Interleukin 7 is a potent co-stimulator of myelin specific T cells that enhances the adoptive transfer of experimental autoimmune encephalomyelitis

Interleukin 7 (IL-7), originally described as a B cell growth factor, has recently been found to play a critical role in T and B lymphocyte development and function. This study evaluated the effects of IL-7 on myelin specific T cells. IL-7 strongly enhanced proliferation of proteolipid protein (PLP) 139-151 specific T cells in association with elevated secretion of the T cell growth factor IL-2. Co-stimulation with IL-7 preferentially increased the levels of pro-inflammatory cytokines secreted by PLP 139-151 specific T cells and adoptive transfer of these cells into naive recipients induced a profound enhancement of experimental autoimmune encephalomyelitis, an animal model for the human disease multiple sclerosis. These results suggest that IL-7 may be a critical co-stimulatory factor that enhances the extrathymic expansion of inflammatory T cells and may play an important role in the pathogenesis of a number of inflammatory autoimmune disorders.

Differential susceptibility of human T(h)1 versus T(h) 2 cells to induction of anergy and apoptosis by ECDI/antigen-coupled antigen-presenting cells

Antigen-coupled antigen-presenting cells (APC) serve as potent tolerogens for inhibiting immune responses in vivo and in vitro, apparently by providing an antigen-specific signal through the TCR in the absence of co-stimulation. Although this approach has been well studied in rodents, little is known about its effects on human T cells. We evaluated the specificity and mechanisms of tolerization of human T cells in vitro using monocyte-enriched adherent cells that were pulsed with antigen and treated with the cross-linker, 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (ECDI). Autologous antigen-coupled APC selectively tolerized T cells of the T(h)1 but not T(h)2 lineage through a mechanism that involved both antigen-specific and antigen-non-specific elements. The tolerization process was dependent on the ECDI and antigen concentration, and the coupling time, and was reflected by initial up-regulation of CD25. However, upon re-stimulation with fresh APC and antigen, tolerized T(h)1 cells failed to proliferate or to produce T(h)1 cytokine message or secreted protein, had decreased expression of CD25, CD28 and B7 and increased expression of MHC class II molecules, and demonstrated an enhanced commitment to apoptosis. T(h)1 cell tolerization could be prevented by adding anti-CD28 antibody, IL-2 or untreated APC at the same time as the ECDI/antigen-coupled APC, or reversed by adding anti-CD28 antibody or IL-2 upon re-stimulation with fresh APC plus antigen. Thus, the tolerizing effect of ECDI/antigen-coupled APC on human T(h)1 cells appears to involve a reversible anergy mechanism leading to apoptosis, whereby the targeted T cells receive full or partial activation through the TCR, without coordinate co-stimulation. These data suggest dichotomous signaling requirements for inactivating cells of the T(h)1 and T(h)2 lineages that may have important implications for treatment of T(h)1-mediated autoimmune or inflammatory diseases.

T cell receptor V genes in multiple sclerosis: increased use of TCRAV8 and TCRBV5 in MBP-specific clones

It is probable that myelin-reactive T cells, including those specific for myelin basic protein (MBP) contribute to the pathogenesis of multiple sclerosis (MS). Although many studies have characterized the specificity, MHC restriction, and V gene use of MBP-specific T cells, there is little agreement as to whether there are differences between MS and controls, and how HLA-DR2, a risk factor for MS, might influence selection of MBP-specific T cells. We here discuss models in which MHC class II alleles could help shape the TCR repertoire, and then review more than 750 clones reported in the literature. The major finding from our analysis is that both TCRAV8 and BV5, but not BV6 were utilized more frequently in MS patients than non-MS patients in response to MBP, although no differences were found between DR2+ versus DR2- donors. These data indicate HLA-independent differences in the T cell repertoire between MS patients and controls that may be important for targeted TCR-based therapy. Moreover, we conclude that (1) HLA-DR alleles preferentially restrict MBP responses, although MS patients tend to use HLA-DQ and -DP alleles more often than control donors; (2) HLA-DR2 alleles are used to restrict only about half the MBP responses in MS patients, significantly less than in control patients; (3) the DRB1*1501 and DRB5*0101 subtypes within the Dw2 haplotype are used relatively equally to restrict MBP responses. In this context, we review the results of our previous clinical trials in progressive MS patients, demonstrating the ability of TCRBV5S2 peptides to induce clinically relevant regulatory responses that inhibit MBP-specific Th1 cells through a bystander suppression mechanism.

Design, engineering and production of functional single-chain T cell receptor ligands

Major histocompatibility complex (MHC) class II molecules are membrane-anchored heterodimers on the surface of antigen presenting cells (APCs) that bind the T cell receptor, initiating a cascade of interactions that results in antigen-specific activation of clonal populations of T cells. The peptide binding/T cell recognition domains of rat MHC class II (alpha-1 and beta-1 domains) were expressed as a single exon for structural and functional characterization. These recombinant single-chain T cell receptor ligands (termed 'beta1alpha1' molecules) of approximately 200 amino acid residues were designed using the structural backbone of MHC class II molecules as template, and have been produced in Escherichia coli with and without N-terminal extensions containing antigenic peptides. Structural characterization using circular dichroism predicted that these molecules retained the antiparallel beta-sheet platform and antiparallel alpha-helices observed in the native MHC class II heterodimer. The proteins exhibited a cooperative two-state thermal folding-unfolding transition. Beta1alpha1 molecules with a covalently linked MBP-72-89 peptide showed increased stability to thermal unfolding relative to the empty beta1alpha1 molecules. This new class of small soluble polypeptide provides a template for designing and refining human homologues useful in detecting and regulating pathogenic T cells.

IL-7 enhances Ag-specific human T cell response by increasing expression of IL-2R alpha and gamma chains

Interleukin-7 has demonstrated potent enhancing effects on the growth and differentiation of several immature cell types, including thymocytes, and on survival of resting and antigen activated T cells. In this study, we evaluated the effects of IL-7 on post-thymic antigen-specific T cells from human blood. IL-7 was found to enhance proliferation responses and IFN-gamma secretion of myelin or recall Ag-specific Th1 cells through the selective up-regulation of the IL-2Ralpha and gamma but not beta chains in both an Ag-dependent and Ag-independent manner, but did not affect monocytes, B cells, or NK cells. These functions of IL-7 enhanced the detection of Th1 but not Th2 cell frequency by >2.5 fold, and promoted selection of Ag-specific Th1 cells by the limiting dilution method. Moreover, IL-7 pretreatment conferred increased resistance of CD4+ T cells to CD8+ cell lysis. These studies demonstrate that IL-7 promotes the growth and survival of circulating Ag-specific human Th1 cells through a mechanism that probably involves the gammac common receptor for IL-2 family members that includes IL-7.

Gender differences in protection from EAE induced by oral tolerance with a peptide analogue of MBP-Ac1-11

Mechanisms that contribute to increased female susceptibility to multiple sclerosis can be studied in the murine model of experimental autoimmune encephalomyelitis (EAE). In this report, we compared oral tolerance induction in male and female B10.PL mice using fed myelin basic protein (MBP) Ac1-11 peptide or a high-affinity analogue, Ac1-11[4Y]. We found that fed Ac1-11[4Y] peptide, but not native Ac1-11, could limit cellular infiltration into the central nervous system (CNS) and protect male mice from EAE, an effect that was completely obviated by castration. In contrast, female mice could not be orally tolerized or protected from EAE with either peptide. Tolerance induction in males was reflected by the appearance of Ac1-11[4Y]-reactive splenocytes that produced a sharply increased ratio of transforming growth factor (TGF)-beta:interleukin (IL)-2 and induced bystander suppression. These data directly demonstrate gender differences in regulatory T cells, and support the concept that androgens are involved in governing oral tolerance to EAE.

