Inflammatory and anti-inflammatory cytokines play an important role in the generation of effector and memory CD8+ T cells. We used two different models, transgenic expression of truncated (dominant negative) form of TGF-β receptor II (dnTGFβRII) and Cre-mediated deletion of the floxed TGFβRII to examine the role of TGF-β signaling in the formation, function, and homeostatic proliferation of memory CD8+ T cells. Blocking TGF-β signaling in effector CD8+ T cells using both of these models demonstrated a role for TGF-β in regulating the number of short-lived effector cells, but did not alter memory CD8+ T cell formation and their function upon Listeria monocytogenes infection in mice. Interestingly however, a massive lymphoproliferative disorder and cellular transformation were observed in antigen-experienced and homeostatically generated memory CD8+ T cells only in cells that express the dnTGFβRII, but not in cells with a complete deletion of TGFβRII. Furthermore, the development of transformed memory CD8+ T cells expressing dnTGFβRII was IL-7- and IL-15-independent, and MHC class I was not required for their proliferation. We show that transgenic expression of the dnTGFβRII, rather than the absence of TGFβRII-mediated signaling, is responsible for dysregulated expansion of memory CD8+ T cells. This study uncovers a previously unrecognized dominant function of the dnTGFβRII in CD8+ T cell proliferation and cellular transformation, which is caused by a mechanism that is different than the absence of TGF-β signaling. These results should be considered during both basic and translational studies where there is a desire to block TGF-β signaling in CD8+ T cells.
Regulation of metabolic pathways in the immune system provides a mechanism to actively control cellular function, growth, proliferation and survival. Here, we report that miR-181 is a non-redundant determinant of cellular metabolism and is essential to support the biosynthetic demands of early NKT cell development. As a result, miR-181-deficient mice showed a complete absence of mature NKT cells in the thymus and periphery. Mechanistically, miR-181 modulated expression of the phosphatase PTEN to control PI3K signaling, which was a primary stimulus for anabolic metabolism in immune cells. Thus miR-181-deficient mice also showed severe defects in lymphoid development and T cell homeostasis associated with impaired PI3K signaling. These results uncover miR-181 as essential for NKT cell development, and establish this family of miRNAs as central regulators of PI3K signaling and global metabolic fitness during development and homeostasis.
miR-181; PTEN; Natural killer T cells; Metabolism; PI3K
The cJun NH2-terminal kinase (JNK) signaling pathway contributes to inflammation and plays a key role in the metabolic response to obesity, including insulin resistance. Macrophages are implicated in this process. To test the role of JNK, we established mice with selective JNK-deficiency in macrophages. We report that feeding a high fat diet to control and JNK-deficient mice caused similar obesity, but only mice with JNK-deficient macrophages remained insulin sensitive. The protection of mice with macrophage-specific JNK-deficiency against insulin resistance was associated with reduced tissue infiltration by macrophages. Immunophenotyping demonstrated that JNK was required for pro-inflammatory macrophage polarization. These studies demonstrate that JNK in macrophages is required for the establishment of obesity-induced insulin resistance and inflammation.
Interleukin-22 (IL-22) is a good candidate to play a critical role in regulating gut microbiota because it is an important inducer of antimicrobial peptides and mucins in the gut. However, whether IL-22 participates into immune homeostasis by way of modulating gut microbiota remains to be elucidated. In this study, we find through 16S rRNA gene pyrosequencing analysis that healthy IL-22 deficient mice had altered colonic microbiota, notably with decreased abundance of some genera including Lactobacillus and increased levels of others. Mice harboring this altered microbiota exhibited more severe disease during experimentally-induced colitis. Interestingly, this altered gut microbiota can be transmitted to co-housed wild-type animals along with the increased susceptibility to this colitis, indicating an important role of IL-22 in shaping the homeostatic balance between immunity and colonic microbiota for host health.
