T-cell brain infiltration and immature antigen-presenting cells in transgenic models of Alzheimer's disease-like cerebral amyloidosis.

Cerebral beta-amyloidosis, one of the pathological hallmarks of Alzheimer's disease (AD), elicits a well-characterised, microglia-mediated local innate immune response. In contrast, it is not clear whether cells of the adaptive immune system, in particular T-cells, react to cerebral amyloidosis in AD. Even though parenchymal T-cells have been described in post-mortem brains of AD patients, it is not known whether infiltrating T-cells are specifically recruited to the extracellular deposits of beta-amyloid, and whether they are locally activated into proliferating, effector cells upon interaction with antigen-presenting cells (APCs). To address these issues we have analysed by confocal microscopy and flow-cytometry the localisation and activation status of both T-cells and APCs in transgenic (tg) mice models of AD-like cerebral amyloidosis. Increased numbers of infiltrating T-cells were found in amyloid-burdened brain regions of tg mice, with concomitant up-regulation of endothelial adhesion molecules ICAM-1 and VCAM-1, compared to non-tg littermates. The infiltrating T-cells in tg brains did not co-localise with amyloid plaques, produced less interferon-gamma than those in controls and did not proliferate locally. Bona-fide dendritic cells were virtually absent from the brain parenchyma of both non-tg and tg mice, and APCs from tg brains showed an immature phenotype, with accumulation of MHC-II in intracellular compartments. These results indicate that cerebral amyloidosis promotes T-cell infiltration but interferes with local antigen presentation and T-cell activation. The inability of the brain immune surveillance to orchestrate a protective immune response to amyloid-beta peptide might contribute to the accumulation of amyloid in the progression of the disease.

Deficiency of Factor VII activating protease alters the outcome of ischemic stroke in mice.

Factor VII activating protease (FSAP) is a circulating protease with a putative role in hemostasis, remodeling and inflammation. A polymorphism giving rise to low proteolytic activity has been associated with an increased risk of stroke and carotid stenosis. To date, no in vivo studies or mechanistic information is available to explain these results. Based on the polymorphism data we hypothesize that a lack of endogenous FSAP will increase the severity of stroke. Stroke was induced by applying thrombin in the middle cerebral artery in wild-type (WT) and FSAP(-/-) mice. Increased stroke volume and worsened neurological deficit were observed in FSAP(-/-) mice. Raised levels of FSAP protein were detected in the infarcted area of WT mice together with enhanced leukocyte infiltration and apoptosis in FSAP(-/-) mice. There was a concomitant increase in the activation of the NFκB pathway and decrease in expression of the PI3K/AKT pathway proteins. At a cellular level, FSAP increased cell survival and decreased apoptosis in primary cortical neurons and astrocytes exposed to tPA/NMDA excitotoxicity or oxygen glucose deprivation (OGD)/reoxygenation, respectively. This was mediated via the PI3K/AKT pathway with involvement of the protease activated receptor-1. To corroborate the human epidemiological data, which link FSAP with stroke, we now show that the lack of FSAP in mice worsens the outcome of stroke. In the absence of FSAP there was a stronger inflammatory response and lower cell survival due to insufficient activation of the PI3K/AKT pathway.

Review: leucocyte-endothelial cell crosstalk at the blood-brain barrier: a prerequisite for successful immune cell entry to the brain.

Leucocyte migration into the central nervous system is a key stage in the development of multiple sclerosis. While much has been learnt regarding the sequential steps of leucocyte capture, adhesion and migration across the vasculature, the molecular basis of leucocyte extravasation is only just being unravelled. It is now recognized that bidirectional crosstalk between the immune cell and endothelium is an essential element in mediating diapedesis during both normal immune surveillance and under inflammatory conditions. The induction of various signalling networks, through engagement of cell surface molecules such as integrins on the leucocyte and immunoglobulin superfamily cell adhesion molecules on the endothelial cell, play a major role in determining the pattern and route of leucocyte emigration. In this review we discuss the extent of our knowledge regarding leucocyte migration across the blood-brain barrier and in particular the endothelial cell signalling pathways contributing to this process.

