Induction of IgG2a class switching in B cells by IL-27

Revisiting the role of IL-27 in obesity-related metabolic diseases: safeguard or perturbation?

The prevalence of metabolic diseases, such as obesity, has been steadily increasing in recent years, posing a significant threat to public health. Therefore, early identification and intervention play a crucial role. With the deepening understanding of the etiology of metabolic diseases, novel therapeutic targets are emerging for the treatment of obesity, lipid metabolism disorders, cardiovascular and cerebrovascular diseases, glucose metabolism disorders, and other related metabolic conditions. IL-27, as a multi-potent cytokine, holds great promise as a potential candidate target in this regard. This article provides a comprehensive review of the latest findings on IL-27 expression and signal transduction in the regulation of immune inflammatory cells, as well as its implications in obesity and other related metabolic diseases. Furthermore, it explores the potential of IL-27 as a novel therapeutic target for the treatment of obesity and metabolic disorders. Finally, an overview is presented on both the opportunities and challenges associated with targeting IL-27 for therapeutic interventions.

Harnessing IL-27: challenges and potential in cancer immunotherapy

IL-27 is structurally an immune-enhancing and pleiotropic two-chain cytokine associated with IL-12 and IL-6 families. IL-27 contains two subunits, namely IL-27p28 and EBI3. A heterodimer receptor of IL-27, composed of IL27Rα (WSX1) and IL6ST (gp130) chains, mediates the IL-27 function following the activation of STAT1 and STAT3 signaling pathways. Specifically, IL-27 is identified as augmenting cytokine of immune responses, including Th1 cell differentiation, TCd4 + cell proliferation, and IFN-γ production with the help of IL-12. According to several published studies, due to the pro-inflammatory or anti-inflammatory functions of cytokine related to the biological context in various disorders and diseases, IL-27 has been considered a complex regulator of the immune system. Surprisingly, the dual role of IL-27, the same as the double-edged sword, has also been evidenced in clinical models of various hematological or solid tumors. Predominantly, Il-27 applies anti-tumor functions by inducing the responses of a cytotoxic T lymphocyte (CTL) and Th1 and suppressing the growth, proliferation, angiogenesis, invasiveness, metastasis, and survival of tumor cells. On the other hand, IL-27 may also play a protumor role in cancers and induce tumor progression. The current update study aimed to summarize the protumor anti-tumor and biological functions of IL-27 in different hematological malignancies and solid tumors.

An updated advancement of bifunctional IL-27 in inflammatory autoimmune diseases

Interleukin-27 (IL-27) is a member of the IL-12 family. The gene encoding IL-27 is located at chromosome 16p11. IL-27 is considered as a heterodimeric cytokine, which consists of Epstein-Barr virus (EBV)-induced gene 3 (Ebi3) and IL-27p28. Based on the function of IL-27, it binds to receptor IL-27rα or gp130 and then regulates downstream cascade. To date, findings show that the expression of IL-27 is abnormal in different inflammatory autoimmune diseases (including systemic lupus erythematosus, rheumatoid arthritis, Sjogren syndrome, Behcet's disease, inflammatory bowel disease, multiple sclerosis, systemic sclerosis, type 1 diabetes, Vogt-Koyanagi-Harada, and ankylosing spondylitis). Moreover, in vivo and in vitro studies demonstrated that IL-27 is significantly in3volved in the development of these diseases by regulating innate and adaptive immune responses, playing either an anti-inflammatory or a pro-inflammatory role. In this review, we comprehensively summarized information about IL-27 and autoimmunity based on available evidence. It is hoped that targeting IL-27 will hold great promise in the treatment of inflammatory autoimmune disorders in the future.

JAK1/JAK2 degraders based on PROTAC for topical treatment of atopic dermatitis

Atopic dermatitis (AD) is a prevalent chronic inflammatory skin disease. The Janus kinase (JAK) has been identified as a target in AD, as it regulates specific inflammatory genes and adaptive immune responses. However, the efficacy of topically applied JAK inhibitors in AD is limited due to the unique structure of skin. We synthesized JAK1/JAK2 degraders (JAPT) based on protein degradation targeting chimeras (PROTACs) and prepared them into topical preparations. JAPT exploited the E3 ligase to mediate ubiquitination and degradation of JAK1/JAK2, offering a promising AD therapeutic approach with low frequency and dosage. In vitro investigations demonstrated that JAPT effectively inhibited the release of pro-inflammatory cytokines and reduced inflammation by promoting the degradation of JAK. In vivo studies further confirmed the efficacy of JAPT in degrading JAK1/JAK2, leading to a significant suppression of type I, II, and III adaptive immunity. Additionally, JAPT demonstrated a remarkable reduction in AD severity, as evidenced by improved skin lesion clearance and AD severity scores (SCORAD). Our study revealed the therapeutic potential of JAPT, surpassing conventional JAK inhibitors in the treatment of AD, which suggested that JAPT could be a promising topically applied anti-AD drug targeting the JAK-STAT signaling pathway.

CD200Fc limits dendritic cell and B-cell activation during chronic allergen exposures

Allergic asthma is a chronic inflammatory disease characterized by Th2, conventional dendritic cell, and B-cell activation. In addition to excessive inflammation, asthma pathogenesis includes dysregulation of anti-inflammatory pathways, such as the CD200/CD200R pathway. Thus, we investigated whether a CD200R agonist, CD200Fc, could disrupt the inflammatory cascade in chronic allergic asthma pathogenesis using a mice model of experimental asthma. Mice were exposed to house dust mites for 5 wk, and CD200Fc treatment was initiated after chronic inflammation was established (starting on week 4). We demonstrate that chronic house dust mite exposure altered CD200 and CD200R expression on lung immune cell populations, including upregulation of CD200 on alveolar macrophages and reduced expression of CD200 on conventional dendritic cells. CD200Fc treatment does not change bronchoalveolar cellular infiltration, but it attenuates B-cell activation and skews the circulating immunoglobulin profile toward IgG2a. This is accompanied by reduced activation of conventional dendritic cells, including lower expression of CD40, especially on conventional dendritic cell subset 2 CD200R+. Furthermore, we confirm that CD200Fc can directly modulate conventional dendritic cell activation in vitro using bone marrow-derived dendritic cells. Thus, the CD200/CD200R pathway is dysregulated during chronic asthma pathogenesis, and the CD200R agonist modulates B-cell and dendritic cell activation but, in our chronic model, is not sufficient to alter inflammation measured in bronchoalveolar lavage.

Tetraspanin Tspan8 restrains interferon signaling to stabilize intestinal epithelium by directing endocytosis of interferon receptor

Inflammation can impair intestinal barrier, while increased epithelial permeability can lead to inflammation. In this study, we found that the expression of Tspan8, a tetraspanin expressed specifically in epithelial cells, is downregulated in mouse model of ulcerative disease (UC) but correlated with those of cell-cell junction components, such as claudins and E-cadherin, suggesting that Tspan8 supports intestinal epithelial barrier. Tspan8 removal increases intestinal epithelial permeability and upregulates IFN-γ-Stat1 signaling. We also demonstrated that Tspan8 coalesces with lipid rafts and facilitates IFNγ-R1 localization at or near lipid rafts. As IFN-γ induces its receptor undergoing clathrin- or lipid raft-dependent endocytosis and IFN-γR endocytosis plays an important role in Jak-Stat1 signaling, our analysis on IFN-γR endocytosis revealed that Tspan8 silencing impairs lipid raft-mediated but promotes clathrin-mediated endocytosis of IFN-γR1, leading to increased Stat1 signaling. These changes in IFN-γR1 endocytosis upon Tspan8 silencing correlates with fewer lipid raft component GM1 at the cell surface and more clathrin heavy chain in the cells. Our findings indicate that Tspan8 determines the IFN-γR1 endocytosis route, to restrain Stat1 signaling, stabilize intestine epithelium, and subsequently prevent intestine from inflammation. Our finding also implies that Tspan8 is needed for proper endocytosis through lipid rafts.

