Both CD4+ FoxP3+ and CD4+ FoxP3- T cells from patients with B-cell malignancy express cytolytic markers and kill autologous leukaemic B cells in vitro

CXCR6 defines therapeutic subtypes of CD4+ cytotoxic T cell lineage for adoptive cell transfer therapy in pediatric B cell acute lymphoblastic leukemia

The potential of cytotoxic CD4+ T cells and tissue resident memory T cells (Trm) in achieving adult leukemia remission have been highlighted [1,2]. We hypothesized that CXCR6 could serve as a marker for cytotoxic CD4+ Trm cells in the bone marrow (BM) of pediatric B-ALL patients. Flow cytometry (FCM) and published single cell RNA sequencing (scRNA-seq) datasets were employed to characterize CXCR6+CD4+ T cells in the BM and peripheral blood (PB) of pediatric B-ALL patients and healthy donors. FCM, scRNA-seq and co-culture were utilized to explore the cytotoxicity of CXCR6+CD4+ T cells in vitro based on in vitro induction of CXCR6+CD4+ T cells using tumor antigens and peripheral blood mononuclear cells (PBMCs). The ssGSEA based on the cell markers identified according to the in vivo scRNA-seq data, the TARGET-ALL-P2 datasets, and integrated machine learning algorithm were employed to figure out the key cells with prognostic values, followed by simulation of adoptive cell transfer therapy (ACT). Integrated machine learning identified the high-risk cells for disease free survival, and overall survival, while simulation of ACT therapy using CXCR6+CD4+T cells indicated that CXCR6+CD4+ T cells could remodel the bone marrow microenvironments towards anti-tumor. Based on the expression of genes involved in formation of resident memory T cells, CXCR6 is not a marker of resident memory CD4+T cells but defines therapeutic subtypes of CD4+ cytotoxic T cell lineage for pediatric B-ALL.

Characterization of post-vaccination SARS-CoV-2 T cell subtypes in patients with different hematologic malignancies and treatments

Background

To evaluate the benefits of SARS-CoV-2 vaccination in cancer patients it is relevant to understand the adaptive immune response elicited after vaccination. Patients affected by hematologic malignancies are frequently immune-compromised and show a decreased seroconversion rate compared to other cancer patients or controls. Therefore, vaccine-induced cellular immune responses in these patients might have an important protective role and need a detailed evaluation.

Methods

Certain T cell subtypes (CD4, CD8, Tfh, γδT), including cell functionality as indicated by cytokine secretion (IFN, TNF) and expression of activation markers (CD69, CD154) were assessed via multi-parameter flow cytometry in hematologic malignancy patients (N=12) and healthy controls (N=12) after a second SARS-CoV-2 vaccine dose. The PBMC of post-vaccination samples were stimulated with a spike-peptide pool (S-Peptides) of SARS-CoV-2, with CD3/CD28, with a pool of peptides from the cytomegalovirus, Epstein-Barr virus and influenza A virus (CEF-Peptides) or left unstimulated. Furthermore, the concentration of spike-specific antibodies has been analyzed in patients.

Results

Our results indicate that hematologic malignancy patients developed a robust cellular immune response to SARS-CoV-2 vaccination comparable to that of healthy controls, and for certain T cell subtypes even higher. The most reactive T cells to SARS-CoV-2 spike peptides belonged to the CD4 and Tfh cell compartment, being median (IQR), 3.39 (1.41-5.92) and 2.12 (0.55-4.14) as a percentage of IFN- and TNF-producing Tfh cells in patients. In this regard, the immunomodulatory treatment of patients before the vaccination period seems important as it was strongly associated with a higher percentage of activated CD4 and Tfh cells. SARS-CoV-2- and CEF-specific T cell responses significantly correlated with each other. Compared to lymphoma patients, myeloma patients had an increased percentage of SARS-CoV-2-specific Tfh cells. T-SNE analysis revealed higher frequencies of γδT cells in patients compared to controls, especially in myeloma patients. In general, after vaccination, SARS-CoV-2-specific T cells were also detectable in patients without seroconversion.

Conclusion

Hematologic malignancy patients are capable of developing a SARS-CoV-2-specific CD4 and Tfh cellular immune response after vaccination, and certain immunomodulatory therapies in the period before vaccination might increase the antigen-specific immune response. A proper response to recall antigens (e.g., CEF-Peptides) reflects immune cellular functionality and might be predictive for generating a newly induced antigen-specific immune response as is expected after SARS-CoV-2 vaccination.

Regulatory T cells (Tregs) in lymphoid malignancies and the impact of novel therapies

Regulatory T cells (Tregs) are responsible for maintaining immune homeostasis by controlling immune responses. They can be characterized by concomitant expression of FoxP3, CD25 and inhibitory receptors such as PD-1 and CTLA-4. Tregs are key players in preventing autoimmunity and are dysregulated in cancer, where they facilitate tumor immune escape. B-cell lymphoid malignancies are a group of diseases with heterogenous molecular characteristics and clinical course. Treg levels are increased in patients with B-cell lymphoid malignancies and correlate with clinical outcomes. In this review, we discuss studies investigating Treg immunobiology in B-cell lymphoid malignancies, focusing on clinical correlations, mechanisms of accumulation, phenotype, and function. Overarching trends suggest that Tregs can be induced directly by tumor cells and recruited to the tumor microenvironment where they suppress antitumor immunity to facilitate disease progression. Further, we highlight studies showing that Tregs can be modulated by novel therapeutic agents such as immune checkpoint blockade and targeted therapies. Treg disruption by novel therapeutics may beneficially restore immune competence but has been associated with occurrence of adverse events. Strategies to achieve balance between these two outcomes will be paramount in the future to improve therapeutic efficacy and safety.

