Variation in NOD2 augments Th2- and Th17 responses to myelin basic protein in multiple sclerosis

Variations in the gene for the nucleotide-binding oligomerisation domain (NOD) 2 have been associated with Crohn's disease but not multiple sclerosis (MS). Here we investigate the effect of three polymorphisms in the NOD2 gene (rs5743277, rs2066842 and rs5743291) on cytokine production and CD4+ T cell proliferation elicited by human myelin basic protein (MBP) in blood mononuclear cell (MNC) cultures from 29 patients with MS. No polymorphism was observed at rs5743277. No associations with the rs2066842 polymorphism were found. Concerning rs5743291, none were homozygous for the minor allele. Seven of 29 (24%) patients were heterozygous, and five of these (71%) exhibited increased MBP-induced CD4+ T cell proliferation versus four of 22 (18%), who were homozygous for the major allele (p<0.04). Interleukin (IL)-5 was induced by MBP in MNC from the same five carriers versus two (9%) homozygotes (p<0.004); four carriers (57%) versus three non-carriers (14%) exhibited IL-17 responses to MBP (p<0.04). By contrast, we found no association between the polymorphisms investigated and interferon-gamma-, tumor necrosis factor-alpha-, IL-2, -4- or IL-10 responses to MBP. These results indicate that the rs5743291 polymorphism influences T helper (Th) cell 2- and Th17 cell responses in MNC from MS patients.

Myelin basic protein priming reduces the expression of Foxp3 in T cells via nitric oxide

Regulatory T cells (Tregs) play a vital role in autoimmune disorders. Among several markers, forkhead box p3 (Foxp3) is the most specific with regard to Treg activity. Therefore, understanding mechanisms that regulate Foxp3 expression is a critical step for unraveling the complicacy of autoimmune pathophysiology. The present study was undertaken to investigate the crosstalk between NO and Tregs. Interestingly, after myelin basic protein (MBP) priming, the expression of Foxp3 decreased in MBP-primed T cells. However, blocking NO either by inhibiting inducible NO synthase with l-N(6)-(1-iminoethyl)-lysine hydrochloride or through scavenging with PTIO or by pharmacological drugs, such as pravastatin, sodium benzoate, or gemfibrozil, restored the expression of Foxp3 in MBP-primed T cells. However, this restoration of Foxp3 by pharmacological drugs was reversed by S-nitrosoglutathione, an NO donor. Similarly, NO also decreased the populations of Tregs characterized by CD4(+)CD25(+) and CD25(+)FoxP3(+) phenotypes. We have further confirmed this inverse relationship between NO and Foxp3 by analyzing the mRNA expression of Foxp3 and characterizing CD25(+)FoxP3(+) or CD4(+)Foxp3(+) phenotypes from inducible NO synthase knockout mice. Moreover, this inverse relation between NO and Foxp3 also was observed during priming with myelin oligodendrocyte glycoprotein, another target neuroantigen in multiple sclerosis, as well as collagen, a target autoantigen in rheumatoid arthritis. Finally, we demonstrate that NO inhibited the expression of Foxp3 in MBP-primed T cells via soluble guanylyl cyclase-mediated production of cGMP. Taken together, our data imply a novel role of NO in suppressing Foxp3(+) Tregs via the soluble guanylyl cyclase pathway.

Inhibition of familial cerebral amyloid angiopathy mutant amyloid beta-protein fibril assembly by myelin basic protein

