Experimental allergic encephalomyelitis: passive transfer of resistance during lactation

Effects of biological sex and pregnancy in experimental autoimmune encephalomyelitis: It's complicated

Experimental autoimmune encephalomyelitis (EAE) can be induced in many animal strains by inoculation with central nervous system antigens and adjuvant or by the passive transfer of lymphocytes reactive with these antigens and is widely used as an animal model for multiple sclerosis (MS). There are reports that female sex and pregnancy affect EAE. Here we review the effects of biological sex and the effects of pregnancy on the clinical features (including disease susceptibility) and pathophysiology of EAE. We also review reports of the possible mechanisms underlying these differences. These include sex-related differences in the immune system and in the central nervous system, the effects of hormones and the sex chromosomes and molecules unique to pregnancy. We also review sex differences in the response to factors that can modify the course of EAE. Our conclusion is that the effects of biological sex in EAE vary amongst animal models and should not be widely extrapolated. In EAE, it is therefore essential that studies looking at the effects of biological sex or pregnancy give full information about the model that is used (i.e. animal strain, sex, the inducing antigen, timing of EAE induction in relation to pregnancy, etc.). In addition, it would be preferable if more than one EAE model were used, to show if any observed effects are generalizable. This is clearly a field that requires further work. However, understanding of the mechanisms of sex differences could lead to greater understanding of EAE, and suggest possible therapies for MS.

The Short and Long-Term Effects of Pregnancy on Multiple Sclerosis and Experimental Autoimmune Encephalomyelitis

The role of pregnancy in multiple sclerosis (MS) is of importance because many patients with MS are young women in the childbearing age who require information to inform their reproductive decisions. Pregnancy is now well-known to be associated with fewer relapses of MS and reduced activity of autoimmune encephalomyelitis (EAE). However, in women with multiple sclerosis, this benefit is not always sufficient to protect against a rebound of disease activity if disease-modulating therapy is ceased for pregnancy. There is concern that use of assisted reproductive therapies can be associated with relapses of MS, but more data are required. It is thought that the beneficial effects of pregnancy are due to the pregnancy-associated changes in the maternal immune system. There is some evidence of this in human studies and studies of EAE. There is also evidence that having been pregnant leads to better long-term outcome of MS. The mechanism for this is not fully understood but it could result from epigenetic changes resulting from pregnancy or parenthood. Further studies of the mechanisms of the beneficial effects of pregnancy could provide information that might be used to produce new therapies.

Late pregnancy suppresses relapses in experimental autoimmune encephalomyelitis: evidence for a suppressive pregnancy-related serum factor

Women with multiple sclerosis have significantly diminished disease activity during pregnancy. The purpose of our study was to identify the underlying mechanism for the diminished disease activity. We found that during the period of late pregnancy there is protection against paralysis, during both the induction and effector phases of relapsing experimental autoimmune encephalomyelitis, a mouse model of multiple sclerosis. We did not find any changes in the cytokine secretion profiles or the proliferative activity of autoreactive T cells from mice induced during late pregnancy compared with virgin controls. In mice mated after disease onset, the inflammatory histologic lesions did not clear, despite marked clinical improvement during pregnancy. We found evidence for a serum factor present in late pregnancy that suppresses T cell activation. In the presence of sera taken from mice late in pregnancy, the proliferative response and IL-2 production of proteolipid protein p139-151-specific T cells were significantly diminished as compared with stimulation in the presence of normal mouse sera. In conclusion, serum from late pregnancy has the capacity to down-regulate T cell responses and might be associated with the amelioration of disease activity in experimental autoimmune encephalomyelitis.

