Interleukin-21: basic biology and implications for cancer and autoimmunity

Engineering interferons and interleukins for cancer immunotherapy

Cytokines are a class of potent immunoregulatory proteins that are secreted in response to various stimuli and act locally to regulate many aspects of human physiology and disease. Cytokines play important roles in cancer initiation, progression, and elimination, and thus, there is a long clinical history associated with the use of recombinant cytokines to treat cancer. However, the use of cytokines as therapeutics has been limited by cytokine pleiotropy, complex biology, poor drug-like properties, and severe dose-limiting toxicities. Nevertheless, cytokines are crucial mediators of innate and adaptive antitumor immunity and have the potential to enhance immunotherapeutic approaches to treat cancer. Development of immune checkpoint inhibitors and combination immunotherapies has reinvigorated interest in cytokines as therapeutics, and a variety of engineering approaches are emerging to improve the safety and effectiveness of cytokine immunotherapy. In this review we highlight recent advances in cytokine biology and engineering for cancer immunotherapy.

IL-21 Enhances the Immune Protection Induced by the Vibrio vulnificus Hemolysin A Protein

We previously reported that the Vibrio vulnificus hemolysin A (VvhA) protein elicited good immune protection and could effectively control V. vulnificus infection in mice. However, its molecular mechanism remains unknown. We hypothesized that hemolysin A induces an immunoprotective response via IL-21 regulation. To demonstrate this, IL-21 expression in mice was regulated by injecting either specific antibodies or rIL-21, and the immune response was evaluated by flow cytometry. Our results suggested that IL-21 enhances immune protection by inducing a T follicular helper cell and germinal center B cell response. We used RNA-seq to explore molecular mechanisms and identified 10 upregulated and 32 downregulated genes involved in IL-21-upregulated protection. Gene Ontology analysis and pathway analysis of the differentially expressed genes were also performed. Our findings indicate that IL-21 can enhance the immune protection effect of the VvhA protein and may serve as a novel strategy for enhancing the immune protection effect of protein vaccines.

Identification of T Peripheral Helper (Tph) Cells

T peripheral helper (Tph) cells represent a T cell population that stimulates B cell responses within peripheral tissues. Like T follicular helper (Tfh) cells, PD-1^hi CXCR5^- CD4⁺ Tph cells produce IL-21 and CXCL13, yet these cells differ from Tfh cells in expression of both transcription factors and chemokine receptors. Originally identified in rheumatoid arthritis synovium, Tph cells are expanded in multiple autoimmune diseases. Tph cells can be identified and distinguished from Tfh cells by both flow cytometry and mass cytometry. Here, we describe detailed methods to identify Tph cells and characterize associated phenotypic features and functions. These protocols and additional notes provide a guide to identify and explore the roles of Tph cells in various human diseases.

MicroRNA-30b Is Both Necessary and Sufficient for Interleukin-21 Receptor-Mediated Angiogenesis in Experimental Peripheral Arterial Disease

The interleukin-21 receptor (IL-21R) can be upregulated in endothelial cells (EC) from ischemic muscles in mice following hind-limb ischemia (HLI), an experimental peripheral arterial disease (PAD) model, blocking this ligand–receptor pathway-impaired STAT3 activation, angiogenesis, and perfusion recovery. We sought to identify mRNA and microRNA transcripts that were differentially regulated following HLI, based on the ischemic muscle having intact, or reduced, IL-21/IL21R signaling. In this comparison, 200 mRNAs were differentially expressed but only six microRNA (miR)/miR clusters (and among these only miR-30b) were upregulated in EC isolated from ischemic muscle. Next, myoglobin-overexpressing transgenic (MgTG) C57BL/6 mice examined following HLI and IL-21 overexpression displayed greater angiogenesis, better perfusion recovery, and less tissue necrosis, with increased miR-30b expression. In EC cultured under hypoxia serum starvation, knock-down of miR-30b reduced, while overexpression of miR-30b increased IL-21-mediated EC survival and angiogenesis. In Il21r^−/− mice following HLI, miR-30b overexpression vs. control improved perfusion recovery, with a reduction of suppressor of cytokine signaling 3, a miR-30b target and negative regulator of STAT3. Together, miR-30b appears both necessary and sufficient for IL21/IL-21R-mediated angiogenesis and may present a new therapeutic option to treat PAD if the IL21R is not available for activation.

The Half-Life-Extended IL21 can Be Combined With Multiple Checkpoint Inhibitors for Tumor Immunotherapy

In the era of immune checkpoint blockade cancer therapy, cytokines have become an attractive immune therapeutics to increase response rates. Interleukin 21 (IL21) as a single agent has been evaluated for cancer treatment with good clinical efficacy. However, the clinical application of IL21 is limited by a short half-life and concern about potential immune suppressive effect on dendritic cells. Here, we examined the antitumor function of a half-life extended IL21 alone and in combination with PD-1 blockade using preclinical mouse tumor models. We also determined the immune mechanisms of combination therapy. We found that combination therapy additively inhibited the growth of mouse tumors by increasing the effector function of type 1 lymphocytes. Combination therapy also increased the fraction of type 1 dendritic cells (DC1s) and M1 macrophages in the tumor microenvironment (TME). However, combination therapy also induced immune regulatory mechanisms, including the checkpoint molecules Tim-3, Lag-3, and CD39, as well as myeloid derived suppressor cells (MDSC). This study reveals the mechanisms of IL21/PD-1 cooperation and shed light on rational design of novel combination cancer immunotherapy.

Induction of Unique STAT Heterodimers by IL-21 Provokes IL-1RI Expression on CD8+ T Cells, Resulting in Enhanced IL-1β Dependent Effector Function

IL-1β plays critical roles in the priming and effector phases of immune responses such as the differentiation, commitment, and memory formation of T cells. In this context, several reports have suggested that the IL-1β signal is crucial for CTL-mediated immune responses to viral infections and tumors. However, little is known regarding whether IL-1β acts directly on CD8⁺ T cells and what the molecular mechanisms underlying expression of IL-1 receptors (IL-1Rs) on CD8⁺ T cells and features of IL-1R⁺CD8⁺ T cells are. Here, we provide evidence that the expression of IL-1R type I (IL-1RI), the functional receptor of IL-1β, is preferentially induced by IL-21 on TCR-stimulated CD8⁺ T cells. Further, IL-1β enhances the effector function of CD8⁺ T cells expressing IL-21-induced IL-1RI by increasing cytokine production and release of cytotoxic granules containing granzyme B. The IL-21-IL-1RI-IL-1β axis is involved in an augmented effector function through regulation of transcription factors BATF, Blimp-1, and IRF4. Moreover, this axis confers a unique effector function to CD8⁺ T cells compared to conventional type 1 cytotoxic T cells differentiated with IL-12. Chemical inhibitor and immunoprecipitation assay demonstrated that IL-21 induces a unique pattern of STAT activation with the formation of both STAT1:STAT3 and STAT3:STAT5 heterodimers, which are critical for the induction of IL-1RI on TCR-stimulated CD8⁺ T cells. Taken together, we propose that induction of a novel subset of IL-1RI-expressing CD8⁺ T cells by IL-21 may be beneficial to the protective immune response against viral infections and is therefore important to consider for vaccine design.

Interleukin-17 in Liver Disease Pathogenesis

Interleukin 17A (IL-17A)-producing T helper 17 (Th17) cells were identified as a subset of T helper cells that play a critical role in host defense against bacterial and fungal pathogens. Th17 cells differentiate from Th0 naïve T-cells in response to transforming growth factor β1 (TGF-β1) and IL-6, the cytokines which also drive development of liver fibrosis, require activation of transcription factor retinoic acid receptor-related orphan nuclear receptor gamma t (RORγt). IL-17A signals through the ubiquitously expressed receptor IL-17RA. Expression of IL-17RA is upregulated in patients with hepatitis B virus/hepatitis C virus (HBV/HCV) infections, nonalcoholic steatohepatitis (NASH), alcohol-associated liver disease (AALD), hepatocellular carcinoma (HCC), and experimental models of chronic toxic liver injury. The role of IL-17 signaling in the pathogenesis of NASH- and AALD-induced metabolic liver injury and HCC will be the focus of this review. The role of IL-17A-IL-17RA axis in mediation of the cross-talk between metabolically injured hepatic macrophages, hepatocytes, and fibrogenic myofibroblasts will be discussed.