Androgens alter the cytokine profile and reduce encephalitogenicity of myelin-reactive T cells

Adoptive transfer of proteolipid protein 139-151-specific T cell lines was used to examine the role of androgens in regulating T cell cytokine secretion and the severity of experimental autoimmune encephalomyelitis (EAE) in the SJL mouse. In this study, we found that T cells from female mice transferred more severe EAE than T cells from male mice and that gender differences in clinical disease were due, at least in part, to differences in donor T cell cytokine secretion. T cell lines were selected from proteolipid protein 139-151-immunized female SJL mice in the presence or absence of exogenous androgens. Androgen-selected T cell lines secreted less IFN-gamma and more IL-10 than untreated cell lines. Clinical disease induced by the adoptive transfer of androgen-selected T cell lines was less severe than disease induced with untreated T cell lines. Furthermore, androgen treatment of naive TCR transgenic T cells, during their first encounter with Ag, resulted in a shift in the balance of Th1/Th2 cytokines. This phenotype was maintained during subsequent stimulations in the absence of androgen. These results suggest that androgen present in the lymphoid microenvironment during the induction of an immune response can alter the development of effector T cells and may play an important role in governing gender differences in the immune response and susceptibility to autoimmune disorders.

Androgens Alter the Cytokine Profile and Reduce Encephalitogenicity of Myelin-Reactive T Cells

Adoptive transfer of proteolipid protein 139–151-specific T cell lines was used to examine the role of androgens in regulating T cell cytokine secretion and the severity of experimental autoimmune encephalomyelitis (EAE) in the SJL mouse. In this study, we found that T cells from female mice transferred more severe EAE than T cells from male mice and that gender differences in clinical disease were due, at least in part, to differences in donor T cell cytokine secretion. T cell lines were selected from proteolipid protein 139–151-immunized female SJL mice in the presence or absence of exogenous androgens. Androgen-selected T cell lines secreted less IFN-γ and more IL-10 than untreated cell lines. Clinical disease induced by the adoptive transfer of androgen-selected T cell lines was less severe than disease induced with untreated T cell lines. Furthermore, androgen treatment of naive TCR transgenic T cells, during their first encounter with Ag, resulted in a shift in the balance of Th1/Th2 cytokines. This phenotype was maintained during subsequent stimulations in the absence of androgen. These results suggest that androgen present in the lymphoid microenvironment during the induction of an immune response can alter the development of effector T cells and may play an important role in governing gender differences in the immune response and susceptibility to autoimmune disorders.

Two-Domain MHC Class II Molecules Form Stable Complexes with Myelin Basic Protein 69–89 Peptide That Detect and Inhibit Rat Encephalitogenic T Cells and Treat Experimental Autoimmune Encephalomyelitis

We designed and expressed in bacteria a single-chain two-domain MHC class II molecule capable of binding and forming stable complexes with antigenic peptide. The prototype “β1α1” molecule included the β1 domain of the rat RT1.B class II molecule covalently linked to the amino terminus of the α1 domain. In association with the encephalitogenic myelin basic protein (MBP) 69–89 peptide recognized by Lewis rat T cells, the β1α1/MBP-69–89 complex specifically labeled and inhibited activation of MBP-69–89 reactive T cells in an IL-2-reversible manner. Moreover, this complex both suppressed and treated clinical signs of experimental autoimmune encephalomyelitis and inhibited delayed-type hypersensitivity reactions and lymphocyte proliferation in an Ag-specific manner. These data indicate that the β1α1/MBP-69–89 complex functions as a simplified natural TCR ligand with potent inhibitory activity that does not require additional signaling from the β2 and α2 domains. This new class of small soluble polypeptide may provide a template for designing human homologues useful in detecting and regulating potentially autopathogenic T cells.

Two-domain MHC class II molecules form stable complexes with myelin basic protein 69-89 peptide that detect and inhibit rat encephalitogenic T cells and treat experimental autoimmune encephalomyelitis

We designed and expressed in bacteria a single-chain two-domain MHC class II molecule capable of binding and forming stable complexes with antigenic peptide. The prototype "beta1alpha1" molecule included the beta1 domain of the rat RT1.B class II molecule covalently linked to the amino terminus of the alpha1 domain. In association with the encephalitogenic myelin basic protein (MBP) 69-89 peptide recognized by Lewis rat T cells, the beta1alpha1/MBP-69-89 complex specifically labeled and inhibited activation of MBP-69-89 reactive T cells in an IL-2-reversible manner. Moreover, this complex both suppressed and treated clinical signs of experimental autoimmune encephalomyelitis and inhibited delayed-type hypersensitivity reactions and lymphocyte proliferation in an Ag-specific manner. These data indicate that the beta1alpha1/MBP-69-89 complex functions as a simplified natural TCR ligand with potent inhibitory activity that does not require additional signaling from the beta2 and alpha2 domains. This new class of small soluble polypeptide may provide a template for designing human homologues useful in detecting and regulating potentially autopathogenic T cells.

Induction of T cell anergy by high concentrations of immunodominant native peptide is accompanied by IL-10 production and a block in JNK activity

The ability to induce anergy in antigen-specific T cells has potential therapeutic value for altering pathologic immune responses. This study was undertaken to further analyze changes in cytokine production and intracellular signaling during anergy induction using high concentrations of native peptide ligand of tetanus toxoid (TT)- and myelin basic protein (MBP)-specific human T cell lines. The TT-selected T cell line could be rendered unresponsive to its dominant epitope in a dose-dependent manner (IC50 = 0.03 microg/ml). The TT-selected line, as well as three T cell clones established from this line, continued to produce IFN-gamma and significantly increased IL-4 and IL-10 production when anergy was induced with high concentrations of the immunodominant epitope. JNK enzymatic activity was blocked in anergized T cells. The MBP-selected line could likewise be rendered unresponsive by incubation with supraoptimal concentrations of immunodominant peptide and anergy induction was accompanied by IL-10 release. Both T cell lines could be anergized by the autopresentation of native peptide since anergy was induced in cultures lacking fresh antigen-presenting cells. This study shows that the mitogen-activated protein kinase cascade is blocked when anergy is induced to high concentrations of soluble peptide.

Vaccination with BV8S2 protein amplifies TCR-specific regulation and protection against experimental autoimmune encephalomyelitis in TCR BV8S2 transgenic mice

TCR determinants overexpressed by autopathogenic Th1 cells can naturally induce a second set of TCR-specific regulatory T cells. We addressed the question of whether immune regulation could be induced naturally in a genetically restricted model in which a major portion of TCR-specific regulatory T cells expressed the same target TCR BV8S2 chain as the pathogenic T cells specific for myelin basic protein (MBP). We found vigorous T cell responses to BV8S2 determinants in naive mice that could be further potentiated by vaccination with heterologous BV8S2 proteins, resulting in the selective inhibition of MBP-specific Th1 cells and protection against experimental encephalomyelitis. Moreover, coculture with BV8S2-specific T cells or their supernatants reduced proliferation, IFN-gamma secretion, and encephalitogenic activity of MBP-specific T cells. These results suggest that immune regulation occurs through a nondeletional cytokine-driven suppressive mechanism.

Vaccination with BV8S2 Protein Amplifies TCR-Specific Regulation and Protection Against Experimental Autoimmune Encephalomyelitis in TCR BV8S2 Transgenic Mice

TCR determinants overexpressed by autopathogenic Th1 cells can naturally induce a second set of TCR-specific regulatory T cells. We addressed the question of whether immune regulation could be induced naturally in a genetically restricted model in which a major portion of TCR-specific regulatory T cells expressed the same target TCR BV8S2 chain as the pathogenic T cells specific for myelin basic protein (MBP). We found vigorous T cell responses to BV8S2 determinants in naive mice that could be further potentiated by vaccination with heterologous BV8S2 proteins, resulting in the selective inhibition of MBP-specific Th1 cells and protection against experimental encephalomyelitis. Moreover, coculture with BV8S2-specific T cells or their supernatants reduced proliferation, IFN-γ secretion, and encephalitogenic activity of MBP-specific T cells. These results suggest that immune regulation occurs through a nondeletional cytokine-driven suppressive mechanism.

