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

Antibodies to influenza nucleoprotein cross-react with human hypocretin receptor 2

The sleep disorder narcolepsy is linked to the HLA-DQB1*0602 haplotype and dysregulation of the hypocretin ligand-hypocretin receptor pathway. Narcolepsy was associated with Pandemrix vaccination (an adjuvanted, influenza pandemic vaccine) and also with infection by influenza virus during the 2009 A(H1N1) influenza pandemic. In contrast, very few cases were reported after Focetria vaccination (a differently manufactured adjuvanted influenza pandemic vaccine). We hypothesized that differences between these vaccines (which are derived from inactivated influenza viral proteins) explain the association of narcolepsy with Pandemrix-vaccinated subjects. A mimic peptide was identified from a surface-exposed region of influenza nucleoprotein A that shared protein residues in common with a fragment of the first extracellular domain of hypocretin receptor 2. A significant proportion of sera from HLA-DQB1*0602 haplotype-positive narcoleptic Finnish patients with a history of Pandemrix vaccination (vaccine-associated narcolepsy) contained antibodies to hypocretin receptor 2 compared to sera from nonnarcoleptic individuals with either 2009 A(H1N1) pandemic influenza infection or history of Focetria vaccination. Antibodies from vaccine-associated narcolepsy sera cross-reacted with both influenza nucleoprotein and hypocretin receptor 2, which was demonstrated by competitive binding using 21-mer peptide (containing the identified nucleoprotein mimic) and 55-mer recombinant peptide (first extracellular domain of hypocretin receptor 2) on cell lines expressing human hypocretin receptor 2. Mass spectrometry indicated that relative to Pandemrix, Focetria contained 72.7% less influenza nucleoprotein. In accord, no durable antibody responses to nucleoprotein were detected in sera from Focetria-vaccinated nonnarcoleptic subjects. Thus, differences in vaccine nucleoprotein content and respective immune response may explain the narcolepsy association with Pandemrix.

Lymphocytes in neuroprotection, cognition and emotion: is intolerance really the answer?

Clinical, epidemiological and therapeutic studies indicate that some human depression is associated with proinflammatory cytokines, chronic inflammatory disorders, and inflammation-inducing lifestyle factors. Moreover depression can be induced by administration of proinflammatory cytokines, including IL-2 or IFN-α. However, recent studies in specific pathogen-free (SPF) rodents suggest a different--and potentially contradictory--relationship between immune processes and mental health. These studies suggest that effector T cells specific for central nervous system (CNS) antigens can assist recovery from an array of environmental insults ranging from nerve injury to psychological stress, while in contrast, regulatory T cells (Treg) oppose such recovery. Indeed, some reported effects of this so-called "protective autoimmunity" seem of direct relevance to depressive disorders. These findings pose a dilemma for those intending to manipulate inflammatory pathways as a treatment for depression. Should we administer anti-inflammatory treatments, or should we induce self-reactive T cells? We re-examine the rodent findings and outline immunological peculiarities of SPF rodents, the abnormal properties of their regulatory T cells, and the impact of gut microbiota. We find that "protective autoimmunity" is likely to be relevant only to very clean SPF animals that lack normal levels of activated T cells, CNS T cell traffic and mature Treg. The data indicate that even in SPF models the effectors of beneficial effects are not the proinflammatory autoimmune cells themselves, but rather unidentified regulatory cells. This reinterpretation of findings relevant to "protective autoimmunity" suggests that ongoing, and planned, clinical trials of anti-inflammatory strategies to treat depressive disorders are justified.

Immunodominance in the TCR repertoire of a [corrected] TCR peptide-specific CD4+ Treg population that controls experimental autoimmune encephalomyelitis