Deposition of fibrillar amyloid beta-protein (Abeta) in the brain is a prominent pathological feature of Alzheimer disease and related disorders, including familial forms of cerebral amyloid angiopathy (CAA). Mutant forms of Abeta, including Dutch- and Iowa-type Abeta, which are responsible for familial CAA, deposit primarily as fibrillar amyloid along the cerebral vasculature and are either absent or present only as diffuse non-fibrillar plaques in the brain parenchyma. Despite the lack of parenchymal fibril formation in vivo, these CAA mutant Abeta peptides exhibit a markedly increased rate and extent of fibril formation in vitro compared with wild-type Abeta. Based on these conflicting observations, we sought to determine whether brain parenchymal factors that selectively interact with and modulate CAA mutant Abeta fibril assembly exist. Using a combination of immunoaffinity chromatography and mass spectrometry, we identified myelin basic protein (MBP) as a prominent brain parenchymal factor that preferentially binds to CAA mutant Abeta compared with wild-type Abeta. Surface plasmon resonance measurements confirmed that MBP bound more tightly to Dutch/Iowa CAA double mutant Abeta than to wild-type Abeta. Using a combination of biochemical and ultrastructural techniques, we found that MBP inhibited the fibril assembly of CAA mutant Abeta. Together, these findings suggest a possible role for MBP in regulating parenchymal fibrillar Abeta deposition in familial CAA.

Cytokine-neuroantigen fusion proteins: new tools for modulation of myelin basic protein (MBP)-specific T cell responses in experimental autoimmune encephalomyelitis

Fusion proteins incorporating anti-inflammatory cytokines and immunodominant self antigen as separate domains of a single protein may hold promise for development of antigen-specific tolerogenic vaccines. Proteins incorporating rat sequences of IL-1RA, IL-2, IL-4, IL-10, or IL-13 were expressed as fusion proteins containing the major encephalitogenic region of myelin basic protein (MBP). These fusion proteins were expressed via baculovirus (bv) expression systems and were shown to have cytokine-dependent and antigen-specific biological activity. In the case of the IL-2 and IL-4 fusion proteins, covalent linkage of the cytokine and neuroantigen domains resulted in synergistic antigen presentation. These data indicate that the cytokine domain may be able to modulate APC activity and simultaneously target the covalently tethered NAg for enhanced presentation by certain APC subsets. Cytokine/antigen fusion proteins may represent a novel tool for antigen-specific immune modulation in autoimmune disease.

Multiple roles of Id4 in developmental myelination: predicted outcomes and unexpected findings

Myelination in the central nervous system is a complex process requiring the integration of oligodendrocyte progenitor differentiation and the coordinate expression of myelin genes. This study addresses the role of the helix-loop-helix protein Id4 in these two events. Overexpression of Id4 in oligodendrocyte progenitors prevents differentiation and consequently decreases the endogenous expression of all myelin genes. Conversely, progenitors lacking Id4 display precocious differentiation both in vitro and in vivo, and this phenotype is partially compensated by increased apoptosis. Besides this role, Id4 also has the ability to decrease the activity of specific myelin promoters, since Id4 overexpression decreases the activity of luciferase reporter genes driven by the ceramide galactosyltransferase (CGT) or myelin basic protein (MBP) promoter, but not by a myelin proteolipid protein (PLP) promoter. Consistent with these results, the expression levels of MBP and CGT are greater in neonatal Id4 null mice when compared with wild-type siblings and correlate with the early detection of MBP immunoreactive myelinated fibers. In contrast, the levels of other myelin proteins, such as PLP and myelin associated glycoprotein (MAG) are decreased in the Id4 null mice. MAG expression is localized to the soma rather than the fibers of immunoreactive cells in the neonatal brain and compensated at later developmental stages. These data support the role of Id4 as oligodendrocyte differentiation inhibitor with the ability to differentially regulate the expression and subcellular distribution of myelin gene products.

A Tale of Two Citrullines—Structural and Functional Aspects of Myelin Basic Protein Deimination in Health and Disease

Myelin basic protein (MBP) binds to negatively charged lipids on the cytosolic surface of oligodendrocyte membranes and is responsible for adhesion of these surfaces in the multilayered myelin sheath. The pattern of extensive post-translational modifications of MBP is dynamic during normal central nervous system (CNS) development and during myelin degeneration in multiple sclerosis (MS), affecting its interactions with the myelin membranes and with other molecules. In particular, the degree of deimination (or citrullination) of MBP is correlated with the severity of MS, and may represent a primary defect that precedes neurodegeneration due to autoimmune attack. That the degree of MBP deimination is also high in early CNS development indicates that this modification plays major physiological roles in myelin assembly. In this review, we describe the structural and functional consequences of MBP deimination in healthy and diseased myelin.

