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H Wekerle

Publications and source records attributed to H Wekerle.

At least 91 records · Page 5Linked to original sources
PubMed1994

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.

Animals↗
PubMed1994

Transcription factor NF-kappa B is activated in microglia during experimental autoimmune encephalomyelitis.

NF-kappa B is an inducible transcription factor involved in the induction of multiple genes during inflammatory processes. So far the information pertaining to the role of NF-kappa B in autoimmune processes has been restricted to in vitro analysis. To further characterize the role of NF-kappa B in vivo, the involvement of NF-kappa B has been studied by immunocytochemistry in T cell-mediated autoimmune encephalomyelitis (EAE) of the Lewis rat. In non-diseased animals, immunoreactivity for the DNA-binding subunit p50 and for the DNA-binding and transactivating subunit p65 was low and restricted to the surface of small to medium-sized blood vessels. Strong immunoreactivities for p50 and p65 were detected at the peak of clinical disease. At the recovery stage of EAE, p50 and p65 immunoreactivities had declined to base line levels. Within the resident glial cell population, p50 and p65-immunoreactive cells were identified as OX-42-positive microglia. GFAP-positive astrocytes did not show significant p50 or p65 immunoreactivity. In the core and the vicinity of perivascular inflammatory lesions, both ED-1-positive macrophages and W3/13-positive T lymphocytes and monocytes were strongly immunoreactive for NF-kappa B. Our data suggest a crucial involvement of the transcription factor NF-kappa B in autoimmune diseases of the central nervous system. Furthermore, NF-kappa B appears as a useful marker for inflammatory processes in vivo.

Animals↗
PubMed1994

The role of the thymus in myasthenia gravis.

The experimental work discussed here supports the hypothesis that in the pathogenesis of MG the initial and essential steps take place within the thymus. Most if not all thymuses of MG patients contain B cells capable of producing AChR specific autoantibody along with appropriate stroma elements. Hyperplastic thymuses characteristically contain germinal centers with cellular complexes of AChR-producing MC and surrounding interdigitating dendritic cells. In thymomas, the source of the myasthenogenic autoantigen is less obvious. There are data suggesting that thymoma epithelium expresses a protein sharing certain peptide epitopes with the AChR alpha chain, although there is no further molecular similarity. A unique type of 'molecular self-mimicry' cold be involved in the initiation of thymoma-associated MG.

Animals↗
PubMed1994

Human astrocytes are only partially competent antigen presenting cells. Possible implications for lesion development in multiple sclerosis.

Highly purified astrocyte cultures from human embryonic brain were examined for their capacity to present antigen to human leukocyte antigen (HLA) class II compatible, cytolytic CD4+ T lymphocytes. Most astrocytes constitutively expressed HLA class I products and LFA-3 (CD58). Constitutive expression of HLA class II, LFA-1 alpha (CD11a) and ICAM-1 (CD54) was lower and varied among different cultures, while LFA-2 (CD2) was absent. IFN-gamma alone or in combination with TNF-alpha strongly enhanced expression of HLA class I, HLA-DR, -DP, -DQ, LFA-1 alpha and ICAM-1, but did not affect expression of LFA-2 (CD2) and LFA-3 (CD58). TNF-alpha alone induced only HLA class I and ICAM-1, but not HLA class II or LFA-1 alpha. Cytokine treated, but not untreated astrocytes were able to present protein (auto-)antigens to specific T lymphocyte lines. Astrocytes expressing appropriate major histocompatibility complex class II products were lysed by CD4+ T cells specific for myelin basic protein or tetanus toxoid. The lytic response was antigen dose dependent and HLA-DR restricted. It could be blocked by antibodies against HLA-DR determinants and against the adhesion molecules LFA-1 alpha and ICAM-1. In remarkable contrast to their susceptibility to T cell lysis, antigen presenting astrocytes were not only completely unable to induce T cell proliferation but even inhibited proliferation. The results indicate that, although human astrocytes have the potential to present protein antigens to CD4+ T cells, they do not induce the co-stimulatory factors required to trigger the complete T cell activation programme.

Antigen-Presenting Cells↗
PubMed1994

Multiple sclerosis. Immunomodulatory effects of human astrocytes on T cells.

