Role Of Interferon Regulatory Factor Research Articles

Essential role of interferon regulatory factor 4 (IRF4) in immune cell development.

The family of interferon regulatory factors, which includes nine mammalian members (IRF1-IRF9), acts as transcription factors for interferons and thus exerts regulatory functions in the immune system and in oncogenesis. Among these members, IRF4 expression is restricted to immune cells such as T and B lymphocytes, macrophages, and dendritic cells where it is a key factor in the regulation of differentiation and is required during the immune response for lymphocyte activation and the generation of immunoglobulin-secreting plasma cells. Consequently, dysregulation of IRF4 is associated with many lymphoid malignancies. Recent studies have demonstrated that depending on the context and stage of hematopoietic cell differentiation in which its expression is dysregulated, IRF4 may act as either an oncogene or a tumor-suppressor-like factor. In addition, it has been shown that IRF4 plays a pivotal role in the development and function of several autoimmune-associated cells. Various genetic and functional studies have also pointed to IRF4 as a master regulator for autoimmunity. In this review, the roles of IRF4 in the immune response are briefly summarized and discussed, with particular focus on its essential and distinct functions in immune cell development.

Inhibition of IRF8 Negatively Regulates Macrophage Function and Impairs Cutaneous Wound Healing.

The inflammatory response is essential for normal cutaneous wound healing. Macrophages, as critical inflammatory cells, coordinate inflammation and angiogenesis phases during wound healing. It has been reported that the transcription factor interferon regulatory factor 8 (IRF8), a member of the IRF family, plays a critical role in the development and function of macrophages and is associated with inflammation. However, the role of IRF8 in cutaneous wound healing and its underlying mechanism remain elusive. Through immunohistochemical (IHC) staining, we showed that IRF8 is involved in the wound repair process in mice and patients. Furthermore, we ascertain that the repression of IRF8 by small interfering RNA (siRNA) leads to delayed wound healing. To explore the mechanism by which IRF8 impacts wound healing, we observed its effect on macrophage-related mediators by IHC or real-time PCR. The results demonstrated that the inhibition of IRF8 decreases the mRNA expression of inflammatory mediators associated with M1 macrophage (il-1b, il-6, inos, and tnf-a) but no impact on M2 macrophage-related mediators (arg-1, mrc-1, and il-10) and the number of macrophages in the wounds. Furthermore, the inhibition of IRF8 induced apoptosis in the wounds. In summary, this study demonstrates that the down-regulation of IRF8 in the wound leads to impaired wound healing possibly through the regulation of macrophage function and apoptosis in skin wound.

Interferon regulatory factor 4 (IRF4) controls myeloid-derived suppressor cell (MDSC) differentiation and function.

Myeloid-derived suppressor cells (MDSCs) are immature cells that do not differentiate into mature myeloid cells. Two major populations of PMN-MDSCs (Ly6GhighLy6ClowGr1highCD11b+) and MO-MDSCs (Ly6G-Ly6ChighGr-1intCD11b+) have an immune suppressive function. Interferon regulatory factor 4 (IRF4) has a role in the negative regulation of TLR signaling and is associated with lymphoid cell development. However, the roles of IRF4 in myeloid cell differentiation are unclear. In this study, we found that IRF4 expression was remarkably suppressed during the development of MDSCs in the tumor microenvironment. Both the mRNA and protein levels of IRF4 in MDSCs were gradually reduced, depending on the development of tumors in the 4T1 model. siRNA-mediated knockdown of IRF4 in bone marrow cells promoted the differentiation of PMN-MDSCs. Similarly, IRF4 inhibition in bone marrow cells using simvastatin, which has been known to inhibit IRF4 expression, increased PMN-MDSC numbers. In contrast, IRF4 overexpression in bone marrow cells inhibited the total numbers of MDSCs, especially PMN-MDSCs. Notably, treatment with IL-4, an upstream regulator of IRF4, induced IRF4 expression in the bone marrow cells, and consequently, IL-4-induced IRF4 expression resulted in a decrease in PMN-MDSC numbers. Finally, we confirmed that IRF4 expression in MDSCs can modulate their activity to inhibit T cell proliferation through IL-10 production and ROS generation, and myeloid-specific deletion of IRF4 leads to the increase of MDSC differentiation. Our present findings indicate that IRF4 reduction induced by tumor formation can increase the number of MDSCs, and increases in the IRF4 expression in MDSCs may infringe on the immune-suppressive function of MDSCs.

