A critical role for IL-21 in regulating immunoglobulin production

Peritoneal B1 and B2 cells respond differently to LPS and IL-21 stimulation

Peritoneal B cells can be divided into B1 cells (CD11b+CD19+) and B2 cells (CD11b-CD19+) based on CD11b expression. B1 cells play a crucial role in the innate immune response by producing natural antibodies and cytokines. B2 cells share similar traits with B1 cells, influenced by the peritoneal environment. However, the response of both B1 and B2 cells to the same stimuli in the peritoneum remains uncertain. We isolated peritoneal B1 and B2 cells from mice and assessed differences in Interleukin-10(IL-10) secretion, apoptosis, and surface molecule expression following exposure to LPS and Interleukin-21(IL-21). Our findings indicate that B1 cells are potent IL-10 producers, possessing surface molecules with an IgMhiCD43+CD21low profile, and exhibit a propensity for apoptosis in vitro. Conversely, B2 cells exhibit lower IL-10 production and surface markers characterized as IgMlowCD43-CD21hi, indicative of some resistance to apoptosis. LPS stimulates MAPK phosphorylation in B1 and B2 cells, causing IL-10 production. Furthermore, LPS inhibits peritoneal B2 cell apoptosis by enhancing Bcl-xL expression. Conversely, IL-21 has no impact on IL-10 production in these cells. Nevertheless, impeding STAT3 phosphorylation permits IL-21 to increase IL-10 production in peritoneal B cells. Moreover, IL-21 significantly raises apoptosis levels in these cells, a process independent of STAT3 phosphorylation and possibly linked to reduced Bcl-xL expression. This study elucidates the distinct functional and response profiles of B1 and B2 cells in the peritoneum to stimuli like LPS and IL-21, highlighting their differential roles in immunological responses and B cell diversity.

Interleukin 21 promotes IgG1+ plasma cell differentiation instead of class switching to IgE via Blimp1 expression

IgE is induced by the presence of IL-4 by class switching from IgM through IgG1 to IgE. IL-21 inhibits the IgE class switch by induction of Blimp1 leading to Stat6 and AID downregulation, and plasmablast/plasma cell differentiation.

CD4 T Cell-Derived IL-21 Is Critical for Sustaining Plasmodium Infection-Induced Germinal Center Responses and Promoting the Selection of Memory B Cells with Recall Potential

Development of Plasmodium-specific humoral immunity is critically dependent on CD4 Th cell responses and germinal center (GC) reactions during blood-stage Plasmodium infection. IL-21, a cytokine primarily produced by CD4 T cells, is an essential regulator of affinity maturation, isotype class-switching, B cell differentiation, and maintenance of GC reactions in response to many infection and immunization models. In models of experimental malaria, mice deficient in IL-21 or its receptor IL-21R fail to develop memory B cell populations and are not protected against secondary infection. However, whether sustained IL-21 signaling in ongoing GCs is required for maintaining GC magnitude, organization, and output is unclear. In this study, we report that CD4+ Th cells maintain IL-21 expression after resolution of primary Plasmodium yoelii infection. We generated an inducible knockout mouse model that enabled cell type-specific and timed deletion of IL-21 in peripheral, mature CD4 T cells. We found that persistence of IL-21 signaling in active GCs had no impact on the magnitude of GC reactions or their capacity to produce memory B cell populations. However, the memory B cells generated in the absence of IL-21 exhibited reduced recall function upon challenge. Our data support that IL-21 prevents premature cellular dissolution within the GC and promotes stringency of selective pressures during B cell fate determination required to produce high-quality Plasmodium-specific memory B cells. These data are additionally consistent with a temporal requirement for IL-21 in fine-tuning humoral immune memory responses during experimental malaria.

Enhanced attenuation of chikungunya vaccines expressing antiviral cytokines

Alphaviruses are vector-borne, medically relevant, positive-stranded RNA viruses that cause disease in animals and humans worldwide. Of this group, chikungunya virus (CHIKV) is the most significant human pathogen, responsible for generating millions of infections leading to severe febrile illness and debilitating chronic joint pain. Currently, there are limited treatments to protect against alphavirus disease; thus, there is a tremendous need to generate safe and effective vaccines. Live-attenuated vaccines (LAVs) are cost-effective and potent immunization strategies capable of generating long-term protection in a single dose. However, LAVs often produce systemic viral replication, which can lead to unwanted post-vaccination side effects and pose a risk of reversion to a pathogenic phenotype and transmission to mosquitoes. Here, we utilized a chimeric infectious clone of CHIKV engineered with the domain C of the E2 gene of Semliki Forest virus (SFV) to express IFNγ and IL-21-two potent antiviral and immunomodulatory cytokines-in order to improve the LAV's attenuation while maintaining immunogenicity. The IFNγ- and IL-21-expressing vaccine candidates were stable during passage and significantly attenuated post-vaccination, as mice experienced reduced footpad swelling with minimal systemic replication and dissemination capacity compared to the parental vaccine. Additionally, these candidates provided complete protection to mice challenged with WT CHIKV. Our dual attenuation strategy represents an innovative way to generate safe and effective alphavirus vaccines that could be applied to other viruses.

Regulatory B Cells-Immunopathological and Prognostic Potential in Humans

The aim of the following review is to shed light on the putative role of regulatory B cells (Bregs) in various human diseases and highlight their potential prognostic and therapeutic relevance in humans. Regulatory B cells are a heterogeneous group of B lymphocytes capable of suppressing inflammatory immune reactions. In this way, Bregs contribute to the maintenance of tolerance and immune homeostasis by limiting ongoing immune reactions temporally and spatially. Bregs play an important role in attenuating pathological inflammatory reactions that can be associated with transplant rejection, graft-versus-host disease, autoimmune diseases and allergies but also with infectious, neoplastic and metabolic diseases. Early studies of Bregs identified IL-10 as an important functional molecule, so the IL-10-secreting murine B10 cell is still considered a prototype Breg, and IL-10 has long been central to the search for human Breg equivalents. However, over the past two decades, other molecules that may contribute to the immunosuppressive function of Bregs have been discovered, some of which are only present in human Bregs. This expanded arsenal includes several anti-inflammatory cytokines, such as IL-35 and TGF-β, but also enzymes such as CD39/CD73, granzyme B and IDO as well as cell surface proteins including PD-L1, CD1d and CD25. In summary, the present review illustrates in a concise and comprehensive manner that although human Bregs share common functional immunosuppressive features leading to a prominent role in various human immunpathologies, they are composed of a pool of different B cell types with rather heterogeneous phenotypic and transcriptional properties.

IL-17 and IL-21: Their Immunobiology and Therapeutic Potentials

Studies over the last 2 decades have identified IL-17 and IL-21 as key cytokines in the modulation of a wide range of immune responses. IL-17 serves as a critical defender against bacterial and fungal pathogens, while maintaining symbiotic relationships with commensal microbiota. However, alterations in its levels can lead to chronic inflammation and autoimmunity. IL-21, on the other hand, bridges the adaptive and innate immune responses, and its imbalance is implicated in autoimmune diseases and cancer, highlighting its important role in both health and disease. Delving into the intricacies of these cytokines not only opens new avenues for understanding the immune system, but also promises innovative advances in the development of therapeutic strategies for numerous diseases. In this review, we will discuss an updated view of the immunobiology and therapeutic potential of IL-17 and IL-21.

