Anti-endothelial cell antibody and immune complexes in the sera of animals with acute experimental allergic encephalomyelitis and chronic relapsing experimental allergic encephalomyelitis

Disturbed morphogenesis of cardiac outflow tract and increased rate of aortic arch anomalies in the offspring of diabetic rats

BACKGROUND

Maternal diabetes (MD) is a risk factor for offspring to develop cardiovascular anomalies; this is of growing clinical concern since the number of women in childbearing age with compromised glucose homeostasis is increasing. Hyperglycemia abrogates cardiovascular development in vitro; however, a link to cardiovascular defects in diabetic offspring remains to be investigated.

METHODS

We have studied cardiovascular development in offspring of MD rats by examining serial histological sections of GD 12.0-18.0 offspring. Development of pharyngeal arch artery malformations was analyzed and related to intracardiac anomalies.

RESULTS

Pharyngeal arch artery and intracardiac defects were present in 27 of 37 MD GD 13.0-18.0 offspring. Early sixth arch arteries showed abrogated arteriogenesis, whereas fourth arch artery defects developed as a result of abnormal remodeling. Morphometrical analysis showed increased apoptosis in regressing artery segments and reduced apoptosis in persisting artery segments. Double outlet right ventricle with infundibular stenosis (tetralogy of Fallot) was predominantly found in combination with sixth artery defects and pulmonary atresia. As confirmed by morphometric analysis and three-dimensional (3D)-reconstructions, outflow tract defects coincided with endocardial cushion hypoplasia. Cases with teratology of Fallot additionally showed a shorter outflow tract. No relation with apoptosis or disturbed neural crest cell migration was found.

CONCLUSIONS

Our data uniquely demonstrate mechanistic differences involved in the development of sixth and fourth artery anomalies. Whereas increased apoptosis induces fourth artery anomalies, pulmonary outflow obstruction abrogates sixth artery differentiation independent of apoptosis. The model presented allows analysis of diabetic conditions on cardiovascular development in vivo, essential for elucidating this teratology.

Serum IgG to brain microvascular endothelial cells in multiple sclerosis

Serum IgG to brain microvascular endothelial cells (BMECs) were assessed in the sera from 50 patients with definite multiple sclerosis, 24 patients with other inflammatory and non-inflammatory neurological diseases and 30 healthy individuals. Standard indirect immunofluorescence on BMEC culture was used as the bioassay system. Positive immunostaining was found in the sera (1:5 to 1:50 dilution) from 0/15 inactive relapsing remitting (RR), 12/16 active RR (p = 0.0001), 1/8 relapsing progressive (RP) and 0/11 primary progressive (PP) patients. No specific binding was detected when sera from neurologic and healthy controls were used. The specificity of the immune reaction for brain endothelium was established by the absence of staining on human umbilical vein endothelial cell and brain pericyte cultures. Gadolinium (Gd)-enhanced magnetic resonance imaging of the brain and spinal cord was performed in 36 MS patients within a 10-day interval from serum collection. Anti-brain endothelium antibodies were found in 9/12 patients with, and in 1/24 patients without Gd-enhanced lesions (p = 0.00002). Regardless of a pathogenetic role in the blood-brain barrier breakdown, serum IgG to BMECs may be a marker of disease activity in RR and RP MS and a factor differentiating RR/RP and PP MS.

Vascularization and microvascular permeability in solid versus cell-suspension embryonic neural grafts

