Studies Of Toll-like Receptors Research Articles

TRAF3 regulation of proximal TLR signaling in B cells.

Toll-like receptors are pattern recognition receptors that bridge the innate and adaptive immune responses and are critical for host defense. Most studies of Toll-like receptors have focused upon their roles in myeloid cells. B lymphocytes express most Toll-like receptors and are responsive to Toll-like receptor ligands, yet Toll-like receptor-mediated signaling in B cells is relatively understudied. This is an important knowledge gap, as Toll-like receptor functions can be cell type specific. In striking contrast to myeloid cells, TRAF3 inhibits TLR-mediated functions in B cells. TRAF3-deficient B cells display enhanced IRF3 and NFκB activation, cytokine production, immunoglobulin isotype switching, and antibody production in response to Toll-like receptors 3, 4, 7, and 9. Here, we address the question of how TRAF3 impacts initial B-cell Toll-like receptor signals to regulate downstream activation. We found that TRAF3 in B cells associated with proximal Toll-like receptor 4 and 7 signaling proteins, including MyD88, TRAF6, and the tyrosine kinase Syk. In the absence of TRAF3, TRAF6 showed a greater association with several Toll-like receptor signaling proteins, suggesting that TRAF3 may inhibit TRAF6 access to Toll-like receptor signaling complexes and thus early Toll-like receptor signaling. In addition, our results highlight a key role for Syk in Toll-like receptor signaling in B cells. In the absence of TRAF3, Syk activation was enhanced in response to ligands for Toll-like receptors 4 and 7, and Syk inhibition reduced downstream Toll-like receptor-mediated NFκB activation and proinflammatory cytokine production. This study reveals multiple mechanisms by which TRAF3 serves as a key negative regulator of early Toll-like receptor signaling events in B cells.

Use of Fluorescent Chemical Probes in the Study of Toll-like Receptors (TLRs) Trafficking.

Fluorescent chemical probes are used nowadays as a chemical resource to study the physiology and pharmacology of several important endogenous receptors. Different fluorescent groups have been coupled with known ligands of these receptors, allowing the visualization of their localization and trafficking. One of the most important molecular players of innate immunity and inflammation are the Toll-Like Receptors (TLRs). These Pattern-Recognition Receptors (PRR) have as natural ligands microbial-derived pathogen-associated molecular patterns (PAMPs) and also endogenous molecules called danger-associated molecular patterns (DAMPs). These ligands activate TLRs to start a response that will determine the host's protection and overall cell survival but can also lead to chronic inflammation and autoimmune syndromes. TLRs action is tightly related to their subcellular localization and trafficking. Understanding this trafficking phenomenon can enlighten critical molecularpathways that might allow to decipher the causes of different diseases. In this chapter, the study of function, localization and trafficking of TLRs through the use of chemical probes will be discussed. Furthermore, an example protocol of the use of fluorescent chemical probes to study TLR4 trafficking using high-content analysis will be described.

Macrophage infection, activation, and histopathological findings in ebolavirus infection.

Macrophages contribute to Ebola virus disease through their susceptibility to direct infection, their multi-faceted response to ebolaviruses, and their association with pathological findings in tissues throughout the body. Viral attachment and entry factors, as well as the more recently described influence of cell polarization, shape macrophage susceptibility to direct infection. Moreover, the study of Toll-like receptor 4 and the RIG-I-like receptor pathway in the macrophage response to ebolaviruses highlight important immune signaling pathways contributing to the breadth of macrophage responses. Lastly, the deep histopathological catalogue of macrophage involvement across numerous tissues during infection has been enriched by descriptions of tissues involved in sequelae following acute infection, including: the eye, joints, and the nervous system. Building upon this knowledge base, future opportunities include characterization of macrophage phenotypes beneficial or deleterious to survival, delineation of the specific roles macrophages play in pathological lesion development in affected tissues, and the creation of macrophage-specific therapeutics enhancing the beneficial activities and reducing the deleterious contributions of macrophages to the outcome of Ebola virus disease.

Structural and Evolutionary Adaptation of NOD-Like Receptors in Birds.