CD4+ T Cell Dependent B Cell Recovery and Function After Autologous Hematopoietic Stem Cell Transplantation

Introduction

High-dose chemotherapy followed by autologous hematopoietic stem cell transplantation (auto-HSCT) represents a standard treatment regime for multiple myeloma (MM) patients. Common and potentially fatal side effects after auto-HSCT are infections due to a severely compromised immune system with hampered humoral and cellular immunity. This study delineates in depth the quantitative and functional B cell defects and investigates underlying extrinsic or intrinsic drivers.

Methods

Peripheral blood of MM patients undergoing high-dose chemotherapy and auto-HSCT (before high-dose chemotherapy and in early reconstitution after HSCT) was studied. Absolute numbers and distribution of B cell subsets were analyzed ex vivo using flow cytometry. Additionally, B cell function was assessed with T cell dependent (TD) and T cell independent (TI) stimulation assays, analyzing proliferation and differentiation of B cells by flow cytometry and numbers of immunoglobulin secreting cells in ELISpots.

Results

Quantitative B cell defects including a shift in the B cell subset distribution occurred after auto-HSCT. Functionally, these patients showed an impaired TD as well as TI B cell immune response. Individual functional responses correlated with quantitative alterations of CD19+, CD4+, memory B cells and marginal zone-like B cells. The TD B cell function could be partially restored upon stimulation with CD40L/IL-21, successfully inducing B cell proliferation and differentiation into plasmablasts and immunoglobulin secreting cells.

Conclusion

Quantitative and functional B cell defects contribute to the compromised immune defense in MM patients undergoing auto-HSCT. Functional recovery upon TD stimulation and correlation with CD4+ T cell numbers, indicate these as extrinsic drivers of the functional B cell defect. Observed correlations of CD4+, CD19+, memory B and MZ-like B cell numbers with the B cell function suggest that these markers should be tested as potential biomarkers in prospective studies.

Review article: targeting the B cell activation system in autoimmune hepatitis

BACKGROUND

The B cell activation system, consisting of B cell activating factor and a proliferation-inducing ligand, may have pathogenic effects in autoimmune hepatitis.

AIMS

To describe the biological actions of the B cell activation system, indicate its possible role in autoimmune diseases, and evaluate its prospects as a therapeutic target in autoimmune hepatitis METHODS: English abstracts were identified in PubMed by multiple search terms. Full length articles were selected for review, and secondary and tertiary bibliographies were developed.

RESULTS

The B cell activating factor is crucial for the maturation and survival of B cells, and it can co-stimulate T cell activation, proliferation, and survival. It can also modulate the immune response by inducing interleukin 10 production by regulatory B cells. A proliferation-inducing ligand modulates and diversifies the antibody response by inducing class-switch recombination in B cells. It can also increase the proliferation, survival, and antigen activation of T cells. These immune stimulatory actions can be modulated by inducing proliferation of regulatory T cells. The B cell activation system has been implicated in diverse autoimmune diseases, and therapeutic blockade is a management strategy now being evaluated in autoimmune hepatitis.

CONCLUSIONS

The B cell activation system has profound effects on B and T cell function in autoimmune diseases. Blockade therapy is being actively evaluated in autoimmune hepatitis. Clarification of the critical pathogenic components of the B cell activation system will improve the targeting, efficacy, and safety of blockade therapy in this disease.

Chronic LCMV Infection Is Fortified with Versatile Tactics to Suppress Host T Cell Immunity and Establish Viral Persistence

Ever since the immune regulatory strains of lymphocytic choriomeningitis virus (LCMV), such as Clone 13, were isolated, LCMV infection of mice has served as a valuable model for the mechanistic study of viral immune suppression and virus persistence. The exhaustion of virus-specific T cells was demonstrated during LCMV infection, and the underlying mechanisms have been extensively investigated using LCMV infection in mouse models. In particular, the mechanism for gradual CD8⁺ T cell exhaustion at molecular and transcriptional levels has been investigated. These studies revealed crucial roles for inhibitory receptors, surface markers, regulatory cytokines, and transcription factors, including PD-1, PSGL-1, CXCR5, and TOX in the regulation of T cells. However, the action mode for CD4⁺ T cell suppression is largely unknown. Recently, sphingosine kinase 2 was proven to specifically repress CD4⁺ T cell proliferation and lead to LCMV persistence. As CD4⁺ T cell regulation was also known to be important for viral persistence, research to uncover the mechanism for CD4⁺ T cell repression could help us better understand how viruses launch and prolong their persistence. This review summarizes discoveries derived from the study of LCMV in regard to the mechanisms for T cell suppression and approaches for the termination of viral persistence with special emphasis on CD8⁺ T cells.

Interleukin-21 in Viral Infections

Interleukin (IL)-21 is a cytokine that affects the differentiation and function of lymphoid and myeloid cells and regulates both innate and adaptive immune responses. In addition to regulating the immune response to tumor and viral infections, IL-21 also has a profound effect on the development of autoimmune and inflammatory diseases. IL-21 is produced mainly from CD4⁺ T cells-in particular, follicular helper T (Tfh) cells-which have a great influence on the regulation of antibody production. It is also an important cytokine for the activation of CD8⁺ T cells, and its role in recovering the function of CD8⁺ T cells exhausted by chronic microbial infections and cancer has been clarified. Thus, IL-21 plays an extremely important role in viral infections, especially chronic viral infections. In this review, I will introduce the findings to date on how IL-21 is involved in some typical viral infections and the potential of treating viral diseases with IL-21.

Gene-Edited Interleukin CAR-T Cells Therapy in the Treatment of Malignancies: Present and Future

In recent years, chimeric antigen receptor T cells (CAR-T cells) have been faced with the problems of weak proliferation and poor persistence in the treatment of some malignancies. Researchers have been trying to perfect the function of CAR-T by genetically modifying its structure. In addition to the participation of T cell receptor (TCR) and costimulatory signals, immune cytokines also exert a decisive role in the activation and proliferation of T cells. Therefore, genetic engineering strategies were used to generate cytokines to enhance tumor killing function of CAR-T cells. When CAR-T cells are in contact with target tumor tissue, the proliferation ability and persistence of T cells can be improved by structurally or inductively releasing immunoregulatory molecules to the tumor region. There are a large number of CAR-T cells studies on gene-edited cytokines, and the most common cytokines involved are interleukins (IL-7, IL-12, IL-15, IL-18, IL-21, IL-23). Methods for the construction of gene-edited interleukin CAR-T cells include co-expression of single interleukin, two interleukin, interleukin combined with other cytokines, interleukin receptors, interleukin subunits, and fusion inverted cytokine receptors (ICR). Preclinical and clinical trials have yielded positive results, and many more are under way. By reading a large number of literatures, we summarized the functional characteristics of some members of the interleukin family related to tumor immunotherapy, and described the research status of gene-edited interleukin CAR-T cells in the treatment of malignant tumors. The objective is to explore the optimized strategy of gene edited interleukin-CAR-T cell function.

Re-Programming Autoreactive T Cells Into T-Regulatory Type 1 Cells for the Treatment of Autoimmunity

Systemic delivery of peptide-major histocompatibility complex (pMHC) class II-based nanomedicines can re-program cognate autoantigen-experienced CD4+ T cells into disease-suppressing T-regulatory type 1 (TR1)-like cells. In turn, these TR1-like cells trigger the formation of complex regulatory cell networks that can effectively suppress organ-specific autoimmunity without impairing normal immunity. In this review, we summarize our current understanding of the transcriptional, phenotypic and functional make up of TR1-like cells as described in the literature. The true identity and direct precursors of these cells remain unclear, in particular whether TR1-like cells comprise a single terminally-differentiated lymphocyte population with distinct transcriptional and epigenetic features, or a collection of phenotypically different subsets sharing key regulatory properties. We propose that detailed transcriptional and epigenetic characterization of homogeneous pools of TR1-like cells will unravel this conundrum.