Using a human culture system, we have previously shown that interferon-gamma-and tumour necrosis factor-alpha-stimulated astrocytes are capable of presenting antigens to T lymphocytes, but do not support antigen-dependent T cell proliferation. To gain further insight into the mechanisms involved in the local regulation of intracerebral T cell responses, we have investigated the effects of astrocytes on T cell proliferation induced by peripheral blood-derived mononuclear cells (PBMC). We found that astrocytes derived from human embryonic brain were able to suppress PBMC-dependent proliferation of antigen-specific, CD4+ T cell lines. Interferon-gamma production by PBMC-stimulated T cells was also suppressed by astrocytes, and this inhibition was seen as early as 6 h after initiation of co-culture. The inhibitory effect was observed in the presence of both HLA matched and mismatched astrocytes and was mediated by astrocyte-derived soluble factor(s) rather than by direct cellular contact. Inhibition of T cell proliferation was incompletely reverted by indomethacin, suggesting that prostaglandins were partially involved in the suppressive effect. The cytotoxic mediator nitric oxide was not involved in astrocyte-mediated inhibition. These observations led us to further investigate the contribution of other mediators known to down-regulate inflammatory processes. Our astrocyte cultures did not synthesize interleukin (IL)-4 or IL-10, whereas they secreted both the latent and active forms of transforming growth factor-beta 2. Transforming growth factor-beta was, however, found not to participate in astrocyte-induced inhibition in vitro. The inhibitory properties of human astrocytes may contribute to confinement of inflammatory lesions in multiple sclerosis and other inflammatory diseases of the central nervous system.

Astrocytes↗
PubMed1994

Constitutive NF-kappa B activity in neurons.

NF-kappa B is inducible transcription factor present in many cell types in a latent cytoplasmic form. So far, only immune cells including mature B cells, thymocytes, and adherent macrophages have been reported to contain constitutively active forms of NF-kappa B in the nucleus. A recent study showed that the human immunodeficiency virus type 1 (HIV-1) promoter is highly active in several brain regions of transgenic mice (J. R. Corboy, J. M. Buzy, M. C. Zink, and J. E. Clements, Science 258:1804-1807, 1992). Since the activity of this viral enhancer is governed mainly by two binding sites for NF-kappa B, we were prompted to investigate the state of NF-kappa B activity in neurons. Primary neuronal cultures derived from rat hippocampus and cerebral cortex showed a high constitutive expression of an HIV-1 long terminal repeat-driven luciferase reporter gene, which was primarily dependent on intact NF-kappa B binding sites and was abolished upon coexpression of the NF-kappa B-specific inhibitor I kappa B-alpha. Indirect immunofluorescence and confocal laser microscopy showed that the activity of NF-kappa B correlated with the presence of the NF-kappa B subunits p50 and RelA (p65) in nuclei of cultured neurons. NF-kappa B was also constitutively active in neurons in vivo. As investigated by electrophoretic mobility shift assays, constitutive NF-kappa B DNA-binding activity was highly enriched in fractions containing neuronal nuclei prepared from rat cerebral cortex. Nuclear NF-kappa B-specific immunostaining was also seen in cryosections from mouse cerebral cortex and hippocampus. Only a subset of neurons was stained. Activated NF-kappa B in the brain is likely to participate in normal brain function and to reflect a distinct state of neuronal activity or differentiation. Furthermore, it may explain the high level of activity of the HIV-1 enhancer in neurons, an observation potentially relevant for the etiology of the AIDS dementia complex caused by HIV infection of the central nervous system.

Animals↗
PubMed1994

Contra: evidence against a primary lesion in the target organ in autoimmune disease.

We discuss evidence suggesting that autoreactive T cell clones are components of the normal immune repertoire. Since these lymphocytes reach the brain only in the activated state, activation must take place outside of the target tissue. Within the brain, most of the autoimmune T cells undergo apoptosis rather than further proliferation.

Animals↗
PubMed1994

Myogenesis in thymic transplants in the severe combined immunodeficient mouse model of myasthenia gravis. Differentiation of thymic myoid cells into striated muscle cells.