Vascularization and microvascular permeability were assessed in a comparative study of solid (organized) and cell-suspension (dissociated) fetal nigral grafts implanted in the dopamine-deprived striatum of adult rats. Both graft types were analyzed by chromogen detection of intravenously injected horseradish peroxidase (HRP), which outlined vessel walls, and, in cases in which the blood-brain barrier was compromised, permeated the graft and host parenchyma. Survival of graft-derived dopaminergic cells was assessed using tyrosine hydroxylase (TH) immunocytochemistry. Glial reactivity to cell-suspension grafts was similarly assessed with an antibody directed against glial fibrillary acidic protein. Morphometry revealed significantly higher microvessel density in the cell-suspension grafts (p < 0.001), which effectively equaled that found in the contralateral striatum despite rather prominent surrounding glial reactivity. Capillaries in the cell-suspension grafts were not permeable to blood-borne HRP at postimplantation study times of 7, 14, and 30 days whereas, in the solid grafts, permeability in some cases could be detected for up to 30 days. Large numbers of cells immunoreactive for TH were seen in cell-suspension grafts; in contrast, few if any were found in the majority of solid transplants. The multiple-fragment solid graft implant model used clinically compares poorly with the cell-suspension model because it lacks consistency in early revascularization and shows a greater (albeit temporary) tendency for blood-brain barrier dysfunction. Delayed and inadequate vascularization of the solid graft is likely to account for graft failure more often than in the cell-suspension graft. Similarly, a certain critical number of specific grafted cells are required to achieve sufficient expression to bring about a favorable response in the disabled host, and this expression appears to be achieved less consistently with the solid implant technique.

Prevalence of anti-endothelial cell antibodies in patients with autoimmune diseases

The prevalence of anti-endothelial cell antibodies (AECA) of IgA, IgG and IgM classes was studied by means of enzyme-linked immunosorbent assays (ELISA) in 466 patients with autoimmune/inflammatory disorders. The reference limits in the ELISAs for the AECA were determined from a random population sample of 249 subjects. The frequency of AECA was highest in patients with SLE (n = 42), 14.6% mainly of IgG class, and the presence of AECA correlated with disease activity in these patients. In the RA patient group (n = 200), 9.5% had AECA, mostly of IgA type. We found no association between the presence of AECA and extra-articular manifestations of RA or survival rate. In patients with undefined connective tissue disease (n = 57), ankylosing spondylitis (n = 109), and psoriatic arthritis (n = 58), the frequency of AECA corresponded to that of the random population sample. In a cohort of samples sent to the laboratory for determination of anti-nuclear antibodies (ANA) there was a correlation between the presence of ANA and AECA. Our findings indicate that RA patients are characterized by IgA class AECA, whereas SLE patients have IgG class AECA also correlating to disease activity.

Changes of experimental allergic encephalomyelitis by methionine-enkephalin injected into lateral ventricles of the rat brain

Our previous investigations have shown that the opioid peptide methionine-enkephalin (Met-Enk) modulates in vivo a variety of humoral and cell-mediated immune performances. In this study, rats bearing polyethylene cannulae permanently inserted into the lateral ventricles of the brain were used. Experimental allergic encephalomyelitis (EAE) was induced with guinea pig spinal cord in complete Freund's adjuvant injected into the left hind foot pad. The following groups of cannulated rats were tested: nontreated with Met-Enk or saline, intracerebroventricularly (i.c.v.) injected with saline, and i.c.v. treated with low (1 microgram/kg) dose of Met-Enk and high (1 mg/kg) dose of Met-Enk. Intact noncannulated rats sensitized for EAE served as an additional control. The results showed that i.c.v. treatment with 1 microgram/kg of Met-Enk significantly increased the incidence and severity of EAE. In contrast, injections of 1 mg/kg of Met-Enk produced a moderate decline of clinical EAE, but marked diminution of inflammatory lesions in the brain. Interestingly, histopathology of EAE was more pronounced in control rats treated i.c.v. with saline. On the other hand, control cannulated rats noninjected with saline exhibited a striking decrease of neurological and histopathological signs of the disease, thus indicating a suppressive effect of stress (surgical procedure) on EAE. In conclusion, the present study showing the central effect of Met-Enk on EAE when peptide was applied in the cerebral cavity, and earlier studies which revealed the peripheral effect on EAE when Met-Enk was administered intraperitoneally, suggests that Met-Enk exerts its immunomodulatory action both centrally and peripherally.

