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

MicroRNAs and multiple sclerosis: from physiopathology toward therapy

INTRODUCTION

MicroRNAs (miRNAs) are an emerging group of small noncoding RNAs that regulate gene expression posttranscriptionally, by targeting messenger RNAs (mRNAs) for translational repression or degradation. They have roles in multiple facets of immunity, from regulation of cell development to activation and function in immune responses. Recent evidence underlines an involvement of miRNAs in the pathogenesis of autoimmune diseases as well as multiple sclerosis (MS).

AREAS COVERED

In this review, the current knowledge of miRNA biogenesis, diverse roles of miRNAs in different cells that could be involved in the process of the disease, and their potential therapeutic applications are summarized. The authors searched MEDLINE and Science direct databases.

EXPERT OPINION

The miRNAs in central nervous system lesions and peripheral blood are potential biomarkers for diagnostic and prognostic use. Also, miRNA mimics, small-molecule inhibitors of specific miRNAs, and antisense oligonucleotides could be therapeutic weapons that facilitate us to combat the disease.

miR-29ab1 deficiency identifies a negative feedback loop controlling Th1 bias that is dysregulated in multiple sclerosis

Th cell programming and function is tightly regulated by complex biological networks to prevent excessive inflammatory responses and autoimmune disease. The importance of microRNAs (miRNAs) in this process is highlighted by the preferential Th1 polarization of Dicer-deficient T cells that lack miRNAs. Using genetic knockouts, we demonstrate that loss of endogenous miR-29, derived from the miR-29ab1 genomic cluster, results in unrestrained T-bet expression and IFN-γ production. miR-29b regulates T-bet and IFN-γ via a direct interaction with the 3' untranslated regions, and IFN-γ itself enhances miR-29b expression, establishing a novel regulatory feedback loop. miR-29b is increased in memory CD4(+) T cells from multiple sclerosis (MS) patients, which may reflect chronic Th1 inflammation. However, miR-29b levels decrease significantly upon T cell activation in MS patients, suggesting that this feedback loop is dysregulated in MS patients and may contribute to chronic inflammation. miR-29 thus serves as a novel regulator of Th1 differentiation, adding to the understanding of T cell-intrinsic regulatory mechanisms that maintain a balance between protective immunity and autoimmunity.

Micro-RNA dysregulation in multiple sclerosis favours pro-inflammatory T-cell-mediated autoimmunity

Pro-inflammatory T cells mediate autoimmune demyelination in multiple sclerosis. However, the factors driving their development and multiple sclerosis susceptibility are incompletely understood. We investigated how micro-RNAs, newly described as post-transcriptional regulators of gene expression, contribute to pathogenic T-cell differentiation in multiple sclerosis. miR-128 and miR-27b were increased in naïve and miR-340 in memory CD4(+) T cells from patients with multiple sclerosis, inhibiting Th2 cell development and favouring pro-inflammatory Th1 responses. These effects were mediated by direct suppression of B lymphoma Mo-MLV insertion region 1 homolog (BMI1) and interleukin-4 (IL4) expression, resulting in decreased GATA3 levels, and a Th2 to Th1 cytokine shift. Gain-of-function experiments with these micro-RNAs enhanced the encephalitogenic potential of myelin-specific T cells in experimental autoimmune encephalomyelitis. In addition, treatment of multiple sclerosis patient T cells with oligonucleotide micro-RNA inhibitors led to the restoration of Th2 responses. These data illustrate the biological significance and therapeutic potential of these micro-RNAs in regulating T-cell phenotypes in multiple sclerosis.

Characterization of CD8+ T cell repertoire in identical twins discordant and concordant for multiple sclerosis

Autoreactive CD4+ and CD8+ T cells directed against CNS autoantigens may play a role in the development of multiple sclerosis (MS). Identical twins share the same genetic background but not the TCR repertoire that is shaped by the encounter with self or foreign antigens. To gain insights into the interplay between MS and T cell repertoire, peripheral blood CD4+ and CD8+ T lymphocytes and their CCR7+/CCR7- subsets from five pairs of identical twins (four discordant and one concordant for MS; none of which had taken disease-modifying therapy) were compared by TCR beta-chain (TCRB) complementary-determining region 3 (CDR3) spectratyping. CD4+ T cells generally showed a Gaussian distribution, whereas CD8+ T cells exhibited subject-specific, widely skewed TCR spectratypes. There was no correlation between CD8+ T cell oligoclonality and disease. Sequencing of predominant spectratype expansions revealed shared TCRB-CDR3 motifs when comparing inter- and/or intrapair twin members. In many cases, these sequences were homologous to published TCRs, specific for viruses implicated in MS pathogenesis, CNS autoantigens, or copaxone [glatiramer acetate (GA)], implying the occurrence of naturally GA-responding CD8+ T cells. It is notable that these expanded T cell clones with putative pathogenic or regulatory properties were present in the affected as well as in the healthy subject, thus suggesting the existence of a "MS predisposing trait" shared by co-twins discordant for MS.

Reconstitution of paired T cell receptor alpha- and beta-chains from microdissected single cells of human inflammatory tissues

We describe a strategy to "revive" putatively pathogenic T cells from frozen specimens of human inflammatory target organs. To distinguish pathogenic from irrelevant bystander T cells, we focused on cells that were (i) clonally expanded and (ii) in direct morphological contact with a target cell. Using CDR3 spectratyping, we identified clonally expanded T cell receptor (TCR) beta-chains in muscle sections of patients with inflammatory muscle diseases. By immunohistochemistry, we identified those Vbeta-positive T cells that fulfilled the morphological criteria of myocytotoxicity and isolated them by laser microdissection. Next, we identified coexpressed pairs of TCR alpha- and beta-chains by a multiplex PCR protocol, which allows the concomitant amplification of both chains from single cells. This concomitant amplification had not been achieved previously in histological sections, mainly because of the paucity of available anti-alpha-chain antibodies and the great heterogeneity of the alpha-chain genes. From muscle tissue of a patient with polymyositis, we isolated 64 T cells that expressed an expanded Vbeta1 chain. In 23 of these cells, we identified the corresponding alpha-chain. Twenty of these 23 alpha-chains were identical, suggesting antigen-driven selection. After functional reconstitution of the alphabeta-pairs, their antigen-recognition properties could be studied. Our results open avenues for combined analysis of the full TCR alpha- and beta-chain repertoire in human inflammatory tissues.