NOD-like receptors (NLRs) are intracellular sensors of the innate immune system that recognize intracellular pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs). Little information exists regarding the incidence of positive selection in the evolution of NLRs of birds or the structural differences between bird and mammal NLRs. Evidence of positive selection was identified in four avian NLRs (NOD1, NLRC3, NLRC5, and NLRP3) using the maximum likelihood approach. These NLRs are under different selection pressures which is indicative of different evolution patterns. Analysis of these NLRs showed a lower percentage of codons under positive selection in the LRR domain than seen in the studies of Toll-like receptors (TLRs), suggesting that the LRR domain evolves differently between NLRs and TLRs. Modeling of human, chicken, mammalian, and avian ancestral NLRs revealed the existence of variable evolution patterns in protein structure that may be adaptively driven.

Study of Toll-like Receptor 3 Gene Polymorphism as a Novel Risk Factor for HCV-related Hepatocellular Carcinoma in Egypt.

Hepatocellular carcinoma (HCC) is a highly aggressive cancer with few treatment options. Toll-like receptor 3 (TLR3) plays a key role in innate immunity and may affect the development of cancers. This study aimed to investigate the association between TLR3 gene polymorphism and HCV-related hepatocellular carcinoma in Egypt. This work was conducted on 70 individuals; fifty HCV cirrhotic patients were included in two groups; with HCC (30 patients) and without HCC (20 patients) compared with a group of 20 apparently healthy controls. All of the studied individuals underwent clinical-laboratory evaluation. TLR3 gene single-nucleotide polymorphism (SNP) (+1234C/T) was tested by polymerase chain reaction- restriction fragment length polymorphism. This study reported that the prevalence of TLR3 +1234TT genotype was significantly increased in cirrhotic patients with HCC than without HCC, while it was not detected at all among the controls. When analyzing the TLR3 SNP +1234C/T with different clinical parameters in HCC patients, there was a significant association between+1234C/T SNP; namely TT genotype and each of the hepatic focal lesions᾽ number, size and the patients᾽ higher Okuda and BCLC stages. No association could be detected between TLR3 SNP and the age, sex, Child-Pugh grades, MELD score or AFP of the studied HCC cases. TLR3 gene SN P +1234C/T could be a novel risk factor for the HCV-related HCC among the Egyptian population.

Иммунный ответ при инфекциях нижних мочевыводящих путей

Urinary tract infections are one of the most common and widespread infectious diseases. A certain role in etiopathogenesis may play genetic predisposition, as well as a decrease in antiadhesive properties and an increase in urothelium permeability due to incompetence of bladder glycosaminoglycan layer. The prevalence of infectious diseases increases significantly with age, as well as in patients with chronic diseases. The introduction of modern biotechnology has allowed clinicians to greatly expand therapeutic armamentarium, while having a number of advantages, including minimal frequency of complications and adverse events, the possibility for long-term use, accessibility, and etc. Priority research areas include the study of toll-like receptors, which are transmembrane proteins that provide pathogen recognition and activate the immune response. The role of these receptors in the development of the immune response to urinary tract infections was evaluated in our study, which allows to predict the course of the disease and to increase treatment efficiency.

Expression of Toll-like receptors in emotiogenic structures of rat brain is changed under longterm alcohol consumption and ethanol withdrawal

