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Biomedical subjects

R L Knobler

Publications and source records attributed to R L Knobler.

At least 73 records · Page 4Linked to original sources
PubMed1986

Interleukin 2 mediates the inhibition of oligodendrocyte progenitor cell proliferation in vitro.

In the immune system, T-lymphocyte proliferation depends on interleukin 2 [IL-2 (T-cell growth factor)] interaction with specific receptors. In this study we show that IL-2 can specifically inhibit the proliferation of neonatal rat oligodendrocyte progenitor cells cultured in a serumless, chemically defined medium (oligodendrocyte-defined medium; ODM). IL-2 inhibited both [3H]thymidine incorporation and increase in cell number. Specificity was shown by precipitating IL-2 activity with anti-IL-2 antiserum. Furthermore, growth inhibition depended on the expression of Tac (an anti-IL-2 receptor monoclonal antibody)-positive receptors (IL-2 receptor). When cells were cultured in the presence of IL-2, both Tac-positive staining and growth inhibition were no longer expressed. The addition of interleukin 1 had no effect on [3H]thymidine incorporation or changes in cell number. However, when IL-1 was subsequently added together with IL-2, Tac expression and IL-2-mediated inhibition of cell proliferation was induced. This inhibitory effect was not due to a sensitive subpopulation because greater than 90% of the culture was Tac positive. Taken together, these data show that IL-2 can specifically inhibit oligodendrocyte proliferation and acts via Tac-positive receptors.

Animals↗
PubMed1986

Relapsing experimental allergic encephalomyelitis in radiation bone marrow chimeras between high and low susceptible strains of mice.

The relapsing form of experimental allergic encephalomyelitis (EAE) has been shown to be a useful model of the human disease, multiple sclerosis. This autoimmune disease is organ specific and appears to be primarily a cell-mediated disorder similar to the acute form of EAE. In order to understand better the regulatory mechanisms responsible for development of disease, radiation bone marrow chimeras were prepared between the highly susceptible SJL/J mouse and the resistant B10.S mouse. A high incidence of disease was seen in SJL----SJL and B10.S----SJL chimeras. A low incidence was seen in B10.S----B10.S and SJL----B10.S chimeras. The results were similar in mice immunized with CNS antigen of either BALB/c or B10.S origin. These results demonstrate that the immune system from the resistant B10.S mouse is capable of mediating relapsing EAE when present in a susceptible SJL host, while the SJL immune system was restricted in its ability to induce disease when present in a resistant B10.S host. This would indicate that restriction to the development of EAE may reside outside of the immune system, perhaps involving antigen recognition or presentation in the CNS itself.

Animals↗
PubMed1985

Encephalitogenic T cell clones specific for myelin basic protein. An unusual bias in antigen recognition.

Class II-restricted T cell clones specific for myelin basic protein (MBP) have been generated from PL/J and (PL/J X SJL/J)F1 [((PLSJ)F1] mice following sensitization to rat MBP. Of 17 T cell clones generated from (PLSJ)F1 mice, 5 are I-Au(A alpha uA beta u) restricted, one is restricted to I-As(A alpha sA beta s), 10 are restricted to hybrid I-A(u X s)F1 (A alpha sA beta u) determinants, and one clone is restricted to hybrid I-E(u X s) (E alpha uE beta s) molecules. Thus, of 16 I-A-restricted T cell clones generated from (PLSJ)F1 mice, only one is I-As-restricted, reflecting a lack of priming to MBP in association with I-As. T cell clones restricted to I-Au and to I-E (E alpha u E beta s) molecules recognize mouse (self) MBP. Furthermore, only the five T cell clones restricted to I-Au molecules recognize a determinant in common with mouse (self) MBP within the encephalitogenic N-terminal peptide. Three such I-Au restricted T cell clones, derived independently, cause paralysis in 100% of (PL/J X SJL/J)F1 mice tested. Acute, chronic unremitting, and chronic relapsing paralysis are all induced following injection of these clones. Administration of greater numbers of cloned T cells causes acute and fatal experimental allergic encephalomyelitis, while administration of lower numbers of cloned T cells is associated with chronic unremitting and relapsing paralysis. Paralysis induced with T cell clones shares many clinical, immunologic, and histologic aspects with human demyelinating diseases such as multiple sclerosis. Histopathology reveals perivascular lymphocytic infiltration, demyelination, and remyelination. These studies demonstrate the utility of T cell clones for analyzing the association between class II major histocompatibility complex molecules and disease susceptibility.

