Cytapheresis with a filter for selective removal of CD4+ T cells in experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is a major animal model of human multiple sclerosis (MS). CD4+ T cells are thought to play a pivotal role in the pathogenesis of EAE and MS. In order to investigate the depletion of CD4+ T cells from the systemic circulation as an effective strategy for the treatment of MS, we performed extracorporeal CD4+ T cell adsorption, using a filter to which anti-CD4+ antibody is immobilized as a ligand, in adoptively transferred EAE. Rats treated with CD4+ T cell removal filter (CD4RF) exhibited milder clinical signs of EAE and earlier recovery than those receiving sham treatment. Moreover, the thymic cells from EAE rats treated with CD4RF exhibited a suppressed proliferative response and IFN-gamma production to myelin basic protein. These results suggest that depletion of CD4+ T cells from the systemic circulation by extracorporeal treatment is a potentially useful strategy for treatment of acute phase and relapsing MS.     

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.     

Memory cells specific for myelin oligodendrocyte glycoprotein (MOG) govern the transfer of experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is an inflammatory disease of the CNS mediated by CD4(+) T cells directed against myelin antigens. Experimental autoimmune encephalomyelitis (EAE) is induced by immunization with myelin antigens like myelin oligodendrocyte glycoprotein (MOG). We have explored the transfer of EAE using MOG(35-55)-specific TCR transgenic (2D2) T cells. Unsorted 2D2 Th1 cells reliably transferred EAE. Further, we found that CD44(hi)CD62L(lo) effector/memory CD4(+) T cells are likely responsible for the disease transfer due to the up-regulation of CD44. Given the importance of MOG in MS pathogenesis, mechanistic insights into adoptively transferred EAE by MOG-specific Th1 cells could prove valuable in MS research.     

Protection against experimental autoimmune encephalomyelitis requires both CD4 T suppressor cells and myelin basic protein-primed B cells

Suppressor cells that regulate experimental autoimmune encephalomyelitis (EAE) are present in rats that recover from the disease and can protect against the development of active EAE when transferred to normal recipients. Both CD4+ T suppressor cells, known to regulate EAE effector cell lymphokine production, and myelin basic protein (MBP)-primed B cells are required to transfer protection against EAE to normal recipients. Neither CD4+ T suppressor cells nor MBP-primed B cells alone could transfer protection. Moreover, the co-transfer of normal B cells with CD4+ T suppressor cells did not provide protection against EAE. These results suggest that the regulation of EAE and perhaps the recovery from acute clinical disease requires the interaction of two specific subpopulations of regulatory lymphocytes.     

Immunopathogenesis of multiple sclerosis: concepts and controversies

Hundred and fifty years after the discovery of multiple sclerosis (MS), neither the etiology nor the mechanism of disease is fully charted, and current treatment has only modest effect. The conceptual understanding of MS rests on the animal model experimental autoimmune encephalomyelitis (EAE). Based on 70 years experience with EAE, it is widely believed that MS is an inflammatory attack on myelin and neurons orchestrated by myelin specific T cells. However, evidence supporting a key role for myelin specific T cells in MS is weak, the model fails to explain how immune self-tolerance is broken, and the peculiar B cell response of MS is poorly reflected in EAE. The pathogenesis of MS should therefore be studied in tissue samples and cells from MS patients, as close to the diseased organ as possible. Studies on lymphocytes from CSF of MS patients suggest that viral infections may be involved in T cell activation, and that intrinsic collaboration between T and B cells could sustain the immune response. These observations could explain the perpetuating immune response in MS in the absence of an overt antigen.     