Emerging Canonical and Non-Canonical Roles of Granzyme B in Health and Disease

The Granzyme (Gzm) family has classically been recognized as a cytotoxic tool utilized by cytotoxic T lymphocytes (CTL) and natural killer (NK) cells to illicit cell death to infected and cancerous cells. Their importance is established based on evidence showing that deficiencies in these cell death executors result in defective immune responses. Recent findings have shown the importance of Granzyme B (GzmB) in regulatory immune cells, which may contribute to tumor growth and immune evasion during cancer development. Other studies have shown that members of the Gzm family are important for biological processes such as extracellular matrix remodeling, angiogenesis and organized vascular degradation. With this growing body of evidence, it is becoming more important to understand the broader function of Gzm's rather than a specific executor of cell death, and we should be aware of the many alternative roles that Gzm's play in physiological and pathological conditions. Therefore, we review the classical as well as novel non-canonical functions of GzmB and discuss approaches to utilize these new findings to address current gaps in our understanding of the immune system and tissue development.

The prognostic significance of immune checkpoint receptor expression in patients with lymphoma: Association with disease status and clinical outcomes

INTRODUCTION

Little is known about the expression of immune checkpoint receptors in the peripheral blood of lymphoma patients. Herein, we assessed the expression of inhibitory checkpoint receptors, including CTLA-4, PD-1/PDL-1, LAG-3, and TIM-3 in the peripheral blood of lymphoma patients and its correlation with the clinical outcomes of patients. Therefore, 47 classical Hodgkin lymphoma (cHL), 48 non-Hodgkin lymphoma patients with diffuse large B-cell lymphoma (DLBCL) subtype, and 30 healthy controls were recruited.

METHODS

The expression of inhibitory receptors was evaluated using SYBR Green real-time PCR method.

RESULTS

CTLA-4, LAG-3, and TIM-3 genes were significantly upregulated in both cHL and DLBCL patients compared to the healthy controls. In addition, the level of these molecules was differentially expressed in cHL and DLBCL patients at different disease phases compared to the healthy controls. The CTLA-4 gene was highly expressed in newly diagnosed (ND) cHL patients compared to the relapsed ones. Relapsed DLBCL patients had significantly increased LAG-3 expression compared to patients at remission, as well as ND patients. Regarding cHL patients, high CTLA-4 expression was correlated with low lactate dehydrogenase level and better performance status, whereas the level of LAG-3 was significantly elevated in patients with poor performance status. Lower initial PD-1 expression was associated with improved disease-free survival in cHL patients.

CONCLUSIONS

Inhibitory immune checkpoint receptors are aberrantly expressed in the peripheral blood of cHL and DLBCL patients in which high LAG-3 in DLBCL patients and PD-1/LAG-3 in cHL patients are associated with relapse occurrence and worse prognosis, respectively.

The PD-1/PD-L1 Checkpoint in Normal Germinal Centers and Diffuse Large B-Cell Lymphomas

Besides a recognized role of PD-1/PD-L1 checkpoint in anti-tumour immune evasion, there is accumulating evidence that PD-1/PD-L1 interactions between B and T cells also play an important role in normal germinal center (GC) reactions. Even when smaller in number, T follicular helper cells (TFH) and regulatory T (TFR) or B (Breg) cells are involved in positive selection of GC B cells and may result critical in the lymphoma microenvironment. Here, we discuss a role of PD-1/PD-L1 during tumour evolution in diffuse large B cell lymphoma (DLBCL), a paradigm of GC-derived lymphomagenesis. We depict a progression model, in two phases, where malignant B cells take advantage of positive selection signals derived from correct antigen-presentation and PD-1/PD-L1 inter-cellular crosstalks to survive and initiate tumour expansion. Later, a constant pressure for the accumulation of genetic/epigenetic alterations facilitates that DLBCL cells exhibit higher PD-L1 levels and capacity to secrete IL-10, resembling Breg-like features. As a result, a complex immunosuppressive microenvironment is established where DLBCL cells sustain proliferation and survival by impairing regulatory control of TFR cells and limiting IL-21-mediated anti-tumour functions of TFH cells and maximize the use of PD-1/PD-L1 signaling to escape from CD8+ cytotoxic activity. Integration of these molecular and cellular addictions into a framework may contribute to the better understanding of the lymphoma microenvironment and contribute to the rationale for novel PD-1/PD-L1-based combinational immunotherapies in DLBCL.

EOMES and IL-10 regulate antitumor activity of T regulatory type 1 CD4+ T cells in chronic lymphocytic leukemia

The transcription factor eomesodermin (EOMES) promotes interleukin (IL)-10 expression in CD4+ T cells, which has been linked to immunosuppressive and cytotoxic activities. We detected cytotoxic, programmed cell death protein-1 (PD-1) and EOMES co-expressing CD4+ T cells in lymph nodes (LNs) of patients with chronic lymphocytic leukemia (CLL) or diffuse large B-cell lymphoma. Transcriptome and flow cytometry analyses revealed that EOMES does not only drive IL-10 expression, but rather controls a unique transcriptional signature in CD4+ T cells, that is enriched in genes typical for T regulatory type 1 (TR1) cells. The TR1 cell identity of these CD4+ T cells was supported by their expression of interferon gamma and IL-10, as well as inhibitory receptors including PD-1. TR1 cells with cytotoxic capacity accumulate also in Eµ-TCL1 mice that develop CLL-like disease. Whereas wild-type CD4+ T cells control TCL1 leukemia development after adoptive transfer in leukopenic Rag2-/- mice, EOMES-deficient CD4+ T cells failed to do so. We further show that TR1 cell-mediated control of TCL1 leukemia requires IL-10 receptor (IL-10R) signaling, as Il10rb-deficient CD4+ T cells showed impaired antileukemia activity. Altogether, our data demonstrate that EOMES is indispensable for the development of IL-10-expressing, cytotoxic TR1 cells, which accumulate in LNs of CLL patients and control TCL1 leukemia in mice in an IL-10R-dependent manner.