EAE TCR Motifs and Antigen Recognition in Myelin Basic Protein-Induced Anterior Uveitis in Lewis Rats

T cells infiltrating the iris/ciliary body of Lewis rats with anterior uveitis (AU) that had been induced by myelin basic protein (MBP) immunization were previously found to share surface markers common to the T cells that cause experimental autoimmune encephalomyelitis (EAE). To determine whether these AU-associated T cells are in fact the same as those that infiltrate the central nervous system to cause EAE, we examined TCR V gene expression in T cells infiltrating the anterior chamber in rats with AU. As with EAE, we found a biased expression of Vβ8.2 and Vα2 in the iris/ciliary body and, although one would expect an influx of nonspecific inflammatory T cells, these biases were still evident at the peak of AU. An analysis of the TCR Vβ8.2 and Vα2 sequences derived from the iris/ciliary body demonstrated the presence of the same complementarity determining region 3 motifs found in MBP-specific T cells that are pathogenic for EAE and found in T cells derived from the central nervous system of rats with EAE. Finally, T cells isolated from the iris/ciliary body of rats with AU were found to proliferate in a specific fashion to MBP Ags. Thus, it appears that MBP-specific T cells are pathogenic for AU as well as EAE in the Lewis rat. In addition, the long-term presence of this highly restricted MBP response in the iris/ciliary body indicates that distinct immunoregulatory mechanisms exist in the environment of the eye. This provides an interesting model with which to address questions pertaining to the nature of T cells infiltrating the eye and their regulation during EAE and other systemic diseases.

EAE TCR motifs and antigen recognition in myelin basic protein-induced anterior uveitis in Lewis rats

T cells infiltrating the iris/ciliary body of Lewis rats with anterior uveitis (AU) that had been induced by myelin basic protein (MBP) immunization were previously found to share surface markers common to the T cells that cause experimental autoimmune encephalomyelitis (EAE). To determine whether these AU-associated T cells are in fact the same as those that infiltrate the central nervous system to cause EAE, we examined TCR V gene expression in T cells infiltrating the anterior chamber in rats with AU. As with EAE, we found a biased expression of Vbeta8.2 and Valpha2 in the iris/ciliary body and, although one would expect an influx of nonspecific inflammatory T cells, these biases were still evident at the peak of AU. An analysis of the TCR Vbeta8.2 and Valpha2 sequences derived from the iris/ciliary body demonstrated the presence of the same complementarity determining region 3 motifs found in MBP-specific T cells that are pathogenic for EAE and found in T cells derived from the central nervous system of rats with EAE. Finally, T cells isolated from the iris/ciliary body of rats with AU were found to proliferate in a specific fashion to MBP Ags. Thus, it appears that MBP-specific T cells are pathogenic for AU as well as EAE in the Lewis rat. In addition, the long-term presence of this highly restricted MBP response in the iris/ciliary body indicates that distinct immunoregulatory mechanisms exist in the environment of the eye. This provides an interesting model with which to address questions pertaining to the nature of T cells infiltrating the eye and their regulation during EAE and other systemic diseases.

Immunity to T Cell Receptor Peptides in Multiple Sclerosis. III. Preferential Immunogenicity of Complementarity-Determining Region 2 Peptides from Disease-Associated T Cell Receptor BV Genes*

Vaccination with synthetic TCR peptides from the BV5S2 complementarity-determining region 2 (CDR2) can boost significantly the frequency of circulating CD4+ peptide-specific Th2 cells in multiple sclerosis (MS) patients, with an associated decrease in the frequency of myelin basic protein (MBP)-reactive Th1 cells and possible clinical benefit. To evaluate the immunogenicity of CDR2 vs other regions of the TCR, we vaccinated seven MS patients with overlapping BV5S2 peptides spanning amino acids 1–94. Six patients responded to at least one of three overlapping or substituted CDR2 peptides possessing a core epitope of residues 44–52, and one patient also responded to a CDR1 peptide. Of the CDR2 peptides, the substituted (Y49T)BV5S2-38–58 peptide was the most immunogenic but cross-reacted with the native sequence and had the strongest binding affinity for MS-associated HLA-DR2 alleles, suggesting that position 49 is an MHC rather than a TCR contact residue. Two MS patients who did not respond to BV5S2 peptides were immunized successfully with CDR2 peptides from different BV gene families overexpressed by their MBP-specific T cells. Taken together, these results suggest that a widely active vaccine for MS might well involve a limited set of slightly modified CDR2 peptides from BV genes involved in T cell recognition of MBP.

Immunity to T cell receptor peptides in multiple sclerosis. III. Preferential immunogenicity of complementarity-determining region 2 peptides from disease-associated T cell receptor BV genes

Vaccination with synthetic TCR peptides from the BV5S2 complementarity-determining region 2 (CDR2) can boost significantly the frequency of circulating CD4+ peptide-specific Th2 cells in multiple sclerosis (MS) patients, with an associated decrease in the frequency of myelin basic protein (MBP)-reactive Th1 cells and possible clinical benefit. To evaluate the immunogenicity of CDR2 vs other regions of the TCR, we vaccinated seven MS patients with overlapping BV5S2 peptides spanning amino acids 1-94. Six patients responded to at least one of three overlapping or substituted CDR2 peptides possessing a core epitope of residues 44-52, and one patient also responded to a CDR1 peptide. Of the CDR2 peptides, the substituted (Y49T)BV5S2-38-58 peptide was the most immunogenic but cross-reacted with the native sequence and had the strongest binding affinity for MS-associated HLA-DR2 alleles, suggesting that position 49 is an MHC rather than a TCR contact residue. Two MS patients who did not respond to BV5S2 peptides were immunized successfully with CDR2 peptides from different BV gene families overexpressed by their MBP-specific T cells. Taken together, these results suggest that a widely active vaccine for MS might well involve a limited set of slightly modified CDR2 peptides from BV genes involved in T cell recognition of MBP.

Neonatal exposure of TCR BV8S2 transgenic mice to recombinant TCR BV8S2 results in reduced T cell proliferation and elevated antibody response to BV8S2, and increased severity of EAE

Transgenic (Tg) mouse models are unique tools for investigating regulatory mechanisms of the immune system. Mice bearing a T cell receptor (TCR) BV8S2 transgene derived from an encephalitogenic T cell clone are highly susceptible to experimental autoimmune encephalomyelitis (EAE), a T cell-mediated neurological disorder. Although the pathogenesis of EAE is not yet fully understood, TCR-specific regulatory T cells seem to play a role in its remission and/or recovery process. In previous studies, we showed that immunization of BV8S2 Tg mice with recombinant BV8S2 protein induced TCR-specific T cells and protection against EAE, clearly indicating the persistence of a functional TCR regulatory network in spite of the highly skewed T cell repertoire. To further investigate the natural regulatory role of TCR-specific T cells, we evaluated the effect on EAE of inducing neonatal tolerance to heterologous (rat) and homologous BV8S2 proteins in Tg mice. Neonatal exposure to rat BV8S2 protein induced "split" tolerance, characterized by decreased T cell proliferation but increased antibody responses to both rat and mouse BV8S2 proteins that are known to be cross-reactive. When challenged as adults with an encephalitogenic emulsion, Tg mice tolerized with rat but not mouse BV8S2 protein developed more severe EAE compared to control mice. These results demonstrate that immunity to BV8S2 determinants in BV8S2 Tg mice is naturally induced and functions to limit the severity of EAE.