The Assessment of IL-21 and IL-22 at the mRNA Level in Tumor Tissue and Protein Concentration in Serum and Peritoneal Fluid in Patients with Ovarian Cancer

The aim of the analysis was for the first time to assess the expression of genes encoding IL-21 and IL-22 at the mRNA level in ovarian tumor specimens and the concentration of these parameters in serum and peritoneal fluid in patients with ovarian serous cancer. The levels of IL-21 and IL-22 transcripts were evaluated with the use of the real-time RT-qPCR. Enzyme-linked immunosorbent assay (ELISA) was used to determine the concentration of proteins. Quantitative analysis of IL-21 gene mRNA in the tumor tissue showed the highest activity in the G1 degree of histopathological differentiation and was higher in G1 compared to the control group. The concentration of IL-21 and IL-22 in the serum and in the peritoneal fluid of women with ovarian cancer varied depending on the degree of histopathological differentiation of the cancer and showed statistical variability compared to controls. The conducted studies have shown that the local and systemic changes in the immune system involving IL-21 and IL-22 indicate the participation of these parameters in the pathogenesis of ovarian cancer, and modulation in the IL-21/IL-22 system may prove useful in the development of new diagnostic and therapeutic strategies used in patients, which require further research.

Immunoengineering approaches for cytokine therapy

Since the discovery of cytokines, much effort has been put forth to achieve therapeutic translation for treatment of various diseases, including cancer and autoimmune diseases. Despite these efforts, very few cytokines have cleared regulatory approval, and those that were approved are not commonly used due to their challenging toxicity profile and/or limited therapeutic efficacy. The main limitation in translation has been that wild-type cytokines have unfavorable pharmacokinetic and pharmacodynamic profiles, either eliciting unwanted systemic side effects or insufficient residence in secondary lymphoid organs. In this review, we address protein-engineering approaches that have been applied to both proinflammatory and anti-inflammatory cytokines to enhance their therapeutic indices, and we highlight diseases in which administration of engineered cytokines is especially relevant.

Polygalaxanthone III downregulates inflammation in the lipopolysaccharide-stimulated RAW264.7 macrophages: A quantibody array analysis

Polygala japonica Houtt. (PJ), a member of the Polygala L. family that is suggested to exhibit detoxification properties in traditional Chinese medicine, is often used to treat upper respiratory tract infections. The anti-inflammatory effects of four main components of PJ (POL, PS-XLIX, PS-E, and PS-F) were examined using the LPS(0.3 μg·mL^-1)-stimulated RAW264.7 macrophage model. The levels of NO, ROS, and iNOS were examined to analyze the anti-inflammatory activity of POL. Additionally, the levels of extracellular inflammation-related cytokines and chemokines were measured using quantibody array. The KEGG pathway analysis was performed to examine the anti-inflammatory mechanism of POL. The levels of NO in the POL-pretreated group were significantly downregulated when compared with those in the PS-E-pretreated, PS-F-pretreated, and PS-XLIX-pretreated groups. POL significantly inhibited the changes of iNOS, ROS, and inflammatory factors caused by LPS stimulation (p < 0.001). The expression levels of IL21 and GM-CSF were examined using qPCR, while those of JAK-STAT signaling pathway-related proteins in the LPS-stimulated RAW264.7 macrophages were analyzed using western blotting. POL significantly downregulated the expression of IL-21 and GM-CSF. The anti-inflammatory mechanism of POL is mediated through the JAK-STAT pathway. Thus, this study demonstrated that POL is an anti-inflammatory component of PJ and elucidated its mechanism.

HIV-1 infection and the lack of viral control are associated with greater expression of interleukin-21 receptor on CD8+ T cells

OBJECTIVES

Interleukin-21 (IL-21) has been linked with the generation of virus-specific memory CD8+ T cells following acute infection with HIV-1 and reduced exhaustion of CD8+ T cells. IL-21 has also been implicated in the promotion of CD8+ T-cell effector functions during viral infection. Little is known about the expression of interleukin-21 receptor (IL-21R) during HIV-1 infection or its role in HIV-1-specific CD8+ T-cell maintenance and subsequent viral control.

METHODS

We compared levels of IL-21R expression on total and memory subsets of CD8+ T cells from HIV-1-negative and HIV-1-positive donors. We also measured IL-21R on antigen-specific CD8+ T cells in volunteers who were positive for HIV-1 and had cytomegalovirus-responding T cells. Finally, we quantified plasma IL-21 in treatment-naive HIV-1-positive individuals and compared this with IL-21R expression.

RESULTS

IL-21R expression was significantly higher on CD8+ T cells (P = 0.0256), and on central memory (P = 0.0055) and effector memory (P = 0.0487) CD8+ T-cell subsets from HIV-1-positive individuals relative to HIV-1-negative individuals. For those infected with HIV-1, the levels of IL-21R expression on HIV-1-specific CD8+ T cells correlated significantly with visit viral load (r = 0.6667, P = 0.0152, n = 13) and inversely correlated with plasma IL-21 (r = -0.6273, P = 0.0440, n = 11). Lastly, CD8+ T cells from individuals with lower set point viral load who demonstrated better viral control had the lowest levels of IL-21R expression and highest levels of plasma IL-21.

CONCLUSION

Our data demonstrates significant associations between IL-21R expression on peripheral CD8+ T cells and viral load, as well as disease trajectory. This suggests that the IL-21 receptor could be a novel marker of CD8+ T-cell dysfunction during HIV-1 infection.

Next-generation cytokines for cancer immunotherapy

Most studies focus on the first and second signals of T cell activation. However, the roles of cytokines in immunotherapy are not fully understood, and cytokines have not been widely used in patient care. Clinical application of cytokines is limited due to their short half-life in vivo, severe toxicity at therapeutic doses, and overall lack of efficacy. Several modifications have been engineered to extend their half-life and increase tumor targeting, including polyethylene glycol conjugation, fusion to tumor-targeting antibodies, and alteration of cytokine/cell receptor-binding affinity. These modifications demonstrate an improvement in either increased antitumor efficacy or reduced toxicity. However, these cytokine engineering strategies may still be improved further, as each strategy poses advantages and disadvantages in the delicate balance of targeting tumor cells, tumor-infiltrating lymphocytes, and peripheral immune cells. This review focuses on selected cytokines, including interferon-α, interleukin (IL)-2, IL-15, IL-21, and IL-12, in both preclinical studies and clinical applications. We review next-generation designs of these cytokines that improve half-life, tumor targeting, and antitumor efficacy. We also present our perspectives on the development of new strategies to potentiate cytokine-based immunotherapy.

Targeting immunometabolism of neoplasms by interleukins: A promising immunotherapeutic strategy for cancer treatment

In recent years, tumor metabolism has become a prevalent research topic for scientists and pharmaceutical companies. As research in the field has progressed, the metabolism-based therapy of tumors has ushered in new opportunities. Most tumors emerge and evolve under selective pressure from their microenvironment, which promotes the diversification of both neoplastic and non-neoplastic compartments of the tumor microenvironment (TME), and finally reaches a certain degree of intratumoral heterogeneity. As a result of the tumor intratumoral heterogeneity, tumor cells often possess a complex energy metabolism phenotype. During tumor progression, the metabolism for both tumor parenchyma and stroma is reprogrammed. The tumor stroma mainly consists of the extracellular matrix, fibroblasts, and immune cells. Interestingly, tumor-infiltrating immune cells utilize different metabolites based on their subtype and function, and these immunometabolic pathways can be modified in the TME. In particular, interleukins play a vital role in the activation and differentiation of immune cells and have exhibited multiple effects on tumor cell neoplasia, invasion, and metastasis. In this review, we summarize the common mechanisms of interleukins affecting the tumor and tumor-infiltrating immune cells metabolically and discuss how these mechanisms may lead to novel therapeutic opportunities. This review might contribute to the novel development of cancer immunotherapy.