Immunodominance in self-Ag-reactive pathogenic CD4(+) T cells has been well established in several experimental models. Although it is clear that regulatory lymphocytes (Treg) play a crucial role in the control of autoreactive cells, it is still not clear whether immunodominant CD4(+) Treg clones are also involved in control of autoreactivity. We have shown that TCR-peptide-reactive CD4(+) and CD8(+) Treg play an important role in the spontaneous recovery and resistance from reinduction of experimental autoimmune encephalomyelitis in B10.PL mice. We report, by sequencing of the TCR alpha- and beta-chain associated with CD4(+) Treg, that the TCR repertoire is limited and the majority of CD4(+) Treg use the TCR Vbeta14 and Valpha4 gene segments. Interestingly, sequencing and spectratyping data of cloned and polyclonal Treg populations revealed that a dominant public CD4(+) Treg clonotype expressing Vbeta14-Jbeta1.2 with a CDR3 length of 7 aa exists in the naive peripheral repertoire and is expanded during the course of recovery from experimental autoimmune encephalomyelitis. Furthermore, a higher frequency of CD4(+) Treg clones in the naive repertoire correlates with less severity and more rapid spontaneous recovery from disease in parental B10.PL or PL/J and (B10.PL x PL/J)F(1) mice. These findings suggest that unlike the Ag-nonspecific, diverse TCR repertoire among the CD25(+)CD4(+) Treg population, TCR-peptide-reactive CD4(+) Treg involved in negative feedback regulation of autoimmunity use a highly limited TCR V-gene repertoire. Thus, a selective set of immunodominant Treg as well as pathogenic T cell clones can be targeted for potential intervention in autoimmune disease conditions.

Isolation and characterization of CD8+ regulatory T cells in multiple sclerosis

To investigate CD8+ regulatory T cell influence on multiple sclerosis development, peripheral blood and cerebrospinal fluid (CSF) CD8+ T cell clones (TCCs) recognizing MBP(83-102) and MOG(63-87)-specific CD4+ T cells were isolated from 20 patients during acute exacerbations, 15 in remission and 15 controls. Blood and CSF CD8+ regulatory TCC cloning frequency decreased more during exacerbations than remissions or controls. Target cell pre-activation significantly enhanced CD8+ T granule-mediated cell killing of CD4+ targets, and was restricted by HLA-E. During exacerbations, killer-inhibitory receptor CD94/NKG2A expression was significantly higher in CD8+ TCCs, limiting their cytotoxic activity. Moreover, IL-15 and IFN-gamma significantly increased CD94 and NKG2A expression. These data provide evidence that CD94/NKG2A receptors play an important role in regulating T cell activity during the course of MS.

[Update on pathophysiologic and immunotherapeutic approaches for the treatment of multiple sclerosis]

Multiple sclerosis (MS) is a chronic disabling disease with significant implications for patients and society. The individual disease course is difficult to predict due to the heterogeneity of clinical presentation and of radiologic and pathologic findings. Although its etiology still remains unknown, the last decade has brought considerable understanding of the underlying pathophysiology of MS. In addition to its acceptance as a prototypic inflammatory autoimmune disorder, recent data reveal the importance of primary and secondary neurodegenerative mechanisms such as oligodendrocyte death, axonal loss, and ion channel dysfunction. The deepened understanding of its immunopathogenesis and the limited effectiveness of currently approved disease-modifying therapies have led to a tremendous number of trials investigating potential new drugs. Emerging treatments take into account the different immunopathological mechanisms and strategies, to protect against axonal damage and promote remyelination. This review provides a compilation of novel immunotherapeutic strategies and recently uncovered aspects of known immunotherapeutic agents. The pathogenetic rationale of these novel drugs for the treatment of MS and accompanying preclinical and clinical data are highlighted.

Recombinant idiotypic TCRβ chain immunization in mice generates antigen specific T cell response

Vaccination remains the most cost-effective means of preventing infectious diseases. Success of vaccination depends on generation of effective memory response. Understanding the mechanism of generation and maintenance of immunological memory would help in the design of rational vaccines. T lymphocytes play a central role in the generation of protective immune response against many microbial infections. A hypothesis known as relay hypothesis was earlier proposed, which explains the maintenance of immunological memory through interaction of idiotypic and anti-idiotypic lymphocytes. In the present study, we have shown that immunization with a model antigen, chicken ovalbumin specific T cell receptor beta chain (idiotypic TCR) generates TCR specific antibody and anti-idiotypic T cell responses as well as ovalbumin specific T cell response. We further show that boosting of ovalbumin primed mice with ovalbumin specific idiotypic TCRbeta DNA or TCRbeta protein gives memory response for ovalbumin. This study provides experimental evidence for perpetuation of immunological memory through idiotypic network interactions.

