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L R Pease

Publications and source records attributed to L R Pease.

At least 37 records · Page 2Linked to original sources
PubMed1998

Targeting of IgMkappa antibodies to oligodendrocytes promotes CNS remyelination.

We previously identified the remyelinating activity of a natural IgMkappa oligodendrocyte-reactive autoantibody (SCH94.03), using a virus-induced murine model of multiple sclerosis. We now describe a second mouse IgMkappa monoclonal antibody (mAb) (SCH79.08) raised against normal mouse spinal cord homogenate, which reacts with myelin basic protein and also promotes remyelination. Because these two mAbs recognize different oligodendrocyte antigens, several previously identified oligodendrocyte-reactive IgMkappa mAbs (O1, O4, A2B5, and HNK-1), each with distinct antigen specificities, were evaluated and found to promote remyelination. In contrast, IgMkappa mAbs that did not bind to oligodendrocytes showed no remyelination. One of these, CH12 IgMkappa mAb, which shares variable region cDNA sequences with SCH94.03 except for amino acid differences in the complementarity-determining region 3 in both heavy and light chains, did not bind to oligodendrocytes and did not promote remyelination. The fact that multiple oligodendrocyte-reactive antibodies with distinct antigen reactivities induce remyelination argues against direct activation by a unique cell surface receptor. These findings are most consistent with the hypothesis that the binding of mAbs to oligodendrocytes in the lesions induces myelin repair via indirect immune effector mechanisms initiated by the mu-chain. Importantly, these studies indicate that oligodendrocyte-reactive natural autoantibodies may provide a powerful and novel therapeutic means to induce remyelination in multiple sclerosis patients.

Animals↗
PubMed1998

Perforin-dependent neurologic injury in a viral model of multiple sclerosis.

In this study we demonstrate perforin-mediated cytotoxic effector function is necessary for viral clearance and may directly contribute to the development of neurologic deficits after demyelination in the Theiler's murine encephalomyelitis virus (TMEV) model of multiple sclerosis. We previously demonstrated major histocompatability complex (MHC) class I-deficient (beta2m-deficient) mice with an otherwise resistant genotype develop severe demyelination with minimal neurologic disease when chronically infected with TMEV. These studies implicate CD8(+) T cells as the pathogenic cell in the induction of neurologic disease after demyelination. To determine which effector mechanisms of CD8(+) T cells, granule exocytosis or Fas ligand expression, play a role in the development of demyelination and clinical disease, we infected perforin-deficient, lpr (Fas mutation), and gld (Fas ligand mutation) mice with TMEV. Perforin-deficient mice showed viral persistence in the CNS, chronic brain pathology, and demyelination in the spinal cord white matter. Perforin-deficient mice demonstrated severely impaired MHC class I-restricted cytotoxicity against viral epitopes, but normal MHC class II-restricted delayed-type hypersensitivity responses to virus antigen. Despite demyelination, virus-infected perforin-deficient mice showed only minimal neurologic deficits as indicated by clinical disease score, activity monitoring, and footprint analysis. Perforin- and MHC class II-deficient mice (with functional CD8(+) T cells and perforin molecules and an H-2(b) haplotype) had comparable demyelination and genotype, however, only the latter showed severe clinical disease. Gld and lpr mice demonstrated normal TMEV-specific cytotoxicity and maintained resistance to TMEV-induced demyelinating disease. These studies implicate perforin release by CD8(+) T cells as a potential mechanism by which neurologic deficits are induced after demyelination.

Animals↗
PubMed1998

Theiler's virus infection of genetically susceptible mice induces central nervous system-infiltrating CTLs with no apparent viral or major myelin antigenic specificity.

