Showing papers by "Reinhard Hohlfeld published in 2009"

MicroRNA profiling of multiple sclerosis lesions identifies modulators of the regulatory protein CD47

Abstract: We established microRNA profiles from active and inactive multiple sclerosis lesions. Using laser capture microdissection from multiple sclerosis lesions to pool single cells and in vitro cultures, we assigned differentially expressed microRNA to specific cell types. Astrocytes contained all 10 microRNA that were most strongly upregulated in active multiple sclerosis lesions, including microRNA-155, which is known to modulate immune responses in different ways but so far had not been assigned to central nervous system resident cells. MicroRNA-155 was expressed in human astrocytes in situ, and further induced with cytokines in human astrocytes in vitro. This was confirmed with astrocyte cultures from microRNA-155-|-lacZ mice. We matched microRNA upregulated in phagocytically active multiple sclerosis lesions with downregulated protein coding transcripts. This converged on CD47, which functions as a 'don't eat me' signal inhibiting macrophage activity. Three microRNA upregulated in active multiple sclerosis lesions (microRNA-34a, microRNA-155 and microRNA-326) targeted the 3'-untranslated region of CD47 in reporter assays, with microRNA-155 even at two distinct sites. Our findings suggest that microRNA dysregulated in multiple sclerosis lesions reduce CD47 in brain resident cells, releasing macrophages from inhibitory control, thereby promoting phagocytosis of myelin. This mechanism may have broad implications for microRNA-regulated macrophage activation in inflammatory diseases.

Contactin-2/TAG-1-directed autoimmunity is identified in multiple sclerosis patients and mediates gray matter pathology in animals

Abstract: Gray matter pathology is increasingly recognized as an important feature of multiple sclerosis (MS), but the nature of the immune response that targets the gray matter is poorly understood. Starting with a proteomics approach, we identified contactin-2/transiently expressed axonal glycoprotein 1 (TAG-1) as a candidate autoantigen recognized by both autoantibodies and T helper (Th) 1/Th17 T cells in MS patients. Contactin-2 and its rat homologue, TAG-1, are expressed by various neuronal populations and sequestered in the juxtaparanodal domain of myelinated axons both at the axonal and myelin sides. The pathogenic significance of these autoimmune responses was then explored in experimental autoimmune encephalitis models in the rat. Adoptive transfer of TAG-1–specific T cells induced encephalitis characterized by a preferential inflammation of gray matter of the spinal cord and cortex. Cotransfer of TAG-1–specific T cells with a myelin oligodendrocyte glycoprotein-specific mAb generated focal perivascular demyelinating lesions in the cortex and extensive demyelination in spinal cord gray and white matter. This study identifies contactin-2 as an autoantigen targeted by T cells and autoantibodies in MS. Our findings suggest that a contactin-2–specific T-cell response contributes to the development of gray matter pathology.

Multiple sclerosis: Human model for EAE?

Abstract: Concepts of the pathogenesis of MS are based on evidence from the animal model, EAE. Yet, the relationship between human MS and EAE is far from being a one-way road: many paths lead from the bedside back to animals in the laboratory.

Novel approaches for identifying target antigens of autoreactive human B and T cells

Abstract: Antigen-specific immune responses in multiple sclerosis have been studied for decades, but the target antigens of the putatively autoaggressive B and T cells still remain elusive. Here, we summarize recent strategies which are based on the direct analysis of biopsy or autopsy specimens from patients. Since this material is extremely scarce, the experimental methods need to be exceptionally sensitive. We describe technologies to distinguish (auto) aggressive T cells from irrelevant bystander lymphocytes by analyzing clonal expansions in relation to the morphological location of the cells in the tissue lesions. We then discuss approaches to clone matching α- and β-chains of the antigen-specific T cell receptor (TCR) molecules from single T cells. This is necessary because usually, several clones are expanded and are diluted by many irrelevant cells. The matching TCR chains from individual T cells can be resurrected in hybridoma cells which may then be used for antigen searches. We discuss strategies to identify antigens of γδ- and αβ-TCR molecules, such as biochemical methods, candidate antigens, human leukocyte antigen requirements, synthetic peptide, and cDNA libraries. These strategies are tailored to characterize the antigens of the membrane-anchored, low-affinity TCR molecules. The strategies to identify (auto) reactive B cells or immunoglobulin (Ig) molecules are fundamentally different, because Ig molecules are water-soluble and have high affinities. We further discuss proteome-based approaches, techniques that analyze Ig-chains from single B cells, and a repertoire-based method that compares Ig-proteomes and Ig-transcriptomes. The first method detects Ig antigens directly, whereas the latter two methods allow reconstruction of Ig molecules, which can be used for antigen searches.

Cross-reactive T-cell receptors in tumor and paraneoplastic target tissue.

Abstract: Background According to established criteria, paraneoplastic encephalomyelitis with adrenal neuroblastoma comprises a definite paraneoplastic neurologic syndrome. Objective To detect T-cell clones that cross-react against antigens shared between tumor and nervous system. Design Case study. Setting Academic research. Patient A 22-year-old woman having paraneoplastic encephalomyelitis with adrenal neuroblastoma. Main Outcome Measures We compared the T-cell receptor repertoires expressed in blood, cerebrospinal fluid, and neuroblastoma tumor tissue using complementary determining region 3 (CDR3) spectratyping and clone-specific polymerase chain reaction. Results The T-cell receptor repertoire in cerebrospinal fluid was narrow compared with that in tumor and blood. Four T-cell clones from different tissues had identical T-cell receptor β chains. Remarkably, the chains showed identical amino acid sequences but different nucleotide sequences. Conclusions These T cells represent ontogenetically distinct clones but share functionally identical receptors. They recognize the same antigen in nervous system and tumor tissue and represent an attractive target for selective therapy.

Therapie der Multiplen Sklerose mit monoklonalen Antikörpern

Abstract: Therapy of relapsing-remitting multiple sclerosis (MS) has become more effective, but this progress has unfortunately been associated with more serious risks. Since 3 years natalizumab has been licensed as the first monoclonal antibody for the treatment of a neurological autoimmune disease. In addition, there is now an increasing off-label use of rituximab and other monoclonal antibodies in a variety of immune-mediated neurological disorders. Experience and insights arising from applying these therapies will be used to define indications, logistics for monitoring treatment and adverse events, and some diagnostic and therapeutic algorithms for future innovative therapies for MS and their potential complications. This article is based on deliberations of a symposium held by an expert group of the German MS society (DMSG) which had a focus on natalizumab. In the future, when other novel therapeutic compounds are to be licensed, this work will be extended, updated and reported. This will help to improve the practical handling of potential complications of therapy in both inpatient and outpatient settings. A structured interaction between different levels of health-care providers will be an important part of establishing robust quality standards aiming at a high level of treatment safety. These structural aspects are addressed in a back-to-back article.