Recent studies have provided strong evidence that long-term ethanol consumption leads to activation the mechanisms of neuroimmune signaling. Recently, much attention has been focused on the study of toll-like receptors (Toll-like receptors, TLRs), which play one of the key roles in the mechanisms of activation of the innate immune system in brain structures subsequently ethanol consumption. It is known that the activation of TLRs leads to the release of many proinflammatory cytokines with the resulting neuroinflammatory process. There are suggestions that TLRs may also be involved in the modulation of neurotransmitter systems of the brain, thereby contributing to the formation of pathological dependence on ethanol. The goal of our work was to study the level of expression the genes of TLRs (TLR3, TLR4, TLR7) and pro-inflammatory cytokine genes (IL-1β, CCL2) in the rat brain (amygdala, hippocampus, medial entorhinal cortex, striatum) under conditions of prolonged alcoholization and on different periods of alcohol withdrawal, which was previously not studied by researchers. Prolonged alcoholization of rats with ethanol did not lead to changes in levels mRNA of TLRs in the studied structures of the rat brain, with the exception of a small increase in the level of TLR3 mRNA in the hippocampus of prolonged alcoholized rats and a slight increase in the level of TLR3 mRNA in mEC. However, gene expression of TLRs undergoes changes in all the structures of the rat brain studied by us at different periods of alcohol withdrawal. The increased level of expression of both TLRs and proinflammatory genes in the period of alcohol withdrawal in the rat brain hippocampus deserves special attention, which indicates the presence of a persistent neuroinflammatory process in this brain structure in the period of alcohol withdrawal, which is probably supported with the participation of TLR-dependent signaling. The study of the mechanisms of inflammatory process activation by TLR-dependent signaling in different brain structures can open new targets for drug exposure. Such drugs can be used in the treatment of alcoholism.

ROLE OF TOLL-LIKE RECEPTORS IN LICHEN PLANUS PATHOGENESIS

Among diseases of the oral mucosa, lichen planus (LP) is up to 13%. Over the past decade, the number of patients with this dermatosis has doubled. Currently, the etiopathogenetic factor of LP development remains unclear, but there are many theories of the development of this disease. However, in the literature there is no description of a common pathogenetic link. In connection with th e above, the authors believe that these theories can be combined with new scientific facts and ideas about the barrier role of innate, and in particular, mucosal immunity. The review article describes the role of mucosal immunity of mucous membranes - toll-like receptors (TLR), describes the mechanism of activation of the immune system through TLR2 and TLR4, shows the relationship of immune inflammation triggers - the reaction of food intolerance, factors that contribute to the development of hypersensitivity in the pathogenesis of LP. The mechanism is presented for the presentation of autoantigens to immunocompetent cells with the participation of heat shock proteins. The prospects for further study of TLR with the aim of increasing the effectiveness of the treatment of LP are presented.

Toll-Like Receptors in Peripheral Blood Cells of Cosmonauts after Long-term Missions on Board the International Space Station

Studies of Toll-like receptors (TLR) in 20 cosmonauts, members of long-term (124- to 199-day) missions on board the International Space Station showed changes in the relative and absolute counts of peripheral blood monocytes with TLR2, TLR4, and TLR6 on their surface, expression of genes TLR2 and TLR6, as well as genes of molecules involved in the TLR signaling pathway and TLR-related NF-κB-, JNK/p38- and IRF pathways on the day of return to Earth. The observed changes displayed individual variability.

Study of toll-like receptor 4 in type 2 diabetic patients with or without nephropathy

Objective The aim of this work was to study the role of toll-like receptor 4 (TLR4) in the development of type 2 diabetes mellitus (T2DM) as well as its relation to the occurrence of diabetic nephropathy. Background Chronic kidney disease is one of the major complications of T2DM and is the leading cause of end-stage renal disease. There is growing evidence indicating that chronic low-grade inflammatory response is a recognized factor in the pathogenesis and progression of diabetic renal injury. Patients and methods A total of 50 T2DM patients were divided into three groups according to urinary albumin excretion: those with normoalbuminuria, those with microalbuminuria, and those with macroalbuminuria. In addition, 10 apparently healthy individuals were included as a control group. Fasting blood glucose, glycated hemoglobin, blood urea, and serum creatinine were measured in all patients. Urinary albumin excretion was measured using a morning spot urine sample and the urinary albumin/creatinine ratio was calculated. Quantification of CD14 and TLR4 expression on monocyte subsets was performed by means of flow cytometry. Results Levels of CD14 were found to be significantly increased in patients with macroalbuminuria, whereas TLR4 levels were increased in T2DM patients, with further elevation in patients with macroalbuminuria. Both markers showed significant positive correlations with the duration of diabetes, glycated hemoglobin, serum creatinine, and urinary albumin/creatinine ratio and significant negative correlations with estimated glomerular filtration rate. Multivariate regression analysis demonstrated that CD14 and TLR4 are independent predictors of the occurrence of microalbuminuria in T2DM patients. Conclusion TLR4 levels were higher in T2DM patients compared with normal individuals. These observations significantly add to the emerging role of TLRs in T2DM development. TLR4 was also found to correlate well with the severity of albuminuria in T2DM and to be a good predictor of microalbuminuria, suggesting its possible role in the pathogenesis and progression of diabetic nephropathy.

