Instruct: Given a scientific claim, retrieve relevant documents that support or refute the claim.
Query: Normal granulomas form in the absence of TNF in Zebrafish.
Tumor necrosis factor (TNF), a key effector in controlling tuberculosis, is thought to exert protection by directing formation of granulomas, organized aggregates of macrophages and other immune cells. Loss of TNF signaling causes progression of tuberculosis in humans, and the increased mortality of Mycobacterium tuberculosis-infected mice is associated with disorganized necrotic granulomas, although the precise roles of TNF signaling preceding this endpoint remain undefined. We monitored transparent Mycobacterium marinum-infected zebrafish live to conduct a stepwise dissection of how TNF signaling operates in mycobacterial pathogenesis. We found that loss of TNF signaling caused increased mortality even when only innate immunity was operant. In the absence of TNF, intracellular bacterial growth and granuloma formation were accelerated and was followed by necrotic death of overladen macrophages and granuloma breakdown. Thus, TNF is not required for tuberculous granuloma formation, but maintains granuloma integrity indirectly by restricting mycobacterial growth within macrophages and preventing their necrosis.
The family of tumor necrosis factor receptors (TNFRs) and their ligands form a regulatory signaling network that controls immune responses. Various members of this receptor family respond differently to the soluble and membrane-bound forms of their respective ligands. However, the determining factors and underlying molecular mechanisms of this diversity are not yet understood. Using an established system of chimeric TNFRs and novel ligand variants mimicking the bioactivity of membrane-bound TNF (mTNF), we demonstrate that the membrane-proximal extracellular stalk regions of TNFR1 and TNFR2 are crucial in controlling responsiveness to soluble TNF (sTNF). We show that the stalk region of TNFR2, in contrast to the corresponding part of TNFR1, efficiently inhibits both the receptor's enrichment/clustering in particular cell membrane regions and ligand-independent homotypic receptor preassembly, thereby preventing sTNF-induced, but not mTNF-induced, signaling. Thus, the stalk regions of the two TNFRs not only have implications for additional TNFR family members, but also provide potential targets for therapeutic intervention.
IL-17 is a novel, CD4+ T cell-restricted cytokine. In vivo, it stimulates hematopoiesis and causes neutrophilia consisting of mature granulocytes. In this study, we show that IL-17-mediated granulopoiesis requires G-CSF release and the presence or induction of the transmembrane form of stem cell factor (SCF) for optimal granulopoiesis. However, IL-17 also protects mice from G-CSF neutralization-induced neutropenia. G-CSF neutralization completely reversed IL-17-induced BM progenitor expansion, whereas splenic CFU-GM/CFU-granulocyte-erythrocyte-megakaryocyte-monocyte was only reduced by 50% in both Sl/Sld and littermate control mice. Thus, there remained a significant SCF/G-CSF-independent effect of IL-17 on splenic granulopoiesis, resulting in a preservation of mature circulating granulocytes. IL-17 is a cytokine that potentially interconnects lymphocytic and myeloid host defense and may have potential for therapeutic development.
The human tuberculous granuloma provides the morphological basis for local immune processes central to the outcome of tuberculosis. Because of the scarcity of information in human patients, the aim of the present study was to gain insights into the functional and structural properties of infiltrated tissue. To this end, the mycobacterial load in lesions and dissemination to different tissue locations were investigated, as well as distribution, biological functions, and interactions of host immune cells. Analysis of early granuloma formation in formerly healthy lung tissue revealed a spatio-temporal sequence of cellular infiltration to sites of mycobacterial infection. A general structure of the developing granuloma was identified, comprising an inner cell layer with few CD8(+) cells surrounding the necrotic centre and an outer area of lymphocyte infiltration harbouring mycobacteria-containing antigen-presenting cells as well as CD4(+), CD8(+), and B cells in active follicle-like centres resembling secondary lymphoid organs. It is concluded that the follicular structures in the peripheral rim of granulomas serve as a morphological substrate for the orchestration of the enduring host response in pulmonary tuberculosis.
