=67), and healthy controls (n=48). We identified significant cell expansions in At-Risk individuals compared with controls, including CCR2+CD4+ T cells, T peripheral helper (Tph) cells, type 1 T helper cells, and CXCR5+CD8+ T cells. We also found that CD15+ classical monocytes were specifically expanded in ACPA-negative FDRs, and an activated PAX5 low naïve B cell population was expanded in ACPA-positive FDRs. Further, we developed an "RA immunophenotype score" classification method based on the degree of enrichment of cell states relevant to established RA patients. This score significantly distinguished At-Risk individuals from controls. In all, we systematically identified activated lymphocyte phenotypes in At-Risk individuals, along with immunophenotypic differences among both ACPA+ and ACPA-FDR At-Risk subpopulations. Our classification model provides a promising approach for understanding RA pathogenesis with the goal to further improve prevention strategies and identify novel therapeutic targets.

Cytolytic CD8+ T cells infiltrate germinal centers to limit ongoing HIV replication in spontaneous controller lymph nodes

Follicular CD8⁺ T cells (fCD8) mediate surveillance in lymph node (LN) germinal centers against lymphotropic infections and cancers, but the precise mechanisms by which these cells mediate immune control remain incompletely resolved. To address this, we investigated functionality, clonotypic compartmentalization, spatial localization, phenotypic characteristics, and transcriptional profiles of LN-resident virus-specific CD8⁺ T cells in persons who control HIV without medications. Antigen-induced proliferative and cytolytic potential consistently distinguished spontaneous controllers from noncontrollers. T cell receptor analysis revealed complete clonotypic overlap between peripheral and LN-resident HIV-specific CD8⁺ T cells. Transcriptional analysis of LN CD8⁺ T cells revealed gene signatures of inflammatory chemotaxis and antigen-induced effector function. In HIV controllers, the cytotoxic effectors perforin and granzyme B were elevated among virus-specific CXCR5⁺ fCD8s proximate to foci of HIV RNA within germinal centers. These results provide evidence consistent with cytolytic control of lymphotropic infection supported by inflammatory recruitment, antigen-specific proliferation, and cytotoxicity of fCD8s.

Follicular CD8+ T Cells Are Elevated in HIV Infection and Induce PD-L1 on B Cells

Follicular CD8+CXCR5+ T cells are a specialized CD8+ T cell subset with unique follicular-homing capabilities that have been reported to display effector functions in viral immunity, tumor immunity, and autoimmunity. CD8+CXCR5+ T cells exhibit B cell helper functions and express CD40L, ICOS, programmed cell death protein 1 (PD-1), and BCL-6, the transcriptional regulator of CD4+CXCR5+ T follicular helper cells and of germinal center B cells. HIV is known to be sequestered in lymphoid follicles, and CD8+CXCR5+ T cell frequency is a marker for disease severity, given that HIV-infected patients with lower numbers of circulating CD8+CXCR5+ T cells display lower CD4+ T cell counts. Likewise, several groups have reported a direct correlation between the quantity of CD8+CXCR5+ T cells and suppression of HIV viral load. In this study, we observed elevated absolute numbers of CD8+CXCR5+ and CD8+CXCR5+BCL-6+PD-1+ T cells in the blood of HIV-infected participants of the Multicenter AIDS Cohort Study. We further demonstrated in vitro that activated human CD8+CXCR5+ T cells isolated from peripheral blood and tonsil from healthy donors show increased CD40L expression and induce the production of PD ligand 1 (PD-L1)+IgG+ B cells. Moreover, absolute numbers of CD8+CXCR5+ T cells significantly and positively correlated with numbers of PD-L1+ B cells found in blood of HIV-infected individuals. Altogether, these results show that activated CD8+CXCR5+ T cells have the ability to activate B cells and increase the percentage of PD-L1+ and PD-L1+IgG+ B cells, which provides insights into the early events of B cell activation and differentiation and may play a role in disease progression and lymphomagenesis in HIV-infected individuals.

Biology and clinical relevance of follicular cytotoxic T cells

Follicular cytotoxic T (Tfc) cells are a newly identified subset of CD8⁺ T cells enriched in B cell follicles and their surroundings, which integrate multiple functions such as killing, memory, supporting and regulation. Tfc cells share similarities with follicular helper T (Tfh) cells, conventional cytotoxic CD8⁺ T (Tc cells)cells and follicular regulatory T (Tfr) cells, while they express distinct transcription factors, phenotype, and perform different functions. With the participation of cytokines and cell-cell interactions, Tfc cells modulate Tfh cells and B cells and play an essential role in regulating the humoral immunity. Furthermore, Tfc cells have been found to change in their frequencies and functions during the occurrence and progression of chronic infections, immune-mediated diseases and cancers. Strategies targeting Tfc cells are under investigations, bringing novel insights into control of these diseases. We summarize the characteristics of Tfc cells, and introduce the roles and potential targeting modalities of Tfc cells in different diseases.

CXCR5+CD8 T cells: Potential immunotherapy targets or drivers of immune-mediated adverse events?