Idiotypic T cells specific for Morbillivirus nucleocapsid protein process and present their TCR to cognate anti-idiotypic CD8+ T cells

CD8(+) T cells are activated by the presentation of antigenic peptide through MHC class I molecules. Newly synthesized proteins formed as defective ribosomal products (DRiPs) can act as a major source of antigenic peptides for MHC class I presentation pathway. Majority of these peptides are generated from the intracellular degradation of self antigens. In the present study, we have shown that newly synthesized T cell receptor (TCR) beta chains formed as DRiPs in T cells are ubiquitinated and degraded by the proteasomes. These TCR-DRiPs are processed and presented by activated T cells to cognate anti-idiotypic CD8(+) T cells. Presentation of TCR idiopeptide (peptide derived from the variable region of idiotypic TCR) by activated T cells leads to Bcl-2 expression and cytokine secretion by anti-idiotypic CD8(+) T cells. Presentation of intracellular antigen by T cells may have important implications in immunoregulation, control of lymphotropic virus infection and autoimmune diseases.

Homeostatic control of immunity by TCR peptide-specific Tregs

Regulation of the immune response is a multifaceted process involving lymphocytes that function to maintain both self tolerance as well as homeostasis following productive immunity against microbes. There are 2 broad categories of Tregs that function in different immunological settings depending upon the context of antigen exposure and the nature of the inflammatory response. During massive inflammatory conditions such as microbial exposure in the gut or tissue transplantation, regulatory CD4+CD25+ Tregs broadly suppress priming and/or expansion of polyclonal autoreactive responses nonspecifically. In other immune settings where initially a limited repertoire of antigen-reactive T cells is activated and expanded, TCR-specific negative feedback mechanisms are able to achieve a fine homeostatic balance. Here I will describe experimental evidence for the existence of a Treg population specific for determinants that are derived from the TCR and are expressed by expanding myelin basic protein-reactive T cells mediating experimental autoimmune encephalomyelitis, an animal prototype for multiple sclerosis. These mechanisms ensure induction of effective but appropriately limited responses against foreign antigens while preventing autoreactivity from inflicting escalating damage. In contrast to CD25+ Tregs, which are most efficient at suppressing priming or activation, these specific Tregs are most efficient in controlling T cells following their activation.

Autoimmune concepts of multiple sclerosis as a basis for selective immunotherapy: from pipe dreams to (therapeutic) pipelines

Autoimmune T and B cell responses to CNS antigen(s) are thought to drive the pathogenesis of multiple sclerosis (MS), and thus are logical targets for therapy. Indeed, several immunomodulatory agents, including IFN-beta 1b, IFN-beta 1a, glatiramer acetate, and mitoxantrone, have had beneficial clinical effects in different forms of MS. However, because the available treatments are only partially effective, MS therapy needs to be further improved. Selective (antigen-specific) immunotherapies are especially appealing because in theory they combine maximal efficacy with minimal side effects. Indeed, several innovative immunotherapies have been successfully applied in experimental autoimmune encephalomyelitis. For example, autoreactive T cells can be selectively targeted by means of antigen, T cell receptor, or activation markers. However, experimental autoimmune encephalomyelitis is far from being a perfect approximation of MS because MS is more heterogeneous and the target antigen(s) is (are) not known. Further advances in MS therapy will depend on our growing understanding of the pathogenesis of this still incurable disease.

Anti-T-cell humoral and cellular responses in healthy BALB/c mice following immunization with ovalbumin or ovalbumin-specific T cells

