Biomedical subjects

H Lassmann

Publications and source records attributed to H Lassmann.

At least 145 records · Page 8Linked to original sources

PubMed1996

Evidence for neuronal apoptosis in pontosubicular neuron necrosis.

Pontosubicular neuron necrosis (PSN) is characterized by acute neuronal death in the subiculum and the pons occurring in a circumscribed perinatal period. The morphological changes in PSN are quite similar to those described during apoptosis, a form of programmed cell death. Morphological re-evaluation of the lesions by light and electron microscopy revealed the typical changes of apoptosis with condensed basophilic nuclei and the formation of apoptotic bodies. By analysing DNA fragmentation in situ with a recently established technique, we were able to show that neuronal death in PSN is apoptotic. The demonstration of DNA fragmentation by the in situ tailing technique was reliable in the human autopsy material used in this study and was only slightly affected by autolysis or formalin fixation. The subiculum and the pons are shown to be susceptible to apoptosis at different times during development. PSN thus provides a model in which the process of nerve cell apoptosis in the developing human central nervous system can be studied.

Apoptosis↗

PubMed1996

Changes of extracellular space volume and tortuosity in the spinal cord of Lewis rats with experimental autoimmune encephalomyelitis.

Three diffusion parameters of nervous tissue, extracellular space (ECS) volume fraction (alpha), tortuosity (gamma) and non-specific uptake (k') of tetramethylammonium (TMA+), were studied in the spinal cord of rats during experimental autoimmune encephalomyelitis (EAE). The three parameters were determined in vivo from concentration-time profiles of TMA+ using ion-selective microelectrodes. EAE was induced by injection of guinea-pig myelin basic protein (MBP), which resulted in typical morphological changes in the CNS tissue, namely inflammatory reaction, astrogliosis, blood-brain barrier (BBB) damage and paralysis. EAE was accompanied by a statistically significant increase of alpha (mean +/- S.E.M.) in the dorsal horn from 0.21 +/- 0.01 to 0.28 +/- 0.02, in the intermediate region from 0.22 +/- 0.01 to 0.33 +/- 0.02, in the ventral horn from 0.23 +/- 0.01 to 0.47 +/- 0.02 and in white matter from 0.18 +/- 0.03 to 0.30 +/- 0.03. There were significant decreases in tortuosity in the dorsal horn and in the intermediate region and decreases in non-specific uptake in the intermediate region and in the ventral horn. Although the inflammatory reaction and the astrogliosis preceded and greatly outlasted the neurological symptoms, the BBB damage had a similar time course. Moreover, there was a close correlation between the changes in extracellular space diffusion parameters and the manifestation of neurological signs. We suggest that the expansion of the extracellular space alters the diffusion properties in the spinal cord. This may affect synaptic as well as non-synaptic transmission, intercellular communication and recovery from acute EAE, and may contribute to the manifestation of neurological signs in EAE rats.

Animals↗

PubMed1996

[Pathogenesis of multiple sclerosis and other neural autoimmune diseases].

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system. Its pathological hallmark is the demyelinated plaque with reactive glial scarring. Recent neuropathological and immunopathological data suggest a pronounced pathologic heterogeneity of MS plaques. Although demyelination is present in all lesions, the extent of oligodendroglia loss, remyelination and axonal pathology is highly variable. In the present review, data are discussed on the fate of myelin forming cells in MS lesions, which suggest that fundamentally different immunological mechanisms may be involved in the formation of the lesions in different MS patients. Possible immunopathogenetic mechanisms are discussed by comparing the different types of MS lesions with those described in different experimental models of inflammatory demyelinating disease.

Animals↗

PubMed1996

[Perspectives in multiple sclerosis research].

There is little doubt that multiple sclerosis (MS) is an immune mediated disease, yet the exact immunological mechanisms, that are responsible for inflammation and demyelination in this disease are controversial. Recent evidence is summarized here, which suggests that heterogeneous pathogenetic mechanisms may lead to the inflammatory demyelinating plaques in different MS patients. This heterogeneity apparently involves the antigen specificity of the immune response as well as the mechanisms, responsible for the destruction of myelin sheaths. Since such a pathogenetic heterogeneity may have consequences for the design of therapeutic studies, strategies are discussed, which should allow a more accurate categorization of patient sub-groups in the future.

Autoantibodies↗

PubMed1995

The small heat-shock protein alpha B-crystallin as candidate autoantigen in multiple sclerosis.