Understanding the Immune-Stroma Microenvironment in B Cell Malignancies for Effective Immunotherapy

Cancers, including lymphomas, develop in complex tissue environments where malignant cells actively promote the creation of a pro-tumoral niche that suppresses effective anti-tumor effector T cell responses. Research is revealing that the tumor microenvironment (TME) differs between different types of lymphoma, covering inflamed environments, as exemplified by Hodgkin lymphoma, to non-inflamed TMEs as seen in chronic lymphocytic leukemia (CLL) or diffuse-large B-cell lymphoma (DLBCL). In this review we consider how T cells and interferon-driven inflammatory signaling contribute to the regulation of anti-tumor immune responses, as well as sensitivity to anti-PD-1 immune checkpoint blockade immunotherapy. We discuss tumor intrinsic and extrinsic mechanisms critical to anti-tumor immune responses, as well as sensitivity to immunotherapies, before adding an additional layer of complexity within the TME: the immunoregulatory role of non-hematopoietic stromal cells that co-evolve with tumors. Studying the intricate interactions between the immune-stroma lymphoma TME should help to design next-generation immunotherapies and combination treatment strategies to overcome complex TME-driven immune suppression.

Immune Dysfunctions and Immune-Based Therapeutic Interventions in Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is a B-cell malignancy characterized by a wide range of tumor-induced alterations, which affect both the innate and adaptive arms of the immune response, and accumulate during disease progression. In recent years, the development of targeted therapies, such as the B-cell receptor signaling inhibitors and the Bcl-2 protein inhibitor venetoclax, has dramatically changed the treatment landscape of CLL. Despite their remarkable anti-tumor activity, targeted agents have some limitations, which include the development of drug resistance mechanisms and the inferior efficacy observed in high-risk patients. Therefore, additional treatments are necessary to obtain deeper responses and overcome drug resistance. Allogeneic hematopoietic stem cell transplantation (HSCT), which exploits immune-mediated graft-versus-leukemia effect to eradicate tumor cells, currently represents the only potentially curative therapeutic option for CLL patients. However, due to its potential toxicities, HSCT can be offered only to a restricted number of younger and fit patients. The growing understanding of the complex interplay between tumor cells and the immune system, which is responsible for immune escape mechanisms and tumor progression, has paved the way for the development of novel immune-based strategies. Despite promising preclinical observations, results from pilot clinical studies exploring the safety and efficacy of novel immune-based therapies have been sometimes suboptimal in terms of long-term tumor control. Therefore, further advances to improve their efficacy are needed. In this context, possible approaches include an earlier timing of immunotherapy within the treatment sequencing, as well as the possibility to improve the efficacy of immunotherapeutic agents by administering them in combination with other anti-tumor drugs. In this review, we will provide a comprehensive overview of main immune defects affecting patients with CLL, also describing the complex networks leading to immune evasion and tumor progression. From the therapeutic standpoint, we will go through the evolution of immune-based therapeutic approaches over time, including i) agents with broad immunomodulatory effects, such as immunomodulatory drugs, ii) currently approved and next-generation monoclonal antibodies, and iii) immunotherapeutic strategies aiming at activating or administering immune effector cells specifically targeting leukemic cells (e.g. bi-or tri-specific antibodies, tumor vaccines, chimeric antigen receptor T cells, and checkpoint inhibitors).

Prognostic role of regulatory T cells in lymphoma: a systematic review and meta-analysis

PURPOSE

The regulatory T cells (Tregs) are a subpopulation of lymphocytes that suppress the immune responses. The prognostic value of Tregs in lymphoma patients remains controversial. Thus, we conducted this meta-analysis to clarify the role of Tregs in the prognosis of lymphoma patients.

METHODS

We searched PubMed, Embase, and Web of Science to obtain eligible studies that evaluated the prognostic factor of Tregs for lymphoma patients. Hazards ratios (HRs) with the matching 95% confidence intervals (95%CIs) were merged to estimate the prognostic value of Tregs.

RESULTS

We finally retrieved 23 eligible studies, including a total of 2269 patients. The overall pooled analysis on all types of lymphomas showed that Tregs had a significantly positive association with prolonged overall survival (OS) (HR = 0.633, 95% CI 0.528-0.758) and progression-free survival (PFS) (HR = 0.451, 95% CI 0.261-0.779). Subgroup analysis indicated that high Tregs were significantly correlated with longer OS in Hodgkin lymphoma, diffuse large B cell lymphoma, and natural killer/T cell lymphoma. However, there was no significant association of Tregs with T cell lymphoma and follicular lymphoma.

CONCLUSIONS

Increased Tregs indicates a better prognosis for patients with lymphoma. Tregs could be used as a valuable prognostic biomarker of lymphoma patients.

