Evidence for multiple human T cell recognition sites on myelin basic protein

Expression of Golli mRNA during development in primary immune lymphoid organs of the rat

The gene-of-the-oligodendrocyte lineage (Golli)-MBP transcription unit contains three Golli-specific exons together with eight exons of the "classical" myelin basic protein (MBP) gene, yielding alternatively spliced proteins which share amino acid sequence with MBP. Unlike MBP, a late antigen expressed only in the nervous system, Golli gene products are expressed pre- and post-natally at many sites. In this study, we determined the sequence of Golli in rat by RT-PCR and 5' RACE and showed that Golli sequences are expressed in primary lymphoid organs as early as e16.5, which could explain the anergic rat T cell response we previously observed in Golli-induced meningitis.

Lessons from studies of antigen-specific T cell responses in Multiple Sclerosis

Multiple Sclerosis (MS) is considered a T cell-mediated autoimmune disease of central nervous system myelin. Based on elegant experiments in an animal model of MS, experimental allergic encephalomyelitis (EAE), a number of myelin proteins and peptides derived from these can induce inflammatory demyelinating lesions. Recent studies with transgenic mice expressing human HLA-DR molecules and a myelin basic protein (MBP)-specific T cell receptor as well as data from a phase II clinical trial with an altered peptide ligand based on MBP peptide (83-99) provide convincing evidence that the pathogenetic concepts which largely stem from the above EAE studies are valid in MS, too.

The neuroimmunology of multiple sclerosis: possible roles of T and B lymphocytes in immunopathogenesis

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system white matter. The association of the disease with MHC genes, the inflammatory white matter infiltrates, similarities with animal models, and the observation that MS can be treated with immunomodulatory and immunosuppressive therapies support the hypothesis that autoimmunity plays a major role in the disease pathology. Evidence supports activated CD4+ myelin-reactive T cells as major mediators of the disease. In addition, a renewed interest in the possible contribution of B cells to MS immunopathology has been sparked by nonhuman primate and MS pathological studies. This review focuses on the immunopathology of MS, outlining the hypothetical steps of tolerance breakdown and the molecules that play a role in the migration of autoreactive cells to the CNS. Particular focus is given to autoreactive T cells and cytokines as well as B cells and autoantibodies and their role in CNS pathogenesis in MS.

Preferential expansion of autoreactive T lymphocytes from the memory T-cell pool by IL-7

We have developed a new technique that allows us to quantify antigen-specific T cells, and to determine their functional phenotype and origin from naive versus memory populations. Using this methodology, we have characterized a total of 286 T-cell lines specific for myelin basic protein (MBP) and influenza hemagglutinin from 16 multiple sclerosis (MS) patients and nine healthy donors. Our data support the notion that MBP-specific T cells undergo in vivo activation in MS patients and indicate a presence of immune dysregulation that renders MS patients prone to develop autoimmunity. Our methodology offers a way to study antigen-specific T-cell characteristics as a surrogate marker in immunotherapy trials.

Autoreactive IgG to intracellular proteins in sera of MS patients

IgG binding to multiple protein constituents in lysates of Jurkat cells was detected by Western blot in sera of patients with multiple sclerosis (MS) and systemic lupus erythematosus (SLE). The distribution patterns of bands with sera tested against protein lysates from normal Jurkat cells or from Jurkat cells exposed to apoptosis or oxidative stress inducing conditions were similar in most patients, but with inter-individual differences. The number of bands with sera of both patient populations far exceeded those (0 or 2 bands) detected with sera of healthy controls. Proteinase K, RNase and DNase pre-treatment of cell lysates suggested a protein nature for all of the antigens and a ribonucleoprotein (RNP) nature for some of the antigens recognized by serum IgG of MS and SLE patients. Only two MS patients had positive anti-nuclear antibody (ANA) titers, while all of them had positive Western blots. In addition to similarities, dissimilarities were also recognized between the humoral immune responses in MS and SLE. No IgG molecules were detected against phosphorylated proteins in the sera of MS patients, while multiple phosphoproteins were recognized by IgG molecules of SLE patients in immunoprecipitation experiments. These data suggest that in addition to ANA, the sera of MS patients contain autoantibodies directed against multiple intracellular proteins. The protein recognition patterns of immunoglobulins in MS share similarities, but also have distinct features when compared to those in SLE. The biological significance of these autoantibodies in MS remains to be understood.

T cell recognition of myelin proteolipid protein and myelin proteolipid protein peptides in the peripheral blood of multiple sclerosis and control subjects

Myelin proteolipid protein (PLP) is a prime candidate autoantigen for multiple sclerosis. In order to define potential immunodominant epitopes, T cell lines (TCL) from the peripheral blood of HLA-DR 15(2) MS patients were established which responded to the intact molecule of PLP. These TCL were then tested in individual proliferation assays with a variety of PLP peptides spanning most of the PLP molecule. Multiple peptides were recognized by TCL from the MS population, with more than one peptide often recognized by lines from the same individual. Three immunodominant peptides were identified which were recognized by the majority of MS patients. Estimated frequency analyses were then performed on the peripheral blood of HLA-DR15(2)-positive MS and control subjects using TCL initiated by the three immunodominant peptides, 40-60, 95-117, and 185-206. TCL from HLA-DR15 MS subjects recognized peptide 95-117 significantly more often than TCL from control subjects.

HLA-DP: a class II restriction molecule involved in epitope spreading during the development of multiple sclerosis

Multiple sclerosis (MS) is an autoimmune demyelinating disease of the central nervous system. It is widely believed that complex polygenic inheritance patterns involving HLA-DR and -DQ class II genes contribute to MS susceptibility, and current evidence indicates that disease risk vs disease outcome may be associated with distinctly different HLA class II alleles. We have recently shown that the early development of MS is accompanied by an extensive plasticity of myelin self-recognition with the acquisition of neo-autoreactivity, or epitope spreading, as a prominent feature. Although we did not observe a common determinant recognized by patients sharing identical HLA-DR or -DQ class II alleles, we did observe epitope spreading to the p50-63 determinant of myelin proteolipid protein (PLP) in two study subjects showing complete disparity at HLA-DR and -DQ but identity at the HLA-DP allele DPB1*0301. In the present study we show that self-recognition during the early stages in the development of MS involves HLA-DP class II restricted responses to the PLP 50-63 spreading determinant. Our results suggest that self-presentation by HLA-DP may play an important role in epitope spreading and in the propagation of self-recognition during the clinical progression of MS.

Identification of multiple sclerosis-associated genes

Multiple sclerosis (MS) is a complex genetic trait. Analyses to identify genetic variants that increase susceptibility to MS have primarily focused on candidate genes, either in family linkage investigations or in association (linkage disequilibrium) studies in sporadic cases and control subjects. Most of the candidate genes considered to date either influence immune function or encode structural myelin proteins. Recently, three preliminary whole genomic surveys were completed, and they reveal multiple loci of possible genetic linkage that are worthy of further study. No convincing evidence for a single strong locus has emerged from analysis of the three studies. Linkage promises to focus the future choice of candidate genes for further investigation.