CXCR5⁺CD8 T cells have attracted significant interest within multiple areas of immunology, cancer, and infection. This is in part due to their apparent dual functionality. These cells perform as cytotoxic cells in a variety of infection states including LCMV, HBV, HIV and SIV. However, CXCR5⁺CD8 T cells also associate with B cells in peripheral organs and function to stimulate B cell proliferation, antibody/B cell receptor class-switch, and antibody production. CXCR5⁺CD8 T cells are similar to CXCR5⁺CD4 T follicular helpers in their genetic make-up, B cell interactions, and functionality despite possessing elevated programmed cell death 1 and cytotoxic proteins. Within cancer CXCR5⁺CD8 T cells have risen as potential prognostic markers for overall survival and are functionally cytotoxic within tumor microenvironments. In inflammatory disease and autoimmunity, CXCR5⁺CD8 T cells are implicated in disease progression. During viral infection and cancer, CXCR5 expression on CD8 T cells generally is indicative of progenitor memory stem-like exhausted cells, which are more responsive to immune checkpoint blockade therapy. The use of immune checkpoint inhibitors to overcome immune exhaustion in cancer, and subsequent consequence of immune adverse events, highlights the dual nature of the cellular immune response. This review will detail the functionality of CXCR5⁺CD8 T cells in cancer and autoimmunity with potential repercussions during immune checkpoint blockade therapy discussed.

CXCL13-CXCR5 axis: Regulation in inflammatory diseases and cancer

Chemokine C-X-C motif ligand 13 (CXCL13), originally identified as a B-cell chemokine, plays an important role in the immune system. The interaction between CXCL13 and its receptor, the G-protein coupled receptor (GPCR) CXCR5, builds a signaling network that regulates not only normal organisms but also the development of many diseases. However, the precise action mechanism remains unclear. In this review, we discussed the functional mechanisms of the CXCL13-CXCR5 axis under normal conditions, with special focus on its association with diseases. For certain refractory diseases, we emphasize the diagnostic and therapeutic role of CXCL13-CXCR5 axis.

Protein Kinase Inhibitor-Mediated Immunoprophylactic and Immunotherapeutic Control of Colon Cancer

Immunotherapy has allowed major advances in oncology in the past years, in particular with the development of immune checkpoint inhibitors, but the clinical benefits are still limited, particularly in colorectal cancer (CRC). Our scientific approach is based on the search for innovative immunotherapy with a final goal that aims to induce an effective antitumor immune response in CRC. Here, we focused on a multikinase inhibitor, H89. We carried out in vivo experiments based on syngeneic mouse models of colon cancer in BALB/c mice and chemically colon tumorigenesis. Flow cytometry, RNAseq, RT-qPCR, antibody-specific immune cell depletion, and Western blot were used to identify the immune cell type involved in the preventive and antitumor activity of H89. We demonstrated that H89 delays colon oncogenesis and prevents tumor growth. This latter effect seems to involve NK cells. H89 also inhibits colon tumor growth in a T-cell-dependent manner. Analysis of the immune landscape in the tumor microenvironment showed an increase of CD4⁺ Th1 cells and CD8⁺ cytotoxic T cells but a decrease of CD4⁺ T_reg cell infiltration. Mechanistically, we showed that H89 could promote naïve CD4⁺ T-cell differentiation into Th1, a decrease in T_reg differentiation, and an increase in CD8⁺ T-cell activation and cytotoxicity ex vivo. Furthermore, H89 induced overexpression of genes involved in antitumor immune response, such as IL-15RA, which depletion counteracts the antitumor effect of H89. We also found that H89 regulated Akt/PP2A pathway axis, involved in TCR and IL-15 signaling transduction. Our findings identify the H89 as a potential strategy for immune system activation leading to the prevention and treatment of CRC.

Ibrutinib in the Treatment of Solid Tumors: Current State of Knowledge and Future Directions

Bruton’s Tyrosine Kinase (BTK) is considered crucial in the activation and survival of both physiological and malignant B-cells. In recent years, ibrutinib, an oral BTK inhibitor, became a breakthrough therapy for hematological malignancies, such as chronic lymphocytic. However, ibrutinib’s feasibility might not end there. Several other kinases with established involvement with solid malignancies (i.e., EGFR, HER2) have been found to be inhibited by this agent. Recent discoveries indicate that BTK is a potential anti-solid tumor therapy target. Consequently, ibrutinib, a BTK-inhibitor, has been studied as a therapeutic option in solid malignancies. While most preclinical studies indicate ibrutinib to be an effective therapeutic option in some specific indications, such as NSCLC and breast cancer, clinical trials contradict these observations. Nevertheless, while ibrutinib failed as a monotherapy, it might become an interesting part of a multidrug regime: not only has a synergism between ibrutinib and other compounds, such as trametinib or dactolisib, been observed in vitro, but this BTK inhibitor has also been established as a radio- and chemosensitizer. This review aims to describe the milestones in translating BTK inhibitors to solid tumors in order to understand the future potential of this agent better.

Correlation Between TCF7+ T Cells and Prognosis of Patients With Oral Squamous Cell Carcinoma

Objective

To investigate whether TCF7⁺ T cells constitute an important factor to improve the existing postoperative prediction model for patients with oral squamous cell carcinoma.

Method

TCF7⁺ T cells were detected in the tissues of 167 OSCC patients by multiplex immunofluorescence. The percentage of TCF7⁺ T cells was transformed into a dichotomous variable, combined with the clinicopathological data for the OSCC patients, and then subjected to univariate and multivariate analyses. The derived independent predictors were then incorporated into risk models to analyze their relationship with the prognosis of patients.

