Chronic neurologic dysfunction and demyelination induced in Lewis rats by repeated injections of encephalitogenic T-lymphocyte lines

Anti-S-nitrosocysteine antibodies are a predictive marker for demyelination in experimental autoimmune encephalomyelitis: implications for multiple sclerosis

Multiple sclerosis (MS) is characterized by inflammation within the CNS. This inflammatory response is associated with production of nitric oxide (NO) and NO-related species that nitrosylate thiols. We postulated that MS patients would exhibit an antibody (Ab) response directed against proteins containing S-nitrosocysteine (SNO-cysteine) and showed that anti-NO-cysteine Abs of the IgM isotype are in fact present in the sera of some MS patients (Boullerne et al., 1995). We report here the presence of a seemingly identical Ab response directed against SNO-cysteine in an acute model of MS, experimental autoimmune encephalomyelitis (EAE) induced in Lewis rats with the 68-84 peptide of guinea pig myelin basic protein (MBP(68-84)). Serum levels of anti-SNO-cysteine Abs peaked 1 week before the onset of clinical signs and well before the appearance of anti-MBP(68-84) Abs. The anti-SNO-cysteine Ab peak titer correlated with the extent of subsequent CNS demyelination, suggesting a link between Ab level and CNS lesion formation. In relapsing-remitting MS patients, we found elevated anti-SNO-cysteine Ab at times of relapse and normal values in most patients judged to be in remission. Two-thirds of patients with secondary progressive MS had elevated anti-SNO-cysteine Ab levels, including those receiving interferon beta-1b. The data show that a rise in circulating anti-SNO-cysteine Ab levels precedes onset of EAE. Anti-SNO-cysteine Abs are also elevated at times of MS attacks and in progressive disease, suggesting a possible role for these Abs, measurable in blood, as a biological marker for clinical activity.

Treatment of relapsing experimental autoimmune encephalomyelitis with largely MHC-matched allogeneic bone marrow transplantation

BUF rats suffering from severe relapsing experimental autoimmune encephalomyelitis (R-EAE), a model for multiple sclerosis, were treated with intensive cytoreductive therapy and grafting of allogeneic bone marrow (BM). BN.1B rats were used as EAE-resistant, largely MHC-matched donors, resembling human BMT from HLA-identical siblings. The treatment induces complete remission and low recurrence rates of R-EAE. Evidence is provided that the efficacy of the treatment depends on a high degree of lymphoablation: a minority of rats had host-type residual activated T lymphocytes in the CNS after treatment. Furthermore, complete replacement of host-type BM by donor-type hemopoietic cells is essential, as higher relapse rates were observed in animals with incomplete reconstitution by donor cells than in completely reconstituted rats. Overall, our results indicate that patients with severe MS might benefit from treatment with HLA-matched allogeneic BM.

T cells specific for the myelin oligodendrocyte glycoprotein mediate an unusual autoimmune inflammatory response in the central nervous system

Myelin oligodendrocyte glycoprotein (MOG)-specific T cells mediate an autoimmune inflammatory response in the central nervous system (CNS) that differs radically from conventional models of T cell-mediated experimental allergic encephalomyelitis (EAE). Using synthetic peptides an encephalitogenic T cell epitope of MOG for the Lewis rat was identified within the extracellular IgG V-like domain of the protein, amino acids 44-53 (FSRVVHLYRN). The adoptive transfer of CD4+ T cells specific for this epitope induce an intense, dose-dependent inflammatory response in the CNS of naive syngeneic recipients. However, unlike the inflammatory response induced by myelin basic protein (MBP)-specific T cell lines, inflammation mediated by the MOG peptide-specific T cells failed to induce a gross neurological deficit. This unexpected observation was not due to a reduction in the overall inflammatory response in the CNS, but was specifically associated with a decrease in the extent of parenchymal (as opposed to perivascular) inflammation, a selective decrease in the number of ED1+ macrophages infiltrating the CNS, and a total lack of peripheral nerve inflammation. The decreased recruitment of macrophages into the CNS could not be ascribed to deficiencies in the synthesis of interferon-gamma, tumor necrosis factor-alpha, interleukin (IL)-6 or IL-2 by the T cell line. Moreover, this sub-clinical inflammatory response induced severe blood-brain barrier dysfunction as demonstrated by the induction of severe clinical disease following intravenous injection of a demyelinating MOG-specific monoclonal antibody. The neurological deficit in EAE thus exhibits an unexpected dependence on the identity of the target autoantigen, which determines the extent and nature of the local inflammatory response and ultimately the extent of the neurological deficit.

