Mental health outcomes of encephalitis: An international web-based study.

BACKGROUND AND PURPOSE: Acute encephalitis is associated with psychiatric symptoms. Despite this, the extent of mental health problems following encephalitis has not been systematically reported. METHODS: We recruited adults who had been diagnosed with encephalitis of any aetiology to complete a web-based questionnaire. RESULTS: In total, 445 respondents from 31 countries (55.1% UK, 23.1% USA) responded. Infectious encephalitis constituted 65.4% of cases, autoimmune 29.7%. Mean age was 50.1 years, 65.8% were female, and median time since encephalitis diagnosis was 7 years. The most common self-reported psychiatric symptoms were anxiety (75.2%), sleep problems (64.4%), mood problems (62.2%), and unexpected crying (35.2%). Self-reported psychiatric diagnoses were common: anxiety (44.0%), depression (38.6%), panic disorder (15.7%), and posttraumatic stress disorder (PTSD; 21.3%). Severe mental illnesses such as psychosis (3.3%) and bipolar affective disorder (3.1%) were reported. Self-reported diagnosis rates were broadly consistent with results from the Psychiatric Diagnostic Screening Questionnaire. Many respondents also reported they had symptoms of anxiety (37.5%), depression (28.1%), PTSD (26.8%), or panic disorder (20.9%) that had not been diagnosed. Rates of psychiatric symptoms did not differ between autoimmune and infectious encephalitis. In total, 37.5% respondents had thought about suicide, and 4.4% had attempted suicide, since their encephalitis diagnosis. More than half of respondents (53.5%) reported they had no, or substandard, access to appropriate mental health care. High rates of sensory hypersensitivities (>75%) suggest a previously unreported association. CONCLUSIONS: This large international survey indicates that psychiatric symptoms following encephalitis are common and that mental health care provision may be inadequate. We highlight a need for proactive psychiatric input.

From Software to Hardware: A Case Series of Functional Neurological Symptoms and Cerebrovascular Disease.

OBJECTIVE: Neuroimaging studies have identified alterations in both brain structure and functional connectivity in patients with functional neurological disorder (FND). For many patients, FND emerges from physical precipitating events. Nevertheless, there are a limited number of case series in the literature that describe the clinical presentation and neuroimaging correlates of FND following cerebrovascular disease. METHODS: The authors collected data from two clinics in the United Kingdom on 14 cases of acute, improving, or delayed functional neurological symptoms following cerebrovascular events. RESULTS: Most patients had functional neurological symptoms that were localized to cerebrovascular lesions, and the lesions mapped onto regions known to be part of functional networks disrupted in FND, including the thalamus, anterior cingulate gyrus, insula, and temporoparietal junction. CONCLUSIONS: The findings demonstrate that structural lesions can lead to FND symptoms, possibly explained through changes in relevant mechanistic functional networks.

Effectiveness and Safety of Intravenous Medications for the Management of Acute Disturbance (Agitation and Other Escalating Behaviors): A Systematic Review of Prospective Interventional Studies.

Acute disturbance is a broad term referring to escalating behaviors secondary to a change in mental state, such as agitation, aggression, and violence. Available management options include de-escalation techniques and rapid tranquilization, mostly via parenteral formulations of medication. While the intramuscular route has been extensively studied in a range of clinical settings, the same cannot be said for intravenous (IV); this is despite potential benefits, including rapid absorption and complete bioavailability. This systematic review analyzed existing evidence for effectiveness and safety of IV medication for management of acute disturbances. It followed a preregistered protocol (PROSPERO identification CRD42020216456) and is reported following the guidelines set by Preferred Reporting Items for Systematic Review and Meta-Analysis. APA PsycINFO, MEDLINE, and EMBASE databases were searched for eligible interventional studies up until May 30th, 2023. Data analysis was limited to narrative synthesis since primary outcome measures varied significantly. Results showed mixed but positive results for the effectiveness of IV dexmedetomidine, lorazepam, droperidol, and olanzapine. Evidence was more limited for IV haloperidol, ketamine, midazolam, chlorpromazine, and valproate. There was no eligible data on the use of IV clonazepam, clonidine, diazepam, diphenhydramine, propranolol, ziprasidone, fluphenazine, carbamazepine, or promethazine. Most studies reported favorable adverse event profiles, though they are unlikely to have been sufficiently powered to pick up rare serious events. In most cases, evidence was of low or mixed quality, accentuating the need for further standardized, large-scale, multi-arm randomized controlled trials with homogeneous outcome measures. Overall, this review suggests that IV medications may offer an effective alternative parenteral route of administration in acute disturbance, particularly in general hospital settings.