The identification of key antigens in human autoimmune diseases is a crucial step towards the development of specific intervention. The autoantigen(s) relevant to multiple sclerosis (MS) probably reside in myelin of the central nervous system, the target of the disease. Here we examine proliferative responses of human peripheral blood T cells to the complete collection of myelin proteins fractionated by reversed-phase high-performance liquid chromatography. Myelin isolated from MS-affected brain contained a single protein fraction to which T cells from MS patients and from healthy controls showed dominant responses. This highly immunogenic protein was identified as alpha B-crystallin, a small heat-shock protein. Immunohistochemical examination of MS lesions revealed the presence of oligodendrocytes and astrocytes with raised alpha B-crystallin expression, which were not found in unaffected myelin. Our findings indicate that alpha B-crystallin serves as immunodominant myelin antigen to human T cells when expressed at the elevated levels found in active MS lesions.

Astrocytes↗

PubMed1995

Monocyte/macrophage differentiation in early multiple sclerosis lesions.

Monocyte/macrophage differentiation was studied in biopsy samples of multiple sclerosis (MS) lesions obtained in the early course of the disease. Macrophages were identified by immunocytochemistry using a panel of antibodies recognizing different macrophage-activation antigens. The number of cells stained with each antibody was related to the demyelinating activity of the lesions as detected by the presence of myelin degradation products. The pan-macrophage marker Ki-M1P revealed the highest numbers of macrophages in early and late active lesions. Lower numbers were encountered in inactive, demyelinated, or remyelinated lesions. The acute stage inflammatory macrophage markers MRP14 and 27E10 were expressed in either only early active (MRP14) or early and late active (27E10) lesions, thus allowing the identification of actively demyelinating lesions. The chronic stage inflammatory macrophage marker 25F9, in contrast, showed increasing expression with decreasing lesional activity. These findings indicate a differentiated pattern of macrophage activation in MS lesions and allow the staging of demyelinating lesions in routinely fixed and paraffin-embedded tissue.

Adolescent↗

PubMed1995

Resident microglia and hematogenous macrophages as phagocytes in adoptively transferred experimental autoimmune encephalomyelitis: an investigation using rat radiation bone marrow chimeras.

Hematogenous macrophages are known to be involved in the induction of tissue damage in the central nervous system (CNS) as well as of clinical symptoms in experimental autoimmune encephalomyelitis (EAE). Although resident microglia can become phagocytic under certain circumstances, little is known about the role of these cells in brain inflammation in vivo. We thus studied EAE in the model of radiation bone marrow chimeras that allows us to distinguish donor-derived hematogenous cells from resident effector cells. Inflammation in the CNS was qualitatively and quantitatively similar in chimeras compared to fully histocompatible Lewis rats. Although activated resident microglial cells were outnumbered four- to sevenfold in EAE lesions by hematogenous macrophages, the number of resident microglia with ingested myelin was equal to that of macrophages containing myelin debris. Phagocytic resident microglia, expressing the macrophage activation marker ED1, showed ramified as well as amoeboid morphology. From our studies the following conclusions can be drawn. First, a considerable proportion of resident microglia upregulated ED1. Second, resident microglia provide a small but substantial source of brain macrophages in EAE as compared to the large influx of macrophages. Third, our results suggest that microglia, due to their strategic position within the CNS, are more effective in removal of myelin debris compared to hematogenous macrophages.

Animals↗

PubMed1995

The role of macrophages, perivascular cells, and microglial cells in the pathogenesis of experimental autoimmune encephalomyelitis.

Clinical signs of experimental autoimmune encephalomyelitis (EAE) in rats can be suppressed by treatment with liposomes containing dichloromethylene diphosphonate (Cl2MDP liposomes). Here we investigated whether besides the blood-borne macrophages also ED2+ perivascular cells and microglia are affected by this treatment. For this purpose we examined the central nervous system of bone marrow chimeras in which EAE was induced with encephalitogenic T cells. Quantification of cell numbers of various cell types in inflammatory lesions in the spinal cord showed that after treatment with Cl2MDP liposomes more than 95% of the bone marrow derived (I1-69+) macrophages were eliminated. In addition the number of ED2+ perivascular cells were seen to be decreased by 68% as compared to ED2+ cells in control liposome treated animals. However the number of these perivascular cells in Cl2MDP liposome treated animals did not differ from the number of perivascular cells in naive animals, indicating that only newly recruited, inflammation associated, ED2+ macrophages were eliminated. Moreover, detection of degenerating nuclei by in situ nick translation (ISNT) in combination with staining for ED1 or ED2 showed that in the perivascular space no degenerating cells were present. Cl2MDP liposome treatment furthermore decreased the numbers of T cells infiltrating the parenchyma by more than 50%. Instead T cells were found in large numbers in the perivascular space. Microglia did not seem to be eliminated by Cl2MDP liposome treatment as shown by the absence of ED1+/ISNT+ cells in the CNS parenchyma. However the number of ED1+ (I1-69-) microglial cells decreased by more than 80%, indicating that the activation of this cell type was impaired. It is concluded that bone marrow derived macrophages play an important role in the pathogenesis of EAE via interactions with lymphocytes and the activation of resident microglia.