Immunodominance of a low-affinity major histocompatibility complex-binding myelin basic protein epitope (residues 111-129) in HLA-DR4 (B1*0401) subjects is associated with a restricted T cell receptor repertoire

The pathogenesis of multiple sclerosis (MS) is currently ascribed in part to a T cell-mediated process targeting myelin components. The T cell response to one candidate autoantigen, myelin basic protein (MBP), in the context of HLA-DR15Dw2, has been previously studied in detail. However, the characteristics of cellular immunity in the context of other MS-associated HLA-DR haplotypes are scarcely known. MBP-specific T cell lines (TCL) were generated from HLA-DR4 (B1*0401)-positive MS subjects. Out of 275 MBP-specific TCL, 178 (64. 7%) specifically recognized region MBP(111-129), predominantly in the context of DRB1*0401. The major T cell epitope for MBP recognition corresponded to residues MBP(116-123). These TCL expressed disparate profiles of cytokine secretion and cytotoxicity. T cell receptor analysis, on the other hand, revealed a strikingly limited heterogeneity of rearrangements. In contrast to MBP(81-99), which binds with high affinity to HLA-DR15 and is recognized by a diverse T cell repertoire, MBP(111-129) binds weakly to DRB1*0401, suggesting that only high affinity T cell receptors might be able to efficiently engage such unstable MHC/peptide complexes, thus accounting for the T cell receptor restriction we observed. This study provides new insight about MBP recognition and proposes an alternative mechanism for immunodominance of self-antigen T cell epitopes in humans.

HPRT mutant T-cell lines from multiple sclerosis patients recognize myelin proteolipid protein peptides

Mutation of the hypoxanthine-guanine phosphoribosyl transferase (HPRT) gene in a T-cell is believed to be an indication that the T-cell has been activated and has proliferated in vivo. HPRT mutant T-cell lines were generated from peripheral blood mononuclear cells from patients with MS and control subjects. More lines were isolated from the MS patients than from the control subjects. Using stringent criteria for recognition, none of the lines from MS-affected or control subjects recognized intact myelin basic protein (MBP) or myelin proteolipid protein (PLP) molecules. Using stringent criteria, two of the 10 MS patients harbored mutant lines each recognizing distinct PLP peptides (PLP peptide 40-60 recognized by 3 lines from one patient and PLP peptide 178-191 recognized by 2 lines from the other patient). A single line recognizing PLP peptide 89-106 was derived from 1 of 7 normal controls. HPRT mutant lines recognizing multiple epitopes of PLP which spanned much of the molecule could be isolated from MS patients, and to a lesser extent, normal subjects.

Diversity and plasticity of self recognition during the development of multiple sclerosis

Recent studies using murine animal model systems indicate that clinical progression of autoimmune disease may be due to the sequential accumulation of neoautoreactivity characterized by extensive plasticity of self recognition. In the present study, we addressed the question of whether a similar paradigm of self recognition is implicated in the development of multiple sclerosis (MS), a demyelinating disease with a presumed autoimmune etiology. Our approach was to determine serial changes over a 12-18-mo period in response to an epitope-mapping series of 265 12-mer peptides of myelin proteolipid protein (PLP) by patients with isolated monosymptomatic demyelinating syndromes (IMDS), a group of distinct clinical disorders with variable rates of progression to MS. Our data showed that an extensive array of proteolipid protein peptides could elicit autoreactivity. Moreover, differential autoreactive patterns were evident within IMDS patient subpopulations. Monocentric monophasic IMDS patients with no evidence of prior subclinical disease typically showed fully sustained autoreactivity characterized by extensive plasticity, epitope focusing, shifting, and spreading of responses to new self determinants. In contrast, multicentric monophasic IMDS patients with putative evidence of prior asymptomatic lesion formation typically showed partially sustained autoreactivity characterized by abrupt abrogation of responses to an extensive array of self determinants. No sustained autoreactivity was observed in normal control subjects or in patients with other neurologic diseases. Our results indicate that self recognition associated with the development of MS is a developmental process characterized by autoreactive diversity, plasticity, and instability.

T cell receptor peptides in treatment of autoimmune disease: rationale and potential

The natural tendency in T cell-mediated autoimmune conditions to develop focused antigen-specific responses that over-utilize certain T cell receptor (TCR) V region segments prompts the induction of anti-TCR-specific T cells and antibodies that can inhibit the pathogenic T cells and promote recovery from disease. This natural regulatory network can be manipulated by injecting synthetic peptide vaccines that correspond to segments of the over-expressed V genes. In experimental autoimmune encephalomyelitis (EAE), an animal model for the human disease multiple sclerosis (MS), the pathogenic T cells are directed at myelin components, including basic protein (MBP). In some strains such as the Lewis rat and the PL/J mouse, the encephalitogenic BP-specific T cells overexpress a particular V region gene (V beta 8.2) in the TCR. In vivo administration of V beta 8.2 peptides in rats or mice can prevent and treat EAE by boosting regulatory anti-V beta 8.2-specific T cells that inhibit but do not delete the encephalitogenic specificities. This regulation is mediated by soluble factors, suggesting that the presence of regulatory TCR-specific T cells within the target organ (the central nervous system) may inhibit not only the stimulating V beta 8.2 + T cells, but also bystander T cells bearing different V genes. Parallel studies in MS patients have revealed striking V gene biases among BP-specific T cell clones from some patients that provided a rationale for TCR peptide therapy. Injection of V beta 5.2 and V beta 6.1 peptides boosted the frequency of TCR peptide-specific T cells and reduced responses to BP, in some cases with clinical benefit, indicating the presence of an anti-TCR regulatory network in humans that may also be manipulated with TCR peptide therapy.

Purification of immunologically active recombinant 21.5 kDa isoform of human myelin basic protein

We have designed and expressed in bacteria a recombinant fetal form of human myelin basic protein (21.5 kDa isoform; rhMBP21.5), a candidate autoantigen in multiple sclerosis. An exon 2 insertion, carboxy-terminal histidine tag and preferred bacterial codons differentiate the MBP21.5 gene from that encoding the adult, brain-derived form of human MBP (18.5 kDa isoform; hMBP18.5). MBPs were expressed at high levels in E. coli and extracted from whole cells by simultaneous acid solubilization and mechanical disruption. A nearly two-fold increase in recombinant protein was detected in strains harboring MBP genes with bacterial preferred codons compared to genes containing human codons. The recombinant molecules were purified in two steps, first by reversed-phase chromatographic separation and then by metal affinity chromatography. Dimeric forms of recombinant MBP21.5 were detected under physiological conditions, however, substitution of a serine for the single cysteine at amino acid residue 81 resulted in only monomer formation. All forms of recombinant MBPs induced proliferative responses of human T lymphocytes specific for epitopes in MBP18.5 kDa. In contrast, human T cell lines that recognize an exon 2-encoded epitope of MBP responded to the 21.5 kDa isoform of MBP, but not the 18.5 kDa isoform.

