Publications by authors named "Christine Baksmeier"

6 Publications

  • Page 1 of 1

Modified recombinant human IgG1-Fc is superior to natural intravenous immunoglobulin at inhibiting immune-mediated demyelination.

Immunology 2021 Apr 20. Epub 2021 Apr 20.

Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, UK.

Intravenous immunoglobulin (IVIG) is an established treatment for numerous autoimmune conditions. Although Fc fragments derived from IVIG have shown efficacy in controlling immune thrombocytopenia in children, the mechanisms of action are unclear and controversial. The aim of this study was to dissect IVIG effector mechanisms using further adapted Fc fragments on demyelination in an ex vivo model of the central nervous system-immune interface. Using organotypic cerebellar slice cultures (OSCs) from transgenic mice, we induced extensive immune-mediated demyelination and oligodendrocyte loss with an antibody specific for myelin oligodendrocyte glycoprotein (MOG) and complement. Protective effects of adapted Fc fragments were assessed by live imaging of green fluorescent protein expression, immunohistochemistry and confocal microscopy. Cysteine- and glycan-adapted Fc fragments protected OSC from demyelination in a dose-dependent manner where equimolar concentrations of either IVIG or control Fc were ineffective. The protective effects of the adapted Fc fragments are partly attributed to interference with complement-mediated oligodendroglia damage. Transcriptome analysis ruled out signatures associated with inflammatory or innate immune responses. Taken together, our findings show that recombinant biomimetics can be made that are at least two hundred-fold more effective than IVIG in controlling demyelination by anti-MOG antibodies.
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http://dx.doi.org/10.1111/imm.13341DOI Listing
April 2021

Protective effects of 4-aminopyridine in experimental optic neuritis and multiple sclerosis.

Brain 2020 04;143(4):1127-1142

NeuroCure Clinical Research Center and Experimental and Clinical Research Center, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health and Max Delbrueck Center for Molecular Medicine, Berlin, Germany.

Chronic disability in multiple sclerosis is linked to neuroaxonal degeneration. 4-aminopyridine (4-AP) is used and licensed as a symptomatic treatment to ameliorate ambulatory disability in multiple sclerosis. The presumed mode of action is via blockade of axonal voltage gated potassium channels, thereby enhancing conduction in demyelinated axons. In this study, we provide evidence that in addition to those symptomatic effects, 4-AP can prevent neuroaxonal loss in the CNS. Using in vivo optical coherence tomography imaging, visual function testing and histologic assessment, we observed a reduction in retinal neurodegeneration with 4-AP in models of experimental optic neuritis and optic nerve crush. These effects were not related to an anti-inflammatory mode of action or a direct impact on retinal ganglion cells. Rather, histology and in vitro experiments indicated 4-AP stabilization of myelin and oligodendrocyte precursor cells associated with increased nuclear translocation of the nuclear factor of activated T cells. In experimental optic neuritis, 4-AP potentiated the effects of immunomodulatory treatment with fingolimod. As extended release 4-AP is already licensed for symptomatic multiple sclerosis treatment, we performed a retrospective, multicentre optical coherence tomography study to longitudinally compare retinal neurodegeneration between 52 patients on continuous 4-AP therapy and 51 matched controls. In line with the experimental data, during concurrent 4-AP therapy, degeneration of the macular retinal nerve fibre layer was reduced over 2 years. These results indicate disease-modifying effects of 4-AP beyond symptomatic therapy and provide support for the design of a prospective clinical study using visual function and retinal structure as outcome parameters.
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http://dx.doi.org/10.1093/brain/awaa062DOI Listing
April 2020

NMDAR encephalitis: passive transfer from man to mouse by a recombinant antibody.

Ann Clin Transl Neurol 2017 11 3;4(11):768-783. Epub 2017 Oct 3.

Department of Neurology Medical Faculty Heinrich Heine University Düsseldorf Düsseldorf Germany.

Objective: Autoimmune encephalitis is most frequently associated with anti-NMDAR autoantibodies. Their pathogenic relevance has been suggested by passive transfer of patients' cerebrospinal fluid (CSF) in mice in vivo. We aimed to analyze the intrathecal plasma cell repertoire, identify autoantibody-producing clones, and characterize their antibody signatures in recombinant form.

Methods: Patients with recent onset typical anti-NMDAR encephalitis were subjected to flow cytometry analysis of the peripheral and intrathecal immune response before, during, and after immunotherapy. Recombinant human monoclonal antibodies (rhuMab) were cloned and expressed from matching immunoglobulin heavy- (IgH) and light-chain (IgL) amplicons of clonally expanded intrathecal plasma cells (cePc) and tested for their pathogenic relevance.

Results: Intrathecal accumulation of B and plasma cells corresponded to the clinical course. The presence of cePc with hypermutated antigen receptors indicated an antigen-driven intrathecal immune response. Consistently, a single recombinant human GluN1-specific monoclonal antibody, rebuilt from intrathecal cePc, was sufficient to reproduce NMDAR epitope specificity in vitro. After intraventricular infusion in mice, it accumulated in the hippocampus, decreased synaptic NMDAR density, and caused severe reversible memory impairment, a key pathogenic feature of the human disease, in vivo.

Interpretation: A CNS-specific humoral immune response is present in anti-NMDAR encephalitis specifically targeting the GluN1 subunit of the NMDAR. Using reverse genetics, we recovered the typical intrathecal antibody signature in recombinant form, and proved its pathogenic relevance by passive transfer of disease symptoms from man to mouse, providing the critical link between intrathecal immune response and the pathogenesis of anti-NMDAR encephalitis as a humorally mediated autoimmune disease.
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http://dx.doi.org/10.1002/acn3.444DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5682115PMC
November 2017

Dose-dependent inhibition of demyelination and microglia activation by IVIG.