Gender differences in experimental autoimmune encephalomyelitis develop during the induction of the immune response to encephalitogenic peptides

Multiple sclerosis (MS) strikes women more often than men. Gender differences in experimental autoimmune encephalomyelitis (EAE) parallel those seen in MS. We utilized the adoptive transfer model of EAE to determine the role of gender on the induction and effector phases of disease. PLP 139-151-sensitized spleen cells from female SJL mice were more effective at transferring disease than male cells. However, there were no gender differences in the frequency of PLP 139-151-specific T cells. PLP 139-151-specific female T cell lines induced more severe disease than male T cell lines. Disease severity was more strongly linked to the sex of the donor T cells, indicating that gender influences the immune response primarily during the induction phase.

Gonadal hormones influence the immune response to PLP 139-151 and the clinical course of relapsing experimental autoimmune encephalomyelitis

Females have an increased incidence of multiple sclerosis (2:1). This gender dimorphism can be studied effectively using a murine model of relapsing experimental autoimmune encephalomyelitis (R-EAE). We demonstrated previously that male SJL mice immunized with proteolipid protein (PLP) peptide 139-151 developed an initial episode of paralysis, but failed to relapse. In the present study, clinical EAE relapses were induced by orchidectomy. Relapses in castrated mice were accompanied by an influx of activated CD4+, Th1 cells into the CNS which were absent in sham mice. Our data suggests an important regulatory role for androgens on the immune response to PLP 139-151 and the clinical course of R-EAE.

The OX-40 receptor provides a potent co-stimulatory signal capable of inducing encephalitogenicity in myelin-specific CD4+ T cells

The OX-40 receptor, a member of the nerve growth factor/tumor necrosis factor receptor gene family, is expressed preferentially on autoreactive CD4+ T cells isolated from the site of inflammation in rats with clinical signs of experimental autoimmune encephalomyelitis (EAE). To examine whether the OX-40 receptor has biologic relevance to T cell function, we evaluated the ability of a rat OX-40 receptor-specific antibody to co-stimulate a myelin basic protein (MBP)-reactive CD4+ T cell line. The anti-OX-40 antibody provided a potent co-stimulatory signal to CD4+ T cells when added in conjunction with a submitogenic dose of anti-CD3, but the anti-OX-40 antibody alone did not produce a mitogenic response. The magnitude and dose-response of anti-OX-40 co-stimulation was virtually identical to the signal delivered to T cells when cultured with anti-CD28 in conjunction with anti-CD3. MBP-specific T cells stimulated with both anti-CD3 and anti-OX-40 antibodies expressed increased mRNA and protein for IL-2 when compared to anti-CD3 alone. MBP-specific T cells stimulated with both anti-CD3 and anti-OX-40 antibodies were also able to induce EAE when transferred into naive Lewis rats. In contrast, cells stimulated with anti-CD3 alone were not encephalitogenic. These data suggest that the function of the OX-40 receptor on activated T cells is to provide an alternative pathway for T cell co-stimulation that may be similar in potency to the CD28-mediated signal.

Effects of vaccination with T cell receptor peptides: epitope switching to a possible disease-protective determinant of myelin basic protein that is cross-reactive with a TCR BV peptide

Immunization of Lewis rats with guinea-pig myelin basic protein (Gp-MBP) induced T cell responses to primary and secondary encephalitogenic determinants, as well as to a third non-encephalitogenic epitope, residues 55-69. This sequence is of interest due to its protective activity against experimental autoimmune encephalomyelitis. Protection involved induction of MBP-55-69-specific T cells expressing cross-reactive TCR BV8S6 genes that activated regulatory T cells specific for TCR BV8S2 determinants expressed on encephalitogenic T cells. We here present and discuss new evidence suggesting a possible immunological cross-reactivity between the protective Gp-MBP-55-69 peptide and the regulatory BV8S2-39-59 peptide. This cross-reactivity, which may also occur between the human MBP-55-74 peptide and the BV12S2-38-58 sequence, has potentially important implications for human diseases such as multiple sclerosis.

Novel adjuvants for induction of T-cell and antibody responses to encephalitogenic and regulatory determinants in Lewis rats

Treatment of human autoimmune diseases may be enhanced by using adjuvants that can selectively induce immunoregulatory responses. Two versions of a novel nonionic block copolymer adjuvant suitable for human use, Optivax Oil Formulation (OF) and Optivax Aqueous Formulation (AF), were evaluated for induction of immunity to encephalitogenic and regulatory T-cell receptor (TCR) V-gene determinants. In Lewis rats immunized with myelin basic protein (BP), Optivax OF was more efficient than Optivax AF for inducing delayed type hypersensitivity (DTH), T-cell proliferation, antibodies, and even mild clinical signs of experimental autoimmune encephalomyelitis (EAE). Similarly, Optivax OF was more efficient for inducing inflammatory T-cell and antibody responses to immunoregulatory V beta 8.2 proteins and peptides than Optivax AF, which induced a noninflammatory Th2 response. In general, DTH response to the various immunogens was reflected by increased cellularity and mRNA levels for IFN-gamma in draining lymph nodes, whereas LN cell proliferation without DTH was characterized by increased IL-2 mRNA levels but low or absent IFN-gamma message. These data suggest important differential adjuvant effects of Optivax OF versus Optivax AF on the respective induction of Th1 versus Th2 responses that may be useful in the selective treatment of human immune disorders.

Multiple class I motifs revealed by sequencing naturally processed peptides eluted from rat T cell MHC molecules

Class I major histocompatibility complex (MHC) molecules interact with a diverse array of self and foreign peptides. Displayed on the cell surface, the class I/peptide complex provides an extracellular indication of the intracellular milieu. We have characterized the Lewis rat Vbeta8.2+ T cell hybridoma C14/BW12-12A1 by FACS analysis and have used immunoaffinity chromatography to purify class I molecules from these cells. Peptides eluted from the class I molecules have been fractionated by HPLC and sequenced. Self-peptide mixtures indicate two distinct peptide motifs, suggesting the possibility of multiple class I loci. The majority of the naturally processed peptide ligands were nonamers. Naturally processed peptide ligands fitting the first motif contained a hydrophobic leucine anchor residue at position three and a carboxyl-terminal serine anchor residue. A second motif was characterized by a tyrosine or phenylalanine residue at position three and a phenylalanine or isoleucine carboxyl-terminal residue. Four peptides derived from the Vbeta8.2 T cell receptor have sequences that fit these motifs, providing a mechanistic explanation for their immunoregulatory role. Identification of these class I peptide binding motifs will be useful for predicting potential CTL epitopes in studies on autoimmunity, immunoregulation and transplantation in the Lewis rat.

A TCR V alpha CDR3-specific motif associated with Lewis rat autoimmune encephalomyelitis and basic protein-specific T cell clones

To investigate TCR V alpha gene expression in the Lewis rat model of experimental autoimmune encephalomyelitis, we obtained V alpha chain sequences from two V beta8.2+-encephalitogenic, BP72-89-specific T cell clones. Two different V alpha genes, a V alpha2 gene and a V alpha23 gene, are utilized, but both were found to contain an asparagine repeat (Asn3+) sequence present in the V alpha CDR3 region. This Asn3+ motif is also present in the previously reported sequence of a BP68-88-specific hybridoma, 510, which utilizes a different V alpha2 gene family member. In further experiments, spinal cord T cells were isolated at the onset of basic protein (BP)-induced disease and sorted for the OX-40 activation marker, which we have previously used to enrich for specifically activated T cells. Analysis of V alpha expression in the OX-40+ population revealed the biased use of three V alpha genes, V alpha1, V alpha2, and V alpha23. The Asn3+ motif was present in the V alpha CDR3 region of V alpha1, V alpha2, and V alpha23 cDNA derived from OX-40+ spinal cord T cells but found to be generally absent in the OX-40- spinal cord population. Since these Asn3+ motif-bearing V alpha chain sequences are nearly identical to those utilized by the BP-specific encephalitogenic clones described, it is likely that these V alpha sequences are derived from disease-associated T cells in the spinal cord. Thus, we demonstrate that the Asn3+ V alpha CDR3 motif is strongly associated with experimental autoimmune encephalomyelitis in the Lewis rat and propose that it plays a role in TCR recognition of a specific BP peptide/MHC complex.