Differences in peptide binding of DR11 and DR13 microvariants demonstrate the power of minor variation in generating DR functional diversity

The influence of subtle HLA diversification on antigen binding was explored using murine L-cell transfectants expressing alleles in the DR11/DR13 family and a panel of peptides. The levels of binding among this family of DR microvariants were as diverse as the levels of binding among distantly related DR molecules. Even a single amino acid difference between allelic products had a profound effect on peptide binding. Specific amino acid substitutions, generated using site-directed mutagenesis to alter polymorphic residues at DR beta 32, 37, 57, 58, 67, 71, 86, demonstrated that a specific change within the context of a single DR molecule differed in its effect on the binding of specific peptides. In addition, a specific amino acid substitution had a differential effect on the binding level of a peptide to different DR molecules. Each polymorphic amino acid appeared to play a role in the binding of some peptide. Studies using the amino-terminal portion of the invariant chain CLIP peptide suggested that this peptide may offer varying degrees of competition in the binding of the cellular peptide pool in cells expressing different DR molecules. Finally, the results obtained with two strain-specific peptides from an immunodominant region of a malarial parasite show differential binding to two DR13 molecules, suggesting that immune pressure may promote parasite diversity. A dynamic interaction may exist between pathogens and the immune system shaping the HLA profile in a population. Thus even subtle diversification of the HLA molecules, possibly pathogen driven, can have a substantial effect on peptide binding and immune recognition.

Multiple sclerosis: immune mechanism and update on current therapies

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS) afflicting approximately 250,000 individuals in the United States. This inflammatory disease has variable clinical manifestations, ranging from a relapsing-remitting course to a chronic progressive disease. Approximately one third of MS patients have chronic progressive disease often leading to severe impairment of mobility, paralysis, poor vision, and disturbances of bladder and bowel function. Although the etiology and pathogenesis remain unknown, accumulating evidence supports the hypothesis that exposure to an as-yet-unidentified infectious agent(s) triggers an aberrant immune response against self nervous tissue in genetically susceptible individuals. The tenfold higher concordance rate for MS in monozygotic twins compared to dizygotic twins, the increased incidence of MS in women compared to men (2:1), and the familial and racial occurrence of MS provide strong evidence that genetic factors influence susceptibility to MS. The major predisposing genes in MS are the human leukocyte antigen (HLA) class II molecules, DR15 and DQw6, molecularly defined as HLA-DRB1, 1501-DQA1 0102-DQB1 0602. In certain ethnic groups, MS susceptibility is more strongly associated with other DR molecules. Environmental factors are also believed to play a role, as suggested by the unique worldwide prevalence, migration effects, and epidemiological studies. Increased serum and cerebrospinal fluid antibody titers to numerous viruses have been reported; however, there have been no confirmed studies detecting viral RNA or antigen in MS brain tissue. At the present time, no known treatment can significantly alter the progression of MS. Based on the postulate that MS is an autoimmune disease associated with abnormalities in immunoregulation, a number of different immunosuppressive and immunomodulating agents have been tested as therapeutic modalities. In this article, we review the circumstantial evidence suggesting that immune system abnormalities are associated with the disease process, and provide an update on current therapies used in MS.

Reactivity of normal T-cell lines to MBP isolated from normal and multiple sclerosis white matter

T-cell reactivity to human myelin basic protein (MBP) has been extensively studied using T-cell lines and clones generated from both peripheral blood and cerebrospinal fluid, from normal controls and multiple sclerosis (MS) patients. These studies have largely utilized myelin basic protein isolated from control human adult white matter. In our study, we used MBP reactive T-cell lines as a probe to investigate antigenic differences in a series of MBP preparations isolated from either control human white matter or white matter from the central nervous system (CNS) of MS patients. Autologous peripheral blood derived mononuclear cells were used as antigen presenting cells (APC). Although the majority of T-cells were found to react equally well with all preparations of MBP isolated from both control and MS white matter, we were also able to identify T-cell lines which reacted well with all preparations of MBP isolated from controls but failed to react with MBP isolated from MS white matter. These differences were unlikely to reflect differences in degradation products or excess peptides present in the MS brain since SDS-PAGE and HPLC did not show any difference in the MS samples compared to the controls, and the concentration response curves for a human T-cell clone specific for the 84-102 region of MBP were similar for all the MBP preparations. We did not detect differences in amino acid content amongst MBP preparations although single amino acid substitutions cannot be ruled out. These results raise the possibility that MBP isolated from MS brain may differ in charge microheterogeneity which would affect antigenic determinants.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunological aspects of experimental allergic encephalomyelitis and multiple sclerosis

Multiple sclerosis (MS) is the most frequent, demyelinating disease of the central nervous system (CNS) in Northern Europeans and North Americans. Despite intensive research its etiology is still unknown, but a T cell-mediated autoimmune pathogenesis is likely to be responsible for the demyelination. This hypothesis is based both on findings in MS patients and studies of an experimental animal model for demyelinating diseases, experimental allergic encephalomyelitis (EAE). Experiments in EAE have not only demonstrated which myelin antigens are able to induce the demyelinating process but also have determined the characteristics of encephalitogenic T cells, that is, their fine specificity, major histocompatibility complex (MHC) restriction, lymphokine secretion, activation requirements, and T cell receptor (TCR) usage. Based on these findings, highly specific and efficient immune interventions have been designed in EAE and have raised hopes that similar approaches could modulate the disease process in MS. Although the examination of the myelin-specific T cell response in MS patients has shown parallels to EAE, this remains an area of intensive research because a number of questions remain. This review summarizes the important lessons from EAE, examines recent findings in MS, and discusses current concepts about how the disease process develops and which steps might be taken to modulate it.

Self-determinants in autoimmune demyelinating disease: changes in T- cell response specificity

Recent research developments support the following views regarding antigen recognition in autoimmune demyelinating disease: there may be no single autoimmune target protein; diverse peptide self-determinants from multiple myelin proteins can be recognized; target determinant epitopes may differ among individuals; and target epitope recognition can change with time during the course of disease.

T lymphocyte recognition sites on peripheral nerve myelin P0 protein

Synthetic peptides corresponding to the extracellular and cytoplasmic domain of bovine (b) or rat (r) peripheral myelin P0 protein were used to establish a total of 50 short-term T cell lines (TCL) from blood of eight healthy subjects. Despite expressing different HLA-DR and HLA-DQ specificities, one or more TCL (range 1-16) specific for peptide bovine P0 19-38 could be isolated from the blood of each donor. Therefore, this peptide covers an immunodominant T cell recognition site in humans. However, when testing seven bP0-19-38-specific TCL derived from blood of two healthy subjects for recognition of the corresponding human P0 sequence, no TCL showed any proliferative response. Bovine P0-19-38 differs in only two amino acid residues from the human peptide. This observation stresses the necessity for using homologous antigens when screening for T cell-mediated autoreactivity to myelin antigens in humans. Unexpectedly, we failed to establish a single P0 peptide-specific TCL from blood of four patients with acute Guillain-Barré syndrome (GBS), in which P0 is considered a putative target autoantigen. As already suggested by others, this could indicate that T cell responses to P0 do not play a pathogenic role in all GBS cases. Alternatively, in these four patients neuritogenic P0-specific T lymphocytes may have been sequestrated to peripheral nerves.

