T cell response to myelin basic protein in the context of the multiple sclerosis-associated HLA-DR15 haplotype: peptide binding, immunodominance and effector functions of T cells

In this study, we evaluated the role of the two functional HLA-DR heterodimers, DR2a (DRα paired with the β chain encoded by DRB5^*0101) and DR2b (DRα paired with the β chain encoded by DRB1^*1501), that are coexpressed in the multiple sclerosis (MS)-associated haplotype HLA-DR15 Dw2, in presenting myelin basic protein (MBP) peptides to MBP-specific T cell lines (TCL). Our results show that both HLA-DR molecules serve as restriction elements for HLA-DR15-restricted TCL. Slightly higher numbers of TCL use DR2a as restriction element, and the epitopes contained in the immunodominant C-terminal region (131–159) are uniquely restricted by DR2a. The immunodominant middle epitope (81–99) is recognized in the context of both DR2a and DR2b, but this specificity strongly dominates the DR2b-restricted T cell response. Overall, immunodominance in the MBP-specific T cell response correlated well with peptide binding to DR2a or DR2b, demonstrating that the affinity of MHC-peptide interactions is important for shaping the T cell response to this autoantigen. Furthermore, we show that binding of the middle MBP peptide to HLA-DR15 molecules prevents cleavage by cathepsin D, a protease abundantly found in endosomal processing compartments, and thus contributes to its immunodominance. Surprisingly, the restriction element employed by MBP-specific T cell clones influenced the effector function (i.e., cytotoxic activity) of T cells irrespective of their peptide fine specificity.     

Cytokine secretion profile of myelin basic protein-specific T cells in multiple sclerosis

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system with a presumed autoimmune pathogenesis involving autoantigen-specific CD4+ T cells and cytokines. A similar frequency of T cells responding to myelin basic protein (MBP), a putative target in MS, has been observed in MS patients and controls. To dissect the differences between MBP-specific T cells in patients and controls, we have analyzed the cytokine secretion profile of such autoreactive T cells. MBP-specific T cell clones (TCC) were isolated from the peripheral blood of MS patients and controls by limiting dilution. Expression of mRNA for interferon-gamma (IFN-gamma), interleukin (IL)-4, IL-10, tumor necrosis factor-alpha (TNF-alpha) and transforming growth factor-beta (TGF-beta) was assessed by polymerase chain reaction whereas secretion of cytokine protein was measured by ELISA. MBP-specific TCC exhibited a heterogeneous cytokine secretion profile with clones displaying Th1, Th2 and Th0 phenotypes. A significant difference in the distribution of the cytokine profile was noted between MS patients and controls. Although the frequency of Th1 secreting MBP-reactive TCC was similar between MS patients and controls, stable MS patients had a significant association with the Th0 phenotype whereas healthy individuals were associated with the Th2 phenotype. In comparison to control TCC, MBP-specific TCC from MS patients secreted increased amounts of IFN-gamma, IL-4 and IL-10 and decreased quantities of TGF-beta. Thus, these studies suggest that there is a dysregulation in the balance between pro-inflammatory Th1 and anti-inflammatory Th2 cytokines in MS. It appears that the presence of Th1 secreting autoreactive T cells in healthy individuals may be counterbalanced by the presence of cells secreting Th2 cytokines and by the augmented production of the immunosuppressive cytokine TGF-beta, whereas in MS there is a decrease in these anti-inflammatory agents.     

Myelin basic protein-specific T lymphocyte lines from MS patients and healthy individuals.

We derived a total of 146 T lymphocyte lines specific for human myelin basic protein (MBP) from the peripheral blood of 20 MS patients and from a control group of 12 healthy donors, and determined the reactivities of T cell lines by [3H]thymidine incorporation on exposure to MBP and MBP peptides 1-44, 45-89, and 90-170. We defined HLA restriction of the T lines by using monoclonal antibodies against monomorphic determinants on human HLA-DR, HLA-DQ, and HLA-DP molecules. MBP-specific T cell lines could be isolated with a comparable efficiency from MS patients and healthy individuals. In both groups, MBP-specific T lymphocytes recognized at least 4 different epitopes in the MBP molecule, and specificities showed comparable patterns for different MBP peptides. MBP-specific T cell lines derived from MS patients and controls were restricted by DR products of the human major histocompatibility class II locus. Notable phenotypic differences of T cell lines existed between the 2 groups. Lines isolated from MS patients expressed predominantly the CD3+ CD4+ CD8- phenotype, while some control lines were composed of up to 87% CD3+CD4+CD8+ T lymphocytes. These findings illustrate the presence of MBP-specific T cells in MS patients and controls that are similarly sensitized to MBP and restricted by HLA-DR products.     