Myelin basic protein-specific T cells induce demyelinating experimental autoimmune encephalomyelitis in Buffalo rats

This is the first description of acute demyelinating experimental autoimmune encephalomyelitis (EAE) induced in rats by myelin basic protein (BP)-specific T lymphocytes without the administration of demyelinating antibodies. BP-specific T cell lines were selected from inbred Buffalo-strain rats (Rt-1b) following techniques used to develop similar lines from Lewis rats (Rt-1l). Unlike those of Lewis rats, the spinal cords of Buffalo rats with T cell line-mediated EAE had prominent perivascular demyelination associated with mononuclear inflammation. Like Lewis rat lines. Buffalo rat BP-specific T cell lines transferred acute, non-relapsing EAE into syngeneic recipients, demonstrating that demyelination in passive acute EAE can occur without subsequent clinical relapses.

Characterization of basic protein-specific T cell lines selected from Lewis rats with relapsing experimental autoimmune encephalomyelitis

Relapsing experimental autoimmune encephalomyelitis (EAE) was induced in Lewis rats by intraperitoneal immunization with guinea pig whole central nervous system tissue. Basic protein (BP)-specific T cell lines selected from rats with relapsing EAE proliferated in response to BP, the 44-89 peptidase fragment of BP and the synthetic peptide, S72-89, as did lines selected from rats with non-relapsing EAE induced by immunization with guinea pig BP. BP-specific T cell lines selected from rats with relapsing EAE transferred acute but not relapsing EAE. BP-specific T cell lines selected from Lewis rats with relapsing EAE appear not to differ from those selected from rats with non-relapsing EAE.

Demyelination and early remyelination in experimental allergic encephalomyelitis passively transferred with myelin basic protein-sensitized lymphocytes in the Lewis rat

Histological studies were performed on Lewis rats with experimental allergic encephalomyelitis (EAE) passively transferred by myelin basic protein (MBP)-sensitized syngeneic spleen cells in order to determine the relationship between demyelination and neurological signs. Neither inflammation nor demyelination was present on the day prior to the onset of neurological signs but both were present in the spinal roots and spinal cord on the day of onset of tail weakness (4 days after passive transfer). Demyelination and the neurological signs both increased over the next 48 h. There was evidence that the caudal roots were more severely affected than the rostral roots. The peripheral nerves were spared. Demyelination in the spinal cord was concentrated in the dorsal root entry and ventral root exit zones. The initial stages of repair of demyelinated spinal root fibres by Schwann cells were observed on the earliest day that clinical recovery commenced (day 7). At this time some demyelinated fibres were closely associated with debris-free Schwann cells, and occasional fibres were completely invested by 1-2 layers of Schwann cell cytoplasm. Remyelination (compact myelin lamellae formation) by Schwann cells was first observed in the spinal roots on day 9. By the time of complete clinical recovery (day 11) the majority of affected spinal root cores had thin new myelin sheaths. Repair of central nervous system myelin by oligodendrocytes was slower than peripheral nervous system myelin repair. Investment of demyelinated spinal cord axons by oligodendrocytes was observed on day 9, and remyelination by these cells was seen on day 10. We conclude that the neurological signs of passively induced MBP-EAE can be accounted for by demyelination of the lumbar, sacral and coccygeal spinal roots and spinal cord root entry and exit zones, and that the subsequent clinical recovery can be explained by investment and remyelination of demyelinated peripheral and central nervous system fibres by Schwann cells and oligodendrocytes respectively.