Anti-IL-16 therapy reduces CD4+ T-cell infiltration and improves paralysis and histopathology of relapsing EAE

Infiltration of the central nervous system (CNS) by CD4+ Th1 cells precedes onset and relapses of experimental autoimmune encephalomyelitis (EAE). We reported that (B6xSJL) F1 (H-2b/s) mice with severe relapsing-remitting disease had extensive infiltration by CD4+ T cells compared to that in C57BL/6 (B6) (H-2b) mice, which developed mild low-relapsing disease in response to myelin oligodendrocyte peptide 35-55 (MOG(35-55)). This observation led us to search for mechanisms that specifically regulate trafficking of CD4+ cells in relapsing H-2b/s mice. We show that the CD4+ cell chemoattractant cytokine interleukin (IL)-16 has an important role in regulation of relapsing EAE induced by MOG(35-55) in the (B6xSJL) F1 (H-2b/s) mice. We found production of IL-16 in the CNS of mice with EAE. IL-16 levels in the CNS correlated well with the extent of CD4+ T-cell and B-cell infiltration during acute and relapsing disease. Infiltrating CD4+ T cells, B cells, and to a lesser extent CD8+ T cells all contained IL-16 immunoreactivity. Treatment with neutralizing anti-IL-16 antibody successfully reversed paralysis and ameliorated relapsing disease. In treated mice, diminished infiltration by CD4+ T cells, less demyelination, and more sparing of axons was observed. Taken together, our results show an important role for IL-16 in regulation of relapsing EAE. We describe a novel therapeutic approach to specifically impede CD4+ T cell chemoattraction in EAE based on IL-16 neutralization. Our findings have high relevance for the development of new therapies for relapsing EAE and potentially MS.     

Synergy between encephalitogenic T cells and myelin basic protein-specific antibodies in the induction of experimental autoimmune encephalomyelitis.

Experimental autoimmune encephalomyelitis (EAE) is an experimentally induced demyelinating disease mediated by CD4+ T cells specific for various myelin proteins including myelin basic protein (MBP) and myelin proteolipid protein (PLP). Although myelin- and other CNS-specific antibodies are produced in EAE, B cells and antibodies are thought by most not to play a decisive role in the induction of EAE. In this report we show that B cells serve as the major antigen-presenting cells (APC) during the T cell activation stage in lymph nodes, and that MBP-specific antibodies can greatly enhance the induction of EAE. The role of B cells as APC is demonstrated in B cell-depleted mice. EAE cannot be induced by antigen/complete Freund's adjuvant immunization unless these mice are locally reconstituted with B cells prior to immunization. The enhancing effect of antibodies is demonstrated in experiments in which EAE is induced by the adoptive transfer of encephalitogenic T cells. The adoptive transfer of large numbers of encephalitogenic T cells induces EAE in 90% of normal recipient mice, but only 33% of B cell-depleted mice get EAE at the same cell dose. The efficiency of EAE induction in B cell-depleted mice can be enhanced if MBP-specific antibodies are simultaneously administered. A similar enhancement is also seen in normal mice when the number of adoptively transferred T cells is limiting. We propose that MBP-specific antibodies enhance the presentation of myelin-derived antigens by APC in the CNS to the adoptively transferred encephalitogenic T cells.     

