Inhibition by serum of encephalitogenic activity of myelin basic protein.

Basic protein of myelin from bovine brain (B-BPM) in Freund's complete adjuvant (FCA) is highly encephalitogenic for the guinea pig. However, when B-BPM is mixed with serum from various species it loses its encephalitogenic effect but not its immunogenic properties. When the synthetic tryptophan peptide matching residue 115-126 of human BPM is mixed with normal human serum it loses both its encephalitogenic and immunogenic effects. The time of exposure to serum necessary for complete inhibition of encephalitogenic activity of B-BPM varied: rat, horse, sheep and human sera produced their inhibitory effect immediately after mixing, whereas guinea pig serum required 8h. The capacity of serum to abrogate the encephalitogenic effects of B-BPM was not due to complete degradation of the molecule by proteinases in serum, because all animals injected with the B-BPM serum mixture gave cutaneous delayed hypersensitivity reactions to B-BPM. The inhibitory effect could be attributed to a factor in serum which is non-dialysable, thermostable at 56 degrees C, for 1 h, and present in high concentration in fetal calf serum. It may be an alpha2 macroglobulin which can act selectively on the main encephalitogenic determinant, around or within residues 115-126 of the basic protein of myelin.     

Interstrain cross-reactive idiotypes on monoclonal antibodies to an encephalitogenic myelin basic protein peptide.

In order to assess the role of idiotype (Id) and the anti-Id network in murine experimental autoimmune encephalomyelitis (EAE), Id-bearing monoclonal antibodies (mAb) to human myelin basic protein (MBP) peptide acetyl 1-9, as well as mAb anti-Id, were developed in EAE-susceptible PL/J mice (H-2u). These mice recognize MBP residues acetyl 1-9 as an encephalitogenic determinant. Reactivities of PL/J Id-bearing mAbs to MBP and to MBP peptides were identical to those of mAbs generated against the same MBP peptide in EAE-resistant BALB/c mice (H-2d), even though isotypes of the mAbs differed. By using an inhibitory ELISA and immunoblotting, it was demonstrated that one PL/J mAb anti-Id recognized a public or framework Id, whereas another PL/J mAb-anti Id was directed to a private Id more restricted to the paratopic site. Two Id-bearing PL/J mAbs shared a cross-reactive Id (IdX) on the light chain, and an interstrain IdX was present on both the heavy and light chains of mAbs raised in PL/J and BALB/c mice to the same MBP peptide. The PL/J mAb anti-Id was capable of cross-regulating the production of Id-bearing mAbs by hybridomas across murine strains. These findings suggest that a restrictive family of germ-line genes encode for these Id-bearing antibodies to MBP peptide, irrespective of whether the MBP peptide is encephalitogenic in the murine strain immunized. Manipulation of the Id network may provide a means for modifying autoimmune demyelinating diseases of the central nervous system.     

Blocking the encephalitogenic activity of the C-terminal part of the basic myelin protein in rabbits by treatment with serum.

Peptides HNB-92-169 and 116-169, tyr, derivatives of the C-terminal part of bovine myelin basic protein, sensitize rabbits for experimental allergic encephalomyelitis (EAE). Dissolving these peptides in heat-inactivated normal guinea-pig, human, or monkey serum immediately before emulsification with Freund's complete adjuvant (FCA) abrogated their disease-inducing activity. Dissolving them in homologous or autologous serum only slightly affected the encephalitogenicity.     

Binding of encephalitogenic basic protein by serum alpha-globulins

The binding capacity of human and rabbit serum and serum fractions for [¹²⁵I]encephalitogenic basic protein, extracted from human brain, were determined by gel-filtration radioimmunoassay. Strong binding was effected by the γ-globulin fraction or whole serum of a rabbit with experimental allergic encephalitis, and was completely inhibited by excess of unlabelled encephalitogenic basic protein but not by large amounts of lysozyme. Smaller amounts of encephalitogenic basic protein were bound by normal rabbit and human serum, and by the serum of a patient with multiple sclerosis: the α₂-macroglobulin fraction was responsible for this, and complete inhibition was effected by excess unlabelled encephalitogenic basic protein but only partial inhibition by excess lysozyme. It is concluded that binding detected in some radioimmunoassay systems may not represent a classical antigen—antibody reaction, and it is suggested that α-macroglobulins may, by binding in vivo, be of importance in experimental allergic encephalomyelitis and, by analogy, in human demyelinating disease.     

T-cell recognition of myelin basic protein

Multiple sclerosis is a chronic inflammatory disease of the central nervous system which has been hypothesized to be autoimmune in nature. To test whether this is the case, Kai Wucherp fennig and colleagues have developed a set of criteria that must be met to satisfy the hypothesis. Here, they present these criteria and assess the extent to which studies to date satisfy them.     

Heterogeneity of rat encephalitogenic T cells elicited by variants of the myelin basic protein (68–86) peptide

By immunizing Lewis rats with myelin basic protein (MBP) peptide variants derived from the major encephalitogenic epitope of guinea pig (MBP(68–88) and then isolating encephalitogenic T cells from these animals, we demonstrated that the variant peptides do not elicit the same encephalitogenic T cell subsets as those induced by the wild-type peptide or by intact MBP. Rather, the pathogenic T cells differed in clonal composition as reflected by their heterogeneous responses to a panel of variant peptides and by their T cell receptor usage. Thus, molecules mimicking the MBP(68–88) autoantigen can elicit pathogenic T cell subsets without necessarily cross-reacting with T cells specific for the original autoantigen. This suggests that a more clonally diverse group of pathogenic T cells might be involved in EAE than has been apparent from studies with intact MBP or its unaltered peptides.     