Roles of Interferon Regulatory Factors in Chronic Myeloid Leukemia.

The Interferon Regulatory Factor (IRF) family consists of multiple transcription factors involved in the regulation of a variety of biological processes. Originally identified as transcriptional regulators of the type I interferon system, IRFs play a pivotal role in adaptive immunity, cell growth, differentiation and tumorigenesis. Hence, understanding IRF biology has important implications in the host response to cancer development and progression. Many lines of evidence suggest that different IRFs are involved in the pathogenesis of Chronic Myeloid Leukemia (CML), a myeloproliferative disorder caused by the BCR-ABL oncoprotein. BCR-ABL displays constitutive tyrosine kinase activity that favors cell proliferation, inhibits apoptosis and allows cell survival even in the absence of proper adhesion to the extracellular matrix. Different BCR-ABL tyrosine kinase inhibitors are currently available for CML treatment. These drugs are able to generate eight year CML-specific overall survival rates >90%, only a minority of patients will achieve molecular responses compatible with drug discontinuation. Thus, there is an unmet need for additional therapeutic targets that may lead to the cure of most patients diagnosed with CML. A growing body of evidence has suggested a role for both IRF4 and IRF8 in the pathogenesis of CML. Furthermore, IRF1 is consistently deleted at one or both alleles in patients with leukemia and myelodysplasia. Finally, we have recently demonstrated that IRF5 is a target of BCR-ABL kinase activity and reduces CML cell proliferation. In this article, we provide an update on the current knowledge of the role of the IRFs in CML.

Abstract 4141: Role of interferon regulatory factor 5 in anti-tumor immunity: Orchestration of a functional tertiary lymphoid structure

Abstract The ability of breast cancer cells to metastasize is due to intrinsic intratumoral and extrinsic microenvironment changes. Many breast cancers are heavily infiltrated by immune cells and these infiltrating leukocytes are commonly observed around tumors in patients with invasive ductal carcinoma. Several recent studies show that the presence of tumor infiltrating leukocytes in human breast cancer tissue is associated with improved outcome, suggesting that the immune system is participating in the control and elimination of tumor cells. One way in which epithelial-derived cancers evade immunity is through dysregulation of cytokines and chemokines that “call in” specific immune cells to form a functional ectopic lymphoid-like structure termed a tertiary lymphoid structure (TLS) near the tumor. TLS are important for cell-mediated and humoral immunity and are extremely efficient immunological tools as the presentation of antigen occurs to both B and T cells. Although very little is known about the processes that drive TLS formation, data indicate that the presence of a TLS next to a solid cancer, including breast cancer, is a strong positive prognostic indicator. Recent data from our lab and others show that expression of the transcription factor interferon regulatory factor 5 (IRF5) in a human breast cancer molecular signature predicts increased survival and lower incidence of metastasis. We recently identified IRF5 as an important intrinsic regulator of mammary epithelial cell migration and metastasis. We also found that IRF5 within a breast tumor regulates the expression of cytokines/chemokines, such as CXCL13, that mediate immune cell trafficking. We previously reported that tumor-conditioned media (TCM) from IRF5-positive breast tumor cells contains CXCL13 and induces trafficking of CD19+CXCR5+ B cells and CD3+CD4+CXCR5+ T follicular helper-like (Tfh) cells to the TCM. CXCL13 is a key player in the formation of a TLS as it recruits in the specific cells and activates the B cells to produce immunoglobulins. Further analysis of immune cell trafficking to TCM from IRF5+ and IRF5- breast tumor cells reveals specificity for the trafficking of anti-tumorigenic B and T cell subsets to IRF5-positive TCM, such as transitional, memory, and plasmablast/plasma B cells, along with Th1 and Tfh cells, rather than pro-tumorigenic, immunosuppressive Bregs, Th2, and Tregs that were found to specifically migrate to IRF5-negative TCM. Analysis of formalin-fixed paraffin-embedded breast tumors by immunofluorescence microscopy revealed a significant correlation between IRF5 intratumoral expression and the presence of a TLS. Furthermore, preliminary data from a murine model of invasive mammary tumorigenesis supports a critical role for IRF5 in anti-tumor immunity. Together, these data implicate IRF5 in the generation of a functional TLS and as a critical mediator of anti-tumor immunity. Citation Format: Erica Pimenta, Ryan Weiss, Dan Li, Betsy Barnes. Role of interferon regulatory factor 5 in anti-tumor immunity: Orchestration of a functional tertiary lymphoid structure. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4141.