Illness perceptions, experiences of stigma and engagement in functional neurological disorder (FND): exploring the role of multidisciplinary group education sessions.

Background: A critical first step in managing functional neurological disorder (FND) is a positive diagnosis and clear explanation using an understandable illness model. Multidisciplinary group education sessions are one way to achieve this, with some evidence they improve understanding, confidence in diagnosis and outcomes with further treatment. In many conditions, illness perceptions and stigma affect distress, functioning, quality of life and engagement. Exploring relationships between these factors could lead to deeper understanding of the impact of education. Methods: Questionnaires assessing illness perceptions, quality of life, mood, anxiety, comorbidities, treatment engagement and stigma (both experienced and anticipated) were completed before, immediately and 1 month after a multidisciplinary online group education session for FND at a regional neurosciences centre. Free-text data on causal attributions and needs were also collected. Results: 166 patients attended online education sessions from January 2022 to July 2023; 61 (37%) completed presession surveys, 42 (25%) completed postsession and 35 (21%) completed 1 month postsession surveys. Patients reported multiple comorbidities, poor quality of life, functioning and high levels of stigma. Illness perception scores indicated FND as threatening, mysterious and unpredictable, with low personal or treatment control over symptoms. Illness coherence/understanding (mean difference 2.27, p<0.01, 95% CI 1.22 to 4.23) and engagement (mean difference 2.42, p<0.01, 95% CI 0.46 to 4.36) increased after the session. There were no significant changes in stigma, distress, sense of control or anticipated discrimination. Free-text analysis revealed stress and trauma as the most common causal attributions, followed by physical illnesses. Patients requested personalised formulations, practical disability advice, help with explaining the condition to others (eg, employers), peer support and treatment. Conclusion: Multidisciplinary group FND education sessions potentially improve patient understanding and engagement. Clinicians should consider the possible benefits of personalised formulations and linking to practical and peer support. Further work assessing illness perceptions is needed, such as adapting measures for FND.

Impairment of adenosine A3 receptor activity disrupts neutrophil migratory capacity and impacts innate immune function in vivo.

Adenosine possesses potent anti-inflammatory properties which are partly mediated by G(i) -coupled adenosine A3 receptors (A3Rs). A3R agonists have shown clinical benefit in a number of inflammatory conditions although some studies in A3R-deficient mice suggest a pro-inflammatory role. We hypothesised that, in addition to cell signalling effects, A3R compounds might inhibit neutrophil chemotaxis by disrupting the purinergic feedback loop controlling leukocyte migration. Human neutrophil activation triggered rapid upregulation of surface A3R expression which was disrupted by pre-treatment with either agonist (Cl-IB-MECA) or antagonist (MRS1220). Both compounds reduced migration velocity and neutrophil transmigration capacity without impacting the response to chemokines per se. Similar effects were observed in murine neutrophils, while cells from A3R-deficient mice displayed a constitutively impaired migratory phenotype indicating compound-induced desensitisation and genetic ablation had the same functional outcome. In a dextran sodium sulphate-induced colitis model, A3R-deficient mice exhibited reduced colon pathology and decreased tissue myeloperoxidase levels at day 8 - consistent with reduced neutrophil recruitment. However, A3R-deficient mice were unable to resolve the dextran sodium sulphate-induced inflammation and had elevated numbers of tissue-associated bacteria by day 21. Our data indicate that A3Rs play a role in neutrophil migration and disrupting this function has the potential to adversely affect innate immune responses.

William Butler (1535-1618): A biography of a singular physician.

William Butler (1535-1618) was a man without a medical degree who was styled as the 'greatest physician of his age'. He was famous in his lifetime, and in the latter stages of his career was involved with the royal court, attending to King James I and his son, Prince Henry. Butler was an empiricist who practiced confidently and compassionately in a time of limited medical understanding. He was also a man of contradictions: he was loved and respected by his contemporaries but could be cantankerous and obtuse; he was anti-establishment, complaining bitterly about the restrictive monopolisation of medicine sustained by the Royal College of Physicians, but advanced his career via connections within the aristocracy; he sometimes practiced orthodox Galenic medicine, but was at times highly unconventional in his treatments. Posthumously, despite some compelling historical studies of Butler, there has been a great deal of embellishment of his behaviour and practice. This biography draws from Butler's own letters, contemporary writers and modern scholarly literature. It aims to arrange these sources into a verifiable narrative of this singular physician's life.