Oligoclonal T cells are infiltrating the brains of children with AIDS: sequence analysis reveals high proportions of identical beta-chain T-cell receptor transcripts

We have recently described the presence of perivascular CD3+ CD45RO+ T cells infiltrating the brains of children with AIDS. To determine whether these infiltrates contain oligoclonal populations of T cells, we amplified by PCR beta-chain T-cell receptor (TCR) transcripts from autopsy brains of four paediatric patients with AIDS. The amplified transcripts were cloned and sequenced. Sequence analysis of the beta-chain TCR transcripts from all four patients revealed multiple identical copies of TCR beta-chain transcripts, suggesting the presence of oligoclonal populations of T-cells. These TCR transcripts were novel. The presence of oligoclonal populations of T cells in the brains of these four paediatric patients with AIDS suggests that these T cells have undergone antigen-driven proliferation and clonal expansion very likely in situ, in the brains of these AIDS patients, in response to viral or self-antigens. Although the specificity of the clonally expanded beta-chain TCR transcripts remains to be elucidated, none of the beta-chain TCR transcripts identified in this study were identical to those specific for HIV-1 antigens that are currently reported in the GENBANK/EMBL databases. Certain common CDR3 motifs were observed in brain-infiltrating T cells within and between certain patients. Large proportions (24 of 61; 39%) of beta-chain TCR clones from one patient (NP95-73) and 2 of 27 (7%) of another patient (NP95-184-O) exhibited substantial CDR3 homology to myelin basic protein (MBP)-specific TCR derived from normal donors or TCR expressed in the brain of patients with multiple sclerosis (MS) or with viral encephalitis. These two patients (NP95-73 and NP95-184-O) also shared HLA class II with the normal donors and the MS patients who expressed these homologous TCR. Pathologic examination at autopsy of the brains revealed the presence of myelin pallor only in patient NP95-73. T-cell clones identified in the brain of patients NP95-73 and NP95-184-O may recognize MBP or another CNS self antigen and this recognition may be restricted by either DRB1*15 or DQB1*0602 specificities.

Substantial proportions of identical β-chain T-cell receptor transcripts are present in epithelial ovarian carcinoma tumors

To determine whether clonally expanded T cells are present in tumor specimens from patients with epithelial ovarian carcinoma (EOC) we amplified by the non-palindromic adaptor PCR (NPA-PCR) or by Vbeta-specific PCR beta-chain T-cell receptor (TCR) transcripts from these tumor specimens. The amplified transcripts were cloned and sequenced. Sequence analysis revealed the presence of substantial proportions of multiple identical copies of beta-chain TCR transcripts, suggesting the presence of clonal expansions of T cells in these patients, which were statistically significant by the binomial distribution in seven of nine patients. Independent amplification in separate experiments of beta-chain TCR transcripts from one patient by either NPA-PCR or by Vbeta-specific PCR, followed by cloning and sequencing, revealed identical clonal expansions irrespectively of the amplification method used. Multiple identical copies of beta-chain TCR transcripts can be derived only by specific antigen-driven proliferation and clonal expansion of the T-cell clones which recognize these antigens. Because of the very large size of the TCR repertoire, the probability of finding by chance multiple identical copies of these transcripts within an independent sample of T cells is negligible. These results demonstrate that T cells infiltrating solid tumor specimens or malignant ascites of patients with EOC contain monoclonal/oligoclonal populations of T cells.

Antigen recognition properties of a Vgamma1.3Vdelta2-T-cell receptor from a rare variant of polymyositis

Previously we partially characterized an autoreactive human Vgamma1.3Vdelta2-T-cell receptor (TCR) that had originally been identified in muscle of a patient with an unusual form of polymyositis. This TCR recognizes a muscle-associated auto-antigen in a CDR3-dependent, MHC non-restricted way. Here we show that this TCR also recognizes an antigen from Escherichia coli. Like the muscle-associated mammalian antigen, the bacterial antigen is recognized in a CDR3-dependent, but MHC-non-restricted way. Both antigens have strikingly similar molecular characteristics suggesting that their epitopes are at least very similar. The dissociation kinetics of the bacterial antigen-TCR complexes was investigated by surface plasmon resonance using soluble single-chain TCR molecules produced in COS-7 cells. The measured dissociation rate constant (k(off)=5.7 x 10(-3) s(-1)) shows that the complexes dissociate more slowly than most previously described antigen/alphabeta-TCR complexes, but much faster than antibody/antigen pairs. These results (a) provide further insight into the molecular properties of this unusual TCR, and (b) should help in future attempts to identify the elusive target antigen(s).

An autoreactive gamma delta TCR derived from a polymyositis lesion

To investigate the role of gammadelta T cells in human autoimmune disease we expressed and characterized a gammadelta TCR from an autoimmune tissue lesion. The TCR was first identified in a rare form of polymyositis characterized by a monoclonal infiltrate of gammadelta T cells which invaded and destroyed skeletal muscle fibers. The Vgamma1.3-Jgamma1-Cgamma1/Vdelta2-Jdelta3 TCR cDNA of the original muscle invasive gammadelta T cell clone was reconstructed from unrelated cDNA and transfected into the mouse hybridoma BW58alpha(-)beta(-). Appropriate anti-human gammadelta TCR Abs stimulated the TCR transfectants to produce IL-2, thus demonstrating that the human gammadelta TCR functionally interacted with murine signaling components. The transfected Vgamma1.3/Vdelta2 TCR recognized a cytosolic protein expressed in cultured human myoblasts and TE671 rhabdomyosarcoma cells. The Ag was recognized in the absence of presenting cells. Using a panel of control gammadelta TCR transfectants with defined exchanges in different positions of both TCR chains, we showed that the gammadelta TCR recognized its Ag in a TCR complementarity-determining region 3-dependent way. To our knowledge, this is the first example of a molecularly defined gammadelta TCR directly derived from an autoimmune tissue lesion. The strategy used in this study may be applicable to other autoimmune diseases.

Short-term dynamics of circulating T cell receptor V beta repertoire in relapsing-remitting MS

To understand the short-term dynamics of the circulating T cell receptor V beta (TCRBV) repertoire in relapsing-remitting multiple sclerosis (MS), we monitored the TCRBV profiles of untreated MS patients and healthy controls. Expansions of TCRBV genes in MS patients were significantly more frequent than in controls (P<0.001), were predominantly oligoclonal (80%) and were significantly correlated with immune responses to myelin basic protein (MBP) (P<0.02) and with inflammatory disease activity detected by magnetic resonance imaging (MRI) (P<0.05). Autoreactive T cell responses against myelin antigens may be implicated in perturbations of TCR repertoire in untreated MS patients, detectable even in the absence of clinically evident manifestations.