Intracranial infection of susceptible mice with Theiler's virus results in persistent infection and spinal cord demyelination similar to human multiple sclerosis. While central nervous system infiltrating lymphocytes (CNS-ILs) in these mice display no virus-specific CTL activity, the cells were found to be activated killers using a specificity-independent assay. We previously demonstrated that the depletion of T cells in persistently infected mice significantly decreases demyelinating disease. Consequently, we have investigated the killing pathways employed by CNS-ILs that are isolated from persistently infected animals, the relative contribution of CD4 and CD8 cells in the generation of these CTLs, and the reactivity of this cell population to two putative autoantigens in the CNS. In vitro or in vivo manipulation of T cell populations using Abs or genetic knockout strategies demonstrate that the cytotoxic activity is primarily mediated by CD8+ T cells, and that perforin is an important molecule in the effector pathway. Since effector functions in infected mice were not inhibited by the depletion of CD4 cells with mAb but was blocked genetically in CD4 knockout mice, CD4+ T cells appear to play a helper role in the generation of CD8+ CTLs. We found no evidence of autoimmune-mediated demyelination, as the CD8+ CTLs were not reactive to two major myelin autoantigens, myelin basic protein and proteolipid protein. Our finding that CNS-ILs that are isolated from mice susceptible to persistent virus infection are neither specific for virus or myelin autoantigens is consistent with the possibility that CD8+ CTLs mediate CNS damage as a result of nonspecific activation by virus.

Animals↗
PubMed1998

Structural basis of plasticity in T cell receptor recognition of a self peptide-MHC antigen.

The T cell receptor (TCR) inherently has dual specificity. T cells must recognize self-antigens in the thymus during maturation and then discriminate between foreign pathogens in the periphery. A molecular basis for this cross-reactivity is elucidated by the crystal structure of the alloreactive 2C TCR bound to self peptide-major histocompatibility complex (pMHC) antigen H-2Kb-dEV8 refined against anisotropic 3.0 angstrom resolution x-ray data. The interface between peptide and TCR exhibits extremely poor shape complementarity, and the TCR beta chain complementarity-determining region 3 (CDR3) has minimal interaction with the dEV8 peptide. Large conformational changes in three of the TCR CDR loops are induced upon binding, providing a mechanism of structural plasticity to accommodate a variety of different peptide antigens. Extensive TCR interaction with the pMHC alpha helices suggests a generalized orientation that is mediated by the Valpha domain of the TCR and rationalizes how TCRs can effectively "scan" different peptides bound within a large, low-affinity MHC structural framework for those that provide the slight additional kinetic stabilization required for signaling.

Animals↗
PubMed1998

Degenerate recognition of alloantigenic peptides on a positive-selecting class I molecule.

The well-defined 2C T cell was used to investigate alloreactive degeneracy. A panel of class I molecules that are known ligands for the 2C TCR were sensitized with three known peptide ligands, p2Ca (LSPFPFDL), dEV-8 (EQYKFYSV), and SIYR-8 (SIYRYYGL). The peptide p2Ca was originally identified as the allopeptide seen in the Ld class I molecule by 2C T cells, 2C recognizes the dEV-8 peptide as the ligand in the Kbm3 class I molecule, and SIYR-8 was recently identified as a peptide ligand for 2C in the context of the Kb class I molecule. Strong recognition of all three Ag-presenting molecules occurred in the context of their respective allopeptides, but 2C recognized all three peptides to a measurable extent in the context of Kb. Molecular modeling of these Kb/peptide complexes revealed a high degree of similarity between dEV-8 and SIYR-8, but very little conformational similarity of either of these peptides with p2Ca. Furthermore, the structural changes in the mutant Kbm3 binding site resulted in generalized changes in the conformation of each of five bound peptides compared with those of the same peptides bound to Kb. The finding that degenerate recognition occurs on Kb, the restriction element responsible for selecting 2C T cells, suggests a unique relationship between a TCR and the Ag-presenting molecule that mediates its positive selection.

Animals↗
PubMed1998

Chromosome 14 contains determinants that regulate susceptibility to Theiler's virus-induced demyelination in the mouse.

Theiler's murine encephalomyelitis virus causes a chronic demyelinating disease in susceptible strains of mice that is similar to human multiple sclerosis. Several nonmajor histocompatibility complex-linked genes have been implicated as determinants of susceptibility or resistance to either demyelination or virus persistence. In this study, we used linkage analysis of major histocompatibility complex identical H-2d (DBA/2J x B10.D2) F2 intercross mice to identify loci associated with susceptibility to virus-induced demyelinating disease. In a 20-cM region on chromosome 14, we identified four markers, D14Mit54, D14Mit60, D14Mit61, and D14Mit90 that are significantly associated with demyelination. Because two peaks were identified, one near D14Mit54 and one near D14Mit90, it is possible that two loci in this region are involved in controlling demyelination.

