Neutralizing antibodies to IL-18 ameliorate experimental autoimmune neuritis by counter-regulation of autoreactive Th1 responses to peripheral myelin antigen

Experimental autoimmune neuritis (EAN) is a demyelinating disease of the peripheral nervous system (PNS). This acute inflammatory disease is mediated by CD4+ T cells and bears significant similarities to the Guillain-Barré syndrome of humans. In the present study, we investigated the function of IL-18 in T cell-mediated autoimmunity of EAN in mice induced by P0 peptide 180-199 and Freund's complete adjuvant. Our data indicate that in 2 different therapeutic regimens, anti-IL-18 monoclonal antibody (mAb) effectively ameliorates the clinical and pathological signs of EAN. The suppression is associated with reduced inflammatory cell infiltration into the PNS and an insufficiency of autoreactive Th1 cells, as reflected by a reduced mononuclear cell proliferation and IFN-gamma-secretion in the spleen. Increased numbers of IL-4 expressing cells and decreased numbers of IFN-gamma and TNF-alpha expressing cells were found in the PNS. Our results suggest that shifting the Th1/Th2 balance towards Th2 cells may be one mechanism underlying EAN suppression by anti-IL-18 mAb. In addition, anti-IL-18 mAb treatment reduced anti-P0 peptide 180-199 autoantibody responses, which may also contribute to EAN suppression. We conclude that endogenous IL-18 plays a critical role in the pathogenesis of autoimmune demyelinating disease of the PNS and that IL-18 antagonists may provide a new therapy for these diseases.     

Resistance and susceptibility to experimental autoimmune neuritis in Sprague-Dawley and Lewis rats correlate with different levels of autoreactive T and B cell responses to myelin antigens

Experimental autoimmune neuritis (EAN) is a CD4⁺ T cell-mediated, inflammatory demyelinating disease of the peripheral nervous system (PNS) that serves as a model for Guillain-Barré syndrome (GBS) in humans. Various mouse and rat strains show different susceptibilities to EAN that can be induced by immunization with bovine PNS myelin (BPM) + Freund's complete adjuvant (FCA). We examined PNS-induced T and B cell responses and cytokine protein production as well as mRNA expression to study the mechanisms behind susceptibility to EAN in Lewis rats and resistance in Sprague-Dawley (SD) rats. Lewis rats with EAN have elevated PNS myelin-reactive interferon-γ (IFN-γ) production, TNF-α mRNA expression, and increased B cell responses to PNS myelin antigens, but low PNS myelin-reactive transforming growth factor-β (TGF-β) and interleukin (IL)-10 mRNA expression in lymph node mononuclear cells (MNC). In contrast, resistance to EAN in SD rats is associated with reduced BPM and P2 peptide-reactive IFN-γ production, TNF-α mRNA expression, and suppressed B cell responses to PNS myelin antigens as well as up-regulation of TGF-β and IL-10 mRNA expression. Resistance to EAN is also associated with low-grade inflammation or absence of histological evidence of EAN. These results suggest that differential autoreactive T and B cells responses to PNS myelin antigens are strain specific, and the susceptibility to EAN is related to quantitative rather than qualitative differences in distribution between pro-inflammatory and anti-inflammatory cytokines. J. Neurosci. Res. 54:373–381, 1998. © 1998 Wiley-Liss, Inc.     

T cell responses to myelin basic protein in experimental autoimmune encephalomyelitis-resistant BALB/c mice