Immune function of the blood-brain barrier: incomplete presentation of protein (auto-)antigens by rat brain microvascular endothelium in vitro.

The endothelial blood-brain barrier (BBB) has a critical role in controlling lymphocyte traffic into the central nervous system (CNS), both in physiological immunosurveillance, and in its pathological aberrations. The intercellular signals that possibly could induce lymphocytes to cross the BBB include immunogenic presentation of protein (auto-)antigens by BBB endothelia to circulating T lymphocytes. This concept has raised much, though controversial, attention. We approached this problem by analyzing in vitro immunospecific interactions between clonal rat T lymphocyte lines with syngeneic, stringently purified endothelial monolayer cultures from adult brain micro-vessels. The rat brain endothelia (RBE) were established from rat brain capillaries using double collagenase digestion, density gradient fractionation and selective cytolysis of contaminating pericytes by anti-Thy 1.1 antibodies and complement. Incubation with interferon-gamma in most of the brain-derived endothelial cells induced Ia-antigens in the cytoplasm and on the cell surface in some of the cells. Before the treatment, the cells were completely Ia-negative. Pericytes were unresponsive to IFN-gamma treatment. When confronted with syngeneic T cell lines specific for protein (auto-)antigens (e.g., ovalbumin and myelin basic protein, MBP), RBE were completely unable to induce antigen-specific proliferation of syngeneic T lymphocytes irrespective of pretreatment with IFN-gamma and of cell density. RBE were inert towards the T cells, and did not suppress T cell activation induced by other "professional" antigen presenting cells (APC) such as thymus-derived dendritic cells or macrophages. IFN-gamma-treated RBE were, however, susceptible to immunospecific T cell killing. They were lysed by MBP-specific T cells in the presence of the specific antigen or Con A. Antigen dependent lysis was restricted by the appropriate (MHC) class II product. We conclude that the interaction of brain endothelial cells with encephalitogenic T lymphocytes may involve recognition of antigen in the molecular context of relevant MHC products, but that this interaction per se is insufficient to initiate the full T cell activation program.

Endothelial cell laminin isoforms, laminins 8 and 10, play decisive roles in T cell recruitment across the blood-brain barrier in experimental autoimmune encephalomyelitis.

An active involvement of blood-brain barrier endothelial cell basement membranes in development of inflammatory lesions in the central nervous system (CNS) has not been considered to date. Here we investigated the molecular composition and possible function of the extracellular matrix encountered by extravasating T lymphocytes during experimental autoimmune encephalomyelitis (EAE). Endothelial basement membranes contained laminin 8 (alpha4beta1gamma1) and/or 10 (alpha5beta1gamma1) and their expression was influenced by proinflammatory cytokines or angiostatic agents. T cells emigrating into the CNS during EAE encountered two biochemically distinct basement membranes, the endothelial (containing laminins 8 and 10) and the parenchymal (containing laminins 1 and 2) basement membranes. However, inflammatory cuffs occurred exclusively around endothelial basement membranes containing laminin 8, whereas in the presence of laminin 10 no infiltration was detectable. In vitro assays using encephalitogenic T cell lines revealed adhesion to laminins 8 and 10, whereas binding to laminins 1 and 2 could not be induced. Downregulation of integrin alpha6 on cerebral endothelium at sites of T cell infiltration, plus a high turnover of laminin 8 at these sites, suggested two possible roles for laminin 8 in the endothelial basement membrane: one at the level of the endothelial cells resulting in reduced adhesion and, thereby, increased penetrability of the monolayer; and secondly at the level of the T cells providing direct signals to the transmigrating cells.

Alpha4-integrin-VCAM-1 binding mediates G protein-independent capture of encephalitogenic T cell blasts to CNS white matter microvessels.