Higher infiltration of intratumoral CD25+ FOXP3+ lymphocytes correlates with a favorable prognosis in patients with diffuse large B-cell lymphoma

Regulatory T-cells (Tregs) play an important role in cancer immunity but their prognostic impact is controversial in diffuse large B-cell lymphoma (DLBCL). Intratumoral Tregs in DLBCL (n = 70) were evaluated by double-stained CD25 and FOXP3 lymphocytes in formalin-fixed paraffin-embedded tissues, and correlated with clinicopathologic features. We found that increased numbers of intratumoral FOXP3+ lymphocytes (>2.4/HPF) and CD25 + FOXP3+ lymphocytes (>0.8/HPF) are favorable prognosticators (p = .004 and p < .001, respectively) in DLBCL patients, along with age <70 years, stage I-II disease, normal serum LDH level and low IPI scores (p < .001, .002, .002, and <.001, respectively). On multivariate analyses, a higher number of CD25 + FOXP3+ lymphocytes retained prognostic significance (p = .040). Interestingly, higher Treg infiltration correlated with increased infiltration by cytotoxic T-lymphocytes (γ = 0.294, p = .038) and nodal location (γ = 0.390, p = .004), but not with infiltration by CD123+ plasmacytoid dendritic cells, which were reported to induce Tregs with immune tolerance. Therefore, congruent with literature meta-analyses, higher intratumoral CD25 + FOXP3+ lymphocytes have a beneficial impact on DLBCL.

T-cells in chronic lymphocytic leukemia: Guardians or drivers of disease?

Chronic lymphocytic leukemia (CLL) is a B-cell malignancy, which is associated with profound alterations and defects in the immune system and a prevalent dependency on the microenvironmental niche. An abnormal T-cell compartment in the blood of CLL patients was already reported 40 years ago. Since then, our knowledge of T-cell characteristics in CLL has grown steadily, but the question of whether T-cells act as pro-tumoral bystander cells or possess anti-tumoral activity is still under debate. Increased numbers of CD4+ T-helper cell subsets are present in the blood of CLL patients, and T-helper cell cytokines have been shown to stimulate CLL cell survival and proliferation in vitro. In line with this, survival and growth of CLL cells in murine xenograft models have been shown to rely on activated CD4+ T-cells. This led to the hypothesis that T-cells are tumor-supportive in CLL. In recent years, evidence for an enrichment of antigen-experienced CD8+ T-cells in CLL has accumulated, and these cells have been shown to control leukemia in a CLL mouse model. Based on this, it was suggested that CD8+ T-cells recognize CLL-specific antigens and exert an anti-leukemia function. As described for other cancer entities, T-cells in CLL express multiple inhibitory receptors, such as PD-1, and lose their functional capacity, leading to an exhaustion phenotype which has been shown to be more severe in T-cells from secondary lymphoid organs compared with peripheral blood. This exhausted phenotype has been suggested to be causative for the poor response of CLL patients to CAR T-cell therapies. In addition, T-cells have been shown to be affected by drugs that are used to treat CLL, which likely impacts therapy response. This review provides an overview of the current knowledge about alterations of T-cells in CLL, including their distribution, function, and exhaustion state in blood and lymphoid organs, and touches also on the topic of how CLL drugs impact on the T-cell compartment and recent results of T-cell-based immunotherapy. We will discuss potential pathological roles of T-cell subsets in CLL and address the question of whether they foster progression or control of disease.

Regulation of CD4+CD25+FOXP3+ cells in Pediatric Acute Lymphoblastic Leukemia (ALL): Implication of cytokines and miRNAs

Regulatory T cells (Tregs) is one of the immunosuppressive subsets of CD4⁺ T cells characterized by transcription factor forkhead box protein P3 (FOXP3) expression which are involved in tumor development and progression. Identification of the factors that influence Treg cell function is extremely important. Our current study aimed to evaluate the frequency of Treg cells, cytokine secretion and the expression of microRNAs (miRNAs) in pediatric acute lymphoblastic leukemia (ALL) patients. The frequency of CD3⁺, CD4⁺ and CD4⁺CD25⁺FOXP3⁺ Treg was assessed by flow cytometry in 43 ALL patients versus 42 controls. Plasma levels of IL-10, transcription factor β (TGF-β), IL-6, IL-17, IL-23 and tumor necrosis factor (TNF-α) were measured by Enzyme-linked immunosorbent assay (ELISA). miR-21, miR-24, miR-26a, miR133b, miR-148a and miR-155 expression were analyzed using quantitative real-time polymerase chain reaction (qRT-PCR). A slight insignificant increase in Treg cells in ALL patients compared to controls was observed. There was a significant elevation in IL-10 (p < 0.05), IL-6 (p < 0.01), IL-23 (p < 0.05) and TNF-α (p < 0.01) in ALL patients compared with controls. Meanwhile, a significant reduction in TGF-β (p < 0.001) was recorded. A slight insignificant decrease in IL-17 in ALL patients was observed.ALL patients showed a significant increase in miR-21 (p < 0.05), miR-148a (p < 0.01), miR-24 (p < 0.05) and a significant reduction in miR-155 (p < 0.01). In conclusion, the slight change in Treg cells frequency and alteration in related cytokines could possibly involve in the pathogenesis of ALL. Dysregulated miRNAs, as a regulatory mechanism of epigenetics, might contribute to these observed results. Further researches are required to confirm our interesting findings.