Animals↗

PubMed1995

Are current immunological concepts of multiple sclerosis reflected by the immunopathology of its lesions?

Immunopathological studies on multiple sclerosis (MS) brain clearly indicate that a T cell-mediated immune response is the driving force in the induction of the lesions. This T cell-mediated response alone, however, is not sufficient to explain the widespread and selective destruction of myelin sheaths. According to present evidence, it is likely that antibodies directed against surface components of myelin sheaths are at least one factor involved in the demyelinating process. The patterns of inflammation, demyelination and oligodendrocyte destruction, however, suggest that the pathogenesis of the lesions may be fundamentally different in individual MS patients and that autoimmunity may not be the sole cause. In the case of autoimmune reactions various different proteins of the nervous system may become targets and it appears unlikely, that myelin basic protein is a major candidate for a pathogenetic role in MS.

Humans↗

PubMed1995

Cell death in Alzheimer's disease evaluated by DNA fragmentation in situ.

Loss of nerve cells is a hallmark of the pathology of Alzheimer's disease (AD), yet the patterns of cell death are unknown. By analyzing DNA fragmentation in situ we found evidence for cell death not only of nerve cells but also of oligodendrocytes and microglia in AD brains. In average, 30 times more brain cells showed DNA fragmentation in AD as compared to age-matched controls. Nuclear alterations suggestive of apoptosis were rare in degenerating cells. Even though the majority of degenerating cells were not located within amyloid deposits and did not contain neurofibrillary tangles, neurons situated within areas of amyloid deposits or affected by neurofibrillary degeneration revealed a higher risk of DNA fragmentation and death than cells not exposed to these AD changes.

Aged↗

PubMed1995

Diffuse Lewy body disease as substrate of primary lateral sclerosis.

We describe the case of a 40-year-old male patient who had presented clinically as primary lateral sclerosis for the past 10 years and neuropathologically as diffuse Lewy body disease (DLBD). Neuropathology demonstrated DLBD as an almost ubiquitous disorder of the neuronal cytoskeleton.

Adult↗

PubMed1995

The N-terminal domain of the myelin oligodendrocyte glycoprotein (MOG) induces acute demyelinating experimental autoimmune encephalomyelitis in the Lewis rat.

Using a highly purified recombinant protein, mMOG, we demonstrated that autoimmune responses to the N-terminal domain (a.a 1-125) of the myelin oligodendrocyte glycoprotein (MOG) induce an acute demyelinating variant of experimental autoimmune encephalomyelitis (EAE) in the Lewis rat. Immunisation with 100 micrograms of mMOG in adjuvant at the base of the tail induced mild clinical disease in 9 of 11 animals (mean clinical score 1.1). The disease was characterised histopathologically by the presence of inflammation and focal demyelinating lesions in the central nervous system (CNS). Adoptive transfer experiments suggest that this inflammatory demyelinating pathology is mediated by synergy between a weakly encephalitogenic, MOG-specific T cell response and a demyelinating, MOG-specific autoantibody response. Using in vitro selected mMOG-reactive T cell lines, the encephalitogenic T cell response to this domain of MOG was found to recognise two distinct epitopes, MOG1-20 and MOG35-55; whereas ELISA demonstrated that the immunodominant B cell epitope was located within the amino acid sequence MOG1-25. However although active immunisation with synthetic peptides corresponding to the T cell epitopes, MOG1-20 or MOG35-55, induced an inflammatory response in the CNS, this was not associated with demyelination indicating that the demyelinating antibody response recognises other, possibly conformation dependent epitopes. This study unequivocally demonstrates that MOG-specific autoimmune responses are alone sufficient to induce a demyelinating disease of the CNS and supports the proposal that MOG may play an important role in the immunopathogenesis of multiple sclerosis.

Amino Acid Sequence↗

PubMed1995

Apoptosis in brain-specific autoimmune disease.