Direct in vivo evidence is still lacking for alpha4-integrin-mediated T cell interaction with VCAM-1 on blood-brain barrier-endothelium in experimental autoimmune encephalomyelitis (EAE). To investigate a possible alpha4-integrin-mediated interaction of encephalitogenic T cell blasts with VCAM-1 on the blood-brain barrier white matter endothelium in vivo, we have developed a novel spinal cord window preparation that enabled us to directly visualize CNS white matter microcirculation by intravital fluorescence videomicroscopy. Our study provides the first in vivo evidence that encephalitogenic T cell blasts interact with the spinal cord white matter microvasculature without rolling and that alpha4-integrin mediates the G protein-independent capture and subsequently the G protein-dependent adhesion strengthening of T cell blasts to microvascular VCAM-1.

The development of experimental autoimmune encephalomyelitis in the mouse requires alpha4-integrin but not alpha4beta7-integrin.

Because monoclonal antibodies (mAbs) directed against alpha4-integrin and VCAM-1 inhibit the development of experimental autoimmune encephalomyelitis (EAE) in vivo, it has been concluded that the successful therapeutic effect is due to interference with alpha4beta1/VCAM-1-mediated interaction of autoaggressive T cells with the blood-brain barrier. A possible role for alpha4beta7-integrin, or interference with other T cell mediated events during the pathogenesis of EAE, has not been considered. We have compared the effects of mAb therapy on the development of EAE in the SJL/N mouse, using a large panel of mAbs directed against alpha4, beta7, the alpha4beta7-heterodimer, and against VCAM-1. Although encephalitogenic T cells express both alpha4-integrins, mAbs directed against the alpha4beta7-heterodimer or against the beta7-subunit did not interfere with the development of EAE. In contrast, mAbs directed against alpha4 and VCAM-1 inhibited or diminished clinical or histopathological signs of EAE. Our data demonstrate for the first time that alpha4beta7 is not essential for the development of EAE. Furthermore, our in vitro studies suggest that the therapeutic effect of anti-alpha4-treatment of EAE might also be caused by inhibition of antigen-specific T cell proliferation.

PECAM-1/CD31 trans-homophilic binding at the intercellular junctions is independent of its cytoplasmic domain; evidence for heterophilic interaction with integrin alphavbeta3 in Cis.

PECAM-1/CD31 is a cell adhesion and signaling molecule that is enriched at the endothelial cell junctions. Alternative splicing generates multiple PECAM-1 splice variants, which differ in their cytoplasmic domains. It has been suggested that the extracellular ligand-binding property, homophilic versus heterophilic, of these isoforms is controlled by their cytoplasmic tails. To determine whether the cytoplasmic domains also regulate the cell surface distribution of PECAM-1 splice variants, we examined the distribution of CD31-EGFPs (PECAM-1 isoforms tagged with the enhanced green fluorescent protein) in living Chinese hamster ovary cells and in PECAM-1-deficient endothelial cells. Our results indicate that the extracellular, rather than the cytoplasmic domain, directs PECAM-1 to the cell-cell borders. Furthermore, coculturing PECAM-1 expressing and deficient cells along with transfection of CD31-EGFP cDNAs into PECAM-1 deficient cells reveal that this PECAM-1 localization is mediated by homophilic interactions. Although the integrin alphavbeta3 has been shown to interact with PECAM-1, this trans-heterophilic interaction was not detected at the borders of endothelial cells. However, based on cocapping experiments performed on proT cells, we provide evidence that the integrin alphavbeta3 associates with PECAM-1 on the same cell surface as in a cis manner.