Animals↗
PubMed1998

Molecular characterization of a nondemyelinating variant of Daniel's strain of Theiler's virus isolated from a persistently infected glioma cell line.

Wild-type Daniel's strain of Theiler's virus (wt-DA) induces a chronic demyelination in susceptible mice which is similar to multiple sclerosis. A variant of wt-DA (designated DA-P12) generated during the 12th passage of persistent infection of a G26-20 glioma cell line failed to persist and induce demyelination in SJL/J mice. To identify the determinants responsible for this change in phenotype, we sequenced the capsid coding sequence (nucleotides [nt] 2991 to 3994) and found three mutations in VP1: residues 99 (Gly to Ser), 100 (Gly to Asp), and 103 (Asn to Lys). To study the role of these mutations in neurovirulence and demyelination, we prepared a recombinant virus, DAP-1C-2A/DA, with replacement of wt-DA nt 2991 to 3994 with the corresponding region of DA-P12, and viruses with individual point mutations at VP1 residues 99(Ser), 100(Asp), and 103(Lys). DAP-1C-2A/DA and viruses with a mutation at VP1 residue 99 or 100 (but not 103) completely attenuated the ability of wt-DA to induce demyelination. Failure to induce demyelination was not due to a general failure in growth, since DA-P12 and other mutant viruses lysed L-2 cells in vitro as effectively as wt-DA. The change in disease phenotype was independent of the specific B- or T-cell immune recognition because a decrease in the neurovirulence of mutant viruses was observed in neonatal mice and immune-deficient RAG1 -/- mice. This difference in neurovirulence is not the complete explanation for the failure of DA-P12 to demyelinate, since virus with a mutation at residue 103(Lys) had decreased neurovirulence but did induce demyelination. Therefore, point mutation at VP1 residue 99 or 100 altered the ability of wt-DA to demyelinate, perhaps related to a disruption in interaction between virus and receptor on certain neural cells.

Animals↗
PubMed1997

Alphabeta T cell receptor interactions with syngeneic and allogeneic ligands: affinity measurements and crystallization.

Cellular immunity is mediated by the interaction of an alphabeta T cell receptor (TCR) with a peptide presented within the context of a major histocompatibility complex (MHC) molecule. Alloreactive T cells have alphabeta TCRs that can recognize both self- and foreign peptide-MHC (pMHC) complexes, implying that the TCR has significant complementarity with different pMHC. To characterize the molecular basis for alloreactive TCR recognition of pMHC, we have produced a soluble, recombinant form of an alloreactive alphabeta T cell receptor in Drosophila melanogaster cells. This recombinant TCR, 2C, is expressed as a correctly paired alphabeta heterodimer, with the chains covalently connected via a disulfide bond in the C-terminal region. The native conformation of the 2C TCR was probed by surface plasmon resonance (SPR) analysis by using conformation-specific monoclonal antibodies, as well as syngeneic and allogeneic pMHC ligands. The 2C interaction with H-2Kb-dEV8, H-2Kbm3-dEV8, H-2Kb-SIYR, and H-2Ld-p2Ca spans a range of affinities from Kd = 10(-4) to 10(-6)M for the syngeneic (H-2Kb) and allogeneic (H-2Kbm3, H-2Ld) ligands. In general, the syngeneic ligands bind with weaker affinities than the allogeneic ligands, consistent with current threshold models of thymic selection and T cell activation. Crystallization of the 2C TCR required proteolytic trimming of the C-terminal residues of the alpha and beta chains. X-ray quality crystals of complexes of 2C with H-2Kb-dEV8, H-2Kbm3-dEV8 and H-2Kb-SIYR have been grown.

Amino Acid Sequence↗
PubMed1997

A complex major histocompatibility complex D locus variant generated by an unusual recombination mechanism in mice.