It is known that T-cell vaccination (TCV) elicits cellular immune responses against the immunizing T cells in vivo. However, it is still unclear whether similar anti-T-cell responses are also induced in individuals responding to foreign antigen (Ag) challenge. This study was undertaken to characterize and compare anti-T-cell cellular and humoral responses of BALB/c mice after ovalbumin (OVA) immunization or TCV. Splenocytes from OVA-primed BALB/c mice proliferated in response to stimulation with a syngeneic OVA-specific T-cell clone, OVA-T3, and secreted interferon-gamma (IFN-gamma) but not interleukin-4 (IL-4). Cytotoxic T-lymphocyte (CTL) activity against the T-cell clone was also observed. Serum samples from these animals discriminated between activated and resting murine T cells, as determined by indirect immunofluorescence staining. Vaccination of BALB/c mice with OVA-T3 cells induced similar, but stronger, cellular and humoral responses. TCV-induced antibodies were not only able to distinguish between activated and resting syngeneic T cells but also positively stained allogeneic T cells from BXSB mice. Furthermore, TCV resulted in hyporesponsiveness of BALB/c mice to subsequent Ag challenge, and antisera from the immunized animals inhibited T-cell proliferation in vitro. Our data suggest that anti-T-cell antibodies, and CD4+ and CD8+ regulatory T lymphocytes may form a complex and co-ordinated regulatory network that plays an important role in regulating the adaptive immune responses in vivo. Implications of this observation for our understanding of the immunoregulation and peripheral tolerance are discussed.

Diminished frequency of interleukin-10-secreting, T-cell receptor peptide-reactive T cells in multiple sclerosis patients might allow expansion of activated memory T cells bearing the cognate BV gene

T cells responsive to T-cell receptor (TCR) determinants may regulate pathogenic Th1 responses in patients with multiple sclerosis (MS) through interleukin (IL)-10-dependent bystander suppression. In this study, innate IL-10- and interferon (IFN)-gamma-secreting T cells responsive to TCR peptides were quantified in peripheral blood mononuclear cells of MS patients and healthy controls (HC) using the ELISPOT assay. Most HC had vigorous IL-10 but low IFN-gamma frequencies to BV5S2 and BV6S1 peptides. In contrast, MS patients had significantly lower IL-10 frequency responses to the TCR peptides but normal responses to concanavalin A. Patients undergoing TCR-peptide vaccination had moderate responses that fluctuated in concert with vaccination. In an MS patient and HC, expression of BV6S1 by activated memory T cells was inversely associated with the presence of IL-10-secreting BV6S1-reactive T cells. These results suggest that MS patients have diminished frequencies of innate TCR-reactive T cells that may allow oligoclonal expansion of activated autoreactive Th1 effector cells expressing cognate V genes.

TCR peptide therapy in human autoimmune diseases

Inflammatory Th1 cells reacting to tissue/myelin derived antigens likely contribute to the pathogenesis of diseases such as multiple sclerosis (MS), rheumatoid arthritis (RA), and psoriasis. One regulatory mechanism that may be useful for treating autoimmune diseases involves an innate second set of Th2 cells specific for portions of the T cell receptor of clonally expanded pathogenic Th1 cells. These Th2 cells are programmed to respond to internally modified V region peptides from the T cell receptor (TCR) that are expressed on the Th1 cell surface in association with major histocompatibility molecules. Once the regulatory Th2 cells are specifically activated, they may inhibit inflammatory Th1 cells through a non-specific bystander mechanism. A variety of strategies have been used by us to identify candidate disease-associated TCR V genes present on pathogenic Th1 cells, including BV5S2, BV6S5, and BV13SI in MS, BV3, BV14, and BV17 in RA, and BV3 and BV13S1 in psoriasis. TCR peptides corresponding to the mid region of these BV genes were found to be consistently immunogenic in vivo when administered either i.d. in saline or i.m. in incomplete Freund's adjuvant (IFA). In MS patients, repeated injection of low doses of peptides (100-300 microg) significantly boosted the number of TCR-reactive Th2 cells. These activated cells secreted cytokines, including IL-10, that are known to inhibit inflammatory Th1 cells. Cytokine release could also be induced in TCR-reactive Th2 cells by direct cell-cell contact with Th1 cells expressing the target V gene. These findings indicate the potential of regulatory Th2 cells to inhibit not only the target Th1 cells, but also bystander Th1 cells expressing different V genes specific for other autoantigens. TCR peptide vaccines have been used in our studies to treat a total of 171 MS patients (6 trials), 484 RA patients (7 trials), and 177 psoriasis patients (2 trials). Based on this experience in 824 patients with autoimmune diseases, TCR peptide vaccination is safe and well tolerated, and can produce significant clinical improvement in a subset of patients that respond to immunization. TCR peptide vaccination represents a promising approach that is well-suited for treating complex autoimmune diseases.