Abstract 3677: Loss of IRF5 induces spontaneous murine mammary tumorigenesis

Abstract Despite significant research efforts, breast cancer is still the most common malignancy in women and the most common cause of cancer death worldwide. A major challenge in breast cancer treatment is disease heterogeneity that is contributed by many factors including intrinsic cell factors, microenvironment, angiogenesis and tumor-specific immune responses. Interferon regulatory factor 5 (IRF5) is a transcription factor that controls inflammatory and immune responses. Analysis of over 3,000 human breast cancer tissues revealed that high expression of IRF5 correlates with increased survival and lower incidence of metastasis, whereas the lower quartile of IRF5 expression is a significant marker of poor prognosis for recurrence-free survival. These data support a tumor suppressor role for IRF5. To examine how loss of IRF5 expression may play a role in spontaneous mammary tumorigenesis, we generated Irf5 knockout (ko) mice in a BALB/C background. In mammary glands harvested from one-year-old female virgin ko mice (n = 15), we found an increased incidence (16%) of mammary carcinoma in situ as compared to their wild-type littermates (4%; n = 18). Of interest, the number of tumor bearing mice was significantly higher (38%) in retired ko female breeders (n = 8); however, there were no abnormalities detected in one-year-old male ko virgins or breeders (n = 6). Cellular and molecular analysis of female ko and wild-type littermates revealed that Irf5 deficiency enhanced mammary epithelial cell proliferation as indicated by an increased number of Ki67 expressing cells, and resulted in abnormal hyperbranching, which may contribute to mammary tumorigenesis. Irf5 ko breeders also showed impaired mammary gland involution after weaning, which has been shown to facilitate mammary tumor formation in humans. Taken together, these findings demonstrate that IRF5 is a gender-specific tumor suppressor in breast cancer. In this ongoing study, we are further investigating the intrinsic and extrinsic (microenvironment) role of IRF5 in mammary tumor initiation and progression. Citation Format: Dan Li, Xiaohui Bi, Corey Goyeneche, Amy Pitler, Betsy Barnes. Loss of IRF5 induces spontaneous murine mammary tumorigenesis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3677.

Relevance of Interferon Regulatory Factor-8 Expression in Myeloid-Tumor Interactions.

Perturbations in myelopoiesis are a common feature in solid tumor biology, reflecting the central premise that cancer is not only a localized affliction but also a systemic disease. Because the myeloid compartment is essential for the induction of adaptive immunity, these alterations in myeloid development contribute to the failure of the host to effectively manage tumor progression. These "dysfunctional" myeloid cells have been coined myeloid-derived suppressor cells (MDSCs). Interestingly, such cells not only arise in neoplasia but also are associated with many other inflammatory or pathologic conditions. MDSCs affect disease outcome through multiple mechanisms, including their ability to mediate generalized or antigen-specific immune suppression. Consequently, MDSCs pose a significant barrier to effective immunotherapy in multiple disease settings. Although much interest has been devoted to unraveling mechanisms by which MDSCs mediate immune suppression, a large gap has remained in our understanding of the mechanisms that drive their development in the first place. Investigations into this question have identified an unrecognized role of interferon regulatory factor-8 (IRF-8), a member of the IRF family of transcription factors, in tumor-induced myeloid dysfunction. Ordinarily, IRF-8 is involved in diverse stages of myelopoiesis, namely differentiation and lineage commitment toward monocytes, dendritic cells, and granulocytes. Several recent studies now support the hypothesis that IRF-8 functions as a "master" negative regulator of MDSC formation in vivo. This review focuses on IRF-8 as a potential target suppressed by tumors to cripple normal myelopoiesis, redirecting myeloid differentiation toward the emergence of MDSCs. Understanding the bases by which neoplasia drives MDSC accumulation has the potential to improve the efficacy of therapies that require a competent myeloid compartment.

A Simple Screening Approach To Prioritize Genes for Functional Analysis Identifies a Role for Interferon Regulatory Factor 7 in the Control of Respiratory Syncytial Virus Disease.