Chronic viral infections lead to CD8+ T cell exhaustion, characterized by impaired cytokine secretion. Presence of the immune-regulatory cytokine IL-10 promotes chronicity of Lymphocytic Choriomeningitis Virus (LCMV) Clone 13 infection, while absence of IL-10/IL-10R signaling early during infection results in viral clearance and higher percentages and numbers of antiviral, cytokine producing T cells. IL-10 is produced by several cell types during LCMV infection but it is currently unclear which cellular sources are responsible for induction of viral chronicity. Here, we demonstrate that although dendritic cells produce IL-10 and overall IL-10 mRNA levels decrease significantly in absence of CD11c+ cells, absence of IL-10 produced by CD11c+ cells failed to improve the LCMV-specific T cell response and control of LCMV infection. Similarly, NK cell specific IL-10 deficiency had no positive impact on the LCMV-specific T cell response or viral control, even though high percentages of NK cells produced IL-10 at early time points after infection. Interestingly, we found markedly improved T cell responses and clearance of normally chronic LCMV Clone 13 infection when either myeloid cells or T cells lacked IL-10 production and mice depleted of monocytes/macrophages or CD4+ T cells exhibited reduced overall levels of IL-10 mRNA. These data suggest that the decision whether LCMV infection becomes chronic or can be cleared critically depends on early CD4+ T cell and monocyte/macrophage produced IL-10.
Chronic viral infections like Hepatitis B and C Virus (HBV and HCV) and Human Immunodeficiency Virus (HIV) in humans affect more than 500 million people worldwide. While a robust T cell response is a hallmark of many acute infections one hurdle inhibiting the clearance of chronic viral infections is that the immune-suppressive cytokine IL-10 modulates the virus-host balance towards induction of T cell dysfunction. IL-10 is produced by several cell types during chronic Lymphocytic Choriomeningitis Virus (LCMV) infection but it is currently unclear which cellular sources are responsible to promote viral chronicity. Here, we demonstrate that T cell responses improved markedly, and that normally chronic LCMV Clone 13 infection could be cleared when either myeloid cells or T cells lacked IL-10 production. Furthermore, mice depleted of monocytes/macrophages or CD4+ T cells exhibited reduced overall levels of IL-10 mRNA. These data suggest that the decision whether LCMV infection becomes chronic or can be cleared critically depends on CD4+ T cell and monocyte/macrophage produced IL-10 early during the establishment of viral chronicity.
The gram-negative obligate intracellular bacterium Anaplasma phagocytophilum is the causative agent of human granulocytic anaplasmosis (HGA), an emerging tick-borne infectious disease occuring worldwide. HGA is generally self-limiting, however, the underlying mechanisms, particularly the innate immune pathways that mediate the immune clearance of A. phagocytophilum, are less understood. We herein report an unexpected role for Receptor interacting protein-2 (Rip2), the adaptor protein for the Nod-Like Receptors (NLRs), Nod1/Nod2, in the host immune response against A. phagocytophilum infection. Although A. phagocytophilum genome is reported to lack the genes encoding the known ligands of Nod1 and Nod2, its infection up-regulated the transcription of Rip2 in human primary neutrophils. Our results revealed that Rip2 deficient mice had significantly higher bacterial load than wild type controls throughout the infection period. In addition, the Rip2 deficient mice took strikingly longer duration to clear A. phagocytophilum infection. Detailed analysis identified that interferon gamma (IFNγ) and interleukin -18 (IL-18) but not interleukin -12 (IL-12), macrophage inflammatory protein-2 (MIP-2), and KC response were diminished in A. phagocytophilum-challenged Rip2 deficient mice. Together, these results revealed that Rip2 play important roles in the immune control of A. phagocytophilum, and may contribute to our understanding of the host response to Rickettsiales.
Rip2; Anaplasma phagocytophilum; NLR; IFNγ
Skin wound repair requires complex and highly coordinated interactions between keratinocytes, fibroblasts and immune cells to restore the epidermal barrier and tissue architecture after acute injury. The cytokine interleukin-22 (IL-22) mediates unidirectional signaling from immune cells to epithelial cells during injury of peripheral tissues such as the liver and colon, where IL-22 causes epithelial cells to produce anti-bacterial proteins, express mucins, and enhance epithelial regeneration. In this study, we use IL-22−/− mice to investigate the in vivo role for IL-22 in acute skin wounding. We find that IL-22−/− mice display major defects in the skin’s dermal compartment after full thickness wounding. We find that IL-22 signaling is active in fibroblasts using in vitro assays with primary fibroblasts and that IL-22 directs extracellular matrix (ECM) gene expression as well as myofibroblast differentiation both in vitro and in vivo. These data define roles of IL-22 beyond epithelial crosstalk, and suggest that IL-22 plays a previously unidentified role in skin repair by mediating interactions between immune cells and fibroblasts.