Generation of highly proliferative rejuvenated cytotoxic T cell clones through pluripotency reprogramming for adoptive immunotherapy

Adoptive immunotherapy has emerged as a powerful approach to cure cancer and chronic infections. Currently, the generation of a massive number of T cells that provide long-lasting immunity is challenged by exhaustion and differentiation-associated senescence, which inevitably arise during in vitro cloning and expansion. To circumvent these problems, several studies have proposed an induced pluripotent stem cell (iPSC)-mediated rejuvenation strategy to revitalize the exhausted/senescent T-cell clones. Because iPSC-derived cytotoxic T lymphocytes (iPSC-CTLs) generated via commonly used monolayer systems have unfavorable innate-like features such as aberrant natural killer (NK) activity and limited replication potential, we modified the redifferentiation culture to generate CD8αβ⁺CD5⁺CCR7⁺CD45RA⁺CD56^- adaptive iPSC-CTLs. The modified iPSC-CTLs exhibited early memory phenotype, including high replicative capacity and the ability to give rise to potent effector cells. In expansion culture with an optimized cytokine cocktail, iPSC-CTLs proliferated more than 10¹⁵-fold in a feeder-free condition. Our redifferentiation and expansion package of early memory iPSC-CTLs could supply memory and effector T cells for both autologous and allogeneic immunotherapies.

A review of signaling and transcriptional control in T follicular helper cell differentiation

T follicular helper (Tfh) cells are a critical component of adaptive immunity and assist in optimal Ab-mediated defense. Multiple effector functions of Tfh support germinal center B cell survival, Ab class switching, and plasma cell maturation. In the past 2 decades, the phenotype and functional characteristics of GC Tfh have been clarified allowing for robust studies of the Th subset including activation signals and environmental cues controlling Tfh differentiation and migration during an immune response. A unique, 2-step differentiation process of Tfh has been proposed but the mechanisms underlying transition between unstable Tfh precursors and functional mature Tfh remain elusive. Likewise, newly identified transcriptional regulators of Tfh development have not yet been incorporated into our understanding of how these cells might function in disease. Here, we review the signals and downstream transcription factors that shape Tfh differentiation including what is known about the epigenetic processes that maintain Tfh identity. It is proposed that further evaluation of the stepwise differentiation pattern of Tfh will yield greater insights into how these cells become dysregulated in autoimmunity.

Interleukin-21 in cancer immunotherapy: Friend or foe?

Interleukin (IL)-21, a cytokine produced by activated conventional CD4+ T lymphocytes and Natural Killer T cells, drives anti-tumor immunity in the skin and kidney. However IL-21 is also pro-inflammatory in many tissues and promotes colitis-associated colon cancer. Understanding the biology of IL-21 in these different situations is needed to ensure maximal therapeutic benefit.

B Cell Aberrance in Lupus: the Ringleader and the Solution

Systemic lupus erythematosus (SLE) is a prototypical autoimmune disease with high heterogeneity but the common characterization of numerous autoantibodies and systemic inflammation which lead to the damage of multiple organs. Aberrance of B cells plays a pivotal role in the immunopathogenesis of SLE via both antibody-dependent and antibody-independent manners. Escape of autoreactive B cells from the central and peripheral tolerance checkpoints, over-activation of B cells and their excessive cytokines release which drive T cells and dendritic cells stimulation, and dysregulated surface molecules, as well as intracellular signal pathways involved in B cell biology, are all contributing to B cell aberrance and participating in the pathogenesis of SLE. Based on that rationale, targeting aberrance of B cells and relevant molecules and pathways is expected to be a promising strategy for lupus control. Multiple approaches targeting B cells through different mechanisms have been attempted, including B-cell depletion via monoclonal antibodies against B-cell-specific molecules, blockade of B-cell survival and activation factors, suppressing T-B crosstalk by interrupting costimulatory molecules and inhibiting intracellular activation signaling cascade by targeting pathway molecules in B cells. Though most attempts ended in failure, the efficacy of B-cell targeting has been encouraged by the FDA approval of belimumab that blocks B cell-activating factor (BAFF) and the recommended use of anti-CD20 as a remedial therapy in refractory lupus. Still, quantities of clinical trials targeting B cells or relevant molecules are ongoing and some of them have displayed promising preliminary results. Additionally, advances in multi-omics studies help deepen our understandings of B cell biology in lupus and may promote the discovery of novel potential therapeutic targets. The combination of real-world data with basic research achievements may pave the road to conquering lupus.

Why do human B cells secrete granzyme B? Insights into a novel B-cell differentiation pathway

B cells are generally believed to operate as producers of high affinity antibodies to defend the body against microorganisms, whereas cellular cytotoxicity is considered as an exclusive prerogative of natural killer (NK) cells and cytotoxic T lymphocytes (CTLs). In conflict with this dogma, recent studies have demonstrated that the combination of interleukin-21 (IL-21) and B-cell receptor (BCR) stimulation enables B cells to produce and secrete the active form of the cytotoxic serine protease granzyme B (GrB). Although the production of GrB by B cells is not accompanied by that of perforin as in the case of many other GrB-secreting cells, recent findings suggest GrB secretion by B cells may play a significant role in early antiviral immune responses, in the regulation of autoimmune responses, and in cancer immunosurveillance. Here, we discuss in detail how GrB-secreting B cells may influence a variety of immune processes. A better understanding of the role that GrB-secreting B cells are playing in the immune system may allow for the development and improvement of novel immunotherapeutic approaches against infectious, autoimmune and malignant diseases.

Reduced CD5 on CD8+ T Cells in Tumors but Not Lymphoid Organs Is Associated With Increased Activation and Effector Function

CD5, a member of the scavenger receptor cysteine-rich superfamily, is a marker for T cells and a subset of B cells (B1a). CD5 associates with T-cell and B-cell receptors and increased CD5 is an indication of B cell activation. In tumor-infiltrating lymphocytes (TILs) isolated from lung cancer patients, CD5 levels were negatively correlated with anti-tumor activity and tumor‐mediated activation-induced T cell death, suggesting that CD5 could impair activation of anti-tumor T cells. We determined CD5 levels in T cell subsets in different organs in mice bearing syngeneic 4T1 breast tumor homografts and assessed the relationship between CD5 and increased T cell activation and effector function by flow cytometry. We report that T cell CD5 levels were higher in CD4⁺ T cells than in CD8⁺ T cells in 4T1 tumor-bearing mice, and that high CD5 levels on CD4⁺ T cells were maintained in peripheral organs (spleen and lymph nodes). However, both CD4⁺ and CD8⁺ T cells recruited to tumors had reduced CD5 compared to CD4⁺ and CD8⁺ T cells in peripheral organs. In addition, CD5^high/CD4⁺ T cells and CD5^high/CD8⁺ T cells from peripheral organs exhibited higher levels of activation and associated effector function compared to CD5^low/CD4⁺ T cell and CD5^low/CD8⁺ T cell from the same organs. Interestingly, CD8⁺ T cells among TILs and downregulated CD5 were activated to a higher level, with concomitantly increased effector function markers, than CD8⁺/CD5^high TILs. Thus, differential CD5 levels among T cells in tumors and lymphoid organs can be associated with different levels of T cell activation and effector function, suggesting that CD5 may be a therapeutic target for immunotherapeutic activation in cancer therapy.