Preliminary studies on sensitization of Lewis rats with sulfated glucuronyl paragloboside

A large number of patients with peripheral neuropathy and IgM paraproteinemia have IgM monoclonal antibodies which recognize a carbohydrate determinant shared by myelin-associated glycoprotein (MAG) and sulfated glucuronyl glycolipids (SGGLs). There is considerable evidence that these IgM monoclonal antibodies are responsible for demyelination in this disorder. To study the pathogenic role of SGGLs in this type of neuropathy, we sensitized Lewis rats with sulfated glucuronyl paragloboside (SGPG), a major SGGL. Fifty percent of the animals (8/16) developed neurological symptoms such as mild to moderate distal tail tone loss, with or without abnormal posture, along with development of anti-SGPG antibodies. These antibodies reacted with SGGLs, but not with rat MAG. Morphological studies showed: (1) axonal change in the lateral aspects of the dorsal columns in the spinal cord; and (2) damage to the endothelial cells in the spinal cord which suggested a breakdown of the blood-brain barrier. There was no obvious change in the peripheral nerve. Since no marked cellular infiltration was detected in these lesions, the clinicopathological findings observed could be induced by humoral mechanism, most likely anti-SGPG antibodies.

Immunocytochemical localization of the terminal complement complex in multiple sclerosis

Granular deposits of C9 and the terminal complement complex, measuring 0.3-1.2 microns, have been demonstrated immunocytochemically in association with capillary endothelial cells, predominantly within plaques and adjacent white matter, in tissue obtained at autopsy from 5/7 patients with multiple sclerosis (MS) and one individual with subacute sclerosing panencephalitis but not from 7/7 controls. This finding suggests that the evolution of focal tissue damage in MS may involve complement activation associated with passage of humoral and cellular mediators of the immune system through the blood-brain barrier.

Integrity of the blood-brain barrier in retinal xenografts is correlated with the immunological status of the host

The purpose of this study was to determine the immunological correlates of blood-brain barrier breakdown in retinal xenografts in rats by utilizing skin grafting to initiate a timed immune response to the transplanted neural tissue. Embryonic day 13-14 CD-1 mouse retinae were grafted into the brainstem parenchyma of neonatal Sprague-Dawley rats. In one group of animals a 100 mm2 CD-1 skin graft was placed on the flank 21 days after the initial neural transplant in order to provoke an immune response to the neural graft. Control animals received no skin graft. Animals were injected with horseradish peroxidase (HRP) in the femoral vein 2-8 days after skin grafting. Brains were processed for Nissl, HRP-tetramethylbenzidine, and anti-M-6, -lymphocyte, -macrophage, and -astrocyte antibodies. Experimental and control animals injected 2-4 days after skin grafting showed no leakage of reaction product in the grafted tissue. A small percentage (one of eight) of 5-day animals showed isolated, patchy leakage, but no evidence of rejection of the neural graft. At 6 days all of the grafts showed evidence of leakage, and 71% of these grafts showed infiltration of lymphocytes. By 7-8 days extensive leakage of HRP and widespread infiltration of lymphocytes and macrophages were clearly evident. The present study demonstrates that blood-brain barrier breakdown is correlated closely with the sequence of immunological rejection of the graft. While these results confirm that a barrier exists in healthy neural transplants, they suggest that immunological factors should be considered in cases in which grafts are not protected by an intact barrier.

Immune mechanisms in the pathogenesis of demyelinating diseases

The loss of myelin which characterises many human and experimental demyelinating diseases, among them multiple sclerosis, is thought to be immune mediated, but the precise mechanisms responsible remain unknown despite intense research. Normally, myelin in the central nervous system (CNS) is protected from systemic immune responses by the blood brain barrier, which separates nervous tissue from the peripheral circulation. Here we review evidence suggesting that an understanding of the demyelinating disorders may be helped by considering their immune pathogenesis in two stages. The first is damage to the blood brain barrier; this appears to be cell mediated, and allows infiltration into the CNS of other immune effectors. These include complement and also macrophages, which together may mediate the second stage, injury to the myelin/oligodendrocyte complex.

Plasma immunoglobulin responses and disease severity in chronic relapsing experimental allergic encephalomyelitis

Plasma IgG, IgA and IgM responses in various stages of chronic relapsing experimental allergic encephalomyelitis (CR-EAE) were investigated by ELISA and rocket immunoelectrophoresis. Autoantibody levels were elevated in acute EAE but immunoglobulin responses were maximal in chronic disease. Plasma IgG and IgA specific for the whole cord, myelin and MBP correlated closely with the clinical signs of post-acute disease; in age-matched groups, levels were lower in animals in remission or with no further disease than in those in relapse or with a stable chronic disease course. Sequential sampling revealed a significant increase in neuroantigen-specific IgG (with MBP as the dominant autoantigen) during the onset of a relapse. Lipid-specific antibody levels were raised throughout CR-EAE but constituted only a small proportion of the total response against neural antigens. Determination of total immunoglobulin concentrations suggested a general suppression of IgG responses in guinea pigs in remission. The strong correlations found between antibody levels and the severity of chronic disease provide further evidence that antibody-mediated mechanisms can play a major role in the pathogenesis of CR-EAE.