Greater understanding of the functions of host gene products in response to infection is required. While many of these genes enable pathogen clearance, some enhance pathogen growth or contribute to disease symptoms. Many studies have profiled transcriptomic and proteomic responses to infection, generating large data sets, but selecting targets for further study is challenging. Here we propose a novel data-mining approach combining multiple heterogeneous data sets to prioritize genes for further study by using respiratory syncytial virus (RSV) infection as a model pathogen with a significant health care impact. The assumption was that the more frequently a gene is detected across multiple studies, the more important its role is. A literature search was performed to find data sets of genes and proteins that change after RSV infection. The data sets were standardized, collated into a single database, and then panned to determine which genes occurred in multiple data sets, generating a candidate gene list. This candidate gene list was validated by using both a clinical cohort and in vitro screening. We identified several genes that were frequently expressed following RSV infection with no assigned function in RSV control, including IFI27, IFIT3, IFI44L, GBP1, OAS3, IFI44, and IRF7. Drilling down into the function of these genes, we demonstrate a role in disease for the gene for interferon regulatory factor 7, which was highly ranked on the list, but not for IRF1, which was not. Thus, we have developed and validated an approach for collating published data sets into a manageable list of candidates, identifying novel targets for future analysis. IMPORTANCE Making the most of "big data" is one of the core challenges of current biology. There is a large array of heterogeneous data sets of host gene responses to infection, but these data sets do not inform us about gene function and require specialized skill sets and training for their utilization. Here we describe an approach that combines and simplifies these data sets, distilling this information into a single list of genes commonly upregulated in response to infection with RSV as a model pathogen. Many of the genes on the list have unknown functions in RSV disease. We validated the gene list with new clinical, in vitro, and in vivo data. This approach allows the rapid selection of genes of interest for further, more-detailed studies, thus reducing time and costs. Furthermore, the approach is simple to use and widely applicable to a range of diseases.

Th17 cell differentiation proceeds independently of IRF8.

The transcriptional repressor/activator interferon regulatory factor 8 (IRF8) modulates the differentiation of a multitude of hematopoietic lineages. However, the role of IRF8 in CD4(+) T-cell development is less well defined, with a recent study implicating IRF8 as an intrinsic repressor of interleukin-17 (IL-17) expressing T helper type 17 (Th17) cell differentiation. Using an IRF8-EGFP reporter strain we have confirmed that IRF8 is expressed in all T helper lineages, including Th17 cells. The loss of IRF8 did not affect Th17 differentiation in vitro, beyond a small increase in IL-22 expression. Moreover, IRF8 deficiency did not enhance the Th17 immune response in experimental T-cell transfer colitis. Together, these results suggest that IRF8 does not play an essential intrinsic role in Th17 cell differentiation.

Elucidating the contribution of IRF3 to effector and memory cytotoxic T cell responses after influenza virus infection

Abstract The role of interferon regulatory factor (IRF) 3 in initiating the type I interferon response in innate immune cells has been well studied in the context of viral infection. However, it is less clear what impact IRF3 has in shaping and maintaining adaptive immune responses. Previous reports have demonstrated that when restimulated, both CD4 and CD8 T cells from IRF3 knockout (KO) mice have significantly reduced expression of Granzyme B 30 days after infection or following secondary influenza A virus (IAV) challenge. To determine whether deficiencies in Granzyme B correlate with CTL function, we are examining the cytotoxic potential and specific antiviral lytic activity after primary and secondary challenge with IAV in CD4 and CD8 cells. Additionally, as early signals derived from antigen presenting cells (APCs) influence effector and memory T cell development, the innate immune response following IAV infection was examined. Our results demonstrate the innate response is not compromised in IRF3 KO mice at day 1 or 3 post IAV infection in the draining lymph node. Interestingly, macrophages and dendritic cells had decreased expression of MHCII and CD86 at both time points in the lung. These results suggest that while initial priming is sufficient in the draining lymph nodes, secondary factors in the lung could provide T cells with the signals needed for effective memory development. Together, this work provides insight into the molecular regulation of T cell responses to viral infections and highlights the role IRFs play in the development of high quality effector and memory T cells.