Beneficial effect of temporary methotrexate interruption on B and T cell responses upon SARS-CoV-2 vaccination in patients with rheumatoid arthritis or psoriatic arthritis

B and T cell responses were evaluated in patients with rheumatoid arthritis (RA) or psoriatic arthritis (PsA) after 1 or 2 weeks of methotrexate (MTX) withdrawal following each COVID-19 vaccine dose and compared with those who maintained MTX. Adult RA and PsA patients treated with MTX were recruited and randomly assigned to 3 groups: MTX-maintenance (n = 72), MTX-withdrawal for 1 week (n = 71) or MTX-withdrawal for 2 weeks (n = 73). Specific antibodies to several SARS-CoV-2 antigens and interferon (IFN)-γ and interleukin (IL)-21 responses were assessed. MTX withdrawal in patients without previous COVID-19 was associated with higher levels of anti-RBD IgG and neutralising antibodies, especially in the 2-week withdrawal group and with higher IFN-γ secretion upon stimulation with pools of SARS-CoV-2 S peptides. No increment of RA/PsA relapses was detected across groups. Our data indicate that two-week MTX interruption following COVID-19 vaccination in patients with RA or PsA improves humoral and cellular immune responses.

Translatability of findings from cynomolgus monkey to human suggests a mechanistic role for IL-21 in promoting immunogenicity to an anti-PD-1/IL-21 mutein fusion protein

AMG 256 is a bi-specific, heteroimmunoglobulin molecule with an anti-PD-1 antibody domain and a single IL-21 mutein domain on the C-terminus. Nonclinical studies in cynomolgus monkeys revealed that AMG 256 administration led to the development of immunogenicity-mediated responses and indicated that the IL-21 mutein domain of AMG 256 could enhance the anti-drug antibody response directed toward the monoclonal antibody domain. Anti-AMG 256 IgE were also observed in cynomolgus monkeys. A first-in-human (FIH) study in patients with advanced solid tumors was designed with these risks in mind. AMG 256 elicited ADA in 28 of 33 subjects (84.8%). However, ADA responses were only robust and exposure-impacting at the 2 lowest doses. At mid to high doses, ADA responses remained low magnitude and all subjects maintained exposure, despite most subjects developing ADA. Limited drug-specific IgE were also observed during the FIH study. ADA responses were not associated with any type of adverse event. The AMG 256 program represents a unique case where nonclinical studies informed on the risk of immunogenicity in humans, due to the IL-21-driven nature of the response.

Co-expression of IL-21-Enhanced NKG2D CAR-NK cell therapy for lung cancer

BACKGROUND

Adoptive cell therapy has achieved great success in treating hematological malignancies. However, the production of chimeric antigen receptor T (CAR-T) cell therapy still faces various difficulties. Natural killer (NK)-92 is a continuously expandable cell line and provides a promising alternative for patient's own immune cells.

METHODS

We established CAR-NK cells by co-expressing natural killer group 2 member D (NKG2D) and IL-21, and evaluated the efficacy of NKG2D-IL-21 CAR-NK cells in treating lung cancer in vitro and in vivo.

RESULTS

Our data suggested that the expression of IL-21 effectively increased the cytotoxicity of NKG2D CAR-NK cells against lung cancer cells in a dose-dependent manner and suppressed tumor growth in vitro and in vivo. In addition, the proliferation of NKG2D-IL-21 CAR-NK cells were enhanced while the apoptosis and exhaustion of these cells were suppressed. Mechanistically, IL-21-mediated NKG2D CAR-NK cells function by activating AKT signaling pathway.

CONCLUSION

Our findings provide a novel option for treating lung cancer using NKG2D-IL-21 CAR-NK cell therapy.

Destabilisation of T cell-dependent humoral immunity in sepsis

Sepsis is a heterogeneous condition defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. For some, sepsis presents as a predominantly suppressive disorder, whilst others experience a pro-inflammatory condition which can culminate in a 'cytokine storm'. Frequently, patients experience signs of concurrent hyper-inflammation and immunosuppression, underpinning the difficulty in directing effective treatment. Although intensive care unit mortality rates have improved in recent years, one-third of discharged patients die within the following year. Half of post-sepsis deaths are due to exacerbation of pre-existing conditions, whilst half are due to complications arising from a deteriorated immune system. It has been suggested that the intense and dysregulated response to infection may induce irreversible metabolic reprogramming in immune cells. As a critical arm of immune protection in vertebrates, alterations to the adaptive immune system can have devastating repercussions. Indeed, a marked depletion of lymphocytes is observed in sepsis, correlating with increased rates of mortality. Such sepsis-induced lymphopenia has profound consequences on how T cells respond to infection but equally on the humoral immune response that is both elicited by B cells and supported by distinct CD4+ T follicular helper (TFH) cell subsets. The immunosuppressive state is further exacerbated by functional impairments to the remaining lymphocyte population, including the presence of cells expressing dysfunctional or exhausted phenotypes. This review will specifically focus on how sepsis destabilises the adaptive immune system, with a closer examination on how B cells and CD4+ TFH cells are affected by sepsis and the corresponding impact on humoral immunity.

Biological effects of IL-21 on immune cells and its potential for cancer treatment

Interleukin-21 (IL-21), a member of the IL-2 cytokine family, is one of the most important effector and messenger molecules in the immune system. Produced by various immune cells, IL-21 has pleiotropic effects on innate and adaptive immune responses via regulation of natural killer, T, and B cells. An anti-tumor role of IL-21 has also been reported in the literature, as it may support cell proliferation or on the contrary induce growth arrest or apoptosis of the tumor cell. Anti-tumor effect of IL-21 enhances when combined with other agents that target tumor cells, immune regulatory circuits, or other immune-enhancing molecules. Therefore, understanding the biology of IL-21 in the tumor microenvironment (TME) and reducing its systemic toxic and side effects is crucial to ensure the maximum benefits of anti-tumor treatment strategies. In this review, we provide a comprehensive overview on the biological functions, roles in tumors, and the recent advances in preclinical and clinical research of IL-21 in tumor immunotherapy.

The role of Interleukin-21 in autoimmune Diseases: Mechanisms, therapeutic Implications, and future directions

IL-21 is a multifunctional cytokine that regulates the functional activity of various immune cells. Initial studies have shown that IL-21 can influence the differentiation, proliferation and function of T and B cells, as well as promote the maturation and increase the cytotoxicity of CD8 + T cells and NK cells. During humoral immune responses, IL-21 has significant effects on B cell activation, differentiation and apoptosis. In addition, IL-21 promotes the differentiation of both naive and memory B cells, ultimately leading to the activation of plasma cells. The function of IL-21 in the immune system is complex, as it has the ability to either stimulate or inhibit immune responses. in addition, IL-21 facilitates the differentiation of naive and memory B cells into plasma cells. The functionality of IL-21 in the immune system is diverse, as it has the ability to stimulate or inhibit immune responses. This cytokine has been implicated in several diseases including cancer, allergies and autoimmune diseases. Research has suggested that this cytokine is involved in the development of autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis. Several studies have suggested that inhibition of IL-21 has a therapeutic effect on autoimmune diseases. Therefore, targeting both the cytokine's receptor and IL-21 in autoimmune diseases may be an effective approach to reduce the severity of the disease or to treat it. This review will examine the biological effects of IL-21 on various immune cells and the role of the cytokine in autoimmune diseases.