Thymic myoid cells (TMCs) bearing acetylcholine receptors (AchR) on their surface have a central role in the concept of intrathymic autosensitization in the pathogenesis of myasthenia gravis. In a SCID mouse model of myasthenia gravis, solid pieces of thymuses with lymphofollicular hyperplasia were transplanted into SCID mice. The chimeric mice displayed long-term secretion of anti-AchR antibodies. Here, we traced the fate of TMCs contained in transplanted myasthenia gravis thymuses. Unexpectedly, the number of thymic TMCs in transplanted tissue was slightly higher than in untransplanted thymus. More strikingly, the transplanted TMCs were more highly differentiated than their nontransplanted counterparts. This was demonstrated by a more than 10-fold increase of AchR-main immunogenic region epitopes recognized by monoclonal antibody 198. Some TMCs had even differentiated into striated muscle cells. The abundance of AchRs in human thymic transplants in the SCID mouse model of myasthenia gravis may help to study the mechanisms of autosensitization against the AchR in vivo.

Animals↗
PubMed1994

The thymus in myasthenia gravis.

The experimental work discussed here endorses the hypothesis that in the pathogenesis of MG the initial and essential steps take place within the thymus. Most, if not all, thymuses of MG patients contain B cells capable of producing AChR-specific autoantibody along with appropriate stroma elements. This is especially pertinent in hyperplastic thymuses with germinal centers, which characteristically contain cellular complexes formed by AChR-producing MCs and surrounding interdigitating dendritic cells. The source of the myasthenogenic autoantigen is more complex in thymomas. There are data suggesting that thymoma epithelium express a protein that shares certain peptide epitopes with the AChR alpha chain, although there is no further molecular similarity. A unique type of "molecular self mimicry" could be the starter of thymoma-associated MG.

Animals↗
PubMed1993

Transformation of human T-cell clones by Herpesvirus saimiri: intact antigen recognition by autonomously growing myelin basic protein-specific T cells.

Herpesvirus saimiri has recently been shown to immortalize human T cells. It was unknown, however, whether Herpesvirus saimiri transformation affects T-cell receptor (TCR) expression and signal transduction. In the present study, we have transformed CD4+ human T-cell clones specific for human myelin basic protein. The transformed T cells were grown in interleukin 2 and divided in the absence of antigen and antigen-presenting cells. They retained the membrane phenotype of activated T cells and secreted the cytokines interferon gamma and lymphotoxin, but interleukin 4 was not detected. Further, the transformed T cells continued to express the original TCR as demonstrated by TCR variable-region-V beta-specific monoclonal antibodies and TCR sequencing. Antigen-specific recognition and signal transduction by the TCR were demonstrated by myelin-basic-protein-induced HLA-DR-restricted secretion of interferon gamma and lymphotoxin and by myelin-basic-protein-specific proliferation. Antigen specificity and reactivity have been maintained for > 1 year after transformation. Transformation with Herpesvirus saimiri now allows the production of virtually unlimited numbers of (auto)antigen-specific T cells expressing functional TCR and a stable membrane phenotype. This technology will facilitate studies of the pathogenesis of putative autoimmune diseases, such as multiple sclerosis, and may be of help in TCR-targeted immunotherapy.

Antigens, CD↗
PubMed1993

Transforming growth factor beta expression in reactive spinal cord microglia and meningeal inflammatory cells during experimental allergic neuritis.

Experimental allergic neuritis (EAN), an inflammatory demyelinating disorder of the peripheral nervous system, is preceded and accompanied by a massive microglial reaction in the spinal cord which occurs in the absence of inflammatory cells infiltrating the cord parenchyma. Since transforming growth factor beta (TGF-beta) has been shown to play a beneficial role in experimental autoimmune disease and might be involved in the regulation of glial activity, we have investigated the expression of TGF-beta in EAN spinal cord and nerve root tissue. Adoptive transfer EAN was induced by the injection of neurotogenic T-cells specific for the P2 myelin protein. In normal spinal cord tissue, both TGF-beta 1 and TGF-beta 3 mRNA were constitutively expressed at low levels. Already 3 days following injection of P2-specific T-cells, TGF-beta 1 mRNA levels began to increase, peaked at day 6 at levels about tenfold above normal, and thereafter declined. TGF-beta 3 was induced even earlier with a sharp rise at day 3 and a peak fourfold above normal at day 4. In situ hybridization for TGF-beta 1 performed on spinal cord sections 6 days after injection of cells localized TGF-beta 1 mRNA to many nonneuronal cells with the typical morphology of microglia. In addition, TGF-beta 1 mRNA was observed in the meninges, and massive accumulation of signal was seen over inflammatory cells infiltrating the nerve roots. Our data indicate that TGF-beta 1 and -beta 3 are involved in regulating the glial response in EAN and that activated microglial cells might control their own activity state by expressing TGF-beta 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Human T cell autoimmunity against myelin basic protein: CD4+ cells recognizing epitopes of the T cell receptor beta chain from a myelin basic protein-specific T cell clone.

