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M B Lees

Publications and source records attributed to M B Lees.

At least 19 recordsLinked to original sources
PubMed1992

Identification and characterization of a second encephalitogenic determinant of myelin proteolipid protein (residues 178-191) for SJL mice.

We previously described a synthetic peptide of myelin proteolipid protein (PLP), peptide 139-151, which induces experimental allergic encephalomyelitis in SJL/J (H-2s) mice. We have now identified an additional determinant, PLP residues 178-191, that is also a potent encephalitogen in this strain. When PLP peptide 178-191 was compared with peptide 139-151 on an equimolar basis, the day of onset of disease induced by PLP 178-191 was earlier, but the incidence, severity, and histologic features were indistinguishable. Lymph node cells from animals immunized with the whole PLP molecule responded to both PLP 178-191 and 139-151, suggesting immunologic codominance of the two epitopes. PLP 178-191 elicited stronger proliferative responses and this may relate to the earlier onset of disease induced with this peptide. Two CD4+, peptide-specific, I-A(s)-restricted T cell lines, selected by stimulation of lymph node cells with either PLP 178-191 or 139-151, were each encephalitogenic in naive syngeneic mice. The presence of multiple encephalitogenic codominant PLP epitopes within a single mouse strain emphasizes the complexity of the immune response to PLP and its potential as a target Ag in autoimmune demyelinating diseases.

Amino Acid Sequence↗
PubMed1992

Experimental allergic encephalomyelitis mediated by cloned T cells specific for a synthetic peptide of myelin proteolipid protein. Fine specificity and T cell receptor V beta usage.

Proteolipid protein (PLP) is the major protein of central nervous system myelin. SJL (H-2s) mice immunized with a synthetic peptide corresponding to PLP residues 139-151 develop acute EAE. In this study, 6 IAs-restricted, CD4+, TCR alpha beta-bearing T cell clones were derived from SJL/J mice after immunization with this synthetic peptide. The clones responded in in vitro proliferative assays to the whole PLP molecule and to PLP peptide 139-151, but not to irrelevant Ag. They also responded to truncated and overlapping forms of the peptide but five distinct reactivity patterns were observed using these peptides. A panel of anti-TCR V beta mAb and TCR V beta-specific cDNA probes were used to determine the TCR V beta usage of the clones. Five clones were found to use four different V beta (V beta 2, V beta 6, V beta 10, or V beta 17a), whereas the V beta on the sixth clone could not be identified. Five of the clones induced EAE of varying severity upon adoptive transfer into naive syngeneic mice or mice pretreated with irradiation and pertussis and one clone was nonencephalitogenic. The Ag-specific proliferative response of all but the nonencephalitogenic clone could be blocked by an anti-CD4 mAb. Thus, the clones showed differences in their fine specifity, TCR V beta usage, sensitivity to antibody blocking, and encephalitogenic potency. These data demonstrate that the T cell response to the encephalitogenic PLP peptide 139-151 is heterogeneous.

Amino Acid Sequence↗
PubMed1992

Orientation of the myelin proteolipid protein C-terminus in oligodendroglial membranes.

The topology of the integral membrane proteolipid protein (PLP) has important structural and functional implications for central nervous system myelin. To determine the orientation of the carboxyl-terminal portion of PLP, cultured mouse oligodendrocytes were probed with polyclonal antibodies raised against a synthetic terminal peptide corresponding to PLP residues 264-276 and with ten separate monoclonal antibodies that react with this region. Cells were examined by double-label indirect immunofluorescence for the presence of the PLP C-terminus and either oligodendrocyte-specific surface or intracellular antigens. To detect surface antigens, both living and paraformaldehyde-fixed cells were incubated with primary antibodies and then stained with fluorochrome-conjugated second antibodies. Antigens located within the cytoplasmic space were identified after fixation and permeabilization of cells. Live-labeled oligodendrocytes were stained brightly for myelin-oligodendrocyte glycoprotein, galactocerebroside, and other surface markers but did not stain for the PLP C-terminus or the intracellular proteins myelin basic protein and beta-tubulin. Fixation alone was sufficient for partial permeabilization of oligodendrocytes to antibodies and resulted in limited staining of the PLP C-terminus and intracellular proteins. The permeabilized oligodendrocytes stained intensely for the PLP C-terminus, myelin basic protein, and beta-tubulin. Finally, trypsinization of living oligodendrocytes eliminated surface myelin-oligodendrocyte glycoprotein staining but did not change the immunostaining properties of the PLP C-terminus. These results provide evidence that the carboxyl-terminus of PLP is located at the cytoplasmic face of oligodendroglial membranes.