Effects of oral tolerance induction by myelin basic protein on Vβ8+ lewis rat T cells

Encephalitogenic T cells from Lewis rats use a restricted T cell receptor (TCR) gene combination, Vβ8.2 and Vα2. The oral administration of myelin basic protein (MBP) to Lewis rats prior to encephalito-genic challenge results in a marked inhibition of clinical neurologic signs of encephalitis, reduced central nervous system pathology, suppressed T cell reactivity to MBP, and decreased serum anti-MBP antibody responses. The present study determined the TCR Vβ8 gene usage in rats rendered orally tolerant to MBP as compared with vehicle-fed or unfed controls. Total RNA was extracted from lymph node cells (LNC), Northern blots run, and hybridizations performed using a rat β chain V region probe positive for Vβ8.2. The results indicate that feeding MBP results in a decrease in Vβ8+ TCR RNA expression in lymph nodes draining the site of encephalitogenic challenge. T cell proliferation was reduced in LNC of tolerized rats relative to control rats. No change in the Vβ8+ TCR RNA expression or MBP reactivity was observed in the mesenteric lymph nodes (MLN) of vehicle-fed or MBP-fed rats, although an increase in cell number was found in the MLN of both groups. These results suggest that the mechanisms of orally induced tolerance involve local clonal deletion or migration of Vβ8+ T cells, of which MBP-specific T cells are a part.     

Junctional region of the myelin basic protein-specific T cell receptor β chain in mice

Evidence for the existence of both conserved and diverse amino acid sequences in the Junctional regions of the myelin basic protein (MBP)-specific T cell receptors (TCR) in mice is presented. The Junctional region of the Nacl-11 MBP peptide-specific, H-2^u-restricted TCR β-chains is characterized by the utilization of similar amino acid sequences. In contrast, diverse Junctional sequences within the TCR β-chains of the p89-101 MBP peptide and H-2^s-restricted T cell clones are reported. These findings demonstrate that a limited heterogeneity of the MBP-specific T cell clones does exist. However, it may not be universal even in inbred mouse strains.     

Differential expression of costimulatory molecules B7-1 and B7-2 on microglial cells induced by Th1 and Th2 cells in organotypic brain tissue.

Autoreactive T-cells are involved in demyelination, neurodegeneration, and the recruitment of peripheral macrophages and nonspecific activated T-cells in autoimmune diseases such as multiple sclerosis (MS). The ligation of costimulatory B7 molecules on microglia with CD28/CTLA-4 on T-cells is thought to be crucial to the onset and course of MS and its rodent model experimental autoimmune encephalomyelitis (EAE). It is currently unclear as to how far the nature of infiltrating T-cells has an impact on the expression of the B7 molecules on microglia, the resident antigen-presenting cells (APCs) of the brain. We studied the expression of B7-1 and B7-2 on microglia after encounter with preactivated Th1 and Th2 cells from transgenic mice whose T-cells express a receptor (TCR) either specific to myelin basic protein (MBP) or ovalbumin (OVA) using murine organotypic entorhinal-hippocampal slice cultures (OEHSC). Our main finding was that Th1 cells downregulate the constitutive expression of B7-2 and induce B7-1 expression while Th2 cells do not induce this B7-1 upregulation. The main difference between MBP- and OVA-specific cells was seen in experiments were Th1 cells had direct contact to APCs but not to brain tissue. In contrast to MBP-specific Th1 cells, OVA-specific Th1 cells required the addition of antigen to upregulate B7-1 and downregulate B7-2. When the cells were allowed to have contact to brain tissue, no difference was seen in the pattern of B7 regulation between OVA- and MBP-specific T-cells. Our data suggest that T-cells are able to modulate B7 expression on microglial cells in the brain independent of antigen presentation through TCR/MHC-II ligation but presumably by soluble mediators.     