A TCR V alpha CDR3-specific motif associated with Lewis rat autoimmune encephalomyelitis and basic protein-specific T cell clones

To investigate TCR V alpha gene expression in the Lewis rat model of experimental autoimmune encephalomyelitis, we obtained V alpha chain sequences from two V beta8.2+-encephalitogenic, BP72-89-specific T cell clones. Two different V alpha genes, a V alpha2 gene and a V alpha23 gene, are utilized, but both were found to contain an asparagine repeat (Asn3+) sequence present in the V alpha CDR3 region. This Asn3+ motif is also present in the previously reported sequence of a BP68-88-specific hybridoma, 510, which utilizes a different V alpha2 gene family member. In further experiments, spinal cord T cells were isolated at the onset of basic protein (BP)-induced disease and sorted for the OX-40 activation marker, which we have previously used to enrich for specifically activated T cells. Analysis of V alpha expression in the OX-40+ population revealed the biased use of three V alpha genes, V alpha1, V alpha2, and V alpha23. The Asn3+ motif was present in the V alpha CDR3 region of V alpha1, V alpha2, and V alpha23 cDNA derived from OX-40+ spinal cord T cells but found to be generally absent in the OX-40- spinal cord population. Since these Asn3+ motif-bearing V alpha chain sequences are nearly identical to those utilized by the BP-specific encephalitogenic clones described, it is likely that these V alpha sequences are derived from disease-associated T cells in the spinal cord. Thus, we demonstrate that the Asn3+ V alpha CDR3 motif is strongly associated with experimental autoimmune encephalomyelitis in the Lewis rat and propose that it plays a role in TCR recognition of a specific BP peptide/MHC complex.

Myelin basic protein-specific and TCR V beta 8.2-specific T-cell lines from TCR V beta 8.2 transgenic mice utilize the same V alpha and V beta genes: specificity associated with the V alpha CDR3-J alpha region

Our analysis of TCR V gene usage in mice transgenic for the V beta 8.2 gene has demonstrated that T cells isolated from the spinal cord of these transgenic mice during active experimental autoimmune encephalomyelitis were significantly biased for V alpha 2 expression. This V alpha 2 bias was noted in T cells derived from the periphery as well but only after stimulation with specific antigen. Thus, spinal cord-derived pathogenic T cells had already undergone activation and expansion within the central nervous system environment of these mice. As part of an investigation of regulatory function in these V beta 8.2 transgenic mice, two T cell lines were selected. The first T cell line is encephalitogenic and specific for the dominant myelin basic protein peptide NAc1-11, while the second T cell line is specific for the V beta 8.2 protein. Surprisingly, polymerase chain reaction and sequence analysis of the TCR from both the T cell lines demonstrated that they utilize identical V beta, D beta, J beta, and V alpha gene segments. The only difference found was in their use of the J alpha gene segment, indicating that this region of the TCR molecule can play a key role in determining antigen specificity.

Treatment of multiple sclerosis with T-cell receptor peptides: results of a double-blind pilot trial

A T-cell receptor (TCR) peptide vaccine from the V beta 5.2 sequence expressed in multiple sclerosis (MS) plaques and on myelin basic protein (MBP)-specific T cells boosted peptide-reactive T cells in patients with progressive MS. Vaccine responders had a reduced MBP response and remained clinically stable without side effects during one year of therapy, whereas nonresponders had an increased MBP response and progressed clinically. Peptide-specific T helper 2 cells directly inhibited MBP-specific T helper 1 cells in vitro through the release of interleukin-10, implicating a bystander suppression mechanism that holds promise for treatment of MS and other autoimmune diseases.

MHC-restriction, cytokine profile, and immunoregulatory effects of human T cells specific for TCR V beta CDR2 peptides: comparison with myelin basic protein-specific T cells

HLA-DR2+ patients with multiple sclerosis (MS) that respond to vaccination with TCR V beta 5.2-38-58 peptides have increased frequencies of TCR peptide-specific T cells, reduced frequencies of myelin basic protein (MBP)-specific T cells, and a better clinical course than non-responders. To evaluate possible network regulation of MBP responses by TCR peptide-specific T cells, we compared properties of both cell types. Both MBP- and TCR peptide-specific T cell clones were CD4+ and predominantly HLA-DR restricted. HLA-DR2, which is in linkage disequilibrium in MS patients, preferentially restricted TCR peptide-specific clones as well as MBP-specific responses in HLA-DR2 and DR2,3+ donors. Within the DR2 haplotype, however, both DR beta 1*1501 and DR beta 5*0101 alleles could restrict T cell responses to V beta CDR2 peptides, whereas responses to MBP were restricted only by DR beta 5*0101. TCR peptide-specific clones expressed message for Th2 cytokines, including IL-4, IL-5, IL-6, IL-10, and TGF-beta, whereas MBP-specific T cell clones expressed the Th1 cytokines IFN-gamma and IL-2. Consistent with the Th2-like cytokine profile, TCR peptide-specific T cell clones expressed higher levels of CD30 than MBP-specific T cells. Culture supernatants from TCR peptide-specific T cell clones, but not from MBP- or Herpes simplex virus-specific T cells, inhibited both proliferation responses and cytokine message production of MBP-specific T cells. These results demonstrate distinct properties of MBP and TCR peptide-specific T cells, and indicate that both target and bystander Th1 cells can be inhibited by Th2 cytokines secreted by activated TCR peptide-specific T cells. These data support the rationale for TCR peptide vaccination to regulate pathogenic responses mediated by oligoclonal T cells in human autoimmune diseases.

Male SJL mice do not relapse after induction of EAE with PLP 139-151

SJL mice immunized with proteolipid protein (PLP) develop relapsing experimental autoimmune encephalomyelitis (R-EAE). R-EAE is a CD4+, Th1 cell-mediated demyelinating disease of the central nervous system (CNS) that is used as a model for the human disease multiple sclerosis (MS). Previous studies showed that young (< 8 weeks) male SJL mice were resistant to active induction of EAE with CNS homogenate, while female mice were susceptible. We have recently observed that young male SJL mice immunized with a major encephalitogenic peptide of myelin, PLP 139-151, developed initial clinical and histological symptoms of EAE with a severity similar to age-matched females; however, unlike females, male mice did not relapse. Significant T cell proliferation to PLP 139-151, but not to other PLP and myelin basic protein (MBP) epitopes, was observed in both males and females during the initial episode, recovery, and first relapse of clinical disease. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of lymphokine mRNA revealed differences in IFN-gamma and IL-4 synthesis consistent with the hypothesis that Th2 T cells develop in young male SJL mice that regulate the relapsing phase of the disease. These data suggest that immunization of young male SJL mice with PLP 139-151 overrides a defect in antigen presentation responsible for the previously observed resistance to EAE, and that natural processing and presentation of neuroantigens during the course of acute EAE induces Th2 cells that prevent the relapse of disease.

Variation in H-2K(k) peptide motif revealed by sequencing naturally processed peptides from T-cell hybridoma class I molecules

Class I major histocompatibility complex (MHC) molecules interact with a diverse array of self and foreign peptides, displaying them on the cell surface and providing an extracellular indication of intracellular invasion. The most clearly defined role for these class I/peptide complexes is to cause effector responses upon binding to antigen-specific receptors of cytotoxic T cells. We have characterized the mouse thymoma/rat V beta 8.2+ T-cell hybridoma C14/BW12-12A1 by fluorescence-activated cell sorting analysis and have used immunoaffinity chromatography to purify class I molecules from these cells. The peptides bound to the class I molecules were fractionated by high-performance liquid chromatography and sequenced. Self-peptide mixtures eluted from the mouse H-2Kk class I allele revealed a dominant primary sequence motif, with a carboxyl-terminal residue that appeared to be invariantly valine and a secondary or auxiliary anchor residue at position 2 that could be either glutamate or proline. The majority of naturally processed peptide ligands appeared to be octamers. Although peptides eluted off H-2Kk molecules from tissue derived from a number of different inbred mouse strains also appeared to be octamers, others have reported that isoleucine is the dominant carboxyl-terminal residue. Thus, different cell types displayed distinct differences in naturally processed peptides bound by the same class I alleles. The variation in naturally processed peptides loaded onto the same class I allele most likely reflects the nature of the pool of peptides within the cell available for loading class I molecules.