In strains of mice that are susceptible to experimental autoimmune encephalomyelitis (EAE), cloned CD4⁺ T cells reactive with autologous myelin basic protein (MBP) have been shown to cause disease when transferred to naive syngeneic recipients. Recent reports indicate that under particular experimental conditions, ‘resistant’ strains of mice can also develop EAE, although cloned cells have not been isolated and characterized. An analyis of the characteristics of a panel of MBP-specific T cells and the antigen presenting capability of CNS-derived cells obtained from the resistant strain BALB/c is presented here. The data demonnstrate that immunization of EAE-resistant BALB/c mice results in the activation of a heterogeneous group of T cells reactive with autologous MBP. Both peripheral antigen presenting cells, as well as microglia isolated from brains of BALB/c mice, are capable of stimulating these cloned MBP-specific T cells to proliferate. When optimally activated in vitro and then injected in vivo into syngeneic BALB/c recipients, three clones studied induced severe cachexia, resulting in loss of up to 35% of body weight before death. Two of the clones also induced clinical and histological EAE, while the third induced only occasional histological evidence of disease. Differences in epitope recognition, T cell receptor usage, cytokine profiles or regulatory mechanisms of self tolerance, may play important roles in preventing potentially destructive autoimmune reactions by these T cells capable of recognizing autologous myelin in the central nervous system.     

Differential susceptibility to experimental autoimmune neuritis in Lewis rat strains is associated with T-cell immunity to myelin antigens

Experimental autoimmune neuritis (EAN) is a CD4(+) T-cell-mediated inflammatory demyelinating disease of the peripheral nervous system (PNS) that serves as a model for Guillain-Barré syndrome (GBS) in humans. Various rat strains show different susceptibility to EAN. We examined PNS myelin-induced T- and B-cell responses and cytokine production in order to explore the mechanisms behind different EAN susceptibility in the three Lewis rat strains, Hannover, Charles River, and Taconic. Lewis rats of Hannover and Charles River strains exhibited a higher susceptibility to EAN than Lewis rats of the Taconic strain. The higher susceptibility was associated with increased inflammatory cell infiltrates and major histocompatibility class II expression as well as enhanced mitogenic (phytohemagglutinin-induced) and antigen-specific (P2 peptide 57-81-induced) lymphocyte proliferation compared with the Taconic strain. The Hannover strain also showed increased proinflammatory cytokine (interferon-γ and tumor necrosis factor-α) production in the PNS. Cross-cultures of T cells and macrophages from Hannover and Taconic rats revealed that the Hannover rats exerted the strongest priming function of T cells. In contract, the P2 peptide-induced antibody production was not different among the three Lewis rat strains. In conclusion, the differential susceptibility to EAN of Lewis rat strains is correlated primarily with T-cell immunity to myelin antigens.     

T cell vaccination does not induce resistance to experimental autoimmune neuritis.

The effectiveness of T cell vaccination was analyzed in experimental autoimmune neuritis (EAN) that can be induced by immunization with bovine P2 protein or a peptide representing the amino acids 53-78 of P2 (P2 53-78). Lewis rats were vaccinated with glutaraldehyde-fixed lymph node cells which had been primed in vivo with P2 protein or P2 53-78 and had been activated in vitro with concanavalin A. Vaccinated animals were not protected from EAN induced by immunization with P2 protein in complete Freund's adjuvant (CFA). In a second set of experiments Lewis rats were vaccinated with irradiated or fixed P2-specific T cell lines of different specificity and neuritogenicity and were subsequently challenged with P2 53-78 in CFA. Likewise, severity of P2 53-78-induced EAN was not different between naive and T line-vaccinated groups. In spleens of vaccinated animals a substantial suppressive activity was demonstrated which was positively correlated with a weak anti-ergotypic response of these spleen cells. The fact that development of actively induced EAN was not prevented or even mitigated by T cell vaccination, in spite of an apparent vaccination-induced response to and on T lymphocytes, suggests that protection from disease is not readily induced in every autoimmune disease model.     

