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Biomedical subjects

R M Ransohoff

Publications and source records attributed to R M Ransohoff.

At least 109 records · Page 6Linked to original sources
PubMed1993

In vitro and in vivo inhibition of mitogen-driven T-cell activation by recombinant interferon beta.

Recombinant interferon beta (rIFN beta) is being tested as experimental immunotherapy for exacerbating-remitting MS. To clarify the possible mechanisms of a therapeutic response to rIFN beta in MS patients, we conducted studies on the effects of rIFN beta on mitogen-driven T-cell activation by stimulating peripheral blood mononuclear cells (PBMC) with concanavalin A (ConA) or with anti-CD3 monoclonal antibodies in the presence or absence of rIFN beta. We monitored T-cell activation using proliferation assays or by expression of surface activation markers detected by flow cytometry. In vitro rIFN beta, in concentrations > or = 10 U/ml, inhibited PBMC proliferation or surface expression of interleukin-2 receptor (IL-2R), transferrin receptor, or CD2. In contrast, rIFN gamma augmented mitogen-driven IL-2R expression. PBMC isolated from normal volunteers or MS patients responded to ConA and rIFN beta in a similar manner. We conducted pilot in vivo studies in exacerbating-remitting MS patients participating in a double-blind placebo-controlled clinical trial of rIFN beta. PBMC were isolated from study participants immediately before and 24 hours after a weekly study injection. IL-2R expression by T cells was determined following a ConA stimulus. While there was no significant change following placebo injection, rIFN beta recipients showed significantly reduced ConA-driven IL-2R expression following study injection. The results document in vitro and in vivo inhibition of mitogen-driven T-cell activation by rIFN beta. This suggests a possible mechanism underlying a therapeutic response to rIFN beta in MS patients.

Antibodies, Monoclonal↗
PubMed1992

Transforming growth factor-beta 1 differentially regulates proliferation and MHC class-II antigen expression in forebrain and brainstem astrocyte primary cultures.

To facilitate investigation of cytokine regulation of reactive astrogliosis, primary astrocyte cultures from neonatal murine forebrain and brainstem were established. Forebrain and brainstem astrocytes proliferated at a similar rate under basal culture conditions, and both were growth-inhibited by treatment with recombinant murine interferon-gamma. The growth of cultured brainstem astrocytes was significantly enhanced by exposure to recombinant human transforming growth factor-beta 1. In contrast, proliferation of forebrain astrocytes was not significantly affected by transforming growth factor-beta 1. The disparate responses of brainstem and forebrain astrocytes to transforming growth factor-beta 1 treatment were not limited to effects on cell growth, since transforming growth factor-beta 1 could block interferon-gamma-induced MHC class-II antigen expression on cultured brainstem astrocytes but not on forebrain cells. Results could not be attributed to use of an heterologous cytokine/cellular target system, since similar variability in transforming growth factor-beta 1 modulation of major histocompatibility complex antigen expression could be demonstrated using two human astrocytoma cell lines. This report is the first to document mitogenic response to transforming growth factor-beta 1 for neuroepithelial cells. The role of transforming growth factor-beta 1 in regulating aspects of reactive astrogliosis, particularly in the context of inflammatory demyelination, requires further investigation. Furthermore, these studies may provide insight into regional variability in the sequelae of inflammation within the central nervous system.

Animals↗
PubMed1992

Cytokine secretion by multiple sclerosis monocytes. Relationship to disease activity.

Autoantigen recognition by specific T cells may initiate a tissue-specific immune response in multiple sclerosis (MS), which is a chronic inflammatory demyelinating disorder. During subsequent nonspecific immune amplification, interleukin 1 beta and tumor necrosis factor alpha are released by cells of the monocyte/macrophage lineage, with the potential to influence profoundly immune regulation systemically or within the central nervous system. Regulation of monocyte inflammatory gene expression may be relevant to the pathogenesis of MS. We investigated spontaneous secretion of interleukin 1 beta, tumor necrosis factor alpha, and prostaglandin E2 with the use of monocytes that we isolated from patients with active (n = 9) and stable (n = 9) MS and from age-matched normal controls (n = 9). The patient groups with MS were matched for age, duration of MS, and disease severity. Patients with active disease were within weeks of the onset of a clinical exacerbation. Monocytes were isolated by density gradient centrifugation, followed by adherence to plastic tissue culture flasks, resulting in a highly purified adherent monocyte preparation. Monocytes from patients with active disease spontaneously secreted less tumor necrosis factor alpha and less prostaglandin E2 compared with that in patients with stable MS, while interleukin 1 beta levels were below the level of assay sensitivity. Levels of interleukin 1 beta and tumor necrosis factor alpha increased to similar levels in response to lipopolysaccharide (0.1 mg/L), indicating that altered cell viability could not account for the observed differences. In response to lipopolysaccharide, prostaglandin E2 levels increased more significantly in patients with stable than active MS, suggesting differential sensitivity to stimuli of arachidonic acid metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Monocytes in active multiple sclerosis: intact regulation of HLA-DR density in vitro despite decreased HLA-DR density in vivo.