Neonatal injection of Lewis rats with recombinant V beta 8.2 induces T cell but not B cell tolerance and increased severity of experimental autoimmune encephalomyelitis

In Lewis rats with experimental autoimmune encephalomyelitis (EAE) mediated by V beta 8.2 effector cells, anti-idiotypic T cells and antibodies could be boosted by injection of V beta 8.2 peptides, inducing both T cells and antibodies that reduced the severity and shortened the course of disease. However, EAE in Lewis rats is self-limiting, and we sought to determine if the anti-idiotypic response contributed to the natural recovery process. In a previous study, we found that adult tolerance induced to one of the regulatory idiotopes, V beta 8.2-44-54, caused worsening of EAE, implicating response to this epitope in recovery from EAE. However, neonatally-induced tolerance to V beta 8.2-44-54 did not alter the course of EAE, suggesting either compensation by additional V beta 8.2 determinants, or mechanistic differences in tolerization protocols. In this report, we reevaluate the role of V beta 8.2 determinants in recovery from EAE, using two recombinant V beta 8.2 constructs to induce neonatal tolerance to the comprehensive set of V beta 8.2 epitopes prior to adult induction of EAE. We found that neonatal exposure to either of the recombinant V beta 8.2 molecules induced "split" tolerance-specific T cell tolerance but enhanced antibody responses- and a more severe course of EAE. In contrast, neonatal exposure to a V beta 8.2 + T cell hybridoma or a control protein did not induce T cell tolerance to V beta 8.2 determinants and did not alter the EAE disease course. These results are consistent with those obtained by inducing adult tolerance, and suggest that our previous result (normal recovery from EAE in rats neonatally tolerized to V beta 8.2-44-54) was probably due to a compensatory response to other V beta 8.2 determinants. In both studies, the data clearly implicate T cell recognition of V beta 8.2 determinants in the natural EAE recovery process.

Prevention and treatment of relapsing autoimmune encephalomyelitis with myelin peptide-coupled splenocytes

Injection of antigen cross-linked accessory cells has proven to be an efficient and highly selective approach for inducing epitope-specific peripheral tolerance. This approach has been used successfully to inhibit induction of experimental autoimmune encephalomyelitis (EAE) and to dissect the relative dominance of component encephalitogenic determinants that contribute to both acute and relapsing EAE. In this study, we evaluated the tolerogenic effect of the dominant encephalitogenic epitope for SJL/J mice, residues 139-151 of myelin proteolipid protein (PLP), on the induction and relapses of EAE induced actively with PLP139-151/CFA. Our results demonstrate the powerful protective effect of treating mice before induction of EASE with PLP139-151-conjugated splenocytes (SPL) on the incidence and severity of both the initial episode and the first relapse of EAE. Moreover, treatment of mice on the first day of onset of clinical signs of EAE reduced the severity of the first relapse, apparently by reducing T cell recognition of PLP139-151, although no significant therapeutic effect was observed during the initial treated clinical episode. These data demonstrate the utility of using neuroantigen-coupled accessory cells to prevent and treat relapsing EAE.

V beta CDR3 motifs associated with BP recognition are enriched in OX-40+ spinal cord T cells of Lewis rats with EAE

Spinal cord (SC) T cells were isolated at the onset of actively induced experimental autoimmune encephalomyelitis (EAE) and sorted for the presence of the OX-40 activation marker. Previously, we reported an enhanced bias in V beta 8.2 expression as well as enhanced proliferative responses to basic protein antigens among the OX-40+ SC T cells. Here we demonstrate that CDR3 motifs associated with EAE are present at a significantly higher frequency in V beta 8.2 sequences of OX-40+ SC T cells (16/17) compared with those of OX-40- SC T cells (5/17). Thus, the OX-40 antigen may be useful as a marker to isolate and characterize autoantigen-specific T cells from the site of inflammation in T-cell-mediated autoimmune diseases.

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.

Selective depletion of myelin-reactive T cells with the anti-OX-40 antibody ameliorates autoimmune encephalomyelitis

The OX-40 protein was selectively upregulated on encephalitogenic myelin basic protein (MBP)-specific T cells at the site of inflammation during the onset of experimental autoimmune encephalomyelitis (EAE). An OX-40 immunotoxin was used to target and eliminate MBP-specific T cells within the central nervous system without affecting peripheral T cells. When injected in vivo, the OX-40 immunotoxin bound exclusively to myelin-reactive T cells isolated from the CNS, which resulted in amelioration of EAE. Expression of the human OX-40 antigen was also found in peripheral blood of patients with acute graft-versus-host disease and the synovia of patients with rheumatoid arthritis during active disease. The unique expression of the OX-40 molecule may provide a novel therapeutic strategy for eliminating autoreactive CD4+T cells that does not require prior knowledge of the pathogenic autoantigen.

Natural immunodominant and experimental autoimmune encephalomyelitis-protective determinants within the Lewis rat V beta 8.2 sequence include CDR2 and framework 3 idiotopes

The V beta 8.2-39-59 peptide has served as a prototypic natural regulatory idiotope in Lewis rats developing experimental autoimmune encephalomyelitis (EAE). The purpose of the present study was to determine if additional regulatory regions were contained within the V beta 8.2 sequence expressed by most encephalogenic T cells. A comprehensive strategy utilizing V beta 8+ hybridomas, a recombinant (r) V beta 8.2 molecule, and overlapping synthetic V beta 8.2 peptides reconfirmed the natural recognition of the 39-59 idiotope, and revealed a second immunodominant and EAE-protective determinant residing within residues 71-90. Both the V beta 8.2-39-59 and V beta 8.2-71-90 peptides were immunogenic, and each was recognized after immunization of Lewis rats with V beta 8+ cells or rV beta 8.2, indicating the preservation of these epitopes during the processing of the V beta 8.2 chain. Moreover, both epitopes were recognized naturally by T cells from rats developing or recovering from EAE that had never been purposefully immunized with V beta 8.2 peptides or rV beta 8.2. Of additional interest, the V beta 8.2-31-50 peptide was recognized by T cells from some rats immunized with complete Freund's adjuvant (CFA) alone. This peptide possessed mildly protective activity against EAE and thus could account for sporadic reports of CFA interference in EAE.

OX-40 antibody enhances for autoantigen specific V beta 8.2+ T cells within the spinal cord of Lewis rats with autoimmune encephalomyelitis

The V beta 8.2 T cell receptor (TCR) component is the predominant V beta gene product associated with antigen specific CD4+ T cell response to the major encephalitogenic epitope of myelin basic protein (MBP) in Lewis rats. Lewis rats were actively immunized with MBP in complete Freund's adjuvant and the V beta 8.2 positive and negative cells were analyzed for IFN-gamma mRNA production and OX-40 cell surface expression during the onset of EAE. The V beta 8.2+ T cells isolated from the spinal cord produced the majority of mRNA for IFN-gamma and also showed a marked enhancement for OX-40 expression compared to V beta 8.2+ T cells isolated from the lymph nodes. Only a fraction of IL-2 receptor positive T cells examined ex vivo from the inflammatory compartments co-expressed the OX-40 antigen. These results suggested that OX-40 cell surface expression could be used to identify and isolate the most recently activated T cells ex vivo. OX-40+ T cells isolated from the spinal cord were highly enriched for the V beta 8.2 T cell receptor component compared to OX-40- or unsorted spinal cord lymphocytes. OX-40+ T cells isolated from the spinal cord had an enhanced response to MBP, whereas OX-40+ cells isolated from the lymph nodes responded to both MBP and purified protein derivative. These data suggest that activated T cells can be isolated and characterized with the OX-40 antibody which only respond to the antigens present at the local site. The data also imply that isolation of OX-40+ T cells will be useful in identifying V beta biases and autoantigen specific cells within inflamed tissues even when the antigen specificity is unknown.