The role of costimulation in autoimmune demyelination

Experimental allergic encephalomyelitis (EAE) is a T cell-mediated, autoimmune disorder characterized by central nervous system (CNS) inflammation and demyelination, features reminiscent of the human disease, multiple sclerosis (MS). In addition to the signal the encephalitogenic T cell receives through the T cell receptor (TCR), a second signal, termed costimulation, is required for complete T cell activation. The B7 family of cell surface molecules expressed on antigen presenting cells (APC) is capable of providing this second signal to T cells via two receptors, CD28 and CTLA-4. Our studies have shown that costimulation provided by B7 molecules to its ligand CD28 is important in the initiation of the autoimmune response in EAE. Further, it appears the costimulation provided by B7-1 is important in disease development, while B7-2 may play an important regulatory role. We and others later showed that B7/CTLA-4 interaction plays a critical role in down-regulating the immune response. Previous work has shown that activated T cells and T cells of a memory phenotype are less dependent on costimulation than naive T cells. T cells reactive with myelin components that are involved in the pathogenesis of EAE and possibly MS would be expected to have been activated as part of the disease process. Building upon our prior work in the EAE model, we have tested the hypothesis that myelin-reactive T cells, which are relevant to the pathogenesis of CNS inflammatory demyelination, can be distinguished from naive myelin-reactive T cells by a lack of dependence upon costimulation for activation and that the costimulatory requirements of these myelin-reactive T cells change during the course of disease. Our studies in the EAE model have also addressed the mechanisms of extrathymic (peripheral) T cell tolerance following intravenous (i.v. ) administration of high dose antigen. It is believed that TCR signaling in the absence of costimulation is a vital component of peripheral tolerance mechanisms. However, recent evidence suggests that peripheral tolerance of antigen-specific T cells induced in vivo may require CTLA-4 engagement of the tolerized T cells. We have begun to examine the molecular mechanisms of tolerance induction following intravenous and intraperitoneal administration of myelin antigens in the EAE model and test the hypothesis that tolerance induction is dependent on the B7:CD28/CTLA-4 pathway. The results from our studies will enhance our understanding of the role that myelin-reactive T cells may play in the pathogenesis of MS. We have determined that MBP-reactive T cells in MS patients are less dependent upon CD28 costimulation than in normal controls, suggesting that these T cells were previously primed in vivo. Characterization of these CD28-independent myelin-specific T cells will have broad implications for a variety of immunologically based therapies in diseases such as MS.     

CD8+ T cells in inflammatory demyelinating disease

We review the contribution made by CD8+ T cells to inflammation in the central nervous system (CNS) in Multiple Sclerosis (MS), and discuss their role in the animal model Experimental Autoimmune Encephalomyelitis (EAE). We show that the inflammatory cytokines interferon-gamma and interleukin-17 are differentially regulated in CNS-infiltrating CD4+ and CD8+ T cells in EAE, and that CD8+ T cells regulate disease. In MS, CD8+ T cells appear to play a role in promotion of disease, so cytokine regulation is likely different in CD8+ T cells in MS and EAE.     

Role of Fas--FasL interactions in the pathogenesis and regulation of autoimmune demyelinating disease

Multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE) represent complex processes that lead to destruction of oligodendrocytes (ODCs) and myelin. T cells are integral to the development of these diseases, but whether T cell-mediated cytolytic mechanisms are involved in the destruction of MHC Class II-negative targets, such as oligodendroglia and myelin, in the CNS is unclear. The primary lytic mechanism employed by CD4⁺ T cells is Fas-dependent, but can be MHC-unrestricted. Thus, T cell-mediated Fas–FasL interactions could directly contribute to the pathology of EAE and MS. This review summarizes studies from our laboratory and others that implicate Fas–FasL interactions in both the pathogenesis and regulation of demyelinating diseases.     

Vaccination with autoreactive T cell clones in multiple sclerosis: overview of immunological and clinical data

Although the etiology and pathogenesis of Multiple Sclerosis (MS) remain elusive, accumulating evidence indicates that MS is a chronic inflammatory disease with an autoimmune component, mediated by autore-active T lymphocytes specific for myelin antigens. The triggering T cell autoantigen has not been identified yet, but recent immunological studies in MS and parallel experiments in experimental allergic encephalomyelitis (EAE), the animal model of MS, have indicated that myelin basic protein (MBP) can be considered as one of the major candidate autoantigens in the pathogenesis of the disease. Based on these observations, several therapeutic strategies have been developed aimed at the specific elimination or inactivation of MBP reactive T cells in MS. One of these approaches involves the immunization of MS patients with autologous attenuated autoreactive T cells to induce an immune response specifically targeted at these autoreactive T cells. This method, termed T cell vaccination, has been shown to prevent and treat EAE. We have recently conducted a pilot trial of T cell vaccination in a limited group of MS patients to evaluate the immunological responses to the injected cells. The data obtained indicate that this type of vaccination induces an effective anti-clonotypic T cell response leading to a specific depletion of circulating MBP reactive T cells. Preliminary data on the clinical effects are promising, encouraging further clinical trials. © 1996 Wiley-Liss, Inc.     