IgG1-Dominant Antibody Response Induced by Recombinant Trimeric SARS-CoV-2 Spike Protein with PIKA Adjuvant

Recombinant trimeric SARS-CoV-2 Spike protein with PIKA (polyI:C) adjuvant induces potent and durable neutralizing antibodies that protect against multiple SARS-CoV-2 variants. The immunoglobulin subclasses of viral-specific antibodies remain unknown, as do their glycosylation status on Fc regions. In this study, we analyzed immunoglobulins adsorbed by plate-bound recombinant trimeric SARS-CoV-2 Spike protein from serum of Cynomolgus monkey immunized by recombinant trimeric SARS-CoV-2 Spike protein with PIKA (polyI:C) adjuvant. The results showed that IgG1 was the dominant IgG subclass as revealed by ion mobility mass spectrometry. The average percentage of Spike protein-specific IgG1 increased to 88.3% as compared to pre-immunization. Core fucosylation for Fc glycopeptide of Spike protein-specific IgG1 was found to be higher than 98%. These results indicate that a unique Th1-biased, IgG1-dominant antibody response was responsible for the effectiveness of PIKA (polyI:C) adjuvant. Vaccine-induced core-fucosylation of IgG1 Fc region may reduce incidence of severe COVID-19 disease associated with overstimulation of FCGR3A by afucosylated IgG1.

Human T-bet governs the generation of a distinct subset of CD11chighCD21low B cells

High-level expression of the transcription factor T-bet characterizes a phenotypically distinct murine B cell population known as "age-associated B cells" (ABCs). T-bet-deficient mice have reduced ABCs and impaired humoral immunity. We describe a patient with inherited T-bet deficiency and largely normal humoral immunity including intact somatic hypermutation, affinity maturation and memory B cell formation in vivo, and B cell differentiation into Ig-producing plasmablasts in vitro. Nevertheless, the patient exhibited skewed class switching to IgG1, IgG4, and IgE, along with reduced IgG2, both in vivo and in vitro. Moreover, T-bet was required for the in vivo and in vitro development of a distinct subset of human B cells characterized by reduced expression of CD21 and the concomitantly high expression of CD19, CD20, CD11c, FCRL5, and T-bet, a phenotype that shares many features with murine ABCs. Mechanistically, human T-bet governed CD21^loCD11c^hi B cell differentiation by controlling the chromatin accessibility of lineage-defining genes in these cells: FAS, IL21R, SEC61B, DUSP4, DAPP1, SOX5, CD79B, and CXCR4. Thus, human T-bet is largely redundant for long-lived protective humoral immunity but is essential for the development of a distinct subset of human CD11c^hiCD21^lo B cells.

Type I Interferons Promote Germinal Centers Through B Cell Intrinsic Signaling and Dendritic Cell Dependent Th1 and Tfh Cell Lineages

Type I interferons (IFNs) are essential for antiviral immunity, appear to represent a key component of mRNA vaccine-adjuvanticity, and correlate with severity of systemic autoimmune disease. Relevant to all, type I IFNs can enhance germinal center (GC) B cell responses but underlying signaling pathways are incompletely understood. Here, we demonstrate that a succinct type I IFN response promotes GC formation and associated IgG subclass distribution primarily through signaling in cDCs and B cells. Type I IFN signaling in cDCs, distinct from cDC1, stimulates development of separable Tfh and Th1 cell subsets. However, Th cell-derived IFN-γ induces T-bet expression and IgG2c isotype switching in B cells prior to this bifurcation and has no evident effects once GCs and bona fide Tfh cells developed. This pathway acts in synergy with early B cell-intrinsic type I IFN signaling, which reinforces T-bet expression in B cells and leads to a selective amplification of the IgG2c+ GC B cell response. Despite the strong Th1 polarizing effect of type I IFNs, the Tfh cell subset develops into IL-4 producing cells that control the overall magnitude of the GCs and promote generation of IgG1+ GC B cells. Thus, type I IFNs act on B cells and cDCs to drive GC formation and to coordinate IgG subclass distribution through divergent Th1 and Tfh cell-dependent pathways.

Age-associated B cells in viral infection

Age-associated B cells (ABCs) are a recently identified, unique B cell population that displays both protective and pathogenic characteristics, depending on the context. A major role of ABCs is to protect from viral infection. ABCs expand during an array of viral infections and display various functional capacities, including secretion of antibodies and activation of T cells. Following resolution of infection, ABCs appear to persist and play a crucial role in memory and recall responses. Here, we review the currently understanding of ABCs in the antiviral response in both humans and mice. We discuss avenues for future research, including the impact of sex on the ABC population and heterogeneity of ABCs between contexts.

The JAK/STAT signaling pathway: from bench to clinic

The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway was discovered more than a quarter-century ago. As a fulcrum of many vital cellular processes, the JAK/STAT pathway constitutes a rapid membrane-to-nucleus signaling module and induces the expression of various critical mediators of cancer and inflammation. Growing evidence suggests that dysregulation of the JAK/STAT pathway is associated with various cancers and autoimmune diseases. In this review, we discuss the current knowledge about the composition, activation, and regulation of the JAK/STAT pathway. Moreover, we highlight the role of the JAK/STAT pathway and its inhibitors in various diseases.

CD38 Deficiency Ameliorates Chronic Graft-Versus-Host Disease Murine Lupus via a B-Cell-Dependent Mechanism

The absence of the mouse cell surface receptor CD38 in Cd38^−/− mice suggests that this receptor acts as a positive regulator of inflammatory and autoimmune responses. Here, we report that, in the context of the chronic graft-versus-host disease (cGVHD) lupus inducible model, the transfer of B6.C-H2bm12/KhEg(bm12) spleen cells into co-isogenic Cd38^−/− B6 mice causes milder lupus-like autoimmunity with lower levels of anti-ssDNA autoantibodies than the transfer of bm12 spleen cells into WT B6 mice. In addition, significantly lower percentages of Tfh cells, as well as GC B cells, plasma cells, and T-bet⁺CD11c^hi B cells, were observed in Cd38^−/− mice than in WT mice, while the expansion of Treg cells and Tfr cells was normal, suggesting that the ability of Cd38^−/− B cells to respond to allogeneic help from bm12 CD4⁺ T cells is greatly diminished. The frequencies of T-bet⁺CD11c^hi B cells, which are considered the precursors of the autoantibody-secreting cells, correlate with anti-ssDNA autoantibody serum levels, IL-27, and sCD40L. Proteomics profiling of the spleens from WT cGVHD mice reflects a STAT1-driven type I IFN signature, which is absent in Cd38^−/− cGVHD mice. Kidney, spleen, and liver inflammation was mild and resolved faster in Cd38^−/− cGVHD mice than in WT cGVHD mice. We conclude that CD38 in B cells functions as a modulator receptor that controls autoimmune responses.