Identification of a second T cell epitope of human proteolipid protein (residues 89-106) recognized by proliferative and cytolytic CD4+ T cells from multiple sclerosis patients

Research into the pathogenesis of multiple sclerosis (MS) has focused on myelin antigens as potential targets of autoimmune attack. Proteolipid protein (PLP) is the most abundant myelin protein comprising more than 50% of central nervous system myelin. Although PLP is a hydrophobic membrane protein which has made it difficult to study, the use of synthetic peptides based on the PLP sequence provides an alternative method for studying the immunological properties of PLP. Using peripheral blood lymphocytes from MS patients, long-term TCL established in the presence of PLP reacted weakly to PLP in proliferation assays; however, these same lines were much more reactive to synthetic peptides of PLP. Thus, we established short-term T cell lines (TCL) from the peripheral blood lymphocytes (PBL) of MS patients in the presence of five separate synthetic PLP peptides. In 6/7 MS patients, proliferative responses were elicited most often to PLP 40-60 compared to four other PLP peptides (PLP 89-106, 103-120, 125-143, and 139-154) (Pelfrey et al., 1993). Interestingly, however, the magnitude of the proliferative response was greatest in response to PLP 89-106. Characterization of PLP 89-106-responsive TCL from several MS patients, indicated that TCL proliferating to the peptide also lysed PLP 89-106 pulsed autologous targets. The majority of cytolytic PLP 89-106 TCL were CD4+ and MHC class II restricted and the predominant restriction elements were those most commonly found in MS patients. These findings suggest that the use of synthetic peptides represents a viable alternative approach to the study of PLP reactivity in humans. We report here that MS PBL recognize several PLP peptides, with the predominant responses to PLP 40-60 and PLP 89-106. Since these cells have both helper (CD4+) and cytolytic capabilities, it is possible that they may play a role in the pathogenesis or progression of MS.

Peptide determinants of myelin proteolipid protein (PLP) in autoimmune demyelinating disease: a review

This article reviews recent advances in understanding the role of myelin proteolipid protein (PLP) in autoimmune demyelination. It is drawn largely from work published within the last ten years and discusses the immunology of PLP in the historical context of what has been learned from extensive studies on the immune response to myelin basic protein (MBP). Despite the fact that PLP is the major protein constituent of mammalian myelin, its role in autoimmune demyelination has not been widely recognized. The lack of understanding about the immunology of PLP is a direct result of the biochemical characteristics of the protein. PLP is a highly hydrophobic membrane protein with limited aqueous solubility. The hydrophobicity of PLP has thwarted immunologic studies of the intact protein. Recent work has circumvented the technical obstacles of studying the intact protein by using soluble synthetic PLP peptides. This approach has rapidly resulted in a more definitive understanding of the immune response to PLP. Presently, the data indicate that: i) PLP is a major central nervous system (CNS) specific encephalitogen; ii) CD4+ T cell reactivity to discrete PLP peptide determinants can mediate the development of acute, chronic relapsing, and chronic progressive experimental autoimmune encephalomyelitis (EAE); and iii) T cell reactivity to multiple PLP determinants occurs in patients with multiple sclerosis (MS), the major human CNS demyelinating disease.

Direct binding of myelin basic protein and synthetic copolymer 1 to class II major histocompatibility complex molecules on living antigen-presenting cells--specificity and promiscuity

Copolymer 1 (Cop 1) is a synthetic basic random copolymer of amino acids that has been shown to be effective in suppression of experimental allergic encephalomyelitis and is being tested as a candidate drug for multiple sclerosis. It has been previously demonstrated that Cop 1 is immunologically cross-reactive with the autoantigen myelin basic protein (BP) and competitively inhibits the response to BP of T-cell lines and clones of different major histocompatibility complex (MHC) restrictions, of both mouse and human origin. In the present study we demonstrated the direct binding of Cop 1, using its biotinylated derivative, to MHC molecules on living antigen-presenting cells. Binding of biotinylated BP and peptide p84-102 (an immunodominant epitope of BP) was also demonstrated. Cop 1 and BP bound in a promiscuous manner to different types of antigen-presenting cells of various H-2 and HLA haplotypes. The specificity of the binding was confirmed by its inhibition with either the relevant anti-MHC class II antibodies or unlabeled analogs. Cop 1 exhibited the most extensive and fast binding to antigen-presenting cells. In addition, Cop 1 inhibited the binding of biotinylated derivatives of BP and of p84-102 to the MHC class II molecules and even displaced these antigens when already bound. Thus, these results suggest that Cop 1 indeed competes with BP for MHC binding and, thereby, inhibits T-cell responses to BP. The binding of Cop 1 to different DR alleles, probably because of its multiple MHC binding motifs, may indicate its potential as a broad-spectrum drug for multiple sclerosis.

Human myelin basic protein (MBP) epitopes recognized by mouse MBP-selected T cell lines from multiple sclerosis patients

We investigated whether myelin basic protein (MBP)-reactive T cells from multiple sclerosis (MS) patients can recognize mouse MBP since this is an expected requirement for the transfer of experimental autoimmune encephalomyelitis (EAE) into severe combined immunodeficiency (SCID) mouse-human chimeras. Peripheral blood mononuclear cells from 11 MS patients were analyzed for in vitro proliferation to mouse MBP. Six patients (55%) responded to mouse MBP at the first or second stimulation. Five T cell lines, selected with mouse MBP from five MS patients, were analyzed for their proliferation to mouse and human MBP and to a panel of synthetic peptides of human MBP. Four of the five lines recognized mouse MBP. In vitro proliferation was restricted by MHC class II in one line tested for MHC restriction. One of the five lines recognized whole human MBP and all five of the lines responded to at least one of the five synthetic peptides corresponding to human MBP residues 8-28, 67-90, 84-102, 87-99 or 130-149. These results show that MS patient T cells recognize mouse MBP and suggest that distinct human MBP epitopes are immunologically cross-reactive with epitopes of mouse MBP.