PHA activation of encephalitogenic T cells: in vitro line selection overcomes splenic suppression

In this study we compared myelin basic protein (MBP) and phytohemagglutinin (PHA) for their ability to induce proliferation and experimental autoimmune encephalomyelitis (EAE) transfer activity in mixed cell cultures obtained from spleen and lymph nodes versus highly selected MBP-specific T cell lines and clones. Established MBP-specific cells derived initially from immune lymph nodes attained both proliferative and EAE-transfer activities after in vitro activation with either MBP or PHA. In contrast, PHA was unable to induce immune spleen cells to transfer EAE, in spite of its potent mitogenic activity. On the basis of these results, we evaluated the in vitro proliferation and differentiation responses of MBP-specific T cells during the line selection process using cells derived from both immune lymph node and immune spleen. During the initial selection process with MBP, proliferation of MBP-specific T cell precursors from immunized spleen populations was reduced relative to lymph node cells. After antigen-dependent selection the encephalitogenic cells from either organ exhibited identical in vitro response characteristics. Freshly isolated immune spleen cells were potent suppressors of MBP-specific T cell proliferation suggesting that the in vitro differences between the two organs was due to splenic suppression of the encephalitogenic cells.

Human T lymphocyte response to myelin basic protein: selection of T lymphocyte lines from MBP-responsive donors

The goal of this study was to delineate the importance of blood T lymphocyte responses to several myelin basic protein (MBP) preparations in the ultimate selection of MBP-specific T lymphocyte lines. Proliferation responses to human myelin basic protein (MBP) were assessed in blood samples from 27 multiple sclerosis (MS) patients, 20 patients with other neurologic diseases (OND), and 26 normal subjects, using five MBP preparations with different histories and electrophoretic characteristics to enhance the spectrum of epitopes represented. Substantial variations were observed in the ability of different MBP preparations to induce blood T cell proliferation in a given donor. However, four out of five of the MBPs induced modest but significant proliferation in the MS study population relative to normal individuals, with intermediate responses occurring in OND patients. Positive responses occurred more frequently in MS patients (78%) than in normal donors (31%), and were an important prerequisite for the successful selection of MBP-specific T cell lines.

Lymphocyte vaccination against experimental autoimmune encephalomyelitis: evaluation of vaccination protocols

Repeated vaccination with encephalitogenic but not other T cell lines could effect marked resistance to 'active' experimental autoimmune encephalomyelitis (EAE) induced by injection of GP-BP in adjuvant. Partial resistance to active EAE was observed in rats recovered from 'passive' line-mediated EAE and in rats vaccinated with T cells attenuated by irradiation or ganglioside treatment. However, no resistance was observed in animals given low doses of activated encephalitogenic T cells. Treatment with hydrostatic pressure alone was found to be ineffective as a means of attenuation, and vaccination with pressure-treated encephalitogenic T cells actually induced mild signs of EAE. However, vaccination with cells that were first pressure treated and then irradiated prevented both clinical and histologic signs of active EAE. In contrast, protection against passive EAE appeared to be clonotypic. Lymphocyte vaccination induced delayed type hypersensitivity (DTH) reactions against autologous T cells, mostly to shared antigens, demonstrating the immunogenicity of multiple antigens on the vaccinating cells.