The Role of Interferon Regulatory Factor-1 on LPS-Induced ROS Production and Mitochondrial Damage in Macrophages

The Role of Interferon Regulatory Factor-1 on LPS-Induced ROS Production and Mitochondrial Damage in Macrophages

The emerging role of interferon regulatory factor 9 in the antiviral host response and beyond

The host response to viral infections relies on tightly regulated and intricate signaling pathways involving type I interferons (IFN-Is). The IFN-Is mediate their antiviral effects predominantly through a signaling factor complex that comprises the transcription factors, interferon regulatory factor 9 (IRF9) and the signal transducers and activators of transcription (STAT) 1 and STAT2. While STAT1 and STAT2 have been studied extensively, the biological significance of IRF9 is only beginning to emerge. Recent studies have revealed a unique role for IRF9 as a conductor of the cellular responses to IFN-Is. Intriguingly, novel roles for IRF9 outside of the antiviral response are also being identified. Thus IRF9 may have a more extensive influence on cellular processes than previously recognized, ranging from antiviral immune responses to oncogenesis and gut homeostasis. In this review, we will focus on the distinct and emerging roles of IRF9 in the antiviral host response and beyond.

Interferon regulatory factor 7 regulates airway epithelial cell responses to human rhinovirus infection.

BackgroundHuman rhinoviruses (HRV) cause the majority of colds and trigger exacerbations of chronic lower airway diseases. Airway epithelial cells are the primary site for HRV infection and replication, and the initiation of host inflammatory responses. At present, the molecular mechanisms that underpin HRV responses in airway epithelial cells are incompletely understood. The aim of this study was to employ microarray profiling, upstream regulator analysis, and siRNA mediated gene silencing to further our understanding of the role of interferon regulatory factor 7 (IRF7) in this response.MethodsPrimary human bronchial epithelial cells (HBE) where transfected with siRNA that targets IRF7 or a non-silencing control (all-star control) using Lipofectamine. The cells were allowed to recover, and then cultured in the presence or absence of HRV-16 for 24 h. Global patterns of gene expression were profiled on microarrays. A subset of genes identified in the microarray study were validated at the mRNA and/or protein level using real time RT-qPCR, ELISA, and western blots.ResultsHundreds of genes were upregulated in HBE during HRV infection. Pathways analysis demonstrated that these genes were mainly involved in type I and II interferon signaling, RIG-I/MDA5 signaling, antigen processing and presentation, and apoptosis. Upstream regulator analysis of these data suggested that IRF7 was a major molecular driver of this response. Knockdown of IRF7 reduced the HRV-driven upregulation of genes involved in antiviral responses (interferon signaling, Toll-like receptor signaling, NOD-like receptor signaling, RIG-I/MDA5 signaling), and increased the expression of genes that promote inflammation (e.g. CXCL5, IL-33, IL1RL1) and the response to oxidative stress. However, the majority of genes that were perturbed by HRV in HBE cells including those that are known to be regulated by IRF7 were insensitive to IRF7 knockdown. Upstream regulator analysis of the part of the response that was insensitive to IRF7 knockdown suggested it was driven by NF-κB, STAT1, STAT3, and IRF1.ConclusionsOur findings demonstrate that IRF7 regulates the expression of genes involved in antiviral immunity, inflammation, and the response to oxidative stress during HRV infections in HBE cells, and also suggests that other transcription factors play a major role in this response.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2405-z) contains supplementary material, which is available to authorized users.

IRF5 regulates lung macrophages M2 polarization during severe acute pancreatitisin vitro

AIMTo investigate the role of interferon regulatory factor 5 (IRF5) in reversing polarization of lung macrophages during severe acute pancreatitis (SAP) in vitro.METHODSA mouse SAP model was established by intraperitoneal (ip) injections of 20 μg/kg body weight caerulein. Pathological changes in the lung were observed by hematoxylin and eosin staining. Lung macrophages were isolated from bronchoalveolar lavage fluid. The quantity and purity of lung macrophages were detected by fluorescence-activated cell sorting and evaluated by real-time polymerase chain reaction (RT-PCR). They were treated with IL-4/IRF5 specific siRNA (IRF5 siRNA) to reverse their polarization and were evaluated by detecting markers expression of M1/M2 using RT-PCR.RESULTSSAP associated acute lung injury (ALI) was induced successfully by ip injections of caerulein, which was confirmed by histopathology. Lung macrophages expressed high levels of IRF5 as M1 phenotype during the early acute pancreatitis stages. Reduction of IRF5 expression by IRF5 siRNA reversed the action of macrophages from M1 to M2 phenotype in vitro. The expressions of M1 markers, including IRF5 (S + IRF5 siRNA vs S + PBS, 0.013 ± 0.01 vs 0.054 ± 0.047, P < 0.01), TNF-α (S + IRF5 siRNA vs S + PBS, 0.0003 ± 0.0002 vs 0.019 ± 0.018, P < 0.001), iNOS (S + IRF5 siRNA vs S + PBS, 0.0003 ± 0.0002 vs 0.026 ± 0.018, P < 0.001) and IL-12 (S + IRF5 siRNA vs S + PBS, 0.000005 ± 0.00004 vs 0.024 ± 0.016, P < 0.001), were decreased. In contrast, the expressions of M2 markers, including IL-10 (S + IRF5 siRNA vs S + PBS, 0.060 ± 0.055 vs 0.0230 ± 0.018, P < 0.01) and Arg-1 (S + IRF5 siRNA vs S + PBS, 0.910 ± 0.788 vs 0.0036 ± 0.0025, P < 0.001), were increased. IRF5 siRNA could reverse the lung macrophage polarization more effectively than IL-4.CONCLUSIONTreatment with IRF5 siRNA can reverse the pancreatitis-induced activation of lung macrophages from M1 phenotype to M2 phenotype in SAP associated with ALI.