Ann Clin Transl Neurol 2016 11 23;3(11):828-843. Epub 2016 Sep 23.

Department of Neurology, Medical Faculty Heinrich-Heine-University Duesseldorf Moorenstr. 5 D-40225 Duesseldorf Germany.

Objective: Intravenous immunoglobulin (IVIG) is an established treatment for numerous autoimmune conditions. Clinical trials of IVIG for multiple sclerosis, using diverse dose regimens, yielded controversial results. The aim of this study is to dissect IVIG effector mechanisms on demyelination in an model of the central nervous system (CNS)-immune interface.

Methods: Using organotypic cerebellar slice cultures (OSC) from transgenic mice expressing green fluorescent protein (GFP) in oligodendrocytes/myelin, we induced extensive immune-mediated demyelination and oligodendrocyte loss with an antibody specific for myelin oligodendrocyte glycoprotein (MOG) and complement. Protective IVIG effects were assessed by live imaging of GFP expression, confocal microscopy, immunohistochemistry, gene expression analysis and flow cytometry.

Results: IVIG protected OSC from demyelination in a dose-dependent manner, which was at least partly attributed to interference with complement-mediated oligodendroglia damage, while binding of the anti-MOG antibody was not prevented. Staining with anti-CD68 antibodies and flow cytometry confirmed that IVIG prevented microglia activation and oligodendrocyte death, respectively. Equimolar IVIG-derived Fab fragments or monoclonal IgG did not protect OSC, while Fc fragments derived from a polyclonal mixture of human IgG were at least as potent as intact IVIG.

Interpretation: Both intact IVIG and Fc fragments exert a dose-dependent protective effect on antibody-mediated CNS demyelination and microglia activation by interfering with the complement cascade and, presumably, interacting with local immune cells. Although this experimental model lacks blood-brain barrier and peripheral immune components, our findings warrant further studies on optimal dose finding and alternative modes of application to enhance local IVIG concentrations at the site of tissue damage.
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http://dx.doi.org/10.1002/acn3.326DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5099529PMC
November 2016

Epigallocatechin gallate (EGCG) inhibits adhesion and migration of neural progenitor cells in vitro.

Arch Toxicol 2017 Feb 26;91(2):827-837. Epub 2016 Apr 26.

IUF - Leibniz Research Institute for Environmental Medicine, Auf'm Hennekamp 50, 40225, Düsseldorf, Germany.

Food supplements based on herbal products are widely used during pregnancy as part of a self-care approach. The idea that such supplements are safe and healthy is deeply seated in the general population, although they do not underlie the same strict safety regulations than medical drugs. We aimed to characterize the neurodevelopmental effects of the green tea catechin epigallocatechin gallate (EGCG), which is now commercialized as high-dose food supplement. We used the "Neurosphere Assay" to study the effects and unravel underlying molecular mechanisms of EGCG treatment on human and rat neural progenitor cells (NPCs) development in vitro. EGCG alters human and rat NPC development in vitro. It disturbs migration distance, migration pattern, and nuclear density of NPCs growing as neurospheres. These functional impairments are initiated by EGCG binding to the extracellular matrix glycoprotein laminin, preventing its binding to β1-integrin subunits, thereby prohibiting cell adhesion and resulting in altered glia alignment and decreased number of migrating young neurons. Our data raise a concern on the intake of high-dose EGCG food supplements during pregnancy and highlight the need of an in vivo characterization of the effects of high-dose EGCG exposure during neurodevelopment.
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http://dx.doi.org/10.1007/s00204-016-1709-8DOI Listing
February 2017

Automatic counting and positioning of 5-bromo-2-deoxyuridine (BrdU) positive cells in cortical layers of rat brain slices.

Neurotoxicology 2014 Jul 23;43:127-133. Epub 2014 Feb 23.

IUF - Leibniz Research Institute for Environmental Medicine, Auf'm Hennekamp 50, 40225 Düsseldorf, Germany. Electronic address:

5-Bromo-2-deoxyuridine (BrdU) staining is often used to evaluate cortical layer formation during mammalian brain development. This method allows the quantification of newly generated cells and therefore the study of the effects of xenobiotics or genetic factors on proliferation, cell death and migration behavior in a quantitative manner. However, these endpoints are generally assessed by time-consuming manual evaluation. In the present work, we introduce a novel procedure to identify and quantify BrdU(+) cells within cortical layers, using the commercially available vHCS-Scan V.6.3.1 software to identify BrdU(+) cell coordinates and the novel program 'BrdeLuxe' to define cortical layers and quantitatively assign BrdU(+) cells to them. This procedure is compared to BrdU(+) cell counting with the freeware 'ImageJ' in respect to the manual evaluation, all by two different researchers. BrdeLuxe shows high accuracy and precision for the determination of total number of BrdU(+) cells compared to the manual counting, while ImageJ does not reach such results. Accuracy and precision are also higher for employing the BrdeLuxe program to evaluate the percentage of BrdU(+) cells per brain layer compared to ImageJ. In terms of running time, BrdeLuxe is the fastest method of the three making it more suitable for multiple brain slices analyses.
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http://dx.doi.org/10.1016/j.neuro.2014.02.005DOI Listing
July 2014