T-cell hybridoma specific for myelin oligodendrocyte glycoprotein-35-55 peptide produced from HLA-DRB1*1501-transgenic mice

The goal of this study was to establish an unlimited and standardized source of humanized myelin peptide-specific T cells for in vitro testing of biological function. Thus, we perpetuated myelin oligodendrocyte glycoprotein (MOG)-35-55 peptide-specific T cells obtained from immunized HLA-DRB1*1501-transgenic (Tg) mice by somatic fusions with BW5147 thymoma cells or BW5147 T-cell receptor (TCR) alpha(-)beta(-) variant (BW5147 variant) cells. The resulting T-cell hybridomas responded strongly to both mouse MOG-35-55 (42S) and human MOG-35-55 peptide (42P), regardless of which peptide was used for initial immunization, and were DRB1*1501 restricted. The MOG-35-55-reactive T-cell hybridomas were CD3(+)CD4(+)CD8(-) and expressed intracellular Th1 cytokines upon concanavalin A stimulation. Clones from either human MOG-35-55- or mouse MOG-35-55-selected hybridomas uniquely expressed the TCR BV8 gene in combination with AV17 and AV11 genes. V gene analyses confirmed the expression of TCR AV1, AV11, AV16, BV1, and BV5 gene segments in the widely used fusion partner BW5147 and demonstrated deletion of TCR AV1, AV11, and BV1 in the BW5147 variant. T-cell hybridomas were positively stained with anti-TCR beta-chain antibody on the cell surface, whereas neither BW5147 nor its variant had positive TCR surface expression. For functional application, we found that a monomeric form of the human HLA-DR2-derived recombinant T-cell receptor ligand (RTL) covalently linked to human MOG-35-55 peptide specifically inhibited proliferation of a hybridoma clone selected with human MOG-35-55 but not a different hybridoma clone selected with myelin basic protein. The RTL-induced inhibition in vitro of the human MOG-35-55 peptide-specific hybridoma reflected the ability of the RTL to inhibit experimental autoimmune encephalomyelitis induced by human MOG-35-55 peptide in HLA-DR2 transgenic mice. Thus, the MOG-35-55 peptide-specific T-cell hybridoma from DR2-Tg mice represents a novel humanized T-cell reagent useful for standardized biological screening of both DR2-restricted stimulation and RTL-dependent inhibition of response to human MOG-35-55 peptide.     

Cytokine phenotype of human autoreactive T cell clones specific for the immunodominant myelin basic protein peptide (83–99)

Experimental allergic encephalomyelitis (EAE), an animal model resembling multiple sclerosis (MS), is mediated by myelin antigen-specific CD4+ T cells secreting cytokines such as interferon-γ (IFN-γ), tumor necrosis factor-β (TNF-β), and the proinflammatory cytokine TNF-α—all associated with the T-helper-1 (Th1) T cell subset. Based on numerous similarities between MS and EAE, it has been postulated that Th1-like T cells are involved in the pathogenesis of MS. Production of proinflammatory cytokines such as IFN-γ and, in particular, TNF-α/β by autoreactive T cells is considered crucial for the initiation and amplification of inflammatory brain lesions and possibly also for direct myelin damage. In contrast, regulatory cytokines such as interleukin-4 (IL-4), IL-10, and IL-13, which are associated with the Th2-like phenotype, may play a role in the resolution of relapses. Although the human T cell response to myelin basic protein (MBP) is well characterized in terms of antigen specificity, HLA restriction, and T cell-receptor (TCR) usage, little is known about the cytokine pattern of these autoreactive T cells. To gain such information, conditions for studying cytokine secretion by human autoreactive T cell clones (TCC) were established. The cytokine secretion profile of human autoreactive CD4+ TCC, specific for myelin basic protein peptide (83–89) [MBP(83–99)], a candidate autoantigen in MS, was investigated. Our results show that TCC cytokine production in long-term culture was stable. In addition, the correlation of various cytokines within specific TCC revealed differences compared to murine T cells. The comparison of 30 human MBP(83–99)-specific TCC demonstrated heterogeneity in cytokine secretion, with a continuum between Th1- and Th2-like cells rather than distinct Th1 or Th2 subsets. These data are important for further investigation of the potential role of cytokines in the inflammatory process of MS, and provide a powerful tool to investigate therapeutic interventions with respect to their influence on cytokine secretion of autoreactive T cells. © 1996 Wiley-Liss, Inc.     