Patterns of angiogenesis in neural transplant models: II. Fetal neocortical transplants

Vascular integration between transplanted fetal CNS tissues and host brain is essential for long-term transplant survival. This study compares the time course and mechanism of vascularization in allografts of fetal cerebral cortex inserted either into the fourth ventricle or directly into the parietal cortex or hippocampus of perinatal rats. Recipient animals were administered 3H-thymidine after various postoperative time periods. The tissues were processed for light microscopic autoradiography to determine the temporal pattern of endothelial proliferation at the graft sites. Correlative electron microscopy depicted the morphological changes in transplant vasculature. Some recipients were prelabelled with 3H-thymidine prior to transplantation to determine if host vessels invaded the grafts; conversely, some donor tissues were prelabelled in utero to ascertain if the intrinsic vascular anlagen survived. Intraventricular transplants contained patent vessels, probably originating from the host pia mater, as early as 24 hours postoperative. Intraparenchymal transplants had patent vessels by 72 hours and a more complete network by 5 days. Prelabelling experiments and ultrastructural observations demonstrated that adjacent host pial vessels became incorporated into the perimeter of the intraventricular transplants and later grew centrally into the grafts. Intraparenchymal transplants also contained host vessels that exhibited a similar growth pattern. Intrinsic graft vessels remained viable and continued their development, and presumably anastomosed with the ingrowing host vasculature. Temporal labelling studies revealed that both vessel populations attained their highest proliferative rates within 72 hours after transplantation. This study demonstrates that the vasculature which develops within both intraventricular and intraparenchymal fetal CNS transplants is chimeric, consisting of intrinsic fetal vasculature and proliferating host vessels. The mechanism of transplant vascularization may be significant with regard to astrocytic, immunological, or blood-brain-barrier characteristics at these transplantation sites.

Anti-endothelial cell antibodies and circulating immune complexes in the sera of patients with multiple sclerosis

Sera from patients with multiple sclerosis (MS) were examined for anti-endothelial cell antibodies and immune complexes by enzyme-linked immunosorbent assays (ELISAs) using cultured brain endothelial cells and Raji cells respectively. The concentrations of immunoglobulin (Ig) G which bound to cerebral endothelial cells and of immune complexes were significantly increased in the sera of patients with MS, especially those with an exacerbation. The levels of IgG binding to endothelial cells were still increased in the sera of exacerbated MS patients after blocking Fc receptors compared to those of controls. These findings indicate that IgG binding to endothelial cells may be mediated via an immunologically specific antigen-antibody interaction. The results show that anti-endothelial cell antibodies and immune complexes are present in cases of MS and they may play a pathogenetic role in the blood-brain barrier (BBB) damage.

A new model for multiple sclerosis: chronic experimental allergic encephalomyelitis induced by immunization with cerebral endothelial cell membrane

Multiple sclerosis is considered to be an autoimmune demyelinating disease of the central nervous system. Damage to the blood-brain barrier, of which endothelial cells are the main constituent, occurs in multiple sclerosis, probably due to immunological mechanisms. We report here the results of immune-mediated damage to these cells, produced by immunizing guinea pigs with an endothelial cell membrane fraction. The fraction was obtained from cerebral endothelial cells grown in vitro and was free from myelin basic protein. The immunized animals developed a chronic neurological illness with evidence of delayed hypersensitivity to the cell membrane fraction but not to myelin antigens. Histological examination of the brain in the acute stage showed mononuclear cell infiltrates around blood vessels, while in the chronic phase large areas of demyelination, especially in the periventricular region, were present. This bore a striking similarity to the brain in multiple sclerosis. This may prove to be a useful new animal model for the investigation of the human demyelinating disease.