Results

The high TCF7⁺ group had a better prognosis than the low TCF7⁺ group (OS: p<0.001; RFS: p<0.001). Univariate and multivariate analyses showed that TCF7⁺ T cells serve as an independent predictor of OSCC (univariate/multivariate analysis: p<0.001). In Cox risk progression models, inclusion of the TCF7⁺ T cell percentage improved the predictive accuracy of Grade and TNM stage (Grade-OS/RFS: p<0.001; TNM-OS/RFS: p<0.001; TNM+Grade-OS: p<0.001, TNM+Grade-RFS: p=0.004). Inclusion of the TCF7⁺ T cell percentage improved the clinical utility.

Conclusions

TCF7⁺ T cells can act as an independent predictor for postoperative OSCC patients. The inclusion of TCF7⁺ T cells improved the predictive accuracy and clinical utility of the nomograms to different degrees.

Triterpenoids of Rhus chinensis Supressed Colorectal Cancer Progress by Enhancing Antitumor Immunity and CD8 + T Cells Tumor Infiltration

The absence of CD8+ T cells in the tumor center has become a major obstacle in the immunotherapy of colorectal cancer. Therefore, new therapeutic strategies are urgently needed to promote the accumulation of CD8+ T cells in the tumor center. Previous studies have shown that triterpenoid of Rhus chinensis (TER) is involved in the proliferation and apoptosis of colorectal cancer cells, and can regulate their immune activity, but its mechanism needs to be further elucidated. In this study, the antitumor effect and adaptive immune response of TER on tumor-bearing mice were evaluated and compared with 5-fluorouracil. The results showed that TER could significantly inhibit tumor growth and prolong the survival time of tumor-bearing mice. The In Vivo studies have shown that TER can not only enhance antitumor immunity and promote the accumulation of CD8 + T cells to tumor sites, but also inhibit tumor progression by regulating the expression of PD-1 and PD-L1 and significantly reducing the mortality of mice. Our study demonstrated for the first time that TER has oncolytic effect, and recruited adaptive immune cells to enhance the efficacy of anti-PD-1/PD-L1 in colorectal cancer, which provides a potential therapeutic target for combined immunotherapy of colorectal cancer.

Characterization of the Immune Cell Infiltration Landscape of Thyroid Cancer for Improved Immunotherapy

Within the endocrine system, thyroid cancer (THCA) is the most typical malignant tumor. Tumor-infiltrating immune cells play vital roles in tumor progression, recurrence, metastasis as well as response to immunotherapy. However, THCA’s immune infiltrative landscape is still not clarified. Therefore, we utilized two statistical algorithms to investigate the immune cell infiltration (ICI) landscape of 505 THCA samples and defined three ICI immune subtypes. The ICI scores were calculated using principal-component analysis. Increased tumor mutation burden (TMB) and immune-related signaling pathways were associated to a high ICI score. The high ICI score group indicated a relatively longer overall survival (OS) than the low ICI score group. Most immune checkpoint-related and immune activation-related genes were considerably upregulated in the ICI high group, which indicates stronger immunogenicity and a greater likelihood of benefiting from immunotherapy. In two cohort studies of patients receiving immunotherapy, high-ICI-score group showed notable therapeutic effects and clinical advantages compared to those with lower ICI scores. These results demonstrate that ICI score acts as an effective prognostic indicator and predictor of response to immunotherapy.

CCR4 is a prognostic biomarker and correlated with immune infiltrates in head and neck squamous cell carcinoma

Background

Increased evidence has indicated that the tumour microenvironment plays an essential in the development, treatment and prognosis of head and neck squamous cell carcinoma (HNSC). Recent studies have indicated CC chemokine receptor 4 (CCR4) plays an essential role in tumor invasion and other adverse biological behavior. This study used data from the Cancer Genome Atlas (TCGA) database to explore the role of CCR4 in HNSC and its clinical significance.

Methods

The gene expression and clinical data of HNSC patients in the TCGA database were extracted. Gene Expression Profiling Interactive Analysis (GEPIA) was used to analyze the expression of CCR4 in tumor and non-tumor tissue. Kaplan-Meier survival analysis was used to analyze the relationship between CCR4 expression and overall survival rate (OS), disease-specific survival (DSS), and progression-free interval (PFI) in HNSC. A logistic regression model was used to analyze the relationships between various clinical factors and CCR4 expression. Gene Set Enrichment Analysis (GSEA) was used to explore the potential role of CCR4 in HNSC. Additionally, we explored the relationship between CCR4 and immune infiltration.

Results

The expression of CCR4 in HNSC was not significantly different from that in normal tissue. The expression level of CCR4 in wild-type TP53 was higher than that in mutant TP53. Cox regression analysis showed the expression level of CCR4 was related to the patient's tumor grade and Tumor-Node-Metastasis (TNM) stage. CCR4 expression level is an independent prognostic factor. CCR4 is positively correlated with immune infiltration and immune checkpoints expression levels. The results of GSEA revealed that the high CCR4 expression group genes were enriched in allograft rejection, inflammatory response, IL-6/JAK/STAT3 signaling, interferon gamma response, and KRAS signaling up. Low CCR4 expression group genes were enriched in oxidative phosphorylation, MYC targets v1, DNA repair, reactive oxygen species pathway, and P53 pathway. Further, our study indicated CCR4 can also predict the prognosis of radiotherapy patients.