Les protéines cationiques de l'éosinophile : marqueurs d'activation du polynucléaire éosinophile

INTRODUCTION

Eosinophils play a central role in the pathogenesis of allergic diseases and host protection against parasites, especially against helminths.

EXEGESIS

Eosinophil granules contain cytotoxic proteins, including cationic proteins: major basic protein (MBP), eosinophil cationic protein (ECP), eosinophil peroxidase (EPO) and eosinophil derived neurotoxin (EDN).

CONCLUSION

Eosinophil granule proteins are implicated in the occurrence of allergic diseases and Churg-Strauss syndrome. These proteins are activation markers of eosinophils and may be useful in clinical practice.

The pathobiology of myelin mutants reveal novel biological functions of the MBP and PLP genes

Substantial biological data indicate that the myelin basic protein (MBP) and myelin proteolipid protein (PLP/DM20) genes produce products with functions beyond that of serving as myelin structural proteins. Much of this evidence comes from studies on naturally-occurring and man-made mutations of these genes in mice and other species. This review focuses upon recent evidence showing the existence of other products of these genes that may account for some of these other functions, and recent studies providing evidence for alternative biological functions of PLP/DM20. The MBP and PLP/DM20 genes each encode the classic MBP and PLP isoforms, as well as a second family of proteins that are not involved in myelin structure. The biological roles of these other products of the genes are becoming clarified. The non-classic MBP gene products appear to be components of transcriptional complexes in the nucleus, and they also may be involved in signaling pathways in T-cells and in neural cells. The non-classic PLP/DM20 gene products appear to be components of intracellular transport vesicles in oligodendrocytes. There is evidence for other functions of the classic PLP/DM20 proteins, including a role in neural cell death mechanisms, autocrine and paracrine regulation of oligodendrocytes and neurons, intracellular transport and oligodendrocyte migration.

Myelin basic protein-primed T cells of female but not male mice induce nitric-oxide synthase and proinflammatory cytokines in microglia: implications for gender bias in multiple sclerosis

Females are more susceptible than males to multiple sclerosis (MS). However, the underlying mechanism behind this gender difference is poorly understood. Because the presence of neuroantigen-primed T cells within the CNS is necessary for the development of MS, the present study was undertaken to investigate the activation of microglia by myelin basic protein (MBP)-primed T cells of male, female, and castrated male mice. Interestingly, MBP-primed T cells isolated from female and castrated male but not from male mice induced the expression of inducible nitric-oxide synthase (iNOS) and proinflammatory cytokines (interleukin-1beta (IL-1beta), IL-1alpha, IL-6, and tumor necrosis factor-alpha) in microglia by cell-cell contact. Again there was no apparent defect in male microglia, because MBP-primed T cells isolated from female and castrated male but not male mice were capable of inducing the production of NO in male primary microglia. Inhibition of female T cell contact-mediated microglial expression of proinflammatory molecules by dominant-negative mutants of p65 and C/EBPbeta suggest that female MBP-primed T cells induce microglial expression of proinflammatory molecules through the activation of NF-kappaB and C/EBPbeta. Interestingly, MBP-primed T cells of male, female, and castrated male mice were able to induce microglial activation of NF-kappaB. However, MBP-primed T cells of female and castrated male but not male mice induced microglial activation of C/EBPbeta. These studies suggest that microglial activation of C/EBPbeta but not NF-kappaB by T cell:microglial contact is a gender-specific event and that male MBP-primed T cells are not capable of inducing microglial expression of proinflammatory molecules due to their inability to induce the activation of C/EBPbeta in microglia. This novel gender-sensitive activation of microglia by neuroantigen-primed T cell contact could be one of the mechanisms behind the female-loving nature of MS.