Aberrant peripheral blood CD4+ CD25+ FOXP3+ regulatory T cells/T helper-17 number is associated with the outcome of patients with lymphoma

Little is known about the clinical significance of the peripheral blood CD4⁺ CD25⁺ FOXP3⁺ regulatory T cells (Tregs) and T helper-17 (Th17) cells in lymphoma patients. In this study, the prognostic and clinical significance of peripheral blood Tregs and Th17 cells were evaluated in lymphoma patients during different phases. The frequency of Tregs and Th17 lymphocytes was measured by flow cytometry method in 47 classical Hodgkin's lymphoma (cHL) and 48 diffuse large B cell lymphoma (DLBCL) patients. Our results showed that the frequency of Tregs and absolute Treg count was significantly reduced in relapsed patients compared to patients at the remission phase, as well as with newly diagnosed untreated patients in both groups. Patients who reached complete remission had elevated frequency of CD4⁺ FOXP3⁺ lymphocytes, Tregs, absolute Treg count, Treg/CD4 and Treg/Th17 ratio in the cHL group and CD4⁺ CD25⁺ cells in DLBCL group. The frequency of Tregs, absolute Treg count and Treg/Th17 ratio in cHL patients and CD4⁺ FOXP3⁺ and CD4⁺ CD25⁺ cells in DLBCL patients positively associated with survival rate. Moreover, the percentage of Tregs and absolute Treg count positively correlated with white blood cell, platelet count and ESR level in cHL patients and with white blood cell count in DLBCL patients. The initial number of Tregs/Th17 cells and also the Treg/Th17 ratio was not associated with changes in disease-free survival (DFS) in both groups. Therefore, higher frequency of peripheral blood Tregs and Treg/Th17 ratio might be associated with a favorable outcome in lymphoma patients, better response to chemotherapy and lower rate of relapse.

Increased frequency of CD4+ PD-1+ HLA-DR+ T cells is associated with disease progression in CLL

Chronic lymphocytic leukaemia (CLL) patients often have abnormal expansions of CD4+ and CD8+ T cells and this can be associated with progressive disease. To characterise the key T-cell populations involved in this phenomenon, we used flow cytometry and 11 phenotypic markers to study 74 CLL patients and 14 controls. T cells of CLL patients were more phenotypically complex than those of healthy controls with significant increases in the frequencies of CD4 and CD8 memory T cells expressing exhaustion-, activation- and senescence-associated markers. Multivariate analysis of 111 different T-cell subsets showed that high frequencies of four subsets (three CD8 and one CD4) were associated with shorter progression-free survival. The most significant association was with CD4+ HLA-DR+ PD-1+ T cells, and patients could be stratified into high- and low-risk groups based on the frequency of these T cells. The expansion of this CD4+ subset could not be accounted for by age, cytomegalovirus infection or increases in Treg cells. Overall, these results highlight two relatively simple biomarkers, percentage CD8+ and percentage CD4+ PD-1+ HLA-DR+ T cells, which can be used to risk-stratify CLL patients, independent of other tumour-associated markers. They also provide further evidence for the pivotal role of T cells in modulating the pathology of CLL.

Chronic lymphocytic leukaemia: the role of T cells in a B cell disease

Chronic lymphocytic leukaemia (CLL) has long been thought to be an immunosuppressive disease and abnormalities in T-cell subset distribution and function have been observed in many studies. However, the role of T cells (if any) in disease progression remains unclear and has not been directly studied. This has changed with the advent of new therapies, such as chimeric antigen receptor-T cells, which actively use retargeted patient-derived T cells as "living drugs" for CLL. However complete responses are relatively low (~26%) and recent studies have suggested the differentiation status of patient T cells before therapy may influence efficacy. Non-chemotherapeutic drugs, such as idelalisib and ibrutinib, also have an impact on T cell populations in CLL patients. This review will highlight what is known about T cells in CLL during disease progression and after treatment, and discuss the prospects of using T cells as predictive biomarkers for immune status and response to therapy.

Evaluating the role of Tregs in the progression of multiple myeloma

The role of regulatory T-cells (Treg) and Th17 cells in the progression of multiple myeloma has been unclear. There are conflicting reports of the Treg and Th17 frequency being increased, decreased, and unchanged as compared with controls. In this study, we sought to characterize the T-cell subsets including Treg function in both blood and marrow compartments of monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma (MM). The Treg/Th17 ratio is skewed toward the suppressive phenotype in MGUS and MM. There are more activated and memory Tregs in the myeloma marrow. Although the myeloma Tregs are functional, they are less suppressive than Tregs in chronic lymphocytic leukemia where they drive disease progression. None of the T-cell subsets were found to have a clinical correlation with time to progression in MGUS or progression-free survival in myeloma. Tregs are important but unlikely major players in the progression of MGUS to MM.

T cell senescence and CAR-T cell exhaustion in hematological malignancies

T cell senescence has been recognized to play an immunosuppressive role in the aging population and cancer patients. Strategies dedicated to preventing or reversing replicative and premature T cell senescence are required to increase the lifespan of human beings and to reduce the morbidity from cancer. In addition, overcoming the T cell terminal differentiation or senescence from lymphoma and leukemia patients is a promising approach to enhance the effectiveness of adoptive cellular immunotherapy (ACT). Chimeric antigen receptor T (CAR-T) cell and T cell receptor-engineered T (TCR-T) cell therapy highly rely on functionally active T cells. However, the mechanisms which drive T cell senescence remain unclear and controversial. In this review, we describe recent progress for restoration of T cell homeostasis from age-related senescence as well as recovery of T cell activation in hematological malignancies.