Suppression of experimental autoimmune encephalomyelitis by cannabinoids

The effect of delta 8-THC on experimental autoimmune encephalomyelitis (EAE) was examined. delta 8-THC is an analogue of delta 9-THC, the psychoactive component of marijuana. It is more stable and less psychotropic than delta 9-THC and like the latter it binds to the brain cannabinoid receptor. Two strains of rats were inoculated for EAE, and delta 8-THC (40 mg/kg) was administered for up to 21 days. delta 8-THC significantly reduced the incidence and severity of neurological deficit in both rat strains. The beneficial influence of delta 8-THC only occurred on oral administration and not with parenteral injection. Serum corticosterone levels were twofold elevated in rats with EAE chronically treated with delta 8-THC. These results suggest that suppression of EAE by cannabinoids may be related to their effect on corticosterone secretion.

Interleukin-10 prevents experimental allergic encephalomyelitis in rats

Experimental allergic encephalomyelitis (EAE) is an autoimmune disease mediated by myelin protein-specific CD4+ T lymphocytes of the T(h)1-like phenotype. In rats, the disease is characterized by a monophasic clinical manifestation, followed by a subsequent spontaneous remission and the establishment of life-long resistance to reinduction of disease. Recent data indicate that intracerebral cytokine production, in particular synthesis of interleukin(IL)-10, is selectively up-regulated during the recovery phase of disease. This led us to assess the effects of IL-10 on different rat lymphoid cell functions in vitro and to consider the possibility of an IL-10-mediated treatment to prevent the induction of central nervous system (CNS) autoimmune disease in vivo. Human recombinant IL-10 suppressed interferon-gamma induced major histocompatibility complex class II up-regulation in rat peritoneal macrophages, exhibited pleiotropic effects on thymocytes and totally abrogated tumor necrosis factor production of encephalitogenic T lymphocytes in vitro, without simultaneously affecting proliferative responses of the cells. Upon systemic administration during the initiation phase of disease, IL-10 was effective in markedly suppressing the subsequent induction of EAE in Lewis rats. This suppression of clinical disease coincided with a significant and specific elevation of myelin basic protein-specific autoantibody production, a sustained T cell proliferative response to myelin basic protein and a diminution of CNS infiltrations and thymic involutions in diseased animals. These data implicate IL-10 as a possible candidate for treatment of T(h)1-mediated CNS (auto-) immune diseases.

Mast cells in experimental allergic encephalomyelitis: characterization, distribution in the CNS and in vitro activation by myelin basic protein and neuropeptides

Mast cells (MC) have been implicated in the pathogenesis of experimental allergic encephalomyelitis (EAE). In order to further evaluate their role, several morphological and functional studies were performed. Semiquantitative counts of histological sections showed a significant reduction in MC numbers in EAE brains. In addition, a higher proportion of EAE MC (about 50-70%) appeared degranulated compared with about 20% degranulation in controls. Central nervous system (CNS) MC exhibited staining properties of connective tissue MC and about 98% of them, both in diseased and control rats, were located in the thalamus. They were not present in the spinal cord and did not relate to EAE lesions. In vitro incubation of peritoneal MC (of connective tissue phenotype) with either MBP, or with neuropeptides such as substance P or bradykinin resulted in release of beta-hexosaminidase and histamine. The latter responses were similar in both EAE and control rats. It is suggested that the decrease in number and in granular content of CNS MC in EAE may reflect prior in vivo activation. The fact that MC were activated by MBP and by neuropeptides in vitro suggests a possible mechanism of MC activation in EAE.

Inhibition of acute, experimental autoimmune encephalomyelitis by the synthetic immunomodulator linomide

