Dendritic cells in experimental allergic encephalomyelitis and multiple sclerosis

The mechanisms by which autoimmune diseases are triggered and by which the activation of autoreactive T cells is initiated and maintained are not yet fully understood. As the most potent antigen presenting cells (APC), and also being responsible for antigen transport as well as primary sensitisation of T cells, dendritic cells (DC) are capable of breaking the state of self-ignorance and inducing aggressive autoreactive T cells. In the development of autoimmune diseases, different types of DC exhibit distinct properties for inducing Th1/Th2 cell responses. Appropriate cytokines can convert immunogenic DC to tolerogenic DC. Utilizing the possibility to promote the tolerogenic effects of DC, a new therapeutic tool might soon become available to treat multiple sclerosis and other autoimmune diseases.     

Suppression of experimental allergic encephalomyelitis in rats exposed nocturnally to magnetic fields.

After inoculation with spinal cord and complete Freund's adjuvant, female Lewis rats were exposed to weak, 7 Hz complex magnetic fields or to the control condition. The computer-generated magnetic field, whose amplitude varied from 15 nT to 60 nT every 6 to 12 sec, was presented for 6 min every hour between midnight and 0800 of the scotophase. In two replicates of the experiment, the rats exposed to the field displayed statistically significant suppression relative to sham-field controls (effect size = 55%) of the overt symptoms of experimental allergic encephalomyelitis which included hindleg paralyses.     

雌激素对实验性变态反应性脑脊髓炎大鼠发病影响的研究

目的探讨雌激素对实验性变态反应性脑脊髓炎(EAE)的影响。方法将30只大鼠随机分为EAE组及大、小剂量雌激素干预组,每组10只,制作EAE模型,大、小剂量雌激素干预组分别给予皮下注射苯甲酸雌二醇1 mg/kg/d、250μg/kg/d,连续10 d,观察各组的发病情况并采用HE染色观察脑和脊髓组织病理变化。结果大、小剂量雌激素干预组的临床症状均较EAE组轻,表现为发病率减少、潜伏期延长、进展期缩短、高峰期神经功能损害较轻。病理切片提示雌激素干预组脑和脊髓炎症细胞浸润明显减少,其中以大剂量组更明显。结论雌激素对多发性硬化动物模型EAE具有保护作用,且与剂量相关。     

Ia-expressing microglial cells in experimental allergic encephalomyelitis in rats

Summary Monoclonal antibodies (MRC OX-6 and OX-17) recognized three types of cells expressing Ia antigen during the course of acute experimental allergic encephalomyelitis (EAE) in rats. In earlier stages of the disease, in animals with or without paralysis, Ia antigens were mostly localized to subarachnoidal and perivascular lymphocytic and histiocytic cell infiltrates, possibly serving as antigen-presenting cells. On the other hand, in convalescent rats, Ia antigens were expressed in a large number of cells with dendritic processes heavily populating the spinal gray matter. The appearance of these Ia-expressing cells in the convalescent stage coincided with the development of degenerating axon terminals in the spinal gray matter. These Ia-expressing cells possessed morphological features characteristic of microglia and were positive for ML-1 lectin but did not express glial fibrillary acidic protein. Immune electron microscopy disclosed the presence of Ia reaction products in the Golgi apparatus, endoplasmic reticulum and plasma membrane of these cells with dendritic processes, indicating active synthesis of Ia molecules in microglia. In addition, Ia antigens were localized to the cells with ultrastructural features of macrophages. Thus, Ia-expressing cells in EAE seems to play dual roles: the induction of immunological reactions during earlier stages and the participation in reparative processes during convalescence.Supported by Grants-in-aid from the Ministry of Health and Welfare for Intractable Neuroimmunological Diseases and from the Ministry of Education, Science and Culture (Project 61570380 to HK)     

Neuroimmunoprotective effects of estrogen and derivatives in experimental autoimmune encephalomyelitis: therapeutic implications for multiple sclerosis