Animals↗
PubMed1985

Immunological complications in multiple sclerosis patients receiving interferon.

In a prospective, placebo-controlled study designed to test the efficacy of human alpha interferon (IFN) in the treatment of multiple sclerosis, we monitored several immunological functions. Interferon was shown to have many effects on the immune system, including activation of natural killer cells in vivo and elevation of serum immunoglobulin and cerebrospinal fluid IgG ratios. Furthermore, all patients who received IFN developed antibody titers to a protein contaminant (molecular weight, 27 kilodaltons) in the IFN preparation. This antibody was associated with an elevation in serum concentrations of C1q- and Raji-binding immune complexes in 6 of 12 patients. Some of these 12 patients developed symptoms suggestive of immune complex disease. IFN had pronounced effects on the immune system of these patients.

Antibodies↗
PubMed1985

Host genetic regulation of acute MHV-4 viral encephalomyelitis and acute experimental autoimmune encephalomyelitis in (BALB/cKe x SJL/J) recombinant-inbred mice.

In the present report we provide the strain distribution patterns of susceptibility to acute mouse hepatitis virus type-4 (MHV-4) encephalomyelitis, acute experimental allergic encephalomyelitis (EAE) and vasoactive amine sensitivity (VAAS) for 9 (CXJ) recombinant-inbred strains between BALB/cKe (C) and SJL/J(J) mice. We confirm that susceptibility to MHV-4 is not linked to the H-2 complex, and that all strains susceptible to acute EAE have both a responder H-2 haplotype (H-2s or H-2d) and induced (B. pertussis) VAAS. In addition, we provide evidence that susceptibility to acute EAE induction is controlled by an additional presently unmapped locus and that an EAE-like histopathological disease does not usually follow MHV-4 infection intracerebrally in animals susceptible to MHV-4, acute EAE and induced VAAS.

Animals↗
PubMed1985

Epitope-specific antibody response to murine hepatitis virus-4 (strain JHM).

Monoclonal hybridoma antibodies to the structural proteins of murine hepatitis virus-4, strain JHM (MHV-4) were used in a competition binding enzyme immunoassay to analyze at the epitope level the antibody response of mice after infection with MHV-4. Colonized mice often had pre-existing MHV antibodies directed against epitopes on the E2 glycoprotein, the E1 glycoprotein, and the nucleocapsid protein. These mice generated a secondary antibody response after virus inoculation, reaching peak levels 7 days after infection. In contrast, Nude/+ mice raised in a pathogen-free colony had no detectable circulating MHV antibodies and generated a primary antibody response which gradually increased to peak levels 14 to 28 days after infection. Kinetics of antibody responses against specific epitopes usually correlated well with measured total virus-specific antibody responses, but variation was observed. Mice injected with three antigenically distinct strains of MHV made antibody responses to conserved epitopes but not to an antigenic determinant absent in these strains. Measurement of epitope-specific responses in a polyclonal population of viral specific antibodies is feasible and a valuable adjunct in understanding viral immunity.

Animals↗
PubMed1984

Western and dot immunoblotting analysis of viral antigens and antibodies: application to murine hepatitis virus.

Viral proteins were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and transferred quantitatively to nitrocellulose by electroblotting in SDS-containing buffer. Monoclonal antibodies directed against previously defined epitopes on the viral proteins were used as probes to detect viral protein synthesis and processing, as well as expression in animal tissues. Circulating polyclonal antibodies were also probed and characterized for their polypeptide specificities. Under appropriate conditions, this Western immunoblotting technique was quantitative. Finally, a highly sensitive dot immunoblotting assay was used to analyze the sensitivity to denaturation of various epitopes on the viral proteins. This assay detected picogram quantities of viral antigens and antibodies.

Antigens, Viral↗
PubMed1984

Topographical mapping of epitopes on the glycoproteins of murine hepatitis virus-4 (strain JHM): correlation with biological activities.