Linomide (LS-2616, quinoline-3-carboxamide) is a synthetic immunomodulator that stimulates natural killer cell activity and activates several lymphocytic subpopulations in experimental animals and humans. In this study we determined the effect of oral treatment with linomide on the development of experimental autoimmune encephalomyelitis, an animal model for immune-mediated human demyelinating disorders. Experimental autoimmune encephalomyelitis was induced in SJL/J mice and in an outbred strain of rats (Sabra) by subcutaneous injection of spinal cord homogenate in adjuvant followed by inoculation with Bordetella pertussis. Linomide was administered in drinking water, at an estimated dose of 50 to 100 mg/kg/day. None of the linomide-treated mice (0/41) and Sabra rats (0/15) developed any clinical or pathological signs of experimental autoimmune encephalomyelitis, whereas almost all control animals (48/53 and 18/19, respectively) were severely paralyzed and 64.5% died from the disease. Lymphocytes obtained from linomide-treated animals had reduced in vitro proliferative responses to guinea pig myelin basic protein, proteolipid protein of the myelin, and tuberculin-purified protein derivative, unlike antigen-independent proliferation which was rather unaffected. Natural killer cell activity (tested by a cytotoxic assay on radiolabeled YAC-1 target cells) was significantly enhanced in mice treated with linomide. Our results indicate that modulation of the immune system with linomide leads to complete inhibition of experimental autoimmune encephalomyelitis in the absence of systemic immunosuppression. Linomide could therefore be of use in future clinical trials for the treatment of human autoimmune demyelinating disorders.

Natural and experimental transfer of anti-Pertussis antibodies confers resistance to experimental autoimmune encephalomyelitis

Pregnant rats challenged with Bordetela Pertussis vaccine, with or without encephalitogenic antigen during pregnancy, transferred a resistance to induction of experimental autoimmune encephalomyelitis (EAE) to their offspring. Cross-fostering experiments showed that the protection against EAE is conferred during the lactation period through the transfer of anti pertussis antibodies in the milk. The degree of protection correlated with antibody levels. Passive transfer of these antibodies through intraperitoneal injection to naive adult rats also conferred the same degree of protection against EAE induction. It is suggested that such transfer of resistance and antibodies may serve as a model for the study of milk transmitted immunocompetent factors, as well as a model for the mechanisms involved in the resistance to EAE.

Multifocal motor nerve conduction abnormalities in amyotrophic lateral sclerosis

Motor nerve conduction in motor neuron disease is considered normal until the terminal stages of the disease, a notable exception being lower motor neuron syndrome associated with anti-glycolipid antibodies. We reviewed the electrophysiological findings in all our patients who were diagnosed as having amyotrophic lateral sclerosis (ALS) during the last 6 years. Six patients, clinically indistinguishable from "classical" ALS patients, out of 31 (19%) displayed motor nerve conduction abnormalities. The most consistent finding, occurring in all 6, was prolonged distal latency or reduced conduction velocity in the distal segment of the median nerve, with normal sensory conduction, suggesting possible pressure proneness of motor nerve fibers in ALS. Additional abnormalities included multifocal motor conduction slowing (3 patients), and conduction blocks (4 patients). None of the patients had paraproteinemia and anti-GM1 and anti-GD1a antibodies were not detected. Thus, a subgroup of clinically indistinguishable ALS patients may have multifocal motor nerve conduction abnormalities, indicating motor nerve fiber involvement. The etiology and pathogenesis of the peripheral nerve involvement are presently unknown.

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.

In vitro synthesis of antibodies to myelin antigens by Epstein-Barr virus-transformed B lymphocytes from patients with neurologic disorders

Anti-myelin antibodies can be found in sera from patients with neurologic disorders of suspected immune-mediated pathogenesis such as multiple sclerosis and inflammatory polyneuropathies. However, the specificity of these findings is controversial. In the present study, in vitro synthesis of antibodies to myelin components was compared to their presence in sera in diverse neurological disorders. Epstein-Barr virus was used to activate B lymphocytes for in vitro antibody production. Anti-myelin basic protein and anti-galactocerebroside antibodies were secreted in vitro by B lymphocytes derived from patients with neurological disorders of various etiologies and pathogenetic mechanisms. Anti-myelin basic protein antibodies were detected in many more cell culture supernatants than in sera from the same patients. In vitro secretion of antibodies to myelin antigens, as well as the presence of these antibodies in body fluids, are apparently non-specific for disease type and may be secondary to neural tissue damage.