Response of the axon and barrier endothelium to experimental allergic neuritis induced by autoreactive T cell lines

Summary Experimental allergic neuritis was induced in Lewis rats by inoculation with autoreactive T cell lines senisitized to residue 57–81 of P₂ myelin protein. Control rats received cells derived from immunization to complete Freund's adjuvant alone. Endoneurial fluid pressure (EFP) was measured in both sciatic nerves at 0, 3, 5, 7, 9, and 11 days post-inoculation (PI). The temporal evolution of inflammatory disease was studied by correlating EFP with a morphometric analysis of the nerve microenvironment and with electron microscopic observations. Both edema, as evidenced by increased endoneurial extracellular space, and inflammation paralleled the time course of the EFP increase, reaching peak values at 7 days PI and declining to near-normal values after 11 days. Wallerian degeneration was detectable at 7 days and increased 9 days after inoculation. Axonal damage appeared at the height of the inflammatory process, when edema and increased EFP were maximal. Evidence of demyelination was apparent by 7 days and persisted through 11 days. The onset of edema was associated with changes in venular endothelial cells which tended to lose their normal scaphoid appearance and assumed rhomboid configurations reminiscent of high endothelial venules. At that point, the barrier endothelium was visibly disrupted with the loss of tight junctions and separation of adjacent cells. Specific cell-cell interactions took place between endothelial cells and infiltrating leukocytes as they immigrated into the endoneurial compartment. There was evidence of altered perineurial permeability with fibrin deposition and leukocyte infiltration between the layers of the perineurial sheath.Supported in part by NIH grants NS11867, NS14162, NS18715, the Juvenile Diabetes Foundation International and the Veterans Administration Research Service     

Glucocorticosteroids modulate antigen-induced T cell apoptosis in experimental autoimmune neuritis and cause T cell proliferation in situ

Treatment of experimental autoimmune disorders of the nervous system with high doses of glucocorticosteroids (GC) or with administration of the specific antigen is effective and associated with marked T cell apoptosis in situ. Here we investigated in adoptive transfer-experimental autoimmune neuritis (AT-EAN) of the Lewis rat whether induction of T cell apoptosis resulting from T cell activation by antigen therapy can be further augmented by glucocorticosteroids (GC). AT-EAN was induced by intravenous injection of P2-specific T cell blasts. At the maximum of disease two pulses of the antigen recombinant human P2 (rhP2) were given within 12 h. Methylprednisolone was administered simultaneously or 2 h after the antigen and animals were killed 6 h after the second antigen injection. Using an in situ tailing technique followed by immunocytochemical analysis, the presence of DNA fragmentation in T lymphocytes was confirmed. The bromodeoxyuridine (BrdU) technique was employed to detect in situ proliferating cells. T cell apoptosis in sciatic nerve was enhanced after monotherapy with either antigen or GC compared to the control group receiving an irrelevant myelin protein, recombinant human P0. In combination therapy, a synergistic effect on T cell apoptosis in sciatic nerve was obtained when methylprednisolone was injected sequentially, 2 h after rhP2 protein. BrdU incorporation in the sciatic nerve as well as in the spleen, a major lymphoid organ, was significantly enhanced in animals treated with antigen followed by GC 2 h later as compared to rats receiving rhP2 only, speaking for T cell proliferation in situ associated with T cells undergoing apoptosis. Our findings underscore that different proapoptotic stimuli may act synergistically, depending on the timing of the second treatment. In this scenario even local T cell proliferation in the inflamed nervous system occurs. These results support the paradigm of antigen presentation in the nervous system.     

Oestrogen treatment reduces duration of experimental allergic neuritis in rats and suppresses T cell responses to myelin

The effects of oestrogen and pregnancy on the disease course of experimental allergic neuritis (EAN) in rats were investigated. Pregnant rats were totally protected from EAN and long term 17-beta-oestradiol treatment significantly shortened the disease duration. Lymph node cells from oestrogen treated rats had a suppressed proliferative response when stimulated with myelin or PPD, both when the response was measured immediately after cell preparation and after 72 h cell culture in vitro. Serum levels of IgG antibodies against myelin, P2 or PPD did not differ between treated and non-treated rats although oestrogen treated rats had significantly higher levels of total IgG. Immunohistochemical stainings of nerve roots showed less intensive invasion of T lymphocytes in the oestrogen treated group while immunoreactivity to both class I and II major histocompatibility complex antigens did not differ in between the groups. These findings show that oestrogen ameliorates EAN and suggest that this effect is mediated by suppression of T cell dependent immunity. Factors in addition to oestrogen may be operative during pregnancy when a total protection from EAN is obtained.     