Expectancy in placebo-controlled trials of psychedelics: if so, so what?

Modern psychedelic research remains in an early phase, and the eventual introduction of psychedelics into clinical practice remains in doubt. In this piece, we discuss the role of blinding and expectancy in psychedelic trials, and place this in a broader historical and contemporary context of blinding in trials across the rest of healthcare. We suggest that premature and uncritical promotion ('hype') of psychedelics as medicines is not only misleading, but also directly influences participant expectancy in ongoing psychedelic trials. We argue that although psychedelic trials are likely to significantly overestimate treatment effects by design due to unblinding and expectancy effects, this is not a unique situation. Placebo-controlled RCTs are not a perfect fit for all therapeutics, and problems in blinding should not automatically disqualify medications from licencing decisions. We suggest that simple practical measures may be (and indeed already are) taken in psychedelic trials to partially mitigate the effects of expectancy and unblinding, such as independent raters and active placebos. We briefly suggest other alternative trial methodologies which could be used to bolster RCT results, such as naturalistic studies. We conclude that the results of contemporary placebo-controlled RCTs of psychedelics should neither be dismissed due to imperfections in design, nor should early data be taken as firm evidence of effectiveness.

Human Induced Pluripotent Stem Cell-Derived Microglia-Like Cells Harboring TREM2 Missense Mutations Show Specific Deficits in Phagocytosis.

Dysfunction of microglia, the brain's immune cells, is linked to neurodegeneration. Homozygous missense mutations in TREM2 cause Nasu-Hakola disease (NHD), an early-onset dementia. To study the consequences of these TREM2 variants, we generated induced pluripotent stem cell-derived microglia-like cells (iPSC-MGLCs) from patients with NHD caused by homozygous T66M or W50C missense mutations. iPSC-MGLCs expressed microglial markers and secreted higher levels of TREM2 than primary macrophages. TREM2 expression and secretion were reduced in variant lines. LPS-mediated cytokine secretion was comparable between control and TREM2 variant iPSC-MGLCs, whereas survival was markedly reduced in cells harboring missense mutations when compared with controls. Furthermore, TREM2 missense mutations caused a marked impairment in the phagocytosis of apoptotic bodies, but not in Escherichia coli or zymosan substrates. Coupled with changes in apoptotic cell-induced cytokine release and migration, these data identify specific deficits in the ability of iPSC-MGLCs harboring TREM2 missense mutations to respond to specific pathogenic signals.

Muramyl dipeptide and toll-like receptor sensitivity in NOD2-associated Crohn's disease.

Both NOD2 (CARD15) alleles are mutated in roughly 15% of patients with Crohn's disease, but functional effects are unclear. We analysed the cytokine response of peripheral blood mononuclear cells to muramyl dipeptide (MDP), the ligand for NOD2. MDP induced little TNFalpha or interleukin 1beta, but strong interleukin-8 secretion. MDP also substantially upregulated secretion of TNFalpha and interleukin 1beta induced by toll-like receptor ligands. These effects were abolished by the most common Crohn's NOD2 double mutant genotypes at low nanomolar MDP concentrations, and provide the basis to develop a test of NOD2 functional deficiency. In Crohn's disease, there are defects in neutrophil recruitment driven by NOD2 and interleukin 8 and in cross talk between the NOD2 and toll-like receptor pathways, which suggests that the immune system fails to receive an early priming signal.

The Plant-Derived Chalcone 2,2',5'-Trihydroxychalcone Provides Neuroprotection against Toll-Like Receptor 4 Triggered Inflammation in Microglia.