Monoclonal hybridoma antibodies (MAb) of defined polypeptide specificity and biological activity were used in a competition binding assay to identify antibody binding sites (epitopes) on the glycoproteins of murine hepatitis virus-4 strain JHM (MHV-4). Individual MAb were labeled with horseradish peroxidase (HRP) and used as probes in a competition enzyme immunoassay (EIA). Four topographically distinct antigenic sites were detected on the E2 glycoprotein of MHV-4. Antibodies reacting with these four determinants provisionally designated A(E2), B(E2), C(E2), and D(E2) had corresponding biological activities (M. J. Buchmeier, H. A. Lewicki, P. J. Talbot, and R. L. Knobler (1984) Virology 132, 261-270). Antibodies to sites A(E2) and B(E2) mediated virus neutralization in vitro and passively protected mice against lethal virus challenge in vivo. Antibody to site C(E2) neutralized virus efficiently in vitro but did not alter disease in vivo, while antibody to site D(E2) neither neutralized nor protected. Two major nonoverlapping antigenic sites were defined on the E1 glycoprotein. Overlapping epitopes A(E1) and B(E1) constituted one site and epitope C(E1) the other.

Animals↗
PubMed1984

Murine hepatitis virus-4 (strain JHM)-induced neurologic disease is modulated in vivo by monoclonal antibody.

Monoclonal hybridoma antibodies directed against the polypeptides of murine hepatitis virus-4 (JHM strain) were tested for their ability to alter the course of a normally lethal intracerebral virus challenge. Three monoclonal antibodies directed against two distinct epitopes on the E2 glycoprotein of MHV-4 protected mice against lethal virus challenge and converted the infection from fatal encephalomyelitis to demyelination. A single neutralizing antibody directed against a third epitope on E2 as well as seven nonneutralizing antibodies to E2, E1, and N polypeptides did not protect against challenge. In mice which received protective antibody, MHV-4 infection was not blocked, however, virus grew to lower titers in liver and brain, and virus replication in the CNS was more restricted than in unprotected mice. Decreased involvement of neurons in the brains of protected mice was observed, and no evidence of neuronal infection in the spinal cords was found. In contrast, oligodendrocytes were infected in the presence of protective antibody, and evidence of demylination associated with mononuclear cell infiltration was found. These studies demonstrate that antibody to a single epitope on a viral glycoprotein can substantially alter the course and phenotype of disease.

Animals↗
PubMed1984

Disease activity markers in multiple sclerosis. Another look at suppressor cells defined by monoclonal antibodies OKT4, OKT5, and OKT8.

Here we report our experience in profiling peripheral blood T-cell subsets with the monoclonal antibodies OKT4, OKT5 , and OKT8. Lymphocyte surface phenotype was measured by automated cytofluorometry. In a population survey, we were unable to detect differences between patients with multiple sclerosis (MS) and control subjects when we compared ratios of lymphocytes of helper cell phenotype (OKT4) to those with suppressor cell phenotype ( OKT5 and OKT8). No differences could be established between patients with stable disease, chronic progressive disease, or those with active disease. In a study of 10 patients followed through an exacerbation, we were also unable to define perturbations in these lymphocyte ratios that correlated with disease activity. Detailed analysis of the fluorescence histogram, which examines the entire spectrum of cell surface fluorescence intensity in a population of lymphocytes, was also not useful in predicting disease activity in these patients. The discrepancies between these data and other reports in the literature are discussed. We propose that these reagents are inadequate indices of disease activity, and that until other monoclonal reagents are developed and studied, the suppressor cell compartment is best assessed by assays of function.

Antibodies, Monoclonal↗
PubMed1984

Host genetic control of mouse hepatitis virus type 4 (JHM strain) replication. I. Restriction of virus amplification and spread in macrophages from resistant mice.

Peritoneal macrophages were used to analyse host genetic control of mouse hepatitis virus type 4 (MHV-4) infection. Both infectious centre and immunofluorescence assays indicated that only a subset of macrophages from either susceptible (BALB, C3H or C57BL/6J) or resistant (SJL/J) mice were initially infected with MHV-4 during the first cycle of infection. However, compared to macrophages from susceptible mice, three- to sixfold fewer SJL/J macrophages were infected, and there was no amplification of virus replication by involvement of adjacent cells during the second cycle of infection. Treatment of macrophages from susceptible mice with interferon beta could not duplicate the aborted second cycle of infection that occurred in macrophages from resistant mice.

Animals↗
PubMed1984

Systemic alpha-interferon therapy of multiple sclerosis.