Interleukin 22; Wound Healing; Fibroblasts; extracellular matrix
Inflammasome activation is important for the development of an effective host defense against many pathogens, including RNA viruses. However, the mechanism by which the inflammasome recognizes RNA viruses and its role in rabies virus (RABV) pathogenicity and immunogenicity remain poorly defined. To determine the function of the inflammasome in response to RABV infection, we infected murine bone marrow-derived dendritic cells (BMDCs) with RABV. Our results indicate that the infection of BMDCs with RABV induces both the production of pro-interleukin-1β (pro-IL-1β) and its processing, resulting in the secretion of active IL-1β through activation of the NLRP3-, ASC-, and caspase-1-dependent inflammasome. As previously shown for the induction of type I interferon by RABV, the induction of pro-IL-1β also depends upon IPS-1. We demonstrate that both the production of pro-IL-1β and activation of the inflammasome require viral replication. We also demonstrate that increased viral replication in BMDCs derived from IFNAR-deficient mice resulted in significantly more IL-1β release. Additionally, IL-1 receptor-deficient mice show an increase in RABV pathogenicity. Taken together, these results indicate an important role of the inflammasome in innate immune recognition of RABV.
We previously demonstrated that γδ T cells played an important role in tumor immune surveillance by providing an early source of IFN-γ. The precise role of different subsets of γδ T cells in the antitumor immune response, however, is unknown. Vγ1 and Vγ4 γδ T cells are the principal subsets of peripheral lymphoid γδ T cells and they might play distinct roles in tumor immunity. In support of this, we observed that reconstitution of TCRδ−/− mice with Vγ4, but not Vγ1, γδ T cells restored the antitumor response. We also found that these effects were exerted by the activated (CD44high) portion of Vγ4 γδ T cells. We further determined that IFN-γ and perforin are critical elements in the Vγ4-mediated antitumor immune response. Indeed, CD44high Vγ4 γδ T cells produced significantly more IFN-γ and perforin on activation, and showed greater cytolytic activity than did CD44high Vγ1 γδ T cells, apparently due to the high level of eomesodermin (Eomes) in these activated Vγ4 γδ T cells. Consistently, transfection of dominant-negative Eomes in Vγ4 γδ T cells diminished the level of IFN-γ secretion, indicating a critical role of Eomes in the effector function of these γδ T cells. Our results thus reveal distinct functions of Vγ4 and Vγ1 γδ T cells in antitumor immune response, and identify a protective role of activated Vγ4 γδ T cells, with possible implications for tumor immune therapy.
TLR3 is known to respond to dsRNA from viruses, apoptotic cells, and/or necrotic cells. Dying cells are a rich source of ligands that can activate TLRs, such as TLR3. TLR3 expressed in the liver is likely to be a mediator of innate activation and inflammation in the liver. The importance of this function of TLR3 during acute hepatitis has not previously been fully explored. We used the mouse model of Con A-induced hepatitis and observed a novel role for TLR3 in hepatocyte damage in the absence of an exogenous viral stimulus. Interestingly, TLR3 expression in liver mononuclear cells and sinus endothelial cells was up-regulated after Con A injection and TLR3−/− mice were protected from Con A-induced hepatitis. Moreover, splenocytes from TLR3−/− mice proliferated less to Con A stimulation in the presence of RNA derived from damaged liver tissue compared with wild-type (WT) mice. To determine the relative contribution of TLR3 expression by hematopoietic cells or nonhematopoietic to liver damage during Con A-induced hepatitis, we generated bone marrow chimeric mice. TLR3−/− mice engrafted with WT hematopoietic cells were protected in a similar manner to WT mice reconstituted with TLR3−/− bone marrow, indicating that TLR3 signaling in both nonhematopoietic and hematopoietic cells plays an important role in mediating liver damage. In summary, our data suggest that TLR3 signaling is necessary for Con A-induced liver damage in vivo and that TLR3 regulates inflammation and the adaptive T cell immune response in the absence of viral infection.