Recombinant Lactococcus Lactis Displaying Omp31 Antigen of Brucella melitensis Can Induce an Immunogenic Response in BALB/c Mice

Since Brucella infection mostly occurs through the mucosal surfaces, immune response induced by vaccine that is delivered by a way of mucosal route can be drastically enhanced to control the brucellosis. Omp31is the major outer membrane protein of Brucella, and is considered as a protective antigen against Brucella infection. Accordingly, Lactococcus lactis has been used as an antigen-delivering vector to develop a vaccine-induced mucosal response for having a safer vaccination against brucellosis. A designed omp31 gene fused to the usp45 signal peptide and M6 cell wall anchor was sub cloned in the pNZ7021 expression vector, and a recombinant L. lactis displaying Omp31 was constructed. Omp31 protein expression was confirmed using Western blotting and immunofluorescence analysis. Animals were orally and intraperitoneally immunized with live or killed L. lactis expressing Omp31, respectively. The humoral and cellular immune responses were evaluated by measuring the specific cytokines and antibodies. sIgA, serum IgA, IgM, and total IgG antibodies significantly increased in the mice immunized with live recombinant L. lactis expressing Omp31 and also serum IgM, and total IgG antibodies significantly increased in mice immunized with killed recombinant L. lactis expressing Omp31. Among IgG subtypes, IgG2a response was significantly higher in both groups compared to IgG1. In mice groups immunized with recombinant L. lactis, the IFN-γ and IL-10 level elevated; however, there was no change in the level of IL-4. These results indicated that recombinants L. lactis induce both humoral and cellular immune responses in mice, and also vaccines based on L. lactis-derived live carriers are promising interventions against Brucella melitensis infections.

Interleukin-27 and Its Diverse Effects on Bacterial Infections

Innate and adaptive immune responses against pathogens are known to be carefully orchestrated by specific cytokines that initiate and down regulate immune cell functions from the initial infection through tissue repair and homeostasis. However, some cytokines, including interleukin-27, are expressed at multiple phases of the infection, such that their pro and anti-inflammatory functions have been difficult to interpret. As elucidation of specific cytokine functions throughout infection is central to our understanding of protective vs. susceptible immunity and return to homeostasis vs. prolonged inflammation leading to septic shock, here we review the literature on IL-27 signaling and the various functions of this heterodimeric ligand member of the IL-12 cytokine family. Canonically, IL-27 is produced by antigen-presenting cells, and is thought of as an immunostimulatory cytokine due to its capacity to induce Th1 differentiation. However, many studies have also identified various immunosuppressive effects of IL-27 signaling, including suppression of Th17 differentiation and induction of co-inhibitory receptors on T cells. Thus, the exact role of IL-27 in the context of infectious diseases remains a topic of debate and active research. Additionally, as recent interest has focused on clinical management of acute vs. chronic infections, and life-threatening "cytokine storm" from sepsis, we propose a hypothetical model to explain the biphasic role of IL-27 during the early and late phases of immune responses to reconcile its known pro and anti-inflammatory functions, which could be therapeutically regulated to improve patient outcomes of infection.

Epithelial-immune cell interplay in primary Sjögren syndrome salivary gland pathogenesis

In primary Sjögren syndrome (pSS), the function of the salivary glands is often considerably reduced. Multiple innate immune pathways are likely dysregulated in the salivary gland epithelium in pSS, including the nuclear factor-κB pathway, the inflammasome and interferon signalling. The ductal cells of the salivary gland in pSS are characteristically surrounded by a CD4⁺ T cell-rich and B cell-rich infiltrate, implying a degree of communication between epithelial cells and immune cells. B cell infiltrates within the ducts can initiate the development of lymphoepithelial lesions, including basal ductal cell hyperplasia. Vice versa, the epithelium provides chronic activation signals to the glandular B cell fraction. This continuous stimulation might ultimately drive the development of mucosa-associated lymphoid tissue lymphoma. This Review discusses changes in the cells of the salivary gland epithelium in pSS (including acinar, ductal and progenitor cells), and the proposed interplay of these cells with environmental stimuli and the immune system. Current therapeutic options are insufficient to address both lymphocytic infiltration and salivary gland dysfunction. Successful rescue of salivary gland function in pSS will probably demand a multimodal therapeutic approach and an appreciation of the complicity of the salivary gland epithelium in the development of pSS.

Impaired Interleukin-27-Mediated Control of CD4+ T Cell Function Impact on Ectopic Lymphoid Structure Formation in Patients With Sjögren's Syndrome

OBJECTIVE

Ectopic lymphoid structures (ELS) develop at sites of infection, autoimmunity, and cancer. In patients with Sjögren's syndrome (SS), ELS support autoreactive B cell activation and lymphomagenesis. Interleukin-27 (IL-27) is a key regulator of adaptive immunity and limits Th17 cell-driven pathology. We undertook this study to elucidate the role of IL-27 in ELS formation and function in autoimmunity using a murine model of sialadenitis and in patients with SS.

METHODS

ELS formation was induced in wild-type and Il27ra-/- mice via salivary gland (SG) cannulation of a replication-deficient adenovirus in the presence or absence of IL-17A neutralization. In SG biopsy samples, IL-27-producing cells were identified by multicolor immunofluorescence microscopy. Lesional and circulating IL-27 levels were determined by gene expression and enzyme-linked immunosorbent assay. The in vitro effect of IL-27 on T cells was assessed using fluorescence-activated cell sorting and cytokine release.

RESULTS

In experimental sialadenitis, Il27ra-/- mice had larger and more hyperactive ELS (focus score; P < 0.001), increased autoimmunity, and an expanded Th17 response (P < 0.001), compared to wild-type mice. IL-17 blockade in Il27ra-/- mice suppressed the aberrant ELS response (B and T cell reduction against control; P < 0.01). SS patients displayed increased circulating IL-27 levels (P < 0.01), and in SG biopsy samples, IL-27 was expressed by DC-LAMP+ dendritic cells in association with CD3+ T cells. Remarkably, in SS T cells (but not in T cells from patients with rheumatoid arthritis or healthy controls), IL-27-mediated suppression of IL-17 secretion was severely impaired and associated with an aberrant interferon-γ release upon IL-27 stimulation.

CONCLUSION

Our data indicate that the physiologic ability of IL-27 to limit the magnitude and function of ELS through control of Th17 cell expansion is severely impaired in SS patients, highlighting a defective immunoregulatory checkpoint in this condition.

Gene expression profiling of epithelium-associated FcRL4+ B cells in primary Sjögren's syndrome reveals a pathogenic signature

In primary Sjögren's syndrome (pSS), FcRL4⁺ B cells are present in inflamed salivary gland tissue, within or in close proximity to ductal epithelium. FcRL4 is also expressed by nearly all pSS-related mucosa-associated lymphoid tissue (MALT) B cell lymphomas, linking FcRL4 expression to lymphomagenesis. Whether glandular FcRL4⁺ B cells are pathogenic, how these cells originate, and how they functionally differ from FcRL4^- B cells in pSS is unclear. This study aimed to investigate the phenotype and function of FcRL4⁺ B cells in the periphery and parotid gland tissue of patients with pSS. First, circulating FcRL4⁺ B cells from 44 pSS and 54 non-SS-sicca patients were analyzed by flow cytometry. Additionally, RNA sequencing of FcRL4⁺ B cells sorted from parotid gland cell suspensions of 6 pSS patients was performed. B cells were sorted from cell suspensions as mini bulk (5 cells/well) based on the following definitions: CD19⁺CD27^-FcRL4^- ('naive'), CD19⁺CD27⁺FcRL4^- ('memory'), and CD19⁺FcRL4⁺ B cells. We found that, although FcRL4⁺ B cells were not enriched in blood in pSS compared with non-SS sicca patients, these cells generally exhibited a pro-inflammatory phenotype. Genes coding for CD11c (ITGAX), T-bet (TBX21), TACI (TNFRSF13B), Src tyrosine kinases and NF-κB pathway-related genes were, among others, significantly upregulated in glandular FcRL4⁺ B cells versus FcRL4^- B cells. Pathway analysis showed upregulation of B cell activation, cell cycle and metabolic pathways. Thus, FcRL4⁺ B cells in pSS exhibit many characteristics of chronically activated, pro-inflammatory B cells and their gene expression profile suggests increased risk of lymphomagenesis. We postulate that these cells contribute significantly to the epithelial damage seen in the glandular tissue and that FcRL4⁺ B cells are an important treatment target in pSS.