A Blood Pact: the Significance and Implications of eIF4E on Lymphocytic Leukemia

Elevated levels of eukaryotic initiation factor 4E (eIF4E) are implicated in neoplasia, with cumulative evidence pointing to its role in the etiopathogenesis of hematological diseases. As a node of convergence for several oncogenic signaling pathways, eIF4E has attracted a great deal of interest from biologists and clinicians whose efforts have been targeting this translation factor and its biological circuits in the battle against leukemia. The role of eIF4E in myeloid leukemia has been ascertained and drugs targeting its functions have found their place in clinical trials. Little is known, however, about the pertinence of eIF4E to the biology of lymphocytic leukemia and a paucity of literature is available in this regard that prospectively evaluates the topic to guide practice in hematological cancer. A comprehensive analysis on the significance of eIF4E translation factor in the clinical picture of leukemia arises, therefore, as a compelling need. This review presents aspects of eIF4E involvement in the realm of the lymphoblastic leukemia status; translational control of immunological function via eIF4E and the state-of-the-art in drugs will also be outlined.

Chemotherapy alters the increased numbers of myeloid-derived suppressor and regulatory T cells in children with acute lymphoblastic leukemia

INTRODUCTION

Acute lymphoblastic leukemia (ALL) is the most common cancer diagnosed in children. The precise mechanism behind the relapse in this disease is not clearly known. One possible mechanism could be the accumulation of immunosuppressive cells, including myeloid-derived suppressor cells (MDSCs) and T regulatory cells (T_regs) which we and others have reported to mediate suppression of anti-tumor immune responses.

AIM

In this study, we aimed to analyze the numbers of these cells in a population of B-ALL pediatric patients.

METHODS

Peripheral blood samples withdrawn from B-ALL pediatric patients (n = 45 before, during and after the induction phase of chemotherapy. Using multi parametric flow cytometric analysis. MDSCs were identified as Lin^-HLA-DR^-CD33⁺CD11b⁺; and T_reg cells were defined as CD4⁺CD25⁺CD127^-/low.

RESULTS

Early diagnosed B-ALL patients showed significant increases in the numbers of MDSCs and T_regs as compared to healthy volunteers. During induction of chemotherapy, however, the patients showed higher and lower numbers of MDSCs and T_reg cells, respectively as compared to early diagnosed patients (i.e., before chemotherapy). After induction of chemotherapy, the numbers of MDSCs and T_reg cells showed higher increases and decreases, respectively as compared to the numbers in patients during chemotherapy.

CONCLUSION

Our results indicate that B-ALL patients harbor high numbers of both MDSCs and T_regs cells. This pilot study opens a new avenue to investigate the mechanism mediating the emergence of these cells on larger number of B-ALL patients at different treatment stages.

Imbalance in circulatory iNKT, Th17 and T regulatory cell frequencies in patients with B-cell non-Hodgkin's lymphoma

T cells are important in B-cell non-Hodgkin's lymphoma immunity, however the function of T cell subsets, including natural killer (iNKT), T helper (Th)17, and T regulatory cells remains to be elucidated. The present study analyzed the frequencies of iNKT, Th17 and T regulatory cells in the peripheral blood of 41 patients with B-cell non-Hodgkin lymphoma at diagnosis, then during and following immunochemotherapy R-CHOP/R-CVP. At lymphoma diagnosis, iNKT and Th17 frequencies were decreased and T regulatory cell frequencies were increased compared with healthy control group. The Th17 cell percentage was lower in patients with a worse prognosis and at a more advanced clinical stage and in contrast, the percentage of T regulatory cells was increased in patients at advanced stages of lymphoma, compared to earlier stages. There was an increase of iNKT and Th17 cells following R-CHOP/R-CVP therapy. In patients that responded, both prior to and following-treatment, percentages of iNKT and Th17 were higher and T regulatory cells were lower compared with patients with subsequent disease progression. Taken together, the results obtained demonstrated the opposing effects of T cell subsets in B-cell lymphoma immunity, with iNKT and Th17 inhibiting and T regulatory cells enhancing tumor growth. These alterations may be caused by malignant B-cells, however there may also be an axis of inverse feedback between T regulatory cells and their interaction with Th17 and iNKT cells.

Quantitative and qualitative analysis of regulatory T cells in B cell chronic lymphocytic leukemia

Accumulated data indicate a significant role of T cell dysfunction in the pathogenesis of chronic lymphocytic leukemia. In CLL, regulatory T cells are significantly higher and show lower apoptotic levels compared to healthy donors. We demonstrate that CLL derived CD4⁺CD25^-CD127^- and CD4⁺CD25^lowCD127^- subpopulations share a common immunophenotypic profile with conventional Tregs and are associated with advanced stage disease. We further provide evidence that the increased number of Tregs contributes indirectly to the proliferation of the CLL clone, by suppressing the proliferation of Teffs which in turn suppress CLL cells. These data are further supported by our observations that CLL derived Tregs appear rather incapable of inducing apoptosis of both normal B cells and CLL cells, in contrast to normal Tregs, suggesting an immunoediting effect of CLL cells on Tregs which negatively affects the functionality of the latter and contributes to the failure of Tregs in CLL to efficiently eliminate the abnormal clone.

Follicular B Lymphomas Generate Regulatory T Cells via the ICOS/ICOSL Pathway and Are Susceptible to Treatment by Anti-ICOS/ICOSL Therapy

The prognosis of follicular lymphoma (FL) patients is suspected to be influenced by tumor-infiltrating regulatory T cells (Treg). The mechanism of Treg enrichment in FL and their impact on malignant FL B cells remains to be elucidated. We analyzed 46 fresh lymph node biopsy samples, including FL (n = 20), diffuse large B-cell lymphoma (n = 10), classical Hodgkin lymphoma (n = 9), and reactive lymphadenitis (n = 7). Using multicolor flow cytometry and cell sorting, we observed an accumulation of CD25(high)CD127(low/neg) Tregs in FL tissues. These Tregs comprised activated ICOS(+) Tregs that were able to suppress not only conventional T cells, but also FL B cells. These FL B cells were able to express ICOSL in vitro and to generate CD25(high)FoxP3(high) Tregs expressing ICOS. Treg generation was associated with ICOS/ICOSL engagement and was abrogated by antagonist anti-ICOS and anti-ICOSL antibodies. Interactions between Tregs and FL B cells resulted in ICOSL downregulation on FL B cells. Our results highlight a key role for Tregs in FL pathogenesis and suggest that targeting the ICOS/ICOSL pathway may be a promising immunotherapy for FL treatment. Cancer Res; 76(16); 4648-60. ©2016 AACR.