HLA-DR expression on circulating monocytes varies as a function of disease activity in patients with multiple sclerosis (MS), a putative immunopathological demyelinating disorder. Specifically, monocytes isolated from subjects with active MS exhibit reduced HLA-DR antigen density, and immunoregulatory aberrations such as impaired T lymphocyte-mediated suppression correlate strongly with this quantitative defect. To address the mechanism underlying this phenomenon, we compared in vitro regulation of HLA-DR by interferon beta (IFN beta), interferon gamma (IFN gamma), and lipopolysaccharide (LPS) in monocytes from patients with stable and active MS and normal individuals. Interferon-gamma and LPS enhanced monocyte expression of HLA-DR equally in both MS patient groups, suggesting that underexpression of HLA-DR in active MS was not explained by impaired in vivo monocyte responsiveness. Furthermore, interferon regulation of HLA-DR in normals and stable MS subjects was indistinguishable, indicating that aberrant interferon-mediated regulation of class II major histocompatibility complex (MHC) on circulating monocytes does not appear to be a characteristic of the MS disease state.

HLA-DR Antigens↗
PubMed1991

Diagnostic criteria for multiple sclerosis research involving multiply affected families.

Existing diagnostic criteria for multiple sclerosis present significant limitations when assessing multiplex families for three reasons: (1) restricting age of onset to 10 to 50 years is likely to exclude 10% of patients known to have a later onset, (2) diagnoses based on subjective information can potentially result in a false-positive diagnosis, and (3) including progressive myelopathies occurring within families, particularly when highly symmetrical, may result in the improper inclusion of genetically determined neurological diseases such as familial spastic paraparesis. The validity of any molecular genetic approach for determining disease susceptibility critically depends on diagnostic accuracy. We present adapted diagnostic criteria that address each of these diagnostic pitfalls unique to multiplex multiple sclerosis family research.

Family↗
PubMed1991

Astrocyte expression of major histocompatibility complex gene products in multiple sclerosis brain tissue obtained by stereotactic biopsy.

Major histocompatibility complex (MHC) class I and class II antigens were characterized by immunocytochemistry in two chronic-active multiple sclerosis lesions in tissue obtained from two patients by stereotactic biopsy. We examined in particular astrocytic MHC-positive cells in relation to lesion architecture. The MHC class I (HLA-A,B,C)-positive astrocytic cells were widely dispersed, being present at the lesion edge, in the gliotic lesion center, and in normal-appearing white matter as well. Morphologically astrocytic MHC class II (HLA-DR)-positive cells were confined exclusively to the lesion edge. By staining serial sections with antisera to glial-fibrillary acidic protein and HLA-DR, we confirmed the lineage of several MHC class II-positive astrocytes. The demonstration of MHC antigen-positive astrocytes in multiple sclerosis tissue obtained by stereotactic biopsy is novel; the differential distribution of MHC class I- and class II-positive astrocytes in the multiple sclerosis lesion may provide suggestive clues about the regulation of MHC expression on these cells in vivo.

Adolescent↗
PubMed1991

Interferon-beta specifically inhibits interferon-gamma-induced class II major histocompatibility complex gene transcription in a human astrocytoma cell line.

We established cultures of human astrocytes and astrocytoma cells from surgical specimens, to study regulation of class II major histocompatibility (MHC) complex antigen expression by interferons. Using these cultures we previously showed that expression of the class II MHC determinant HLA-DR could be induced by interferon-gamma and this induction was inhibited by interferon-beta. In this report, we extend these observations by showing that the inhibitory effect of interferon-beta on interferon-gamma induction of the class II MHC gene HLA-DR alpha was exerted at the transcriptional level, as documented by nuclear run-on experiments and confirmed with blot hybridization analysis. Astrocyte expression of intercellular adhesion molecule-1 (ICAM-1) was induced efficiently by interferon-gamma, but not by interferon-beta, and induction of ICAM-1 expression by interferon-gamma could not be impaired by interferon-beta, suggesting that the suppressive effect on induction of HLA-DR was relatively gene-specific. Furthermore, interferon-beta did not antagonize interferon-gamma induction of HLA-DR expression in human monocytes, suggesting that the inhibition observed in astrocytes was relatively tissue-specific.