IgG4-related cholangitis - a mimicker of fibrosing and malignant cholangiopathies

IgG4-related cholangitis (IRC) is the major hepatobiliary manifestation of IgG4-related disease (IgG4-RD), a systemic fibroinflammatory disorder. The pathogenesis of IgG4-RD and IRC is currently viewed as multifactorial, as there is evidence of a genetic predisposition while environmental factors, such as blue-collar work, are major risk factors. Various autoantigens have been described in IgG4-RD, including annexin A11 and laminin 511-E8, proteins which may exert a partially protective function in cholangiocytes by enhancing secretion and barrier function, respectively. For the other recently described autoantigens, galectin-3 and prohibitin 1, a distinct role in cholangiocytes appears less apparent. In relation to these autoantigens, oligoclonal expansions of IgG4+ plasmablasts are present in patients with IRC and disappear upon successful treatment. More recently, specific T-cell subtypes including regulatory T cells, follicular T helper 2 cells, peripheral T helper cells and cytotoxic CD8+ and CD4+ SLAMF7+ T cells have been implicated in the pathogenesis of IgG4-RD. The clinical presentation of IRC often mimics other biliary diseases such as primary sclerosing cholangitis or cholangiocarcinoma, which may lead to inappropriate medical and potentially invalidating surgical interventions. As specific biomarkers are lacking, diagnosis is made according to the HISORt criteria comprising histopathology, imaging, serology, other organ manifestations and response to therapy. Treatment of IRC aims to prevent or alleviate organ damage and to improve symptoms and consists of (i) remission induction, (ii) remission maintenance and (iii) long-term management. Glucocorticosteroids are highly effective for remission induction, after which immunomodulators can be introduced for maintenance of remission as glucocorticosteroid-sparing alternatives. Increased insight into the pathogenesis of IRC will lead to improved diagnosis and novel therapeutic strategies in the future.

Single cell transcriptome analyses reveal the roles of B cells in fructose-induced hypertension

Rationale

While the immune system plays a crucial role in the development of hypertension, the specific contributions of distinct immune cell populations remain incompletely understood. The emergence of single-cell RNA-sequencing (scRNA-seq) technology enables us to analyze the transcriptomes of individual immune cells and to assess the significance of each immune cell type in hypertension development.

Objective

We aimed to investigate the hypothesis that B cells play a crucial role in the development of fructose-induced hypertension.

Methods and Results

Eight-week-old Dahl salt-sensitive (SS) male rats were divided into two groups and given either tap water (TW) or a 20% fructose solution (HFS) for 4 weeks. Systolic blood pressure was measured using the tail-cuff method. ScRNA-seq analysis was performed on lamina propria cells (LPs) and peripheral blood mononuclear cells (PBMCs) obtained from SS rats subjected to either TW or HFS. The HFS treatment induced hypertension in the SS rats. The analysis revealed 27 clusters in LPs and 28 clusters in PBMCs, allowing for the identification and characterization of various immune cell types within each cluster. Specifically, B cells and follicular helper T (Tfh) cells were prominent in LPs, while B cells and M1 macrophages dominated PBMCs in the HFS group. Moreover, the HFS treatment triggered an increase in the number of B cells in both LPs and PBMCs, accompanied by activation of the interferon pathway.

Conclusions

The significant involvement of B cells in intestinal and PBMC responses indicates their pivotal contribution to the development of hypertension. This finding suggests that targeting B cells could be a potential strategy to mitigate high blood pressure in fructose-induced hypertension. Moreover, the simultaneous increase in follicular B cells and Tfh cells in LPs, along with the upregulation of interferon pathway genes in B cells, underscores a potential autoimmune factor contributing to the pathogenesis of fructose-induced hypertension in the intestine.

IL-21 shapes germinal center polarization via light zone B cell selection and cyclin D3 upregulation

Germinal center (GC) dysregulation has been widely reported in the context of autoimmunity. Here, we show that interleukin 21 (IL-21), the archetypal follicular helper T cell (Tfh) cytokine, shapes the scale and polarization of spontaneous chronic autoimmune as well as transient immunization-induced GC. We find that IL-21 receptor deficiency results in smaller GC that are profoundly skewed toward a light zone GC B cell phenotype and that IL-21 plays a key role in selection of light zone GC B cells for entry to the dark zone. Light zone skewing has been previously reported in mice lacking the cell cycle regulator cyclin D3. We demonstrate that IL-21 triggers cyclin D3 upregulation in GC B cells, thereby tuning dark zone inertial cell cycling. Lastly, we identify Foxo1 regulation as a link between IL-21 signaling and GC dark zone formation. These findings reveal new biological roles for IL-21 within GC and have implications for autoimmune settings where IL-21 is overproduced.

Molecular consideration relevant to the mechanism of the comorbidity between psoriasis and systemic lupus erythematosus (Review)

Systemic lupus erythematosus (SLE), a common autoimmune disease with a global incidence and newly diagnosed population estimated at 5.14 (range, 1.4-15.13) per 100,000 person-years and 0.40 million people annually, respectively, affects multiple tissues and organs; for example, skin, blood system, heart and kidneys. Accumulating data has also demonstrated that psoriasis (PS) can be a systemic inflammatory disease, which can affect organs other than the skin and occur alongside other autoimmune diseases, such as inflammatory bowel disease, multiple sclerosis, rheumatoid arthritis and SLE. The current explanations for the possible comorbidity of PS and SLE include: i) The two diseases share susceptible gene loci; ii) they share a common IL-23/T helper 17 (Th17) axis inflammatory pathway; and iii) the immunopathogenesis of the two conditions is a consequence of the interactions between IL-17 cytokines with effector Th17 cells, T regulatory cells, as well as B cells. In addition, the therapeutic efficacy of IL-17 or TNF-α inhibitors has been demonstrated in PS, and has also become evident in SLE. However, the mechanisms have not been investigated. To the best of our knowledge, there remains a lack of substantial studies on the correlation between PS and SLE. In the present review, the literature, with regards to the epidemiology, genetic predisposition, inflammatory mechanisms and treatment of the patients with both PS and SLE, has been reviewed. Further investigations into the molecular pathogenic mechanism may provide drug targets that could benefit the patients with concomitant PS and SLE.