We have investigated whether the normal immune system contains T cells that are able to recognize T cell receptor (TcR) determinants of autologous autoantigen-specific T cells. The T cell clone HW.BP3, specific for myelin basic protein (MBP) was isolated from a healthy donor. HW.BP3 is restricted by HLA-DR2a, and reacts to human MBP 139-153. The expressed alpha beta TcR genes of HW.BP3 were cloned and sequenced, and the sequences analyzed for potential T cell epitopes. Two synthetic peptides, one from the VDJ beta junctional (beta 1) and one from the V beta region (beta 2) of the TcR of HW.BP3, were used to select four TcR peptide-specific T cell lines from the donor of HW.BP3. All anti-TcR lines had the phenotype CD3+/CD4+/HLA-DR+/CD25+/CD45RO+, and recognized the antigen in the context of HLA-DR. Three anti-TcR lines, which had been selected for reactivity to peptide beta 1, recognized exclusively this peptide restricted by HLA-DR2b. One anti-TcR line, selected for peptide beta 2, responded to both peptides beta 1 and beta 2 when presented by autologous blood mononuclear cells, but not by HLA-DR2a- or HLA-DR2b-transfected L cells. All TcR peptide-specific T cell lines were efficiently cytotoxic. They specifically lysed autologous macrophages or HW.BP3 line cells in the presence of exogenous peptide antigen. In contrast, HW.BP3 did not present endogenous TcR peptides to the anti-TcR lines. The results demonstrate that the normal human immune system contains not only autoantigen-specific T cells, but also T cells that recognize antigenic determinants of autologous autoreactive TcR.

Amino Acid Sequence↗
PubMed1993

Predominant and stable T cell responses to regions of myelin basic protein can be detected in individual patients with multiple sclerosis.

T lymphocytes from patients with multiple sclerosis (MS) recognize multiple myelin basic protein (MBP) epitopes. This situation complicates the design of specific immunotherapies. We investigated to which extent the T cell response to MBP is heterogeneous in single subjects in terms of preferentially recognized regions of the molecule, major histocompatibility complex (MHC) restriction, and stability over time. From each of nine patients with MS, a minimum of six MBP-specific T lymphocyte lines (TLL) were assayed for the proliferative response to a panel of overlapping peptides, encompassing the whole MBP. Predominant T cell recognitions of distinct MBP regions were present in three patients, all HLA-DR2+, independently of the clinical features of their disease. T cell reactivity was preferentially directed to residues 16-38 in one patient. In this case the response was also stable over time, during different phases of the disease. Predominant reactivity to residues 86-99 was detected in the two other DR2+ patients. In each of the patients with other HLA-DR haplotypes (DR2-), as well as in three DR2+ non-MS donors, the T cell response to MBP appeared to be considerably more heterogeneous. The HLA restriction element varied among TLL recognizing the same MBP region, even when raised from the same individual. The genomic HLA typing, performed on the DRB1 and DRB5 genes in the DR2+ subjects, showed no obvious correspondence between preferential responses to regions of MBP and HLA-DR2 subtypes. In this context, a simple, new method for the genomic typing of the HLA-DRB1 gene in individuals with the HLA-DR2 serological specificity is also described. We conclude that predominant and stable T cell responses to a single MBP region can be detected in some patients with MS. In these individuals, the MHC restriction of the T cell recognition of predominant regions appears to be variable. Polymorphisms of the HLA-DR2 gene products alone do not account for the selection of the dominant MBP T cell epitope.

Adolescent↗
PubMed1993

T cells specific for the myelin oligodendrocyte glycoprotein mediate an unusual autoimmune inflammatory response in the central nervous system.