Kinetic profiles of cerebrospinal fluid anti-MBP in response to intravenous MBP synthetic peptide DENP(85)VVHFFKNIVTP(96)RT in multiple sclerosis patients

Multiple sclerosis [MS], a demyelinating disease of the central nervous system associated with inflammation and gliosis, may be an autoimmune disease with T lymphocytes and autoantibodies to myelin protein(s). This study deals exclusively with B cell autoimmunity to myelin basic protein (MBP). T lymphocytes and anti-MBP share a common MBP epitope located between P(85) and P(96) which contains the essential contact residues H(88)FFK(91) for the trimolecular complex. The purpose of this Phase I open label clinical study was to monitor CSF anti-MBP in patients with chronic progressive MS subsequent to IV administration of synthetic peptide (sp) MBP82-98 namely DEN(85)VVHFFKNIVTP(96)RT. Fifty-six patients who participated in this project were assigned to two groups: a 'control group' of 15 patients who received IV saline injections every 6 months for the first 2 years of the study and a 'peptide group' of 41 patients who received IV spMBP82-98 from the beginning of the study and then infrequently subsequent to a rise of their CSF anti-MBP. In the control group antibody levels remained persistently elevated during the 2 year period. Patients in the 'peptide group' segregated into four kinetic profiles: Cohort A (15 patients) illustrated prolonged anti-BMP suppression into the normal range. Cohort B (10 patients) illustrated significant anti-MBP suppression into the normal range for shorter durations. Cohort C (eight patients) showed significant CSF anti-MBP suppression after the initial injection but lost the ability to suppress the autoantibody titer following subsequent injections. Cohort D (eight patients) failed to show significant CSF anti-MBP suppression. In conclusion the B cell tolerizing effect of spMBP82-98 segregated into four kinetic profiles; this molecular variability should be considered in attempts to develop specific 'peptide therapies' for the broad range of clinical profiles currently diagnosed as 'multiple sclerosis'. Multiple Sclerosis (2000) 6 300 - 311

Immunoglobulin variable regions usage by B-lymphocytes infiltrating a human breast medullary carcinoma

Breast medullary carcinoma are heavily infiltrated by B-lymphocytes and associated with a good prognosis despite their high histological grade. We investigated the Ig repertoire of B-lymphocytes infiltrating one such tumour. A single cell suspension was obtained from a tumor specimen by enzymatic digestion. VH, Vkappa, and Vlambda regions were amplified by RT-PCR using mixtures of primers optimized to maximize the diversity of the PCR products. They were then cloned and sequenced. Analysis of 9 VH, 5 Vkappa, and 10 Vlambda sequences using the Kabat database indicated that several VH and VL region subgroups (I, II and III) are expressed by B-lymphocytes infiltrating this tumor. The analysis of CDR3 regions also showed a variability, although some VH and VL clones exhibited identical or nearly identical sequences. Thus, the B-cell infiltration observed in this breast medullary carcinoma does not reflect a monoclonal proliferation and represents an oligoclonal or a polyclonal B-cell proliferation.

Structural Aspects of the Interaction Between Heterogeneic Human Papillomavirus Type 1 E4-Specific T Cell Receptors and the Same Peptide/HLA-DQ8 Complex

TCR usage has been studied in a panel of Th cell clones specific for the same peptide epitope (P N S Q D R G R P R R S D), derived from the human papillomavirus type 1 (HPV1) E4 protein, and restricted through HLA-DQ8. After identifying the V, D, and J genes used by the TCRs and sequencing across the V(D)J junctions, five different α-chain sequences and five different β-chain sequences, comprising six independent clones, were identified. A structural model of our E4 peptide/HLA-DQ8 complex predicted that the guanidinyl side chain on the arginine residue at position 6 of the peptide could exist in different orientations. An intramolecular interaction between this arginine and the glutamine residue at position four appeared to control this orientation. Interacting HPV1 E4-specific TCRs would therefore have to recognize the complex in different conformations, and molecular modeling of the TCRs suggested that this could be achieved by changing the dimensions of the central pocket formed where the CDR3 loops of the TCR α- and β-chains converge. It is known that interactions between bound peptide and amino acid residues lining the peptide-binding cleft of HLA molecules are important for determining the conformation and orientation of the peptide/MHC complex. The suggestion here that intramolecular interactions between amino acids of close proximity on the bound peptide are also important adds a further level of complexity to the mechanism by which TCRs interact with Ag.

T-cell responses to myelin antigens in multiple sclerosis; relevance of the predominant autoimmune reactivity to myelin oligodendrocyte glycoprotein

Until recently, the search for the 'culprit' autoantigen towards which deleterious autoimmunity is directed in multiple sclerosis (MS) centered mostly on myelin basic protein (MBP) and proteolipid (PLP), the two most abundant protein components of central nervous system (CNS) myelin, the target tissue for the autoimmune attack in MS. Although such research has yielded important data, furthering our understanding of the disease and opening avenues for possible immune-specific therapeutic approaches, attempts to unequivocally associate MS with MBP or PLP as primary target antigens in the disease have not been successful. This has led in recent years to a new perspective in MS research, whereby different CNS antigens are being investigated for their possible role in the initiation or progression of MS. Interesting studies in laboratory animals show that T-cells directed against certain non-myelin-specific CNS antigens are able to cause inflammation of the CNS, albeit without expression of clinical disease. However, reactivity to these antigens by MS T-cells has not been demonstrated. Conversely, reactivity by MS T-cells to non-myelin-specific antigens such as heat shock proteins, could be observed, but the pathogenic potential of such reactivity has not been corroborated with the encephalitogenicity of the antigen. More relevant to MS pathogenesis may be, as we outlined in this review, the autoimmune reactivity directed against minor myelin proteins, in particular the CNS-specific myelin oligodendrocyte glycoprotein (MOG). Here, we review the current knowledge gathered on T-cell reactivity to possible target antigens in MS in the context of their encephalitogenic potential, and underline the facets which make MOG a highly relevant contender as primary target antigen in MS, albeit not necessarily the only one.

Lack of over-expression of T cell receptor Vbeta5.2 in myelin basic protein-specific T cell lines derived from HLA-DR2 positive multiple sclerosis patients and controls

Based on studies reporting an overexpression of certain V genes in myelin basic protein (MBP)-specific T cells from MS patients, immunotherapies targeting single TCR (Vbeta5.2, Vbeta6.1) are currently under way. In order to assess the basic assumption for one of these therapeutic strategies, i.e. the overexpression of Vbeta5.2 by MBP-specific T cells, we analyzed 100 MBP-specific T cell lines (TCL) for Vbeta5.2 expression. Only 4 out of 100 TCL expressed Vbeta5.2, and expression of this TCR gene is therefore not more frequent than expected from the normal peripheral blood distribution.

Insights into the aetiology and pathogenesis of multiple sclerosis

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system, and the most common neurological disease affecting young adults. Multiple sclerosis is a clinically heterogeneous disorder. It is believed to be an autoimmune disease, with cell-mediated and humoral responses directed against myelin proteins. This hypothesis largely comes from pathological parallels with an animal model, experimental autoimmune encephalomyelitis (EAE). Autoimmunity to myelin proteins in humans may be inadvertently triggered by microbes which have structural homologies with myelin antigens (molecular mimicry). As with other autoimmune diseases, susceptibility to MS is associated with certain MHC genes/haplotypes. Full genomic screening of mutiplex families has underscored the role for MHC genes as exerting moderate but the most significant effects in susceptibility. The primary target autoantigen in MS has yet to be definitively identified, but as well as the major myelin proteins, it is now clear that minor myelin components, such as myelin oligodendrocyte glycoprotein (MOG) may play a primary role in disease initiation. This review examines the current knowledge about the aetiology and pathogenesis of MS, and the important similarities with EAE. A better understanding of the molecular mechanisms of autoimmune pathology will provide the basis for more rational immunotherapies to treat 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.