CD11c+ B Cells Are Mainly Memory Cells, Precursors of Antibody Secreting Cells in Healthy Donors

CD11c+ B cells have been reported to be increased in autoimmune diseases, but they are detected in the blood of healthy individuals as well. We aimed to characterize CD11c+ B cells from healthy donors by flow cytometry, microarray analysis, and in vitro functional assays. Here, we report that CD11c+ B cells are a distinct subpopulation of B cells, enriched in the memory subpopulation even if their phenotype is heterogeneous, with overexpression of genes involved in B-cell activation and differentiation as well as in antigen presentation. Upon activation, CD11c+ B cells can differentiate into antibody-secreting cells, and CD11c could be upregulated in CD11c- B cells by B-cell receptor activation. Finally, we show that patients with pemphigus, an autoimmune disease mediated by B cells, have a decreased frequency of CD11c+ B cell after treatment, relative to baseline. Our findings show that CD11c+ B cells are mainly memory B cells prone to differentiate into antibody secreting cells that accumulate with age, independently of gender.

Activation and IL-10 production of specific CD4+ T cells are regulated by IL-27 during chronic infection with Plasmodium chabaudi

IL-27, a regulatory cytokine, plays critical roles in the prevention of immunopathology during Plasmodium infection. We examined these roles in the immune responses against Plasmodium chabaudi infection using the Il-27ra^-/- mice. While IL-27 was expressed at high levels during the early phase of the infection, enhanced CD4⁺ T cell function and reduction in parasitemia were observed mainly during the chronic phase in the mutant mice. In mice infected with P. chabaudi and cured with drug, CD4⁺ T cells in the Il-27ra^-/- mice exhibited enhanced CD4⁺ T-cell responses, indicating the inhibitory role of IL-27 on the protective immune responses. To determine the role of IL-27 in detail, we performed CD4⁺ T-cell transfer experiments. The Il-27ra^-/- and Il27p28^-/- mice were first infected with P. chabaudi and then cured using drug treatment. Plasmodium-antigen primed CD4⁺ T cells were prepared from these mice and transferred into the recipient mice, followed by infection with the heterologous parasite P. berghei ANKA. Il-27ra^-/- CD4⁺ T cells in the infected recipient mice did not produce IL-10, indicating that IL-10 production by primed CD4⁺ T cells is IL-27 dependent. Il27p28^-/- CD4⁺ T cells that were primed in the absence of IL-27 exhibited enhanced recall responses during the challenge infection with P. berghei ANKA, implying that IL-27 receptor signaling during the primary infection affects recall responses in the long-term via the regulation of the memory CD4⁺ T cell generation. These features highlighted direct and time-transcending roles of IL-27 in the regulation of immune responses against chronic infection with Plasmodium parasites.

Interleukin-27 promotes CD8+ T cell reconstitution following antibody-mediated lymphoablation

Antibody-mediated lymphoablation is used in solid organ and stem cell transplantation and autoimmunity. Using murine anti-thymocyte globulin (mATG) in a mouse model of heart transplantation, we previously reported that the homeostatic recovery of CD8+ T cells requires help from depletion-resistant memory CD4+ T cells delivered through CD40-expressing B cells. This study investigated the mechanisms by which B cells mediate CD8+ T cell proliferation in lymphopenic hosts. While CD8+ T cell recovery required MHC class I expression in the host, the reconstitution occurred independently of MHC class I, MHC class II, or CD80/CD86 expression on B cells. mATG lymphoablation upregulated the B cell expression of several cytokine genes, including IL-15 and IL-27, in a CD4-dependent manner. Neither treatment with anti-CD122 mAb nor the use of IL-15Rα-/- recipients altered CD8+ T cell recovery after mATG treatment, indicating that IL-15 may be dispensable for T cell proliferation in our model. Instead, IL-27 neutralization or the use of IL-27Rα-/- CD8+ T cells inhibited CD8+ T cell proliferation and altered the phenotype and cytokine profile of reconstituted CD8+ T cells. Our findings uncover what we believe is a novel role of IL-27 in lymphopenia-induced CD8+ T cell proliferation and suggest that targeting B cell-derived cytokines may increase the efficacy of lymphoablation and improve transplant outcomes.

IL-27 promotes NK cell effector functions via Maf-Nrf2 pathway during influenza infection

Influenza virus targets epithelial cells in the upper respiratory tract. Natural Killer (NK) cell-mediated early innate defense responses to influenza infection include the killing of infected epithelial cells and generation of anti-viral cytokines including interferon gamma (IFN-γ). To date, it is unclear how the underlying cytokine milieu during infection regulates NK cell effector functions. Our data show during influenza infection myeloid cell-derived IL-27 regulates the early-phase effector functions of NK cells in the bronchioalveolar and lung tissue. Lack of IL-27R (Il27ra^−/−) or IL-27 (Ebi3^−/−) resulted in impaired NK cell effector functions including the generation of anti-viral IFN-γ responses. We identify CD27⁺CD11b⁺ NK cells as the primary subset that expresses IL-27R, which predominantly produces IFN-γ within the upper respiratory tract of the infected mice. IL-27 alone was incapable of altering the effector functions of NK cells. However, IL-27 sensitizes NK cells to augment both in vitro and in vivo responses mediated via the NKG2D receptor. This ‘priming’ function of IL-27 is mediated partly via transcriptional pathways regulated by Mafs and Nrf2 transcriptionally regulating TFAM and CPT1. Our data for the first time establishes a novel role for IL-27 in regulating early-phase effector functions of NK cells during influenza infection.

T-bet+ memory B cells: Generation, function, and fate

B cells expressing the transcription factor T-bet have emerged as participants in a number of protective and pathogenic immune responses. T-bet+ B cells characteristically differentiate in response to combined Toll-like receptor and cytokine signaling, contribute to protective immunity against intracellular pathogens via IgG2a/c production and antibody-independent mechanisms, and are prone to produce autoantibodies. Despite recent advances, a number of questions remain regarding the basic biology of T-bet+ B cells and their functional niche within the immune system. Herein, we review the discovery and defining characteristics of the T-bet+ B cell subset in both mice and humans. We further discuss their origins, the basis for their persistence, and their potential fate in vivo. Evidence indicates that T-bet+ B cells represent a distinct, germinal center-derived memory population that may serve as an important therapeutic target for the improvement of humoral immunity and prevention of autoimmunity.

Molecular regulation of peripheral B cells and their progeny in immunity

In this review, Boothby et al. summarize some salient advances toward elucidation of the molecular programming of the fate choices and function of B cells in the periphery. They also note unanswered questions that pertain to differences among subsets of B lymphocytes and plasma cells.

Mature B lymphocytes are crucial components of adaptive immunity, a system essential for the evolutionary fitness of mammals. Adaptive lymphocyte function requires an initially naïve cell to proliferate extensively and its progeny to have the capacity to assume a variety of fates. These include either terminal differentiation (the long-lived plasma cell) or metastable transcriptional reprogramming (germinal center and memory B cells). In this review, we focus principally on the regulation of differentiation and functional diversification of the “B2” subset. An overview is combined with an account of more recent advances, including initial work on mechanisms that eliminate DNA methylation and potential links between intracellular metabolites and chromatin editing.