The current model of apoptosis holds that upstream signals lead to activation of downstream effector caspases. We generated mice deficient in the two effectors, caspase 3 and caspase 7, which died immediately after birth with defects in cardiac development. Fibroblasts lacking both enzymes were highly resistant to both mitochondrial and death receptor–mediated apoptosis, displayed preservation of mitochondrial membrane potential, and had defective nuclear translocation of apoptosis-inducing factor (AIF). Furthermore, the early apoptotic events of Bax translocation and cytochrome c release were also delayed. We conclude that caspases 3 and 7 are critical mediators of mitochondrial events of apoptosis.
Inflammasomes are multi-protein intracellular signaling complexes that have recently been hypothesized to play a role in the regulation of the inflammation response. We studied associations between inflammasome-associated cytokines IL-1β and IL-18 in cerebrospinal fluid (CSF) of patients with bacterial meningitis and clinical outcome, and pneumococcal serotype. In a murine model of pneumococcal meningitis we examined the pathophysiological roles of two inflammasome proteins, NLRP3 (Nod-like receptor protein-3) and adaptor protein ASC (apoptosis-associated speck-like protein).
In a nationwide prospective cohort study, CSF cytokine levels were measured and related to clinical outcome and pneumococcal serotype. In a murine model of pneumococcal meningitis using Streptococcus pneumoniae serotype 3, we examined bacterial titers, cytokine profiles and brain histology at 6 and 30 hours after inoculation in wild-type (WT), Asc and Nlrp3 deficient mice.
In patients with bacterial meningitis, CSF levels of inflammasome associated cytokines IL-1β and IL-18 were related to complications, and unfavorable disease outcome. CSF levels of IL-1β were associated with pneumococcal serotype (p<0.001). In our animal model, Asc and Nlrp3 deficient mice had decreased systemic inflammatory responses and bacterial outgrowth as compared to WT mice. Differences between Asc−/− and WT mice appeared sooner after bacterial inoculation and were more widespread (lower pro-inflammatory cytokine levels in both blood and brain homogenate) than in Nlrp3-/-mice. Nlrp3 deficiency was associated with an increase of cerebral neutrophil infiltration and cerebral hemorrhages when compared to WT controls.
Our results implicate an important role for inflammasome proteins NLRP3 and ASC in the regulation of the systemic inflammatory response and the development of cerebral damage during pneumococcal meningitis, which may dependent on the pneumococcal serotype.
Host antibacterial responses include mechanisms that kill bacteria, but also those that protect or tolerize the host to potentially damaging antibacterial effects. We determined that Chitinase 3-like-1 (Chi3l1), a conserved prototypic chitinase-like protein, is induced by Streptococcus pneumoniae and plays central roles in promoting bacterial clearance and mediating host tolerance. S. pneumoniae-infected Chi3l1 null mice exhibit exaggerated lung injury, inflammation and hemorrhage, more frequent bacterial dissemination, decreased bacterial clearance, and enhanced mortality compared to controls. Chi3l1 augments macrophage bacterial killing by inhibiting caspase-1-dependent macrophage pyroptosis and augments host tolerance by controlling inflammasome activation, ATP accumulation, expression of ATP receptor P2×7R, and production of thymic stromal lymphopoietin and type 1, type 2, and type 17 cytokines. These data demonstrate that Chi3l1 is induced during infection, where it promotes bacterial clearance while simultaneously augmenting host tolerance, and that these roles likely contributed to the retention of Chi3l1 over species and evolutionary time.