Therapeutic potential of phosphodiesterase type 4 inhibition in chronic autoimmune demyelinating disease

It was recently demonstrated that selective phosphodiesterase type 4 (PDE4) inhibition suppresses the clinical manifestations of acute experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS), and inhibits the production of tumor necrosis factor-alpha (TNF-alpha), a pathogenetically central cytokine. Since the most common presentation of MS in humans is a relapsing-remitting course, we investigated the therapeutic potential of PDE4 inhibition in the relapsing-remitting EAE model of the SJL mouse. Administration of rolipram, the prototypic PDE4 inhibitor, reduced the clinical signs of EAE during both the initial episode of disease and subsequent relapses. In parallel, there was marked reduction of demyelination and also less inflammation throughout the central nervous system (CNS) of rolipram-treated animals. Gene expression of proinflammatory cytokines in the CNS was reduced in most of the rolipram-treated animals. Additional experiments demonstrated that PDE4 inhibition acted principally by inhibiting the secretion of Th1 cytokines, however, the encephalitogenic potential of myelin basic protein-specific T cells was not impaired. Our findings suggest that PDE4 inhibitors are a promising cytokine-directed therapy in chronic demyelinating disease.

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.

Immunological aspects of experimental allergic encephalomyelitis and multiple sclerosis and their application for new therapeutic strategies

The etiology of multiple sclerosis (MS), a demyelinating disorder of the central nervous system (CNS), is not yet known. Immunological, clinical and pathological studies suggest, however, that T lymphocytes directed against myelin antigens are involved in the pathogenesis of MS. The examination of an experimental animal model for MS, experimental allergic encephalomyelitis (EAE), demonstrated that myelin basic protein-(MBP) or proteolipidprotein-(PLP) specific T cells mediate the destruction of CNS myelin. In recent years, elegant studies in EAE showed that encephalitogenic T cells recognize short peptides of MBP or PLP in the context of MHC/HLA-class II molecules, express a restricted number of T cell receptor (TCR) molecules and secrete interferon-gamma and tumor necrosis factor-alpha/beta. Understanding the pathogenetic steps of demyelination at the molecular level led to highly specific immunotherapies of EAE targeting each individual molecule. MBP- and PLP-specific T cells with similar properties could also be isolated from MS patients and control individuals. Due to their heterogeneity in terms of specificity, function and TCR usage, it was difficult, however, to draw definite conclusions from these results, so far. The recent approval of interferon-beta, a cytokine that antagonizes a number of the effects of interferon-gamma, for the treatment of MS has raised great interest in examining novel strategies for immunotherapies in MS. The basic concepts as well as the current candidates for such new immunotherapies will be outlined in this brief article.

Experimental autoimmune uveitis: molecular mimicry and oral tolerance

Intraocular inflammatory disease or uveitis, which affects the uveal tract and the retina of the eyes in human, is the major cause of visual impairment. Experimental autoimmune uveitis (EAU) is a T-cell-mediated autoimmune disease directed against retinal proteins and has been studied in several mammalian species including subhuman primates as a model for human posterior uveitis. Autoimmune responses provoked by molecular mimicry occur when the nonself and host determinants are similar enough to cross-react yet different enough to break immunological tolerance, and is one of the proposed mechanisms for induction of autoimmune diseases. Therapeutic immunomodulatory strategies have been used to induce antigen-specific peripheral immune tolerance in animal models of T-cell-mediated autoimmune diseases by oral administration of autoantigens. Oral tolerance leads to unique mechanisms of tissue and disease-specific immunosuppression, which would circumvent the immunotherapeutic problem of multiple target tissue autoreactivity. Several groups have investigated the effects of delivering autoantigens across gastric mucosal surfaces. This review briefly discusses molecular mimicry and the mechanism of induction of oral tolerance with respect to immunopathogenesis of T-cell-mediated autoimmune disease in general and EAU in particular.

Sequence comparisons of the CDR3 hyper-variable loops of human T cell receptors specific for three major T cell epitopes of the birch pollen allergen Bet v 1

We have analysed the T cell receptor (TCR) alpha and beta chain sequences of 16 human CD4+ T cell clones (TCCs) specific for three important epitopes of the major birch pollen allergen Bet v 1. The TCCs were raised from the peripheral blood of eight patients with birch pollen allergy, showing allergic rhino-conjunctivitis and allergic asthma. The TCCs from these individuals were specific for Bet v 1-derived peptides: amino acids (aa)77-92 (epitope 1), aa93-108 (epitope 2) and aa113-126 (epitope 3). The DNA sequence analysis of the TCRAV and BV regions revealed heterogeneous repertoires for recognition of the peptides. Multiple combinations of AV/AJ and BV/BJ were used. However, some inter-individual restriction was evident. A limited selection of AVS and the normally infrequently used BV1S4 was obvious in TCCs specific for epitope 1. The TCRBV13 was more frequent in TCCs recognizing epitope 3. A very narrow distribution in length could be seen in the CDR3 sequences of the beta chain of TCRs with specificity for epitopes 1 and 2. Inter-individual positional micro-restriction was observed for the aa motif LR in the tCDR3 (epitope 1), for the aa residue M in the alphaCDR3 and for the aa residue G in the betaCDR3 (epitope 3). Our results illustrate clearly that each antigenic peptide derived from a single allergen, is capable of selecting different characteristics in the responding repertoire of TCRs, thus increasing the complexity of allergen-recognition by T lymphocytes. Therefore, our findings limit the potential use of TCR targeted therapeutical strategies in Type I allergy.

Autoreactive T-cells in Goodpasture's syndrome recognize the N-terminal NC1 domain on alpha 3 type IV collagen

Goodpasture's syndrome is mediated by immunopathogenic autoantibodies to the alpha 3 NC1 domain of type IV collagen. It is not known whether collaborating T-cells participate in this autoreactive response. Here we describe the first T-cell clone isolated from a Goodpasture patient autoreactive to alpha 3 type IV collagen of glomerular basement membrane. To investigate cellular autoreactivity, T-cells from Goodpasture patients or controls were isolated and stimulated by purified native or recombinant type IV collagen proteins and synthetic oligopeptides. Cell surface markers, the T-cell receptor repertoire, and MHC-restriction were analyzed. T-cell clones specific for the alpha 3 (IV) NC1 domain were established in two Goodpasture patients, but not in controls. One of the three CD8+ T-cell clones was characterized further. It was MHC class I restricted (HLA-A11) and expressed the T-cell receptor V beta 5.1. chain. This clone specifically recognized a motif at the N-terminal area of the alpha 3 (IV) NC1 domain (AA 51 to 59: GSPATWTTR). We conclude that autoreactive T-cells exists in Goodpasture patients and may play a crucial role in the inflammatory process. T-cell clones are autoreactive to the alpha 3 (IV) NC1 domain. At least for one of the clones, the T-cell epitope is different from the putative antibody-binding site.