Endogenous CD4+BV8S2- T cells from TG BV8S2+ donors confer complete protection against spontaneous experimental encephalomyelitis (Sp-EAE) in TCR transgenic,RAG-/- mice

To investigate regulatory mechanisms which naturally prevent autoimmune diseases, we adopted the genetically restricted immunodeficient (RAG‐1^?/?) myelin basic protein (MBP)‐specific T cell receptor (TCR) double transgenic (T/R?) mouse model of spontaneous experimental autoimmune encephalomyelitis (Sp‐EAE). Sp‐EAE can be prevented after transfer of CD4+splenocytes from naïve immunocompetent mice. RAG‐1+ double transgenic (T/R+) mice do not develop Sp‐EAE due to the presence of a very small population (about 2%) of non‐Tg TCR specificities. In this study, CD4+BV8S2+ T cells that predominate in T/R+ mice, and three additional populations, CD4+BV8S2?, CD4?CD8?BV8S2+, and CD4?CD8+BV8S2+ T cells that expanded in T/R+ mice after immunization with MBP‐Ac1‐11 peptide, were studied for their ability to prevent Sp‐EAE in T/R? mice. Only the CD4+BV8S2? T cell population conferred complete protection against Sp‐EAE, similar to unfractionated splenocytes from non‐Tg donors, whereas CD4?CD8?BV8S2+ and CD4+BV8S2+ T cells conferred partial protection. In contrast, CD4?CD8+BV8S2+ T cells had no significant protective effects. The highly protective CD4+BV8S2? subpopulation was CD25+, contained non‐clonotypic T cells, and uniquely expressed the CCR4 chemokine receptor. Protected recipient T/R? mice had marked increases in CD4+CD25+ Treg‐like cells, retention of the pathogenic T cell phenotype in the spleen, and markedly reduced inflammation in CNS tissue. Partially protective CD4+BV8S2+ and CD4? CD8?BV8S2+ subpopulations appeared to be mainly clonotypic T cells with altered functional properties. These three Sp‐EAE protective T cell subpopulations possessed distinctive properties and induced a variety of effects in T/R? recipients, thus implicating differing mechanisms of protection. © 2002 Wiley‐Liss, Inc.     

Bothanti-CD11a(LFA-l) and anti-CD11b (MAC-1) therapy delay the onset and diminish the severity of experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is a demyelinating disease of the central nervous system (CNS) induced in rodents by activated CD4⁺ T cells specific for various myelin proteins such as myelin basic protein and proteolipid protein. The disease is characterized by breach of the blood-brain barrier, perivascular infiltration of leukocytes into the CNS, local inflammation and demyelination in the form of plaques. In this study, we evaluated the effect of administration of antibodies to two members of the β2 integrin sub-family of adhesion molecules, CD11a and CD11b, on the onset and progression of EAE. CD11a and CD11b are involved in cell-cell interactions leading to T cell and macrophage extravasation to inflammatory sites and T cell activation. Our results show that anti-CD11a antibodies could completely block the induction of EAE and anti-CD11b antibodies significantly delayed the onset and diminished the severity of clinical signs of EAE even when injections were initiated at the first appearance of clinical signs.     

Candidate autoantigens in multiple sclerosis.

Multiple sclerosis is an inflammatory demyelinating CNS disease of putatively autoimmune origin. Novel models of experimental autoimmune encephalomyelitis (EAE) have demonstrated that T cells specific for various myelin and even nonmyelin proteins are potentially encephalitogenic. The encephalitogenic T cell response directed against different CNS antigens not only determines the lesional topography of CNS inflammation but also the composition of the inflammatory infiltrates. The heterogeneity of the lesional distribution seen in EAE might therefore be useful for the understanding of the various clinical subtypes seen in MS. In this review the possible candidate autoantigens in MS are discussed with special regard to the human T cell and B cell responses against various myelin and nonmyelin proteins.     