Astrocytes↗
PubMed1990

Stereotactic biopsy of an active multiple sclerosis lesion. Immunocytochemical analysis and neuropathologic correlation with magnetic resonance imaging.

Stereotactic biopsy of an active multiple sclerosis lesion in a 23-year-old patient with unilateral symptoms and an isolated high-signal-intensity magnetic resonance abnormality yielded 10 serial tissue cores (1.0 x 0.5 cm) spanning 40 mm within and around the lesion. We performed semiquantitative analysis of lymphocyte phenotype, using antisera to CD3, CD4, CD8, and CD22 molecules, in 11 separate perivascular cuffs in three tissue sections from the lesion edge. Total cells in the cuffs varied from 10 to 100; ratios of CD4+/CD8+ cells in individual cuffs varied from 1.3 to 4.7. Although intense parenchymal infiltrates bordered the least cellular cuffs, parenchymal and perivascular cell phenotypes were indistinguishable, arguing against selective trafficking of lymphocytes into tissue. Individual microfoci of cells displaying CD45RA, CD25, and TQ1 antigens were present. The remarkable phenotypic heterogeneity of T lymphocytes in the multiple sclerosis lesion border is consistent with exposure in situ to a diversity of differentiating stimuli. Histologic demyelination correlated very closely with the signal-intensity abnormality observed on magnetic resonance imaging. These studies provide unusual insight into the histologic and immunocytochemical morphologic appearance of the active multiple sclerosis plaque.

Adult↗
PubMed1990

Characterization of adult human astrocytes derived from explant culture.

Four different human astrocytic cell lines established from either epilepsy surgical specimens or cerebral white matter obtained during thalamotomy for tremor in a patient with multiple sclerosis were characterized using morphologic analysis, ultrastructural attributes, growth characteristics, and immunocytochemical analysis. Immunocytochemical characterization of cultures indicated a mean of 84% of cells contained cytoplasmic glial fibrillary acidic protein (GFAP): to confirm that GFAP(+) cells also proliferated, bromo-deoxyuridine (BrdU) uptake was measured in cell line. Our method of simplified explant culture allows establishment of astrocytic cell lines from a variety of pathologic substrates using limited amounts of human material.

Adult↗
PubMed1990

Human astrocytes proliferate in response to tumor necrosis factor alpha.

Two different human astrocytic cell lines derived from adult epilepsy surgical specimens were exposed in vitro to concentrations of 1-100 ng/ml recombinant tumor necrosis factor alpha (TNF alpha). Results indicated dose-dependent stimulation of DNA synthesis and proliferation. Both of these effects were abrogated by treatment with monoclonal antibody specific for TNF alpha but not by irrelevant murine IgG. Immunocytochemical characterization of TNF alpha-treated and control cultures indicated that greater than 98% of proliferating cells contained cytoplasmic glial fibrillary acidic protein (GFAP), and were therefore astrocytic in nature. These studies demonstrate that growth of adult human non-neoplastic astrocytes is stimulated by TNF alpha, an inflammatory cytokine produced primarily by macrophages but also by astrocytes.

Astrocytes↗
PubMed1990

Astrocyte cultures derived from human brain tissue express angiotensinogen mRNA.

We have identified human cultured cell lines that are useful for studying angiotensinogen gene expression and its regulation in the central nervous system. A model cell system of human central nervous system origin expressing angiotensinogen has not previously been available. Expression of angiotensinogen has not previously been available, Expression noninduced human astrocytes, since astrocytic cell lines derived from human glioblastomas or nonneoplastic human brain tissue invariably produced angiotensinogen mRNA. In situ hybridization histochemistry revealed that angiotensinogen mRNA production was not limited to a subpopulation of astrocytes because greater than 99% of cells in these cultures contained angiotensinogen mRNA. These cell lines will be useful in studies of the molecular mechanisms controlling angiotensin synthesis and the role of biologically active angiotensin in the human brain by allowing us to examine regulation of expression of the renin-angiotensin system in human astrocyte cultures.

Angiotensinogen↗