Chalcones are plant metabolites with potential for therapeutic exploitation as antioxidant, anti-inflammatory, and antiproliferative agents. Here we explored the neuroprotective effects of 2,2',5'-trihydroxychalcone (225THC), a potent antioxidant with radical-scavenging properties. 225THC was found to be a potent inhibitor of apoptosis in stimulated primary rat neuronal cultures. This was likely mediated by an anti-inflammatory effect on microglial cells since 225THC inhibited LPS-stimulated TNF-α and IL-6 secretion from primary rat microglia and modulated the cytokine/chemokine profile of BV2 microglial cells. Additionally, 225THC inhibited LPS-evoked inducible nitric oxide synthase expression but did not influence endogenous superoxide generation. Microglial flow cytometric analyses indicated the 225THC treatment induced a shift from an M1-like phenotype to a more downregulated microglial profile. Taken together these data suggest that the chalcone 2,2',5'-trihydroxychalcone can modulate neuroinflammatory activation in brain-derived microglia and holds promise as a therapeutic in neuroinflammatory conditions.

Host genetics and environmental factors regulate ecological succession of the mouse colon tissue-associated microbiota.

BACKGROUND: The integration of host genetics, environmental triggers and the microbiota is a recognised factor in the pathogenesis of barrier function diseases such as IBD. In order to determine how these factors interact to regulate the host immune response and ecological succession of the colon tissue-associated microbiota, we investigated the temporal interaction between the microbiota and the host following disruption of the colonic epithelial barrier. METHODOLOGY/PRINCIPAL FINDINGS: Oral administration of DSS was applied as a mechanistic model of environmental damage of the colon and the resulting inflammation characterized for various parameters over time in WT and Nod2 KO mice. RESULTS: In WT mice, DSS damage exposed the host to the commensal flora and led to a migration of the tissue-associated bacteria from the epithelium to mucosal and submucosal layers correlating with changes in proinflammatory cytokine profiles and a progressive transition from acute to chronic inflammation of the colon. Tissue-associated bacteria levels peaked at day 21 post-DSS and declined thereafter, correlating with recruitment of innate immune cells and development of the adaptive immune response. Histological parameters, immune cell infiltration and cytokine biomarkers of inflammation were indistinguishable between Nod2 and WT littermates following DSS, however, Nod2 KO mice demonstrated significantly higher tissue-associated bacterial levels in the colon. DSS damage and Nod2 genotype independently regulated the community structure of the colon microbiota. CONCLUSIONS/SIGNIFICANCE: The results of these experiments demonstrate the integration of environmental and genetic factors in the ecological succession of the commensal flora in mammalian tissue. The association of Nod2 genotype (and other host polymorphisms) and environmental factors likely combine to influence the ecological succession of the tissue-associated microflora accounting in part for their association with the pathogenesis of inflammatory bowel diseases.

Direct bacterial killing in vitro by recombinant Nod2 is compromised by Crohn's disease-associated mutations.

BACKGROUND: A homeostatic relationship with the intestinal microflora is increasingly appreciated as essential for human health and wellbeing. Mutations in the leucine-rich repeat (LRR) domain of Nod2, a bacterial recognition protein, are associated with development of the inflammatory bowel disorder, Crohn's disease. We investigated the molecular mechanisms underlying disruption of intestinal symbiosis in patients carrying Nod2 mutations. METHODOLOGY/PRINCIPAL FINDINGS: In this study, using purified recombinant LRR domains, we demonstrate that Nod2 is a direct antimicrobial agent and this activity is generally deficient in proteins carrying Crohn's-associated mutations. Wild-type, but not Crohn's-associated, Nod2 LRR domains directly interacted with bacteria in vitro, altered their metabolism and disrupted the integrity of the plasma membrane. Antibiotic activity was also expressed by the LRR domains of Nod1 and other pattern recognition receptors suggesting that the LRR domain is a conserved anti-microbial motif supporting innate cellular immunity. CONCLUSIONS/SIGNIFICANCE: The lack of anti-bacterial activity demonstrated with Crohn's-associated Nod2 mutations in vitro, supports the hypothesis that a deficiency in direct bacterial killing contributes to the association of Nod2 polymorphisms with the disease.

CD205 (DEC-205): a recognition receptor for apoptotic and necrotic self.