In situ demonstration of T cell activation and elimination in the peripheral nervous system during experimental autoimmune neuritis in the Lewis rat

The mechanisms of activation and termination of autoimmune responses are poorly understood. We have studied the sites and mode of activation and elimination of T cells in actively induced experimental autoimmune neuritis (EAN) and in EAN adoptively transferred by P2-specific T cells (AT-EAN). The bromodeoxyuridine (BrdU) technique was employed to detect in situ proliferating cells in spleen and sciatic nerve. We assessed the nuclear morphology of infiltrating T cells using morphological criteria of apoptotic cell death. Apoptosis of lymphoid cells was also investigated using molecular labeling techniques. In AT-EAN, the number of BrdU-positive cells in splenic germinal centers peaked at day 2 after cell transfer [554 ± 267 (mean ± SEM) per mm²; controls 98 ± 35), 1 day before disease onset, and declined thereafter. BrdU incorporation in spleens from animals with active EAN peaked at day 11, around disease onset, but reached lower total values (165 ± 29 per mm²). In neither model did we observe a significant proportion of BrdU-positive T cells in the peripheral nervous system. However, T cells exhibiting morphological signs of apoptosis were detected in the sciatic nerve immediately after disease onset. The number of these cells was highest on day 7 in AT-EAN (6.6 ± 3.2 per mm²) and on day 17 in active EAN (11.2 ± 2.2 per mm²), corresponding to the maximum of T cell infiltration in both animal models. T cell activation occurs systemically and not just in the autoimmune lesion. Infiltrating T cells are eliminated by apoptosis in situ, terminating the inflammatory process. Further insight into these mechanisms may help to develop new therapeutic strategies for autoimmune disorders of the peripheral nervous system. Received: 21 July 1995 / Revised, accepted: 31 October 1995     

Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) blockade enhances incidence and severity of experimental autoimmune neuritis in resistant mice

Experimental autoimmune neuritis (EAN), an autoimmune inflammatory demyelinating disease of the peripheral nervous system, represents an animal model of the human Guillain-Barré syndrome. EAN can be induced by active immunization in several animals, including Lewis rats. In contrast, most strains of mice including the widely used C57BL/6 (B6) strain are reputedly resistant to the induction of EAN. In the present study, we demonstrate that in B6 mice, anti-CTLA-4 monoclonal antibody administration in conjunction with immunization with the P0 protein derived peptide 180-199 can induce clinical and pathological definite EAN. Upregulating effects of CTLA-4 blockade on initial and ongoing EAN are demonstrated. CTLA-4 blockade augmented cellular infiltration and enhanced demyelination in the target organ sciatic nerves as well as increased T cell proliferation in lymph node cells. Moreover, serum levels of IFN-gamma and IL-4 were increased. Thus, manipulation of CTLA-4/B7 costimulatory pathway by CTLA-4 blockade can promote autoreactivity and break the relative tolerance to peripheral autoantigen P0 in resistant B6 mice.     

Dominance of autoreactive T cell-mediated delayed-type hypersensitivity or antibody-mediated demyelination results in distinct forms of experimental autoimmune neuritis in the Lewis rat

The role of anti-myelin antibodies in the pathogenesis of experimental autoimmune neuritis (EAN) induced in the Lewis rat by immunization with peripheral nerve myelin has been assessed. Passive transfer with lymph node cells (LNC) or purified serum immunoglobulin from rats with EAN was employed to directly measure the contribution of B cells and anti-myelin antibodies to demyelination and disease. Lewis rats with EAN transferred by LNC or purified serum immunoglobulin from EAN donors in conjunction with a low dose of P2-specific CD4+ T cells demonstrated profound histopathological and neurophysiological evidence of demyelination during disease. In contrast, the classical adoptive transfer model of EAN in the Lewis rat induced by the injection of P2-specific CD4+ T cells was characterized by histopathological and neurophysiological evidence of axonal dysfunction and degeneration with limited demyelination. These findings demonstrate that the synergistic action of T cells and anti-myelin antibodies mediating demyelination or purely T cell mediated axonal dysfunction and degeneration are distinct pathways by which a specific autoimmune response in the peripheral nervous system can cause neurological disease.     