PURPOSE OF REVIEW Recent discoveries implicate neutrophils as important regulators of innate and adaptive immunity and in the development of organ damage in systemic autoimmune diseases, including systemic lupus erythematosus (SLE). RECENT FINDINGS Various putative SLE biomarkers are neutrophil-related, including neutrophil granular proteins and histones undergoing post-translational modifications during neutrophil extracellular trap (NET) formation. In the bone marrow, lupus neutrophils can drive B and T cell abnormalities, at least in part, by their enhanced production of type-I interferons, tumor necrosis factor-alpha (TNFα) and the B-cell stimulating factors B-cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL). Lupus neutrophils and, in particular, lupus low-density granulocytes (a distinct pathogenic subset) display epigenetic modifications and genomic alterations that may be relevant to their deleterious roles in SLE. Proteins and enzymes externalized by lupus NETs can affect vascular health by inducing endothelial apoptosis and oxidizing lipoproteins. Hampering NET formation through peptidylarginine deiminase inhibitors abrogates lupus phenotype and atherosclerosis in murine studies. SUMMARY Recent discoveries support the notion that neutrophils, low-density granulocytes and aberrant NET formation and clearance play important roles in lupus pathogenesis. Future studies should focus on how to selectively target these immunostimulatory pathways in this disease.
Neutrophil is a key cell in pathophysiology of granulomatosis with polyangiitis. Recently, neutrophil extracellular traps were described in this disease. Mitochondrial DNA is also released during traps formation. We measured circulating cell-free mitochondrial and genomic DNA in serum of patients with granulomatosis with polyangiitis. Subjects with the disease (14 active and 11 in remission stage) and 10 healthy controls were enrolled. Quantitative real-time polymerase chain reaction (PCR) was used to measure 79 base pairs (bp) and 230 bp mtDNA fragments. Alu repeats were quantified to evaluate abundance of nuclear DNA in serum at the presence of plasmid control. Both fragments of mtDNA (79 bp and 230 bp) and genomic DNA were elevated significantly in granulomatosis with polyangiitis compared to controls. Only the shorter 79 bp mtDNA correlated with active stage of granulomatosis with polyangiitis and clinical symptoms. A mechanism of extracellular release of mitochondrial DNA accompanies the active stage of the disease. Circulating mtDNA is extremely high in untreated patients. This suggests that biomarker properties of mtDNA are useful for monitoring of treatment.
Half a century ago, chronic granulomatous disease (CGD) was first described as a disease fatally affecting the ability of children to survive infections. Various milestone discoveries have since been made, from an insufficient ability of patients’ leucocytes to kill microbes to the underlying genetic abnormalities. In this inherited disorder, phagocytes lack NADPH oxidase activity and do not generate reactive oxygen species, most notably superoxide anion, causing recurrent bacterial and fungal infections. Patients with CGD also suffer from chronic inflammatory conditions, most prominently granuloma formation in hollow viscera. The precise mechanisms of the increased microbial pathogenicity have been unclear, and more so the reasons for the exaggerated inflammatory response. Here we show that a superoxide-dependent step in tryptophan metabolism along the kynurenine pathway is blocked in CGD mice with lethal pulmonary aspergillosis, leading to unrestrained Vγ1+ γδ T-cell reactivity, dominant production of interleukin (IL)-17, defective regulatory T-cell activity and acute inflammatory lung injury. Although beneficial effects are induced by IL-17 neutralization or γδ T-cell contraction, complete cure and reversal of the hyperinflammatory phenotype are achieved by replacement therapy with a natural kynurenine distal to the blockade in the pathway. Effective therapy, which includes co-administration of recombinant interferon-γ (IFN-γ), restores production of downstream immunoactive metabolites and enables the emergence of regulatory Vγ4+ γδ and Foxp3+ αβ T cells. Therefore, paradoxically, the lack of reactive oxygen species contributes to the hyperinflammatory phenotype associated with NADPH oxidase deficiencies, through a dysfunctional kynurenine pathway of tryptophan catabolism. Yet, this condition can be reverted by reactivating the pathway downstream of the superoxide-dependent step.
Regulatory T (Treg) cells play a pivotal role in suppressing self-harmful T cell responses, but how Treg cells mediate suppression to maintain immune homeostasis and limit responses during inflammation is unclear. Here we show that effector Treg cells express high amounts of the integrin αvβ8, which enables them to activate latent transforming growth factor-β (TGF-β). Treg-cell-specific deletion of integrin αvβ8 did not result in a spontaneous inflammatory phenotype, suggesting that this pathway is not important in Treg-cell-mediated maintenance of immune homeostasis. However, Treg cells lacking expression of integrin αvβ8 were unable to suppress pathogenic T cell responses during active inflammation. Thus, our results identify a mechanism by which Treg cells suppress exuberant immune responses, highlighting a key role for effector Treg-cell-mediated activation of latent TGF-β in suppression of self-harmful T cell responses during active inflammation.