Inflammation and Heart Diseases: Role of Toll-Like Receptor Signaling

Aim of review: Heart diseases such as septic cardiomyopathy, ischemic myocardial injury and acute myocarditis pose significant perioperative risk to surgical patients and present challenges to anesthesiologists. Myocardial inflammation is a common theme of these diseases and plays an important role in their pathogeneses. Toll-like receptors (TLRs) are an important part of the innate immune system. The aim of this article is to provide a brief review on the major landmark studies of TLRs and their signaling, the complex and critical role of TLRs in severe sepsis, ischemic myocardial injury, and myocarditis. The article intends to cover animal studies defining the molecular mechanisms by which TLR signaling contributes to the pathogenesis of these heart diseases as well as the recent clinical trials targeting TLR for sepsis intervention.Method: Literatures were searched via PubMed with the key words TLRs, sepsis, myocardial ischemia, and myocarditis. A few previously published review articles in the relevant fields were referenced.Recent findings: TLRs detect invading pathogens through the pathogen-associated molecular pattern (PAMP) recognition and play an essential role in the host defense. TLRs can also sense endogenous molecules with the danger-associated molecular pattern (DAMP), such as heat shock proteins (HSPs), high mobility group 1 (HMGB-1) and extracellular RNA, which are produced under various injurious conditions. Studies in the past decade have clearly established the critical role of TLR signaling in mediating cardiac inflammation in the context of severe sepsis, myocardial ischemia-reperfusion injury and acute myocarditis. A variety of microbial and non-microbial TLR ligands have been identified under these critical conditions. These ligands act through TLRs and elicit potent biochemical and inflammatory responses. By mediating the complex cardiac as well as systemic inflammation, either beneficial or deleterious in nature, TLRs play a pivotal role in the development of these cardiac diseases. Recent TLR4 antagonist (eritoran) Phase I-III clinical trials represent the latest effort targeting TLR signaling for sepsis therapeutics.Summary: Studies of the past decade have firmly established the role of TLR signaling in cardiac inflammation and dysfunction during severe sepsis, ischemic myocardial injury, and acute myocarditis. Understanding the complex cellular and molecular pathways by which TLR signaling controls myocardial inflammation and injury provides insight into the mechanisms of these cardiac diseases and will impact on how we diagnose and treat these critical conditions in the future. Citation: Wei Chao. Inflammation and heart diseases: role of toll-like receptor signaling. J Anesth Perioper Med 2014; 1: 104-17. doi: 10.24015/JAPM.2014.0016This is an open-access article, published by Evidence Based Communications (EBC). This work is licensed under the Creative Commons Attribution 4.0 International License, which permits unrestricted use, distribution, and reproduction in any medium or format for any lawful purpose. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

The role of Toll-like Receptors in innate immunity and infectious diseases of teleost

The immune defence mechanism depends mainly on germ-line encoded pattern-recognition receptors (PRRs). These PRRs respond to many exogenous pathogens and/or endogenous serious signals, by recognizing some highly conserved structures such as pathogen-associated molecular patterns (PAMPs) and danger/damage associated molecular patterns (DAMPs). Till date, the most studied PRRs are Toll-like receptors (TLRs). Upon activation of TLRs, there is production of inflammatory cytokines and type I interferons (IFNs) via myeloid differentiation primary response gene 88 (MyD88)-dependent or -independent signalling, respectively, modulating innate and adaptive immunity, as well as inflammatory responses. In fish species studied to date, there are more than 17 TLRs that are identified with some showing homology to mammals, and some are unique for teleost. In the present review, more light are to be shed on the classification, structure and specific ligands of TLRs, with focuses on their signal pathways and different biological activities. Studies of TLRs and their role in the innate immune will potentially have implications for the prevention and treatment of fish diseases.