Ebi3 promotes T- and B-cell division and differentiation via STAT3

Although sharing the same subunit Ebi3, IL-27 (p28/Ebi3) and IL-35 (p35/Ebi3) have different biological functions, suggesting that Ebi3 subunit may functions as a carrier. Our data demonstrated that activated T cells and B cells effectively up-regulated Ebi3 expression. In addition, Ebi3 effectively promoted T-cell activation and the differentiation of helper T 1 (Th1), Th17, and Foxp3⁺ regulatory T (Treg) cells induced by Th1, Th17, and Treg polarizing condition, respectively. Naturally, Ebi3 could promote B-cell activation and the production of CD138⁺ plasma cells (PC) induced by LPS. Conversely, neutralizing anti-Ebi3 antibody could significantly suppress T/B-cell activation and production of Th1, Th17, Tregs, and PC induced by Th1, Th17, Treg polarizing condition, and LPS, respectively. Furthermore, we found that Ebi3 time-dependently induced STAT3 activation in CD4⁺T cells and B cells. Conversely, STAT3^-/- effectively reduced Ebi3 expression and the production of Th1, Th17, Tregs, and plasma cells. Finally, we showed that gp130 but not IL-27Rα mediates Ebi3-induced STAT3 activation. These results suggest that Ebi3 promotes Th- and B-cell differentiation via gp130-STAT3 signaling pathway. Thus, autocrine Ebi3 may play an important role in the differentiation of Th and B cells and thus in infection, inflammation, and autoimmune disorders.

Interleukin-27R Signaling Mediates Early Viral Containment and Impacts Innate and Adaptive Immunity after Chronic Lymphocytic Choriomeningitis Virus Infection

Chronic viral infections represent a major challenge to the host immune response, and a unique network of immunological elements, including cytokines, are required for their containment. By using a model persistent infection with the natural murine pathogen lymphocytic choriomeningitis virus clone 13 (LCMV Cl13) we investigated the role of one such cytokine, interleukin-27 (IL-27), in the control of chronic infection. We found that IL-27 receptor (IL-27R) signaling promoted control of LCMV Cl13 as early as days 1 and 5 after infection and that il27p28 transcripts were rapidly elevated in multiple subsets of dendritic cells (DCs) and myeloid cells. In particular, plasmacytoid DCs (pDCs), the most potent type 1 interferon (IFN-I)-producing cells, significantly increased il27p28 in a Toll-like receptor 7 (TLR7)-dependent fashion. Notably, mice deficient in an IL-27-specific receptor, WSX-1, exhibited a pleiotropy of innate and adaptive immune alterations after chronic lymphocytic choriomeningitis virus (LCMV) infection, including compromised NK cell cytotoxicity and antibody responses. While, the majority of these immune alterations appeared to be cell extrinsic, cell-intrinsic IL-27R was necessary to maintain early pDC numbers, which, alongside lower IFN-I transcription in CD11b⁺ DCs and myeloid cells, may explain the compromised IFN-I elevation that we observed early after LCMV Cl13 infection in IL-27R-deficient mice. Together, these data highlight the critical role of IL-27 in enabling optimal antiviral immunity early and late after infection with a systemic persistent virus and suggest that a previously unrecognized positive-feedback loop mediated by IL-27 in pDCs might be involved in this process.

IMPORTANCE Persistently replicating pathogens, such as human immunodeficiency virus, hepatitis B virus, and hepatitis C virus, represent major health problems worldwide. These infections impose a long-term challenge on the host immune system, which must be heavily and continuously regulated to keep pathogen replication in check without causing fatal immunopathology. Using a persistently replicating rodent pathogen, LCMV, in its natural host, we identified the cellular sources and effects of one important regulatory pathway, interleukin-27 receptor WSX-1 signaling, that is required for both very early and late restriction of chronic (but not acute) infection. We found that WSX-1 was necessary to promote innate immunity and the development of aberrant adaptive immune responses. This not only highlights the role of IL-27 receptor signaling in regulating distinct host responses that are known to be necessary to control chronic infections, but also positions IL-27 as a potential therapeutic target for their modulation.

Unexpected involvement of IL-13 signalling via a STAT6 independent mechanism during murine IgG2a development following viral vaccination

In this study, recombinant pox viral vaccination was shown to induce highly elevated IgG2a and low IgG1 antibody expression in mice lacking IL-4 or STAT6, whilst IL-13^-/- mice exhibited elevated IgG1, but very low IgG2a. These findings revealed that IL-13 and IL-4 differentially regulated antibody development. To understand this further, when STAT6^-/- mice were given a vaccine co-expressing IL-13Rα2 that temporarily sequestered IL-13, significantly reduced IgG2a expression, was detected. These findings for the first time demonstrated that IL-13 regulated IgG2a differentiation utilising an alternative IL-13R signalling pathway independent of STAT6 (IL-13Rα2 pathway). This was further corroborated by the (i) elevated IL-13Rα2 expression detected on STAT6^-/- lung MHCII⁺ CD11c⁺ cells 24 h post IL-13 inhibitor vaccination and ii) significant up-regulation of IL-13Rα2 expression on spleen and lung derived MHCII⁺ CD11c⁺ following inhibition of STAT6 signalling in vitro, or vaccination with IL-4R/STAT6 antagonist in vivo. When T follicular helper (Tfh) cells which regulate antibody differentiation were assessed post vaccination, although no difference in IL-4 expression was observed, greatly reduced IFN-γ expression was detected in IL-13^-/- and STAT6^-/- mice compared to wild-type. These findings support the notion that the balance of IL-13 level at the vaccination site can differentially regulate T and B-cell immune outcomes.

Interleukin-27 Exerts Its Antitumor Effects by Promoting Differentiation of Hematopoietic Stem Cells to M1 Macrophages

The interleukin IL27 promotes expansion and differentiation of hematopoietic stem cells into myeloid progenitor cells. Many tumor-infiltrating myeloid cells exert immunosuppressive effects, but we hypothesized that the myeloid cells induced by IL27 would have antitumor activity. In this study, we corroborated this hypothesis as investigated in two distinct mouse transplantable tumor models. Malignant mouse cells engineered to express IL27 exhibited reduced tumor growth in vivo Correlated with this effect was a significant increase in the number of tumor-infiltrating CD11b⁺ myeloid cells exhibiting a reduced immunosuppressive activity. Notably, these CD11b⁺ cells were characterized by an activated M1 macrophage phenotype, on the basis of increased expression of inducible nitric oxide synthase and other M1 biomarkers. In vivo depletion of these cells by administering anti-Gr-1 eradicated the antitumor effects of IL27. When admixed with parental tumors, CD11b⁺ cells inhibited tumor growth and directly killed the tumor in a nitric oxide-dependent manner. Mechanistically, IL27 expanded Lineage^-Sca-1⁺c-Kit⁺ cells in bone marrow. Transplant experiments in Ly5.1/5.2 congenic mice revealed that IL27 directly acted on these cells and promoted their differentiation into M1 macrophages, which mobilized into tumors. Overall, our results illustrated how IL27 exerts antitumor activity by enhancing the generation of myeloid progenitor cells that can differentiate into antitumorigenic M1 macrophages.Significance: These findings show how the interleukin IL27 exerts potent antitumor activity by enhancing the generation of myeloid progenitor cells that can differentiate into antitumorigenic M1 macrophages.Cancer Res; 78(1); 182-94. ©2017 AACR.

CD11c+ T-bet+ memory B cells: Immune maintenance during chronic infection and inflammation?