Th1-like cell responses to peripheral nerve myelin components over the course of experimental allergic neuritis in Lewis rats

Experimental allergic neuritis (EAN) is a T cell-mediated animal model of Guillain-Barré syndrome characterized by inflammation and demyelination of peripheral nerves. EAN can be induced by immunization of rats with bovine peripheral nerve myelin (BPM) or the myelin proteins P2 or PO, but the extent of T cell responses over the course of EAN is incompletely defined. We studied the T cell responses to these proteins and the glycolipid GM1 by enumerating T helper type 1 (Th1)-like cells secreting interferon-γ (IFN-γ) after short-term culture of mononuclear cells (MNC) in presence of antigen. Already 7 days post immunization (p.i.) with BPM and before onset of clinical EAN, lymph nodes contained elevated levels of P2 responsive T cells. At the height of EAN on day 14 p.i. and during recovery, T cell levels responding to BPM, PO and GM1 were also elevated. The same temporal profiles and specificities were registered for antigen reactive spleen MNC. The results implicate that Th1-like cells with multiple specificities including the glycolipid GM1 occur at increased levels in lymphoid organs in EAN rats, and that IFN-γ may be an important effector molecule in the induction of nerve damage.     

Modulation of experimental autoimmune neuritis in Lewis rats by oral application of myelin antigens

Experimental autoimmune neuritis (EAN) in Lewis rats is a T cell-mediated disease and serves as an animal model of human inflammatory demyelinating neuropathies. EAN can be induced by immunization with complete bovine peripheral nerve myelin (BPM), the myelin protein P2 or its neuritogenic peptide, each emulsified in complete Freund's adjuvant (CFA). The present study evaluates the effect of oral tolerization with BPM or P2 protein on the development of actively induced EAN. Oral administration of BPM strongly suppressed clinical and histological signs of EAN subsequently induced by BPM/CFA, but feeding of P2 protein alone did not affect its course. In contrast, feeding of BPM did not mitigate the course of EAN subsequently induced by immunization with neuritogenic P2 peptide/CFA. Oral therapy with BPM after onset of myelin-induced EAN only slightly ameliorated the further course of disease, but significantly reduced lethality of this severe form of disease. The findings suggest that immunogenicity of the antigens fed determine strength of tolerance, that downregulation of EAN occurs at the site of immunization and not in the nerve, and that active suppression rather than specific anergization is operative in mediating resistance to EAN. However, only partial tolerance to myelin-induced EAN was achieved in naive animals by transfer of spleen/LN cells from rats orally tolerized with BPM. Although methodic factors may have limited the effect of the cells, the result is suggestive of some contribution of anergy to oral tolerance in the present model. Cholera toxin and LPS were identified as oral adjuvants for BPM and prolonged the state of tolerance. However, LPS exhibited proinflammatory properties if EAN was induced early after BPM/LPS-feeding. Thus, oral application of a mixture of myelin components in combination with cholera toxin may be a useful treatment for chronic inflammatory neuropathies considered autoimmune in nature.     