Reactivity and regulatory properties of human anti-idiotypic antibodies induced by T cell vaccination

Immunization with irradiated autoreactive T cells (T cell vaccination) induces anti-idiotypic T cell responses that preferentially recognize complementarity-determining region 3 sequences, contributing to clonal depletion of autoreactive T cells. However, it remains unknown whether T cell vaccination elicits anti-idiotypic humoral responses and whether the anti-idiotypic Abs play a similar role in the regulatory mechanism induced by T cell vaccination. In this study we examined the occurrence, the reactivity pattern, and the regulatory role of anti-idiotypic Abs elicited by T cell vaccination in patients with multiple sclerosis. We demonstrated for the first time that B cells producing anti-idiotypic Abs could be isolated from vaccinated patients. These EBV-transformed B cell lines were selected for specific reactivity to a 20-mer TCR peptide incorporating a common complementarity-determining region 3 sequence of the immunizing T cell clones. The resulting anti-idiotypic Abs were found to react with the original immunizing T cell clones and exhibit an inhibitory effect on their proliferation. The findings suggest that anti-idiotypic Ab responses can be induced by T cell vaccination in humans and that their regulatory properties are likely to contribute to the suppression of myelin basic protein-reactive T cells in vaccinated patients. The study has important implications in our understanding of the regulatory role of the anti-idiotypic humoral responses induced by T cell vaccination.

Preferential recognition of TCR hypervariable regions by human anti-idiotypic T cells induced by T cell vaccination

T cell responses to myelin basic protein (MBP) are potentially involved in the pathogenesis of multiple sclerosis (MS). Immunization with irradiated MBP-reactive T cells (T cell vaccination) induces anti-idiotypic T cell responses that suppress circulating MBP-reactive T cells. This T cell-T cell interaction is thought to involve the recognition of TCR expressed on target T cells. The study was undertaken to define the idiotypic determinants responsible for triggering CD8+ cytotoxic anti-idiotypic T cell responses by T cell vaccination in patients with MS. A panel of 9-mer synthetic TCR peptides corresponding to complementarity-determining region 2 (CDR2) and CDR3 of the immunizing MBP-reactive T cell clones were used to isolate anti-idiotypic T cell lines from immunized MS patients. The resulting TCR-specific T cell lines expressed exclusively the CD8 phenotype and recognized preferentially the CDR3 peptides. CDR3-specific T cell lines were found to lyze specifically autologous immunizing MBP-reactive T cell clones. The findings suggest that CDR3-specific T cells represented anti-idiotypic T cell population induced by T cell vaccination. In contrast, the CDR2 peptides were less immunogenic and contained cryptic determinants as the CDR2-specific T cell lines did not recognize autologous immunizing T cell clones from which the peptide sequence was derived. The study has important implications in our understanding of in vivo idiotypic regulation of autoimmune T cells and the regulatory mechanism underlying T cell vaccination.

Expression of Multiple Unique Rejection Antigens on Murine Leukemia BALB/c RL♂1 and the Role of Dominant Akt Antigen for Tumor Escape

Using the pRL1a Ag-loss RL♂1 tumor variant cell line RM2-1, we demonstrated the presence of tumor Ags other than pRL1a that were recognized by CTLs on RL♂1 cells. Semiallogeneic CB6F1 or syngeneic BALB/c CTLs generated against RM2-1 lysed RM2-1 and RL♂1 cells to a similar extent, but no killing was observed with any other tumor or normal cells examined. Clonal analysis and sensitization with reversed phase-HPLC fractions revealed that there were Dd- and Ld-binding peptides recognized by RM2-1 CTLs. Lysis by bulk CTLs stimulated against RL♂1 and limiting dilution analysis suggested that the pRL1a peptide was dominantly recognized to the RM2-1 peptides by CTLs on RL♂1 cells. The rejection response against the parental RL♂1 tumor was much less than that against RM2-1 cells in either CB6F1 or BALB/c mice, suggesting that the presence of altered Akt molecules from which the dominant pRL1a peptide was derived inhibited the rejection response against RL♂1. Depletion of CD4 T cells caused the regression of RL♂1 at the doses in which the tumor grew in untreated mice. The generation of pRL1a CTLs was inhibited in RL♂1-bearing mice. Thus, immunoregulatory CD4 T cells were most likely activated by the altered Akt molecules and inhibited the efficient generation of CTLs against the dominant pRL1a Ag in RL♂1.