Myelin basic protein-specific T lymphocyte repertoire in multiple sclerosis. Complexity of the response and dominance of nested epitopes due to recruitment of multiple T cell clones

The human T cell response to the myelin basic protein (MBP) has been studied with respect to T cell receptor (TCR) usage, HLA class II restriction elements, and epitope specificity using a total of 215 long-term MBP-specific T cell lines (TCL) isolated from the peripheral blood of 13 patients with multiple sclerosis (MS) and 10 healthy donors. In most donors, the anti-MBP response was exceedingly heterogeneous. Using a panel of overlapping synthetic peptides spanning the entire length of human MBP, at least 26 epitopes recognized by human TCL could be distinguished. The MBP domain most commonly recognized was sequence 80-105 (31% of MS TCL, and 24% of control TCL). Sequence 29-48 was recognized more frequently by control-derived TCL (24%) than by TCL from MS patients (5%). The MBP epitopes were recognized in the context of DRB1 *0101, DRB5*0101, DRB1*1501, DRB1*0301, DRB1*0401, DRB1*1402, and DRB3*0102, as demonstrated using a panel of DR gene-transfected L cells. The TCR gene usage was also heterogeneous. V beta 5.2, a peptide of which is currently being used in a clinical trial for treatment of MS patients, was expressed by only one of our TCL. However, within this complex pattern of MBP-specific T cell responses, a minority of MS patients were found to exhibit a more restricted response with respect to their TCL epitope specificity. In these patients 75-87% of the TCL responded to a single, patient-specific cluster of immunodominant T cell epitopes located within a small (20-amino acid) domain of MBP. These nested clusters of immunodominant epitopes were noted within the amino acids 80-105, 108-131, and 131-153. The T cell response to the immunodominant epitopes was not monoclonal, but heterogeneous, with respect to fine specificity, TCR usage, and even HLA restriction. In one patient (H.K.), this restricted epitope profile remained stable for > 2 yr. The TCR beta chain sequences of TCL specific for the immunodominant region of HK are consistent with an oligoclonal response against the epitopes of this region (80-105). Further, two pairs of identical sequences were established from TCL generated from this patient at different times (June 1990 and June 1991), suggesting that some TCL specific for the immunodominant region persisted in the peripheral repertoire. The possible role of persistent immunodominant epitope clusters in the pathogenesis of MS remains to be established.

Shifts in the epitopes of myelin basic protein recognized by Lewis rat T cells before, during, and after the induction of experimental autoimmune encephalomyelitis

An epitope present in the 71-90 sequence of basic protein (BP) has been identified as the dominant epitope recognized by most Lewis rat encephalitogenic T cells isolated during experimental autoimmune encephalomyelitis (EAE). In the present study, we investigated the BP epitopes recognized by Lewis rat T cells in naive rats, in rats suffering from acute EAE, and in recovered rats. T cells isolated from the spinal cord lesions and from the lymph nodes were studied using T cell lines and bulk cultures. Virulence of the T cells was assayed by adoptive transfer. We now report that naive and recovered Lewis rats are populated with T cells reactive to a variety of BP epitopes and only a minority are specific for the 71-90 epitope. In contrast, the induction of EAE was associated with a predominance of T cells reactive to the 71-90 epitope. T cells recovered from naive, diseased, or recovered rats were found to be virulent upon passive transfer. Some of these virulent T cells were specific to BP epitopes other than the 71-90 epitope. There was no major difference in the BP specificities of T cells isolated from the lesions and from the lymph nodes. Thus, natural T cell reactivity to BP is heterogeneous and pathogenicity is not confined to one particular epitope, active disease is characterized by a dominant response to the 71-90 epitope, and recovery is marked by a return to heterogeneity.

Myelin basic protein-specific T-cell responses in identical twins discordant or concordant for multiple sclerosis

Although multiple sclerosis (MS) is thought to be an autoimmune disease, the target antigen of the immune response is unknown. Both myelin basic protein (MBP) and proteolipid protein (PLP) have been considered candidate autoantigens. Because the immune response to either foreign or self antigens is influenced by the genetic background of the host, the importance of these candidate antigens has been difficult to establish in humans because of genetic diversity. To eliminate genetic differences in MS patients and healthy controls, we have studied the MBP-specific T-cell response in 6 sets of identical twins, 3 of which were concordant and 3 discordant for MS. A total of 638 short-term T-cell lines were established and characterized for MBP-specific proliferative and cytotoxic activity, fine specificity, and human leukocyte antigen (HLA) restriction. Similar frequencies of MBP-specific T cells were observed in affected and unaffected individuals. A slightly higher percentage of cytotoxic T-cell lines was found in affected individuals. For most of the cell lines, the restriction elements were the HLA class II antigens that have been reported previously to be associated with MS; no important differences with respect to HLA restriction were found between the patients and healthy individuals. The peptide epitopes of MBP that were recognized most frequently by the T-cell lines were those previously shown to be immunodominant. Differences in specificity were seen in some discordant twins indicating that, despite genetic identity, the MBP-specific T-cell repertoire may be shaped differently. These findings indicate that differences in frequency, peptide specificity, or HLA restriction are not sufficient to implicate MBP-specific T cells in the pathogenesis of MS. However, the T-cell response to MBP may still represent one necessary component with disease occurring when this response is combined with other host characteristics such as regulation of cytokine-, adhesion molecule-, or HLA-antigen expression in the nervous system or immunoregulatory mechanisms.

Identification of a novel T cell epitope of human proteolipid protein (residues 40-60) recognized by proliferative and cytolytic CD4+ T cells from multiple sclerosis patients

Research into the pathogenesis of multiple sclerosis (MS) has focused on myelin antigens as potential targets of autoimmune attack. Proteolipid protein (PLP), which makes up more than 50% of central nervous system myelin, is a hydrophobic membrane protein with many properties that historically have made it difficult to study. The use of synthetic peptides based on the PLP sequence provides an alternative method for studying the immunological properties of PLP. Using peripheral blood lymphocytes from MS patients, long-term TCL established in the presence of PLP reacted weakly to PLP in proliferation assays; however, these same lines were much more reactive to synthetic peptides of PLP. Thus, we established short-term T cell lines (TCL) from the peripheral blood lymphocytes (PBL) of MS patients in the presence of five separate synthetic PLP peptides. In six out of seven MS patients, proliferative responses were elicited most often to PLP 40-60 compared to four other PLP peptides (PLP 89-106, 103-120, 125-143, and 139-154). Characterization of PLP 40-60-responsive TCL from a single MS patient, MS1, indicated that six out of seven TCL proliferating to the peptide also lysed PLP 40-60 pulsed autologous targets. All cytolytic PLP 40-60 TCL were CD4+ and MHC class II restricted and further analysis of MS1 TCL showed that the PLP 40-60 TCL were restricted by DR4 whereas the MBP TCL from MS1 were restricted by DR6. These findings suggest that difficulties in examining the immune response to PLP have been due to the poor response generated in vitro using the whole molecule and that the use of synthetic peptides may represent an alternative approach to the study of PLP. These results also suggest that MS PBL recognize several PLP peptides, with the predominant response to PLP 40-60. Since these cells phenotypically resemble T cells known to mediate experimental autoimmune encephalomyelitis, it is possible that they may play a role in the pathogenesis of MS.