A spontaneous variant of the mouse class I major histocompatibility complex D(b) gene, designated D(bm28), is characterized. This mutation consists of a cluster of nucleotide substitutions in exon 3 that resembles the product of a classical gene conversion event in that the substituted nucleotides appear to be templated. However, D(bm28) is distinctive, because no single donor gene containing the nucleotide sequence of the mutation exists in the genome of the parent strain. The mutation is consistent with the expected result of an interaction of two donor genes at the target locus during a single recombination event. While no known genetic mechanism gives rise to this class of mutation, we have established that 10 percent of spontaneous class I mutations in the mouse major histocompatibility complex have this complex phenotype. This process occurs at the D locus and the K locus. The significance of this kind of genetic interaction may extend beyond the major histocompatibility complex and have importance in shaping other multigene families.

Animals↗
PubMed1997

Differential generation of class I H-2D- versus H-2K-restricted cytotoxicity against a demyelinating virus following central nervous system infection.

Despite the fact that both H-2K and D molecules are up-regulated in the central nervous system (CNS) following Theiler's murine encephalomyelitis virus (TMEV) infection, resistance in this virus model of multiple sclerosis maps exclusively to D. To address this paradox, we examined the ability of the K and D molecules to present viral antigens to cytotoxic T lymphocytes (CTL). Whereas no virus-specific CTL were detected in the CNS of susceptible B10.Q and B10.S mice 7 days post-infection, D-restricted CTL were identified readily in the CNS of resistant B10 animals. There was no evidence of K-restricted CTL in the CNS of B10 mice at day 7 post-infection. The presence of both K- and D-restricted virus-specific CTL in the spleen of immunized B10 mice demonstrates that the exclusive use of D molecules by CTL in the CNS of mice 7 days post-infection is not due to the inability of the K molecules to present viral peptides to lymphocytes. We conclude that the prominent role of the D locus in determining resistance or susceptibility to TMEV-induced demyelination is determined by factors governing the regulation of the immune response, and not by the presence or absence of CTL precursors capable of recognizing viral peptides presented by the K and D antigen-presenting molecules, or by differences in the ability of the K and D molecules to present viral peptides.

Animals↗
PubMed1997

Antiviral immune responses modulate the nature of central nervous system (CNS) disease in a murine model of multiple sclerosis.

The spectrum of disease is influenced by factors related to both the pathogen and the host, as well as the end points used in defining disease. In this article, the issue of disease resistance versus susceptibility will be examined in the framework that genetic manipulation of either the pathogen or the host immune response alters the balance from disease protection towards pathogenesis. The response of the host may trigger both a protective and a pathogenic immune response. The failure to mount a protective immune response predisposes the pathogen to persistence, which then becomes the target for immunopathology. This review will examine the factors involved both in virus-mediated pathogenesis and in disease protection in the Theiler's model of human multiple sclerosis. By manipulating the character of the virus pathogen and the specificity of the immune response, the entire spectrum of human demyelinating disease is reproduced.

Animals↗
PubMed1997

The immune system preferentially clears Theiler's virus from the gray matter of the central nervous system.

Infection of susceptible strains of mice with Daniel's (DA) strains of Theiler's murine encephalomyelitis virus (DAV) results in virus persistence in the central nervous system (CNS) white matter and chronic demyelination similar to that observed in multiple sclerosis. We investigated whether persistence is due to the immune system more efficiently clearing DAV from gray than from white matter of the CNS. Severe combined immunodeficient (SCID) and immunocompetent C.B-17 mice were infected with DAV to determine the kinetics, temporal distribution, and tropism of the virus in CNS. In early disease (6 h to 7 days postinfection), DAV replicated with similar kinetics in the brains and spinal cords of SCID and immunocompetent mice and in gray and white matter. DAV RNA was localized within 48 h in CNS cells of all phenotypes, including neurons, oligodendrocytes, astrocytes, and macrophages/microglia. In late disease (13 to 17 days postinfection), SCID mice became moribund and permitted higher DAV replication in both gray and white matter. In contrast, immunocompetent mice cleared virus from the gray matter but showed replication in the white matter of their brains and spinal cords. Reconstitution of SCID mice with nonimmune splenocytes or anti-DAV antibodies after establishment of infection demonstrated that both cellular and humoral immune responses decreased virus from the gray matter; however, the cellular responses were more effective. SCID mice reconstituted with splenocytes depleted of CD4+ or CD8+ T lymphocytes cleared virus from the gray matter but allowed replication in the white matter. These studies demonstrate that both neurons and glia are infected early following DAV infection but that virus persistence in the white matter is due to preferential clearance of virus from the gray matter by the immune system.