IL-21-Deficient T Follicular Helper Cells Support B Cell Responses Through IL-27 in Patients With Chronic Hepatitis B

Chronic Hepatitis B (CHB) affects over 350 million people worldwide. Current treatment does result in reduced complications; however, a cure (development of antibodies to the S antigen) is not achieved, requiring life-long therapy. Humoral responses contribute to viral elimination by secreting neutralizing antibodies; though, effective induction of humoral immunity require CD4T cell differentiation into T follicular helper (T_FH) cells that support B cell response through interleukin-21 (IL-21). In CHB, mechanism of T_FH-B interactions is seldom described. During CHB, T_FH cells are defective in producing IL-21 in response to hepatitis B surface antigen (HBsAg). However, regardless of low IL-21, T_FH cells efficiently support B cell responses by producing interleukin-27 (IL-27), which directs the formation of plasmablasts and plasma cells from memory and naïve B cells by enhancing B lymphocyte-induced maturation protein-1. IL-27 not only improved total antibody production but HBsAg-specific IgG and IgM secretion that are essential for viral clearance. Importantly, IL-27+T_FH cells were significantly associated with HBV DNA reduction. Therefore, these findings imply a novel mechanism of T_FH mediated B cell help in CHB and suggest that IL-27 effectively compensate the function of IL-21 by supporting T_FH-B cell function, required for protective antibody response and may contribute to viral clearance by providing potential target for achieving a functional cure.

Serum IL-21 levels predict HBeAg decline during rescue therapy in patients with partial response to nucleos(t)ide analogues

To investigate whether IL-21 levels predict treatment outcomes of salvage therapy among patients with suboptimal response (SOR) to nucleos(t)ide analogues (NAs), serum IL-21 levels were measured in a prospective cohort of hepatitis B e antigen (HBeAg)-positive patients with SOR to antiviral therapy. The patients switched therapy to entecavir (ETV) with or without adefovir (ADV) for 104 weeks. IL-21 levels at treatment week 12 in patients who achieved HBeAg loss with undetectable levels of hepatitis B virus (HBV)-DNA at week 104 were the primary endpoint and the results were compared with those of corresponding patients without such an endpoint. Furthermore, IL-21 levels at treatment week 12 in patients who achieved an HBeAg-level decline at week 104 were assessed as the secondary endpoint. Among 24 enrolled patients with SOR to ADV (n=21), telbivudine (n=2) or ETV (n=1), the median (10-90th percentile) levels of HBeAg, HBV-DNA and ALT at baseline were 2.7 (0.2-3.1) log₁₀ S/CO, 5.2 (3.5-7.5) log₁₀ IU/ml and 0.9 (0.5-3.1) upper limit of normal, respectively. Comparison of the patients with and without HBeAg loss at week 104 indicated that their mean IL-21 levels did not significantly differ at week 12 (63.0±14.4 vs. 55.9±10.5 pg/ml; P=0.26). In the secondary endpoint analyses of patients with and without HBeAg level decline, the elevated levels of IL-21 at the first 12 weeks were significantly higher in the decline group (15.6±8.3 vs. 3.1±13.2 pg/ml; P=0.03). Following adjustment for confounding factors, the elevated levels of IL-21 from baseline to week 12 independently predicted an HBeAg level decline at week 104 (odds ratio=1.137, R²=0.23; P=0.047). In conclusion, the serum IL-21 levels at the first 12 weeks during the salvage therapy independently predicted HBeAg level decline at treatment week 104 in patients with SOR to NAs (ClinicalTrials.gov identifier: NCT01829685; date of registration, April 2013).

Cytokine Regulation and Function in T Cells

T lymphocytes, the major effector cells in cellular immunity, produce cytokines in immune responses to mediate inflammation and regulate other types of immune cells. Work in the last three decades has revealed significant heterogeneity in CD4⁺ T cells, in terms of their cytokine expression, leading to the discoveries of T helper 1 (Th1), Th2, Th17, and T follicular helper (Tfh) cell subsets. These cells possess unique developmental and regulatory pathways and play distinct roles in immunity and immune-mediated pathologies. Other types of T cells, including regulatory T cells and γδ T cells, as well as innate lymphocytes, display similar features of subpopulations, which may play differential roles in immunity. Mechanisms exist to prevent cytokine production by T cells to maintain immune tolerance to self-antigens, some of which may also underscore immune exhaustion in the context of tumors. Understanding cytokine regulation and function has offered innovative treatment of many human diseases.

The role of Th17 cells in viral infections

The present review provides an overview of recent advances regarding the function of Th17 cells and their produced cytokines in the progression of viral diseases. Viral infections alone do not lead to virus-induced malignancies, as both genetic and host safety factors are also involved in the occurrence of malignancies. Acquired immune responses, through the differentiation of Th17 cells, form the novel components of the Th17 cell pathway when reacting with viral infections all the way from the beginning to its final stages. As a result, instead of inducing the right immune responses, these events lead to the suppression of the immune system. In fact, the responses from Th17 cells during persistent viral infections causes chronic inflammation through the production of IL-17 and other cytokines which provide a favorable environment for tumor growth and its development. Additionally, during the past decade, these cells have been understood to be involved in tumor progression and metastasis. However, further research is required to understand Th17 cells' immune mechanisms in the vast variety of viral diseases. This review aims to determine the roles and effects of the immune system, especially Th17 cells, in the progression of viral diseases; which can be highly beneficial for the diagnosis and treatment of these infections.

Are Anti-Inflammatory Cytokines Associated with Cognitive Impairment in Patients with Insomnia Comorbid with Depression? A Pilot Study

BACKGROUND

To distinguish insomnia comorbid with depression (ICD) from chronic insomnia disorder (CID) by exploring the relationship between serum levels of frequently overlooked anti-inflammatory cytokines and cognitive function.

METHODS

A total of 42 ICD patients, 63 CID patients, and 42 healthy control subjects were enrolled in the study. The Pittsburgh Sleep Quality Index and Hamilton Depression Rating Scale were used to assess sleep quality and depression severity, respectively. The Chinese-Beijing version of Montreal Cognitive Assessment scale (MoCA-C) and Nine-Box Maze Test (NBMT) were used to assess cognitive function. Serum levels of anti-inflammatory interleukins (IL-1RA, IL-4, IL-5, IL-10, IL-13, and IL-28A), transforming growth factor (TGF)-β1, granulocyte-macrophage colony-stimulating factor, interferon-γ, and the chemokine regulated upon activation, normal T cell expressed and secreted (RANTES) were measured by enzyme-linked immunosorbent assay.

RESULTS

The ICD group had significantly more errors in the spatial reference task (H=2.55, P_s=0.03) and spatial working memory task (H=5.67, P_s<0.01) of the NBMT, as well as lower levels of IL-1RA (H=-2.85, P_s=0.01), IL-4 (H=-3.28, P_s<0.01), IL-5 (H=-3.35, P_s<0.01), IL-10 (H=-4.46, P_s<0.01), and IL-28A (H=-2.75, P_s=0.02) than control subjects. Compared with the CID group, the ICD group had significantly more errors in the spatial reference memory task (H=-2.84, P_s=0.01) of the NBMT, and lower levels of IL-5 (H=3.41, P_s<0.01), IL-10 (H=5.30, P_s<0.01), IL-13 (H=3.89, P_s<0.01), and GM-CSF (H=2.72, P_s=0.02). A partial correlation analysis showed that the level of one or more of IL-4, IL-5, IL-10, IL-13, and TGF-β1 was positively correlated with cognitive function (MoCA-C score and/or performance in spatial memory task) in ICD patients.

CONCLUSION

ICD is a distinct condition that can be distinguished from CID based on immune dysfunction and specific types of cognitive dysfunction.

Increased expression of interleukin-21-inducible genes in minor salivary glands are associated with primary Sjögren’s syndrome disease characteristics

Objective

To determine the upregulation of IL-21-inducible genes in minor salivary glands (MSGs) in 28 primary SS (pSS) patients and 12 non-pSS subjects and correlate it with disease characteristics.

Methods

RNA sequencing was utilized to compare IL-21-inducible genes expression in the MSGs between pSS and non-pSS subjects. The subgroups were characterized according to the IL-21 score calculated by seven IL-21-inducible genes. Furthermore, the disease characteristics and transcripts implicated in hypoxia and interferon signalling were assessed in two pSS subgroups.