Contribution of resident endoneurial macrophages to the local cellular response in experimental autoimmune neuritis

Macrophages are intimately involved in the pathogenesis of inflammatory neuropathies. The contribution of resident endoneurial macrophages is unknown since their differentiation from infiltrating macrophages is difficult due to missing cellular markers. Previous studies demonstrated the participation of resident macrophages in Wallerian degeneration and the pathogenesis of hereditary neuropathies. The question arises whether resident macrophages are involved in experimental autoimmune neuritis (EAN) where they could contribute to immunosurveillance and antigen presentation. To address this question we used bone marrow chimeric rats, allowing the differentiation between resident and hematogenous cells. Immunohistochemistry and in situ hybridization were applied on to identify and characterize resident macrophages in terms of morphological features, expression of activation markers, proliferation, phagocytosis, and MHC-II expression. Endoneurial macrophages of resident origin were detectable at all stages of disease with a contribution of at least 27% of the total macrophages. They appeared activated by morphological and immunohistochemical criteria and proliferated early. MHC-II-positive resident macrophages were observed that had phagocytosed myelin. These results demonstrate that the macrophage response in EAN is partly of intrinsic origin. The rapid activation and proliferation of resident endoneurial macrophages points toward an active role of these cells in inflammatory peripheral nerve disease, especially early in disease.     

Reduced susceptibility of T cell-deficient rats to induction of experimental allergic neuritis

Lewis rats were made deficient in T cells by adult thymectomy and lethal irradiation, and then reconstituted with T cell-free bone marrow. Their ability to develop experimental allergic neuritis (EAN) was compared with normal rats. The majority of T cell-deficient rats remained clinically and histologically unaffected, whereas all but one of the normal rats developed severe EAN. Those T cell-deficient animals which succumbed to EAN were found to have a significantly higher percentage of residual blood T lymphocytes than those which did not. Full susceptibility to EAN was restored by an inoculum of whole thoracic duct lymphocytes (TDL) from normal animals but not by TDL depleted of T cells. The results therefore provide direct confirmation that T cells are a requirement for the development of EAN.     

Aggravation of experimental autoimmune neuritis in TNF-alpha receptor 1 deficient mice

The role of tumor necrosis factor (TNF)-alpha and its receptors in the pathogenesis of experimental autoimmune neuritis (EAN) induced by P0 peptide 180-199 in TNFR1 (p55) deficient (TNFR1-/-) mice was investigated. Compared to wild type EAN mice, TNFR1-/- EAN mice developed significantly more severe clinical signs, in parallel with enhanced numbers of inflammatory infiltrating cells in peripheral nerves and splenic P0-reactive T cell proliferation, as well as increased obviously MHC class II and CCR3 expression on the macrophages in the cauda equina. Our data indicated that TNF-alpha might have anti-inflammatory effect preventing the development of EAN in this mouse model.     

Cytokines in neuroinflammatory disease: role of myelin autoreactive T cell production of interferon-gamma

Many cytokines must be considered as effector and immunoregulatory molecules in neuroinflammatory diseases such as multiple sclerosis (MS) and experimental allergic encephalomyelitis (EAE). We have studied the potential role of interferon-gamma (IFN-γ) in the pathogenesis of these diseases, since this cytokine has a number of important effects such as macrophage activation, induction of MHC class I and class I antigens, and T cell homing. An immunospot assay that allows enumeration of single cells secreting IFN-γ after short-term culture in vitro of mononuclear cell suspensions has been used. In EAE, increased numbers of IFN-γ-secreting cells (IFN-γ-sc) appear in the central nervous system shortly before onset of clinical signs. Such cells also increased during pharmacologically induced relapse of EAE. In later stages of EAE, memory T cells that produced IFN-γ in response to presented antigen, recognized multiple regions of the myelin basic protein (MBP), showing that (i) myelin autoreactive T cells have the functional ability to produce this cytokine, (ii) the concept of immunodominance as to autoantigen peptide reactivity is non-absolute and time-dependent. In multiple sclerosis (MS) there are increased numbers of IFN-γ-sc among the CSF cells. Also, there are increased numbers of memory T cells, strongly enriched to the cerebrospinal fluid, which upon recognition of several myelin antigens and several MBP peptide stretches, produce IFN-γ. Taken together, the data are consistent with a role for IFN-γ as a key mediator in inflammatory demyelinating diseases.     