CD11c+ T-bet+ B cells have now been detected and characterized in different experimental and clinical settings, in both mice and humans. Whether such cells are monolithic, or define subsets of B cells with different functions is not yet known. Our studies have identified CD11c+ IgM+ CD19^hi splenic IgM memory B cells that appear at approximately three weeks post-ehrlichial infection, and persist indefinitely, during low-level chronic infection. Although the CD11c+ T-bet+ B cells we have described are distinct, they appear to share many features with similar cells detected under diverse conditions, including viral infections, aging, and autoimmunity. We propose that CD11c+ T-bet+ B cells as a group share characteristics of memory B cells that are maintained under conditions of inflammation and/or low-level chronic antigen stimulation. In some cases, these cells may be advantageous, by providing immunity to re-infection, but in others may be deleterious, by contributing to aged-associated autoimmune responses.

T-bet expressing B cells - Novel target for autoimmune therapies?

Autoimmune diseases affect more than 23.5million Americans. Traditional therapies for autoimmune diseases involve immunosuppressive drugs that globally dampen immune responses or target and kill large populations of normal immune cells. Both approaches lead to severe dysfunction of the immune system increasing the risk of infections and cancer. Therefore, a more targeted approach, modulating only the pathogenic autoimmune response, would be tremendously beneficial for autoimmune patients. However, only some novel targets involved in pathogenic autoimmune response have been discovered and it is likely that more remain, currently unknown. Here we review the data that have recently been described about T-bet+ B cells (also known as ABCs). Some data suggest that this B cell subset includes cells that are pathogenic in autoimmune responses. Therefore procedures that target these cells might be useful in autoimmune therapies.

Transcription Factor T-bet Orchestrates Lineage Development and Function in the Immune System

T-bet was originally described as the key transcription factor defining type 1 T helper (Th) cells. However, it is now clear that it drives the orchestrated generation of effector and memory cells in multiple different lymphocyte lineages. In addition to Th1 cells, CD8 T cells, B cells and some innate lymphocyte populations require T-bet for their development or differentiation in response to antigen. Furthermore, other Th cell populations, including T follicular helper and Th17, as well as regulatory T cells can co-opt T-bet expression to promote functional diversification and colocalization. Thus, T-bet broadly regulates transcriptional programs in response to type 1 inflammatory signals and mediates the coordinated differentiation, function, migration and survival of effector and memory lymphocyte subsets in the affected tissue. Therefore, T-bet expression is essential for effective clearance of pathogens and maintenance of immunity.

Dual Roles of IL-27 in Cancer Biology and Immunotherapy

IL-27 is a pleiotropic two-chain cytokine, composed of EBI3 and IL-27p28 subunits, which is structurally related to both IL-12 and IL-6 cytokine families. IL-27 acts through a heterodimer receptor consisting of IL-27Rα (WSX1) and gp130 chains, which mediate signaling predominantly through STAT1 and STAT3. IL-27 was initially reported as an immune-enhancing cytokine that supports CD4+ T cell proliferation, T helper (Th)1 cell differentiation, and IFN-γ production, acting in concert with IL-12. However, subsequent studies demonstrated that IL-27 displays complex immune-regulatory functions, which may result in either proinflammatory or anti-inflammatory effects in relationship to the biological context and experimental models considered. Several pieces of evidence, obtained in preclinical tumor models, indicated that IL-27 has a potent antitumor activity, related not only to the induction of tumor-specific Th1 and cytotoxic T lymphocyte (CTL) responses but also to direct inhibitory effects on tumor cell proliferation, survival, invasiveness, and angiogenic potential. Nonetheless, given its immune-regulatory functions, the effects of IL-27 on cancer may be dual and protumor effects may also occur. Here, we will summarize IL-27 biological activities and its functional overlaps with the IFNs and discuss its dual role in tumors in the light of potential applications to cancer immunotherapy.

Transcriptomic Study on Ovine Immune Responses to Fasciola hepatica Infection

BACKGROUND

Fasciola hepatica is not only responsible for major economic losses in livestock farming, but is also a major food-borne zoonotic agent, with 180 million people being at risk of infection worldwide. This parasite is sophisticated in manipulating the hosts' immune system to benefit its own survival. A better understanding of the mechanisms underpinning this immunomodulation is crucial for the development of control strategies such as vaccines.

METHODOLOGY/PRINCIPAL FINDINGS

This in vivo study investigated the global gene expression changes of ovine peripheral blood mononuclear cells (PBMC) response to both acute & chronic infection of F. hepatica, and revealed 6490 and 2364 differential expressed genes (DEGS), respectively. Several transcriptional regulators were predicted to be significantly inhibited (e.g. IL12 and IL18) or activated (e.g. miR155-5p) in PBMC during infection. Ingenuity Pathway Analysis highlighted a series of immune-associated pathways involved in the response to infection, including 'Transforming Growth Factor Beta (TGFβ) signaling', 'Production of Nitric Oxide in Macrophages', 'Toll-like Receptor (TLRs) Signaling', 'Death Receptor Signaling' and 'IL17 Signaling'. We hypothesize that activation of pathways relevant to fibrosis in ovine chronic infection, may differ from those seen in cattle. Potential mechanisms behind immunomodulation in F. hepatica infection are a discussed.

SIGNIFICANCE

In conclusion, the present study performed global transcriptomic analysis of ovine PBMC, the primary innate/adaptive immune cells, in response to infection with F. hepatica, using deep-sequencing (RNAseq). This dataset provides novel information pertinent to understanding of the pathological processes in fasciolosis, as well as a base from which to further refine development of vaccines.

IL-27 Directly Enhances Germinal Center B Cell Activity and Potentiates Lupus in Sanroque Mice

Germinal centers (GC) give rise to high-affinity and long-lived Abs and are critical in immunity and autoimmunity. IL-27 supports GCs by promoting survival and function of T follicular helper cells. We demonstrate that IL-27 also directly enhances GC B cell function. Exposure of naive human B cells to rIL-27 during in vitro activation enhanced their differentiation into CD20⁺CD38⁺CD27^lowCD95⁺CD10⁺ cells, consistent with the surface marker phenotype of GC B cells. This effect was inhibited by loss-of-function mutations in STAT1 but not STAT3 To extend these findings, we studied the in vivo effects of IL-27 signals to B cells in the GC-driven Roquin^san/san lupus mouse model. Il27ra^-/-Roquin^san/san mice exhibited significantly reduced GCs, IgG2a(c)⁺ autoantibodies, and nephritis. Mixed bone marrow chimeras confirmed that IL-27 acts through B cell- and CD4⁺ T cell-intrinsic mechanisms to support GCs and alter the production of pathogenic Ig isotypes. To our knowledge, our data provide the first evidence that IL-27 signals directly to B cells promote GCs and support the role of IL-27 in lupus.