Mechanical ventilation using high oxygen tensions is often necessary to treat patients with respiratory failure. Recently, TLRs were identified as regulators of noninfectious oxidative lung injury. IRAK-M is an inhibitor of MyD88-dependent TLR signaling. Exposure of mice deficient in IRAK-M (IRAK-M−/−) to 95% oxygen resulted in reduced mortality compared with wild-type mice and occurred in association with decreased alveolar permeability and cell death. Using a bone marrow chimera model, we determined that IRAK-M’s effects were mediated by structural cells rather than bone marrow-derived cells. We confirmed the expression of IRAK-M in alveolar epithelial cells (AECs) and showed that hyperoxia can induce the expression of this protein. In addition, IRAK-M−/− AECs exposed to hyperoxia experienced a decrease in cell death. IRAK-M may potentiate hyperoxic injury by suppression of key antioxidant pathways, because lungs and AECs isolated from IRAK-M−/− mice have increased expression/activity of heme oxygenase-1, a phase II antioxidant, and NF (erythroid-derived)-related factor-2, a transcription factor that initiates antioxidant generation. Treatment of IRAK-M−/− mice in vivo and IRAK-M−/− AECs in vitro with the heme oxygenase-1 inhibitor, tin protoporphyrin, substantially decreased survival and significantly reduced the number of live cells after hyperoxia exposure. Collectively, our data suggest that IRAK-M inhibits the induction of antioxidants essential for protecting the lungs against cell death, resulting in enhanced susceptibility to hyperoxic lung injury.
TGFβ1 is a regulatory cytokine that has an important role in controlling T cell differentiation. T cell-produced TGFβ1 acts on T cells to promote Th17 cell differentiation and the development of experimental autoimmune encephalomyelitis (EAE). However, the exact TGFβ1-producing T cell subset required for Th17 cell generation and its cellular mechanism of action remain unknown. Here we showed that deletion of the Tgfb1 gene from activated T cells and Treg cells, but not Treg cells alone, abrogated Th17 cell differentiation resulting in almost complete protection from EAE. Furthermore, differentiation of T cells both in vitro and in vivo demonstrated that TGFβ1 was highly expressed by Th17 cells and acted in a predominantly autocrine manner to maintain Th17 cells in vivo. These findings reveal an essential role for activated T cell-produced TGFβ1 in promoting the differentiation of Th17 cells and controlling inflammatory diseases.
TLR7 is an innate signaling receptor that recognizes single-stranded viral RNA and is activated by viruses that cause persistent infections. We show that TLR7 signaling dictates either clearance or establishment of life-long chronic infection by lymphocytic choriomeningitis virus (LCMV) Cl 13 but does not affect clearance of the acute LCMV Armstrong 53b strain. TLR7−/− mice infected with LCMV Cl 13 remained viremic throughout life from defects in the adaptive anti-viral immune response, notably diminished T cell function, exacerbated T cell exhaustion, decreased plasma cell maturation, and negligible anti-viral antibody production. Adoptive transfer of TLR7+/+ LCMV immune memory cells that enhance clearance of persistent LCMV Cl 13 infection in TLR7+/+ mice fail to purge LCMV Cl 13 infection in TLR7−/− mice, demonstrating that a TLR7-deficient environment renders anti-viral responses ineffective. Therefore, methods that promote TLR7 signaling are promising treatment strategies for chronic viral infections.
The antiviral response is largely mediated by dendritic cells (DC), including conventional (c) DCs that function as antigen presenting cells and plasmacytoid (p) DCs that produce Type I interferons, making them an attractive target for viruses. We find that the Old-world arenaviruses lymphocytic choriomeningitis virus clone 13 (LCMV Cl13) and Lassa virus bind pDCs to a greater extent than cDCs. Consistently, LCMV Cl13 targets pDCs early after in vivo infection of its natural murine host and establishes a productive and robust replication cycle. pDCs co-produce type I interferons and pro-inflammatory cytokines, with the former being induced in both infected and uninfected pDCs, demonstrating a dissociation from intrinsic virus replication. TLR7 globally mediates pDC responses, limits pDC viral load and promotes rapid innate and adaptive immune cell activation. These early events likely help dictate the outcome of infections with arenaviruses and other DC-replicating viruses and shed light on potential therapeutic targets.
dendritic cell; plasmacytoid dendritic cells; type I interferon; interleukin-12; innate; toll like receptor-7; lymphocytic choriomeningitis virus (LCMV); Lassa Fever virus (LASV); arenavirus; chronic viral infection
A functional adaptive immune system depends on a diverse and self-tolerant population of T lymphocytes that are generated in the thymus and maintained in the peripheral lymphoid organs. Recent studies have defined the cytokine transforming growth factor-β (TGF-β) as a critical regulator of thymic T cell development as well as a crucial player in peripheral T cell homeostasis, tolerance to self antigens, and T cell differentiation during the immune response. The unique mechanism of TGF-β activation and the plasticity of TGF-β signaling create a stage for TGF-β to integrate signals from multiple cell types and environmental cues to regulate T cells.