Granule associated DNase in T4 and T8 lymphocytes from patients with autoimmune diseases

The presence of a DNase activity associated with secretion granules was detected in T4 and T8 lymphocytes from patients with autoimmune diseases. This activity was much higher in primary biliary cirrhosis (PBC) than in Graves' disease (GD) and multiple sclerosis (MS) or in healthy subjects. This granule associated DNase activity was Ca(2+)-dependent, inhibited by Zn2+, and higher at low pH; its molecular weight corresponded to 66kDa; it was more active with double-strand than single-strand DNA. Judging from its properties this enzyme differed from the three types of endonucleases described as involved in DNA fragmentation (DNase I, DNase II and NUC18). Flow cytometry analysis of T lymphocytes showed that DNase activity associated with CD4+ lymphocyte granules correlated with the ratio CD4+CD45RO+/CD4+CD45RA+ (memory and cytotoxic cells/naive cells, inducers of suppression). In contrast, T8 lymphocyte DNase activity correlated with the proportion of CD4+ lymphocytes with CD4+CD45RA- phenotype (helpers and inducers of cytotoxicity). The possible role of this DNase activity in the mechanisms of lysis or apoptosis mediated by CTL is discussed. We suggest that this DNase activity could be implicated in some of the alterations of the autoimmune response depending on cytotoxic T lymphocytes or T cell inducers of apoptosis.

Acquired resistance to experimental autoimmune encephalomyelitis is independent of V beta usage

In Lewis rats, activated encephalitogenic T-helper cells elicit a single bout of experimental autoimmune encephalomyelitis (EAE). Recovery from EAE is marked by reduced susceptibility to disease reinduction. The purpose of this study was to determine whether a dominant expression of V beta gene segments by encephalitogenic T cells was required for development of recovery-associated resistance. Several polyclonal and monoclonal T cell lines were derived from Lewis rats sensitized with R72-86, a synthetic peptide representing the 72- to 86-amino-acid sequence of rat myelin basic protein (RMBP). The results revealed broad heterogeneity among encephalitogenic T cells specific for R72-86 in regard to V beta expression and CDR3 sequence. Encephalitogenic clones exclusively bearing either V beta 4 or V beta 10 TCR or polyclonal T cells bearing heterogeneous TCR transferred EAE to recipient rats and elicited resistance to EAE as revealed by subsequent challenge with guinea pig (GP)MBP in complete Freund's adjuvant (CFA). Nonpathogenic V beta 3+ and V beta 8.6+ clones specific for the 68-86 and 55-66 regions of MBP, respectively, did not elicit effective protection from EAE. These data indicate that induction of postrecovery resistance to EAE does not depend upon a particular V beta usage.

T cell vaccination in multiple sclerosis

T cell responses to myelin basic protein (MBP) are implicated to play an important role in the pathogenesis of multiple sclerosis (MS). These MBP autoreactive T cells are found to undergo in vivo activation and clonal expansion in patients with MS. They accumulate in the brain compartment and may reside in the brain lesions of patients with MS. As MBP-reactive T cells potentially hold a central position in initiation and perpetuation of the brain inflammation, specific immune therapies designed to deplete them may improve the clinical course of the disease. In this paper, the therapeutic potential of T cell vaccination in the treatment of MS is discussed in context of its immunological and clinical effect. The results of our phase one clinical trial indicate that T cell vaccination with inactivated MBP autoreactive T cells induces specific regulatory T cell network of the host immune system to deplete circulating MBP-reactive T cells in a clonotype-specific fashion. The immunity induced by T cell vaccination is clonotype-specific and long-lasting. Our longitudinal clinical evaluation further suggests a moderate reduction of rate of clinical exacerbation, disability score and the brain lesions (measured by magnetic resonance imaging) in vaccinated patients, as compared to matched controls. Our study should encourage further investigation on the treatment efficacy of T cell vaccination and further improvement for its clinical application.