CAR T-Cell Therapy: The Role of Physical Barriers and Immunosuppression in Lymphoma

Chimeric antigen receptor (CAR) T-cells have shown remarkable results in patients with B-cell leukemia and lymphoma. However, while CAR T-cells have shown complete responses in a majority of patients with acute lymphoblastic leukemia (ALL), lymphomas are more difficult to treat. Different CAR designs and conditioning protocols seem to affect the persistence of patient responses. However, factors that determine if patients receiving the same CARs will respond or not remain obscure. In Sweden, a phase I/IIa trial using third-generation CAR T-cells is ongoing in which we intend to compare tumor biology and immunology, in each patient, to treatment response. CAR T-cell therapy is a powerful tool to add to the treatment options for this patient group but we need to perform the necessary basic research on the multifactorial mechanisms of action to give patients the best possible option of survival. Such studies are also crucial to expand the success of CAR T-cells beyond CD19+ B-cell malignancy. This review will focus on possible barriers of treating lymphoma to define factors that need to be investigated to develop the next generation of CAR T-cell therapy.

The skewed balance between Tregs and Th17 in chronic lymphocytic leukemia

While Tregs maintain self-tolerance and inhibit antitumor responses, T helper (Th)17 cells may enhance inflammatory and antitumor responses. The balance between these two important T-cell subsets has been skewed in many immunopathologic conditions such as autoimmune and cancer diseases. B-cell chronic lymphocytic leukemia (CLL) is the most common form of leukemia in the western world and is characterized with monoclonal expansion of B lymphocytes. There is evidence which implies that the progression of CLL is associated with expansion of Treg and downregulation of Th17 cells. In this review, we will discuss about immunobiology of Treg and Th17 cells and their role in immunopathogenesis of CLL as well as their reciprocal changes during disease progression.

The role of CD4(+) T cells in BKV-specific T cell immunity

Reactivation of polyomavirus BK (BKV) infection represents a severe complication in kidney transplant (KTX) patients. We previously reported an association between a declining BK viral load and the reconstitution of CD4(+) T cell BKV-specific immunity in patients following kidney transplantation. However, the specific contribution of CD4(+) T cells in the regulation of BKV-replication is unknown. Nevertheless, in vitro enrichment of BKV-specific T cells and subsequent adoptive T cell transfer may improve the restoration of immune competence in KTX patients with BKV infection. To date, strategies to capture human BKV-specific T cells with the ensuing expansion to clinically useful numbers are lacking. Here, we demonstrated a comprehensive flow cytometric analysis of the BKV-specific T cell response that permits access to the majority of T cells specific for immunodominant BKV antigens. A full-spectrum evaluation of the BKV-specific T cell response was performed by stimulating peripheral blood mononuclear cells (PBMC) with a mixture of BKV immunodominant peptide pools at varying concentrations and measuring activation marker expression and cytokine secretion. We also examined the effects of co-stimulation and PBMC resting time prior to activation. We defined the narrow range of stimulation conditions that permit the capture and expansion of functional BKV-specific T cell lines. The generated BKV-specific T cell lines showed the highest specificity and functionality when the T cells were captured according to IFNγ-secretion. This study highlights the multifunctional and cytolytic BKV-specific CD4(+) T cells as a dominant population within the generated T cell product. This method offers a novel approach for the generation of BKV-specific T cell lines for adoptive immunotherapy and underscores the critical role of CD4(+) T cells in the clearance of BKV.

Downregulation of IL-17-producing T cells is associated with regulatory T cell expansion and disease progression in chronic lymphocytic leukemia

Little is known about the immunobiology of interleukin-17 (IL-17)-producing T cells and regulatory T cells (Treg) in chronic lymphocytic leukemia (CLL). In this study, the frequencies of Th17, Tc17, and CD39(+) Treg cells were enumerated in peripheral T cells isolated from 40 CLL patients and 15 normal subjects by flow cytometry. Our results showed a lower frequency of Th17 and Tc17 cells in progressive (0.99 ± 0.12 % of total CD3(+)CD4(+) cells; 0.44 ± 0.09 % of total CD8(+) cells) compared to indolent patients (1.57 ± 0.24 %, p = 0.042; 0.82 ± 0.2 %, p = 0.09) and normal subjects (1.78 ± 0.2 %, p = 0.003; 0.71 ± 0.09 %, p = 0.04). Decrease in IL-17-producing T cells was associated with CD39(+) Treg cells expansion. Variation of IL-17-producing cells and Treg cells in indolent and progressive patients was neither associated to the expression levels of Th1- and Th2-specific transcription factors T-bet and GATA-3 nor to the frequencies of IFN-γ and IL-4-producing CD4(+) T cells in a selected number of samples. Additionally, suppressive potential of CD4(+) Treg was similar in CLL patients and normal subjects. Our data indicate that progression of CLL is associated with downregulation of IL-17-producing T cells and expansion of Treg cells, implying contribution of these subsets of T cells in the progression of CLL.