Conclusions

Our study found that CCR4 was a prognostic marker related to HNSC immune infiltration, and patients with high expression of CCR4 had a better prognosis.

CXCR5+CD8+ T Cells Shape Antibody Responses In Vivo Following Protein Immunisation and Peripheral Viral Infection

Crosstalk between T and B cells is crucial for generating high-affinity, class-switched antibody responses. The roles of CD4⁺ T cells in this process have been well-characterised. In contrast, regulation of antibody responses by CD8⁺ T cells is significantly less defined. CD8⁺ T cells are principally recognised for eliciting cytotoxic responses in peripheral tissues and forming protective memory. However, recent findings have identified a novel population of effector CD8⁺ T cells that co-opt a differentiation program characteristic of CD4⁺ T follicular helper (Tfh) cells, upregulate the chemokine receptor CXCR5 and localise to B cell follicles. While it has been shown that CXCR5⁺CD8⁺ T cells mediate the removal of viral reservoirs in the context of follicular-trophic viral infections and maintain the response to chronic insults by virtue of progenitor/stem-like properties, it is not known if CXCR5⁺CD8⁺ T cells arise during acute peripheral challenges in the absence of follicular infection and whether they influence B cell responses in vivo in these settings. Using the ovalbumin-specific T cell receptor transgenic (OT-I) system in an adoptive transfer-immunisation/infection model, this study demonstrates that CXCR5⁺CD8⁺ T cells arise in response to protein immunisation and peripheral viral infection, displaying a follicular-homing phenotype, expression of cell surface molecules associated with Tfh cells and limited cytotoxic potential. Furthermore, studies assessing the B cell response in the presence of OT-I or Cxcr5^-/- OT-I cells revealed that CXCR5⁺CD8⁺ T cells shape the antibody response to protein immunisation and peripheral viral infection, promoting class switching to IgG2c in responding B cells. Overall, the results highlight a novel contribution of CD8⁺ T cells to antibody responses, expanding the functionality of the adaptive immune system.

CXCR5+CD8+ T cells: A Review of their Antibody Regulatory Functions and Clinical Correlations

CD8⁺ T cells have conventionally been studied in relationship to pathogen or tumor clearance. Recent reports have identified novel functions of CXCR5⁺CD8⁺ T cells that can home to lymphoid follicles, a key site of antibody production. In this review we provide an in-depth analysis of conflicting reports regarding the impact of CXCR5⁺CD8⁺ T cells on antibody production and examine the data supporting a role for antibody-enhancement (B cell "helper") and antibody-downregulation (antibody-suppressor) by CXCR5⁺CD8⁺ T cell subsets. CXCR5⁺CD8⁺ T cell molecular phenotypes are associated with CD8-mediated effector functions including distinct subsets that regulate antibody responses. Co-inhibitory molecule PD-1, among others, distinguish CXCR5⁺CD8⁺ T cell subsets. We also provide the first in-depth review of human CXCR5⁺CD8⁺ T cells in the context of clinical outcomes and discuss the potential utility of monitoring the quantity of peripheral blood or tissue infiltrating CXCR5⁺CD8⁺ T cells as a prognostic tool in multiple disease states.

Intratumoral CXCR5+CD8+T associates with favorable clinical outcomes and immunogenic contexture in gastric cancer

Studies that examined an association between CD8⁺T and prognosis in gastric cancer are inconsistent, and a distinct population of CXCR5⁺CD8⁺T associated with better overall survival has been reported among various malignancies. Here, we show that the abundance of intratumoral CXCR5⁺CD8⁺T cells is associated with better overall survival in patients with gastric cancer. Patients with TNM II + III gastric cancer with higher intratumoral CXCR5⁺CD8⁺T cell infiltration are more likely to benefit from adjuvant chemotherapy. Microsatellite-unstable and Epstein–Barr virus positive tumors are enriched with CXCR5⁺CD8⁺T cells. Gastric cancer infiltrating CXCR5⁺CD8⁺T cells represent a specific subtype of stem-like CD8⁺T with effector memory feature. Identification of the clinical significance and phenotype of gastric cancer infiltrating CXCR5⁺CD8⁺T provides a roadmap for patient stratification and trials of targeted therapies.

The prognostic value of tumor infiltrating lymphocytes in gastric cancer remains controversial. Here the authors show a consistent association between higher density of intratumoral CXCR5+CD8+ T cells and longer overall survival in four different cohorts of patients with gastric cancer.

Tumor cell PD-L1 expression is a strong predictor of unfavorable prognosis in immune checkpoint therapy-naive clear cell renal cell cancer

BACKGROUND

PD-L1 expression predicts response to immune checkpoint inhibitors in renal cell carcinomas (RCC), but has also been suggested to be linked to poor patient outcome.

METHODS

We analyzed PD-L1 in > 1400 RCC in a tissue microarray format by immunohistochemistry. Results were compared with histological tumor type, parameters of cancer aggressiveness, and intratumoral CD8⁺ cytotoxic cells.