Increased phosphorylation of caveolin-1 in the sciatic nerves of Lewis rats with experimental autoimmune neuritis

The levels of phosphorylated caveolin-1 (p-caveolin-1) were analyzed in the sciatic nerves of Lewis rats with experimental autoimmune neuritis (EAN). Western blot analysis showed that the phosphorylation of caveolin-1 increased significantly in the sciatic nerves of EAN-affected rats at the paralytic stage of EAN on day 14 post-immunization (PI) (P<0.05) and declined slightly thereafter during the recovery stage. Immunohistochemistry showed intense p-caveolin-1 immunostaining in some inflammatory macrophages, as well as in T-cells in individual nerve fascicles at the peak stage of EAN, while p-caveolin-1 was weakly expressed in some of the vascular endothelial cells and Schwann cells of normal sciatic nerves. The inflammatory cells with intense p-caveolin-1 expression in the EAN-affected individual nerve fascicles were not positive for terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL), while the TUNEL-positive apoptotic cells in the perineurium, where infiltration initially occurred, were weakly positive for p-caveolin-1. Based on these findings, we postulate that caveolin-1 is phosphorylated in inflammatory cells soon after they infiltrate the sciatic nerve, as well as in the perineurium, and that p-caveolin-1 activates intracellular signaling in inflammatory cells, leading to cell death, which ultimately eliminates the infiltrating inflammatory cells from the sciatic nerves of animals with EAN.     

Sulfasalizine aggravates experimental autoimmune encephalomyelitis and causes an increase in the number of autoreactive T cells

Sulfasalazine (SASP; 5-(p-(2-pyridylsulfamoyl)phenylazo)salicylic acid) has beneficial effects on certain inflammatory diseases and has been proposed for clinical trials in multiple sclerosis (MS). We have explored the effects of SASP on actively induced experimental autoimmune encephalomyelitis (EAE) in Lewis rats. SASP was given orally at three different doses from the day of immunization to day 40 post-immunization (p.i.). All doses led to a clinically more protracted disease, increased numbers of T cells infiltrating into the central nervous system (CNS) and to increased numbers of interferon-γ-secreting cells (IFN-γ-sc) in the CNS. The effects of SASP treatment on T cell-mediated autoimmunity against CNS myelin and peptides of myelin basic protein (MBP) were measured by IFN-γ secretion and proliferation by lymph node mononuclear cells in response to these antigens. In SASP-treated rats, increased numbers of IFN-γ-sc appeared in response to myelin antigens, while the proliferative responses were decreased. We suggest that monitoring cell-mediated immunity with the IFN-γ-sc method may be relevant for the evaluation of new immunotherapeutic strategies in flammatory demyelinating diseases. Furthermore, our results demand caution as to clinical trials with SASP in MS.     

Mice devoid of Tau have increased susceptibility to neuronal damage in myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis

The abundant axonal microtubule-associated protein tau regulates microtubule and actin dynamics, thereby contributing to normal neuronal function. We examined whether mice deficient in tau (Tau(-/-)) or with high levels of human tau differ from wild-type (WT) mice in their susceptibility to neuroaxonal injury in experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis. After sensitization with MOG35-55, there was no difference in clinical disease course between human tau and WT mice, but Tau mice had more severe clinical disease and significantly more axonal damage in spinal cord white matter than those in WT mice. Axonal damage in gray matter correlated with clinical severity in individual mice. By immunoblot analysis, the early microtubule-associated protein-1b was increased 2-fold in the spinal cords of Tau mice with chronic experimental autoimmune encephalomyelitis versus naive Tau mice. This difference was not detected in comparable WT animals, which suggests that there was compensation for the loss of tau in the deficient mice. In addition, levels of the growth arrest-specific protein 7b, a tau-binding protein that is stabilized when bound to tau, were higher in WT than those in Tau(-/-) spinal cord samples. These data indicate that loss of tau exacerbates experimental autoimmune encephalomyelitis and suggest that maintaining tau integrity might reduce the axonal damage that occurs in inflammatory neurodegenerative diseases such as multiple sclerosis.