Recent neuropathological studies of experimental autoimmune encephalomyelitis have focused attention on the high number of cells in the lesions that show typical morphological features of apoptosis. Surprisingly, it has turned out that the vast majority of apoptotic cells are T lymphocytes and that they actually represent the antigen-specific T-cell population responsible for the induction of the disease. Taken together, these data suggest that clearance of autoimmune inflammation in the nervous system is accomplished by the destruction of the antigen-specific T-cell population within the lesions. This may explain the low level of central nervous system specific T-cell memory formation, as well as previously unexplained phenomena of 'epitope spreading', in autoimmune inflammation of the nervous system.

Animals↗

PubMed1995

Coronavirus-induced encephalomyelitis: balance between protection and immune pathology depends on the immunization schedule with spike protein S.

The neurotropic mouse hepatitis virus MHV-JHM induces central nervous system (CNS) demyelination in Lewis rats that pathologically resembles CNS lesions in multiple sclerosis. The mechanisms of MHV-JHM-induced demyelination remain unclear and several studies have implicated the role of the immune response in this process. We have shown previously that protective immunity against MHV-JHM-induced encephalomyelitis was induced by immunization with a vaccinia virus (VV) recombinant expressing MHV-JHM S-protein (VV-S). Here, we present evidence that the time of MHV-JHM challenge after immunization with VV-S plays a critical role in protective immunity. The induction of virus-neutralizing S-protein-specific antibodies prior to the MHV-JHM challenge modulates the disease process and a subacute encephalomyelitis based on a persistent virus infection developed. Typical pathological alterations were lesions of inflammatory demyelination. In addition, the results indicate that after seroconversion, CD8+ T cells were no longer essential for virus elimination in contrast to their role in protection during acute encephalomyelitis.

Animals↗

PubMed1995

Thyroid epithelial cells produce large amounts of the Alzheimer beta-amyloid precursor protein (APP) and generate potentially amyloidogenic APP fragments.

The Alzheimer beta-amyloid precursor protein (APP) is a transmembrane glycoprotein from which the amyloid beta-protein is proteolytically derived. The latter is a hydrophobic peptide that can aggregate and forms the core of the senile plaques found in the brains of patients suffering from Alzheimer's disease (AD). In view of the known association between familial AD and thyroid autoimmune disease, the expression pattern and cellular processing of APP in human thyroid cells were investigated. Cultured thyroid epithelial cells and homogenized thyroid tissue from normal and pathological thyroid samples were analyzed by immunoblotting using specific N- and C-terminal APP antibodies as well as by reverse transcription-polymerase chain reaction in which two sets of oligonucleotide primers were used. The results of these studies demonstrated that APP isoforms 770 and 751 were expressed in fresh thyroid extracts as well as in cultured thyroid epithelial cells, with APP 770 being the predominant form. Compared to other types of cells, such as lymphocytes and fibroblasts, thyroid epithelial cells produced larger amounts of APP. Most of the mature protein was cleaved within the amyloid beta region, as a result of which a large N-terminal APP fragment was released into the culture medium, whereas a C-terminal nonamyloidogenic fragment of 14 kilodaltons (kDa) was retained within the cell. Interestingly, thyroid epithelial cells also contained larger C-terminal APP fragments of 21, 35, and 41 kDa. From the sizes of these fragments it could be deduced that they contained the entire amyloid beta sequence and were thus potentially amyloidogenic. The 41-kDa fragment was unique to thyroid cells. These fragments may be released into the circulation after thyroid cell damage. Increased/altered thyroid APP expression in familiar AD may induce alterations in thyroid epithelial cells and cell damage, and thus explain the frequent occurrence of thyroid autoimmunity in this disease.

Adult↗

PubMed1995

Detection of tumor necrosis factor-alpha protein and messenger RNA in human glial brain tumors: comparison of immunohistochemistry with in situ hybridization using molecular probes.

Tumor necrosis factor-alpha (TNF alpha) protein and messenger (m)RNA distribution was studied in biopsy samples of glial brain tumors, using immunohistochemistry and in situ hybridization with molecular probes, to investigate the role of this cytokine in tumor proliferation and immunological host defense. Focal expression of TNF alpha was detected in four of four glioblastomas, one of two anaplastic astrocytomas, and four of five low-grade astrocytomas, regardless of their subtype or grade of malignancy, but in none of the normal peritumoral brain tissues used as controls. The TNF alpha protein and mRNA were present in reactive astrocytes and protoplasmic tumor cells, confined to areas of leukocyte or T-lymphocyte infiltrating, and less pronounced in tumor cells at the edge of necrosis. Additionally, TNF alpha reactivity was found in infiltrating macrophages and perivascular microglia. Immunohistochemistry and in situ hybridization for TNF alpha showed comparable reaction patterns and numbers of TNF alpha-positive cells, even though the sensitivity of in situ hybridization was significantly higher. Quantitative evaluation of TNF alpha protein, TNF alpha mRNA, and leukocyte infiltration revealed a significant positive correlation between the TNF alpha-positive reactive astrocytes and the number of lymphocytes present in corresponding areas. Together, these data lead to the conclusion that TNF alpha in reactive astrocytes and monocytic cells within tumor areas of high leukocyte infiltration and in tumor cells at the border of necrosis may represent one defense pathway of the immune system against tumor proliferation.