Reactivity of mouse T-cell hybridomas expressing human Vbeta gene segments with staphylococcal and streptococcal superantigens

A panel of 15 mouse T-cell hybridomas, each expressing a different human Vbeta gene segment (hVbeta) in an otherwise mouse T-cell receptor (i.e., mouse alpha chain and CD3 complex), was constructed by transfection of hVbeta/mouse Cbeta chimeric T-cell receptor (TCR)-beta genes into a mouse T-cell hybridoma recipient lacking the endogenous TCR-beta chain. Several qualities that are conferred by the hVbeta chain of the TCR are retained in the chimeric human-mouse TCR complex: a large panel of hVbeta-specific antibodies specifically stained the hVbeta expressed by the mouse T-cell hybridomas. Moreover, hVbeta-transfected mouse cells could readily produce interleukin 2 when stimulated by superantigens presented by antigen-presenting cells. These characteristics made it possible to refine the reactivity of 17 superantigen preparations with the available transfected Vbetas. Each superantigen gave a characteristic pattern of reactivity on the transfectants. Positive reactivities with some of these transfectants, which differ only by the expressed hVbeta, demonstrate unambiguously the superantigenic character of a protein or fraction and its potential to react with the corresponding Vbetas. Therefore, these hVbeta-transfected cells constituted a valuable tool for determining "specificity fingerprints" of known or putative superantigens. First, commonly used, commercially available superantigens such as staphylococcal enterotoxin B and toxic shock syndrome toxin-1 (TSST-1) showed additional Vbeta reactivities, compared with those of their recombinant counterparts. This stresses the importance of using defined preparations of superantigens for the definition of Vbeta specificities. Second, the stimulatory pattern of a strain of Streptococcus pyogenes demonstrated that this strain, unlike others, produces a potent Vbeta 8-specific superantigen that is an yet undefined at the molecular level.

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.

Analysis of the T-cell receptor repertoire of human T-cell leukemia virus type 1 (HTLV-1) Tax-specific CD8+ cytotoxic T lymphocytes from patients with HTLV-1-associated disease: evidence for oligoclonal expansion

Human T-cell leukemia virus type 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a chronic, progressive neurological disease characterized by marked degeneration of the spinal cord and the presence of antibodies against HTLV-1. Patients with HAM/TSP, but not asymptomatic carriers, show very high precursor frequencies of HTLV-1-specific CD8+ T cells in peripheral blood and cerebrospinal fluid, suggestive of a role of these T cells in the pathogenesis of the disease. In HLA-A2+ HAM/TSP patients, HTLV-1-specific T cells were demonstrated to be directed predominantly against one HTLV-1 epitope, namely, Tax11-19. In the present study, we analyzed HLA-A2-restricted HTLV-1 Tax11-19-specific cytotoxic T cells from three patients with HAM/TSP. An analysis of the T-cell receptor (TCR) repertoire of these cells revealed an absence of restricted variable (V) region usage. Different combinations of TCR V alpha and V beta genes were utilized between, but also within, the individual patients for the recognition of Tax11-19. Sequence analysis of the TCR showed evidence for an oligoclonal expansion of few founder T cells in each patient. Apparent structural motifs were identified for the CDR3 regions of the TCR beta chains. One T-cell clone could be detected within the same patient over a period of 3 years. We suggest that these in vivo clonally expanded T cells might play a role in the pathogenesis of HAM/TSP and provide information on HTLV-1-specific TCR which may elucidate the nature of the T cells that infiltrate the central nervous system in HAM/TSP patients.

Experimental immunotherapies for multiple sclerosis

Multiple sclerosis (MS) is a chronic demyelinating disease affecting the central nervous system (CNS) principally in young adults. Although its etiology is as yet unknown current evidence suggests that tissue damage is mediated by autoimmune T cells. The examination of an experimental animal model for MS, experimental allergic encephalomyelitis (EAE), has demonstrated that myelin basic protein (MBP)- or proteolipid protein (PLP)-specific T cells mediate the destruction of CNS myelin. In recent years, elegant studies in EAE have shown that encephalitogenic T cells recognize short peptides of MBP or PLP in the context of MHC/HLA-class II molecules, express a restricted number of T cell receptor (TCR) molecules and secrete interferon-gamma and tumor necrosis factor-alpha/beta. Understanding the pathogenetic steps in lesion development at the molecular level led to highly specific immunotherapies for EAE targeting each individual molecule. It has been the hope of many investigators that immunological events resembling those in EAE can be found in patients with MS and that the specific immunotherapies effective in EAE could also be applied to MS. However, to date, the evidence for a unique immunological abnormality in MS is not strong. Although MBP- and PLP-specific T cells with properties similar to those that are encephalitogenic in animals can be isolated from patients, they are not specific for MS and occur with similar frequency in controls. In addition, the variability in specificity and TCR usage has raised questions regarding the relevance of these cells in patients. The importance of the T cell responses to myelin antigens in MS may not be established until the effects of abrogating their activity through specific therapies targeting the trimolecular complex (TMC) have been demonstrated. Consequently, attention has begun to focus on modifying the biology of the MS lesion rather than targeting the initiating event at the level of the TMC, and the success of this approach is reflected by the effect of interferon-beta on lesion development in MS. The recent approval for the use of interferon-beta for the treatment of relapsing-remitting MS has raised great interest in examining novel strategies for immunotherapies in MS. The basic concepts as well as the current candidates for such new immunotherapies will be outlined in this short review.

Diversity of human T cell receptor sequences of T cell clones with specificity for Bet v 1 peptide/MHC II complexes

T cell clones (TCC) were raised from the peripheral blood of patients suffering from tree pollen allergy. All TCC were restricted by HLA-DR molecules. In order to investigate possible intervention targets in Type I allergic diseases, we have examined T cell receptor (TCR) alpha- and beta-chain nucleotide sequences of several allergen-reactive human CD4+ TCC specific for four frequently found epitopes of Bet v 1, the major birch pollen allergen. In general, TCC specific for the 4 epitopes investigated, used diverse TCRAV and TCRBV gene segments. Moreover, the junctional regions encoding the third complementarity determining regions (CDR3) of the TCR showed striking heterogeneities in length and amino acid composition. A more restricted use of two J gene segments (TCRBJ1S4 and 2S7) was only observed in the beta-chain of TCR used by TCC specific for epitope 1. In addition, all TCC specific for epitope 4 showed an arginine residue in the N-terminal region of their TCRBV CDR3 loops despite their sequence diversities. In view of the striking heterogeneities found, therapeutical strategies aimed at the clonal deletion of allergen-specific T cell clones, providing help for IgE synthesis, may not be feasible. Moreover, our results cast a doubt on the theory, that the CDR3 exclusively provides the primary contact with the peptide bound in the major histocompatibility (MHC) groove, and suggest additional interaction with MHC class II.