RESULT

At a cut-off level of 5% PD-L1 positive tumor cells, PD-L1 positivity was seen in 6.3% of 633 clear cell RCC (ccRCC), 18.2% of 165 papillary RCC, 18.8% of 64 chromophobe RCC, and 41.7% of 103 oncocytomas. In ccRCC, PD-L1 positivity was significantly linked to high ISUP (p < 0.0001), Fuhrman (p < 0.0001), Thoenes grade (p < 0.0001), distant metastasis (p = 0.0042), short recurrence-free (p < 0.0001), and overall survival (p = 0.0002). Intratumoral CD8⁺ lymphocytes were more frequent in PD-L1 positive (1055 ± 109) than in PD-L1 negative ccRCC (407 ± 28; p < 0.0001). PD-L positive immune cells were seen in 8.2% of all RCC and 13.9% of papillary RCC. In ccRCC, PD-L1 positive immune cells were linked to high numbers of tumor-infiltrating CD8⁺ cells (p < 0.0001), high ISUP (p < 0.0001), Fuhrman (p = 0.0027), and Thoenes grade (p < 0.0001), and poor tumor-specific survival (p = 0.0280).

CONCLUSIONS

These data suggest that PD-L1 expression in highly immunogenic RCCs facilitates immune evasion and contributes to cancer aggressiveness.

The Dual Role of STAT1 in Ovarian Cancer: Insight Into Molecular Mechanisms and Application Potentials

The signal transducer and activator of transcription 1 (STAT1) is a transducer protein and acts as a transcription factor but its role in ovarian cancer (OC) is not completely understood. Practically, there are two-faced effects of STAT1 on tumorigenesis in different kinds of cancers. Existing evidence reveals that STAT1 has both tumor-suppressing and tumor-promoting functions involved in angiogenesis, cell proliferation, migration, invasion, apoptosis, drug resistance, stemness, and immune responses mainly through interacting and regulating target genes at multiple levels. The canonical STAT1 signaling pathway shows that STAT1 is phosphorylated and activated by the receptor-activated kinases such as Janus kinase in response to interferon stimulation. The STAT1 signaling can also be crosstalk with other signaling such as transforming growth factor-β signaling involved in cancer cell behavior. OC is often diagnosed at an advanced stage due to symptomless or atypical symptoms and the lack of effective detection at an early stage. Furthermore, patients with OC often develop chemoresistance and recurrence. This review focuses on the multi-faced role of STAT1 and highlights the molecular mechanisms and biological functions of STAT1 in OC.

CXCL13 shapes immunoactive tumor microenvironment and enhances the efficacy of PD-1 checkpoint blockade in high-grade serous ovarian cancer

BACKGROUND

Most patients with high-grade serous ovarian cancer (HGSC) lack an effective response to immune checkpoint blockade, highlighting the need for more knowledge about what is required for successful treatment. As follicular cytotoxic CXCR5⁺CD8⁺ T cells are maintained by reinvigoration by immune checkpoint blockade in tumors, we attempted to reveal the relationship between CXCR5⁺CD8⁺ T cells and the tumor microenvironment to predict immunotherapy responses in HGSC.

METHODS

264 patients with HGSC from two cohorts and 340 HGSC cases from The Cancer Genome Atlas cohort were enrolled. Ex vivo and in vivo studies were conducted with human HGSC tumors and murine tumor models. The spatial correlation between CXC-chemokine ligand 13 (CXCL13), CXCR5, CD8, and CD20 was evaluated by immunohistochemistry and immunofluorescence. Survival was compared between different subsets of patients using Kaplan-Meier analysis. The therapeutic effect of CXCL13 and programmed cell death-1 (PD-1) blockade was validated using human HGSC tumors and murine models.

RESULTS

High CXCL13 expression was associated with prolonged survival. Tumors with high CXCL13 expression exhibited increased infiltration of activated and CXCR5-expressing CD8⁺ T cells. Incubation with CXCL13 facilitated expansion and activation of CXCR5⁺CD8⁺ T cells ex vivo. CXCR5⁺CD8⁺ T cells appeared in closer proximity to CXCL13 in tumors and chemotaxis towards CXCL13 in vitro. The combination of CXCL13, CXCR5, and CD8⁺ T cells was an independent predictor for survival. In addition, CXCL13 was associated with clusters of CD20⁺ B cells. CD20⁺ B cells predicted better patient survival in the presence of CXCL13. Histological evaluation highlighted colocalization of CXCL13 with tertiary lymphoid structures (TLSs). TLSs carried prognostic benefit only in the presence of CXCL13. CXCL13 in combination with anti-PD-1 therapy retarded tumor growth in a CD8⁺ T-cell-dependent manner, resulting in increased infiltration of cytotoxic CD8⁺ T cells and CXCR5⁺CD8⁺ T cells.

CONCLUSIONS

These data define a critical role of CXCL13 in shaping antitumor microenvironment by facilitating the maintenance of CXCR5⁺CD8⁺ T cells in TLSs and support a clinical investigation for a combination of CXCL13 and PD-1 blockade therapy in HGSC.