Interleukin-21 Influences Glioblastoma Course: Biological Mechanisms and Therapeutic Potential

Brain tumors represent a heterogeneous group of neoplasms involving the brain or nearby tissues, affecting populations of all ages with a high incidence worldwide. Among the primary brain tumors, the most aggressive and also the most common is glioblastoma (GB), a type of glioma that falls into the category of IV-grade astrocytoma. GB often leads to death within a few months after diagnosis, even if the patient is treated with available therapies; for this reason, it is important to continue to discover new therapeutic approaches to allow for a better survival rate of these patients. Immunotherapy, today, seems to be one of the most innovative types of treatment, based on the ability of the immune system to counteract various pathologies, including cancer. In this context, interleukin 21 (IL-21), a type I cytokine produced by natural killer (NK) cells and CD4+ T lymphocytes, appears to be a valid target for new therapies since this cytokine is involved in the activation of innate and adaptive immunity. To match this purpose, our review deeply evaluated how IL-21 could influence the progression of GB, analyzing its main biological processes and mechanisms while evaluating the potential use of the latest available therapies.

IL-6 and IL-27 play both distinct and redundant roles in regulating CD4 T-cell responses during chronic viral infection

The IL-6 cytokine family signals through the common signal transduction molecule gp130 combined with a cytokine-specific receptor. Gp130 signaling on CD4 T cells is vital in controlling chronic infection of mice with lymphocytic choriomeningitis virus clone 13 (LCMV Cl13), but the precise role of individual members of the IL-6 cytokine family is not fully understood. Transcriptional analysis highlighted the importance of gp130 signaling in promoting key processes in CD4 T cells after LCMV Cl13 infection, particularly genes associated with T follicular helper (Tfh) cell differentiation and IL-21 production. Further, Il27r-/-Il6ra-/- mice failed to generate antibody or CD8 T-cell immunity and to control LCMV Cl13. Transcriptomics and phenotypic analyses of Il27r-/-Il6ra-/- Tfh cells revealed that IL-6R and IL-27R signaling was required to activate key pathways within CD4 T cells. IL-6 and IL-27 signaling has distinct and overlapping roles, with IL-6 regulating Tfh differentiation, IL-27 regulating CD4 T cell survival, and both redundantly promoting IL-21.

Phorbol-12-myristate-13-acetate is a potent enhancer of B cells with a granzyme B+ regulatory phenotype

Introduction

The infusion of ex-vivo-generated regulatory B cells may represent a promising novel therapeutic approach for a variety of autoimmune and hyperinflammatory conditions including graft-versus-host disease.

Methods

Previously, we developed a protocol for the generation of a novel population of regulatory B cells, which are characterized by secretion of enzymatically active granzyme B (GraB cells). This protocol uses recombinant interleukin 21 (IL-21) and goat-derived F(ab)'2 fragments against the human B cell receptor (anti-BCR). Generally, the use of xenogeneic material for the manufacturing of advanced therapy medicinal products should be avoided to prevent adverse immune reactions as well as potential transmission of so far unknown diseases.

Results

In the present work we demonstrated that phorbol-12-myristate-13-acetate (PMA/TPA), a phorbol ester with a particular analogy to the second messenger diacylglycerol (DAG), is a potent enhancer of IL-21-induced differentiation of pre-activated B cells into GraB cells. The percentage of GraB cells after stimulation of pre-activated B cells with IL-21 and PMA/TPA was not significantly lower compared to stimulation with IL-21 and anti-BCR.

Discussion

Given that PMA/TPA has already undergone encouraging clinical testing in patients with certain haematological diseases, our results suggest that PMA/TPA may be a safe and feasible alternative for ex-vivo manufacturing of GraB cells.

The interweaved signatures of common-gamma-chain cytokines across immunologic lineages

"γc" cytokines are a family whose receptors share a "common-gamma-chain" signaling moiety, and play central roles in differentiation, homeostasis, and communications of all immunocyte lineages. As a resource to better understand their range and specificity of action, we profiled by RNAseq the immediate-early responses to the main γc cytokines across all immunocyte lineages. The results reveal an unprecedented landscape: broader, with extensive overlap between cytokines (one cytokine doing in one cell what another does elsewhere) and essentially no effects unique to any one cytokine. Responses include a major downregulation component and a broad Myc-controlled resetting of biosynthetic and metabolic pathways. Various mechanisms appear involved: fast transcriptional activation, chromatin remodeling, and mRNA destabilization. Other surprises were uncovered: IL2 effects in mast cells, shifts between follicular and marginal zone B cells, paradoxical and cell-specific cross-talk between interferon and γc signatures, or an NKT-like program induced by IL21 in CD8+ T cells.

Complex interactions of cellular players in chronic Graft-versus-Host Disease

Chronic Graft-versus-Host Disease is a life-threatening inflammatory condition that affects many patients after allogeneic hematopoietic stem cell transplantation. Although we have made substantial progress in understanding disease pathogenesis and the role of specific immune cell subsets, treatment options are still limited. To date, we lack a global understanding of the interplay between the different cellular players involved, in the affected tissues and at different stages of disease development and progression. In this review we summarize our current knowledge on pathogenic and protective mechanisms elicited by the major involved immune subsets, being T cells, B cells, NK cells and antigen presenting cells, as well as the microbiome, with a special focus on intercellular communication of these cell types via extracellular vesicles as up-and-coming fields in chronic Graft-versus-Host Disease research. Lastly, we discuss the importance of understanding systemic and local aberrant cell communication during disease for defining better biomarkers and therapeutic targets, eventually enabling the design of personalized treatment schemes.

Requirements of IL-4 during the Generation of B Cell Memory

IL-4 has long been established as a key regulator of Th cells and for promoting effective B cell survival and isotype class switching. Yet, despite having been extensively studied, the specific role of IL-4 in generating humoral memory in vivo is unclear. In this review, we explore the recent studies that unravel the cellular sources and spatiotemporal production of IL-4, the relationship between IL-4 and IL-21 during germinal center responses and the formation of Ab-secreting cells, and the current understanding of whether IL-4 promotes or suppresses memory B cell generation in vitro and in vivo.

T helper 2 cells in asthma

Allergic asthma is among the most common immune-mediated diseases across the world, and type 2 immune responses are thought to be central to pathogenesis. The importance of T helper 2 (Th2) cells as central regulators of type 2 responses in asthma has, however, become less clear with the discovery of other potent innate sources of type 2 cytokines and innate mediators of inflammation such as the alarmins. This review provides an update of our current understanding of Th2 cells in human asthma, highlighting their many guises and functions in asthma, both pathogenic and regulatory, and how these are influenced by the tissue location and disease stage and severity. It also explores how biologics targeting type 2 immune pathways are impacting asthma, and how these have the potential to reveal hitherto underappreciated roles for Th2 cell in lung inflammation.