Clonal dominance and selection for similar complementarity determining region 3 motifs among T lymphocytes responding to the HLA-DR3-associated Mycobacterium leprae heat shock protein 65-kd peptide 3-13

In order to establish whether specific MHC class II-peptide complexes are capable of selecting TCR V regions, we investigated in detail the TCR beta chain used in the recognition of HLA-DR3 restricted hsp65 peptide 3-13 in a tuberculoid leprosy patient. Using RT-PCR, a clear dominance of the TCRBV5 gene family was observed in a hsp65 peptide 3-13-specific T-cell line; however, not in fresh, unstimulated PBMCs, PHA-stimulated PBMCs, or a T-cell line specific for tetanus toxoid. DNA sequence analysis of the TCR V regions, comprising TCRBV5 genes, derived from the hsp65 peptide 3-13-specific T-cell line revealed the exclusive usage of the TCRBV55S1 gene segment and a predominance of one V-D-J gene rearrangement, which is indicative of clonal expansion of these T lymphocytes. Additional highly similar V-D-J gene rearrangements were detected at a low level in this hsp65 peptide 3-13 specific T-cell line. These conserved junctional regions (CDR3 regions) could not be detected within the TCRBV5 gene family of fresh PBMCs, PHA-stimulated PBMCs, hsp65, and tetanus-toxoid-specific T-cell lines from this patient. The observations in this tuberculoid leprosy patient reveal that an HLA class-II-restricted T-cell response results in selection of TCRBV regions which are highly similar in amino acid composition to the CDR3 region within the expanding TCRBV regions.

T cell receptor V beta gene expression in experimental herpes stromal keratitis

Our study examined T cell receptor (TCR) V beta mRNA expression in a murine model of experimental herpes simplex keratitis (HSK). We employed a polymerase chain reaction (PCR) technique to detect TCR V beta mRNA expression in the inoculated eyes of both HSK-susceptible and HSK-resistant mice at different time points after corneal inoculation with herpes simplex virus type 1 (HSV-1), followed by Southern blotting and densitometry analysis. In eyes from HSK-susceptible C.AL-20 mice, a more diverse TCR V beta transcript usage pattern was detected as compared with that seen in HSK-resistant C.B-17 mice. V beta 8 family members were expressed in both strains of mice at days 11, 14 and 21 post-inoculation. By densitometry, at day 11, the intensity of expression of V beta 8.2 and V beta 8.3 message was significantly greater in the eyes of C.AL-20 mice; V beta 8.1 was expressed only in C.B-17 mice. There were obvious differences in the TCR V beta expression between HSK-susceptible and HSK-resistant mice. The differences in the intensity of the message expressed by V beta 8 family members between the two strains could be correlated to previous experiments that showed V beta 8.1,2+ T cells as the main infiltrating cells in the corneas of HSK-susceptible mice by day 11 and 14 after challenge with HSV-1.

Unique T-cell receptor junctional sequences found in multiple sclerosis and T-cells mediating experimental allergic encephalomyelitis

We have used two approaches to isolate TCR sequences that are unique to patients with multiple sclerosis. One strategy was to sequence TCR gene rearrangements directly from MS lesions. The second strategy utilized T-cell clones with a selectable mutation that are found only in MS patients. The selection of T-cell clones with mutations in the hypoxanthine guanine phosphoribosyltransferase (hprt) gene was used to isolate T-cells reactive to myelin basic protein (MBP) in patients with multiple sclerosis (MS). These T-cell clones are activated in vivo, and are not found in healthy individuals. The third complementarity determining regions (CDR3) of the T-cell receptor (TCR) alpha and beta chains are the putative contact sites for peptide fragments of MBP bound in the groove of the HLA molecule. The TCR V gene usage and CDR3s of these MBP-reactive hprt- T-cell clones are homologous to TCRs from other T-cells relevant to MS, including T-cells causing experimental allergic encephalomyelitis (EAE) and T-cells found in brain lesions and in the cerebrospinal fluid (CSF) of MS patients. In vivo activated MBP-reactive T-cells in MS patients may be critical in the pathogenesis of MS.

A review of T-cell receptors in multiple sclerosis: clonal expansion and persistence of human T-cells specific for an immunodominant myelin basic protein peptide

Understanding the immune response to myelin antigens in regard to the peptide/MHC/TCR complex is important in defining pathogenesis of demyelinating autoimmune diseases and in developing antigen-specific therapies. We previously reported that individual multiple sclerosis patients may use certain dominant TCR V beta chains to recognize immunodominant MBP peptides. In examining the TCR beta chain usage, we observed repeated TCR VDJ sequences among different T-cell lines isolated from the same patient. This suggested that a few expanded T-cell clones may dominate the immune response to immunodominant MBP peptides. Here, we report experiments where TCR rearrangements were used as a probe for the clonal origin of MBP specific T-cells cultured from blood lymphocytes of MS patients and normal subjects. In two patients with the DR2 haplotype that were analyzed in detail, the T-cell response to MBP was focused on the MBP (84-102) peptide and in vivo expanded population(s) dominated the response to the MBP (84-102) peptide. Two MBP (84-102) specific T-cell clones from a normal subject with the DR2 haplotype were also found to have identical TCR sequences. Clonality was proven by demonstrating that independent clones had identical TCR alpha and beta chain sequences as well as identical sequences of a TCR gamma chain or of a second TCR alpha chain rearrangement. These data suggest that the response to human MBP is dominated in at least some subjects by expanded clones that may persist in vivo for relatively long periods of time.

T-cell receptor gene expression in tumour-infiltrating lymphocytes and peripheral blood lymphocytes of patients with nasopharyngeal carcinoma

The T-cell receptor (TCR) repertoire expression of tumour-infiltrating lymphocytes (TILs) from 19 nasopharyngeal carcinoma (NPC) biopsies was compared with those of lymphocytes from 18 control nasopharyngeal biopsies. mRNA was extracted from these lymphocytes and the cDNA transcribed. A panel of 18 V alpha- and 21 V beta-specific primers was used to detect the TCR gene use from cDNA. The use of V alpha and V beta genes was restricted in TILs compared with lymphocytes from biopsies. The frequencies of V alpha 2, V alpha 3, V alpha 9, V alpha 10, V alpha 11, V alpha 13, V alpha 14, V alpha 15, V beta 11, V beta 15 and V beta 20 were decreased and the frequencies of V alpha 10 [Pc = 0.04; relative risk (RR) = 0.05], V alpha 11 (Pc = 0.02; RR = 0.07), V alpha 13 (Pc = 0.002; RR = 0), V alpha 14 (Pc = 0.04; RR = 0.05), V beta 14 (Pc = 0.001; RR = 0.03) and V beta 20 (Pc = 0.001; RR = 0.03) remained significantly reduced after correction for the number of families typed. The frequency of V alpha 17 was higher in NPC biopsies than in NPC PBLs (P = 0.05), and the frequency of V beta 15 was lower in NPC biopsies than in NPC PBLs (P = 0.02). The frequencies of V alpha 17 and V alpha 18 in HLA-B46+ patients were significantly lower (P = 0.009; P = 0.044) than in B46+ controls. The results suggest that the restriction of TCR gene use in NPC patients may be important in NPC pathogenesis.