Although myeloid cell activation is requisite for an optimal innate immune response, this process must be tightly controlled to prevent collateral host tissue damage. Kruppel-like factor 2 (KLF2) is a potent regulator of myeloid cell proinflammatory activation. As an approximately 30% to 50% reduction in KLF2 levels has been observed in human subjects with acute or chronic inflammatory disorders, we studied the biological response to inflammation in KLF2(+/-) mice. Herein, we show that partial deficiency of KLF2 modulates the in vivo response to acute (sepsis) and subacute (skin) inflammatory challenge. Mechanistically, we link the anti-inflammatory effects of KLF2 to the inhibition of NF-κB transcriptional activity. Collectively, the observations provide biologically relevant insights into KLF2-mediated modulation of these inflammatory processes that could potentially be manipulated for therapeutic gain.
Tuberculosis, a major health problem in developing countries, has reemerged in recent years in many industrialized countries. The increased susceptibility of immunocompromised individuals to tuberculosis, and many experimental studies indicate that T cell-mediated immunity plays an important role in resistance. The lymphokine interferon gamma (IFN-gamma) is thought to be a principal mediator of macrophage activation and resistance to intracellular pathogens. Mice have been developed which fail to produce IFN-gamma (gko), because of a targeted disruption of the gene for IFN-gamma. Upon infection with Mycobacterium tuberculosis, although they develop granulomas, gko mice fail to produce reactive nitrogen intermediates and are unable to restrict the growth of the bacilli. In contrast to control mice, gko mice exhibit heightened tissue necrosis and succumb to a rapid and fatal course of tuberculosis that could be delayed, but not prevented, by treatment with exogenous recombinant IFN-gamma.
Schizophrenia may arise from subtle abnormalities in brain development due to alterations in the functions of candidate susceptibility genes such as Disrupted-in-schizophrenia 1 (DISC1) and Neuregulin 1 (NRG1). To provide novel insights into the functions of DISC1 in brain development, we mapped the expression of zebrafish disc1 and set out to characterize its role in early embryonic development using morpholino antisense methods. These studies revealed a critical requirement for disc1 in oligodendrocyte development by promoting specification of olig2-positive cells in the hindbrain and other brain regions. Since NRG1 has well-documented roles in myelination, we also analyzed the roles of nrg1 and ErbB signalling in zebrafish brain development and we observed strikingly similar defects to those seen in disc1 morphant embryos. In addition to their effects on oligodendrocyte development, knock-down of disc1 or nrg1 caused near total loss of olig2-positive cerebellar neurones, but caused no apparent loss of spinal motor neurones. These findings suggest that disc1 and nrg1 function in common or related pathways controlling development of oligodendrocytes and neurones from olig2-expressing precursor cells. Like DISC1 and NRG1, OLIG2 and ERBB4 are promising candidate susceptibility genes for schizophrenia. Hence our findings in the zebrafish embryo suggest that hitherto unappreciated neurodevelopmental connections may exist between key human schizophrenia susceptibility genes. These connections could be investigated in Disc1 and Nrg1 mouse models and in genetically defined groups of patients in order to determine whether they are relevant to the pathobiology of schizophrenia. GenBank accession number for Danio rerio disc1: EU273350.
Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by a breakdown of tolerance to nuclear antigens and the development of immune complexes. Genomic approaches have shown that human SLE leukocytes homogeneously express type I interferon (IFN)-induced and neutrophil-related transcripts. Increased production and/or bioavailability of IFN-α and associated alterations in dendritic cell (DC) homeostasis have been linked to lupus pathogenesis. Although neutrophils have long been shown to be associated with lupus, their potential role in disease pathogenesis remains elusive. Here, we show that mature SLE neutrophils are primed in vivo by type I IFN and die upon exposure to SLE-derived anti-ribonucleoprotein antibodies, releasing neutrophil extracellular traps (NETs). SLE NETs contain DNA as well as large amounts of LL37 and HMGB1, neutrophil proteins that facilitate the uptake and recognition of mammalian DNA by plasmacytoid DCs (pDCs). Indeed, SLE NETs activate pDCs to produce high levels of IFN-α in a DNA- and TLR9 (Toll-like receptor 9)-dependent manner. Our results reveal an unsuspected role for neutrophils in SLE pathogenesis and identify a novel link between nucleic acid-recognizing antibodies and type I IFN production in this disease.