Small cell lung cancer tumour cells induce regulatory T lymphocytes, and patient survival correlates negatively with FOXP3+ cells in tumour infiltrate

Small cell lung cancer (SCLC) kills at least one person every 2 hr in the United Kingdom. Some patients do relatively well but most have rapidly progressive disease. There is no effective treatment and overall 2-year survival is less than 5%. Patients with SCLC have poorly understood local and systemic immune defects and can be immunocompromised. As CD4(+) T lymphocytes coordinate and regulate immunity, a better understanding of interactions between SCLC tumour cells and CD4(+) T cells may lead to effective molecular immunotherapy. We show that some, but not all, SCLC tumour cell lines secrete molecules that induce IL-10 secretion by and de novo differentiation of functional CD4(+)CD25(+)FOXP3(+)CD127(lo)Helios(-) regulatory T (Treg) cells in healthy blood lymphocytes. FOXP3(+) T cells were found in SCLC tumour biopsies, and patients with higher ratios of FOXP3(+) cells in tumour infiltrates have a worse survival rate. The inhibitory effect of SCLC tumour cells was not affected by blocking IL-10 receptor or TGF-β signalling but was partially reversed by blocking IL-15, which is reported to be involved in human Treg cells induction. IL-15 was secreted by SCLC cells that inhibited CD4(+) T-cell proliferation and was present in SCLC biopsy tumour cells. These novel findings demonstrate that SCLC tumour cells can induce CD4(+) T-cell-mediated immunosuppression. This gives a potential mechanism by which SCLC tumour cells may downregulate local and systemic immune responses and contribute to poor patient survival. Our data suggest that IL-15 and Treg cells are potential new therapeutic targets to improve immune response and patient survival in SCLC.

Aberrant expression of Treg-associated cytokine IL-35 along with IL-10 and TGF-β in acute myeloid leukemia

Acute myeloid leukemia (AML) is the most common hematological malignancy in adults, characterized by distorted proliferation and the development of myeloid cells and their precursors in the blood and bone marrow. Interleukin 35 (IL-35), a novel inhibitory cytokine secreted by regulatory T (Treg) cells is a novel potential target used for the therapeutic manipulation of Treg activity in order to treat cancer and autoimmune diseases. To investigate the role and imbalance of Treg-related cytokines in the pathogenesis of AML, we measured the plasma concentration of three Treg-associated cytokines [IL-35, IL-10 and transforming growth factor-β (TGF-β)] and evaluated their clinical relevance. The concentration of IL-35, IL-10 and TGF-β in plasma specimens from 55 patients with AML [27 newly diagnosed (ND) patients and 28 in complete remission (CR)] and 24 controls was analyzed using the enzyme-linked immunosorbent assay method. Significantly higher levels of plasma IL-35 and IL-10 were observed in AML ND patients compared with healthy controls or AML CR patients. IL-10 concentrations were positively correlated with TGF-β, whereas no correlations were found between the other cytokines. IL-10 levels were positively correlated with white blood cell (WBC) and neutrophil (NEU) count but there were no correlations between IL-35 and TGF-β with WBC and NEU count. In conclusion, we demonstrated for the first time that AML ND patients have increased plasma concentrations of IL-35, suggesting that this cytokine is involved in the pathophysiological process of the disease, and that further research is required to address this issue.

T regulatory cells in B-cell malignancy - tumour support or kiss of death?

It is well established that T regulatory (Treg) cells counteract tumour immunity. However, conflicting results describing the role of Treg cells in haematological tumours warrant further investigations to clarify the interactions between Treg cells and the tumour. B-cell malignancy derives from different stages of B-cell development and differentiation in which T cells play a profound role. The transformed B cell may still be in need of T-cell help to thrive but simultaneously they may be recognized and destroyed by cytotoxic lymphocytes. Recent reports demonstrate that Treg cells can suppress and even kill B cells as part of their normal function to rescue the body from autoimmunity. An emerging body of evidence points out that Treg cells not only inhibit tumour-specific T cells but may also have a role in suppressing the progression of the B-cell tumour. In this review, we discuss the origin and function of Treg cells and their role in patients with B-cell tumours.

Chronic lymphocytic leukaemia cells drive the global CD4+ T cell repertoire towards a regulatory phenotype and leads to the accumulation of CD4+ forkhead box P3+ T cells

Advanced chronic lymphocytic leukaemia (CLL) is associated with profound immunodeficiency, including changes in T regulatory cells (T(regs)). We determined the pattern of expression of forkhead box P3 (FoxP3), CD25, CD27 and CD127 and showed that the frequency of CD4+ FoxP3+ T cells was increased in CLL patients (12% versus 8% in controls). This increase was seen only in advanced disease, with selective expansion of FoxP3-expressing cells in the CD4+ CD25(low) population, whereas the number of CD4+ CD25(high) FoxP3+ cells was unchanged. CD4+ CD25(low) cells showed reduced expression of CD127 and increased CD27, and this regulatory phenotype was also seen on all CD4 T cells subsets in CLL patients, irrespective of CD25 or FoxP3 expression. Incubation of CD4+ T cells with primary CLL tumours led to a sixfold increase in the expression of FoxP3 in CD4+ CD25- T cells. Patients undergoing treatment with fludarabine demonstrated a transient increase in the percentage of CD4+ FoxP3+ T cells, but this reduced to normal levels post-treatment. This work demonstrates that patients with CLL exhibit a systemic T cell dysregulation leading to the accumulation of CD4+ FoxP3+ T cells. This appears to be driven by interaction with malignant cells, and increased understanding of the mechanisms that are involved could provide novel avenues for treatment.