Myelin antigen-coupled splenocytes suppress experimental autoimmune encephalomyelitis in Lewis rats through a partially reversible anergy mechanism

Mechanisms of adult tolerance induced by injecting myelin Ag/ECDI (ethyl carbodiimide)-coupled splenocytes (Ag-SPL) were evaluated in Lewis rat experimental autoimmune encephalomyelitis (EAE). Rats could be tolerized against the major encephalitogenic epitope of guinea pig basic protein (Gp-BP), residues 72-89, using either S72-89-SPL or crude spinal cord homogenate (SCH)-SPL. In contrast to lymph node responses that were not affected significantly, the proliferation responses of blood T cells were markedly inhibited at the peak of EAE and during the recovery period to both Gp-BP and S72-89, but not to purified protein derivative (PPD), demonstrating Ag-specific tolerance. Tolerance induction reduced the number of infiltrating spinal cord (SC) cells, especially recruited CD45RC+ cells, as well as SC proliferation responses to S72-89 throughout the course of EAE. In contrast, SC response to PPD was increased at onset of EAE, but later during recovery the PPD response was also decreased compared with control rats. Tolerance induced by S72-89-SPL in blood and SC T cells could be reversed by incubation in IL-2, in accordance with an anergy model. BP-specific T cells preincubated in vitro with Gp-BP-SPL were rendered unresponsive to Gp-BP or S72-89, compared with the same T cells preincubated with histone (Hist)-SPL that remained Ag responsive. Consistent with an anergy model, preincubation with BP-SPL+IL-2 partially prevented tolerance induction to BP. T cells tolerized in vitro to BP-SPL induced milder EAE with delayed onset compared with control-tolerized T cells that produced lethal disease. These results demonstrate the efficacy of myelin Ag-coupled SPL in preventing EAE by selective tolerization of encephalitogenic T cells through a partially reversible anergy-induction mechanism.

Myelin antigen-coupled splenocytes suppress experimental autoimmune encephalomyelitis in Lewis rats through a partially reversible anergy mechanism

Mechanisms of adult tolerance induced by injecting myelin Ag/ECDI (ethyl carbodiimide)-coupled splenocytes (Ag-SPL) were evaluated in Lewis rat experimental autoimmune encephalomyelitis (EAE). Rats could be tolerized against the major encephalitogenic epitope of guinea pig basic protein (Gp-BP), residues 72-89, using either S72-89-SPL or crude spinal cord homogenate (SCH)-SPL. In contrast to lymph node responses that were not affected significantly, the proliferation responses of blood T cells were markedly inhibited at the peak of EAE and during the recovery period to both Gp-BP and S72-89, but not to purified protein derivative (PPD), demonstrating Ag-specific tolerance. Tolerance induction reduced the number of infiltrating spinal cord (SC) cells, especially recruited CD45RC+ cells, as well as SC proliferation responses to S72-89 throughout the course of EAE. In contrast, SC response to PPD was increased at onset of EAE, but later during recovery the PPD response was also decreased compared with control rats. Tolerance induced by S72-89-SPL in blood and SC T cells could be reversed by incubation in IL-2, in accordance with an anergy model. BP-specific T cells preincubated in vitro with Gp-BP-SPL were rendered unresponsive to Gp-BP or S72-89, compared with the same T cells preincubated with histone (Hist)-SPL that remained Ag responsive. Consistent with an anergy model, preincubation with BP-SPL+IL-2 partially prevented tolerance induction to BP. T cells tolerized in vitro to BP-SPL induced milder EAE with delayed onset compared with control-tolerized T cells that produced lethal disease. These results demonstrate the efficacy of myelin Ag-coupled SPL in preventing EAE by selective tolerization of encephalitogenic T cells through a partially reversible anergy-induction mechanism.

Antigen-specific T-cell activations distinguished by in vivo anti-CD4 antibody treatment

This study identifies activation characteristics of PPD-responsive T-cells that emerge after treatment with anti-CD4 monoclonal antibody (Mab). PPD-stimulated T-cell proliferations, OX40 phenotype and protein tyrosine phosphorylations involving p56lck (pp56lck) were compared to Con A stimulations using T-cells isolated from spleen and draining lymph node of CFA/PPD-immunized rats either untreated or treated in vivo with anti-CD4 Mab. Splenocytes stimulated by concanavalin A (Con A) showed correlated increases in proliferation, levels of pp56lck, and OX40 expression; these parameters were not correlated in splenocytes after PPD-stimulations. T-cells isolated from lymph nodes draining the site of CFA/PPD immunization proliferated in response to stimulation by either PPD or Con A, but only PPD-responsive cells showed correlation to the OX40 activation phenotype and increased levels of pp56lck. CD4+ T-cells isolated from either tissue compartment after anti-CD4 Mab treatments showed higher background and PPD-stimulated proliferations, and expressed lower levels of OX40. In contrast, anti-CD4 Mab treatments reduced (60%) and abolished Con A-stimulated proliferations of splenocytes and lymph node T-cells, respectively. The effects of anti-CD4 Mab treatment on pp56lck levels correlated only to the changes observed for Con A stimulations of splenocytes. These results demonstrate that PPD antigen-specific T-cell populations recovered from different tissue compartments were resistant to in vivo anti-CD4 Mab treatments and did not show the activation changes characteristics of CD4+ T-cells after Con A stimulation.

Analysis of V beta 8.2 CDR3 sequences from spinal cord T cells of Lewis rats vaccinated or treated with TCR V beta 8.2-39-59 peptide

Experimental autoimmune encephalomyelitis (EAE) in the Lewis rat can be induced with the administration of Gp-BP. This disease appears to be mediated at least in part by V beta 8.2+CD4+T cells, which specifically recognize the BP72-89 encephalitogenic peptide. Treatment or protection with V beta 8.2 CDR2 39-59 peptide can suppress or prevent clinical signs of EAE, presumably through the activation of regulatory T cells. Interestingly, V beta 8.2+ T cells continue to persist in the spinal cord of protected animals, although their appearance in the central nervous system (CNS) is delayed when compared with control animals with EAE. As part of our effort to elucidate the mechanism(s) of peptide protection and therapy, we sought to determine whether the V beta 8.2+ T cells in the spinal cord of protected or treated rats were truly representative of those found in rats with clinical EAE. Therefore, we examined the following CNS samples for the Asp96Ser97 motif, which has been identified previously in V beta 8.2+ BP-specific, encephalitogenic T cell clones: 1) rats protected with V beta 8.2-39-59 peptide, 2) rats treated with V beta 8.2-39-59 peptide, and 3) control rats with EAE. Our findings indicate that EAE-associated V beta 8.2+ sequences can still be found in both peptide-treated and peptide-protected rats. It appears that administration of V beta 8.2 CDR2 peptide does not prevent EAE-associated V beta 8.2+ T cells from infiltrating the CNS and that other mechanisms are at work to prevent the development of EAE.