Characteristics of the T lymphocytes involved in experimental allergic encephalomyelitis

Both heterogeneity and restricted heterogeneity of the encephalitogenic myelin basic protein (MBP) peptide-specific T cell receptors (TCRs) were demonstrated in inbred animals depending on the strain-specific genetic characteristics, the stage of the disease, the compartment of the lymphocytes obtained and the methodology used. Nevertheless, the similar features of some MBP-specific TCRs demonstrated across species suggest that conservation of these autoantigen-specific molecules undoubtedly exists, even though the degree of this conservation is controversial. However, the unequivocal heterogeneity of the immune response directed at one of the most important myelin constituents, proteolipid lipoprotein (PLP), which occurs either as a primary or a secondary event during experimental allergic encephalomyelitis (EAE), indicates the complexity of the in vivo situation. Intramolecular and intermolecular spreading of antigen specificity during the course of the disease indicates that a TCR directed therapy may not be the choice of intervention in established disease even in individual strains of laboratory animals with restricted heterogeneity of the primary MBP-specific response. Studying the sequence of events, the recruited regulatory cells and cytokines, and the stromal factors controlling persistence or death of activated, memory cells in the tissue lesion, may reveal new therapeutic modalities with more universal applicabilities.     

Dysregulation of potentially pathogenic self reactivity is crucial for the manifestation of clinical autoimmunity

During the evolution of the autoimmune response to myelin basic protein (MBP), at least two distinct lymphocyte populations arise, one that is specific for determinants within the protein antigen and another that is specific for the receptors displayed by the antigen-specific lymphocytes themselves. The T-cell receptor (TCR)-specific lymphocytes appear to oppose the action of the pathogenic effector cells, which predominantly utilize the TCR Vβ8.2 gene segment. We will discuss our work suggesting that both CD4 and CD8 cells specific for different TCR determinants on the Vβ8.2 chain are involved in the regulation of MBP-specific CD4 T cells mediating experimental autoimmune encephalomyelitis. We suggest that a crucial balance between the effectors and regulators is decisive for the clinical manifestation of autoimmunity. © 1996 Wiley-Liss, Inc.     

Characterization of T cell lines derived from glatiramer-acetate-treated multiple sclerosis patients

We analyzed the effects of glatiramer acetate (GA) therapy on in vitro proliferative responses and cytokine production by lymphocytes derived from multiple sclerosis patients receiving this therapy. We confirmed that lymphocytes derived from GA na?ve patients show a high frequency of response when initially exposed to GA in vitro; this frequency decreased following GA therapy. The frequency of lymphocytes responding to whole MBP stimulation did not change with GA therapy. GA- and MBP-specific T cell lines generated from these patients by repeated cycles of in vitro stimulation did not cross react. Some (23%) whole MBP-reactive T cell lines did cross react with MBP peptide 83-99. The mean levels of interferon (IFN) gamma secretion and the mean ratio of IFN-gamma/IL-5 were lower for GA-reactive cell lines, derived from patients both prior to and during GA therapy, compared to MBP-reactive T cell lines. The proportion of IFN-gamma(+) cells in unfractionated lymphocyte preparations derived from the GA-treated patients did not differ from that found for healthy controls. Our findings indicate that GA-reactive T cell lines derived from GA-treated MS patients continue to show a relative Th2 cytokine bias consistent with a bystander suppressor function. GA treatment is not associated with a cytokine phenotype shift in the total T cell or MBP-reactive T cell populations.     