Myelin oligodendrocyte glycoprotein (MOG)-specific T cells mediate an autoimmune inflammatory response in the central nervous system (CNS) that differs radically from conventional models of T cell-mediated experimental allergic encephalomyelitis (EAE). Using synthetic peptides an encephalitogenic T cell epitope of MOG for the Lewis rat was identified within the extracellular IgG V-like domain of the protein, amino acids 44-53 (FSRVVHLYRN). The adoptive transfer of CD4+ T cells specific for this epitope induce an intense, dose-dependent inflammatory response in the CNS of naive syngeneic recipients. However, unlike the inflammatory response induced by myelin basic protein (MBP)-specific T cell lines, inflammation mediated by the MOG peptide-specific T cells failed to induce a gross neurological deficit. This unexpected observation was not due to a reduction in the overall inflammatory response in the CNS, but was specifically associated with a decrease in the extent of parenchymal (as opposed to perivascular) inflammation, a selective decrease in the number of ED1+ macrophages infiltrating the CNS, and a total lack of peripheral nerve inflammation. The decreased recruitment of macrophages into the CNS could not be ascribed to deficiencies in the synthesis of interferon-gamma, tumor necrosis factor-alpha, interleukin (IL)-6 or IL-2 by the T cell line. Moreover, this sub-clinical inflammatory response induced severe blood-brain barrier dysfunction as demonstrated by the induction of severe clinical disease following intravenous injection of a demyelinating MOG-specific monoclonal antibody. The neurological deficit in EAE thus exhibits an unexpected dependence on the identity of the target autoantigen, which determines the extent and nature of the local inflammatory response and ultimately the extent of the neurological deficit.

Amino Acid Sequence↗
PubMed1993

Microglial involvement in experimental autoimmune inflammation of the central and peripheral nervous system.

Microglial cells form a network of potential antigen presenting cells throughout the nervous system. Much progress has recently been made towards a better understanding of their immunological properties. This study examines their activation in 2 models of T cell-mediated autoimmune inflammation of the nervous system, experimental autoimmune encephalomyelitis (EAE) and its peripheral counterpart, experimental autoimmune neuritis (EAN), induced by the transfer of antigen-specific T cell lines. In both models microglial activation occurs at early stages of the disease. Activated microglial cells show an increased expression of MHC class I and II antigens. In EAE ultrastructural analysis revealed that MHC antigen expression is pronounced on perivascular microglial cells, suggesting this cell population may be important for antigen presentation at a site close to the blood-brain barrier. In contrast to EAE, the microglial reaction in EAN occurs at sites remote from the inflammatory response in the peripheral nerve, not only in the spinal cord but also in the terminal projection fields of primary sensory neurons in the lower brainstem. This early microglial activation in EAN suggests that a rapid and remote signaling mechanism can operate following peripheral inflammation. Immuno-electron microscopy revealed that activated microglial cells are also involved in the synaptic deafferentation of spinal cord motoneurons during autoimmune reactions. The rapid involvement of microglial cells in experimental autoimmune inflammation of the nervous system further points to their role as the main intrinsic immuneffector cell population of the central nervous system.

Animals↗
PubMed1993

The human granzyme A (HFSP, CTLA3) gene maps to 5q11-q12 and defines a new locus of the serine protease superfamily.

Human granzyme A (HFSP, Hanukah factor serine protease; CTLA3, cytotoxic T-lymphocyte-associated serine esterase-3), a homodimeric, trypsin-like serine protease of 60 kDa found in granules of cytolytic T cells and natural killer cells, is implicated in lymphocyte-mediated target cell lysis. It contributes to DNA fragmentation in perforin (PRF1)-lysed target cells through an unknown mechanism. We have isolated a cosmid clone for the functional gene of human granzyme A and established its complete exon-intron map of 10 kb. Using an 11-kb subfragment of the cloned genomic DNA as a probe, we have identified the chromosomal position of human granzyme A on 5q11-q12. Thus, the human granzyme A gene falls into a region of homology between human chromosome 5 and mouse chromosome 13, band D, where the mouse granzyme A gene has been located previously. The granzyme A gene is not linked to known members of the large superfamily of serine proteases.

Animals↗