Individual specific bias usage of HLA-DR antigens in the restriction of myelin basic protein-reactive T cell clones

Multiple sclerosis, a demyelinating disease of the human central nervous system occurs in genetically susceptible individuals through a presumably autoimmune mechanism directed against the myelin sheath. The influence of the major histocompatibility locus on T cell recognition of myelin basic protein (MBP), a suspected target autoantigen, was investigated by analyzing MBP-specific T cell clones generated from the peripheral blood of healthy individuals. Inhibition studies using monoclonal antibodies demonstrated that MBP recognition was restricted by HLA-DR antigens. MBP recognition of the majority of T cell clones from each individual was restricted predominantly by one of the DR alleles. Thus, there appears to be a bias in the use of allelic DR restricting elements for MBP responses.

A novel candidate autoantigen in a multiplex family with multiple sclerosis: prevalence of T-lymphocytes specific for an MBP epitope unique to myelination

Although the major isoform of myelin basic protein (MBP) in the healthy adult CNS is the 18.5-kDa protein, other isoforms containing exon 2 encoded protein (21.5 kDa and 20.2 kDa) exist and are expressed primarily during myelin formation. Since remyelination is a prominent feature in MS lesions, we examined the frequencies of T cell lines (TCLs) specific for epitopes within exon 2 encoded MBP (X2MBP), and also within 18.5-kDa MBP, in members of a multiplex family with MS. TCLs specific for X2MBP were as prevalent as TCLs specific for immunodominant epitopes within 18.5-kDa MBP. In addition, while frequencies of TCLs specific for 18.5-kDa MBP were no different between the affected and unaffected, the frequency of X2MBP-specific TCLs correlated with disease.

Epitope specificity and V gene expression of cerebrospinal fluid T cells specific for intact versus cryptic epitopes of myelin basic protein

Recent evidence supports the possible involvement of myelin basic protein (BP) as one of the target autoantigens in multiple sclerosis (MS), including elevated frequencies of MS blood and cerebrospinal fluid (CSF) T cells, and the presence in MS plaque tissue of V beta gene sequences and CDR3 motifs characteristic of BP-reactive T cells. Because of its proximity to the target organ, the CSF has long been thought to harbor T cells involved in the pathogenic process. In order to evaluate their frequency and response characteristics, BP-reactive T cells were isolated by limiting dilution from the CSF of patients with MS and other neurological diseases (OND) for quantitation and determination of epitope specificity and V alpha and V beta gene expression. In addition to isolates responsive to intact BP epitopes that were present at a significantly higher frequency in MS versus OND CSF, we here describe a second clonotype responsive to 'cryptic' BP epitopes that is present at approximately equal frequencies in MS and OND patients. In spite of their difference in recognition of intact versus 'cryptic' BP determinants, both clonotypes predominantly recognized epitopes in the N terminal half of human BP, using a similar V gene repertoire that included biased use of V alpha 2 and to a lesser degree V beta 7 and V beta 18. These V gene biases were not related to the epitope specificity of the T cells, indicating that V gene selection is not epitope-driven. These data suggest that there is differential recognition of intact versus 'cryptic' BP determinants in MS versus OND patients that may be related to the processing and presentation of BP to the immune system.

T cells recognizing multiple peptides of myelin basic protein are found in blood and enriched in cerebrospinal fluid in optic neuritis and multiple sclerosis

The cause of multiple sclerosis (MS) is unknown. Recently reported abnormal T-cell responses to several myelin proteins and myelin basic protein (MBP) peptides in peripheral blood constitute one line of evidence that autoimmune mechanisms could be involved in the pathogenesis of the disease. Monosymptomatic unilateral optic neuritis (ON) is a common first manifestation of MS and important to examine for a possible restriction of the T-cell repertoire early in the disease. T-cell activities to MBP and the MBP amino acid sequences 63-88, 110-128 and 148-165 were examined by short-term cultures of mononuclear cells from cerebrospinal fluid (CSF) and blood in the presence of these antigens, and subsequent detection and counting of antigen-specific T cells that responded by interferon-gamma (IFN-gamma) secretion. Most patients with MS and ON had MBP and MBP peptide-reactive T cells in CSF, amounting to mean values of between about 1 per 2000 and 1 per 7000 CSF cells and without immunodominance for any of the peptides. Numbers were 10-fold to 100-fold lower in the patients' blood. Values were similar in ON and MS, and no evidence was obtained for a more restricted T-cell repertoire in ON. The MBP peptide-recognizing T-cell repertoire was different in CSF than in blood in individual patients with ON and MS, thereby giving further evidence for an autonomy of the autoimmune T-cell response in the CSF compartment. No relations were observed between numbers of autoreactive T cells and presence of oligoclonal IgG bands in CSF or abnormalities on magnetic resonance imaging of the brain in ON or clinical variables of MS. The high numbers of MBP and MBP peptide-reactive T cells could play a role in the pathogenesis of ON via secretion of effector molecules, one of them being IFN-gamma, as well as in the transfer of ON to MS.

Human T cell autoimmunity against myelin basic protein: CD4+ cells recognizing epitopes of the T cell receptor beta chain from a myelin basic protein-specific T cell clone

We have investigated whether the normal immune system contains T cells that are able to recognize T cell receptor (TcR) determinants of autologous autoantigen-specific T cells. The T cell clone HW.BP3, specific for myelin basic protein (MBP) was isolated from a healthy donor. HW.BP3 is restricted by HLA-DR2a, and reacts to human MBP 139-153. The expressed alpha beta TcR genes of HW.BP3 were cloned and sequenced, and the sequences analyzed for potential T cell epitopes. Two synthetic peptides, one from the VDJ beta junctional (beta 1) and one from the V beta region (beta 2) of the TcR of HW.BP3, were used to select four TcR peptide-specific T cell lines from the donor of HW.BP3. All anti-TcR lines had the phenotype CD3+/CD4+/HLA-DR+/CD25+/CD45RO+, and recognized the antigen in the context of HLA-DR. Three anti-TcR lines, which had been selected for reactivity to peptide beta 1, recognized exclusively this peptide restricted by HLA-DR2b. One anti-TcR line, selected for peptide beta 2, responded to both peptides beta 1 and beta 2 when presented by autologous blood mononuclear cells, but not by HLA-DR2a- or HLA-DR2b-transfected L cells. All TcR peptide-specific T cell lines were efficiently cytotoxic. They specifically lysed autologous macrophages or HW.BP3 line cells in the presence of exogenous peptide antigen. In contrast, HW.BP3 did not present endogenous TcR peptides to the anti-TcR lines. The results demonstrate that the normal human immune system contains not only autoantigen-specific T cells, but also T cells that recognize antigenic determinants of autologous autoreactive TcR.