In vitro carboxymethylation of myelin basic protein

During a study to find natural substrate proteins of carboxymethylation, myelin basic protein was found to be a good substrate. The two protein carboxymethylases were purified partially using myelin basic protein as a substrate. These two enzymes may be identical with protein carboxymethylase I and II, which have been found to methylate gamma-globulin. The Km of myelin basic protein (25 microM) was very small compared with other substrates. The activities of the two carboxymethylases were high in the rat brain in comparison to the other rat organs. The activity increased during the period of myelination in the rat brain. These findings suggest that carboxymethylation of myelin basic protein may play an important role in myelination.     

Immuno-electron microscopic localisation of caveolin 1 in human placenta

We have localised the placental endothelial marker caveolin-1 at the ultrastructural level using indirect immunogold labelling. The particulate label has been quantified to assess the distribution of the target protein within term placental chorionic villi. The mesodermal compartment of the tissue was more heavily labelled than the ectodermally derived trophoblast. Basal plate lining endothelium and villous endothelium had similar immunoreactivity with anti-caveolin-1 antibody. A polarised distribution of the caveolin within chorionic villous capillary endothelial cells was observed. As evidenced by immuno-reactivity, the protein was statistically significantly more concentrated in the region associated with the basal membrane than the apical membrane. The latter region contained in turn significantly more anti-caveolin-1 immunoreactivity than the central region. These differences are discussed in the light of possible transport and signalling platform r?les for villous and basal plate endothelium.     

Monoclonal antibodies reactive with myelin basic protein

New monoclonal antibodies (MAbs) to myelin basic protein (BP) reveal epitopes to be in sequences 22–34, 75–82, 83–96, 118–131 and 125–131. Comparison of these results with those previously reported suggest that almost every sequence of about 10 amino acid residues may be sufficiently antigenic to make a single MAb but that certain regions are immunodominant, strong enough to make practically the same MAb repeatedly. One of these new MAbs (clone 3) has especially interesting reactivity, sharply limited to residues 75–82 in bovine and porcine BP: Lys-Ala-Gln-His-Gly-Arg-Pro. Whales presumably have the same sequence, since their BPs are fully reactive with clone 3 MAb, but all other species of BP, with known sequences of BP, have at least two changes in this sequence. Deletion of Lys⁷⁵ (as in a tryptic peptide of porcine BP) reduces reactivity with the MAb about 10-fold, whereas substitution of Ala⁷⁶ by Ser (as in all other species of BP) and either deletion of Gln⁷⁷ (as in human, monkey and rabbit BP) or His⁷⁸ (as in the guinea pig and rat BP) or substitution of Pro⁸² by Thr (as in human, monkey, rat and mouse BP) eliminates reactivity. We speculate that woodchuck and prairie dog BPs in this region closely resemble chicken BP, which has about 2% of the original reactivity. However, squirrel BP is unique, probably having only one of the changes in this region of BP, since it possesses 10–20 times the reactivity of chicken BP but still only 20–50% of the original reactivity with clone 3 MAb, a degree of reactivity not seen with any other species of BP.     

Combined nasal administration of encephalitogenic myelin basic protein peptide 68-86 and IL-10 suppressed incipient experimental allergic encephalomyelitis in Lewis rats

Mucosal administration of low doses of myelin basic protein (MBP) peptide 68-86 (MBP 68-86) or anti-inflammatory cytokine IL-10 effectively prevented experimental allergic encephalomyelitis (EAE), but failed to suppress the disease if given after 7 days postimmunization (p.i.), i.e., after T cell priming had occurred. We anticipated that combined administration of autoantigen and IL-10 can treat incipient EAE. Lewis rats with EAE actively induced with MBP 68-86 and complete Freund's adjuvant received 120 microg MBP 68-86 + 200 ng IL-10 per rat per day from day 7 p.i. and for 5 consecutive days. These rats showed later onset, lower clinical scores, less body weight loss, and shorter duration of EAE than rats receiving MBP 68-86 or IL-10 only or PBS. EAE amelioration was associated with decreased infiltration of ED1(+) macrophages and CD4(+) T cells within the central nervous system and with decreased proliferative responses of lymph node cells, indicating that combined administration of MBP 68-86 and IL-10 induced immune hyporesponsiveness. IFN-gamma secretion as well as IFN-gamma, TNF-alpha, IL-4, and IL-10 mRNA expression by lymph node MNC was down-regulated in the treated rats. Immune hyporesponsiveness, rather than immune deviation or regulatory mechanisms, seems to be responsible for the protection of EAE after autoantigen + IL-10 administration by the nasal route.     

Phosphorylation of myelin basic protein by vaccinia virus

Vaccinia virus phosphorylates myelin basic protein in the myelin membrane in vitro. In the presence of vaccinia virus cores maximally 1.5 mol and in the presence of intact virus 0.7 mol phosphate residues were incorporated into 1 mol of myelin basic protein in the myelin membrane. The peptides of myelin basic protein which were phosphorylated by the vaccinia virus kinase were clearly all different from the peptides which were phosphorylated by the endogenous myelin protein kinase.The viral modification of the encephalitogenic protein and its significance to immunological events is discussed.     

Granular cell tumors of the skin contain myelin basic protein

Myelin basic protein, a substance found in neural structures, has been demonstrated in cutaneous granular cell tumors using a monoclonal antibody generated against myelin basic protein and an immunoperoxidase method. The substance was not found in fibrohistiocytic skin lesions. The presence of myelin basic protein in granular cell lesions of the skin supports the concept that this lesion is related closely to nerve structures.