Amino Acid Sequence↗
PubMed1992

Myelin proteolipid protein: minimum sequence requirements for active induction of autoimmune encephalomyelitis in SWR/J and SJL/J mice.

Proteolipid protein (PLP) is the major protein constituent of mammalian central nervous system myelin. We have previously identified two different PLP encephalitogenic T cell epitopes in two mouse strains. Murine PLP peptides 103-116 YKTTICGKGLSATV and 139-151 HCLGKWLGHPDKF are encephalitogenic determinants in SWR/J (H-2q) and SJL/J (H-2s) mice, respectively. The purpose of the present study was to determine the minimum sequence requirements for each of these PLP encephalitogens. In SWR/J mice, at least two distinct overlapping peptides can induce experimental autoimmune encephalomyelitis (EAE). The eleven residue sequences PLP 105-115 TTICGKGLSAT and PLP 106-116 TICGKGLSATV are encephalitogenic in SWR/J mice, but PLP 106-115 TICGKGLSAT, the decapeptide indigenous to both sequences, is non-encephalitogenic. In contrast, the shortest PLP sequence capable of inducing EAE in SJL/J mice is the nonapeptide 141-149 LGKWLGHPD. These data indicate that encephalitogenic determinants of PLP are short contiguous peptide sequences similar in length and diversity to those of MBP.

Amino Acid Sequence↗
PubMed1991

Parental MHC molecule haplotype expression in (SJL/J x SWR)F1 mice with acute experimental allergic encephalomyelitis induced with two different synthetic peptides of myelin proteolipid protein.

To determine if the Ag that induces an autoimmune disease influences parental MHC haplotype molecule expression in situ in MHC heterozygotes, acute experimental allergic encephalomyelitis (EAE) was induced with different encephalitogenic peptides in (SJL/J x SWR)F1 mice. The mice were sensitized with either a synthetic peptide corresponding to mouse myelin proteolipid protein (PLP) residues 103-116 YKTTICGKGLSATV which induces EAE in SWR (H-2q), but not SJL/J (H-2s) mice or a synthetic peptide corresponding to PLP residues 139-151 HCLGKWLGHPDKF which is encephalitogenic in SJL/J but not SWR mice. Mice were killed when they were moribund or at 30 days after sensitization. Twelve of 18 F1 mice given PLP peptide 103-116 and 12 of 17 mice given PLP peptide 139-151 developed EAE within 2 to 3 wk after sensitization. Cryostat sections of brain samples from F1 and parental mice were immunostained with a panel of mAb identifying H-2s and H-2q class I and II MHC molecules. In brains of controls, class I MHC molecules were expressed on choroid plexus, endothelial cells, and microglia whereas class II MHC molecules were absent. In EAE lesions, class I and II MHC molecules were present on inflammatory and parenchymal cells, but the degree of parental haplotype molecule expression did not vary with the different peptide Ag tested. Thus, in (SJL/J x SWR)F1 mice, myelin PLP peptides 103-116 and 139-151 are co-dominant Ag with respect to clinical and histologic disease and parental haplotype MHC molecule expression. We propose a unifying hypothesis consistent with these results and previous observations of differential Ia expression in (responder x non-responder)F1 guinea pigs. We suggest that MHC molecules may bind locally derived peptide Ag in inflammatory sites and that these interactions influence levels of MHC haplotype molecules on APC.

Amino Acid Sequence↗
PubMed1991

Distribution of proteolipid protein and myelin basic protein in cultured mouse oligodendrocytes: primary vs. secondary cultures.

