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R Lebar

Publications and source records attributed to R Lebar.

17 recordsLinked to original sources
PubMed1992

T-cell receptor identification of an oligodendrocyte-specific autoreactive cytotoxic T-cell clone without self restriction.

In addition to myelin basic protein (MBP) and proteolipid protein (PLP), oligodendrocyte (Od) membrane autoantigens, such as the glycoprotein M2/MOG, could participate in the pathogenesis of autoimmune demyelinating diseases of the central nervous system (CNS), such as experimental allergic encephalomyelitis (EAE) or multiple sclerosis (MS). We have described an Od-specific autoreactive and cytotoxic T-cell clone, named C2, which recognized M2/MOG without conventional MHC restriction. In order to analyse the Od/C2 interaction, we determined the alpha/beta T-cell receptor (TCR) variable region usages and structures of C2. Monoclonal antibody stainings of C2 and nucleotide sequences show that the alpha chain is composed of a V alpha 5 and a J alpha identical to J alpha 18BBM142 gene segments, and that the TCR beta chain is composed of V beta 17a, D beta 2.1 and J beta 2.2 gene segments indicating that C2 used a conventional alpha/beta TCR for M2/MOG recognition.

Amino Acid Sequence↗
PubMed1989

Chronic experimental autoimmune encephalomyelitis in the guinea pig. Presence of anti-M2 antibodies in central nervous system tissue and the possible role of M2 autoantigen in the induction of the disease.

Experimental autoimmune encephalomyelitis (EAE) can be transferred adoptively with T cells sensitized to the basic protein of myelin (BP). However, in the guinea pig, the chronic form of EAE has not been found to be inducible with BP alone, nor has it been adoptively transferred. An antibody response to the central nervous system (CNS) myelin autoantigens was looked for in serum and target CNS tissue in S13 guinea pigs with isologous CNS tissue-induced chronic EAE. Antibody activity was estimated by an immunoenzymatic technique and by autoradiography, using immunoprecipitated and electrophoresed relevant radiolabelled antigens. In serum, IgG antibody response to BP and M2 reached its maximum level 30 to 40 d after immunization and then declined progressively until it became undetectable. On the other hand, while anti-BP antibodies were seldom detected in CNS tissue acid extract, anti-M2 IgG antibodies were always present in CNS tissue of chronic EAE animals, and the amount of these antibodies were related to the severity of symptoms and lesions. No antibody response to proteolipid or to galactocerebroside was detected in serum or CNS tissue. BP-immunized controls showed no chronic EAE and no response to M2 in their serum or CNS tissue. Inasmuch as M2 has been shown to be a glycoprotein of CNS myelin, and anti-M2 antibodies to have a demyelinating property, the latter would be responsible for CNS tissue demyelination in chronic EAE. A shared role of BP and M2 in the induction of chronic EAE in the guinea pig is suggested.

Animals↗
PubMed1989

Oligodendrocyte-specific autoreactive T cells using an alpha/beta T-cell receptor kill their target without self restriction.

The oligodendrocyte (Od), a glial cell that produces myelin in the central nervous system, may be a target for autoreactive T cells in autoimmune demyelinating processes, although not expressing major histocompatibility complex (MHC) products. To analyze Od-T-cell interactions, we selected from normal SJL/J mouse splenocytes sensitized in vitro by Lewis rat Od a T-cell clone, named C2, exhibiting a surface phenotype of mature T cell (Thy 1+, CD3+, CD8+, CD4-, asialo-GM1-). C2 T cells displayed a specific cytotoxicity to syngeneic Od as well as to rat Od, but not to astrocytes or lymphoblasts, or to YAC-1 cells, a target for natural killer and lymphokine-activated killer activity. The T-cell receptor of clone C2 was found to be a CD3-associated alpha/beta-chain heterodimer similar to that usually expressed by antigen-specific MHC-restricted mature T cells. Attempts to block the C2-mediated cytolysis by a series of monoclonal antibodies showed that both the CD3-T-cell receptor complex and the CD8 accessory molecule were required for OD-T-cell interaction and confirmed the lack of involvement of polymorphic MHC products as epitope-presenting structures. Antibodies directed against a surface Od glycoprotein, previously shown to elicit demyelinating autoantibodies in experimental autoimmune encephalomyelitis, fully blocked the cytotoxicity of T-cell clone C2 to its Od target. These data suggest that an epitope of a surface Od glycoprotein may be directly and specifically recognized and killed by autoreactive T cells expressing an alpha/beta receptor without conventional MHC restriction.

Animals↗
PubMed1987

[Demyelination and autoimmunity].

Autoimmune diseases are experimental models of human demyelinating diseases such as multiple sclerosis and idiopathic polyneuritis: experimental auto-immune encephalomyelitis (EAE) and experimental autoimmune neuritis. Demyelinating lesions occurring in chronic EAE could be due to the action of autoantibodies rather than to a cellular action involving lymphokines. An antibody-dependent cellular myelinotoxicity could also be the mechanism responsible for demyelination; these mechanisms are suggested by in vitro and in vivo demyelination experiments and by the presence of demyelinating autoantibodies against component(s) of myelin in EAE area. The demyelinating mechanisms could be the same in multiple sclerosis. However, they have not been proven so far.

Animals↗
PubMed1986

The M2 autoantigen of central nervous system myelin, a glycoprotein present in oligodendrocyte membrane.