Environmental and genetic aberrations lead to neural tube closure defects (NTDs) in 1 out of every 1,000 births. Mouse and frog models for these birth defects have indicated that Van Gogh-like 2 (Vangl2, also known as Strabismus) and other components of planar cell polarity (PCP) signalling might control neurulation by promoting the convergence of neural progenitors to the midline. Here we show a novel role for PCP signalling during neurulation in zebrafish. We demonstrate that non-canonical Wnt/PCP signalling polarizes neural progenitors along the anteroposterior axis. This polarity is transiently lost during cell division in the neural keel but is re-established as daughter cells reintegrate into the neuroepithelium. Loss of zebrafish Vangl2 (in trilobite mutants) abolishes the polarization of neural keel cells, disrupts re-intercalation of daughter cells into the neuroepithelium, and results in ectopic neural progenitor accumulations and NTDs. Remarkably, blocking cell division leads to rescue of trilobite neural tube morphogenesis despite persistent defects in convergence and extension. These results reveal a function for PCP signalling in coupling cell division and morphogenesis at neurulation and indicate a previously unrecognized mechanism that might underlie NTDs.
CD25+CD4+ regulatory T cells in normal animals are engaged in the maintenance of immunological self-tolerance. We show here that glucocorticoid-induced tumor necrosis factor receptor family–related gene (GITR, also known as TNFRSF18)—a member of the tumor necrosis factor–nerve growth factor (TNF-NGF) receptor gene superfamily—is predominantly expressed on CD25+CD4+ T cells and on CD25+CD4+CD8− thymocytes in normal naïve mice. We found that stimulation of GITR abrogated CD25+CD4+ T cell–mediated suppression. In addition, removal of GITR-expressing T cells or administration of a monoclonal antibody to GITR produced organ-specific autoimmune disease in otherwise normal mice. Thus, GITR plays a key role in dominant immunological self-tolerance maintained by CD25+CD4+ regulatory T cells and could be a suitable molecular target for preventing or treating autoimmune disease.
The involvement of the immune system in the response to tissue injury has raised the possibility that it might influence tissue, organ or appendage regeneration following injury. One hypothesis that has been discussed is that inflammatory aspects may preclude the occurrence of regeneration, but there is also evidence for more positive roles of immune components. The vertebrate eye is an immunoprivileged site where inflammatory aspects are inhibited by several immunomodulatory mechanisms. In various newt species the ocular tissues such as the lens are regenerative and it has recently been shown that the response to local injury of the lens involves activation of antigen-presenting cells which traffic to the spleen and return to displace and engulf the lens, thereby inducing regeneration from the dorsal iris. The activation of thrombin from prothrombin in the dorsal iris is one aspect of the injury response that is important in the initiation of regeneration. The possible relationships between the immune response and the regenerative response are considered with respect to phylogenetic variation of regeneration in general, and lens regeneration in particular.
Neurofibromatosis type 1 (NF1) is a prevalent genetic disorder that affects growth properties of neural-crest-derived cell populations. In addition, approximately one-half of NF1 patients exhibit learning disabilities. To characterize NF1 function both in vitro and in vivo, we circumvent the embryonic lethality of NF1 null mouse embryos by generating a conditional mutation in the NF1 gene using Cre/loxP technology. Introduction of a Synapsin I promoter driven Cre transgenic mouse strain into the conditional NF1 background has ablated NF1 function in most differentiated neuronal populations. These mice have abnormal development of the cerebral cortex, which suggests that NF1 has an indispensable role in this aspect of CNS development. Furthermore, although they are tumor free, these mice display extensive astrogliosis in the absence of conspicuous neurodegeneration or microgliosis. These results indicate that NF1-deficient neurons are capable of inducing reactive astrogliosis via a non-cell autonomous mechanism.