Combination of High-Resolution Structures for the B Cell Receptor and Co-Receptors Provides an Understanding of Their Interactions with Therapeutic Antibodies

B cells are central to the adaptive immune response, providing long lasting immunity after infection. B cell activation is mediated by a cell surface B cell receptor (BCR) following recognition of an antigen. BCR signaling is modulated by several co-receptors including CD22 and a complex that contains CD19 and CD81. Aberrant signaling through the BCR and co-receptors promotes the pathogenesis of several B cell malignancies and autoimmune diseases. Treatment of these diseases has been revolutionized by the development of monoclonal antibodies that bind to B cell surface antigens, including the BCR and its co-receptors. However, malignant B cells can escape targeting by several mechanisms and until recently, rational design of antibodies has been limited by the lack of high-resolution structures of the BCR and its co-receptors. Herein we review recently determined cryo-electron microscopy (cryo-EM) and crystal structures of the BCR, CD22, CD19 and CD81 molecules. These structures provide further understanding of the mechanisms of current antibody therapies and provide scaffolds for development of engineered antibodies for treatment of B cell malignancies and autoimmune diseases.

Detection of Anti-ZIKV NS1 IgA, IgM, and Combined IgA/IgM and Identification of IL-4 and IL-10 as Potential Biomarkers for Early ZIKV and DENV Infections in Hyperendemic Regions, Thailand

The frequency of Zika virus (ZIKV)-specific IgA and IgM and the cytokine expression profile of ZIKV-infected patients in hyperendemic areas remain unclear. This study investigated the rates of ZIKV non-structural protein 1 (NS1)-specific IgA and IgM and evaluated serum cytokine levels of ZIKV and Dengue virus (DENV) cases in Thailand to identify potential diagnostic biomarkers, elucidate the immunity against ZIKV and DENV, and investigate the association between cytokine levels and ZIKV symptoms. Low rates of positivity for ZIKV NS1-specific IgA and IgM were detected in our study. ZIKV NS1 IgA/M (11%, 11/101) in combination was more frequently detected than ZIKV NS1 IgM (2%, 2/101) or ZIKV NS1 IgA (4%, 4/96) alone, especially in acute ZIKV cases with previous DENV exposure (14%, 10/72). Cytokine analysis showed that both ZIKV and DENV infections induced polyfunctional immunity, and the latter triggered more prolonged responses. The existence of significant differences in IL-4 and IL-10 levels between acute ZIKV and acute DENV cases suggested that IL-4 (p = 0.0176) and IL-10 (p = 0.0003) may represent biomarkers for acute ZIKV and acute DENV infections, respectively. Analysis of the association between increased cytokine levels and ZIKV symptoms indicated that CXCL10 (p = 0.0029) was associated with exanthema, while IL-5 (p = 0.0496) was linked to headache. The detection of ZIKV NS1 IgA and IgM in combination may enhance the diagnosis of early ZIKV infection, particularly when levels of IgM or IgA alone are low or undetectable. IL-4 and IL-10 may serve as targets for the development of diagnostic tools to detect ZIKV and DENV infections early, respectively, in flavivirus-endemic regions.

Heparan sulfate regulates IL-21 bioavailability and signal strength that control germinal center B cell selection and differentiation

In antibody responses, mutated germinal center B (B_GC) cells are positively selected for reentry or differentiation. As the products from GCs, memory B cells and antibody-secreting cells (ASCs) support high-affinity and long-lasting immunity. Positive selection of B_GC cells is controlled by signals received through the B cell receptor (BCR) and follicular helper T (T_FH) cell-derived signals, in particular costimulation through CD40. Here, we demonstrate that the T_FH cell effector cytokine interleukin-21 (IL-21) joins BCR and CD40 in supporting B_GC selection and reveal that strong IL-21 signaling prioritizes ASC differentiation in vivo. B_GC cells, compared with non-B_GC cells, show significantly reduced IL-21 binding and attenuated signaling, which is mediated by low cellular heparan sulfate (HS) sulfation. Mechanistically, N-deacetylase and N-sulfotransferase 1 (Ndst1)-mediated N-sulfation of HS in B cells promotes IL-21 binding and signal strength. Ndst1 is down-regulated in B_GC cells and up-regulated in ASC precursors, suggesting selective desensitization to IL-21 in B_GC cells. Thus, specialized biochemical regulation of IL-21 bioavailability and signal strength sets a balance between the stringency and efficiency of GC selection.

Step-dose IL-7 treatment promotes systemic expansion of T cells and alters immune cell landscape in blood and lymph nodes

We employed a dose-escalation regimen in rhesus macaques to deliver glycosylated IL-7, a cytokine critical for development and maintenance of T lymphocytes. IL-7 increased proliferation and survival of T cells and triggered several chemokines and cytokines. Induction of CXCL13 in lymph nodes (LNs) led to a remarkable increase of B cells in the LNs, proliferation of germinal center follicular T helper cells and elevated IL-21 levels suggesting an increase in follicle activity. Transcriptomics analysis showed induction of IRF-7 and Flt3L, which was linked to increased frequency of circulating plasmacytoid dendritic cells (pDCs) on IL-7 treatment. These pDCs expressed higher levels of CCR7, homed to LNs, and were associated with upregulation of type-1 interferon gene signature and increased production of IFN-α2a on TLR stimulation. Superior effects and dose-sparing advantage was observed by the step-dose regimen. Thus, IL-7 treatment leads to systemic effects involving both lymphoid and myeloid compartments.

Distinct roles of ORAI1 in T cell-mediated allergic airway inflammation and immunity to influenza A virus infection

T cell activation and function depend on Ca2+ signals mediated by store-operated Ca2+ entry (SOCE) through Ca2+ release-activated Ca2+ (CRAC) channels formed by ORAI1 proteins. We here investigated how SOCE controls T cell function in pulmonary inflammation during a T helper 1 (TH1) cell-mediated response to influenza A virus (IAV) infection and TH2 cell-mediated allergic airway inflammation. T cell-specific deletion of Orai1 did not exacerbate pulmonary inflammation and viral burdens following IAV infection but protected mice from house dust mite-induced allergic airway inflammation. ORAI1 controlled the expression of genes including p53 and E2F transcription factors that regulate the cell cycle in TH2 cells in response to allergen stimulation and the expression of transcription factors and cytokines that regulate TH2 cell function. Systemic application of a CRAC channel blocker suppressed allergic airway inflammation without compromising immunity to IAV infection, suggesting that inhibition of SOCE is a potential treatment for allergic airway disease.

A novel platform for the production of autologous human antibodies

At Research Genetic Cancer Centre, we have developed a novel method for the production of human monoclonal antibodies against a specific antigen of our choice (c-met) using isolated human blood cells. By mimicking nature, dendritic, CD4 and CD19 cells from healthy volunteers were driven towards Th2 immunity. Cell activation was succeeded by a cytokine cocktail, and IgG production was promoted by IgG class switching factors. IgG secretion was determined using both enzyme linked immunosorbent assay (ELISA) and Western blot as well as immunoglobulin heavy chain gamma polypeptide gene expression. Secreted antibody was further purified by affinity column chromatography against c-met peptide. Anti-c-met activity was determined using the purified antibody as primary antibody for c-met detection by ELISA, Western blot and flow cytometry. Finally, anti-c-met antibody efficiency was determined by MCF-7 viability assay. Plasma cell formation and IgG secretion took place after 6 days of culture. Plasma cells produced anti-c-met IgG antibody that significantly decreased MCF-7 breast cancer cell proliferation. To our knowledge, this is the first platform of its kind, generating fully human antibodies-on-demand using patient's own cells, bringing personalized, targeted therapy for cancer one step closer.