Follicular cytotoxic CD8 T cells present high cytokine expression, and are more susceptible to Breg-mediated suppression in non-small cell lung cancer

Tumor-infiltrating CD8 T cells are instrumental to antitumor immunity. In this study, we found that a subset of CXCR5-expressing CD8 T cells, termed follicular cytotoxic T (Tfc) cells, potently infiltrated the untreated tumors from non-small cell lung cancer (NSCLC) patients. On average, Tfc cells represented 14% of total tumor-infiltrating CD8 T cells and 6.6% of total tumor-infiltrating lymphocytes. Upon antigenic stimulation, Tfc cells presented significantly higher degranulation and stronger release of proinflammatory cytokines, including IFNg, IL2, and TNF, and the pleiotropic cytokine IL10 than non-Tfc cells. However, the expression of granzyme B and perforin was significantly lower in Tfc cells than in non-Tfc CD8 T cells. B regulatory (Breg) cells could significantly suppress proinflammatory cytokine production in both Tfc cells and non-Tfc CD8 T cells, but in Tfc cells, a lower concentration was required. Moreover, Breg cells could significantly elevate IL10 expression by Tfc cells but could not affect IL-10 expression by non-Tfc CD8 T cells. The neutralization of IL10 significantly reduced the extent of Breg-mediated regulation. Together, this study demonstrated that Tfc cells represented a significant proportion of tumor-infiltrating CD8 T cells in lung carcinoma. These Tfc cells were different from non-Tfc CD8 T cells in terms of cytokine expression and granzyme and perforin release and were more susceptible to Breg-mediated suppression in an IL-10-dependent manner.

Resolving the Paradox of Colon Cancer Through the Integration of Genetics, Immunology, and the Microbiota

While colorectal cancers (CRC) are paradigmatic tumors invaded by effector memory lymphocytes, the mechanisms accounting for the relative resistance of MSI negative CRC to immunogenic cell death mediated by oxaliplatin and immune checkpoint inhibitors has remained an open conundrum. Here, we propose the viewpoint where its microenvironmental contexture could be explained -at least in part- by macroenvironmental cues constituted by the complex interplay between the epithelial barrier, its microbial ecosystem, and the local immune system. Taken together this dynamic ménage-à-trois offers novel coordinated actors of the humoral and cellular immune responses actionable to restore sensitivity to immune checkpoint inhibition. Solving this paradox involves breaking tolerance to crypt stem cells by inducing the immunogenic apoptosis of ileal cells in the context of an ileal microbiome shifted towards immunogenic bacteria using cytotoxicants. This manoeuver results in the elicitation of a productive Tfh and B cell dialogue in mesenteric lymph nodes culminating in tumor-specific memory CD8+ T cell responses sparing the normal epithelium.

CD8+ T Cell Infiltration Predicts Chemoradiosensitivity in Nasopharyngeal or Oropharyngeal Cancer

OBJECTIVES

Limited information exists regarding the associations between pre-existing immune parameters in the tumor immune microenvironment (TIM) and either chemoradiosensitivity or prognosis for patients with squamous cell carcinoma of the nasopharynx or oropharynx involving virus-related or nonvirus-related tumors.

STUDY DESIGN

Retrospective cohort study.

METHODS

We retrospectively reviewed 141 patients with EBV+, p16+, or EBV- and p16- statuses who are receiving chemoradiotherapy. We performed immunohistochemistry using pretreatment biopsy specimens to analyze the programed death ligand 1 (PD-L1) levels in tumor and immune cells and CD8+ tumor-infiltrating lymphocyte (TIL) density. We evaluated chemoradiosensitivity and prognosis with respect to these immune-related parameters.

RESULTS

Virus-related tumors showed associations with both PD-L1 expression and high CD8+ TIL density. Patients with higher CD8+ TIL density or greater numbers of PD-L1+ tumor and immune cells showed significant rates of favorable local recurrence-free survival (LRFS), progression-free survival (PFS), and overall survival (OS). Multivariate analyses demonstrated that higher CD8+ TIL density is an independent, significant, and favorable predictive factor for LRFS (P = .005) and OS (P = .003), although it is not a significant predictor of PFS (P = .077).

CONCLUSIONS

Higher CD8+ TIL density represents a useful and favorable biomarker of chemoradiosensitivity in patients receiving chemoradiotherapy for nasopharyngeal or oropharyngeal cancer.

LEVEL OF EVIDENCE

3 Laryngoscope, 131:E1179-E1189, 2021.

Identification and validation of an excellent prognosis subtype of muscle-invasive bladder cancer patients with intratumoral CXCR5+ CD8+ T cell abundance

Bladder cancer is the ninth most frequent-diagnosed disease worldwide, bearing high morbidity and mortality rates. Studies have shown that a particular population of CXCR5⁺CD8⁺ T cells was associated with superior prognosis in various tumor types, and yet its role in muscle-invasive bladder cancer (MIBC) remains unclear. In this study, 662 MIBC patients from 3 cohorts (Zhongshan Hospital, n = 141; Shanghai Cancer Center, n = 108; The Cancer Genome Atlas, n = 403) were analyzed retrospectively. 11 fresh resected samples of MIBC were examined to characterize the phenotype of CXCR5⁺CD8⁺ T cells and 402 MIBC patients from TCGA were applied for bioinformatics analysis. It was explored that the abundance of intratumoral CXCR5⁺CD8⁺ T cells indicated superior overall survival and disease-free survival. Patients with a higher infiltration of CXCR5⁺CD8⁺ T cells in tumor tissue benefit more from adjuvant chemotherapy (ACT). Intratumoral CXCR5⁺CD8⁺ T cells displayed cytolytic and self-renewal features. Remarkably, CXCR5⁺CD8⁺ T cells were mainly presented in the basal and stromal-rich subtypes of MIBC and tumors with enriched CXCR5⁺CD8⁺ T cells showed limited FGFR3 signaling signature and activated immunotherapeutic and EGFR associated pathway. In conclusion, we identified an excellent prognosis and ACT sensitive subtype of MIBC with intratumoral CXCR5⁺CD8⁺ T cell abundance. Tumors with high density of CXCR5⁺CD8⁺ T cells possessed potential sensitivity to immunotherapy and EGFR-targeted therapy. CXCR5⁺CD8⁺ T cells provide a new potential biomarker as well as a therapeutic target in MIBC.