Suppression of experimental autoimmune encephalomyelitis in Lewis rats by antibodies against CD2

The immunotherapeutic potential of three anti-rat CD2 monoclonal antibodies (mAb) (OX34, OX54, OX55) and the combination of OX54 with OX55 was tested in Lewis rat experimental autoimmune encephalomyelitis (EAE). In actively induced EAE, a single injection of OX34 2 days before immunization with myelin basic protein (MBP) in complete Freund's adjuvant (CFA) completely prevented or greatly attenuated EAE in all animals. Injection of OX54 acted moderately suppressive while OX55 or OX54/55 did not affect disease severity. Abrogation of EAE by OX34 was not restricted to its application before immunization. Therapeutic administration of all three mAb and the Ab combination from onset of first clinical signs efficiently blocked progression of disease and prevented all animals from developing hind limb paresis. In adoptive transfer EAE induced with in vitro activated cells of an encephalitogenic T helper line, clinical and histological signs were completely prevented by injection of OX34 on the day of cell transfer and 4 days later, underlining the strong impact of anti-CD2 mAb on the effector phase of disease. Immunocytofluorometric analysis of peripheral blood lymphocytes after a single Ab injection demonstrated that all mAb induced a variable degree of transient reduction in T cell numbers and modulation of CD2 antigens. In contrast to the other mAb, OX34 persisted on lymphocytes for at least 11 days, which may explain its unique suppressive effect on EAE after a single injection before immunization. The assumption that prophylactic administration of OX34 also inhibits MBP-induced EAE, due to persistence into the effector phase, was substantiated by the finding that none of the mAb prevented generation of an antigen-specific cellular response in MBP/CFA-immunized animals. Since none of the Ab induced T cell unresponsiveness or inhibited T cell activation by antigen- or Ab-mediated stimulation of the T cell receptor, we suggest that their marked action on the effector phase of EAE may rely on inhibition of T cell infiltration into the central nervous system. The demonstrated efficacy of these anti-CD2 mAb in EAE suggests a potential therapeutic role that may be equal to that of anti-CD4 or anti-T cell receptor Ab.

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.

TCR V gene usage in autoimmunity

With the use of polymerase chain reaction technology, investigators now have the ability to assess, in a comprehensive and rapid manner, the entire repertoire of T cell antigen receptors expressed by pathogenic cells present in virtually any disease site. A summary of studies of T cell receptor variable gene usage suggests that preferential expression can be identified most reproducibly when cells are isolated directly from pathogenic lesions. This provides a framework for future investigations in other autoimmune settings.

Myelin basic protein peptide specificity and T-cell receptor gene usage of HPRT mutant T-cell clones in patients with multiple sclerosis

Characterization of T cells responding to autoantigens is central to understanding autoimmune disease. We have used somatic mutation at the hypoxanthine guanine phosphoribosyltransferase (HPRT) gene as an index of T-cell amplification in vivo. With this strategy we previously showed that myelin basic protein-reactive T cells can be isolated only from the HPRT mutant T-cell population cultured from the peripheral blood of multiple sclerosis patients and not from normal individuals. In this study, 165 HPRT mutant and 104 wild-type clones were examined for their reactivity to myelin basic protein and overlapping peptides of myelin basic protein. Five HPRT mutant clones that recognized myelin basic protein and myelin basic protein peptides along with three clones that responded to myelin basic protein peptide alone were isolated. All but one of the eight clones recognized peptides derived from the carboxy terminus of myelin basic protein (p84-168). Sequence analysis showed heterogeneous expression of T-cell receptor V alpha and V beta genes and CDR3s. These studies showed that in vivo amplified autoimmune T cells from patients with long-standing disease use diverse T-cell receptor elements in the recognition of C-terminal myelin basic protein peptides.

Degeneracy of T cell receptor recognition of an influenza virus hemagglutinin epitope restricted by HLA-DQ and -DR class II molecules

DT9301-0229737 the TcR are believed to provide the peptide fragments bound to major histocompatibility (MHC) molecules. TcR have an immunoglobulin (Ig)-like structure and, in an analogous manner to antigen recognition by Ig, the third complementarity determining regions (CDR3) of the TcR are believed to provide the primary contact with the peptide lying in the MHC groove. CDR1 and CDR2 are thought to contact the presenting MHC molecule. We have analyzed seven human CD4+ T cell clones that recognize a conserved peptide epitope (residues 255-270) within the influenza virus hemagglutinin (H3) HA1 subunit. Two T cell clones recognized the peptide in the context of HLA-DRB1*1001 and HLA-DQB1*0602/DQA1*0102, respectively, and shared V alpha, V beta and J beta gene segments. Only the junctional regions encoding the CDR3 regions of the two TcR chains were different. This suggests that the CDR3 regions of these TcR interact with the MHC class II molecule. Six of the T cell clones were restricted by the HLA-DRB1*1001. Two of these T cell clones expressed V beta 9.1 and three expressed V beta 13 gene segments; the remaining clone expressed V beta 7.2, a close homologue of V beta 9.1. A diverse selection of V alpha and J gene segments contributed to the junctional heterogeneity of the TcR, indicating a diversity of sequence combinations recognizing the epitope. Nevertheless, five out of six T cell clones bore a motif in the V alpha CDR3 loop consisting of adjacent acidic and polar amino acid residues, eight residues from the carboxyl end of each CDR3.

Heterogeneity of T cells specific for a particular peptide/HLA-DQ complex

Whether T cells specific for a particular peptide/HLA-DQ complex are restricted with respect to TCR usage has not been fully established. TCR usage of T cells specific for a peptide presented by a given HLA-DQ molecule has not been studied before. We therefore sequenced the TCR genes of five different TCCs derived from the same donor, which were specific for a p21 ras-derived synthetic peptide presented by the HLA-DQ(alpha 1*0102,beta*0602) (DQ6) molecule. We found that these T cells which recognized the same peptide/HLA-DQ complex used highly diverse TCRs. However, dose-response experiments using various truncations of the p21 ras-derived peptide revealed that the peptide fine specificities of the five TCCs were not completely identical. This may explain the heterogeneity in TCR usage.

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.