The extensive literature and the work from our laboratory illustrate the large number of complex processes affected by estrogen that might contribute to the striking ability of 17beta-estradiol (E2) and its derivatives to inhibit clinical and histological signs of experimental autoimmune encephalomyelitis (EAE) in mice. These effects require sustained exposure to relatively low doses of exogenous hormone and offer better protection when initiated prior to induction of EAE. However, oral ethinyl estradiol (EE) and fluasterone, which lacks estrogenic side effects, could partially reverse clinical EAE when given after the onset of disease. The three main areas discussed in this review include E2-mediated inhibition of encephalitogenic T cells, inhibition of cell migration into central nervous system tissue, and neuroprotective effects that promote axon and myelin survival. E2 effects on EAE were mediated through Esr1 (alpha receptor for E2) but not Esr2 (beta receptor for E2), as were its antiinflammatory and neuroprotective effects. A novel finding is that E2 up-regulated the expression of Foxp3 and CTLA-4 that contribute to the activity of CD4+CD25+ Treg cells. The protective effects of E2 in EAE suggest its use as therapy for MS, although the risk of cardiovascular disease may complicate treatment in postmenopausal women. This risk could be minimized by using subpregnancy levels of exogenous E2 that produced synergistic effects when used in combination another immunoregulatory therapy. Alternatively, one might envision using EE or fluasterone metabolites alone or in combination therapies in both male and female MS patients.     

Ameliorating effects of hyperbaric oxygenation on experimental allergic encephalomyelitis

The effect of hyperbaric oxygenation (OHP) on survival and quality of survival of guinea pigs afflicted with experimental allergic encephalomyelitis (EAE) was investigated. EAE was induced in Hartley and Strain 13 animals by intradermal injections of whole guinea pig spinal cord in complete Freund's adjuvant. The inoculated animals were divided into control and treatment groups; the treated animals received OHP in a variety of treatment schedules. Clinical signs of EAE were quantitated and mean survival times were measured. When Hartley animals were exposed to 100% O₂ at 2.5 atmospheres absolute (ATA) for 2 hr/day from 5–19 days postinoculation, the mean survival time (± SE) was 19.1 ± 1.6 days relative to 15.7 ± 0.7 days in the control (p<0.050). When Strain 13 guinea pigs were treated with 100% O₂ at 2 ATA for 4 hr/day on 5–16 days, the mean survival time was 21.6 ± 0.6 days compared to 16.0 ± 0.4 days for the control (p<0.001). Clinical sign measurements demonstrated that the onset of EAE in the treated animals of both strains occurred between 4–6 days after these signs became detectable in control animals. These results suggest that OHP therapy can ameliorate EAE in afflicted guinea pigs.     

Relevance of experimental allergic encephalomyelitis to multiple sclerosis

What the study of EAE has taught us that has relevance to human demyelinating diseases is discussed.     

Immunoglobulin-deficient rats fail to develop experimental allergic encephalomyelitis

Lewis rats were treated from day of birth with a rabbit anti-rat IgM antiserum. As adults these animals were found to have no detectable serum IgM and greatly reduced levels of IgG. They failed to respond to the B-cell mitogen LPS, or to make antibodies to sheep red blood cells (SRBC) or myelin basic protein (BP). These B-lymphocyte and immunoglobulin-deficient rats failed to develop clinical or histological evidence of EAE when sensitized with either whole spinal cord or purified BP. That some T-cell functions of these suppressed animals were not altered was seen by their ability to respond normally to PHA and to reject tissue allografts. The results would suggest that B-cell function (immunoglobulin-antibody production) is essential for the induction of EAE.     

Contrasting effects of anti-adhesion molecule therapy in experimental allergic encephalomyelitis and Theiler's murine encephalomyelitis.

An augmentation of experimental allergic encephalomyelitis (EAE) was observed when monoclonal antibody (mAb) to intercellular adhesion molecule 1 (ICAM-1) was administered after adoptive transfer. Clinical disease was more severe in the ICAM-1 specific mAb-treated EAE mice and included prominent ataxia compared to the PBS-treated controls or Theiler's murine encephalomyelitis virus (TMEV) infected mice treated with ICAM-1 specific mAb. Neuropathologic evaluation demonstrated a distinctly different distribution of lesions in the anti-ICAM-1-treated EAE mice which featured prominent demyelination and inflammation in the cerebellum, brainstem and cerebrum. These structures were minimally involved in the control mice and mAb treatment did not alter the neuropathology in TMEV-infected mice. These results indicate that anti-ICAM-1 can alter trafficking of lymphocytes and mononuclear cells in EAE but not TMEV-induced demyelinating disease.     