Predictive Value of Postoperative Peripheral CD4+ T Cells Percentage in Stage I-III Colorectal Cancer: A Retrospective Multicenter Cohort Study of 1028 Subjects

Objective

Association of postoperative peripheral CD4+ T cells percentage and recurrence in colorectal cancer (CRC) remains to be explored. Therefore, we aimed to investigate the association between the postoperative peripheral CD4+ T cells percentage and recurrence in CRC patients.

Patients and Methods

Consecutive stage I–III CRC patients without neoadjuvant treatment undergoing curative resection from January 2010 to July 2016 were identified in two Chinese centers. The association between the postoperative CD4+ T cells percentage, measured within 12 weeks after surgery, and recurrence-free survival (RFS) was analyzed.

Results

A total of 1028 patients were identified (training set: 913 patients, validation set: 115 patients). In the training set, the 5-year RFS rate of the 441 patients with abnormal postoperative CD4+ T cells percentage was significantly lower than that of those with normal percentage (70.3% [95% CI 65.7–75.2%] vs 77.6% [95% CI 73.7–81.7%] and unadjusted hazard ratio [HR] 1.36 [95% CI 1.04–1.78], P=0.02). The result was confirmed in the validation set. Multivariable Cox regression analysis demonstrated that the association of postoperative CD4+ T cells percentage with 5-year RFS was independent both in the training and validation sets. In propensity score matching analysis, patients with normal postoperative CD4+ T cells percentage were found to have a favourable response to adjuvant chemotherapy (HR 0.29 [95% CI 0.12–0.72], P=0.008).

Conclusion

Postoperative peripheral CD4+ T cells percentage is a predictive biomarker for RFS in patients with CRC, which can identify those who will benefit from adjuvant chemotherapy.

Cancer and HIV-1 Infection: Patterns of Chronic Antigen Exposure

The main role of the human immune system is to eliminate cells presenting foreign antigens and abnormal patterns, while maintaining self-tolerance. However, when facing highly variable pathogens or antigens very similar to self-antigens, this system can fail in completely eliminating the anomalies, leading to the establishment of chronic pathologies. Prototypical examples of immune system defeat are cancer and Human Immunodeficiency Virus-1 (HIV-1) infection. In both conditions, the immune system is persistently exposed to antigens leading to systemic inflammation, lack of generation of long-term memory and exhaustion of effector cells. This triggers a negative feedback loop where effector cells are unable to resolve the pathology and cannot be replaced due to the lack of a pool of undifferentiated, self-renewing memory T cells. In addition, in an attempt to reduce tissue damage due to chronic inflammation, antigen presenting cells and myeloid components of the immune system activate systemic regulatory and tolerogenic programs. Beside these homologies shared between cancer and HIV-1 infection, the immune system can be shaped differently depending on the type and distribution of the eliciting antigens with ultimate consequences at the phenotypic and functional level of immune exhaustion. T cell differentiation, functionality, cytotoxic potential and proliferation reserve, immune-cell polarization, upregulation of negative regulators (immune checkpoint molecules) are indeed directly linked to the quantitative and qualitative differences in priming and recalling conditions. Better understanding of distinct mechanisms and functional consequences underlying disease-specific immune cell dysfunction will contribute to further improve and personalize immunotherapy. In the present review, we describe relevant players of immune cell exhaustion in cancer and HIV-1 infection, and enumerate the best-defined hallmarks of T cell dysfunction. Moreover, we highlight shared and divergent aspects of T cell exhaustion and T cell activation to the best of current knowledge.

Colibactin-positive Escherichia coli induce a procarcinogenic immune environment leading to immunotherapy resistance in colorectal cancer

Colibactin-producing E. coli (CoPEC) are frequently detected in colorectal cancer (CRC) and exhibit procarcinogenic properties. Because increasing evidence show the role of immune environment and especially of antitumor T-cells in CRC development, we investigated the impact of CoPEC on these cells in human CRC and in the APC^Min/+ mice colon. T-cell density was evaluated by immunohistochemistry in human tumors known for their CoPEC status. APC^min/+ mice were chronically infected with a CoPEC strain (11G5). Immune cells (neutrophils and T-cell populations) were then quantified by immunofluorescent staining of the colon. The quantification of lymphoid populations was also performed in the mesenteric lymph nodes (MLNs). Here, we show that the colonization of CRC patients by CoPEC is associated with a decrease of tumor-infiltrating T lymphocytes (CD3⁺ T-cells). Similarly, we demonstrated, in mice, that CoPEC chronic infection decreases CD3⁺ and CD8⁺ T-cells and increases colonic inflammation. In addition, we noticed a significant decrease in antitumor T-cells in the MLNs of CoPEC-infected mice compared to that of controls. Moreover, we show that CoPEC infection decreases the antimouse PD-1 immunotherapy efficacy in MC38 tumor model. Our findings suggest that CoPEC could promote a procarcinogenic immune environment through impairment of antitumor T-cell response, leading to tumoral resistance to immunotherapy. CoPEC could thus be a new biomarker predicting the anti-PD-1 response in CRC.