Inhibition of Interferon Regulatory Factor 4 Attenuates Acute Liver Allograft Rejection in Mice.

Acute liver allograft rejection is a serious complication after liver transplantation. Interferon regulatory factor 4 (IRF4) is expressed predominantly in the immune system and plays an important role in its development and function. However, the role of IRF4 in liver transplantation has never been investigated. In our current study, to evaluate the effect of IRF4 inhibition on recipient survival, IRF4 siRNA, or control siRNA, or PBS was injected into the liver allograft recipients through caudal vein. The survival time of mice treated with IRF4 siRNA (MST=31.5days) was prolonged significantly compared with that of mice treated with PBS (MST=6days) or control siRNA (MST=6.5days) (P<0.001). IRF4 siRNA treatment displays lower induction of pro-inflammatory levels, including TNF-α, IL-6 and IFN-γ, and higher induction of anti-inflammatory IL-10 levels. Administration of anti-IL-10 into IRF4 siRNA-treated mice resulted in shortened allograft survival and increased rejection scores. Furthermore, IRF4 inhibition promotes M2 macrophage differentiation invivo and invitro. And inhibition of macrophages with GdCl3 reverses the prolonged liver allograft survival and decreased liver rejection scores induced by IRF4 siRNA. In conclusion, inhibition of IRF4 attenuates acute liver allograft rejection in mice, and this is associated with promoted M2 macrophage differentiation.

Beyond innate immunity: the role of interferon regulatory factor 3 in CD4+ T cell function (IRM15P.462)

Abstract Interferon regulatory factor 3 (IRF3) is a transcription factor found in the cytoplasm of most nucleated cells. Upon pathogen recognition, IRF3 becomes activated and translocates to the nucleus where it mediates the production of type I interferon (IFN). Whereas IRF3 has been studied extensively in the context of type I IFN production and innate immunity, its role in adaptive immunity has remained largely unexplored. The objective of our research is to elucidate the role of IRF3 in CD4+ T cell function. Our findings demonstrate that IRF3-deficient CD4+ T cells show robust proliferation in response to TCR engagement, but are compromised in their ability to differentiate into specialized T helper cell subsets—most notably IL-17-producing Th17 cells. As such, CD4+ T cells lacking IRF3 expression fail to induce disease in the T cell transfer model of colitis. These studies reveal a novel, T cell-intrinsic function of IRF3 and extend its role beyond the innate immune response to pathogens.

IRF3 deficiency impacts granzyme B expression and maintenance of memory T cell function in response to viral infection

The role of interferon regulatory factor 3 (IRF3) in the innate immune response to infection has been well studied. However, less is known about IRF3 signaling in shaping the adaptive T cell response. To determine the role of IRF3 in the generation and maintenance of effective anti-viral T cell responses, mice deficient in IRF3 were infected with a potentially persistent virus, Theiler's murine encephalomyelitis virus (TMEV) or with a model acute infection, influenza A virus (IAV). IRF3 was required to prevent TMEV persistence and induce robust TMEV specific effector T cell responses at the site of infection. This defect was more pronounced in the memory phase with an apparent lack of TMEV-specific memory T cells expressing granzyme B (GrB) in IRF3 deficient mice. In contrast, IRF3 had no effect on antigen specific T cell responses at the effector stage during IAV infection. However, memory T cell responses to IAV were also impaired in IRF3 deficient mice. Furthermore, addition of cytokines during peptide restimulation could not restore GrB expression in IRF3 deficient memory T cells. Taken together, IRF3 plays an important role in the maintenance of effective anti-viral T cell memory responses.