How do I manage hyperglycemia/post-transplant diabetes mellitus after allogeneic HSCT.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients frequently develop glucose intolerance and post-transplant diabetes mellitus (PTDM). The clinical importance of PTDM and its detrimental impact on HSCT outcomes are under-recognized. After allo-HSCT, various mechanisms can contribute to the development of PTDM. Here we review information about hyperglycemia and PTDM after allo-HSCT as well as PTDM after solid organ transplantation and describe ways to manage hyperglycemia/PTDM after allogeneic HSCT. Taking into consideration a lack of well-established evidence in the field of allo-HSCT, more studies should be conducted in the future, which will require closer multidisciplinary collaboration between hematologists, endocrinologists and nutritionists.

Interaction of T lymphocytes with cerebral endothelial cells in vitro.

As a prerequisite of inflammatory lesion formation in (auto-)immune disease of the central nervous system, lymphocytes have to interact with brain endothelia. In recent years much progress has been made towards a better understanding of mechanisms and factors involved in organ specific homing of lymphocytes. Many lines of evidence indicate that T lymphocytes recognizing antigens which are exclusively beyond the blood-brain barrier cross this barrier only when they are in an activated state, irrespective of their antigen specificity. Antigen presentation by blood-brain barrier endothelia, however, may play a role in later stages of florid inflammation.

Lymphocyte targeting of the central nervous system: a review of afferent and efferent CNS-immune pathways.

The central nervous system (CNS) in considered to be an immunological privileged site. However, inflammatory reactions in response to virus infections, in multiple sclerosis (MS) and in experimental autoimmune encephalomyelitis (EAE) suggest that there are definite connections between the CNS and the immune system. In this review, we examine evidence for afferent and efferent pathways of communication between the CNS and the immune system, the pivotal role of regional lymph nodes in T-cell mediated autoimmune disease of the CNS, and the factors involved in lymphocyte targeting of the CNS. Afferent pathways of lymphatic drainage of the brain are well established in a variety of species, especially rodents. Fluid and antigens appear to drain along perivascular spaces populated by immunocompetent perivascular cells. Drainage pathways connect directly via the cribriform plate to nasal lymphatics and cervical lymph nodes. Soluble antigens draining from the brain induce antibody production in the cervical lymph nodes. Using a model of cryolesion-enhanced EAE, we review the role of lymphatic drainage and cervical lymph nodes in the enhancement of cerebral EAE. If a brain wound in the form of a cryolesion is produced 8 days post inoculation (dpi) of antigen in the induction of acute EAE, there is a 6-fold increase in severity of cerebral EAE by 15 dpi. Removal of the cervical lymph nodes significantly reduces such enhancement of EAE. These findings suggest that drainage of antigens from the brain to the cervical lymph nodes, in the presence of activated lymphocytes in the meninges or CNS, results in an enhanced second wave of lymphocytes targeting the brain. In examining the efferent immune pathway by which lymphocytes home to the CNS, several studies have characterized the phenotype of infiltrating T lymphocytes by the use of immunocytochemistry or FACS analysis. T-cells infiltrating the CNS are recently activated/memory lymphocytes typified by their high expression of CD44, LFA-1 and ICAM-1 and low expression of CD45RB in the mouse. Following the induction of EAE in susceptible mice, ICAM-1 and VCAM-1 are dramatically upregulated on CNS vessels; lymphocytes bind to such vessels via the interaction of their known ligands, LFA-1/Mac-1 and alpha 4-integrins, at least in vitro. It appears that alpha 4-integrin plays a key role in lymphocyte recruitment across the blood-brain barrier and may be a major factor in lymphocyte targeting of the CNS. Definition of factors involved in the afferent and efferent connections between the CNS and the immune system may clarify mechanisms involved in immune privilege of the CNS and may open significant therapeutic opportunities for multiple sclerosis.

Interaction of alpha4-integrin with VCAM-1 is involved in adhesion of encephalitogenic T cell blasts to brain endothelium but not in their transendothelial migration in vitro.