Results

We observed that the expression of the IL-21-inducible genes (IL-21, IL-21R, JAK3, STAT1, HLA-B, CCR7 and CXCL10), the so-called IL-21 signature genes, was significantly increased in pSS patients. The upregulation of JAK3 expression may be induced by hypomethylation of the JAK3 promoter in pSS patients and putatively associated with POU2F2. The patients with increased IL-21 signature gene expression showed an increased EULAR Sjögren’s Syndrome Disease Activity Index score and increased enrichment of B cells, memory B cells, CD4+ T cells and CD8+ T cells. Furthermore, the IL-21 scores in the anti-SSA+, SSB+, ANA+ and high IgG samples were higher than those in the respective antibody-negative samples and normal IgG. In addition, we found both hypoxia and IFN-relevant genes showed strong correlation with IL-21 signature gene expression, indicating their interaction in pSS.

Conclusion

IL-21 signature gene was associated with typical disease characteristics in pSS, which provides insight into the contribution of the IL-21 signalling pathway to the pathogenesis of the disease and might provide a novel treatment strategy for this subtype of pSS.

IFN-γ and IL-18 in conditioned media of parasite-infected host and IL-21-silenced colorectal cancer cells

The presence of certain soluble factors may provide a possible selective advantage for a parasite to gradually modify cell proliferation in neighbouring cells, which may result in chronic diseases. These soluble factors present in the conditioned medium also allow the parasite to invade rapidly into more host cells. The present study aimed to determine the levels of a group of type 1 T helper (Th1) cytokines in the conditioned media of host cells infected with parasites and in IL-21-silenced colorectal cancer cells. The conditioned media of human foreskin fibroblasts (HFFs) parasitized with the RH and ME49 strains of Toxoplasma gondii for 10 days were prepared, and subsequently the levels of the Th1 cytokines in the conditioned media were determined by ELISA. HFFs were incubated with the growth media containing selected soluble factors, and cell proliferation markers were subsequently analysed by reverse transcription-quantitative PCR. The mRNA expression level of cell proliferation markers was also examined in IL-21-silenced HCT116 cells, where the levels of soluble factors in the conditioned media were also determined as aforementioned. The results of the present study demonstrated that HFFs parasitized with ME49 released elevated levels of IFN-γ and lower levels of IL-18 into the conditioned medium compared with the controls. These phenomena were not observed in the conditioned medium of HFFs parasitized with RH. Similar levels of these soluble factors were also detected in the conditioned medium of IL-21-silenced HCT116 cells. The results of the present study also revealed that Ki67 and proliferating cell nuclear antigen mRNA expression was altered in host cells incubated with various levels of IFN-γ and IL-18, as well as in IL-21-silenced HCT116 cells compared with the respective controls. In conclusion, the current study provided preliminary evidence on the fundamental molecular mechanisms of host-parasite interactions that result in chronic diseases, which may aid in the treatment of these diseases in the relevant endemic regions.

Splicing variants of grass carp (Ctenopharyngodon idellus) IL-21: Functions in IgM+ B cell proliferation and IgM secretion

In mammals, interleukin 21 (IL-21) is a type I four-helical bundle cytokine produced by activated T cells that has pleiotropic functions on immune cells. Although IL-21 has been discovered in fish, the splicing variants of this cytokine and their functions on B cells are unclear. In this study, based on the original transcript of grass carp IL-21 (named gcIL-21sv1 in this study), two alternative splicing variants, named gcIL-21sv2 and gcIL-21sv3, were cloned and characterized. The protein sequences of gcIL-21sv1 and gcIL-21sv2 consist of four α-helixes, and only the six amino acid residues at the C-terminal are different. Unlike gcIL-21sv1 and gcIL-21sv2, gcIL-21sv3 lacks the C-terminal region. The expression analysis showed that gcIL-21sv1, gcIL-21sv2, and gcIL-21sv3 were constitutively expressed in all the tested tissues, and their expression could be significantly up-regulated by LPS and Poly (I:C) in head kidney leukocytes (HKLs), with the fold change of gcIL-21sv1 being higher than that of gcIL-21sv2 and gcIL-21sv3. Recombinant gcIL-21sv1 and gcIL-21sv2, but not gcIL-21sv3, could induce the proliferation of IgM⁺ B cells and the secretion of IgM, with the activity of gcIL-21sv1 being stronger than that of gcIL-21sv2, indicating that the C-terminal region plays important roles in the function of gcIL-21. Taken together, this study found that, like IL-21 in human and mouse, IL-21 splicing variants also exist in fish, and the regulatory activities of these variants in humoral immunity are differ, suggesting that grass carp may balance the immune response mediated by IL-21 through alternative splicing.

IL-21 Promotes Intestinal Memory IgA Responses

The role of IL-21, produced mainly by Th17 cells and T follicular helper cells, has been intensively investigated in B cell differentiation and Ab class switch. However, how IL-21 regulates memory IgA⁺ B cell development and memory IgA responses in the intestines is still not completely understood. In this study, we found the total IgA⁺ B cells as well as CD38⁺CD138^-IgA⁺ memory B cells were significantly increased in intestinal lamina propria (LP) of TCRβxδ^-/- mice after transfer of microbiota Ag-specific Th17 cells but not Th1 cells. Although IL-21R^-/- mice or IL-17R^-/- mice showed decreased Ag-specific memory IgA production in the intestines upon infection with Citrobacter rodentium, the percentage of IgA⁺CD38⁺CD138^- memory B cells in Peyer's patches and LP was decreased only in IL-21R^-/- mice, but not in IL-17R^-/- mice, after reinfection with C. rodentium compared with wild-type mice. Blockade IL-21 in vivo suppressed intestinal C. rodentium-specific IgA production as well as IgA⁺CD38⁺CD138^- memory B cells in Peyer's patches and LP. Furthermore, IL-21 significantly induced B cell IgA production in vitro, with the increased expression of genes related with class-switching and memory B cell development, including Aicda, Ski, Bmi1, and Klf2. Consistently, Aicda and Ski expression was decreased in B cells of IL-21R^-/- mice after C. rodentium reinfection. In conclusion, our study demonstrated that IL-21 promotes intestinal memory IgA B cell development, possibly through upregulating differentiation-related and class switching-related genes, indicating a potential role of IL-21 in memory IgA⁺ B cell responses in the intestines.

B cell helper T cells and type 1 diabetes

Type 1 diabetes is an autoimmune disease typically starting in childhood that culminates in the destruction of insulin‐producing beta cells in the pancreas. Although type 1 diabetes is considered to be a primarily T cell–mediated disease, B cells clearly participate in the autoimmune process, as autoantibodies recognizing pancreatic islet antigen commonly appear in circulation before the onset of the disease. T cells providing helper functions to B cells have recently been shown to be involved in the pathogenesis of a wide range of antibody‐associated immune disorders. These T cells include CXCR5‐positive follicular T helper (Tfh) cells, and a recently described closely related CXCR5‐negative subset coined peripheral T helper (Tph) cells. Here, we review the current state of knowledge on different B cell helper T cell subsets, focusing on their potential involvement in the development of type 1 diabetes.

Transcriptional Regulation of Natural Killer Cell Development and Functions

Natural killer (NK) cells are the major lymphocyte subset of the innate immune system. Their ability to mediate anti-tumor cytotoxicity and produce cytokines is well-established. However, the molecular mechanisms associated with the development of human or murine NK cells are not fully understood. Knowledge is being gained about the environmental cues, the receptors that sense the cues, signaling pathways, and the transcriptional programs responsible for the development of NK cells. Specifically, a complex network of transcription factors (TFs) following microenvironmental stimuli coordinate the development and maturation of NK cells. Multiple TFs are involved in the development of NK cells in a stage-specific manner. In this review, we summarize the recent advances in the understandings of TFs involved in the regulation of NK cell development, maturation, and effector function, in the aspects of their mechanisms, potential targets, and functions.