A critical role for interferon regulatory factor 9 in cerebral ischemic stroke.

The failure of past efforts to develop effective stroke treatments is at least partially because these treatments often interfered with essential physiological functions, even though they are targeted toward pathophysiological events, such as inflammation, excitotoxicity, and oxidative stress. Thus, the direct targeting of endogenous neuroprotective or destructive elements holds promise as a potential new approach to treating this devastating condition. Interferon regulatory factor 9 (IRF9), a transcription factor that regulates innate immune responses, has been implicated in neurological pathology. Here, we provide new evidence that IRF9 directly mediates neuronal death in male mice. In response to ischemia/reperfusion (I/R), IRF9 accumulated in neurons. IRF9 deficiency markedly mitigated both poststroke neuronal death and neurological deficits, whereas the neuron-specific overexpression of IRF9 sensitized neurons to death. The histone deacetylase Sirt1 was identified as a novel negative transcriptional target of IRF9 both in vivo and in vitro. IRF9 inhibits Sirt1 deacetylase activity, culminating in the acetylation and activation of p53-mediated cell death signaling. Importantly, both the genetic and pharmacological manipulation of Sirt1 effectively counteracted the pathophysiological effects of IRF9 on stroke outcome. These findings indicate that, rather than activating a delayed innate immune response, IRF9 directly activates neuronal death signaling pathways through the downregulation of Sirt1 deacetylase in response to acute I/R stress.

The Roles of Interferon Regulatory Factors 1 and 2 in the Progression of Human Pancreatic Cancer

Pancreatic cancer is one of the most malignant diseases worldwide. Interferon regulatory factor (IRF) 1 and IRF2 function as a tumor suppressor and oncoprotein, respectively, in several types of cancers. We investigated whether IRF1 and IRF2 are involved in the progression of pancreatic cancer. We examined the expressions of IRF1 and IRF2 in pancreatic cancer specimens and analyzed the association with clinicopathologic features. We evaluated the biological effects of IRF1 and IRF2 using a pancreatic cancer cell line. The expression levels of IRF1 and IRF2 were decreased and increased, respectively, in the pancreatic cancer cells compared with those observed in the paired normal areas. A higher expression of IRF1 was associated with better features of tumor differentiation, infiltration depth, tumor size, and survival, whereas that of IRF2 was associated with a worse feature of tumor infiltration depth. Interferon regulatory factor 2-overexpressing PANC-1 cells exhibited an increase in cell growth, less apoptotic features, and chemoresistance to gemcitabine treatment. In contrast, IRF1-overexpressing cells exhibited the opposite characteristics. Interferon regulatory factors 1 and 2 may regulate the progression of pancreatic cancer by functioning as an antioncoprotein and oncoprotein, respectively. These molecules may serve as potential targets of therapy.

A novel role for interferon regulatory factor 1 (IRF1) in regulation of bone metabolism.

Increased risk of bone fractures is observed in patients with chronic inflammatory conditions, such as inflammatory bowel disease and rheumatoid arthritis. Members of the Interferon Response Factor family of transcriptional regulators, IRF1 and IRF8, have been identified as genetic risk factors for several chronic inflammatory and autoimmune diseases. We have investigated a potential role for the Irf1 gene in bone metabolism. Here, we report that Irf1−/−mutant mice show altered bone morphology in association with altered trabecular bone architecture and increased cortical thickness and cellularity. Ex vivo studies on cells derived from bone marrow stimulated with Rank ligand revealed an increase in size and resorptive activity of tartrate-resistant acid-positive cells from Irf1−/− mutant mice compared with wild-type control mice. Irf1 deficiency was also associated with decreased proliferation of bone marrow-derived osteoblast precursors ex vivo, concomitant with increased mineralization activity compared with control cells. We show that Irf1 plays a role in bone metabolism and suggest that Irf1 regulates the maturation and activity of osteoclasts and osteoblasts. The altered bone phenotype of Irf1−/− mutants is strikingly similar to that of Stat1−/− mice, suggesting that the two interacting proteins play a critical enabling role in the common regulation of these two cell lineages.