Promotion of Expansion and Differentiation of Hematopoietic Stem Cells by Interleukin-27 into Myeloid Progenitors to Control Infection in Emergency Myelopoiesis

Emergency myelopoiesis is inflammation-induced hematopoiesis to replenish myeloid cells in the periphery, which is critical to control the infection with pathogens. Previously, pro-inflammatory cytokines such as interferon (IFN)-α and IFN-γ were demonstrated to play a critical role in the expansion of hematopoietic stem cells (HSCs) and myeloid progenitors, leading to production of mature myeloid cells, although their inhibitory effects on hematopoiesis were also reported. Therefore, the molecular mechanism of emergency myelopoiesis during infection remains incompletely understood. Here, we clarify that one of the interleukin (IL)-6/IL-12 family cytokines, IL-27, plays an important role in the emergency myelopoiesis. Among various types of hematopoietic cells in bone marrow, IL-27 predominantly and continuously promoted the expansion of only Lineage⁻Sca-1⁺c-Kit⁺ (LSK) cells, especially long-term repopulating HSCs and myeloid-restricted progenitor cells with long-term repopulating activity, and the differentiation into myeloid progenitors in synergy with stem cell factor. These progenitors expressed myeloid transcription factors such as Spi1, Gfi1, and Cebpa/b through activation of signal transducer and activator of transcription 1 and 3, and had enhanced potential to differentiate into migratory dendritic cells (DCs), neutrophils, and mast cells, and less so into macrophages, and basophils, but not into plasmacytoid DCs, conventional DCs, T cells, and B cells. Among various cytokines, IL-27 in synergy with the stem cell factor had the strongest ability to augment the expansion of LSK cells and their differentiation into myeloid progenitors retaining the LSK phenotype over a long period of time. The experiments using mice deficient for one of IL-27 receptor subunits, WSX-1, and IFN-γ revealed that the blood stage of malaria infection enhanced IL-27 expression through IFN-γ production, and the IL-27 then promoted the expansion of LSK cells, differentiating and mobilizing them into spleen, resulting in enhanced production of neutrophils to control the infection. Thus, IL-27 is one of the limited unique cytokines directly acting on HSCs to promote differentiation into myeloid progenitors during emergency myelopoiesis.

Emergency myelopoiesis is inflammation-induced hematopoiesis that is critical for controlling infection with pathogens, but the molecular mechanism remains incompletely understood. Here, we clarify that one of the interleukin (IL)-6/IL-12 family cytokines, IL-27, plays an important role in emergency myelopoiesis. Among various types of hematopoietic cells in bone marrow, IL-27 predominantly and continuously promoted expansion of only Lineage⁻Sca-1⁺c-Kit⁺ (LSK) cells, especially long-term repopulating hematopoietic stem cells, and differentiation into myeloid progenitors in synergy with stem cell factor. These progenitors expressed myeloid transcription factors such as Spi1, Gfi1, and Cebpa/b through activation of signal transducer and activator of transcription 1 and 3, and had enhanced potential to differentiate into neutrophils, but not into plasmacytoid dendritic cells. Among various cytokines, IL-27 in synergy with stem cell factor had the strongest ability to augment the expansion of LSK cells and their differentiation into myeloid progenitors. The blood stage of malaria infection was revealed to enhance IL-27 expression through interferon-γ production, and IL-27 then promoted the expansion of LSK cells, differentiating and mobilizing them into the spleen, resulting in enhanced production of neutrophils to control the infection. Thus, IL-27 is one of the limited unique cytokines directly acting on hematopoietic stem cells to promote differentiation into myeloid progenitors during emergency myelopoiesis.

Administration of DNA Encoding the Interleukin-27 Gene Augments Antitumour Responses through Non-adaptive Immunity

DNA-mediated immunization of a tumour antigen is a possible immunotherapy for cancer, and interleukin (IL)-27 has diverse functions in adaptive immunity. In this study, we examined whether IL-27 DNA administration enhanced antitumour effects in mice vaccinated with DNA encoding a putative tumour antigen, β-galactosidase (β-gal). An intramuscular injection of cardiotoxin before DNA administration facilitated the exogenous gene expression. In mice received β-gal and IL-27 DNA, growth of β-gal-positive P815 tumours was retarded and survival of the mice was prolonged. Development of β-gal-positive Colon 26 tumours was suppressed by vaccination of β-gal DNA and further inhibited by additional IL-27 DNA administration or IL-12 family cytokines. Nevertheless, a population of β-gal-specific CD8(+) T cells did not increase, and production of anti-β-gal antibody was not enhanced by IL-27 DNA administration. Spleen cells from mice bearing IL-27-expressing Colon 26 tumours showed greater YAC-1-targeted cytotoxicity although CD3(-)/DX5(+) natural killer (NK) cell numbers remained unchanged. Recombinant IL-27 enhanced YAC-1-targeted cytotoxicity of IL-2-primed splenic NK cells and augmented a phosphorylation of signal transducer and activator of transcription 3 and an expression of perforin. These data collectively indicate that IL-27 DNA administration activates NK cells and augments vaccination effects of DNA encoding a tumour antigen through non-adaptive immune responses.

IL-27-induced modulation of autoimmunity and its therapeutic potential

Interleukin-27 (IL-27) is a new member of the IL-12 family. It is produced by activated antigen-presenting cells and plays an important role in the regulation of CD4+ T cell differentiation and immune response. IL-27 activates multiple signaling cascades, including the JAK-STAT and p38 MAPK pathways. Several studies have revealed that IL-27 promotes the differentiation of Th1 and Tr1, but inhibits Th2, Th17, and Treg cells. However, a few studies have shown an opposite effect on certain T cell subsets, such as Treg. IL-27 displays both pro- and anti- inflammatory activities in different autoimmune diseases. Here, we have discussed the role of IL-27 in rheumatoid arthritis, multiple sclerosis, colitis, lupus, psoriasis, type 1 diabetes, and uveitis. Most of this information is derived from experimental models of these autoimmune diseases. The mechanistic basis of the dual role of IL-27 in inflammation and autoimmunity is still not fully defined. In general, the pro-/anti-inflammatory activity of IL-27 is influenced by the underlying immune effector pathways, the phase of the disease, the presence or absence of counter-regulatory cytokines/T cell subsets, and the tissue/cell type under study. Despite a spectrum of outcomes in various autoimmune diseases, mostly anti-inflammatory and immunomodulatory effects of IL-27 have been observed in this category of diseases. Accordingly, IL-27 represents a novel, promising target/agent for the treatment of autoimmune diseases.

Protective antibody and cytokine responses in mice following immunization with recombinant beta-tubulin and subsequent Trypanosoma evansi challenge

Background

Trypanosomosis or Surra, caused by the flagellated hemoprotozoan parasite Trypanosoma evansi, is a disease of economic importance through its wide prevalence in domestic livestock in tropical countries. In the absence of a protective vaccine, management of the disease relies on a few available chemotherapeutic agents. Although humoral immunity is the mainstay of resistance to T. evansi, the ability of the parasite to vary its immunodominant surface proteins to subvert the immune system has forced vaccine efforts to target a variety of invariant epitopes. Beta tubulin, an integral component of the trypanosome cytoskeleton, was therefore targeted using the recombinant form of the protein for immunization.

Methods

The 1329 bp coding sequence of beta tubulin gene was PCR amplified and cloned in pQE-TriSystem expression vector. Recombinant beta tubulin was heterologously expressed in Escherichia coli as a 46 KDa fusion protein and used for immunization of mice. The Ig response was studied by ELISA, whereas the cytokine response was measured using a cytometric bead-based assay quantified by flow cytometry.

Result

Immunization with recombinant beta (β)-tubulin protein induced a beta-tubulin specific humoral immune response of predominantly IgG2a isotype. Lethal challenge with T. evansi blood-form trypomastigotes post-immunization elicited a robust anamnestic response. An abundance of IFN-γ further confirmed the Th-1 bias of the protective response. We also observed extended survival and better control of the challenge infection in the immunized mice.

Conclusions

A robust anamnestic response following challenge including a Th-1 serum cytokine profile coupled with increased survival is indicative of protective immunity in the immunized mice. These observations suggest that β-tubulin of T. evansi is a viable antigenic target for development of a vaccine against this important livestock pathogen.