CD205 is an endocytic receptor that is expressed at high levels by cortical thymic epithelial cells and by dendritic cell (DC) subsets, including the splenic CD8+ DC population that is responsible for cross-presentation of apoptotic cell-derived antigens. Antigen endocytosed via CD205 enters the MHC class I and MHC class II antigen presentation pathways and is subsequently presented to both CD4+ and CD8+ T cells. Despite the known role of CD205 in antigen uptake, the nature of the ligands bound by CD205 has not been determined, and most studies have relied on the use of monoclonal antibodies as surrogate ligands. To go beyond this approach, we created a panel of CD205-IgG fusion proteins spanning the extracellular portion of CD205 and used these to identify the physiological distribution of CD205 ligands. Our data demonstrate that two areas of the CD205 molecule, within C-type lectin-like domains (CTLDs) 3+4 and 9+10, recognise ligands expressed during apoptosis and necrosis of multiple cell types, and are additionally expressed by live cells of the dendritic cell line DC2.4. Thus, CD205 acts as a recognition receptor for dying cells, potentially providing an important pathway for the uptake of self-antigen in intrathymic and peripheral tolerance.

Comparison of cytokine modulation by natural peroxisome proliferator-activated receptor gamma ligands with synthetic ligands in intestinal-like Caco-2 cells and human dendritic cells--potential for dietary modulation of peroxisome proliferator-activated receptor gamma in intestinal inflammation.

BACKGROUND: Peroxisome proliferator-activated receptor gamma (PPARgamma) plays a role in the regulation of intestinal inflammation and is activated by both natural (polyunsaturated fatty acid; PUFAs) and synthetic (troglitazone) ligands. The fatty acid content of defined formula diets may play a role in mediating the antiinflammatory effect, but the mechanism is unclear. OBJECTIVE: We evaluated to what extent the effect of PUFAs on intestinal inflammation is mediated via PPARgamma. DESIGN: The human enterocyte-like cell line Caco-2 and human dendritic cells were stimulated by interleukin (IL) 1beta and lipoprotein polysaccharide, respectively, in the presence of PPARgamma agonists (troglitazone or PUFAs) or antagonist (GW9662). Five PUFAs were tested: alpha-linolenic acid (ALA), conjugated linoleic acid (CLA), docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and gamma-linolenic acid (GLA). Cytokine production was measured by enzyme-linked immunosorbent assay and PPARgamma, I-kappaB, and inducible nitric oxide synthase (iNOS) expression by Western blot. RESULTS: In Caco-2 cells, IL-6 secretion was significantly decreased by troglitazone, DHA, EPA, and GLA. IL-8 production was significantly decreased by troglitazone, ALA, DHA, EPA, and GLA. PPARgamma expression was significantly increased by troglitazone, DHA, and EPA. iNOS expression was significantly decreased by troglitazone, DHA, and EPA. Troglitazone and PUFAs at 0.1 mumol/L tended to increase the expression of I-kappaB. Addition of GW9662 reversed the effect of troglitazone and PUFAs at 0.1 mumol/L on IL-8 production and decreased the expression of PPARgamma. EPA and DHA also modulated the dendritic cell response to lipoprotein polysaccharide. CONCLUSIONS: The tested PUFAs exerted an antiinflammatory effect in vitro in both models. This effect of PUFAs in Caco-2 cells is similar to that of troglitazone on intestinal inflammation mediated by PPARgamma, and the potency of the antiinflammatory effect is linked to the number of double bonds.

NOD2 activity modulates the phenotype of LPS-stimulated dendritic cells to promote the development of T-helper type 2-like lymphocytes - Possible implications for NOD2-associated Crohn's disease.

Sensing of commensal microorganisms via Toll-like receptors (TLR) in the gut is essential for maintaining intestinal homeostasis in healthy individuals. Conversely, Crohn's disease is characterised by an inappropriate T helper-type 1 (Th1)-mediated immune response towards these same microorganisms. NOD2 is expressed by dendritic cells (DC) and mediates responses to bacterial muramyl-dipeptides (MDP). Mutations in NOD2 (CARD15) have recently been associated with susceptibility to Crohn's disease although the underlying mechanisms have yet to be established. We investigated the functional outcome of NOD2 and TLR4-mediated activation in monocyte-derived DC from wild-type NOD2 healthy controls and NOD2 frame-shift mutation-carrying Crohn's disease patients. In wild-type DC, MDP acted synergistically with LPS to amplify inflammatory cytokine production, enhance co-stimulatory molecule expression, and produce DC that promoted the proliferation of naïve, allogeneic, CD4(+) T lymphocytes with a Th2-like cytokine profile. By contrast, DC carrying homozygous NOD2 mutations were unable to react to MDP, responded to LPS only, and promoted the development of Th1 cells. These results suggest activation of the NOD2 pathway in DC modulates their response to TLR agonists and regulates their ability to induce polarised Th1 responses. As a consequence, Crohn's disease patients with defective NOD2 may be predisposed to the generation of strongly polarised Th1 responses against common commensal microorganisms.