Adoptive transfer of experimental allergic encephalomyelitis with lectin-activated spleen cells

Adoptive transfer of experimental allergic encephalomyelitis (EAE) was achieved in Lewis rats using spleen cells incubated in vitro with various lectins. When stimulated with concanavalin A (Con A), its derivative succinyl-Con A, Lens culinaris or Pisum sativum agglutinin, spleen cells obtained from rats immunized with encephalitogenic emulsion could transfer EAE to normal syngeneic recipients. In contrast, spleen cells stimulated with Phaseolus vulgaris, Robinia pseudoacacia or Wisteria floribunda agglutinin did not transfer EAE. Transfer of EAE with Con A-activated spleen cells was abolished by the specific hapten inhibitor, alpha-methyl-D-mannoside, but not by D-glucose. Our data indicate that the in vitro responses to lectins may differ among T cell subpopulations. Lectins may prove useful for investigating the nature of EAE-effector cells and the mechanisms of immune regulation in this autoimmune central nervous system disease.     

Visual evoked potentials in experimental allergic encephalomyelitis

We have compared the clinical signs, brain pathology and visually evoked responses (VEP) of guinea pigs with experimental allergic encephalomyelitis (EAE). Animals immunized with myelin basic protein had a milder disease, both from the clinical and histological points of views, compared to those immunized with crude white matter extract. However, VEP findings were quite similar in both groups. The VEP of the majority of animals from both groups showed changes before or at the same time that neurological signs appeared. Electrophysiological responses were usually characterized by abnormal wave shapes and prolonged latencies. Recovery of the VEP usually preceded the recovery from clinical signs. In contrast, the severity and incidence of brain tissue pathology was not correlated to either clinical signs or VEP changes. Possible explanations of the electrophysiological, clinical and histopathological changes and their time-course are discussed.     

Mast cells in brains during experimental allergic encephalomyelitis in Lewis rats.

We studied the number of mast cells and their extent of degranulation in brains of Lewis rats with acute experimental allergic encephalomyelitis (EAE), activity induced with guinea pig spinal cord and Freund's complete adjuvant. Non-immunized controls and EAE rats were killed on days 10, 11, 12, and 16 post-immunization (p.i.). The percentage of degranulated mast cells was significantly increased in EAE brains. Signs of degranulation were observed as early as day 10 p.i. Clinical EAE signs appeared from day 10 p.i. A significant change in mast cell number was not observed. The percentage of degranulated cells was largest at day 16 p.i., at a time when the inflammation had reached the thalamus. This indicates that mast cell degranulation may occur as a result of the inflammation. Collectively, the data suggest that mast cells may play a role in the pathogenesis of EAE.     

Mast cell activity in experimental allergic encephalomyelitis

The number and functional reactivity of peritoneal mast cells (MCs) were evaluated in rats with experimental allergic encephalomyelitis (EAE). Cells were counted following staining with toluidine blue and activation was measured by B-hexosaminidase (B-hex) release. The number of detectable MCs and their capacity to release B-hex decreased significantly by 40 and 65%, respectively, as compared with normal controls just prior to the onset of clinical signs. These values returned to normal on clinical recovery. Preliminary data on MC counts performed on histological sections of rat brains with EAE suggested a similar pattern of response, i.e., an early decrease prior to disease onset with subsequent normalization on recovery. In an attempt to modify the course of EAE, rats were treated with the MC stabilizing agent nedocromil or with the MC activating agent, compound 48/80. Nedocromil induced a slight delay in the onset of EAE, but only when administered at the time of EAE induction. Compound 48/80 did not seem to affect the clinical course of the disease. Our results suggest that MCs are involved in the pathogenesis of EAE and may contribute to the induction of the disease rather than to the effector phase and its clinical expression.