Autoantibodies with in-vitro demyelinating capacity induced in Hartley and strain 13 guinea pigs with homologous central nervous system (CNS) tissue were used to characterize the target autoantigen M2. Using the Dot Immunobinding technique, M2 was found to be a component of CNS myelin different from basic protein (BP) and from cerebroside. The expression of M2 on oligodendrocytes, cells known to produce CNS myelin, also confirmed that M2 was a component of CNS myelin. Furthermore, the autoradiography of immunoprecipitates formed with radiolabelled guinea pig myelin and analysed in sodium dodecyl sulphate gels showed that M2 was specific to CNS myelin and absent in peripheral nervous system (PNS) myelin. On electrophoresis M2 appeared as two CNS myelin protein bands at the 27 and 54 KD molecular weight levels, distinct from the major protein bands of proteolipid and BP. M2 bands were of glycoprotein nature, as was demonstrated by affinity chromatography of CNS myelin on wheat germ agglutinin (WGA)-Sepharose. A monoclonal antibody induced by BP-free CNS glycoproteins recognized the same bands as anti-M2 serum in guinea pig CNS myelin. This would imply that both M2 bands share common determinants. M2 bands similar to the above in guinea pig were also shown in rat, rabbit and bovine CNS myelin with guinea pig antibodies. The same type of anti-M2 antibodies were induced in rabbit immunized with homologous CNS tissue. Although only a minor component of myelin, M2 is strongly immunogenic compared to BP. M2 antigen could thus be the target of chronic demyelinating processes such as experimental allergic encephalomyelitis.

Animals↗
PubMed1985

Dot immunobinding as a tool for the study of the CNS myelin antigen, M2.

The unidentified antigen M2, which is the target of demyelinating antibodies in sera from guinea pigs immunized with brain tissue, was studied using a dot immunobinding assay. This method is particularly appropriate for studying the immunologic properties of insoluble brain components such as myelin, glycolipids and myelin proteins. M2 was found to be a component of central nervous system myelin and not peripheral myelin. It appeared at the time of myelination, was not cerebroside or GM1 ganglioside and did not cross-react with the major myelin proteins, i.e. proteolipid or basic protein. These observations confirm and extend previous studies using a complement fixation assay for M2. The antigen was shown to be partially solubilized by Brij 35 and this detergent can provide a starting point for attempts at purification.

Animals↗
PubMed1984

Participation of encephalitogen in incomplete Freund's adjuvant in the induction of experimental allergic encephalomyelitis in Hartley guinea pigs.

The addition of complete Freund's adjuvant (CFA) to encephalitogen is required for the induction of experimental allergic encephalomyelitis (EAE). On the other hand, administration of encephalitogen in incomplete Freund's adjuvant (IFA) protects the animal from the development of EAE. It is shown in this work that injection of homologous central nervous system (CNS) tissue or myelin basic protein (BP) in IFA, before challenge with CNS tissue in CFA, accelerated the onset of the disease in Hartley guinea pigs. It also appeared to protect the animals, however, because 22% of the group did not develop EAE at all, and in those which did, the disease was not as lethal as in controls. To produce this accelerated form of EAE with encephalitogen in IFA required (1) a time interval shorter than 9 days between the first injection and challenge and (2) that the first injection and the challenge be done in the same site, which could be hind or front foot pads but not the nuchal area. The results indicated that 'priming' by encephalitogen in IFA occurred when this two-step induction procedure was used. The experimental conditions may have bypassed suppressive mechanisms.

Animals↗
PubMed1981

Tentative identification of a second central nervous system myelin membrane autoantigen (M2) by a biochemical comparison with the basic protein (BP).

Two central nervous system myelin autoantigens, M2 and basic protein (BP), were examined, using complement-fixing antibodies against each autoantigen as markers on myelin. M2 activity was very labile and very insoluble, PB activity was very resistant. Trypsin reduced both activities an this reduction was greater after phospholipase treatment. Both activities were slightly solubilized in 8 M urea. It is known that BP is not present on the surface of myelin and is considered a peripheral membrane protein. M2 appears to be a surface and integral membrane protein, and as such resembles Folch Pi proteolipid protein. The relationship between M2 and BP requires further study.

Animals↗
PubMed1976

Studies on autoimmune encephalomyelitis in the guinea pig. II. An in vitro investigation on the nature, properties, and specificity of the serum-demyelinating factor.

Complement-dependent demyelinating activity of whole brain homogenate (WBH)-induced experimental allergic encephalomyelitis (EAE) sera was tested on long term tissue cultures of in vitro myelinated fetal guinea pig cerebellum. Complement-fixing (CF) auto-antibodies were shown to be the responsible agents, as demonstrated in experiments where all reagents belonged to the same species: guinea pigs of outbred (Hartley) and even of inbred (S2 or S13) strains. These antibodies were of the IgG2 class as shown by Sephadex G-200 and DEAE cellulose fractionation experiments. The corresponding auto-antigen was present in the homogenate and myelin of the central nervous system (CNS) tissue. It was different from the encephalitogenic basic protein of CNS myelin (BP), as shown in experiments where the demyelinating auto-antibodies were induced, detected, and absorbed by WBH or by CNS myelin but not by BP. They were neither induced by nor cross-reacting with cerebroside and peripheral nervous system (PNS) tissue.

Animals↗