Regulatory circuits in autoimmunity: recruitment of counter-regulatory CD8+ T cells by encephalitogenic CD4+ T line cells

In this study, pretreatment of Lewis rats with a syngeneic encephalitogenic T cell line (S1) was found to be able to constantly induce resistance to the subsequent induction of transferred experimental autoimmune encephalomyelitis (tEAE). This treatment was capable of protecting recipient animals for at least 2-4 months. Here we show an enhanced suppressor T(anti-S1) cell activity, which can be readily detected in the lymphoid organs of animals which recovered from S1-induced tEAE, or from rats pretreated with attenuated (irradiated, fixative treated or water-lysed) S1 cells. Anti-S1 cells, which uniformly express the CD8 phenotype, were selectively stimulated to grow and expand into lines by confronting primed lymphoid cells with irradiated S1 cells in culture. The proliferative response of anti-S1 cells was independent of myelin basic protein and antigen-presenting cells, and the responses against unrelated encephalitogenic T cell lines were minimal. It was also found that none of the monoclonal antibodies tested (including CD8 and MHC class I antigen-specific antibodies) was able to block S1/anti-S1 interactions. These cells are functionally suppressive to the proliferation of S1 cells in vitro, are specifically cytolytic directed against the EAE-inducing S1 cells and are able to antagonize encephalitogenic capacity of S1 cells in vivo. In vivo elimination of the CD8+ T subset from Lewis rats, using a combined treatment of thymectomy and OX-8 antibody injection before the initial cell transfer, totally blocked the induction of resistance. Our experiments document that induction of functionally active suppressor T cells is responsible for the induced resistance observed in tEAE.

Cytotoxic effect of myelin basic protein-reactive T cells on cultured oligodendrocytes

To help clarify effector mechanisms in experimental allergic encephalitis (EAE), the cytotoxic effects of myelin basic protein (MBP)-reactive lymphocytes on oligodendrocytes were studied using a 51Cr release assay. MBP-reactive encephalitogenic T cell lines were cytotoxic to 51Cr-labeled oligodendrocyte target cells derived from Lewis rat fetal brain-dissociated culture, when incubated for 6 h in the presence of antigen-presenting cells (APC) and MBP (percent 51Cr release = 65 +/- 3% vs. spontaneous release = 22 +/- 3% vs. normal lymph node cells + APC and MBP = 20 +/- 3%). This reaction is time dependent, likely MHC restricted, and is not just a nonspecific toxic effect against any Lewis target cells since neither fibroblasts nor astrocytes were affected. Other (tetanus toxoid-reactive) lymphoblasts stimulated by specific antigen were not cytotoxic to the oligodendrocytes. These findings suggest that oligodendrocytes might be target cells for MBP-reactive lymphocytes in EAE if antigen presentation is appropriate.

Basic protein-specific T-cell lines that induce experimental autoimmune encephalomyelitis in SJL/J mice: comparison with Lewis rat lines

Myelin basic protein (BP)-specific T-cell lines were selected from SJL/J mice using techniques to select similar lines from Lewis rats. SJL/J BP-specific T-cell lines were composed of T cells with the helper/inducer phenotype (Lyt 1.2+, 2.2- and L3T4+) and proliferated in response to both the 1-37 and the 89-169 fragments of guinea pig BP. BP-specific T-cell lines transferred delayed-type hypersensitivity (DTH) responses to BP that persisted for over 60 days. Most recipient animals (32/41) developed acute experimental autoimmune encephalomyelitis (EAE), and most survivors (19/24) developed chronic relapsing EAE. Spinal cords of animals during both the acute and the chronic phases of illness contained plaques of demyelination and infiltrates of lymphocytes and macrophages. These findings differed from those of Lewis rat BP-specific lines which respond to a different region of BP, transfer DTH responses that last less than 12 days, and induce acute EAE in which demyelination does not occur.

Perivascular microglial cells of the CNS are bone marrow-derived and present antigen in vivo

A crucial question in the study of immunological reactions in the central nervous system (CNS) concerns the identity of the parenchymal cells that function as the antigen-presenting cells in that organ. Rat bone marrow chimeras and encephalitogenic, major histocompatability--restricted T-helper lymphocytes were used to show that a subset of endogenous CNS cells, commonly termed "perivascular microglial cells," is bone marrow-derived. In addition, these perivascular cells are fully competent to present antigen to lymphocytes in an appropriately restricted manner. These findings are important for bone marrow transplantation and for neuroimmunological diseases such as multiple sclerosis.