Study of toll-like receptor 7 expression and interferon α in Egyptian patients with chronic hepatitis C Infection and Hepatocellular Carcinoma

BackgroundHepatitis C virus is considered to be one of the most important devastating causes of chronic hepatitis, cirrhosis, and hepatic cellular carcinoma. Toll-like receptor 7 (TLR7) is a pathogen-recognition receptor that is expressed on innate immune cells. It recognizes viral RNA which induces its activation with a subsequent increase in IFN-α transcription. It has been postulated that HCV may cause down regulation of these receptors as one of immune evading mechanisms that participate in viral persistence. The aim of the workWas to investigate the expression of TLR7 in peripheral blood of patients with chronic HCV infections and patients with HCC, comparing it with normal individuals, and correlating it with both serum levels of IFN-α and viral load. ResultsThe results of this study showed a significant decrease in TLR7 expression in patients with chronic HCV and no detection at all in patients with HCC, in addition a significant negative correlation was observed between levels of TLR7expression and interferon α when compared to viral load. ConclusionDown regulation of TLR7 expression in HCV and HCC patients may contribute to the decrease of IFN-α and increase in viral load. These results raise the possibility that by targeting TLR7 with high affinity pharmacological stimulants may be able to control HCV infection by induction of IFN-α and direct activation of antiviral mechanisms in hepatocytes. Additionally, they provide insight about the potential use of TLR7 as a new set of molecular markers for prognosis and outcomes of chronic HCV infection and HCC.

Toll-like receptors in the depressed and suicide brain

Abnormalities of the immune function in depression and suicide are based in part on the observation of increased levels of proinflammatory cytokines in the serum and postmortem brain of depressed and suicidal patients. We have examined if abnormalities of the innate immune receptors, known as Toll-like receptors (TLRs), in the brain are associated with depression and suicide, since the activation of these receptors results in production of cytokines. Of all the TLRs shown to be present in humans, TLR3 and TLR4 appear to be unique and important in brain function. We have determined the protein (by ELISA method) and mRNA expression (using qPCR) of TLR3 and TLR4 in the postmortem brain (dorsolateral prefrontal cortex [DLPFC]) of 22 depressed suicide victims, 11 non-depressed suicide victims, 12 depressed non-suicide subjects and 20 normal control subjects. We found that the mRNA expression of TLR3 and TLR4 was significantly increased in DLPFC of depressed suicide victims and in depressed non-suicide subjects, compared with controls. However, the protein expression of TLR3 and TLR4 was significantly increased in depressed suicide victims, but not in depressed non-suicide subjects compared with controls. The observed abnormalities of proinflammatory cytokines in the brain of suicide victims may be related to an abnormality of TLR3 and TLR4 over-expression. To our knowledge, this is the first study of TLRs in the brain of psychiatric subjects.

Immunohistochemical study of toll-like receptors 1 and 2 expression in cutaneous lichen planus lesions

Lichen planus (LP) is a chronic inflammatory, T cell-mediated autoimmune skin disease. Innate immunity could explain the interplay between environmental triggers and the autoimmune cascade leading to disease development. Toll-like receptors (TLRs) are important components of the innate immune system, with no previous evaluation of TLRs 1 and 2 in cutaneous LP. This work aims to investigate TLRs 1 and 2 expression in cutaneous LP. This case-control study included 30 patients with LP and 15 healthy controls. Biopsies from the patients' lesional skin and from the controls' normal skin were examined immunohistochemically for TLR 1 and 2 expression. A significant re-localization was found in TLR1 expression with a higher percentage of basal and a significantly lower percentage of homogenous epidermal expression in patients (73.3 and 0%, respectively) compared with controls (13.3 and 73.3%, respectively) (P<0.001). TLR2 showed a significantly higher percentage of epidermal expression (more in the upper spinous layer) and significantly lower percentage of epidermal but more basal expression in patients (66.6 and 10%, respectively) compared with controls (0 and 73.3%, respectively) (P<0.001). The median (IQR) of TLR1 [1 (0.75-1)] and TLR2 [1 (1-1)] staining score in patients was significantly lower than that of the controls [2 (1-2) and 1 (1-2), respectively] (P<0.05). This work thus shows a re-localization of TLR 1 and 2 expression sites with decreased grade of expression in LP lesions. Targeting TLR signaling is expected to be a novel treatment strategy for cutaneous LP.