T-cell properties determine disease site, clinical presentation, and cellular pathology of experimental autoimmune encephalomyelitis

Two distinct clinical phenotypes of experimental autoimmune encephalomyelitis are observed in BALB interferon-gamma knockout mice immunized with encephalitogenic peptides of myelin basic protein. Conventional disease, characterized by ascending weakness and paralysis, occurs with greater frequency after immunizing with a peptide comprising residues 59 to 76. Axial-rotatory disease, characterized by uncontrolled axial rotation, occurs with greater frequency in mice immunized with a peptide corresponding to exon 2 of the full length 21.5-kd protein. The two clinical phenotypes are histologically distinguishable. Conventional disease is characterized by inflammation and demyelination primarily in spinal cord, whereas axial-rotatory disease involves inflammation and demyelination of lateral medullary areas of brain. Both types have infiltrates in which neutrophils are a predominating component. By isolating T cells and transferring disease to naive recipients, we show here that the type of disease is determined entirely by the inducing T cell. Furthermore, studies using CXCR2 knockout recipients, unable to recruit neutrophils to inflammatory sites, show that although neutrophils are critical for some of these T cells to effect disease, there are also interferon-gamma-deficient T cells that induce disease in the absence of both interferon-gamma and neutrophils. These results highlight the multiplicity of T-cell-initiated effector pathways available for inflammation and demyelination.

The MBP-reactive repertoire is shaped by recognition of minor histocompatibility antigens

While it is known that the degeneracy of T-cell antigen recognition is involved in many aspects of T cell-immunology, its importance in the selection of the T cell repertoire remains an aspect to be better investigated. Here we examined if an intrathymic degenerate T cell recognition mechanism shapes the myelin basic protein (MBP)-reactive repertoire inducing resistance to experimental autoimmune encephalomyelitis (EAE) in some MHC and/or minor histocompatibility antigens (MiHAs) heterozygous F1 mice bearing the H-2(s) susceptibility allele. We found a considerable degree of cross-reactivity between MBP and MiHAs encoded in various EAE resistant mouse strains: (1) MBP-specific T cells can be re-stimulated in vitro by cells expressing these MiHAs and maintain their encephalitogenic activity, and (2) lymphoid cells from parental strains that generate EAE resistant F1 hybrids can induce disease relapse when injected into EAE-susceptible hosts. The results suggest that heterozygosity, through the degeneracy of T cell antigen recognition mechanism, may provide further means to constrain the potential autoreactive repertoire.

Characterization of the protein kinase activity of TRPM7/ChaK1, a protein kinase fused to the transient receptor potential ion channel

Channel-kinase TRPM7/ChaK1 is a member of a recently discovered family of protein kinases called alpha-kinases that display no sequence homology to conventional protein kinases. It is an unusual bifunctional protein that contains an alpha-kinase domain fused to an ion channel. The TRPM7/ChaK1 channel has been characterized using electrophysiological techniques, and recent evidence suggests that it may play a key role in the regulation of magnesium homeostasis. However, little is known about its protein kinase activity. To characterize the kinase activity of TRPM7/ChaK1, we expressed the kinase catalytic domain in bacteria. ChaK1-cat is able to undergo autophosphorylation and to phosphorylate myelin basic protein and histone H3 on serine and threonine residues. The kinase is specific for ATP and cannot use GTP as a substrate. ChaK1-cat is insensitive to staurosporine (up to 0.1 mM) but can be inhibited by rottlerin. Because the kinase domain is physically linked to an ion channel, we investigated the effect of ions on ChaK1-cat activity. The kinase requires Mg(2+) (optimum at 4-10 mM) or Mn(2+) (optimum at 3-5 mM), with activity in the presence of Mn(2+) being 2 orders of magnitude higher than in the presence of Mg(2+). Zn(2+) and Co(2+) inhibited ChaK1-cat kinase activity. Ca(2+) at concentrations up to 1 mM did not affect kinase activity. Considering intracellular ion concentrations, our results suggest that, among divalent metal ions, only Mg(2+) can directly modulate TRPM7/ChaK1 kinase activity in vivo.