Inflammasome activation is important for antimicrobial defense because it induces cell death and regulates the secretion of IL-1 family cytokines, which play a critical role in inflammatory responses. The inflammasome activates caspase-1 to process and secrete IL-1β. However, the mechanisms governing IL-1α release are less clear. Recently, a non-canonical inflammasome was described that activates caspase-11 and mediates pyroptosis and release of IL-1α and IL-1β. Caspase-11 activation in response to Gram-negative bacteria requires Toll-like receptor 4 (TLR4) and TIR-domain-containing adaptor-inducing interferon-β (TRIF)-dependent interferon production. Whether additional bacterial signals trigger caspase-11 activation is unknown. Many bacterial pathogens use specialized secretion systems to translocate effector proteins into the cytosol of host cells. These secretion systems can also deliver flagellin into the cytosol, which triggers caspase-1 activation and pyroptosis. However, even in the absence of flagellin, these secretion systems induce inflammasome activation and the release of IL-1α and IL-1β, but the inflammasome pathways that mediate this response are unclear. We observe rapid IL-1α and IL-1β release and cell death in response to the type IV or type III secretion systems of Legionella pneumophila and Yersinia pseudotuberculosis. Unlike IL-1β, IL-1α secretion does not require caspase-1. Instead, caspase-11 activation is required for both IL-1α secretion and cell death in response to the activity of these secretion systems. Interestingly, whereas caspase-11 promotes IL-1β release in response to the type IV secretion system through the NLRP3/ASC inflammasome, caspase-11-dependent release of IL-1α is independent of both the NAIP5/NLRC4 and NLRP3/ASC inflammasomes as well as TRIF and type I interferon signaling. Furthermore, we find both overlapping and non-redundant roles for IL-1α and IL-1β in mediating neutrophil recruitment and bacterial clearance in response to pulmonary infection by L. pneumophila. Our findings demonstrate that virulent, but not avirulent, bacteria trigger a rapid caspase-11-dependent innate immune response important for host defense.
The inflammasome, a multiprotein complex, is critical for host defense against bacterial infection. The inflammasome activates the host protease caspase-1 to process and secrete IL-1β. Another caspase, caspase-11, can cause cell death and IL-1α release. The bacterial signals that trigger caspase-11 activation are poorly understood. A common feature of many bacterial pathogens is the ability to inject virulence factors and other bacterial molecules into the host cell cytosol by means of a variety of virulence-associated secretion systems. These secretion systems can introduce bacterial flagellin into the host cytosol, which leads to caspase-1 activation and cell death. However, many bacteria lack or down-regulate flagellin yet still activate the inflammasome. Here, we show that the type IV secretion system of Legionella pneumophila and the type III secretion system of Yersinia pseudotuberculosis rapidly trigger caspase-11 activation in a flagellin-independent manner. Caspase-11 activation mediates two separate inflammasome pathways: one leading to IL-1β processing and secretion, and one leading to cell death and IL-1α release. Furthermore, we find these caspase-11-regulated cytokines are critical for neutrophil recruitment to the site of infection and clearance of non-flagellated Legionella in vivo. Overall, our findings show that virulent bacteria activate a rapid caspase-11-dependent immune response that plays a critical role in host defense.
Nucleotide-binding domain leucine-rich repeat containing receptors (NLRs) are cytosolic receptors that initiate immune responses to sterile and infectious insults to the host. Studies have demonstrated that Nlrp3 is critical for the control of Candida albicans infections and in the generation of anti-fungal Th17 responses. Here we show that the NLR family member Nlrp10 also plays a unique role in the control of disseminated C. albicans infection in vivo. Nlrp10-deficient mice had increased susceptibility to disseminated candidiasis as indicated by decreased survival and increased fungal burdens. In contrast to Nlrp3, Nlrp10-deficiency did not affect innate proinflammatory cytokine production from macrophages and dendritic cells challenged with C. albicans. However, Nlrp10-deficient mice displayed a profound defect in Candida-specific Th1 and Th17 responses. These results demonstrate a novel role for Nlrp10 in the generation of adaptive immune responses to fungal infection.