Based on the observation that antibodies directed against alpha4-integrin and its counterreceptor VCAM-1 inhibit inflammatory cell recruitment into the central nervous system (CNS) during experimental autoimmune encephalomyelitis (EAE), it has been concluded that alpha4-integrin/VCAM-1 interaction plays a critical role in T cell interaction with the blood-brain barrier (BBB) endothelium. In order to define the exact role of alpha4-integrin and VCAM-1 in T cell recruitment across the BBB endothelium we set up in vitro studies, where we investigated the interaction of freshly activated autoaggressive T cell blasts with the brain endothelial cell line bEnd5. A large panel of blocking antibodies directed against the alpha4-, beta1- and beta7-integrin subunits or against the alpha4beta7-heterodimer and against endothelial VCAM-1 significantly reduced adhesion of encephalitogenic T cell blasts to brain endothelium. However, the very same antibodies did not influence transendothelial migration of autoaggressive T cell blasts across a bEnd5 monolayer. Our in vitro observations, therefore, suggest that in vivo alpha4/VCAM-1 interactions are not involved in transendothelial migration of encephalitogenic T cells across the BBB but rather mediate earlier steps of T cell/BBB-interaction such as firm adhesion.

Induction of persistently demyelinated lesions in the rat following the repeated adoptive transfer of encephalitogenic T cells and demyelinating antibody.

A chronic relapsing model of demyelinating experimental allergic encephalomyelitis (EAE) was induced in Lewis rats by the repeated co-transfer of encephalitogenic, myelin basic protein (MBP)-specific T cells in combination with a demyelinating monoclonal antibody (mAb) specific for the myelin oligodendrocyte glycoprotein (MOG). In controls, repeated injections of 5 x 10(5) MBP-specific T cells at intervals of 18-21 days resulted in an increasing resistance to the induction of further episodes of EAE. However, intravenous injection of the mAb 4 days after each T cell transfer overcame this 'vaccination' effect and induced severe clinical relapses associated with an increasing and persistent neurological deficit. Histological examination revealed that four cycles of treatment with T cells and mAb were sufficient to result in the formation of large plaques of demyelination in the spinal cord that failed to undergo significant remyelination within 60 days of the final injection of mAb. These lesions consisted of a matrix of astrocytic scar tissue traversed by numerous naked axons. These observations demonstrate that the formation of large, persistently, demyelinated lesions in a T cell-mediated model of EAE in the Lewis rat is dependent on the presence of an appropriate anti-myelin autoantibody response.

Cell adhesion molecules on vessels during inflammation in the mouse central nervous system.

The expression of endothelial cell adhesion molecules (CAMs) in the central nervous system (CNS) of the mouse was examined during an inflammation induced by intracerebral injection of killed Corynebacterium parvum (C. parvum). We showed that injection of killed C. parvum produced an inflammatory cellular infiltrate limited to the injected brain hemisphere. However, the upregulation of ICAM-1 and VCAM-1 on brain endothelium occurred starting 2 days after C. parvum injection throughout the entire CNS and was not restricted to vessels surrounded by a cellular infiltrate. In contrast to the systemic upregulation of ICAM-1 and VCAM-1, cerebral vessels located in the center of the cellular infiltrate started to express the MECA-32 antigen, suggesting an altered functional status of the endothelial cells, as this antigen is suppressed during development of the blood-brain barrier (BBB). Binding assays performed on frozen sections of inflamed brains are consistent with an important role for endothelial VCAM-1 in the recruitment of lymphocytes during inflammation in the CNS of the mouse.

Lysis of rat brain microvascular endothelial cells mediated by resting but not activated MBP-specific CD4+ T cell lines.