Rag-1-dependent cells are necessary for 1,25-dihydroxyvitamin D(3) prevention of experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is a demyelinating disease involving genetic and environmental risk factors. Geographic, genetic, and biological evidence suggests that one environmental risk factor may be lack of vitamin D. Here, we investigated how 1,25-dihydroxyvitamin D(3) (1,25-(OH)(2)D(3)) inhibits experimental autoimmune encephalomyelitis (EAE), an MS model. The experiments used adoptive transfer of TCR-transgenic (TCR1) cells specific for myelin basic protein (MBP) peptide into unprimed recipients. When unprimed TCR1 splenocytes were transferred, and the recipients were immunized with peptide, the mock-treated mice developed EAE, but the 1,25-(OH)(2)D(3)-treated recipients remained disease-free. Both groups had TCR1 T cells that proliferated in response to MBP Ac1-11 and produced IFN-gamma but not IL-4 in the lymph node. In the central nervous system (CNS), the mock-treated mice had activated TCR1 T cells that produced IFN-gamma but not IL-4, while the 1,25-(OH)(2)D(3)-treated mice had TCR1 T cells with a non-activated phenotype that did not produce IFN-gamma or IL-4. When activated TCR1 T cells producing IFN-gamma were transferred into unprimed mice, the mock-treated and the 1,25-(OH)(2)D(3)-treated recipients developed EAE. Likewise, the 1,25-(OH)(2)D(3) did not inhibit Th1 cell IFN-gamma production or promote Th2 cell genesis or IL-4 production in vitro. Finally, the 1,25-(OH)(2)D(3) inhibited EAE in MBP-specific TCR-transgenic mice that were Rag-1(+), but not in animals that were Rag-1-null. Together, these data refute the hypothesis that the hormone inhibits Th1 cell genesis or function directly or through an action on antigen-presenting cells, or promotes Th2 cell genesis or function. Instead, the evidence supports a model wherein the 1,25-(OH)(2)D(3) acts through a Rag-1-dependent cell to limit the occurrence of activated, autoreactive T cells in the CNS.     

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 (Vβ8.2) in their TCR. In vivo administration of Vβ8.2 peptides in rats or mice can prevent and treat EAE by boosting regulatory anti-Vβ8.2-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 Vβ8.2+ 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 Vβ5.2 and Vβ6.1 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. © 1996 Wiley-Liss, Inc.     

Cytokine production by naive and primary effector CD4+ T cells exposed to norepinephrine

We recently showed that clones of Th1 cells, but not Th2 cells, expressed a functional beta-2-adrenergic receptor (beta2AR) and that either norepinephrine or the beta2AR agonist terbutaline stimulated this receptor to modulate the level of Th1 cytokines produced. In the present study, we show that norepinephrine and terbutaline stimulate the beta2AR to decrease the level of IL-2 produced by freshly isolated murine splenic naive CD4+ T cells from either Balb/C or DO11.10 transgenic mice and activated polyclonally with anti-CD3 and anti-CD28 mAbs. In contrast, the level of cytokines produced by primary effector Th1 and Th2 cells were unaffected when norepinephrine, terbutaline, or cAMP analogs were added at the time of restimulation. These results suggest that a diversity exists among CD4+ T-cell subsets with respect to the level of adrenergic receptor expression, responsiveness to cAMP, stage of cell differentiation, or a combination of the above.     

Limited repertoire of HLA-DRB1*0401-restricted MBP111-129-specific T cells in HLA-DRB1*0401 Tg mice and their pathogenic potential

Since myelin basic protein (MBP)111-129 is an immunodominant epitope in humans carrying HLA-DRB1*0401, we investigated the encephalitogenic potential of HLA-DRB1*0401-restricted MBP111-129-specific T cells using HLA-DRB1*0401/DRA*0101 transgenic (Tg) mice. Although we could not detect the primary recall response to MBP111-129 peptide after immunization of HLA-DRB1*0401/DRA*0101 Tg mice with human MBP, V beta 10(+) and V beta 2(+) HLA-DRB1*0401-restricted MBP111-129-specific T cells proliferated after restimulation of the lymph node cells with human MBP111-129 in vitro. The V beta 2(+) T cell line recognized only human MBP111-129 in the context of HLA-DRB1*0401, while the V beta 10(+) T cell line recognized both the human and murine MBP111-129 epitopes. Therefore, we examined the encephalitogenic potential of the V beta 10(+) T cell line in HLA-DRB1*0401/DRA*0101 Tg mice by adoptive transfer experiments. The V beta 10(+) T cell line induced mild EAE and inflammatory lesions were observed in the spinal cord and the brainstem. In the spinal cord, the inflammation was observed in the peripheral nerve roots as well as in the CNS. These data suggest the pathogenic potential of HLA-DRB1*0401-restricted MBP111-129-specific T cells in humans.     