Preferential distribution of V beta 8.2-positive T cells in the central nervous system of rats with myelin basic protein-induced autoimmune encephalomyelitis

To determine the role of encephalitogenic T cells in the formation of lesions in the central nervous system (CNS), experimental autoimmune encephalomyelitis (EAE) was induced in Lewis rats by immunization with either myelin basic protein (MBP) or the synthetic peptide which corresponds to the 87-100 sequence of guinea pig MBP, and T cells expressing T cell receptor (TcR) V beta 8.2, V beta 8.5, V beta 10 and V beta 16 in the lymphoid organs and CNS were localized and quantified by flow cytometry (FCM) and immunohistochemistry. In normal rats, the percentage of T cells expressing these V beta phenotypes to the total number of TcR alpha beta+ T cells, as determined by FCM, ranged from 5% to 10% in the lymph node. V beta 16+ T cells were the most predominant population among the four V beta subsets tested. Essentially the same findings were obtained from the analysis of the lymphoid organs of rats with EAE which had been induced by immunization with the same two antigens. In sharp contrast, 15-20% of the T cells isolated from lesions of MBP-induced EAE expressed V beta 8.2. Thus, the percentage of V beta 8.2+ T cells in the EAE lesions was threefold higher than that in the lymph node, while the proportions of V beta 8.5+, V beta 10+ and V beta 16+ T cells were about the same in both organs. The predominance of V beta 8.2+ T cells in EAE lesions was confirmed by counts of immunohistochemically stained T cells in the spinal cord. Moreover, it was revealed that (i) the predominance of V beta 8.2+ T cells was greatest during the development of EAE and became less obvious at the recovery state, and (ii) at the peak stage of EAE, approximately 85% of V beta 8.2+ T cells were distributed in the parenchyma while 15% were in the perivascular space of the CNS vessels. These findings indicate that encephalitogenic T cells which express V beta 8.2 infiltrate the CNS at a very early stage of EAE and become the predominant population in infiltrating T cells, and further suggest that encephalitogenic T cells, not only recruit inflammatory cells in the CNS, but also cause neural tissue damage, such as demyelination.

The T-cell response to myelin basic protein in familial multiple sclerosis: diversity of fine specificity, restricting elements, and T-cell receptor usage

Indirect evidence suggests that an autoimmune response to myelin basic protein (MBP) may be involved in the pathogenesis of multiple sclerosis (MS). In MS, several reports have suggested that restricted T-cell populations respond to MPB, as in inbred rodents with the MS disease model experimental allergic encephalomyelitis. In experimental allergic encephalomyelitis, the T-cell repertoire to MBP varies between strains, and in MS it is likely that the response to MBP is also best defined under conditions where genetic differences between subjects are controlled. In this report, the fine specificity of the T-cell response to MBP was assessed in three families, each with multiple individuals affected with MS. We found that (1) comparable frequencies of MBP-reactive T-cell lines were obtained from peripheral blood of MS patients and their healthy siblings. Human leukocyte antigen (HLA) identical sibling pairs discordant for MS had similar frequencies of MBP-reactive T-cell lines. (2) A broad spectrum of MBP epitopes was recognized by T-cell lines from all individuals studied. Within a family, the fine specificity of MBP recognition showed little or no overlap between individuals, even between HLA identical siblings. (3) Recognition of MBP epitopes occurred in the context of different HLA class II alleles. At least four DR alleles each served as restricting elements for recognition of P82-101 or the carboxy terminal region of MBP, two regions thought to be important in the human T-cell response to the molecule. No relationship between the use of a particular DR allele and a response to a particular region of MBP could be established.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigen-selected T-cell receptor diversity and self-nonself homology

Recent studies indicate that the T-cell receptor (TCR) repertoire selected by certain antigenic peptide-MHC combinations can be extremely diverse. This is in contrast to earlier studies reporting T-cell responses which were limited in terms of TCR diversity. In this viewpoint, we suggest these variations in TCR diversity may be explained by taking into account the homology between some antigens and self proteins to which T cells are tolerant.

Conservation of T cell receptor usage by HLA B27-restricted influenza-specific cytotoxic T lymphocytes suggests a general pattern for antigen-specific major histocompatibility complex class I-restricted responses

Eight HLA B27-restricted influenza A virus nucleoprotein 383-391-specific cytotoxic T lymphocyte (CTL) clones were obtained from three unrelated donors following natural infection. T cell receptor (TcR) usage was studied using the "anchored" polymerase chain reaction. TcR alpha-chain usage was restricted with three predominant V alpha (V alpha 12.1, 14.1, 22) and two predominant J alpha segments. beta-chain variable-region usage was also conserved, with V beta 7 being used by five clones despite contributing less than 2% of peripheral blood lymphocyte V beta sequences of one individual studied. The TcR beta-chain junctional region was highly conserved even between CTL clones from unrelated individuals, with a negatively charged amino acid, contributed to by N-region addition, encoded at position 97 in all but two clones. This study shows that peptide-specific HLA B27-restricted CTL following influenza virus infection use very similar TcR and, when considered with previous studies, suggests a pattern of TcR conservation for major histocompatibility complex class I-restricted responses. No difference in TcR usage was detected between one healthy donor and two with HLA B27-associated arthritis.

Restricted T cell receptor expression by human T cell clones specific for mycobacterial 65-kDa heat-shock protein: selective in vivo expansion of T cells bearing defined receptors

We have examined the T cell receptor (TcR) expression of clones specific for epitopes of mycobacterial 65-kDa heat-shock protein (hsp65) in the context of two different HLA molecules, and used this system as a model to assess the selection of T cells responsive to this antigen in vivo. DR3-restricted clones were raised from both the synovial fluid (SF) and peripheral blood (PB) of a patient with reactive arthritis in three separate cloning events. Five of five SF-derived clones tested expressed either V beta 5.2 or a closely related beta chain, V beta 5.6. The alpha chains expressed by V beta 5.2+ and V beta 5.6+ clones were from different families, V alpha 2.4 and V alpha 23.2, respectively. Nine of ten clones derived from two cloning procedures on PB taken 3 years later also expressed either V beta 5.2 or V beta 5.6. This suggests that the TcR repertoire for recognizing this major histocompatibility complex/peptide complex is relatively restricted and favors the use of V beta 5. Conservation of the beta chain third complementarity-determining region (CDR3) sequence was not evident, however. Sequencing alpha and beta chains of representative V beta 5.2+ and V beta 5.6+ PB-derived clones revealed TcR which were identical to those utilized by the SF-derived clones, showing that the repertoire for recognition of this antigen is stable over time. Similar studies of TcR expression were carried out on hsp65-specific, DP4-restricted clones derived from the SF of a patient with rheumatoid arthritis by two independent cloning procedures. There was conservation of alpha chain usage, since all clones expressed a member of the V alpha 1 family, but again CDR3 sequence conservation was not apparent. beta chain usage was not restricted since different clones expressed V beta 6.7, V beta 22.3 and V beta 12. Subtle differences in epitope specificity were detected for two clones with differing TcR. Once more, T cell clones with identical alpha and beta TcR chains were obtained from the separate cloning procedures, suggesting oligoclonalty of T cells with this defined specificity in the patient's SF.