T-lymphocyte recognition of a portion of myelin basic protein encoded by an exon expressed during myelination

The major isoform of myelin basic protein (MBP) in the healthy adult central nervous system is the 18.5-kDa protein which is produced by mRNA derived from exons 1, 3, 4, 5, 6 and 7 of the MBP gene. Since isoforms containing exon 2-encoded protein (X2MBP) are expressed during myelin formation, we examined T cell reactivity specific for X2MBP in a disease characterized by remyelination subsequent to demyelination, multiple sclerosis (MS). T cell lines specific for X2MBP were derived from three MS patients as well as one healthy control. This suggests that candidate autoantigens in demyelinating/remyelinating diseases should include not only the major isoforms of myelin proteins, but also isoforms expressed aberrantly during a disease process since they too may be the target of a T cell-mediated autoimmune process.

A functional basis for the association of HLA class II genes and susceptibility to multiple sclerosis: cellular immune responses to myelin basic protein in a multiplex family

This study has examined the cellular response to myelin basic protein (MBP) in a multiplex family with multiple sclerosis (MS). A total of 81 MBP-specific T cell lines (TCLs) were derived from three affected siblings and four healthy siblings. No difference was observed in estimated precursor frequencies of MBP-specific TCLs or peptide specificity of TCLs when comparing affected and unaffected siblings. MBP-specific TCLs from affected siblings, however, were restricted to the DRw15/DQw6 allele more frequently than those from unaffected siblings (P < 0.02). These data suggest that restriction of autoantigen-specific T cells may be the functional basis for disease susceptibility related to HLA class II inheritance.

The synthetic 87–99 peptide of myelin basic protein is encephalitogenic in Buffalo rats

A synthetic peptide corresponding to residues 87-99 (S87-99) of myelin basic protein (BP) induced the proliferation of an encephalitogenic, BP-specific T cell line selected in vitro from inbred Buffalo-strain rats (RT1b). Active immunization with guinea pig (GP)-BP or S87-99 in complete Freund's adjuvant (CFA) and intravenous pertussigen induced acute experimental autoimmune encephalomyelitis (EAE) 10-12 days after immunization. Fifty percent of recovered rats developed a single relapse 17-21 days after immunization. T lymphocytes selected in vitro with S87-99 transferred acute, non-relapsing EAE into naive recipients. Histological examination during acute EAE revealed foci of inflammatory cells associated with demyelination in the spinal cords and peripheral nerve roots. Thus, as in several other rodent strains, the 87-99 region of BP is antigenic and encephalitogenic in the inbred Buffalo-strain rat. Additionally, the 87-99 sequence of GP-BP was predicted to be antigenic by two different methods. These results suggest that the 87-99 region of BP, which is highly conserved among mammalian species, may be widely encephalitogenic due to antigen-intrinsic properties.

Diversity of T cell receptor α and β chain genes expressed by human T cells specific for similar myelin basic protein peptide/major histocompatibility complexes

T cell receptor (TcR) alpha and beta nucleotide sequences involved in the human autoreactivity to myelin basic protein (MBP) were studied by screening cDNA libraries derived from 11 independent T lymphocyte clones (TCC) established from multiple sclerosis patients and healthy donors. The TCC with defined MBP peptide specificity and HLA-DR restriction expressed multiple TcR. Even TCC recognizing the same human MBP peptide [amino acids (aa) 139-153] in identical or very similar HLA-DR context expressed diverse TcR. Two TCC which recognized peptide aa 139-153 equally well in the context of both HLA-DR2a and -DR1 molecules used distinct TcR alpha but identical beta chains. The knowledge of TcR beta and TcR alpha chain sequences of human MBP-specific T cells will allow studies correlating structure and function of TcR and their targets in MBP autoreactivity. This may have an impact on the development of immunotherapies in multiple sclerosis.

Copolymer-1-induced inhibition of antigen-specific T cell activation: interference with antigen presentation

Copolymer-1 (Cop-1) has been shown to inhibit in vivo development of experimental allergic encephalomyelitis (EAE) in animals and has been reported to have some therapeutic benefit in relapsing/remitting multiple sclerosis (MS). The mechanism by which Cop-1 acts in vivo is not known. The present study demonstrates that Cop-1 inhibits the in vitro response of several antigen-specific murine T cell hybridomas restricted to I-A, and to a lesser extent, I-E. The ability of human myelin basic protein (MBP)-specific T cell lines (TCL) to lyse targets in the context of three HLA-DR types associated with MS was also impaired by Cop-1. The results suggest that the observed inhibition was due to competition between Cop-1 and nominal antigen for the class II major histocompatibility complex (MHC) peptide binding site.

Synthetic copolymer 1 inhibits human T-cell lines specific for myelin basic protein

Copolymer 1 (Cop 1) is a synthetic basic random copolymer of amino acids that has been shown to be effective in suppression of experimental allergic encephalomyelitis and has been proposed as a candidate drug for multiple sclerosis. Cop 1 is immunologically cross reactive with myelin basic protein (BP) and was shown to inhibit murine BP-specific T-cell lines of various H-2 restrictions. In the present study these findings were extended to include human T-cell lines. Cop 1 competitively inhibited the proliferative responses and interleukin 2 secretion of six BP-specific T-cell lines and 13 clones with several DR restrictions and epitope specificities. Conversely, BP inhibited--albeit to a lesser extent--the response of all the Cop 1-specific T-cell lines and clones, irrespective of their DR restrictions. Another random copolymer of tyrosine, glutamic acid, and alanine, denoted TGA, had no effect on these lines. Neither Cop 1 nor BP inhibited the response of lines and clones specific for purified protein derivative. Cop 1 and BP exerted their cross-inhibitory effects only in the presence of antigen-presenting cells. These results suggest that Cop 1 can compete with BP for the binding to human major histocompatibility complex molecules. In view of recent studies implicating BP reactivity in multiple sclerosis, these findings suggest a possible mechanism for the beneficial effect of Cop 1 in this disease.

Characterization of rat encephalitogenic T cells bearing non-Vβ8 T cell recepotors

In this study, we demonstrate that T cell lines specific for a synthetic peptide representing sequence 87 to 99 of myelin basic protein (MBP) are encephalitogenic in Lewis rats. However, unlike syngeneic T cells specific for MBP residues 68 to 88 which exclusively use V beta 8 in their antigen receptors, these cells do not. None of the 10 T cell lines and T hybridomas specific for MBP (87-99) used V beta 8 in their T cell receptors. Our results document for the first time that rat encephalitogenic T cells do not exclusively use V beta 8 in T cell receptors that rat encephalitogenic T cells specific for MBP (87-99) are heterogeneous and that MBP (87-99) contains at least two epitopes for rat T cells.

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 Wucherpfennig 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.

Peripheral blood mononuclear cells from multiple sclerosis patients recognize myelin proteolipid protein and selected peptides

Myelin proteolipid protein (PLP) can induce a T cell-mediated chronic relapsing autoimmune encephalomyelitis in animals and therefore is a candidate for an antigen involved in the pathogenesis of multiple sclerosis. In this report, evidence is presented that peripheral blood mononuclear cells from certain multiple sclerosis (MS) patients recognize the intact PLP molecule as well as certain synthetic PLP peptides in proliferation assays. PLP-specific T cell lines could be obtained from six of ten MS patients with early relapsing-remitting disease. These lines recognized more than one PLP peptide and the relevant peptides differed among patients. The relevance of these observations to the pathogenesis of MS remains to be determined.