Adolescent↗

PubMed1994

Experimental autoimmune panencephalitis and uveoretinitis transferred to the Lewis rat by T lymphocytes specific for the S100 beta molecule, a calcium binding protein of astroglia.

The pathogenic potential of autoimmune T cell responses to nonmyelin autoantigens was investigated in the Lewis rat using the astrocyte-derived calcium binding protein S100 beta, as a model nonmyelin autoantigen. The Lewis rat mounts a vigorous RT1B1 (major histocompatibility complex class II) restricted autoimmune response to an immunodominant S100 beta epitope (amino acid residues 76-91). The adoptive transfer of S100 beta-specific T cell lines induced a severe inflammatory response in the nervous system, but only minimal neurological dysfunction in naive syngeneic recipients. The inability of S100 beta-specific T cell transfer to induce severe disease was associated with a decreased recruitment of ED1+ macrophages into the central nervous system (CNS) in comparison with that seen in severe experimental autoimmune encephalomyelitis (EAE) induced by the adoptive transfer of myelin basic protein (MBP)-specific T line cells. Moreover, unlike encephalitogenic MBP-specific T cell lines, S100 beta-specific T cell lines exhibited no cytotoxic activity in vitro. Histopathological analysis also revealed striking differences in the distribution of inflammatory lesions in MBP- and S100 beta-specific T cell-mediated disease. In contrast to the MBP paradigm, S100 beta-specific T cell transfer induces intense inflammation not only in the spinal cord, but throughout the entire CNS and also in the uvea and retina of the eye. In view of the distribution of lesions throughout the grey and white matter of the CNS we propose to term this new model experimental autoimmune panencephalomyelitis (EAP) to differentiate it from EAE. These experiments demonstrate for the first time that nonmyelin CNS autoantigens can initiate a pathogenic autoimmune T cell response, although the nature of the target autoantigen profoundly influences the clinical and histopathological characteristics of the resulting autoimmune disease. This is not simply a consequence of the distribution of the autoantigen, as both MBP and S100 beta are coexpressed in many areas of the CNS, but reflects differences in the capacity of different regions of the CNS to process and present specific autoantigens. This new model of T cell-mediated autoimmune CNS disease exhibits a number of similarities to multiple sclerosis (MS), such as its mild clinical course and the involvement of areas of the brain and eye, which are absent in myelin-mediated models of EAE. Nonmyelin autoantigens may therefore play an unexpectedly important role in the immunopathogenesis of inflammatory diseases of the CNS.

Amino Acid Sequence↗

PubMed1994

Soluble recombinant complement receptor 1 inhibits inflammation and demyelination in antibody-mediated demyelinating experimental allergic encephalomyelitis.

Activation of complement may contribute to tissue damage in many inflammatory diseases, including those that are clearly T cell driven. We have previously provided evidence that C is involved in tissue damage in multiple sclerosis and in the animal models of this disease, experimental allergic encephalomyelitis and Ab-mediated demyelinating experimental allergic encephalomyelitis, the latter being a model more closely resembling multiple sclerosis. The development of a soluble recombinant form of human complement receptor 1 (sCR1) with potent C-inhibiting activity both in vitro and in vivo provides a potential means of preventing C-mediated tissue damage in animal models and in human disease. Here, we describe the effects of this agent on clinical disease and pathology in Ab-mediated demyelinating experimental allergic encephalomyelitis in the rat. Daily i.p. injection of sCR1 (20 mg/kg) over 6 days completely suppressed serum C activity, reduced the severity of clinical disease (clinical score 1.33 vs 2.79 in untreated animals), inhibited central nervous system inflammation (inflammatory index 2.76 vs 6.55), and almost completely blocked demyelination (average 2.43% cord cross-section vs 8.81%). Deposition of C components C1, C3, and C9 was also markedly inhibited in sCR1-treated animals. This dramatic effect on a demyelinating disease, achieved using a well-tolerated biologic reagent, offers an exciting new prospect for therapy in multiple sclerosis.

Animals↗