Toll-Like Receptors of Deuterostome Invertebrates

Defensive systems against pathogens are responsible not only for survival or lifetime of an individual but also for the evolution of a species. Innate immunity is expected to be more important for invertebrates than mammals, given that adaptive immunity has not been acquired in the former. Toll-like receptors (TLRs) have been shown to play a crucial role in host defense of pathogenic microbes in innate immunity of mammals. Recent genome-wide analyses have suggested that TLR or their related genes are conserved in invertebrates. In particular, numerous TLR-related gene candidates were detected in deuterostome invertebrates, including a sea urchin (222 TLR-related gene candidates) and amphioxus (72 TLR-related gene candidates). Molecular phylogenetic analysis verified that most of sea urchin or amphioxus TLR candidates are paralogous, suggesting that these organisms expanded TLR-related genes in a species-specific manner. In contrast, another deuterostome invertebrate, the ascidian Ciona intestinalis, was found to possess only two TLR genes. Moreover, Ciona TLRs, Ci-TLR1 and Ci-TLR2, were shown to possess “hybrid” functionality of mammalian TLRs. Such functionality of Ci-TLRs could not be predicted by sequence comparison with vertebrate TLRs, indicating confounding evolutionary lineages of deuterostome invertebrate TLRs or their candidates. In this review article, we present recent advances in studies of TLRs or their candidates among deuterostome invertebrates, and provide insight into an evolutionary process of TLRs.

Toll-like receptors in innate immunity and infectious diseases

The protective ability of host defense system is largely dependent on germ-line encoded pattern-recognition receptors (PRRs). These PRRs respond to a variety of exogenous pathogens or endogenous danger signals, by recognizing some highly conserved structures such as pathogen-associated molecular patterns (PAMPs) and danger/damage associated molecular patterns (DAMPs). The most studied PRRs are Toll-like receptors (TLRs). Activation of TLRs triggers production of inflammatory cytokines and type I interferons (IFNs) via myeloid differentiation primary response gene 88 (MyD88)-dependent or -independent signaling respectively, thereby modulating innate and adaptive immunity, as well as inflammatory responses. This review introduces the classification, structure, and specific ligands of TLRs, and focuses on their signal pathways and biological activities, as well as clinical relevance. These studies of TLRs in the innate immune system have implications for the prevention and treatment of a variety of infectious diseases, including tuberculosis (TB), microbial keratitis, and hepatitis B and C.