Previous work from this laboratory showed that the encephalitogenic potential of myelin basic protein (MBP)-specific T cells is inseparably associated with their cytotoxic potential. MBP-specific T cells lyse all cells that present autoimmunogenic MBP peptide in context of appropriate MHC class II determinants. Beside class II-induced glia cells, blood-brain barrier-derived endothelial cells were identified as highly susceptible target cells for cytotoxic MBP-specific T cells. Here we show that the cytotoxic reaction against endothelial cells essentially differs from cytotoxicity against other target cells. In contrast to classical T cell-mediated lytic responses, which are most efficiently executed by activated T cells, rat brain endothelium (RBE) lysis could only be mediated by resting T cells. Activated MBP-specific T cell blasts were not able to mediate strong RBE lysis. Furthermore, T cell lines with specificities for protein antigens other than MBP did not cause RBE lysis. A role of the cytolytic capacity of resting MBP-specific T cells in the pathogenesis of experimental autoimmune encephalomyelitis is probable.

Adhesion molecule phenotype of T lymphocytes in inflamed CNS.

The phenotype of T cells in the central nervous system (CNS) in two models of chronic inflammation (experimental allergic encephalomyelitis and Corynebacterium parvum-induced inflammation) was compared to that of T cells in gut and chronically inflamed subcutaneous tissue and lung. CNS T cells display a similar phenotype in both inflammatory models, and are phenotypically unique compared to T cells from the other inflamed tissues. T cells from inflamed CNS are mainly CD4+ and are the only population examined that express a typical activated/memory phenotype: CD44high/LFA-1high/ICAM-1high/CD45RBlow. The CNS T cells are alpha4beta7-integrin(negative), but express alpha4-integrin and activated beta1 integrin, suggesting expression of the alpha4beta1-heterodimer in an activated state. In contrast, most T cells in gut express low levels of activated beta1 integrin. The CNS T cells lack expression of alpha6 and alphaE integrin chains and L-selectin. In inflamed CNS and inflamed subcutaneous tissue, approximately 50% of T cells express high affinity ligands for P-selectin while fewer than 10% express high affinity ligands for E-selectin. In summary, our data show that, independent of the inflammatory stimulus, T cells recruited into the inflamed CNS are phenotypically distinct from T cells in other inflamed tissues. This finding leads us to hypothesize the existence of a phenotypically distinct 'CNS-seeking' T lymphocyte population.

Cell surface bound and soluble adhesion molecules in CSF and blood in multiple sclerosis: correlation with MRI-measures of subclinical disease severity and activity.

BACKGROUND: The expression of soluble cell adhesion molecules (AM) in cerebrospinal fluid (CSF) and blood and their significance as measures of disease activity has been extensively studied in patients with multiple sclerosis (MS). In previous studies, we found that cell surface bound AM on mononuclear cells (MNC) in CSF and blood might be useful markers of clinical disease activity in MS patients. OBJECTIVE: To analyze the correlation of cell surface bound and soluble AM in CSF and blood with magnetic resonance imaging (MRI) markers of subclinical disease severity and activity in patients with MS. METHODS: Expression levels of cell surface bound AM on peripheral blood and CSF MNC were determined by flow cytometry analysis in 77 (CSF: 33) MS patients. Concentration levels of the soluble forms of AM were measured by enzyme-linked immunosorbent assay (ELISA). In corresponding cerebral gadolinium (Gd)-enhanced MRI scans, we determined both measures of subclinical disease severity and subclinical disease activity. RESULTS: The expression levels of cell surface bound AM in peripheral blood correlated inversely with parameters for subclinical disease severity and activity on cerebral MRI scans as well as with the disease duration. Furthermore, we found significant correlations between serum levels of soluble AM and patient age but not with disease duration. CONCLUSIONS: Our results suggest that subclinical disease progression may be associated with a decrease of the expression of cell surface bound AM on peripheral blood MNC. This might be a result of activated MNC migration into the CNS.

Involvement of the choroid plexus in central nervous system inflammation.