T-bet Is Required for the Rapid Clearance of Attenuated Rabies Virus from Central Nervous System Tissue

Much of our understanding of CNS immunity has been gained from models involving pathological inflammation. Attenuated rabies viruses (RABV) are unique tools to study CNS immunity in the absence of conventional inflammatory mechanisms, as they spread from the site of inoculation to the CNS transaxonally, thereby bypassing the blood-brain barrier (BBB), and are cleared without neutrophil or monocyte infiltration. To better understand the role of CD4 T cell subsets in the clearance of the virus from CNS tissues, we examined the development of antiviral immunity in wild-type (WT) and T-bet knockout mice (T-bet(-/-)), which lack Th1 cells. Early control of RABV replication in the CNS tissues of WT mice is associated with the production of IFN-γ, with antiviral effects likely mediated through the enhanced expression of type I IFNs. Of interest, IFN-α and -γ are overexpressed in the infected T-bet(-/-) by comparison with WT CNS tissues, and the initial control of RABV infection is similar. Ultimately, attenuated RABV are cleared from the CNS tissues of WT mice by Ab locally produced by the activities of infiltrating T and B cells. Although T and B cell infiltration into the CNS of infected T-bet(-/-) mice is comparable, their activities are not, the consequence being delayed, low-level Ab production and prolonged RABV replication. More importantly, neither T-bet(-/-) mice immunized with an attenuated virus, nor WT mice with Th2 RABV-specific immunity induced by immunization with inactivated virus, are protected in the long term against challenge with a pathogenic RABV.

Antibody-independent functions of B cells: a focus on cytokines

Cytokine production by B cells is important for multiple aspects of immunity. B cell-derived cytokines, including lymphotoxin, are essential for the ontogenesis, homeostasis and activation of secondary lymphoid organs, as well as for the development of tertiary lymphoid tissues at ectopic sites. Other B cell-derived cytokines, such as interleukin-6 (IL-6), interferon-γ and tumour necrosis factor, influence the development of effector and memory CD4(+) T cell responses. Finally, B cells can regulate inflammatory immune responses, primarily through their provision of IL-10 and IL-35. This Review summarizes these various roles of cytokine-producing B cells in immunity and discusses the rational for targeting these cells in the clinic.

Bone marrow-derived clonal mesenchymal stem cells inhibit ovalbumin-induced atopic dermatitis

Mesenchymal stem cells (MSCs) possess immunomodulatory activities, including suppression of T- and B-cell activation. However, their effects on atopic dermatitis (AD) have not yet been studied. Using an ovalbumin-induced AD mouse model, we investigated whether MSCs can be used as therapeutics in AD. We isolated both allogeneic and syngeneic clonal MSCs (cMSCs) from mouse bone marrow according to the subfractionation culturing method. Our cMSCs suppressed both T- and B-cell activation. T-cell proliferation and cytokine production, including interferon (IFN)-γ and interleukin (IL)-4, were suppressed by inhibition of transcription factors, such as T-bet, GATA-3, and c-Maf. Those transcription factors were nitric oxide dependent. Immunoglobulin E (IgE) suppression occurred through downregulation of AID and BLIMP-1, important regulators for isotype class switch and B-cell differentiation. The cMSCs were injected intravenously into ovalbumin-induced AD mouse model, and the therapeutic effects were analyzed. Injection of both allogeneic and syngeneic cMSCs in an AD mouse model inhibited cell infiltration in skin lesions and decreased the serum level of IgE. IL-4 expression was also suppressed by cMSCs in both the lymph node and skin. The cMSCs migrated to skin lesions and draining lymph nodes. Taken together, these data demonstrated that cMSCs, which suppressed T- and B-cell functions, can be used for the treatment of AD in mice.

Gene expression profiling of the response to interferon beta in Epstein-Barr-transformed and primary B cells of patients with multiple sclerosis

The effects of interferon-beta (IFN-β), one of the key immunotherapies used in multiple sclerosis (MS), on peripheral blood leukocytes and T cells have been extensively studied. B cells are a less abundant leukocyte type, and accordingly less is known about the B cell-specific response to IFN-β. To identify gene expression changes and pathways induced by IFN-β in B cells, we studied the in vitro response of human Epstein Barr-transformed B cells (lymphoblast cell lines-LCLs), and validated our results in primary B cells. LCLs were derived from an MS patient repository. Whole genome expression analysis identified 115 genes that were more than two-fold differentially up-regulated following IFN-β exposure, with over 50 previously unrecognized as IFN-β response genes. Pathways analysis demonstrated that IFN-β affected LCLs in a similar manner to other cell types by activating known IFN-β canonical pathways. Additionally, IFN-β increased the expression of innate immune response genes, while down-regulating many B cell receptor pathway genes and genes involved in adaptive immune responses. Novel response genes identified herein, NEXN, DDX60L, IGFBP4, and HAPLN3, B cell receptor pathway genes, CD79B and SYK, and lymphocyte activation genes, LAG3 and IL27RA, were validated as IFN-β response genes in primary B cells. In this study new IFN-β response genes were identified in B cells, with possible implications to B cell-specific functions. The study's results emphasize the applicability of LCLs for studies of human B cell drug response. The usage of LCLs from patient-based repositories may facilitate future studies of drug response in MS and other immune-mediated disorders with a B cell component.

IL-27p28 is essential for parent-to-F1 acute graft-versus-host disease

Acute graft versus host disease (aGVHD) remains a life-threatening complication of bone marrow transplantation. Here we show that IL-27, a member of the IL-12 cytokine family, plays an essential role in a parent-to-F1 murine aGVHD model, using B6 mice as parents and B6D2 mice as F1 recipients. IL-27 is transiently detectable in the serum of B6D2 recipients of B6 spleen cells, with a peak at day 10. Treatment with anti-IL-27p28 mAb MM27.7B1 (αp28Ab), at the time of and six days after B6 cell transfer, blocked GVHD. Protection was associated with host cell survival and undiminished engraftment of donor cells, lack of host B-cell depletion, increased Th2-type immunoglobulin production, a decrease in serum IFN-γ, a drop in anti-H-2D(d) cytotoxic T lymphocyte activity and an increase in Foxp3(+) T cells. We therefore conclude that IL-27 plays a critical role in the parent-to-F1 model of aGVHD and that blocking IL-27 could have therapeutic relevance.

T-bet: a bridge between innate and adaptive immunity

Originally described over a decade ago as a T cell transcription factor regulating T helper 1 cell lineage commitment, T-bet is now recognized as having an important role in many cells of the adaptive and innate immune system. T-bet has a fundamental role in coordinating type 1 immune responses by controlling a network of genetic programmes that regulate the development of certain immune cells and the effector functions of others. Many of these transcriptional networks are conserved across innate and adaptive immune cells and these shared mechanisms highlight the biological functions that are regulated by T-bet.

Cell-intrinsic IL-27 and gp130 cytokine receptor signaling regulates virus-specific CD4⁺ T cell responses and viral control during chronic infection

The outcome of chronic viral infections, which affect millions of people worldwide, is greatly dependent on CD4⁺ T cells. Here we showed that T cell-specific ablation of the common interleukin-6 (IL-6) family receptor, gp130, profoundly compromised virus-specific CD4⁺ T cell survival, T follicular helper responses, and IL-21 production at late stages of chronic lymphocytic choriomeningitis virus (LCMV) infection. These effects were cell intrinsic for CD4⁺ T cells and were accompanied by a reduction of CD8⁺ T cells, antibodies, and a severe failure in viral control. We identified IL-27 as a gp130 cytokine that promoted antiviral CD4⁺ T cell accumulation in vivo and that rapidly induced IL-21 ex vivo. Furthermore, IL-27R was critical for control of persistent LCMV in vivo. These results reveal that gp130 cytokines (particularly IL-27) are key regulators of CD4⁺ T cell responses during an established chronic viral infection, empowering both humoral and cytotoxic immunity.