A randomized, double-blind, placebo-controlled crossover study tested the efficacy of natural alpha interferon in altering exacerbating-remitting MS. Twenty-four patients with frequent exacerbations were treated for 6-month periods, beginning with either 5 X 10(6) IU of interferon daily or placebo. A 6-month washout period followed each treatment. Exacerbation rates were reduced during interferon and placebo phases compared with pre-study rates; a greater reduction occurred on interferon, particularly following placebo, possibly reflecting a learning phenomenon. Fifteen patients with a strictly exacerbating-remitting course had fewer and milder exacerbations on interferon compared with those on placebo, whereas 9 patients with a progressive component continued to have active disease. These results suggest that interferon might reduce exacerbations in certain patients and indicate guidelines for future trials of interferon in MS.

Adult↗
PubMed1984

A neurologic rating scale (NRS) for use in multiple sclerosis.

A neurologic rating scale (NRS) has been developed for clinical assessment of MS patients. The scale has been tested on 250 MS patients. Assignment of the NRS score is based on assessment of each component of the neurologic examination and accurately reflects overall neurologic function. Clinical exacerbations are evident as significant deviations from baseline scores. There was close interexaminer correlation, with the range of variability no greater than 2.6%. The NRS is a simple, reliable, and sensitive scale that can be used with other objective measurements of neurologic function, such as neurophysiologic studies, in the clinical assessment of MS patients.

Humans↗
PubMed1984

Host genetic control of mouse hepatitis virus type-4 (JHM strain) replication. II. The gene locus for susceptibility is linked to the Svp-2 locus on mouse chromosome 7.

Peritoneal macrophages were used to analyze host genetic control of MHV-4 infection in the 14 recombinant-inbred strains between susceptible SWR/J and resistant SJL/J progenitor strains. 4 strains were resistant to MHV-4 infection, while the remaining 10 strains were productively infected. Based upon the strain distribution pattern of susceptibility the gene locus for MHV-4 susceptibility is linked to the Svp-2 locus on the proximal end of mouse chromosome 7. This strain distribution pattern of susceptibility, and hence linkage, was determined to be identical for another MHV strain, MHV-A59. We have suggested that this locus-controlling susceptibility to MHV-4 and MHV-A59 be designated Hv-2.

Animals↗
PubMed1983

Virologic models of chronic relapsing demyelinating disease.

The present report, compares two murine models of virus induced chronic relapsing demyelination. MHV-induced demyelination in the BALB/c mouse results from the direct virus mediated cytolysis of oligodendrocytes. Extensive remyelination by oligodendrocytes is noted. Recurrent demyelination occurs in small areas. Infectious virus persists and viral antigens are localized within oligodendrocytes and their processes. TMEV-induced demyelination in SJL/J mice is associated with perivascular inflammatory infiltrates and is diminished by immunosuppressive measures. Remyelination by oligodendrocytes is delayed and incomplete. Chronic demyelination is widespread and associated with perivascular inflammatory infiltrates. The virus persists and viral antigen is localized within oligodendrocytes. The findings indicate virus persistence in oligodendrocytes in both models. Demyelination follows the disintegration of infected oligodendrocytes. Virus replication in oligodendrocytes is responsible for cell lysis in the MHV model whereas immune mediated injury of infected oligodendrocytes is considered to play a role in the pathogenesis of demyelination in the TMEV model.

Animals↗
PubMed1983

Mouse hepatitis virus type 4 infection of primary glial cultures from genetically susceptible and resistant mice.

Mouse hepatitis virus type 4 infection of primary glial cultures, which consisted principally of astrocytes (marked by glial fibrillary acidic protein) from encephalitis-susceptible BALB/c or F1 (BALB/c x SJL/J) hybrid mice and resistant SJL/J mice, was studied. Primary neuron cultures from BALB/c and F1 hybrid mice were previously shown to be permissive and were destroyed within 5 days by infection with mouse hepatitis virus type 4, whereas neurons from SJL/J mice were fully resistant. In contrast, in the present study a chronic infection was established and maintained for up to 18 days in glial cultures from all three mouse strains. Infected SJL/J mouse glial cultures produced 10- to 50-fold less infectious virus and showed less cytopathic effect than did cultures from either infected BALB/c or F1 hybrid mice. Cytopathic effect was evident initially in cells from all three strains, and continued virus production occurred in the presence of limited additional cytopathic effect. These results were not due to the production of detectable levels of interferon. This study showed that SJL/J mouse primary glial cultures were permissive for mouse hepatitis virus type 4 infection whereas SJL/J primary neuron cultures were not, and that there was an early lytic phase of infection followed by chronic infection in all three strains.

Animals↗