During inflammatory conditions in the central nervous system (CNS), immune cells immigrate into the CNS and can be detected in the CNS parenchyma and in the cerebrospinal fluid (CSF). The most comprehensively investigated model for CNS inflammation is experimental autoimmune encephalomyelitis (EAE), which is considered the prototype model for the human disease multiple sclerosis (MS). In EAE autoagressive CD4(+), T cells gain access to the CNS and initiate the molecular and cellular events leading to edema, inflammation, and demyelination in the CNS. The endothelial blood-brain barrier (BBB) has been considered the obvious place of entry for the circulating immune cells into the CNS. A role of the choroid plexus in the pathogenesis of EAE or MS, i.e., as an alternative entry site for circulating lymphocytes directly into the CSF, has not been seriously considered before. However, during EAE, we observed massive ultrastructural changes within the choroid plexus, which are different from changes observed during hypoxia. Using immunohistochemistry and in situ hybridization, we observed expression of VCAM-1 and ICAM-1 in the choroid plexus and demonstrated their upregulation and also de novo expression of MAdCAM-1 during EAE. Ultrastructural studies revealed polar localization of ICAM-1, VCAM-1, and MAdCAM-1 on the apical surface of choroid plexus epithelial cells and their complete absence on the fenestrated endothelial cells within the choroid plexus parenchyme. Furthermore, ICAM-1, VCAM-1, and MAdCAM-1 expressed in choroid plexus epithelium mediated binding of lymphocytes via their known ligands. In vitro, choroid plexus epithelial cells can be induced to express ICAM-1, VCAM-1, MAdCAM-1, and, additionally, MHC class I and II molecules on their surface. Taken together, our observations imply a previously unappreciated function of the choroid plexus in the immunosurveillance of the CNS.

Pulmonary response to group B streptococcal toxin in young lambs.

Marked respiratory distress is seen in severe early onset group B beta-hemolytic streptococcal (GBS) disease in newborn infants. To investigate the pathophysiological effects of a polysaccharide toxin from GBS type III cultures, obtained from an infant who died from this disease, young chronically instrumented, unanesthetized lambs were studied with measurements of lung mechanics, lung volumes, ventilation, hemodynamics, and lung vascular permeability. Intravenously administered GBS toxin resulted in a biphasic response with an early threefold increase in total lung resistance, 40% decrease in dynamic lung compliance, and 30% increase in minute ventilation coinciding with hypoxemia, pulmonary hypertension, and fever. A second phase of the response followed consisting of less prominent changes in these variables as well as increased lung lymph protein clearance compatible with increased vascular permeability. The temporal close relationship between marked leukopenia and increased lung lymph thromboxane B2 concentrations to the simultaneously occurring pulmonary hypertension and changes in lung mechanics suggests that leukocytes and thromboxane A2 may be mediators of these GBS toxin-induced effects.

Claudin-1, claudin-2 and claudin-11 are present in tight junctions of choroid plexus epithelium of the mouse.

The choroid plexus epithelium forms the blood-cerebrospinal fluid (CSF) barrier and is responsible for the secretion of the CSF from the blood. The morphological correlate of the blood-CSF barrier are the tight junctions of choroid plexus epithelium. By freeze-fracture electron microscopy it has been demonstrated that choroid plexus epithelial tight junctions form parallel strands resembling those of Sertoli cells building the blood-testis barrier and those of the myelin sheaths of oligodendrocytes. As the oligodendrocyte specific protein/claudin-11 has been shown to be the central mediator of parallel-array tight junctions in Sertoli cells and myelin sheaths in mice, we asked whether claudin-11 is present in the tight junctions of choroid plexus epithelial cells of the mouse. Here, we present the first direct evidence that claudin-11 besides claudin-1 and -2, occludin and the zonula occludens protein ZO-1 is present in choroid plexus epithelial tight junctions. During inflammation in the central nervous system such as experimental autoimmune encephalomyelitis, the molecular composition of choroid plexus epithelial tight junctions does not change considerably. Their unique molecular composition, with claudin-11 accompanied by claudin-1 and claudin-2 points to a unique regulatory mechanism of the blood-CSF-barrier function.