Heterogeneity of the T-cell receptor beta gene rearrangements generated in myelin basic protein-specific T-cell clones isolated from a patient with multiple sclerosis

Seventeen T-cell clones derived from the peripheral blood of a patient with multiple sclerosis and reactive with a synthetic peptide corresponding to residues 152-170 of the human myelin basic protein molecule were previously shown to be cytotoxic for myelin basic protein-coated target cells. Genetic restriction studies have now demonstrated that these clones recognize myelin basic protein in association with human leukocyte antigen DRw13. Studies of the T-cell receptor beta gene rearrangements generated by these clones demonstrated 12 different patterns, as evaluated by Southern blot analysis. Thus, the human T-cell response to myelin basic protein is exceedingly heterogeneous, even among T cells that recognize the same small fragment of the molecule in association with the same class II restriction element.

Specificity of human T cell clones reactive to immunodominant epitopes of myelin basic protein

Several recently discovered lines of evidence support the involvement of myelin basic protein (BP)-specific T cells in multiple sclerosis (MS). To identify potentially relevant immunodominant T cell epitopes, human BP (Hu-BP)-reactive T cell lines were selected from MS and normal donors and tested for reactivity to cleavage fragments and synthetic peptides of Hu-BP. The MS T cell lines responded to more Hu-BP epitopes than did normal lines, showing biased recognition of the N terminal half of the molecule, and one region in the C terminal half, suggesting increased sensitization to BP. The MS lines also differed from normal lines in their decreased percentage of CD8+ T cells. One hundred nine T cell clones isolated from these lines confirmed the reactivity pattern of the lines but did not reflect the mixed phenotype, since all but three clones tested were CD4+. T cell clones from HLA-DR2 homozygous donors responded to a variety of epitopes, indicating that this molecule was permissive in its ability to restrict T cell responses. Other epitopes, including the immunodominant 149-170 sequence, were restricted by several different major histocompatibility complex (MHC) molecules from both MS and normal donors. T cell receptor (TCR) V gene products could be identified on six of 38 clones tested using monoclonal antibodies. From one HLA-DR2 homozygous donor, four of eight clones utilized V beta 5.2 in response to different BP epitopes, providing initial support for the preferential use of a limited set of V region genes in the human response to BP. Preferential TCR V gene use in MS patients would provide the rationale to regulate selectively BP-reactive T cells through immunity directed at the TCR and thus test for the first time the hypothesis that BP-reactive T cells play a critical role in the pathogenesis of MS.

Assessment of antigenic determinants for the human T cell response against myelin basic protein using overlapping synthetic peptides

Immunization of experimental animals with myelin basic protein (MBP) or with specific MBP encephalitogenic determinants induces an autoimmune central nervous system (CNS) disease, experimental allergic encephalomyelitis, often studied as a model for human demyelinating disorders. This study examines the antigenic determinants of MBP recognized by human T cells using overlapping, synthetic peptides and T cell lines and clones isolated from four HLA-typed, neurologically normal subjects. T cell lines and clones isolated from individual subjects recognized at least one and as many as five distinct T cell determinants. In some instances the peptides recognized included determinants previously shown to induce experimental allergic encephalomyelitis (EAE) in experimental animals. In this group of four subjects, some determinants of MBP, including residues 5-25, 35-47, 65-75, and 81-100, were recognized by T cells derived from more than one individual suggesting that these regions may be particularly immunogenic for humans.

Characterization of in vivo-activated T cell clones from peripheral blood of multiple sclerosis patients

In vivo-activated interleukin-2 responsive T cell clones were generated from peripheral blood (PBL) of multiple sclerosis patients (MS) and normal subjects (N) by limiting dilution analysis. The frequency with which interleukin-2 responsive cells were cloned from PBL was higher in MS than N. CD8 was the predominant phenotype expressed by both MS (85%) and N (89%) clones. Seven clones from four MS patients but none from five N subjects specifically proliferated against myelin basic protein. These studies demonstrate the existence of MBP-reactive T cells in PBL of MS patients.

Myelin autoreactivity in multiple sclerosis: recognition of myelin basic protein in the context of HLA-DR2 products by T lymphocytes of multiple-sclerosis patients and healthy donors

A panel of 20 human myelin basic protein (hMBP)-specific T-lymphocyte lines was generated from the peripheral blood of eight multiple sclerosis (MS) patients and two healthy donors, most of them expressing the HLA-DR2 haplotype, which is associated with an increased susceptibility to MS. Using HLA-DR gene-transfected mouse L-cell lines as antigen-presenting cells, we established that of the 20 hMBP-specific T-lymphocyte lines, 7 were restricted by the DR2a gene products of the DR2Dw2 haplotype. Four T-cell lines recognized hMBP in the context of the DR2b products of the DR2Dw2 haplotype. DR2b-restricted T-cell responses were demonstrable only in T-cell lines derived from MS patients. The hMBP epitopes presented by the DR2a heterodimer were mapped to peptides covering amino acid residues 1-44, 76-91, 131-145, or 139-153 and to a region spanning the thrombin-cleaved bond at Arg130-Ala131. DR2b-restricted T-cell lines recognized epitopes within amino acids 80-99 and 148-162. Peptide 139-153 was also presented in the context of HLA-DR1 molecules. Our data show that (i) in MS patients both the DR2a and DR2b products of the DR2Dw2 haplotype function as restriction elements for the myelin autoantigen hMBP, (ii) the DR2a molecule presents at least five different epitopes to hMBP-specific T lymphocytes, and (iii) anti-hMBP T-cell lines derived from individual donors can differ in their antigen fine specificity as well as in their HLA restriction.

Characterization of measles virus-induced cellular autoimmune reactions against myelin basic protein in Lewis rats

Subacute encephalomyelitis (SAME) in Lewis rats following infection with a neurotropic measles virus (MV) is associated with a cell-mediated autoimmune response (CMAI) to myelin basic protein (MBP). MBP-selected CD4+ T cell lines both from measles-infected animals as well as from rats challenged with guinea pig MBP (Gp-MBP) had a similar pattern of response in the presence of synthetic peptides to Gp-MBP and specifically responded in vitro only to the encephalitogenic and not the non-encephalitogenic or other control peptides. In primary splenic lymphocyte cultures from SAME animals, however, a low but significant T-cell response was obtained against the non-encephalitogenic peptide S67 (residues 69-81) of the Gp-MBP. Moreover, immunization of MV-infected rats with this peptide induced clinical and histological experimental allergic encephalomyelitis (EAE) in 38% of the animals. The results of the study show that the non-encephalitogenic peptide S67 can be rendered encephalitogenic in rats when an additional stimulus is given in the form of MV infection. The data indicate further that MV infection of the central nervous system (CNS) enhances the susceptibility of the CNS to autoimmune T cell aggression.