Analysis of V beta 8.2 CDR3 sequences from spinal cord T cells of Lewis rats vaccinated or treated with TCR V beta 8.2-39-59 peptide

Experimental autoimmune encephalomyelitis (EAE) in the Lewis rat can be induced with the administration of Gp-BP. This disease appears to be mediated at least in part by V beta 8.2+CD4+T cells, which specifically recognize the BP72-89 encephalitogenic peptide. Treatment or protection with V beta 8.2 CDR2 39-59 peptide can suppress or prevent clinical signs of EAE, presumably through the activation of regulatory T cells. Interestingly, V beta 8.2+ T cells continue to persist in the spinal cord of protected animals, although their appearance in the central nervous system (CNS) is delayed when compared with control animals with EAE. As part of our effort to elucidate the mechanism(s) of peptide protection and therapy, we sought to determine whether the V beta 8.2+ T cells in the spinal cord of protected or treated rats were truly representative of those found in rats with clinical EAE. Therefore, we examined the following CNS samples for the Asp96Ser97 motif, which has been identified previously in V beta 8.2+ BP-specific, encephalitogenic T cell clones: 1) rats protected with V beta 8.2-39-59 peptide, 2) rats treated with V beta 8.2-39-59 peptide, and 3) control rats with EAE. Our findings indicate that EAE-associated V beta 8.2+ sequences can still be found in both peptide-treated and peptide-protected rats. It appears that administration of V beta 8.2 CDR2 peptide does not prevent EAE-associated V beta 8.2+ T cells from infiltrating the CNS and that other mechanisms are at work to prevent the development of EAE.

Studies on T-cell receptors involved in experimental autoimmune encephalomyelitis using the complementary peptide recognition approach

Based upon Blalock's complementary recognition approach, a complementary or antisense peptide (CP) was designed to the experimental autoimmune encephalomyelitis (EAE) epitope peptide, rat myelin basic protein (MBP) peptide 72-82. This peptide (EAE CP) was shown to have some sequence similarities to T-cell receptors (TCR) and MHC II molecules in a sequence homology search. Solid-phase binding assays demonstrated specific and high affinity binding (3 and 4 microM) between the EAE CP and the rat and guinea pig EAE epitope peptides (Rt72-82 and Gp69-82), respectively. This EAE CP was also found to be immunogenic in rats in an ear swelling test for delayed type hypersensitivity (DTH) reactions and an ELISA for antibody responses. However, a rabbit antibody generated to EAE CP was shown to be unable to stain the V beta 8+ EAE susceptible T-cells in immunofluorescence analyses. This EAE CP was also used in attempts to down-regulate EAE and the results showed that prior immunization with EAE CP in complete Freund's adjuvant could not prevent the Lewis rats from developing EAE. Although the data on sense-antisense peptide interaction were positive and the EAE CP was immunogenic, the inability of EAE CP to regulate EAE indicates that the CP approach may not be generally applicable.

Effects of anti-CD4 antibody: enhancement of lymph node PPD-memory T cell response

In vitro incubations of CD4+ T cells with anti-CD4 monoclonal antibody (Mab) demonstrated saturation binding and inhibited both PPD-stimulated proliferation and delayed-type hypersensitivity (DTH) after passive transfer of these cells into naive rats. In comparison, in vivo administration of anti-CD4 Mab into rats, 2 weeks after CFA immunization (PPD priming), saturated CD4 molecules expressed on T lymphocytes and depleted significant percentages of CD4+ T cells from blood, spleen, and lymph nodes, yet failed to cause significant inhibition of PPD-stimulated DTH ear swelling. Only repeated in vivo administration of anti-CD4 Mabs during the CFA/PPD antigen priming caused significant decreases (36 +/- 5%) in PPD-stimulated DTH ear swelling. T cells isolated from the blood and spleen showed insignificant relative decreases in PPD-stimulated proliferation after anti-CD4 treatments. In contrast, PPD-stimulated proliferation of T cells isolated from the draining lymph nodes after anti-CD4 treatments showed dramatic increases in PPD reactivity. PPD stimulation of T cells isolated from the draining lymph nodes of anti-CD4 Mab-treated rats produced relative phenotypic changes in CD4 coexpressions with CD45RC (inverse memory), CD49d (inflammatory adhesion integrin VLA-4), and OX40 (CD4+ blast), representative of memory CD4+ T cell blasts with reduced capacity for endothelial infiltration. These data demonstrate that depletion of CD4+ T cells by anti-CD4 Mab injections, administered either during or after antigen priming, selectively enhanced memory responses in T lymphocytes in the draining lymph nodes.

Increased severity of experimental autoimmune encephalomyelitis in rats tolerized as adults but not neonatally to a protective TCR V beta 8 CDR2 idiotope

The ability of synthetic V region peptides to induce regulatory T cells and Abs in rodents and humans provides clear evidence that these idiotopes do not naturally induce tolerance. In this study, we investigated the ability of TCR V beta 8.2 peptides to experimentally induce specific T cell tolerance, as measured by loss of Ag-specific proliferation and delayed-type hypersensitivity responses, and by increased susceptibility to experimental autoimmune encephalomyelitis (EAE). We found that both neonatal and adult exposure to V beta 8.2-39-59 or V beta 8-44-54 peptides could induce efficient T cell tolerance, resulting in a significant inhibition of peptide-specific proliferative responses. In addition, neonatal tolerance resulted in a partial reduction in delayed-type hypersensitivity response and an inability to vaccinate against EAE after adult immunization with the tolerizing peptide. We further evaluated the contribution of naturally induced TCR-specific responses to EAE resistance induced by challenging neonatally or adult tolerized rats with myelin basic protein in adjuvant. The clinical course of EAE was not significantly altered in rats tolerized neonatally to V beta 8.2 peptides, but both the severity and incidence of mortality from EAE was increased in rats tolerized as adults with V beta 8.2 peptides conjugated to syngeneic splenocytes. These results demonstrate that V beta 8.2 peptides are tolerogenic as well as immunogenic. Moreover, the observation of different effects of neonatal vs adult tolerization on the course of EAE suggests either the emergence of additional protective idiotopes after neonatal tolerization and/or mechanistic differences in the two tolerance-inducing protocols. Most importantly, the enhancement of clinical EAE in rats tolerized as adults with V beta 8.2 peptides provides evidence for an innate regulatory role of the CDR2 idiotope in recovery from EAE.

Increased severity of experimental autoimmune encephalomyelitis in rats tolerized as adults but not neonatally to a protective TCR V beta 8 CDR2 idiotope

The ability of synthetic V region peptides to induce regulatory T cells and Abs in rodents and humans provides clear evidence that these idiotopes do not naturally induce tolerance. In this study, we investigated the ability of TCR V beta 8.2 peptides to experimentally induce specific T cell tolerance, as measured by loss of Ag-specific proliferation and delayed-type hypersensitivity responses, and by increased susceptibility to experimental autoimmune encephalomyelitis (EAE). We found that both neonatal and adult exposure to V beta 8.2-39-59 or V beta 8-44-54 peptides could induce efficient T cell tolerance, resulting in a significant inhibition of peptide-specific proliferative responses. In addition, neonatal tolerance resulted in a partial reduction in delayed-type hypersensitivity response and an inability to vaccinate against EAE after adult immunization with the tolerizing peptide. We further evaluated the contribution of naturally induced TCR-specific responses to EAE resistance induced by challenging neonatally or adult tolerized rats with myelin basic protein in adjuvant. The clinical course of EAE was not significantly altered in rats tolerized neonatally to V beta 8.2 peptides, but both the severity and incidence of mortality from EAE was increased in rats tolerized as adults with V beta 8.2 peptides conjugated to syngeneic splenocytes. These results demonstrate that V beta 8.2 peptides are tolerogenic as well as immunogenic. Moreover, the observation of different effects of neonatal vs adult tolerization on the course of EAE suggests either the emergence of additional protective idiotopes after neonatal tolerization and/or mechanistic differences in the two tolerance-inducing protocols. Most importantly, the enhancement of clinical EAE in rats tolerized as adults with V beta 8.2 peptides provides evidence for an innate regulatory role of the CDR2 idiotope in recovery from EAE.