Spontaneous development in vitro of a myelin basic protein-specific suppressor T cell line

T cell lines to myelin basic protein (MBP) developed following in vitro culture cause experimental allergic encephalomyelitis (EAE) upon transfer into naive recipient mice. We have, however, repeatedly observed that MBP-specific T cell lines lose their ability to transfer EAE after 40 days in culture. Analyses of such cell lines failed to show any differences in their proliferative responses to antigen, or in the secretion of interleukin-2 (IL-2) and/or IL-4 when compared to their encephalitogenic counterparts. In contrast, examinations of T cell receptor (TCR) beta-chain gene rearrangement patterns showed sequential changes in the clonal population of cells concomitant with the loss of encephalitogenic function. Furthermore, transfer of a non-encephalitogenic, genotypically altered cell line after long-term in vitro culture into mice challenged with MBP suppressed the development of EAE. These findings suggest that the development of such putative regulatory cells in vivo may be involved in the recovery in EAE.     

Cytokine profile of myelin basic protein—reactive T cells in multiple sclerosis and healthy individuals

Myelin basic protein (MBP)-reactive T cells have been implicated in the autoimmune pathogenesis of multiple sclerosis (MS). In this study, we examined the cytokine profile of 531 primary MBP-reactive T-cell lines and 72 independently established clones from 32 patients with MS and 18 healthy controls (NS) by using highly sensitive enzyme-linked immunosorbent assays. An increased number of primary T-cell lines producing interferon-γ (IFNγ) and/or interleukin-4 (IL-4) in response to MBP were found in patients with MS compared with controls. No distinct Th1 or Th2 subtypes could be demonstrated among the MBP-reactive clones. IL-4 was more frequently observed among MS-derived clones. Clones derived from MS patients produced increased levels of IL? 2, IL? 4, tumor necrosis factor-α (TNFα), IFNγ, and IL-10, but not IL-6. It is interesting that MBP-reactive T cells from MS patients expressing the disease-associated HLA-DRBI 15 allele produced increased quantities of TNFα, a cytokine suggested to play an important role in inflammation and demyelination. When challenged with either MBP or a bacterial superantigen, the clones expressed similar levels of the proinflammatory cytokine IFNγ. Our study suggests a functional difference in T-cell responses to MBP in patients with MS compared with healthy individuals, and provides further insights into the role of MBP-reactive T cells and their cytokine profile in the inflammatory processes of MS.     

Autoantigen-induced self lysis of human myelin basic protein-specific T lymphocytes.

Cytotoxic T cells reactive with myelin basic protein (MBP) may be isolated from most human subjects. Since activated T cells express major histocompatibility complex (MHC) class II antigens, we assessed whether MBP-specific, CD4+ T cells could present MBP or synthetic MBP peptides to themselves and whether this provoked self lysis. We examined two MBP-specific cell lines and eight T cell clones recognizing four different MBP epitopes. All T cell populations presented MBP as well as synthetic peptides to themselves eliciting self lysis of the T cell clones. CD4+ T cell populations recognizing another central nervous system (CNS) protein, proteolipid protein (PLP), or the recall antigen, Candida, did not exhibit this antigen-induced, autocytolytic activity. However, activated, PLP-reactive T cells were susceptible to lysis by cytotoxic MBP-specific T cells in the presence of MBP. These results suggest that antigen-induced self lysis of activated human T cells might limit an autoimmune response within a target organ independent of other immunoregulatory mechanisms.     

Response of human T lymphocyte lines to myelin basic protein: association of dominant epitopes with HLA class II restriction molecules

In animals, the selection in vitro of T cell lines to myelin basic protein (MBP) can define immunodominant and encephalitogenic epitopes which are preferentially associated with class II major histocompatibility (MHC) molecules. These principles were used to evaluate the specificity and MHC restriction of 14 human MBP-reactive T cell lines selected from normal individuals and patients with multiple sclerosis (MS) and other neurological diseases (OND). The four normal T cell lines recognized single, separate immunodominant MBP epitopes which were restricted by MHC molecules from the DR or in one case the DP class II locus. In contrast, the MS and OND T cell lines recognized multiple MBP epitopes, each in association with a discrete class II MHC molecule from the DR or DQ locus. Overall, HLA-DR molecules were used preferentially to associate with epitopes on human MBP, restricting 26/33 responses. As predicted from animal studies, T cells from genetically disparate individuals responded to different immunodominant epitopes on human MBP in association with distinct MHC class II molecules. HLA-DR2, which is overrepresented in MS patients, possessed an unusual capacity to restrict all eight epitopes identified on MBP in this study. These data provide the first evidence of genetically restricted human T cell recognition of potentially encephalitogenic epitopes of MBP.