T follicular helper cell-mediated IL-21 production suppresses FOXP3 expression of T follicular regulatory-like cells in diffuse large B cell lymphoma patients

Based on CD25 expression, T follicular helper cells (Tfh) could be divided into T follicular regulatory (Tfr)-like subset (CD25⁺CD4⁺CXCR5⁺) and CD25^- Tfh subset (CD25^-CD4⁺CXCR5⁺). Patients with diffuse large B cell lymphoma (DLBCL) display high level of Tfr-like cells in blood and tumor. This Tfr-like subset could suppress CD8 T cell response while promote tumor cell proliferation. In this study, we investigated the transcription factors and regulatory elements associated with Tfr-like cells in DLBCL patients. Both circulating and tumor-infiltrating Tfr-like cells presented slightly higher Blimp-1 expression and significantly higher Foxp3 expression than the CD25^- Tfh subset. As the IL-2 receptor, CD25 could be moderately upregulated in stimulated CD25^- Tfh cells. However, stimulated CD25^- Tfh cells could not upregulate Foxp3, indicating that the distinction between Foxp3-low CD25^-CXCR5⁺CD4⁺ T cells and Foxp3-high CD25⁺CXCR5⁺CD4⁺ T cells was not due to differences in stimulation status. Regarding cytokine production, while both Tfr-like and CD25^- Tfh cells upregulated IL-21 and IL-10 during stimulation, the CD25^- Tfh cells presented significantly higher IL-21 and lower IL-10 expression than the Tfr-like cells, and the TGF-β expression was only increased in Tfr-like cells. Interestingly, IL-21 secreted from CD25^- Tfh cells negatively regulated the expression of Foxp3 and IL-10 of autologous Tfr-like cells. Together, these results demonstrated that the Tfr-like and CD25^- Tfh subsets of circulating Tfh cells presented different functions and should be investigated separately.

IL-21 and IL-5 coordinately induce surface IgA+ cells

Intestinal IgA is induced by microbes and food antigens. Peyer's patches (PPs) are known as one of the inductive sites for intestinal IgA production. However, the precise mechanism of IgA induction is as yet unknown. IgA secretion was induced from IgD⁺ B cells in vitro by stimulus with lipopolysaccharide in the presence of only retinoic acid (RA) and low doses of TGF-β1. Surface IgA⁺ cells were effectively induced from IgD⁺ B cells in vitro by the mixture of RA and the cytokines TGF-β1, APRIL, IL-5 and IL-21. rIL-21 upregulated surface IgA⁺ but impaired the proliferation of stimulated B cells in the presence of rTGF-β1, RA and rAPRIL, in vitro. The addition of rIL-5 restored the impaired proliferation by rIL-21, resulting in the expansion of IgA⁺ cells. rIL-21 induced the expression of Aicda and Prdm1, and impaired Rel in IgD⁺ B cells. Blockade of IL-21R signaling by a neutralizing mAb in vivo led to lower frequencies of IgA⁺ and IgG2b⁺ cells and lower germinal center B cells in PPs in a homeostatic condition. Although amounts of small intestinal IgA and titers of anti-dsDNA, the major target of intestinal IgA, in these mice were not altered, anti-OVA IgA titers induced by OVA drinking in OVA-specific T-cell receptor (TCR) transgenic mice were decreased. PP-deficient TCR transgenic mice showed diminished anti-OVA IgA induction. Blockade of IL-5R signaling in vivo led to similar results with relatively weaker effects than that of IL-21R mAb administration. These results suggest that IL-21 and IL-5 play cooperative roles in surface expression of IgA in PPs.

Engineered IL-21 Cytokine Muteins Fused to Anti-PD-1 Antibodies Can Improve CD8+ T Cell Function and Anti-tumor Immunity

Inhibitors that block the programmed cell death-1 (PD-1) pathway can potentiate endogenous antitumor immunity and have markedly improved cancer survival rates across a broad range of indications. However, these treatments work for only a minority of patients. The efficacy of anti-PD-1 inhibitors may be extended by cytokines, however, the incorporation of cytokines into therapeutic regimens has significant challenges. In their natural form when administered as recombinant proteins, cytokine treatments are often associated with low response rates. Most cytokines have a short half-life which limits their exposure and efficacy. In addition, cytokines can activate counterregulatory pathways, in the case of immune-potentiating cytokines this can lead to immune suppression and thereby diminish their potential efficacy. Improving the drug-like properties of natural cytokines using protein engineering can yield synthetic cytokines with improved bioavailability and tissue targeting, allowing for enhanced efficacy and reduced off-target effects. Using structure guided engineering we have designed a novel class of antibody-cytokine fusion proteins consisting of a PD-1 targeting antibody fused together with an interleukin-21 (IL-21) cytokine mutein. Our bifunctional fusion proteins can block PD-1/programmed death-ligand 1 (PD-L1) interaction whilst simultaneously delivering IL-21 cytokine to PD-1 expressing T cells. Targeted delivery of IL-21 can improve T cell function in a manner that is superior to anti-PD-1 monotherapy. Fusion of engineered IL-21 variants to anti-PD1 antibodies can improve the drug-like properties of IL-21 cytokine leading to improved cytokine serum half-life allowing for less frequent dosing. In addition, we show that targeted delivery of IL-21 can minimize any potential detrimental effect on local antigen-presenting cells. A highly attenuated IL-21 mutein variant (R9E:R76A) fused to a PD-1 antibody provides protection in a humanized mouse model of cancer that is refractory to anti-PD-1 monotherapy. Collectively, our preclinical data demonstrate that this approach may improve upon and extend the utility of anti-PD-1 therapeutics currently in the clinic.

Ethanol consumption inhibits TFH cell responses and the development of autoimmune arthritis

Alcohol consumption is a consistent protective factor for the development of autoimmune diseases such as rheumatoid arthritis (RA). The underlying mechanism for this tolerance-inducing effect of alcohol, however, is unknown. Here we show that alcohol and its metabolite acetate alter the functional state of T follicular helper (T_FH) cells in vitro and in vivo, thereby exerting immune regulatory and tolerance-inducing properties. Alcohol-exposed mice have reduced Bcl6 and PD-1 expression as well as IL-21 production by T_FH cells, preventing proper spatial organization of T_FH cells to form T_FH:B cell conjugates in germinal centers. This effect is associated with impaired autoantibody formation, and mitigates experimental autoimmune arthritis. By contrast, T cell independent immune responses and passive models of arthritis are not affected by alcohol exposure. These data clarify the immune regulatory and tolerance-inducing effect of alcohol consumption.

Moderate consumption of alcohol is associated with protection from some autoimmune diseases. Here the authors show that ethanol and its metabolite acetate can protect mice from collagen-induced arthritis and provide evidence that the mechanism of this effect might be via inhibition of the effector function of T follicular helper cells.

Targeting tumors with IL-21 reshapes the tumor microenvironment by proliferating PD-1intTim-3-CD8+ T cells

The lack of sufficient functional tumor-infiltrating lymphocytes in the tumor microenvironment (TME) is one of the primary indications for the poor prognosis of patients with cancer. In this study, we developed an Erbitux-based IL-21 tumor-targeting fusion protein (Erb-IL21) to prolong the half-life and improve the antitumor efficacy of IL-21. Compared with Erb-IL2, Erb-IL21 demonstrated much lower toxicity in vivo. Mechanistically, Erb-IL21 selectively expanded functional cytotoxic T lymphocytes but not dysfunctional CD8+ T cells in the TME. We observed that the IL-21-mediated antitumor effect largely depended on the existing intratumoral CD8+ T cells, instead of newly migrated CD8+ T cells. Furthermore, Erb-IL21 overcame checkpoint blockade resistance in mice with advanced tumors. Our study reveals that Erb-IL21 can target IL-21 to tumors and maximize the antitumor potential of checkpoint blockade by expending a subset of tumor antigen-specific CD8+ T cells to achieve effective tumor control.