Duchenne muscular dystrophy (DMD) is a degenerative skeletal muscle disease caused by mutations in dystrophin. The degree of functional deterioration in muscle stem cells determines the severity of DMD. The mitogen-activated protein kinases (MAPKs), which are inactivated by MAPK phosphatases (MKPs), represent a central signaling node in the regulation of muscle stem cell function. Here we show that the dual-specificity protein phosphatase DUSP10/MKP-5 negatively regulates muscle stem cell function in mice. MKP-5 controlled JNK to coordinate muscle stem cell proliferation and p38 MAPK to control differentiation. Genetic loss of Mkp5 in mice improved regenerative myogenesis and dystrophin-deficient mdx mice lacking Mkp5 exhibited an attenuated dystrophic muscle phenotype. Hence, enhanced promyogenic MAPK activity preserved muscle stem cell function even in the absence of dystrophin and ultimately curtailed the pathogenesis associated with DMD. These results identify MKP-5 as an essential negative regulator of the promyogenic actions of the MAPKs and suggest that MKP-5 may serve as a target to promote muscle stem cell function in the treatment of degenerative skeletal muscle diseases.
A novel Bcl6 reporter mouse is used to dissect the developmental requirements, plasticity, and genetic profile of Tfh cells.
T follicular helper cells (Tfh cells) play a pivotal role in germinal center reactions, which require B cell lymphoma 6 (Bcl6) transcription factor. To analyze their relationships with other effector T cell lineages and their stability in vivo, we developed and analyzed a new Bcl6 reporter mouse alone or together with other lineage reporter systems. Assisted with genome-wide transcriptome analysis, we show substantial plasticity of T cell differentiation in the early phase of immune response. At this stage, CXCR5 appears to be expressed in a Bcl6-independent manner. Once Bcl6 is highly expressed, Tfh cells can persist in vivo and some of them develop into memory cells. Together, our results indicate Bcl6 as a bona fide marker for Tfh polarized program.
The tumour microenvironment thwarts conventional immunotherapy through multiple immunologic mechanisms, such as the secretion of the transforming growth factor-β (TGF-β), which stunts local tumour immune responses. Therefore, high doses of interleukin-2 (IL-2), a conventional cytokine for metastatic melanoma, induces only limited responses. To overcome the immunoinhibitory nature of the tumour microenvironment, we developed nanoscale liposomal polymeric gels (nanolipogels; nLGs) of drug-complexed cyclodextrins and cytokine-encapsulating biodegradable polymers that can deliver small hydrophobic molecular inhibitors and water-soluble protein cytokines in a sustained fashion to the tumour microenvironment. nLGs releasing TGF-β inhibitor and IL-2 significantly delayed tumour growth, increased survival of tumour-bearing mice, and increased the activity of natural killer cells and of intratumoral-activated CD8+ T-cell infiltration. We demonstrate that the efficacy of nLGs in tumour immunotherapy results from a crucial mechanism involving activation of both innate and adaptive immune responses.
There are no mucosal adjuvant formulations licensed for human use, despite protection against many mucosally-transmitted infections probably requiring immunity at the site of pathogen entry1. Polyethyleneimines (PEI) are organic polycations used as nucleic acid transfection reagents in vitro, and gene and DNA vaccine delivery vehicles in vivo2, 3. Here we show that PEI has unexpected and unusually potent mucosal adjuvant activity in conjunction with viral subunit glycoprotein antigens. Single intranasal administration of influenza HA or HSV-2 gD with PEI elicited robust protection from otherwise lethal infection, and was superior to existing experimental mucosal adjuvants. PEI formed nanoscale complexes with antigen that were taken up by antigen presenting cells in vitro and in vivo, promoted DC trafficking to draining lymph nodes and induced non-proinflammatory cytokine responses. PEI adjuvanticity required release of host dsDNA that triggered Irf-3-dependent signaling. PEI therefore merits further investigation as a mucosal adjuvant for human use.
mucosal adjuvant; influenza HA; HSV-2 gD; HIV-1 envelope glycoprotein; innate immunity; adaptive immunity