Neuropilin-1 (NRP1) expression distinguishes self-reactive helper T cells in systemic autoimmune disease

Pathogenic T helper cells (Th cells) that respond to self-antigen cannot be easily distinguished from beneficial Th cells. These cells can generate systemic autoimmune disease in response to widely expressed self-antigens. In this study, we have identified neuropilin-1 (NRP1) as a cell surface marker of self-reactive Th cells. NRP1⁺ Th cells, absent in non-regulatory T cell subsets in normal mice, appeared in models of systemic autoimmune disease and strongly correlated with disease symptoms. NRP1⁺ Th cells were greatly reduced in Nr4a2 cKO mice, which have reduced self-reactive responses but showed normal responses against exogenous antigens. Transfer of NRP1⁺ Th cells was sufficient to initiate or accelerate systemic autoimmune disease, and targeting NRP1-expressing Th cells therapeutically ameliorated SLE-like autoimmune symptoms in BXSB-Yaa mice. Peripheral NRP1⁺ Th cells were significantly increased in human SLE patients. Our data suggest that self-reactive Th cells can be phenotypically distinguished within the Th cell pool. These findings offer a novel approach to identify self-reactive Th cells and target them to treat systemic autoimmune disease.

Interleukin-21, acting beyond the immunological synapse, independently controls T follicular helper and germinal center B cells

Germinal centers (GCs), transient structures within B cell follicles and central to affinity maturation, require the coordinated behavior of T and B cells. IL-21, a pleiotropic T cell-derived cytokine, is key to GC biology through incompletely understood mechanisms. By genetically restricting production and receipt of IL-21 in vivo, we reveal how its independent actions on T and B cells combine to regulate the GC. IL-21 established the magnitude of the GC B cell response by promoting CD4⁺ T cell expansion and differentiation in a dose-dependent manner and with paracrine activity. Within GC, IL-21 specifically promoted B cell centroblast identity and, when bioavailability was high, plasma cell differentiation. Critically, these actions may occur irrespective of cognate T-B interactions, making IL-21 a general promoter of growth as distinct to a mediator of affinity-driven selection via synaptic delivery. This promiscuous activity of IL-21 explains the consequences of IL-21 deficiency on antibody-based immunity.

Trypanosoma cruzi blood trypomastigotes induce intense skeletal and cardiac muscle damage and Th1/ Th2 immune response in the acute phase of mice infected by the oral route

Oral acquisition of Trypanosoma cruzi is a foodborne transmission by juices and fruits contaminated with metacyclic trypomastigotes (MT) or by the ingestion of wild reservoirs infected with blood trypomastigotes (BT). In Mexico, hunting and food consumption of wild animals are current practices, which could represent a risk factor for oral infection in the rural population. In this work, Balb/c mice were inoculated by oral route with BT of a highly virulent T. cruzi Mexican strain (DTU I) to evaluate the establishment of the infection, and the humoral and cellular immune response in the acute phase of the infection. We show that BT induces blood and tissue parasitism producing an inflammatory process in the heart and skeletal muscle and low parasitism and inflammation in the digestive tract of orally infected mice. Besides, in the acute phase, the BT promotes splenomegaly, intense damage in skeletal and cardiac muscles, a humoral response dominated by the IgG isotype, and the expression of pro-inflammatory cytokines.

Mast Cell and Basophil Granule Proteases - In Vivo Targets and Function

Proteases are stored in very large amounts within abundant cytoplasmic granules of mast cells (MCs), and in lower amounts in basophils. These proteases are stored in their active form in complex with negatively charged proteoglycans, such as heparin and chondroitin sulfate, ready for rapid release upon MC and basophil activation. The absolute majority of these proteases belong to the large family of chymotrypsin related serine proteases. Three such enzymes are found in human MCs, a chymotryptic enzyme, the chymase, a tryptic enzyme, the tryptase and cathepsin G. Cathepsin G has in primates both chymase and tryptase activity. MCs also express a MC specific exopeptidase, carboxypeptidase A3 (CPA3). The targets and thereby the functions of these enzymes have for many years been the major question of the field. However, the fact that some of these enzymes have a relatively broad specificity has made it difficult to obtain reliable information about the biologically most important targets for these enzymes. Under optimal conditions they may cleave a relatively large number of potential targets. Three of these enzymes, the chymase, the tryptase and CPA3, have been shown to inactivate several venoms from snakes, scorpions, bees and Gila monster. The chymase has also been shown to cleave several connective tissue components and thereby to be an important player in connective tissue homeostasis. This enzyme can also generate angiotensin II (Ang II) by cleavage of Ang I and have thereby a role in blood pressure regulation. It also display anticoagulant activity by cleaving fibrinogen and thrombin. A regulatory function on excessive TH2 immunity has also been observed for both the chymase and the tryptase by cleavage of a highly selective set of cytokines and chemokines. The chymase also appear to have a protective role against ectoparasites such as ticks, mosquitos and leeches by the cleavage of their anticoagulant proteins. We here review the data that has accumulated concerning the potential in vivo functions of these enzymes and we discuss how this information sheds new light on the role of MCs and basophils in health and disease.

Co-Anchoring of Engineered Immunogen and Immunostimulatory Cytokines to Alum Promotes Enhanced-Humoral Immunity

Protein antigens are often combined with aluminum hydroxide (alum), the most commonly used adjuvant in licensed vaccines; yet the immunogenicity of alum-adjuvanted vaccines leaves much room for improvement. Here, the authors demonstrate a strategy for codelivering an immunostimulatory cytokine, the interleukin IL-21, with an engineered outer domain (eOD) human immunodeficiency virus gp120 Env immunogen eOD, bound together to alum to bolster the humoral immune response. In this approach, the immunogen and cytokine are co-anchored to alum particles via a short phosphoserine (pSer) peptide linker, promoting stable binding to alum and sustained bioavailability following injection. pSer-modified eOD and IL-21 promote enhanced lymphatic drainage and lead to accumulation of the vaccine in B cell follicles in the draining lymph nodes. This in turn promotes enhanced T follicular helper cell priming and robust germinal center responses as well as increased antigen-specific serum IgG titers. This is a general strategy for codelivery of immunostimulatory cytokine with immunogens providing a facile approach to modulate T cell priming and GC reactions toward enhanced protective immunity using the most common clinical vaccine adjuvant.