Dendritic cells exposed to estrogen in vitro exhibit therapeutic effects in ongoing experimental allergic encephalomyelitis

Immunomodulatory effects of estrogen have been demonstrated by clinical and experimental observations, but the mechanisms by which estrogen exhibits the effects remain to be defined. One possible mechanism by which estrogen inhibits the development of experimental allergic encephalomyelitis (EAE), a commonly used model of multiple sclerosis (MS) in humans, is over the functions of dendritic cells (DC). Here, we describe that splenic DC from Lewis rats obtained on day 12 post-immunization (p.i.) with myelin basic protein (MBP) encephalitogenic peptide 68-86+Freund's complete adjuvant (FCA), after being exposed in vitro 17beta-estradiol, exhibited therapeutic effects on acute EAE when injected subcutaneously on day 5 p.i. Blood mononuclear cells (MNC) were isolated from thus treated rats on day 12 p.i. Administration of estrogen-exposed DC prevented the expansion of CD4+ T cells and increased proportions of regulatory T cells producing IL-10 and CD4+CD28- suppressor T cells, accompanied with increased IL-10 and IFN-gamma, and reduced TNF-alpha production. Infiltrates of CD68+ macrophages within the central nervous system and MBP 68-86-induced T cell proliferation were inhibited in rats injected with estrogen-exposed DC compared to rats injected with naive DC. Estrogen up-regulated the expression of indoleamine 2,3-dioxygenase, which promotes tolerogenic properties of DC. The results suggest that in vitro exposure of DC to estrogen modulates DC functions and results in a therapeutic effect of DC.     

B-cell depletion abrogates T cell-mediated demyelination in an antibody-nondependent common marmoset experimental autoimmune encephalomyelitis model

CD20-positive B-cell depletion is a highly promising treatment for multiple sclerosis (MS), but the mechanisms underlying therapeutic effects are poorly understood. B cells are thought to contribute to MS pathogenesis by producing autoantibodies that amplify demyelination via opsonization of myelin. To analyze autoantibody-nondependent functions of B cells in an animal model of MS, we used a novel T cell-driven experimental autoimmune encephalomyelitis (EAE) model in marmoset monkeys (Callithrix jacchus). In this model, demyelination of brain and spinal cord white and gray matter and the ensuing neurological deficits are induced by immunization with peptide 34 to 56 of myelin/oligodendrocyte glycoprotein (MOG34-56) in incomplete Freund's adjuvant. Although autoantibodies do not have a detectable pathogeniccontribution in the model, depletion of B cells with monoclonal antibody 7D8, a human IgG1κ monoclonal antibody against human CD20, suppressed clinical and pathological EAE. In B cell-depleted monkeys, the activation of peptide-specific Th17-producing and cytotoxic T cells, which in previous studies were found to play an essential role in disease induction, was impaired. Thus, we demonstrate a critical antibody-nondependent role for B cells in EAE, that is, the activation of pathogenic T cells.     

B cells from glatiramer acetate-treated mice suppress experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS) thought to be primarily mediated by T cells. However, emerging evidence supports an important role for B cells in the pathogenesis and inhibition of MS. Glatiramer acetate (GA), a Food and Drug Administration-approved drug for the treatment of MS, has a good safety profile. But GA's mechanism of action in MS is still elusive. In this study, we showed that B cells from GA-treated mice increased production of IL-10 and reduced expression of co-stimulatory molecules viz.: CD80 and CD86. B cells from GA-treated mice also diminished proliferation of myelin oligodendrocyte glycoprotein (MOG_35-55) specific T cells. Purified B cells transferred from GA-treated mice suppressed experimental autoimmune encephalomyelitis (EAE) in recipient mice compared with B cells transferred from mice treated with PBS or ovalbumin. The treatment effect of GA in EAE was abrogated in B cell-deficient mice. Transfer of B cells from GA-treated mice inhibited the proliferation of autoreactive T cells as well as the development of Th1 and Th17 cells but promoted IL-10 production in recipient mice. The number of peripheral CD11b⁺ macrophages in recipient mice also decreased after transfer of B cells from GA-treated mice; however, the number of dendritic cells and regulatory T cells remained unaltered. These results suggest that B cells are important to the protective effects of GA in EAE.     