Animals↗
PubMed1997

Interferon alpha/beta mediates early virus-induced expression of H-2D and H-2K in the central nervous system.

Cells of the central nervous system (CNS) normally do not express detectable levels of major histocompatibility complex (MHC) Class I antigens. However, MHC Class I expression can be induced after virus infection. We tested the hypothesis that virus-induced Class I expression is mediated by lymphocytes or cytokines using lymphocyte- and cytokine-deficient mice. We used Theiler's murine encephalomyelitis virus (TMEV), which induces CNS demyelination that maps genetically to the D region of MHC Class I and is associated with high levels of Class I products. TMEV infection of severe combined immunodeficiency (SCID) and recombination activation gene-1-deficient mice, which lack B and T lymphocytes, resulted in equivalent H-2D and H-2K expression in brain and spinal cord, according to analysis of the area and intensity of immunoperoxidase staining. Class I antigens were demonstrated as early as 6 hours after infection, and they were more widely distributed than viral RNA, indicating that expression was induced indirectly via a soluble factor. To determine whether cytokines induced the expression, we infected mice lacking receptors for interferon-alpha/beta (IFN-alpha/beta R (-/-)), interferon-gamma (IFN-gamma R(-/-)), and tumor necrosis factor-alpha (TNFRp55(-/-)). TMEV-infected IFN-gamma R(-/-) and TN-FRp55(-/-) mice expressed Class I antigens in the CNS, whereas IFN-alpha/beta R(-/-) mice did not, establishing that IFN-alpha/beta mediated the expression. In contrast to the equivalent expression in SCID mice, we observed greater area and higher intensity of H-2D versus H-2K antigens in infected SCID mice reconstituted with normal spleen cells. Collectively, the data indicate that after TMEV infection, early generalized MHC Class I expression is mediated by IFN-alpha/beta independently of lymphocytes, but the differential regulation of H-2D over H-2K may be controlled by B and/or T lymphocytes.

Animals↗
PubMed1996

The locus-specific enhancer activity of the class I major histocompatibility complex interferon-responsive element is associated with a gamma-interferon (IFN)-inducible factor distinct from STAT1alpha, p48, and IFN regulatory factor-1.

Recent analyses of the upstream regulatory regions of the class I major histocompatibility complex genes in higher primates provided a generalized structural basis for the differential expression of A- and B-locus gene products in response to specific physiological stimulus. Among the regulatory sequences that differ between the loci is the interferon-responsive element (IRE). While the B-IRE is conserved, the A-IREs have species-specific sequence variation. We previously demonstrated that the B-IRE was an interferon (IFN)-inducible enhancer, whereas none of the A-IREs were functional. In the present study, we examined the biochemical basis for the enhancer activity of the conserved B-IRE and found that this may be attributed to a novel gamma-IFN-inducible factor. This factor accumulated in nuclei of cells within minutes of exposure to gamma-IFN. Its appearance was independent of de novo protein synthesis. However, it was not detected in nuclei of cells treated with herbimycin A, suggesting that its appearance depends on a protein kinase activation pathway. Supershift assays indicated that it was distinct from STAT1alpha, IFN regulatory factor-1, and p48, transcription factors known to bind IRE-like sequences found in regulatory regions of many non-major histocompatibility complex gamma-IFN-responsive genes. Competition assays show that this novel factor bound B-IRE with relatively high affinity, about 100-fold more than that for the A-IRE sequence. This factor was also present in STAT1alpha and p48 somatic mutants that also exhibited B-IRE enhancer activity in reporter gene bioassays in a manner similar to those seen with wild type cells. These observations indicate the existence of a novel gamma-IFN-dependent transcriptional activation pathway that correlates with the differential enhancer activity of the HLA-B IRE.