CXC Chemokine Receptors in the Tumor Microenvironment and an Update of Antagonist Development

Chemokine receptors, a diverse group within the seven-transmembrane G protein-coupled receptor superfamily, are frequently overexpressed in malignant tumors. Ligand binding activates multiple downstream signal transduction cascades that drive tumor growth and metastasis, resulting in poor clinical outcome. These receptors are thus considered promising targets for anti-tumor therapy. This article reviews recent studies on the expression and function of CXC chemokine receptors in various tumor microenvironments and recent developments in cancer therapy using CXC chemokine receptor antagonists.

Control of Lymphocyte Fate, Infection, and Tumor Immunity by TCF-1

T cell factor-1 (TCF-1), encoded by Tcf7, is a transcription factor and histone deacetylase (HDAC) essential for commitment to both the T cell and the innate lymphoid cell (ILC) lineages in mammals. In this review, we discuss the multifunctional role of TCF-1 in establishing these lineages and the requirement for TCF-1 throughout lineage differentiation and maintenance of lineage stability. We highlight recent reports showing promise for TCF-1 as a novel biomarker to identify recently characterized subsets of exhausted CD8⁺ T cells that may help to predict patient responses to immune checkpoint blockade (ICB).

CD8+CXCR5+T cells infiltrating hepatocellular carcinomas are activated and predictive of a better prognosis

CD8+ T cells are thought to be the primary cytotoxic lymphocytes exerting antitumor effects. However, few studies have focused on the antitumor effects of CD8+ T cell-mediated humoral immunity or on interactions between CD8+ T cells and B cells in hepatocellular carcinoma (HCC). We found that the frequency of IL-21-producing CD8+CXCR5+ T cells was higher in HCC tumor tissue than in peritumoral tissue or peripheral blood from the same patients or in blood from healthy donors. Moreover, CD8+CXCR5+ T cells migrated in response to supernatants from primary HCC (HCC-SN) cells, and HCC-SN cells also powerfully induced CXCR5 expression in CD8+ T cells and IL-21 expression in CD8+CXCR5+ T cells. CD8+CXCR5+ T cells from HCC patients, but not those from healthy individuals, stimulated CD19+ B cells to differentiate into IgG-producing plasmablasts. These findings reveal that CD8+CXCR5+ T cells strongly infiltrate HCC tumors, and their infiltration is predictive of a better prognosis. Surprisingly, moreover, CD8+CXCR5+ T cells produced IL-21, which induced B cells to differentiate into IgG-producing plasmablasts and to play a key role in humoral immunity in HCC.

T cell immune response within B-cell follicles

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 CXCR5^-CD8⁺ 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.

CXCR5+ CD8 T Cells: Protective or Pathogenic?

CD8 T cells are infrequently considered part of germinal center reactions. Yet, a distinct CXCR5+ CD8 T cell subset identified within the B cell follicle and germinal center in situations of chronic antigen has recently been defined. CXCR5+ CD8 T cells maintain transcriptional and phenotypic features consistent with the CD8 T cell nomenclature of a non-exhausted, effector memory population. CD8 T cell localization to the B cell follicle suggests a functional profile similar to CD4 T follicular helper cells that are licensed to promote B cell responses. The functional mechanisms defined under different immune settings, while largely similar, differentially control disease pathogenesis. CXCR5+ CD8 T cells control viral load during infection, and also promote antibody-mediated autoimmune disease progression. The existence of this novel CXCR5+ CD8 T cell subset in human and murine models of disease may provide a paradigm shift in our understanding of germinal center reactions.

CXCL13/CXCR5 signaling axis in cancer

The tumor microenvironment comprises stromal and tumor cells which interact with each other through complex cross-talks that are mediated by a variety of growth factors, cytokines, and chemokines. The chemokine ligand 13 (CXCL13) and its chemokine receptor 5 (CXCR5) are among the key chemotactic factors which play crucial roles in deriving cancer cell biology. CXCL13/CXCR5 signaling axis makes pivotal contributions to the development and progression of several human cancers. In this review, we discuss how CXCL13/CXCR5 signaling modulates cancer cell ability to grow, proliferate, invade, and metastasize. Furthermore, we also discuss the preliminary evidence on context-dependent functioning of this axis within the tumor-immune microenvironment, thus, highlighting its potential dichotomy with respect to anticancer immunity and cancer immune-evasion mechanisms. At the end, we briefly shed light on the therapeutic potential or implications of targeting CXCL13/CXCR5 axis within the tumor microenvironment.

A Portrait of CXCR5+ Follicular Cytotoxic CD8+ T cells

CD8⁺ T cells differentiate into multiple effector and memory subsets to carry out immune clearance of infected and cancerous cells and provide long-term protection. Recent research identified a CXCR5⁺Tcf1⁺Tim-3^- subset that localizes in, or proximal to, B cell follicles in secondary lymphoid organs of mice, non-human primates, and humans, hereby termed follicular cytotoxic T (T_FC) cells. With remarkable similarity to follicular helper T (T_FH) cells, T_FC differentiation is dependent on transcription factors E2A, Bcl6, and Tcf1, but inhibited by other regulators, including Blimp1, Id2, and Id3. This review summarizes the phenotype, function, and differentiation of this new subset. Owing to its follicular location and self-renewal capability, we propose immunotherapeutic strategies to target T_FC cells to potentially treat certain cancers and chronic infections such as HIV-1.