Altered expression and endocytic function of CD205 in human dendritic cells, and detection of a CD205-DCL-1 fusion protein upon dendritic cell maturation.

CD205 (DEC-205) is a member of the macrophage mannose receptor family of C-type lectins. These molecules are known to mediate a wide variety of biological functions including the capture and internalization of ligands for subsequent processing and presentation by dendritic cells. Although its ligands await identification, the endocytic properties of CD205 make it an ideal target for those wishing to design vaccines and targeted immunotherapies. We present a detailed analysis of CD205 expression, distribution and endocytosis in human monocyte-derived dendritic cells undergoing lipopolysaccharide-induced maturation. Unlike other members of the macrophage mannose receptor family, CD205 was up-regulated upon dendritic cell maturation. This increase was a result of de novo synthesis as well as a redistribution of molecules from endocytic compartments to the cell surface. Furthermore, the endocytic capacity of CD205 was abrogated and small amounts of the recently identified CD205-DCL-1 fusion protein were detected in mature DC. Our results suggest that CD205 has two distinct functions -- one as an endocytic receptor on immature dendritic cells and a second as a non-endocytic molecule on mature dendritic cells -- and further highlight its potential as an immuno-modulatory target for vaccine and immunotherapy development.

Human pancreatic secretory trypsin inhibitor stabilizes intestinal mucosa against noxious agents.

Pancreatic secretory trypsin inhibitor (PSTI) is a serine protease inhibitor, expressed in gut mucosa, whose function is unclear. We, therefore, examined the effects of PSTI on gut stability and repair. Transgenic mice overexpressing human PSTI within the jejunum (FABPi(-1178 to +28) hPSTI construct) showed no change in baseline morphology or morphometry but reduced indomethacin-induced injury in overexpressing hPSTI region by 42% (P < 0.01). Systemic recombinant hPSTI did not affect baseline morphology or morphometry but truncated injurious effects in prevention and recovery rat models of dextran-sodium-sulfate-induced colitis. In vitro studies showed PSTI stimulated cell migration but not proliferation of human colonic carcinoma HT29 or immortalized mouse colonic YAMC cells. PSTI also induced changes in vectorial ion transport (short-circuit current) when added to basolateral but not apical surfaces of polarized monolayers of Colony-29 cells. Restitution and vectorial ion transport effects of PSTI were dependent on the presence of a functioning epidermal growth factor (EGF) receptor because cells with a disrupted (EGFR(-/-) immortalized cells) or neutralized (EGFR blocking antibodies or tyrosine kinase inhibitor) receptor prevented these effects. PSTI also reduced the cytokine release of lipopolysaccharide-stimulated dendritic cells. We conclude that administration of PSTI may provide a novel method of stabilizing intestinal mucosa against noxious agents and stimulating repair after injury.

Modulation of dendritic cell phenotype and function in an in vitro model of the intestinal epithelium.

A network of dendritic cells (DC) can be detected in close proximity to the epithelial cells overlying Peyer's patches in the gut. Intestinal DC show distinct phenotypes as compared to DC from the systemic lymph nodes (relatively low MHC and costimulatory molecules and high IL-10 and TGFbeta) and may play a role in maintaining tolerance to enteric antigens. We show that a similar phenotype is induced in the presence of a polarised epithelial cell monolayer in vitro. Monocyte-derived DC were co-cultured with Caco-2 intestinal epithelial monolayers for 24 h. Co-culture resulted in DC with reduced expression of MHC class II, CD86, and CD80, and poor T cell stimulatory capacity. Cytokine profiles showed reduced levels of inflammatory cytokine production, and co-cultured DC were less sensitive to stimulation via Toll-like receptors (TLR2, 4, and 6) as a result of increased levels of autocrine TGFbeta production. However, phenotypic changes in co-cultured DC could not be blocked by removal of apoptotic cells or addition of anti-TGFbeta antibodies, suggesting that other soluble factors are involved in DC modulation. Thus, polarised epithelial cell monolayers create a 'tolerogenic' environment which modulates the activity of DC. These results highlight the regulatory importance of the epithelial microenvironment at mucosal surfaces.