IL-10 is necessary and sufficient for autoimmune diabetes in conjunction with NOD MHC homozygosity

Contrary to expectations based on in vitro experiments, we previously found that pancreatic IL-10 did not inhibit autoimmune diabetes but accelerated it in an MHC-dependent manner. Therefore, the ability of IL-10 to overcome the absence of all non-MHC diabetes susceptibility (Idd) alleles was studied in transgenic mice expressing pancreatic IL-10 backcrossed to B10.H2g7 congenic mice, which have no Idd alleles other than NOD MHC (H2g7). IL-10 transgenic backcross 1 (BC1) mice with H2g7/g7 haplotype developed clear-cut insulitis and diabetes, but neither transgenic mice with the H2g/b haplotype nor nontransgenic BC1 mice did so. Further implicating IL-10 in autoimmune diabetes, anti-IL-10 antibody treatment inhibited the development of insulitis in NOD mice. These results suggest that IL-10 may be necessary and sufficient for producing autoimmune diabetes in conjunction with NOD MHC homozygosity and that some Idd genes may be related to the regulation of IL-10.

Syngeneic bone marrow transplantation eliminates V beta 8.2 T lymphocytes from the spinal cord of Lewis rats with experimental allergic encephalomyelitis

Experimental allergic encephalomyelitis (EAE), an animal model for multiple sclerosis (MS), is a paralytic disease of the central nervous system (CNS) mediated by T-lymphocytes reactive to myelin basic protein (MBP). Lewis rats actively immunized with fragment 68 to 82 of guinea pig MBP develop a monophasic disease with spontaneous recovery. Lymphocyte recognition of the primary encephalitogenic sequence of MBP (fragment 68 to 82) is V beta 8.2 T cell receptor (TCR) skewed [1-3]. Lewis rats in clinical remission at 1 month and 3 months after spontaneous resolution of EAE retain V beta 8.2 T-lymphocytes in the CNS when analyzed by reverse transcriptase polymerase chain reaction or in situ hybridization. In contrast, 1 and 3 months after clinical remission from syngeneic bone marrow transplantation, V beta 8.2 T lymphocytes are absent from the CNS. During clinically active EAE and inflammatory breakdown of the blood-brain barrier, immune ablation and reconstitution with syngeneic bone marrow results in clinical tolerance of the new immune system to myelin.

T cells as antigen-presenting cells

Human T cells express major histocompatibility complex (MHC) class II antigens and adhesion molecules characteristic of antigen-presenting cells (APCs), and recent in vitro and in vivo evidence supports an antigen-presenting function for T cells. In this guise, T cells provide downregulatory signals for the immune response by inducing anergy in T cells that have already been activated and cytotoxicity in resting T cells. Here, Werner Pichler and Tony Wyss-Coray suggest that this may represent an important negative mechanism for T-cell homeostasis.

CDR1 T-cell receptor beta-chain peptide induces major histocompatibility complex class II-restricted T-T cell interactions

T-T cell interactions have been proposed in postulated network theories of immunoregulation and autoimmunity. Despite previous reports of protection induced by T-cell receptor (TcR)-derived peptides in experimental autoimmunity, no evidence for T-T cell interactions by direct recognition of processed TcRs on native T cells was obtained. Here we report that immunization of rats with overlapping sets of peptides of the TcR alpha or beta chain allowed us to detect immunogenic TcR peptides. Remarkably enough, these TcR peptides appeared to cluster within the hypervariable complementarity-determining regions of the TcR. Immunization of rats with these TcR peptides induced CD4+ TcR peptide-specific T cells, which recognized both rDNA TcR proteins and the original, arthritogenic T cell in a major histocompatibility complex class II-restricted way. These findings indicate that activated T cells can process and present their own TcR in the context of major histocompatibility complex class II molecules and, furthermore, that such peptides can be recognized by TcR variable gene-specific T cells.