The distribution of proteolipid protein (PLP) and myelin basic protein (MBP) was examined in differentiating oligodendrocytes of primary and secondary mouse brain cell cultures by single- and double-label indirect immunofluorescence. In primary cultures, MBP and PLP were differentially located in oligodendrocytes. MBP became concentrated as fine punctate dots lining the edges of processes and as coarse grains in flattened sheet-like structures. PLP was distributed diffusely throughout cell bodies and processes but was limited to the perimeter of sheets and some processes within sheets. To compare the detailed distribution of PLP and MBP in the absence of underlying cells, a simple method for the growth of isolated oligodendrocytes in secondary cultures was developed. Cells were maintained in primary culture for 39-41 days, harvested by scraping, enriched for oligodendrocytes, and plated at low cell density. After 1 week, isolated oligodendrocytes had developed long processes and large flattened membranous sheets. MBP and PLP were differentially localized in these cell structures. The sheets contained fine-grained patches of MBP, which were surrounded by networks of MBP- processes. In contrast, PLP was initially seen throughout the cell bodies and processes. In older cultures, PLP became strikingly concentrated in curvilinear membranous profiles. The observations show that PLP and MBP are differentially located in cultured mouse oligodendrocytes. Furthermore, the precise distribution of these myelin-specific antigens is dependent on culture conditions.

Animals↗
PubMed1991

Fatty acid composition of human myelin proteolipid protein in peroxisomal disorders.

Myelin proteolipid protein (PLP) is an acylated protein which contains approximately 2 mol of ester-bound fatty acids. In this study, the amount and composition of fatty acids covalently bound to human myelin PLP were determined during development and in peroxisomal disorders. Palmitic, oleic, and stearic acids accounted for most of the PLP acyl chains. However, in contrast to PLP in other species, human PLP contains relatively more very long chain fatty acids (VLCFA). The fatty acid composition remained essentially unchanged between 1 day and 74 years of age. The total amount of fatty acid bound to PLP was not altered in any of the pathological cases examined. However, in the peroxisomal disorder adrenoleukodystrophy, the proportions of saturated and, to a lesser extent, monounsaturated VLCFA bound to PLP were increased at the expense of oleic acid. Smaller, but significant, changes were observed in adrenomyeloneuropathy. The reduction in the levels of oleic acid was also observed in two other peroxisomal disorders, the cerebrohepatorenal (Zellweger) syndrome and neonatal adrenoleukodystrophy, as well as in the lysosomal disorder Krabbe globoid cell leukodystrophy. However, in these disorders, the decrease in oleic acid occurred at the expense of stearic acid, and not VLCFA. The results indicate that, although a characteristic PLP fatty acid pattern is normally maintained, changes in the acyl chain pool can ultimately be reflected in the fatty acid composition of the protein. The altered PLP-acyl chain pattern in peroxisomal disorders may contribute to the pathophysiology of these devastating disorders.

Adrenoleukodystrophy↗
PubMed1991

Monoclonal antibodies against myelin proteolipid protein: identification and characterization of two major determinants.

This report describes the preparation and characterization of a panel of monoclonal antibodies (mAbs) against the myelin proteolipid protein (PLP). A Lewis rat was immunized with bovine proteolipid apoprotein and 27 mAbs were selected based on their reactivity against bovine PLP on enzyme-linked immunosorbent assays. Eleven mAbs recognized the PLP carboxyl-terminal sequence when tested against a panel of synthetic peptides in a solid-phase assay. A carboxyl-terminal pentapeptide (residues 272-276) was sufficient for antibody binding and the terminal phenylalanine residue was found particularly important. Deletion, modification, or replacement of this residue markedly reduced or obliterated antigen-antibody interaction. Nine mAbs reacted with a second antigenic determinant, residues 209-217, but these could be identified only by competitive immunoassays. This peptide was a more effective inhibitor than the longer peptides 202-217 and 205-221, suggesting that flanking residues may interfere with peptide-antibody interaction. Seven antibodies did not react with any of the synthetic peptides tested and their determinants remain unidentified. Immunoblot analysis showed that the mAbs reacted with both the PLP and the DM-20 isoforms. Twenty-three of the mAbs were of the immunoglobulin G2a or b isotype; the remaining antibodies were immunoglobulin M and all of these were specific for residues 209-217. Cultured murine oligodendrocytes were stained by most of the mAbs tested, but the most intense reactivity was observed with the carboxyl-terminus-specific mAbs. The immunocytochemical analyses demonstrate that the mAbs react with the native PLP in situ and show their potential usefulness for studies of the cell biology of myelin and oligodendrocytes.

Amino Acid Sequence↗
PubMed1991

Induction of experimental allergic encephalomyelitis by myelin proteolipid-protein-specific T cell clones and synthetic peptides.