Brain Death and Toll-Like Receptors in Lung Transplantation

Modern transplantation has relied greatly on the concept of brain death and the use of brain-dead donors. With the increased understanding of brain death-related pathophysiology, it is now clear that brain death itself can cause injury to the donor organs (1). A “storm” of catecholamines and cytokines accompanies brain death and leads to a generalized systemic inflammatory response. Yet, the exact mechanism for the brain death induced inflammatory responses remains to be elucidated. Key players of the inflammatory response (cytokines, chemokines, and other inflammatory mediators) are generated by the innate immune system after the recognition of molecular patterns deemed harmful to the host. The best studied example of pattern recognition receptors to date is the toll-like receptors (TLRs). Activation of TLRs may result in the activation of NF-κB and the subsequent release of proinflammatory cytokines and the induction of co-stimulatory molecules. Thus, TLRs can bridge innate and adaptive immune responses; certainly, something of interest to transplant clinicians. Initially believed of only as sensors of exogenous or pathogenic molecular patterns, there is now increasing evidence that TLRs can sense host tissue damage (2). Molecules typically confined to the intracellular space such as HMGB1, hyaluronan, and S100 have been found to be able to bind and activate TLRs. Tissue damage is an obligatory part of organ transplantation and thus TLRs likely play a role in the activation of inflammation and priming of the acute immune response after transplantation. In studies of TLRs within the context of transplantation, a reduction of ischemia-reperfusion injury in the lung (3), liver, and kidney as well as reduced antigen presenting cell activation in a skin transplantation model have been found. Living-donor kidneys express less HMGB1 than brain-dead donor kidneys in clinical kidney transplantation. Recipients of kidney grafts from donors with loss-of-function single nucleotide polymorphisms in TLR4, Asp299Gly, and Thr399Ile had superior immediate graft function and lower intragraft proinflammatory gene expression. Thus, TLRs seem to play a role in mediating donor organ injury, but until now the link between brain death and the function of TLRs has not been well studied in the lung transplant setting (4). Rostron et al., (5) in this issue of Transplantation, assess the donor TLR response to brain death using a rat model. Brain death was induced by the previously described method of balloon inflation in the epidural space, and TLR4 and TLR2/6 desensitization was induced by 5 days of TLR agonist treatment and then observed for 3 days before brain death induction. After brain death induction, rats with prior TLR desensitization showed a better preserved mean arterial pressure after brain death, decreased cytokine expression, and reduced expression of CD11b/CD18 adhesion molecules by neutrophils in the blood (5). This is an important first look at the effect of donor brain death on the activation of donor organ TLRs. Their data suggest that TLRs can mediate organ dysfunction after brain death, yet the mechanism remains elusive. Further study with more targeted TLR pathway knockouts may help clarify the mechanism. Recently, the parasympathetic nervous system has been shown to be involved in modulation of the innate immune system. Could loss of vagus nerve stimulation cause HMGB1 secretion? What is the ligand released during brain death leading to TLR activation? Are these effects seen posttransplant? Fortunately, many of the tools needed to start to answer these questions are now available. A variety of TLR and TLR adaptor knockout mice have been generated. Moreover, lung transplantation in mice has now been reported. A better understanding of how this first injury of brain death can activate innate immunity will hopefully lead to reduced organ inflammation and priming of adaptive immunity in the recipient. Further study of this phenomenon is warranted.

Comparative Overview of Toll-Like Receptors in Lower Animals

Toll-like receptors (TLRs) have been shown to play a crucial role in host defense against pathogenic microbes in innate immunity in mammals. Recent genome-wide analyses have suggested that TLRs or related genes are conserved in the genome of non-mammalian organisms such as fishes, cyclostomes, ascidians, cephalochordates, sea urchins, and hydras. However, neither active forms nor functions of authentic invertebrate TLRs had been elucidated. Quite recently, we verified the structures, localization, ligand recognition, activities, and inflammatory cytokine production of two TLRs in the ascidian Ciona intestinalis, designated Ci-TLR1 and Ci-TLR2. Both Ci-TLRs possess a unique structural organization, with moderate sequence similarity to functionally characterized vertebrate TLRs, and are expressed predominantly in the stomach and intestine as well as in hemocytes. Unlike vertebrate TLRs, Ci-TLR1 and Ci-TLR2 are present in both the plasma membrane and endosomes. Furthermore, both Ci-TLR1 and Ci-TLR2 stimulate NF-kappaB induction in response to multiple pathogenic ligands that are differentially recognized by respective vertebrate TLRs. Pathogenic ligands that stimulate the Ci-TLRs also induce the expression of Ci-TNFalpha in the intestine and stomach, where the Ci-TLRs are abundantly expressed. These data reveal the conservation of the TLR-triggered innate immune system in C. intestinalis, and both common and unique biological and immunological functions of the Ci-TLRs. Based on the latest findings, we review recent advances in studies of TLRs or related receptors in fish, cyclostomes, deuterostome invertebrates, and hydra, and also the significance of studies of lower organism TLRs.

S.106. Studies of Toll-like Receptors 7 and 9 Antisense in a Preclinical Model of Colitis

S.106. Studies of Toll-like Receptors 7 and 9 Antisense in a Preclinical Model of Colitis