Vaccination with T cell receptor peptides primes anti-receptor cytotoxic T lymphocytes (CTL) and anergizes T cells specifically recognized by these CTL

We selected three peptides from the germ-line sequence of the V beta 8.2 and J beta 2.3 gene segments of the murine T cell receptor for antigen (TCR) which contained putative Kd- and Ld-restricted epitopes. Immunization of BALB/c (H-2d) mice with the V beta 8.2(67-90) 23-mer peptide 1 as well as the 15-mer V beta 8.2(95-108)-peptide 2 efficiently primed specific CD8+ cytotoxic T lymphocyte (CTL) responses in vivo against natural TCR-V beta 8.2 epitopes. V beta 8.2+ T cells were not deleted in TCR peptide-immunized mice because the fractions of V beta 8.2+ CD4+ and V beta 8.2+ CD8+ T cells in spleen and lymph nodes were not altered. The proliferative response of V beta 8.2+ T cells to stimulation by monoclonal antibody F23.2 was selectively suppressed (by 60-80%) in peptide-immunized BALB/c mice, indicating partial anergy of this T subset. Immunization of BALB/c mice with the J beta 2.3-derived peptide 3 stimulated a CD8+ CTL response against a class I-restricted epitope within this J beta segment that was also generated during natural "endogenous" processing of this self antigen. These data confirm the predictive value of major histocompatibility complex class I allele-specific motifs. The described experiments indicate that TCR peptide-primed CD8+ CTL recognize class I-restricted, natural V beta/J beta-TCR epitopes. Such anti-TCR CTL may, thus, operate in V beta-specific immunoregulation of the T cell system suppressing their functional reactivity without deleting them.

Transformation of human T-cell clones by Herpesvirus saimiri: intact antigen recognition by autonomously growing myelin basic protein-specific T cells

Herpesvirus saimiri has recently been shown to immortalize human T cells. It was unknown, however, whether Herpesvirus saimiri transformation affects T-cell receptor (TCR) expression and signal transduction. In the present study, we have transformed CD4+ human T-cell clones specific for human myelin basic protein. The transformed T cells were grown in interleukin 2 and divided in the absence of antigen and antigen-presenting cells. They retained the membrane phenotype of activated T cells and secreted the cytokines interferon gamma and lymphotoxin, but interleukin 4 was not detected. Further, the transformed T cells continued to express the original TCR as demonstrated by TCR variable-region-V beta-specific monoclonal antibodies and TCR sequencing. Antigen-specific recognition and signal transduction by the TCR were demonstrated by myelin-basic-protein-induced HLA-DR-restricted secretion of interferon gamma and lymphotoxin and by myelin-basic-protein-specific proliferation. Antigen specificity and reactivity have been maintained for > 1 year after transformation. Transformation with Herpesvirus saimiri now allows the production of virtually unlimited numbers of (auto)antigen-specific T cells expressing functional TCR and a stable membrane phenotype. This technology will facilitate studies of the pathogenesis of putative autoimmune diseases, such as multiple sclerosis, and may be of help in TCR-targeted immunotherapy.

The human myelin basic protein gene is included within a 179-kilobase transcription unit: expression in the immune and central nervous systems

Two human Golli (for gene expressed in the oligodendrocyte lineage)-MBP (for myelin basic protein) cDNAs have been isolated from a human oligodendroglioma cell line. Analysis of these cDNAs has enabled us to determine the entire structure of the human Golli-MBP gene. The Golli-MBP gene, which encompasses the MBP transcription unit, is approximately 179 kb in length and consists of 10 exons, seven of which constitute the MBP gene. The human Golli-MBP gene contains two transcription start sites, each of which gives rise to a family of alternatively spliced transcripts. At least two Golli-MBP transcripts, containing the first three exons of the gene and one or more MBP exons, are produced from the first transcription start site. The second family of transcripts contains only MBP exons and produces the well-known MBPs. In humans, RNA blot analysis revealed that Golli-MBP transcripts were expressed in fetal thymus, spleen, and human B-cell and macrophage cell lines, as well as in fetal spinal cord. These findings clearly link the expression of exons encoding the autoimmunogen/encephalitogen MBP in the central nervous system to cells and tissues of the immune system through normal expression of the Golli-MBP gene. They also establish that this genetic locus, which includes the MBP gene, is conserved among species, providing further evidence that the MBP transcription unit is an integral part of the Golli transcription unit and suggest that this structural arrangement is important for the genetic function and/or regulation of these genes.