Proteolipid protein (PLP) is the major protein of central nervous system (CNS) myelin. SJL(H-2s) mice immunized with a synthetic peptide corresponding to PLP residues 139-151 (HSLGKWLGHPDKF) develop acute experimental allergic encephalomyelitis (EAE). In the present study a T cell line and 4 clones were derived from SJL/J mice following immunization with this synthetic peptide. Severe clinical and histological EAE could be induced by adoptive transfer of the peptide-specific T cell line and 3 of 4 T cell clones. The T cell line/clones all responded strongly to PLP peptide 139-151 in in vitro proliferative assays. However, two different reactivity patterns emerged when truncated PLP peptides 141-150 and 141-149 were tested, suggesting that more than 1 epitope may be present within the PLP 139-151 determinant. To evaluate the encephalitogenic potential of the truncated peptides, we compared the ability of 2 truncated PLP peptides to induce EAE in vivo and proliferative responses in vitro. Immunization with PLP peptide 141-150 induced acute EAE in about 70% of mice tested, but PLP peptide 141-149 induced a comparatively mild form of EAE in 4 out of 9 mice tested. Lymph node cells from mice immunized with these peptides showed in vitro proliferative responses to each of the peptides, but the response to peptide 139-151 was always strongest. These combined in vivo and in vitro data further define the epitopes involved in PLP-induced EAE in SJL mice. Furthermore, the availability of multiple PLP-specific T cell clones will enable us to study the diversity of the T cell repertoire to PLP.

Amino Acid Sequence↗
PubMed1990

Acute experimental allergic encephalomyelitis in SJL/J mice induced by a synthetic peptide of myelin proteolipid protein.

Clinical, histologic, and ultrastructural characteristics of acute experimental allergic encephalomyelitis (EAE) induced by sensitization with a synthetic peptide corresponding to mouse myelin proteolipid protein (PLP) residues 139-151 HCLGKWLGHPDKF were studied in SJL/J mice. Groups of mice were immunized with 20, 50, or 100 nmol of the peptide and were killed from seven to 28 days after sensitization or when they were moribund. Beginning on Day 9, the mice showed signs of EAE and the disease progressed rapidly to paralysis. Central nervous system (CNS) inflammation, edema, gliosis, and demyelination were found in all mice killed between Days 10 and 28 and white matter lesion areas correlated with clinical score at the time the mice were killed. Peripheral nerve roots and the cauda equina did not have lesions. Within the range studied, the severity of clinical or histologic disease was the same regardless of the PLP peptide dose. Two of ten mice immunized with 100 nmol and none of 14 mice given smaller doses of a synthetic peptide of mouse myelin basic protein (MBP) showed clinical EAE. These mice had small numbers of CNS lesions that were indistinguishable from those in PLP peptide-sensitized mice. These findings demonstrate that immunization of SJL/J mice with PLP peptide 139-151 produces a disease with the clinical and morphologic features of CNS tissue-, whole PLP-, whole MBP-, and MBP peptide-induced acute EAE. Thus, PLP is a major encephalitogen and immune reactions to epitopes of different myelin proteins may induce identical patterns of injury in the CNS.

Acute Disease↗
PubMed1989

Identification of thiol groups and a disulfide crosslink site in bovine myelin proteolipid protein.

The existence of disulfide crosslinks limits the number of possible folded structures a protein can assume. Thus localization of disulfide and thiol groups is a key to understanding the conformation and orientation of myelin proteolipid protein (PLP) in the myelin membrane. [14C]Carboxamidomethylated PLP was fragmented with chymotrypsin, and the resulting mixture was partially separated by reversed-phase HPLC. Purified 14C-labeled peptides and a disulfide containing peptide were characterized by amino acid analysis. These experiments showed that Cys-32 and Cys-34 are free thiols, and are presumably on the interior of the cell or within the membrane bilayer, and that Cys-200 and Cys-219 are joined by a disulfide bond, and are probably located on the extracellular face of the membrane. Sequence analysis experiments indicate that Cys-5, Cys-6 and Cys-9 are linked by disulfides, probably to other parts of the protein on the extracellular face of the membrane.

Amino Acids↗
PubMed1989

Identification of an encephalitogenic determinant of myelin proteolipid protein for SJL mice.