Mechanisms of recovery from experimental allergic encephalomyelitis induced with myelin basic protein peptide 68-86 in Lewis rats: a role for dendritic cells in inducing apoptosis of CD4+ T cells.

Spontaneous remission of experimental allergic encephalomyelitis (EAE) is usually associated with prominent apoptosis. The mechanisms behind apoptosis are unknown. We examined the functions of dendritic cells (DC) from Lewis rats with EAE induced by immunization with myelin basic protein peptide 68-86 (MBP68 - - 86). Recovery from EAE was associated with three major functional changes of freshly prepared DC: (1) elevated proliferation, (2) increased nitric oxide (NO) production, and (3) augmented IFN-gamma secretion. In Freund's complete adjuvant (FCA)-immunized control rats, no increase of proliferation, NO production or IFN-gamma secretion was observed on day 21 post-immunization (p.i.), i.e., recovery from EAE. In vitro effects of IFN-gamma, TNF-alpha, TGF-beta1, IL-4 and IL-10 on DC were examined. IFN-gamma enhanced proliferation and NO production by DC, while TNF-alpha and IL-4 induced only slight DC proliferation. DC from recovering EAE rats (day 21 p.i.) suppressed MBP68 - - 86-induced T cell proliferation compared to DC obtained at other time points in EAE and FCA-immunized rats. DC-derived NO induced apoptosis of CD4+ T cells, thereby inhibiting autoreactive T cell responses. Besides IFN-gamma stimulation, NO production by DC was mainly induced in an antigen-dependent manner when DC were co-cultured with T cells. The results suggest that spontaneous recovery from EAE is associated with augmented DC functions. Overproduction of NO by DC results in apoptosis of autoreactive CD4+ T cells, thereby decreasing autoreactive T cell reactivities. The existence of such a NO negative feedback loop may contribute to remission of EAE.     

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.     

Sequence 104–117 of myelin proteolipid protein is a cryptic encephalitogenic T cell determinant for SJL/J mice

Immunization of animals with myelin proteolipid protein (PLP) causes experimental autoimmune encephalomyelitis (EAE), a disease model that shares many features with human multiple sclerosis (MS). The SJL/J (H-2⁵) mouse is widely used in EAE studies because of its high disease susceptibility. Previous studies have shown that sequences 139–151 HCLGKWLGHPDKF and 178–191 NTWTTCQSIAFPSK represent distinct co-immunodominant encephalitogenic determinants of PLP for SJL/J mice. In the present study, we identify a third distinct PLP encephalitogenic peptide for SJL/J mice. Following immunization with PLP 104–117 KTTICGKGLSATVT, 10/14 SJL/J mice developed clinical and histological EAE with a mean time of onset of 38 days (18–65 days). T cell lines generated from SJL/J mice immunized with p104–117 were predominantly (> 90%) CD3⁺, CD4⁺, αβTCR⁺, CD8^dim, γδTCR^dim T cells and responded in an Ag-specific, I-As-restricted manner to p104–117. Upon adoptive transfer of 16−40 × 10⁶ T line cells, EAE was produced in naive SJL/J recipients 20–34 days after transfer. The delayed onset of both active and passive disease may be related to the non-immunodominant, cryptic nature of p104–117 in SJL/J mice. Lymph node cells from SJL/J mice immunized with either whole PLP or with pooled encephalitogenic PLP peptides responded to challenge with the immunodominant PLP determinants p139–151 and p178–191 but did not respond to p104–117. The existence of three distinct PLP encephalitogenic T cell determinants for SJL/J mice suggests that susceptibility to EAE and perhaps MS may be related to promiscuous T cell recognition of multiple myelin protein determinants.