Characterization and bioactivity of grass carp (Ctenopharyngodon idella) interleukin-21: Inducible production and involvement in inflammatory regulation

In mammals, interleukin 21 (IL-21) is a broad pleiotropic cytokine that plays critical roles in the development of several inflammatory and autoimmune diseases. In fish, functional information of Il-21 is limited, and its role in immune response is largely unknown. In the present study, we cloned a coding sequence of grass carp (Ctenopharyngodon idella) il21 gene (gcil21). To characterize the release patterns and biological activity of gcIl-21, we prepared recombinant gcIl-21 (rgcIl-21) and obtained the polyclonal antibody with gcIl-21 specificity. Western blotting analysis showed that in grass carp head kidney leukocytes (HKLs), gcIl-21 was undetected in culture supernatant of untreated cells but drastically induced by heat-killed Aeromonas hydrophila (A. hydrophila), uncovering the release features of gcIl-21 and its possible involvement in immune response. Subsequent functional experiments revealed that rgcIl-21 did not affect the mRNA expression of grass carp il1b and tgfb, but induced a strong expression of grass carp il10, and to a lesser extent of grass carp tnfa in HKLs, suggesting a dominant effect of gcIl-21 in modulating Il-10 signaling as seen in rainbow trout and mammals. Furthermore, in vivo studies showed that intraperitoneal injection of rgcIl-21 was able to increase the survival rate of grass carp infected with live A. hydrophila, and reduce the pathological responses caused by the same pathogenic bacteria in head kidney and intestine. Taken together, these results for the first time revealed the close relationship of fish Il-21 production and function with inflammatory responses, and highlighted its anti-bacterial and anti-inflammatory ability, thereby providing a new insight into host defense mechanisms in fish.

Association between interleukin-21 gene rs907715 polymorphism and gastric precancerous lesions in a Chinese population

BACKGROUND

The single nucleotide polymorphisms of interleukin-21 (IL-21) gene were confirmed to be related to various diseases, but no studies have examined the possible role of IL-21 single nucleotide polymorphisms (SNPs) (rs907715, rs2221903, and rs12508721) in gastric precancerous lesions.

AIM

To explore the associations between SNPs of IL-21 gene (rs907715, rs2221903, and rs12508721) and gastric precancerous lesions in a Chinese population.

METHODS

Three SNPs of IL-21 were genotyped using polymerase chain reaction–ligase detection reaction in 588 cases and 290 healthy controls from May 2013 to December 2016 in northwestern China. Gastric precancerous lesions were confirmed by endoscopic examination and categorized as non-atrophic gastritis, atrophic gastritis, and intestinal metaplasia. Descriptive statistic and logistic regression were used for data analyses.

RESULTS

IL-21 rs907715 genotype CC and C frequencies were higher in in patients with gastric precancerous lesions than in the controls (OR = 1.59, 95%CI: 1.06-2.38, P = 0.013; OR = 1.28, 95%CI: 1.01-2.22, P = 0.044, respectively) after adjusting for confounding factors. For SNP rs907715 in intestinal metaplasia patients, significant differences between cases and controls were observed in the frequencies of genotype CC and C (OR = 1.92, 95%CI: 1.24-2.98, P = 0.004; OR = 1.53, 95%CI: 1.04-2.24, P = 0.028, respectively); for non-atrophic gastritis and atrophic gastritis patients, the CC and C genotypes showed no significant association with risk in all models. No association between either rs2221903 or rs12508721 and gastric precancerous lesions was found in the present study. In the haplotype analysis, the TC haplotype (rs907715 and rs12508721) and TT haplotype (rs2221903 and rs907715) were more frequent in the case group than control group (P < 0.05).

CONCLUSION

Our findings indicate that SNP rs907715 of IL-21 gene is associated with gastric precancerous lesions. The TC haplotype (rs907715 and rs12508721) and TT haplotype (rs2221903 and rs907715) increased the risk of gastric precancerous lesions. If confirmed, these findings will shed light on the etiology of precancerous lesions.

Japanese flounder Paralichthys olivaceus interleukin 21 induces inflammatory response and plays a vital role in the immune defense against bacterial pathogen

Interleukin (IL)-21 is a pleiotropic cytokine and plays a vital role in immunity. In the current study, we examined the immune function of Japanese flounder Paralichthys olivaceus IL-21 (PoIL-21). PoIL-21 shares moderate (25.17%-46.25%) sequence identities with other teleost IL-21. PoIL-21 expression occurred in multiple tissues, especially intestine, and was regulated by bacterial infection in a time dependent manner. PoIL-21 was secreted by peripheral blood leukocytes (PBL) upon LPS stimulation. Recombinant PoIL-21 (rPoIL-21) bound to a wide range of Gram-negative and Gram-positive bacteria and inhibited the growth of the fish bacterial pathogen Streptococcus iniae. rPoIL-21 also interacted with PBL, resulting in enhanced cell proliferation, ROS production, and expression of IL-1β, TNF-α, CD8β, T-bet, PoIL-21, PoIL-21 receptor, and STAT. Consequently, the presence of rPoIL-21 significantly reduced bacterial infection in PBL. In vivo study showed that rPoIL-21 upregulated the expression of inflammatory cytokines and PoIL-21. Taken together, these results indicate that PoIL-21 is an inducible, secreted cytokine with a broad range of binding capacities and plays an important role in the regulation of anti-bacterial immunity.

Clinico-Biological Implications of Modified Levels of Cytokines in Chronic Lymphocytic Leukemia: A Possible Therapeutic Role

B-cell chronic lymphocytic leukemia (B-CLL) is the main cause of mortality among hematologic diseases in Western nations. B-CLL is correlated with an intense alteration of the immune system. The altered functions of innate immune elements and adaptive immune factors are interconnected in B-CLL and are decisive for its onset, evolution, and therapeutic response. Modifications in the cytokine balance could support the growth of the leukemic clone via a modulation of cellular proliferation and apoptosis, as some cytokines have been reported to be able to affect the life of B-CLL cells in vivo. In this review, we will examine the role played by cytokines in the cellular dynamics of B-CLL patients, interpret the contradictions sometimes present in the literature regarding their action, and evaluate the possibility of manipulating their production in order to intervene in the natural history of the disease.

T follicular helper and T follicular regulatory cells in colorectal cancer: A complex interplay

Colorectal cancer is considered to be one of the major causes of morbidity and mortality all over the world. T Follicular helper (T_FH) and T follicular regulatory (T_FR) cells are specialized providers of T-cells to help B-cells and shaping germinal centers (GC) response. Recent researches reported a high percentage of T_FH and T_FR in different infectious diseases and certain malignancies. However, their functional role in human colorectal cancer (CRC) is relatively unknown. Furthermore, recent studies show that the interaction of both T_FH cells and T_FR cells are essential to promote several diseases. Under the control of specific cytokines and B-cell lymphoma 6 transcription factor (Bcl-6), the major transcription factor of T_FH cells, T_FH, can expand to the other distinct CD4 + T helper cells (TH1, TH2, and TH17) which exert a different role in the development of CRC. This review aims to discuss these suggested roles of the two-opposite subset of follicular T cells in colorectal cancer immune pathogenesis.

IL-17-Producing Cells in Tumor Immunity: Friends or Foes?

IL-17 is produced by RAR-related orphan receptor gamma t (RORγt)-expressing cells including Th17 cells, subsets of γδT cells and innate lymphoid cells (ILCs). The biological significance of IL-17-producing cells is well-studied in contexts of inflammation, autoimmunity and host defense against infection. While most of available studies in tumor immunity mainly focused on the role of T-bet-expressing cells, including cytotoxic CD8⁺ T cells and NK cells, and their exhaustion status, the role of IL-17-producing cells remains poorly understood. While IL-17-producing T-cells were shown to be anti-tumorigenic in adoptive T-cell therapy settings, mice deficient in type 17 genes suggest a protumorigenic potential of IL-17-producing cells. This review discusses the features of IL-17-producing cells, of both lymphocytic and myeloid origins, as well as their suggested pro- and/or anti-tumorigenic functions in an organ-dependent context. Potential therapeutic approaches targeting these cells in the tumor microenvironment will also be discussed.