PLP is the major protein constituent of central nervous system myelin. We have previously shown that SJL/J (H-2s) mice develop an acute form of EAE after immunization with PLP. The purpose of the present study was to identify an encephalitogenic determinant of PLP for SJL mice. We immunized SJL/J mice with a synthetic peptide identical to residues 130-147 QAHSLERVCHCLGKWLGH of murine PLP, a sequence having an amphipathic alpha-helical conformation. Although it did not induce disease, an overlapping peptide containing residues 139-154 HCLGKWLGHPDKFVGI was encephalitogenic. Immunization with this peptide induced severe clinical and histologic EAE in 3 of 20 mice. T cell enriched ILN cells from these mice responded specifically (3H-thymidine incorporation) to this peptide as well as to shorter analogues of this domain containing serine in place of cysteine at residues 138 and 140. Immunization with the serine-substituted PLP peptides 137-151 VSHSLGKWLGHPDKF and 139-151 HSLGKWLGHPDKF induced severe, acute EAE in 4 of 9 and 15 of 15 SJL mice, respectively, and their T cell enriched ILN cells responded not only to the analogues, but also to the native PLP sequence 139-154. These results indicate that residues 139-151 of murine PLP is an encephalitogenic determinant for SJL mice. Furthermore, like the PLP encephalitogenic domain for SWR (H-2q) mice, this determinant is also a T cell epitope with a coding sequence at the end of an exon.

Amino Acid Sequence↗
PubMed1989

Separation of the major proteins of central and peripheral nervous system myelin using reversed-phase high-performance liquid chromatography.

A general method to separate the major proteins of rat central and peripheral nervous system myelin has been developed. The key step is the initial quantitative removal of the lipids under conditions where the proteins retain their solubility in HPLC solvents. Lipids are removed by a combination of solvent extraction and column chromatography on Sephadex LH-60 in 2-chloroethanol:10 mM HCl (9:1). Proteins are then separated by reversed-phase (RP) HPLC. Samples are applied to a wide pore reversed-phase C-3 column and eluted with a linear gradient of 10-70% 1-propanol in 0.1% trifluoroacetic acid (0-100% B) over a 60-min period. Myelin basic proteins elute between 25 and 30% B, Wolfgram and other high molecular weight proteins at 35-50% B, proteolipid protein at 65-80% B, and P0 glycoprotein at 55-65% B. This elution pattern is consistent with the known relative hydrophobicity of these proteins. Protein recovery for the entire procedure is greater than 74%. Proteolipid and P0 proteins isolated by HPLC contain 2.3 and 1.1 mol of covalently bound fatty acids, respectively. This fatty acid composition is similar to that previously reported using different isolation procedures. The analysis of central and peripheral nervous system myelin proteins by RP-HPLC permits the isolation of purified proteins for structural and metabolic experiments.

Animals↗
PubMed1988

A synthetic peptide from myelin proteolipid protein induces experimental allergic encephalomyelitis.

Immunization of animals with proteolipid protein, the major protein constituent of central nervous system myelin, produces experimental allergic encephalomyelitis. The goal of the present study was to identify an encephalitogenic determinant of this protein. For this purpose, SWR mice were immunized with five groups of pooled synthetic peptides corresponding to various regions of the myelin proteolipid protein sequence. Clinical EAE was observed in only one group. Inguinal lymph node cells from animals in this group responded ([3H]thymidine incorporation) to a peptide within the pool containing residues 103-116 YKTTICGKGLSATV. Mice subsequently immunized with 50 nmol of this peptide developed severe EAE within 3 wk, and their T cell-enriched inguinal lymph node cells responded specifically to this peptide. Control mice immunized to proteolipid peptide 202-217 DARMYGVLPWNAFPGK did not develop experimental allergic encephalomyelitis, and their inguinal lymph node cells were unresponsive to either peptide. Thus, a peptide corresponding to a sequence within the proteolipid protein can produce classical acute experimental allergic encephalomyelitis. This is the first report of a synthetic encephalitogenic peptide from myelin proteolipid protein.

Amino Acid Sequence↗
PubMed1988

Myelin proteolipid protein-induced experimental allergic encephalomyelitis. Variations of disease expression in different strains of mice.