Neutrophil extracellular traps (NETs) are released as neutrophils die in vitro in a process requiring hours, leaving a temporal gap that invasive microbes may exploit. Neutrophils capable of migration and phagocytosis while undergoing NETosis have not been documented. During Gram-positive skin infections, we directly visualized live polymorphonuclear cells (PMNs) in vivo rapidly releasing NETs, which prevented systemic bacterial dissemination. NETosis occurred during crawling, thereby casting large areas of NETs. NET-releasing PMNs developed diffuse decondensed nuclei, ultimately becoming devoid of DNA. Cells with abnormal nuclei showed unusual crawling behavior highlighted by erratic pseudopods and hyperpolarization consistent with the nucleus being a fulcrum for crawling. A requirement for both Toll-like receptor 2 and complement-mediated opsonization tightly regulated NET release. Additionally, live human PMNs injected into mouse skin developed decondensed nuclei and formed NETS in vivo, and intact anuclear neutrophils were abundant in Gram-positive human abscesses. Therefore early in infection NETosis involves neutrophils that do not undergo lysis and retain the ability to multitask.
Zebrafish maintain a greater capacity than mammals for central nervous system repair after injury. Understanding differences in regenerative responses between different vertebrate species may shed light on mechanisms to improve repair in humans. Quinolinic acid is an excitotoxin that has been used to induce brain injury in rodents for modeling Huntington's disease and stroke. When injected into the adult rodent striatum, this toxin stimulates subventricular zone neurogenesis and neuroblast migration to injury. However, most new neurons fail to survive and lesion repair is minimal. We used quinolinic acid to lesion the adult zebrafish telencephalon to study reparative processes. We also used conditional transgenic lineage mapping of adult radial glial stem cells to explore survival and integration of neurons generated after injury. Telencephalic lesioning with quinolinic acid, and to a lesser extent vehicle injection, produced cell death, microglial infiltration, increased cell proliferation, and enhanced neurogenesis in the injured hemisphere. Lesion repair was more complete with quinolinic acid injection than after vehicle injection. Fate mapping of her4-expressing radial glia showed injury-induced expansion of radial glial stem cells that gave rise to neurons which migrated to injury, survived at least 8 weeks and formed long-distance projections that crossed the anterior commissure and synapsed in the contralateral hemisphere. These findings suggest that quinolinic acid lesioning of the zebrafish brain stimulates adult neural stem cells to produce robust regeneration with long-distance integration of new neurons. This model should prove useful for elucidating reparative mechanisms that can be applied to restorative therapies for mammalian brain injury.
Severe quantitative and qualitative brown adipocyte defects are common in obesity. To investigate whether aberrant expression of tumor necrosis factor alpha (TNF-alpha) in obesity is involved in functional brown fat atrophy, we have studied genetically obese (ob/ob) mice with targeted null mutations in the genes encoding the two TNF receptors. The absence of both TNF receptors or p55 receptor alone resulted in a significant reduction in brown adipocyte apoptosis and an increase in beta(3)-adrenoreceptor and uncoupling protein-1 expression in obese mice. Increased numbers of multilocular functionally active brown adipocytes, and improved thermoregulation was also observed in obese animals lacking TNF-alpha function. These results indicate that TNF-alpha plays an important role in multiple aspects of brown adipose tissue biology and mediates the abnormalities that occur at this site in obesity.
Autoantibodies to DNA and histones (chromatin) are the defining antigen specificity in systemic lupus erythematosus (SLE) and related musculoskeletal disorders but the mechanisms responsible for their induction remain mysterious. That situation rapidly changed once neutrophil extracellular chromatin traps (NETs) were discovered and observed to play a conserved role in innate immune responses to a broad variety of microbial pathogens. At the center of an infectious process, neutrophils exert various antimicrobial defenses, including the release of nuclear chromatin into the extracellular space. The externalized NETs, a complex meshwork of nuclear chromatin and antimicrobial proteins, serve to immobilize and degrade microbial pathogens. Here, we critically evaluate the evidence supporting NETs versus apoptotic bodies as a source for nuclear antigens in autoimmunity. We also discuss the possibility that NET chromatin forms an essential component of immune deposits in the pathogenesis of glomerulonephritis in SLE and other autoimmune immune complex diseases.
NADPH oxidase is a critical regulator of both antimicrobial host defense and inflammation. Activated in nature by microbes and microbial-derived products, the phagocyte NADPH oxidase is rapidly assembled, and generates reactive oxidant intermediates (ROIs) in response to infectious threat. Chronic granulomatous disease (CGD) is an inherited disorder of the NADPH oxidase characterized by recurrent and severe bacterial and fungal infections, and pathology related to excessive inflammation. Studies in CGD patients and CGD mouse models indicate that NADPH oxidase plays a key role in modulating inflammation and injury that is distinct from its antimicrobial function. The mechanisms by which NADPH oxidase mediates killing of pathogens and regulation of inflammation have broad relevance to our understanding of normal physiological immune responses and pathological states, such as acute lung injury and bacterial or fungal infections.