Mouse Liver B Cells Phagocytose Streptococcus pneumoniae and Initiate Immune Responses against Their Antigens

Recent studies have revealed that mammalian B cells ingest particulate Ags, such as bacteria, although little is known about the effect of this function on acquired immunity. We investigated the role of bacterium-phagocytosing B cells in acquired host immune responses. Cultured mouse liver B cells substantially phagocytosed serum-opsonized Streptococcus pneumoniae and produced IgM. On adoptive transfer of liver B cells that phagocytose S. pneumoniae labeled with pHrodo Red succinimidyl ester, recipient mice showed elevated plasma levels of IgG specific for bacterial Ags. In particular, the levels of IgG2a and IgG2b specific for pneumococcal surface protein A, as well as IgG3 for pneumococcal polysaccharide, were markedly increased compared with total IgG specific for each Ag. When phagocytic liver B cells were cultured with spleen CD4⁺ T cells obtained from mice primed with heat-killed S. pneumoniae 7 d before, they induced IL-2 production and proliferation of the CD4⁺ T cells, along with Th1 cytokine production. However, they induced neither the CD4⁺ T cell production of IL-21, a suggested marker promoting B cell proliferation and differentiation, nor the expression of genes important for somatic hypermutation or isotype switching; such responses were particularly evident when splenic B cells merely capturing S. pneumoniae without processing them were cultured with spleen CD4⁺ T cells. These findings suggest that phagocytic liver B cells may be involved in acquired immune responses by presenting derivative peptides to CD4⁺ T cells without their own somatic hypermutation or isotype switching.

T Cell Roles and Activity in Chronic Sclerosing Sialadenitis as IgG4-Related Disease: Current Concepts in Immunopathogenesis

IgG4-related disease is a multiorgan immunological fibroinflammatory disorder characterized by lymphoplasmacytic infiltration and fibrosis in multiple organs accompanied by high serum IgG4 levels. The salivary glands are the most common organs involved in this disease. Recently, chronic sclerosing sialadenitis affecting salivary glands, formerly known as Küttner's tumor, and Mikulicz's disease have been classified as a class of IgG4-related diseases. The etiopathobiology of IgG4-related disease is not fully understood. It has recently been hypothesized that the inflammatory and fibrotic process and the increased serum IgG4⁺ levels in IgG4-related disease are the result of an interaction between B cells and T helper cells, suggesting that T cells may play a key role in the pathogenesis of this disease. The aim of this review is to discuss the proposed roles of different T cell subsets in the pathogenesis of IgG4-related disease focusing on their roles in immunopathogenesis of IgG4-related sialadenitis.

Harnessing the B Cell Response in Kidney Transplantation - Current State and Future Directions

Despite dramatic improvement in kidney transplantation outcomes over the last decades due to advent of modern immunosuppressive agents, long-term outcomes remain poor. Antibody-mediated rejection (ABMR), a B cell driven process, accounts for the majority of chronic graft failures. There are currently no FDA-approved regimens for ABMR; however, several clinical trials are currently on-going. In this review, we present current mechanisms of B cell response in kidney transplantation, the clinical impact of sensitization and ABMR, the B cell response under current immunosuppressive regimens, and ongoing clinical trials for ABMR and desensitization treatment.

A Notch/IL-21 signaling axis primes bone marrow T cell progenitor expansion

Long-term impairment in T cell-mediated adaptive immunity is a major clinical obstacle following treatment of blood disorders with hematopoietic stem cell transplantation. Although T cell development in the thymus has been extensively characterized, there are significant gaps in our understanding of prethymic processes that influence early T cell potential. We have uncovered a Notch/IL-21 signaling axis in bone marrow common lymphoid progenitor (CLP) cells. IL-21 receptor expression was driven by Notch activation in CLPs, and in vivo treatment with IL-21 induced Notch-dependent CLP proliferation. Taking advantage of this potentially novel signaling axis, we generated T cell progenitors ex vivo, which improved repopulation of the thymus and peripheral lymphoid organs of mice in an allogeneic transplant model. Importantly, Notch and IL-21 activation were equally effective in the priming and expansion of human cord blood cells toward the T cell fate, confirming the translational potential of the combined treatment.

B cells in autoimmune hepatitis: bystanders or central players?

B cells are central for the adaptive immune system to mount successful immune responses not only as antibody producers but also as regulators of cellular immunity. These multifaceted features are also reflected in autoimmunity where autoreactive B cells can fuel disease by production of cytotoxic autoantibodies, presentation of autoantigens to autoreactive T cells, and secretion of cytokines and chemokines that either promote detrimental immune activation or impair regulatory T and B cells. The role of B cells and autoantibodies in autoimmune hepatitis (AIH) have been controversially discussed, with typical autoantibodies and hypergammaglobulinemia indicating a key role, while strong HLA class II association suggests T cells as key players. In this review, we summarize current knowledge on B cells in AIH and how different B cell subpopulations may drive AIH progression beyond autoantibodies. We also discuss recent findings of B cell-directed therapies in AIH.

Engineering early memory B-cell-like phenotype in hydrogel-based immune organoids

Memory B cells originate in response to antigenic stimulation in B-cell follicles of secondary lymphoid organs where naive B cells undergo maturation within a subanatomical microenvironment, the germinal centers. The understanding of memory B-cell immunology and its regulation is based primarily on sophisticated experiments that involve mouse models. To date, limited evidence exists on whether memory B cells can be successfully engineered ex vivo, specifically using biomaterials-based platforms that support the growth and differentiation of B cells. Here, we report the characterization of a recently reported maleimide-functionalized poly(ethylene glycol) (PEG) hydrogels as immune organoids towards the development of early memory B-cell phenotype and germinal center-like B cells. We demonstrate that the use of interleukin 9 (IL9), IL21, and bacterial antigen presentation as outer membrane-bound fragments drives the conversion of naive, primary murine B cells to early memory phenotype in ex vivo immune organoids. These findings describe the induction of early memory B-cell-like phenotype in immune organoids and highlight the potential of synthetic organoids as a platform for the future development of antigen-specific bona fide memory B cells for the study of the immune system and generation of therapeutic antibodies.

Supplying the trip to antibody production-nutrients, signaling, and the programming of cellular metabolism in the mature B lineage

The COVID pandemic has refreshed and expanded recognition of the vital role that sustained antibody (Ab) secretion plays in our immune defenses against microbes and of the importance of vaccines that elicit Ab protection against infection. With this backdrop, it is especially timely to review aspects of the molecular programming that govern how the cells that secrete Abs arise, persist, and meet the challenge of secreting vast amounts of these glycoproteins. Whereas plasmablasts and plasma cells (PCs) are the primary sources of secreted Abs, the process leading to the existence of these cell types starts with naive B lymphocytes that proliferate and differentiate toward several potential fates. At each step, cells reside in specific microenvironments in which they not only receive signals from cytokines and other cell surface receptors but also draw on the interstitium for nutrients. Nutrients in turn influence flux through intermediary metabolism and sensor enzymes that regulate gene transcription, translation, and metabolism. This review will focus on nutrient supply and how sensor mechanisms influence distinct cellular stages that lead to PCs and their adaptations as factories dedicated to Ab secretion. Salient findings of this group and others, sometimes exhibiting differences, will be summarized with regard to the journey to a distinctive metabolic program in PCs.