Strains of mice with diverse genetic backgrounds were tested for susceptibility to experimental allergic encephalomyelitis (EAE) induced by myelin proteolipid protein. EAE was elicited in all strains of mice tested, but the clinical and histologic features varied. SJL (H-2s) mice had a high incidence of both clinical and histologic disease characterized by early onset of clinical signs. Inguinal lymph node T cells from diseased animals responded specifically [( 3H]thymidine incorporation) to proteolipid protein and not to myelin basic protein. In contrast, BALB/c (H-2d), DBA/1 (H-2q), C57BL/6 (H-2b), AKR (H-2k), CBA (H-2k), C3H (H-2k), B10.BR (H-2k), and C57BR (H-2k) mice showed a later onset of clinical signs and typically a lower disease incidence. However, the most marked variations in disease incidence occurred among BALB/c (H-2d) substrains in which the incidence of EAE ranged from eight of nine (BALB/cPt) to complete resistance (BALB/cWt and BALB/cORNL). Because these BALB/c substrains were initially derived from the same inbred genetic source and are serologically identical at H-2, these results suggest that expression of proteolipid protein-induced EAE in the mouse involves additional loci outside the MHC.

Animals↗
PubMed1988

Immunochemical characterization of antibodies to the myelin proteolipid protein (PLP).

The immunochemical specificity of antibodies raised against the bovine myelin proteolipid protein (PLP) and a series of PLP synthetic peptides was examined by enzyme-linked immunosorbent assay (ELISA) and immunoblot analyses. Polyclonal rabbit anti-bovine PLP antibodies were cross-reactive with PLP isolated from rat, monkey, and human CNS white matter, as well as with PLP incorporated into rat myelin vesicles. Immunochemical analyses of 11 anti-peptide antisera revealed a more restrictive cross-reactivity pattern with only five of the 11 antisera, against peptides encompassing residues 48-59, 97-105, 183-193, 192-200 and 264-276, cross-reacting with bovine PLP by ELISA. Immunoblot analyses with the anti-peptide antisera demonstrated a similar recognition with four of the 11 antisera against peptides 48-59, 97-105, 192-200 and 264-276 recognizing the myelin PLP. These data suggest that, despite its strong phylogenetic conservation, multiple antigenic sites exist within the PLP molecule, and some of these determinants can be mimicked by synthetic peptides. However, the restrictive cross-reactivities of the anti-peptide antisera suggest that humoral recognition of the myelin PLP is conformationally dependent. The availability of anti-peptide antibodies of predetermined specificity, capable of recognizing the intact protein, should permit detailed examination of PLP topography in various experimental systems.

Amino Acid Sequence↗
PubMed1987

Autoacylation of myelin proteolipid protein with acyl coenzyme A.

Rat brain myelin proteolipid protein (PLP) is known to contain long chain, covalently bound fatty acids. In the course of characterizing the mechanism of acylation, we found that the isolated PLP, in the absence of any membrane fraction, was esterified after incubation with [3H]palmitoyl coenzyme A (CoA). This observation demonstrated that the protein acts as both an acylating enzyme and an acceptor. Thus, acylation occurs by an autocatalytic process. The possibility of a separate acyltransferase that copurifies with PLP was essentially excluded by adding brain subcellular fractions to the reaction mixtures and by changing the isolation procedure. After deacylation, the protein was acylated at a 4-fold greater rate, suggesting that the original sites were reacylated. The palmitoyl-CoA concentration followed Michaelis kinetics, confirming that spontaneous acylation was not occurring. Pulse-chase experiments indicated that the reaction entails net addition of acyl groups. Although fatty acids are bound via an O-ester linkage, free SH groups are required in the reaction. Denaturation of the protein by sodium dodecyl sulfate or heat inhibits the reaction, whereas cerulenin has little or no effect. PO, the major protein in peripheral nerve myelin, is also an acylated protein, but it was not labeled upon incubation of either peripheral myelin or the isolated protein with [3H]palmitoyl-CoA, demonstrating that it is acylated by a different route. Several synthetic peptides derived from PLP sequences with sites known to be acylated in vivo as well as a series of deacylated PLP tryptic peptides were not labeled, indicating that integrity of the protein is required for acylation. Limited proteolysis and peptide mapping showed that the same sites are acylated in vitro or in vivo, suggesting that the autocatalytic acylation reaction is physiological.

Acyl Coenzyme A↗