Role of very-late antigen-4 (VLA-4) in myelin basic protein-primed T cell contact-induced expression of proinflammatory cytokines in microglial cells

The presence of neuroantigen-primed T cells recognizing self-myelin antigens within the CNS is necessary for the development of demyelinating autoimmune disease like multiple sclerosis. This study was undertaken to investigate the role of myelin basic protein (MBP)-primed T cells in the expression of proinflammatory cytokines in microglial cells. MBP-primed T cells alone induced specifically the microglial expression of interleukin (IL)-1beta, IL-1alpha tumor necrosis factor alpha, and IL-6, proinflammatory cytokines that are primarily involved in the pathogenesis of MS. This induction was primarily dependent on the contact between MBP-primed T cells and microglia. The activation of microglial NF-kappaB and CCAAT/enhancer-binding protein beta (C/EBPbeta) by MBP-primed T cell contact and inhibition of contact-mediated microglial expression of proinflammatory cytokines by dominant-negative mutants of p65 and C/EBPbeta suggest that MBP-primed T cells induce microglial expression of cytokines through the activation of NF-kappaB and C/EBPbeta. In addition, we show that MBP-primed T cells express very late antigen-4 (VLA-4), and functional blocking antibodies to alpha4 chain of VLA-4 (CD49d) inhibited the ability of MBP-primed T cells to induce microglial proinflammatory cytokines. Interestingly, the blocking of VLA-4 impaired the ability of MBP-primed T cells to induce microglial activation of only C/EBPbeta but not that of NF-kappaB. This study illustrates a novel role of VLA-4 in regulating neuroantigen-primed T cell-induced activation of microglia through C/EBPbeta

Role for IL-10 in suppression mediated by peptide-induced regulatory T cells in vivo

Regulatory CD4(+) T cells were induced in the Tg4 TCR transgenic mouse specific for the N-terminal peptide (Ac1-9) of myelin basic protein by intranasal administration of a high-affinity MHC-binding analog (Ac1-9[4Y]). Peptide-induced tolerant cells (PItol) were anergic, failed to produce IL-2, but responded to Ag by secretion of IL-10. PItol cells were predominantly CD25(-) and CTLA-4(+) and their anergic state was reversed by addition of IL-2 in vitro. PItol cells suppressed the response of naive Tg4 cells both in vitro and in vivo. The in vitro suppression mediated by these cells was not reversed by cytokine neutralization and was cell-cell contact-dependent. However, suppression of proliferation and IL-2 production by PItol cells in vivo was abrogated by neutralization of IL-10. These results emphasize an important role for IL-10 in the function of peptide-induced regulatory T cells in vivo and highlight the caution required in extrapolating mechanisms of T regulatory cell function from in vitro studies.

Local delivery of granulocyte macrophage colony-stimulating factor by retrovirally transduced antigen-specific T cells leads to severe, chronic experimental autoimmune encephalomyelitis in mice

Experimental autoimmune encephalomyelitis (EAE) is an inflammatory disease of the central nervous system (CNS) that can be induced in susceptible mice by the transfer of autoreactive T cells that recognize myelin basic protein (MBP). The onset and subsequent recovery from disease are associated with distinct patterns of cytokine and chemokine expression within the inflammatory lesions of the CNS. Given the likely importance of the local cytokine milieu in regulating the disease process, it would be preferable to administer cytokines locally to the CNS and reduce systemic delivery in order to evaluate their immunoregulatory roles in EAE. For this purpose, we have used retrovirally transduced T cells from MBP-specific T cell receptor transgenic mice in an attempt to target cytokine delivery to the CNS where MBP is primarily expressed. We have found that T cells expressing granulocyte macrophage colony-stimulating factor (GM-CSF) induce severe, chronic EAE from which mice fail to recover. Our results indicate that increased local GM-CSF expression could play an important role in inducing chronic EAE.

Two separate domains in the golli myelin basic proteins are responsible for nuclear targeting and process extension in transfected cells