Lymphocytes provide optimal responses against pathogens with minimal inflammatory pathology. However, the intrinsic mechanisms regulating these responses are unknown. Here, we report that deletion of both transcription factors Egr2 and Egr3 in lymphocytes resulted in a lethal autoimmune syndrome with excessive serum proinflammatory cytokines but also impaired antigen receptor-induced proliferation of B and T cells. Egr2- and Egr3-defective B and T cells had hyperactive signal transducer and activator of transcription-1 (STAT1) and STAT3 while antigen receptor-induced activation of transcription factor AP-1 was severely impaired. We discovered that Egr2 and/or Egr3 directly induced expression of suppressor of cytokine signaling-1 (SOCS1) and SOCS3, inhibitors of STAT1 and STAT3, and also blocked the function of Batf, an AP-1 inhibitor, in B and T cells. Thus, Egr2 and Egr3 regulate B and T cell function in adaptive immune responses and homeostasis by promoting antigen receptor signaling and controlling inflammation.
Neutrophil extracellular traps (NETs) are implicated in autoimmunity, but how they are generated and their roles in sterile inflammation remain unclear. Ribonucleoprotein immune complexes (RNP ICs), inducers of NETosis, require mitochondrial reactive oxygen species (ROS) for maximal NET stimulation. After RNP IC stimulation of neutrophils, mitochondria become hypopolarized and translocate to the cell surface. Extracellular release of oxidized mitochondrial DNA is proinflammatory in vitro, and when this DNA is injected into mice, it stimulates type I interferon (IFN) signaling through a pathway dependent on the DNA sensor STING. Mitochondrial ROS are also necessary for spontaneous NETosis of low-density granulocytes from individuals with systemic lupus erythematosus. This was also observed in individuals with chronic granulomatous disease, who lack NADPH oxidase activity but still develop autoimmunity and type I IFN signatures. Mitochondrial ROS inhibition in vivo reduces disease severity and type I IFN responses in a mouse model of lupus. Together, these findings highlight a role for mitochondria in the generation not only of NETs but also of pro-inflammatory oxidized mitochondrial DNA in autoimmune diseases.
Neutrophil extracellular traps (NETs) represent extracellular structures able to bind and kill microorganisms. It is believed that they are generated by neutrophils undergoing cell death, allowing these dying or dead cells to kill microbes. We show that, following priming with granulocyte/macrophage colony-stimulating factor (GM-CSF) and subsequent short-term toll-like receptor 4 (TLR4) or complement factor 5a (C5a) receptor stimulation, viable neutrophils are able to generate NETs. Strikingly, NETs formed by living cells contain mitochondrial, but no nuclear, DNA. Pharmacological or genetic approaches to block reactive oxygen species (ROS) production suggested that NET formation is ROS dependent. Moreover, neutrophil populations stimulated with GM-CSF and C5a showed increased survival compared with resting neutrophils, which did not generate NETs. In conclusion, mitochondrial DNA release by neutrophils and NET formation do not require neutrophil death and do also not limit the lifespan of these cells.
We developed a novel mouse model of malignant pleural effusion (MPE) by injecting Lewis lung cancer (LLC) cells directly into the pleural space of syngeneic C57B/6 mice. The pleural effusions in this model share common cellular and biochemical features with human MPEs. Implantation and growth of pleural tumors triggers a host inflammatory response characterized by a mixed inflammatory cell influx into the pleural fluid. LLC cells exhibited high basal nuclear factor (NF)-κB activity in vitro and in vivo, which we used to drive expression of a NF-κB–dependent green fluorescent protein-firefly luciferase fusion reporter construct. NF-κB–dependent reporter expression allowed intravital tracing of pleural tumors. Inhibition of NF-κB in LLC cells did not affect cell viability in culture; however, injection of LLC cells expressing a dominant NF-κB inhibitor resulted in decreased tumor burden, decreased pleural effusion volume, and decreased pleural effusion TNF-α levels. These studies indicate that tumor NF-κB a...