Interleukin 21 Receptor Affects Adipogenesis of Human Adipose-Derived Stem/Stromal Cells

Dysfunctions in adipose tissue cells are responsible for several obesity-related metabolic diseases. Understanding the process of adipocyte formation is thus fundamental for understanding these diseases. The adipocyte differentiation of adipose-derived stem/stromal cells (ADSCs) showed a reduction in the mRNA level of the interleukin 21 receptor (IL21R) during this process. Although the receptor has been associated with metabolic diseases, few studies have examined its function in stem cells. In this study, we used confocal immunofluorescence assays to determine that IL21R colocalizes with mitochondrial protein ATP5B, ALDH4A1, and the nucleus of human ADSCs. We demonstrated that silencing and overexpression of IL21R did not affect the cell proliferation and mitochondrial activity of ADSCs. However, IL21R silencing did reduce ADSC adipogenic capacity. Further studies are needed to understand the mechanism involved between IL21R and the adipogenic differentiation process.

Features of B Cell Responses Relevant to Allergic Disease

This Brief Review delves into B cell responses in the context of allergy. The primary contribution of B cells to allergy is the production of IgE, the Ab isotype that triggers immediate hypersensitivity reactions through the release of mediators from mast cells and basophils. B cells may also have protective roles in allergy, such as through the production of IgG or as regulatory B cells. In this review, I focus on the basic principles of B cell differentiation and discuss features relevant to allergic immune responses. In particular, I discuss: (1) class-switch recombination; (2) plasma cell differentiation; (3) germinal centers and affinity maturation; and (4) memory B cells and recall responses, with an emphasis on IgE, IgG1, and IgG4. I also consider how B cells may contribute to allergic responses independent of Ab production-for example, by serving as APCs.

A subset of follicular helper-like MAIT cells can provide B cell help and support antibody production in the mucosa

[Figure: see text].

Functional roles of cytokines in infectious disease associated colorectal carcinogenesis

Infection processes induce various soluble factors that are carcinogens in humans; therefore, research into the soluble factors of chronic disease released from cells that have been infected with parasites is warranted. Parasitic infections in host cells release high levels of IFNγ. Studies have hypothesised that parasitosis-associated carcinogenesis might be analogous to colorectal cancers developed from inflammatory bowel diseases, whereby various cytokines and chemokines are secreted during chronic inflammation. IL-18 and IL-21 are other factors that might be involved in the development of colorectal cancer in schistosomiasis patients and patients with other infections. IL-21 has profound effects on tumour growth and immunosurveillance of colitis-associated tumourigenesis, thereby emphasising its involvement in the pathogenesis of colorectal cancer. The prominent role of IL-21 in antitumour effects greatly depends on the enhanced cytolytic activity of NK cells and the pathogenic role of IL-21, which is often associated with enhanced risks of cancer and chronic inflammatory processes. As IL-15 is also related to chronic disease, it is believed to also play a role in the antitumour effect of colorectal carcinogenesis. IL-15 generates and maintains long-term CD8⁺ T cell immunity against T. gondii to control the infection of intracellular pathogens. The lack of IL-15 in mice contributes to the downregulation of the IFNγ-producing CD4⁺ T cell response against acute T. gondii infection. IL-15 induces hyperplasia and supports the progressive growth of colon cancer via multiple functions. The limited role of IL-15 in the development of NK and CD8⁺ T cells suggests that there may be other cytokines compensating for the loss of the IL-15 gene.

The concerted change in the distribution of cell cycle phases and zone composition in germinal centers is regulated by IL-21

Humoral immune responses require germinal centres (GC) for antibody affinity maturation. Within GC, B cell proliferation and mutation are segregated from affinity-based positive selection in the dark zone (DZ) and light zone (LZ) substructures, respectively. While IL-21 is known to be important in affinity maturation and GC maintenance, here we show it is required for both establishing normal zone representation and preventing the accumulation of cells in the G1 cell cycle stage in the GC LZ. Cell cycle progression of DZ B cells is unaffected by IL-21 availability, as is the zone phenotype of the most highly proliferative GC B cells. Collectively, this study characterises the development of GC zones as a function of time and B cell proliferation and identifies IL-21 as an important regulator of these processes. These data help explain the requirement for IL-21 in normal antibody affinity maturation.

Heterogeneity of Early Host Response to Infection with Four Low-Pathogenic H7 Viruses with a Different Evolutionary History in the Field

Once low-pathogenic avian influenza viruses (LPAIVs) of the H5 and H7 subtypes from wild birds enter into poultry species, there is the possibility of them mutating into highly pathogenic avian influenza viruses (HPAIVs), resulting in severe epizootics with up to 100% mortality. This mutation from a LPAIV to HPAIV strain is the main cause of an AIV’s major economic impact on poultry production. Although AIVs are inextricably linked to their hosts in their evolutionary history, the contribution of host-related factors in the emergence of HPAI viruses has only been marginally explored so far. In this study, transcriptomic sequencing of tracheal tissue from chickens infected with four distinct LP H7 viruses, characterized by a different history of pathogenicity evolution in the field, was implemented. Despite the inoculation of a normalized infectious dose of viruses belonging to the same subtype (H7) and pathotype (LPAI), the use of animals of the same age, sex and species as well as the identification of a comparable viral load in the target samples, the analyses revealed a heterogeneity in the gene expression profile in response to infection with each of the H7 viruses administered.

Follicular helper and follicular regulatory T cell subset imbalance is associated with higher activated B cells and abnormal autoantibody production in primary anti-phospholipid syndrome patients

Primary anti-phospholipid antibody syndrome (pAPS) is a multi-organ autoimmune disease, and autoantibodies are involved in its pathogenesis. Follicular helper T cells (Tfh) and follicular regulatory T cells (Tfr) are critical for B cell maturation and antibody production, but their roles in pAPS remain unknown. We enrolled 32 pAPS patients and 23 healthy controls (HCs) and comprehensively analyzed circulating Tfh and Tfr, as well as their subsets, using flow cytometry. Clinical data including autoantibody levels were collected and their correlations with Tfh and Tfr subsets were analyzed. In addition, correlation analyses between B cell functional subsets and Tfh and Tfr were performed. Changes and potential effects of serum cytokines on Tfr and Tfh were further explored. We found the circulating Tfr was significantly decreased while Tfh and Tfh/Tfr ratios were increased in pAPS patients. Tfh2, inducible T cell co-stimulator (ICOS)+  programmed cell death 1 (PD-1)+  Tfh and Ki-67+  Tfh percentages were elevated, while CD45RA- forkhead box protein 3 (FoxP3)hi , Helios+ , T cell immunoglobulin and ITIM (TIGIT)+  and Ki-67+  Tfr percentages were decreased in pAPS patients. New memory B cells and plasmablasts were increased and altered B cell subsets and serum autoantibodies were positively correlated with Tfh, Tfh2, ICOS+ PD-1+  Tfh cells and negatively associated with Tfr, CD45RA- FoxP3hi Tfr and Helios+  Tfr cells. In addition, pAPS with LA/aCL/β2GPI autoantibodies showed lower functional Tfr subsets and higher activated Tfh subsets. Serum interleukin (IL)-4, IL-21, IL-12 and transforming growth factor (TGF)-β1 were up-regulated and associated with Tfh and Tfr subset changes. Our study demonstrates that imbalance of circulating Tfr and Tfh, as well as their functional subsets, is associated with abnormal autoantibody levels in pAPS, which may contribute to the pathogenesis of pAPS.