The golli products of the myelin basic protein (MBP) gene are expressed in neurons and oligodendrocytes (OLs). In certain neuronal populations, golli proteins undergo translocation between the nucleus and cytoplasm/processes during development. The proteins consist of two domains, a golli domain of 133 amino acids and an MBP domain of variable length. One objective of this study was to identify the sequences responsible for nuclear targeting. Site-directed mutagenesis and deletion analyses were used to generate a series of golli-green fluorescent protein (GFP) DNA constructs that were transfected into OL and neuronal cell lines to follow localization by confocal microscopy. The results indicated that a 36-residue stretch in the MBP domain is essential for nuclear targeting, and the sequence appears to be a nontraditional localization signal motif. The studies also revealed that overexpression of golli proteins could induce dramatic changes in cell morphology. In OL lines, overexpression of intact golli proteins, or golli peptide alone, caused an increase in the length and number of processes, and the elaboration of membrane sheets. In the neuronal lines, there was a dramatic increase in number and length of extensions. The results, consistent with the timing of golli expression in cells during neural development, suggest that golli proteins may be involved in process formation/extension in OLs and neurons during development. These studies have defined two functional domains in the golli protein. Sequences in the MBP domain target the protein into the nucleus and sequences within the golli domain induce process sheet extension in OLs and neurons.

Activation of Vbeta8 T cells affects spontaneous EAE in MBP TCR transgenic mice

Two strains of transgenic (Tg) mice (Valpha2.3/Vbeta8.2 and Valpha4/Vbeta8.2) have T cell receptors (TCR) that recognize the NAc1-11 immunodominant epitope of the myelin basic protein (MBP). Spontaneous experimental autoimmune encephalomyelitis (sEAE) readily develops in Valpha2.3/Vbeta8.2 mice. T cells in Valpha2.3/Vbeta8.2 mice demonstrate increased levels of CD69, CD44(high) and decreased CD45RB relative to Valpha4/Vbeta8.2 mice. Increased proliferative responses to MBP and high levels of TNF-alpha are seen in Valpha2.3/Vbeta8.2 mice. High IL-4 and TGF-beta production is observed in Valpha4/Vbeta8.2 mice. CC chemokines (macrophage inflammatory protein-1 alpha (MIP-1alpha), RANTES and monocyte chemotactic protein 1 (MCP-1)) are increased in the central nervous system (CNS) of Valpha2.3/Vbeta8.2 mice. Thus, activated Th1 cells in the periphery of Valpha2.3/Vbeta8.2 mice may traffic to the CNS in response to CC chemokines, influencing sEAE.

Pre-emptive targeting of the epitope spreading cascade with genetically modified regulatory T cells during autoimmune demyelinating disease

Epitope spreading or endogenous self-priming has been implicated in mediating the progression of autoimmune disease. In the present study we created an immune-deviated, epitope spreading response in SWXJ mice after the onset of experimental autoimmune encephalomyelitis, a prototypic autoimmune animal model widely used in multiple sclerosis research. We established an immunoregulatory spreading repertoire by transferring T cells genetically modified to produce high levels of IL-10 in response to a dominant epitope spreading determinant. Installation of a Th2/Tr1-like spreading repertoire resulted in a marked and prolonged inhibition of disease progression and demyelination characterized by 1) bystander inhibition of the recall response to the priming immunogen, and 2) a Th1-->Tr1 immune-deviated spreading response involving a shift in the source of IL-10 production from the transferred regulatory population to the host-derived, endogenously primed repertoire. Thus, our data provide a rationale for cell-based therapeutic intervention in multiple sclerosis by showing that pre-emptive targeting of the epitope spreading cascade with regulatory T cells effectively induces an immune-deviated spreading response capable of inhibiting ongoing inflammatory autoreactivity and disease progression.

[Myelin basic protein. Structure, properties, function and role in diagnosing demyelinating diseases]

Physico-chemical properties and biological role of myelin basic protein (MBP)--one of the main myelin membrane proteins are reviewed. The data on MBP phosphorylation, methylation, fatty acid acylation and on interaction with lipid molecules in the human and animals bodies are presented. Much attention has been paid to the discussion of the diagnostic and clinical significance of the MBP, as the marker of demyelinating process in the central and peripheral nervous system.