Benzoquinones↗
PubMed1996

A single T cell receptor recognizes structurally distinct MHC/peptide complexes with high specificity.

The 2C T cell is a CD8+, alloreactive T cell, which recognizes cells bearing Ld and Kbm3 class I major histocompatability complex molecules. Here, we characterize an allopeptide, designated dEV-8, that is a ligand in the Kbm3 molecule for the 2C TCR but is not a ligand in the Ld molecule. By biochemical and immunological properties, dEV-8 is distinct from P2Ca, the Ld allopeptide that is also recognized by the 2C TCR. Using the deduced amino acid sequence of dEV-8, we isolate a candidate endogenous source of the peptide. The endogenous protein, MLRQ, contains a peptide sequence identical to dEV-8. This degenerate recognition of two distinct peptide/MHC complexes by a single TCR has important implications for understanding allorecognition.

Amino Acid Sequence↗
PubMed1996

A monoclonal autoantibody which promotes central nervous system remyelination is highly polyreactive to multiple known and novel antigens.

A monoclonal antibody (mAb), designated SCH94.03, which promotes central nervous system remyelination in susceptible mice infected with Theiler's virus, has been proposed to be a natural autoantibody based on its germline immunoglobulin sequence. To identify the potential antigens recognized by mAb SCH94.03, a rat brain lambda gtll cDNA expression library was screened with this antibody. Nine independent clones were identified. Five clones were identical or highly similar to known cDNAs or proteins (rat kinesin light chain, mouse thrombospondin 1, mouse oncofetal antigen, RNA polymerase beta subunit and nuclear phosphoprotein). Four clones, designated REM#1, REM#2, REM#3 and REM#4, contained open reading frames, but were not homologous to any known genes or proteins. The reactivity of SCH94.03 with all nine clones was specific in that all nine clones identified contained continuous open reading frames and none of nine control IgM mAbs showed reactivity with any of the nine cDNA clones. The precise specificity of binding of mAb SCH94.03 was demonstrated by the absence of reactivity to the identified clones with IgM Ab from B cell lymphoma (CH12) which has identical cDNA sequences with mAb SCH94.03, but differ only in the heavy chain CDR3 N region. Our studies support the hypothesis that highly polyreactive natural autoantibodies can play a role in promoting central nervous system remyelination.

Actins↗
PubMed1995

Oligodendrocyte-reactive O1, O4, and HNK-1 monoclonal antibodies are encoded by germline immunoglobulin genes.

Natural or physiologic autoantibodies are present normally in serum, are polyreactive, are frequently of the IgM subtype, and are encoded by unmutated germline genes. We tested whether the oligodendrocyte-reactive O1, O4, A2B5, and HNK-1 IgM kappa monoclonal antibodies are natural autoantibodies by sequencing immunoglobulin (Ig) cDNAs and comparing these with published germline sequences. O1 VH was identical with unrearranged VH segment transcript A1 and A4. O4 VH had three and HNK-1 VH had six nucleotide differences from germline VH101 in the VH coding region. The D segment of O1 was derived from germline SP2 gene family. The D segments of O4 and HNK-1 were derived from DFL16 gene family. O4 JH and HNK-1 JH were encoded by unmutated germline JH4, whereas O1 JH was encoded by germline JH1 with one silent nucleotide change. O1 and O4 light chains were identical with myeloma MOPC21 except for one silent nucleotide change. HNK-1 V kappa was identical with germline V kappa 41 except for two silent nucleotide changes. O1 J kappa, O4 J kappa and HNK J kappa were encoded by unmutated germline J kappa 2. In contrast, A2B5 VH showed seven nucleotide differences from germline V1, whereas no germline sequence encoding A2B5 V kappa was identified. O1 and O4, but not A2B5 were polyreactive against multiple antigens by direct ELISA. Therefore, O1, O4 and HNK-1 Igs are encoded by germline genes, and have the genotype and phenotype of natural autoantibodies.

Amino Acid Sequence↗