New insights on the biology of myelin basic protein gene: the neural-immune connection

In the past 6 years, our conception of the major myelin protein genes has begun to change significantly because of recent findings documenting the existence of new exons encoding other products of these genes. A decade ago the myelin basic protein (MBP) and proteolipid protein (PLP) genes were thought to be expressed solely in myelin-forming cells, and their products were thought to be structural components of myelin. Since then, abundant evidence has been gathered identifying the presence of products of these genes in nonmyelinating cell types including both the immune and the nervous systems. Furthermore, within the nervous system, products of these genes have been identified in neurons and embryonic cells, clearly indicating that these myelin protein genes have additional functions in a number of cell types that are unrelated to myelination. In this brief communication, we review the recent literature that has resulted in this revision of our understanding of the MBP gene structure, products and expression.

Pathologic role and temporal appearance of newly emerging autoepitopes in relapsing experimental autoimmune encephalomyelitis

Relapsing experimental autoimmune encephalomyelitis (R-EAE) is a CD4+ T cell-mediated demyelinating disease model for multiple sclerosis. Myelin destruction during the initial relapsing phase of R-EAE in SJL mice initiated by immunization with the proteolipid protein (PLP) epitope PLP139-151 is associated with activation of T cells specific for the endogenous, non-cross-reactive PLP178-191 epitope (intramolecular epitope spreading), while relapses in R-EAE induced with the myelin basic protein (MBP) epitope MBP84-104 are associated with PLP139-151-specific responses (intermolecular epitope spreading). Here, we demonstrate that T cells specific for endogenous myelin epitopes play the major pathologic role in mediating clinical relapses. T cells specific for relapse-associated epitopes can serially transfer disease to naive recipients and are demonstrable in the CNS of mice with chronic R-EAE. More importantly, induction of myelin-specific tolerance to relapse-associated epitopes, by i.v. injection of ethylene carbodiimide-fixed peptide-pulsed APCs, either before disease initiation or during remission from acute disease effectively blocks the expression of the initial disease relapse. Further, blockade of B7-1-mediated costimulation with anti-B7-1 F(ab) during disease remission from acute PLP139-151-induced disease prevents clinical relapses by inhibiting activation of PLP178-191-specific T cells. The protective effects of anti-B7-1 F(ab) treatment are long-lasting and highly effective even when administered following the initial relapsing episode wherein spreading to a MBP epitope (MBP84-104) is inhibited. Collectively, these data indicate that epitope spreading is B7-1 dependent, plays a major pathologic role in disease progression, and follows a hierarchical order associated with the relative encephalitogenic dominance of the myelin epitopes (PLP139-151 > PLP178-191 > MBP84-104).

Usage of Vbeta3.3 T-cell receptor by myelin basic protein-specific encephalitogenic T-cell lines in the Lewis rat

T-cell receptor (TCR) beta-chain usage in experimental autoimmune encephalomyelitis (EAE) seems to be much more heterogeneous than previously assumed even for a single autoantigen in an inbred animal strain. Owing to the lack of suitable antibodies, this has been demonstrated only at the RNA level so far. To characterize further the TCR elements used in the Lewis rat for the recognition of the main encephalitogenic region of myelin basic protein (MBP), BALB/c mice were immunized with T-cell hybridomas expressing non-Vbeta8.2 TCR specific for guinea pig MBP peptide aa 68-88. Two B-cell hybridomas (clones C-A11 and F-D6) producing TCR Vbeta3.3-specific monoclonal antibodies were selected. Specificity was demonstrated by RT-PCR and cloning of PCR products obtained from sorted T-cell lines and naive T cells. MBP-specific Vbeta3.3 T cells used the L-S motif in the VDJ region, were associated with Valpha2 or Valpha8 chains, and specifically recognized MBP peptide aa 68-88. Vbeta3.3 TCR-positive T cells were detected in all of a panel of six MBP-specific T-cell lines, although to a lesser degree than Vbeta8.2 TCR-positive T cells. After intravenous injection of sorted Vbeta3.3 T cells, animals developed EAE, and Vbeta3.3-positive cells were found by immunocytochemical analyses in the spinal cord. Furthermore, treatment of EAE induced by immunization with MBP was more effective when a combination of anti-Vbeta3.3 and anti-Vbeta8.2 mAbs was used. These results confirm the functional role of TCR Vbeta3.3 and thus underscore the heterogeneity of TCR usage in MBP-associated autoimmunity.