Immunoglobulin binding to brain in autoimmune mice

Brain-reactive autoantibodies (BRAA) are thought to play an important role in central nervous system (CNS) manifestations of systemic lupus erythematosus (SLE). Previous studies have shown the existence of BRAA in human and murine SLE. This study was undertaken to establish and characterize the presence of autoantibody binding to brain of autoimmune mice. Laser confocal microscopy was performed on frozen brain sections to detect the presence of immunoglobulin (Ig) in the brain of MRL/lpr and BXSB mice and compare that to control strains of MRL/mp and C57BL/6 mice. There was a dramatic increase in fluorescence in the brains of MRL/lpr and BXSB at 4 months of age. There was little or no Ig detected in the brains of control mice. This increase in presence of Ig in the autoimmune mouse brain was paralleled by an increase in the serum titers of BRAA and anti-DNA autoantibodies as determined by ELISA. These studies provide another link between the existence of brain-reactive autoantibodies and altered CNS functioning.

Detection of an autoantibody from Pug dogs with necrotizing encephalitis (Pug dog encephalitis)

An autoantibody against canine brain tissue was detected in the cerebrospinal fluid (CSF) and serum of two Pug dogs (Nos. 1 and 2) by indirect immunofluorescence assay (IFA). Dog No. 1, a 2-year-old male, exhibited severe depression, ataxia, and generalized seizures and died 2 months after the onset of symptoms. Dog No. 2, a 9-month-old male, exhibited severe generalized seizures and died 17 months after the onset of symptoms. Histopathologic examination revealed a moderate to severe multifocal accumulation of lymphocytes, plasma cells, and a few neutrophils in both the gray and white matter of the cerebrum in dog No. 1. In dog No. 2, the cellular infiltrates were mild, but there was a severe, diffuse, and multifocal necrosis in the cerebral cortex with prominent astrocytosis. With the aid of IFA using fluorescein isothiocyanate-labeled antidog IgG goat serum and a confocal imaging system, specific reactions for glial cells were detected in the CSF of these Pug dogs but not in six canine control CSF samples. Double-labeling IFA using CSF from these Pug dogs and a rabbit antiserum against glial fibrillary acidic protein (GFAP) revealed that the autoantibody recognized GFAP-positive astrocytes and their cytoplasmic projections. By immunoblot analysis, the autoantibody from CSF of these Pug dogs recognized two common positive bands at 58 and 54 kd, which corresponded to the molecular mass of human GFAP. The role of this autoantibody for astrocytes is not yet clear. However, if the presence of the autoantibody is a specific feature of Pug dog encephalitis, it will be a useful clinical diagnostic marker and a key to the pathogenesis of this unique canine neurologic disease.

Learning in year-old female autoimmune BXSB mice

BXSB/ MpJ-Yaa and NZB/BINJ mice have been used as animal models for both developmental learning disability and systemic autoimmune disease. Approximately 40-60% of these animals show ectopic clusters of neurons in Layer I of cortex similar to those found in postmortem analyses of human dyslexics, and all exhibit an autoimmune condition similar to systemic lupus erythematosus (SLE) in humans. The expression of immune disease in the BXSB strain, unlike in humans, is more severe in males than females. Most previous studies have examined the behavioral sequelae of neocortical ectopias at a relatively young age, when the BXSB females (unlike the male BXSB and female and male NZBs) are not yet showing high titers of autoantibodies associated with their lupus-like form of autoimmune disease. This study examined the behavior of BXSB females at an age subsequent to autoimmune disease onset. When contrasted with younger animals, year-old BXSB females showed good learning behavior, with no differences in Lashley maze learning and remarkably good performance in a visual discrimination learning task. These results are consistent with other data which indicate that many types of learning behavior are apparently unperturbed by systemic autoimmune disease. Results also showed significant interactions between a measure of lateral paw preference and the presence or absence of ectopias in Lashley maze learning. Animals without ectopias that exhibited a right lateral paw preference showed the greatest number of errors on a number of test measures. These findings support previous results indicating that behavioral effects associated with ectopias may vary based upon the behavioral laterality of affected animals.

Animal models for nervous system disease in systemic lupus erythematosus

Animal models have much to teach us about nervous system dysfunction in SLE. It should be stressed that the murine strains described in this review have variable expression in the onset and severity of clinical and serological features, perhaps making them more like a heterogeneous human population with SLE. With this in mind, studies involving animal models like those involving human subjects should use a sample size that ensures adequate power. It is not surprising that studies that use sample sizes as low as four to five animals per group would find discrepant results, especially in outcomes that are measured prior to the terminal phases of the disease. Similar to human SLE patients, murine models have systemic autoimmune as well as neurological manifestations. Studies with murine models must continue to consider some type of SLE disease activity measures in order to control for the effects of systemic disease on nervous system dysfunction. Because of the short time window between the earliest evidence of neurologic dysfunction and severe autoimmune disease manifestations, especially in MRL/lpr mice, the disease acceleration model may allow a more careful dissection of how immunological events are related to nervous system dysfunction. Alternatively, the study of MRL/lpr mice ultraearly (e.g., 3 weeks of age) could also provide invaluable information about the first events leading to nervous system dysfunction in SLE. Both approaches promise to identify predictors of specific nervous system manifestations that may suggest novel and more specific therapeutic interventions.

Neurobehavioral alterations in autoimmune mice

Inbred MRL, NZB and BXSB strains of mice spontaneously develop a systemic, lupus-like autoimmune disease. The progress of autoimmunity is accompanied with a cascade of behavioral changes, most consistently observed in tasks reflective of emotional reactivity and the two-way avoidance learning task. Given the possibility that behavioral alterations may reflect a detrimental consequence of autoimmune-inflammatory processes and/or an adaptive response to chronic malaise, they are tentatively labeled as autoimmunity-associated behavioral syndrome (AABS). It is hypothesized that neuroactive immune factors (pro-inflammatory cytokines, brain-reactive antibodies) together with endocrine mediators (corticotropin-releasing factor, glucocorticoids) participate in the etiology of AABS. Since AABS develops natively, and has a considerable face and predictive validity, and since the principal pathway to autoimmunity is known, AABS may be a useful model for the study of CNS involvement in human autoimmune diseases and by extension, for testing autoimmune hypotheses of several mental disorders (major depression, schizophrenia, Alzheimer's disease, autism and AIDS-related dementia).

Autoantibody reactivity in serum of patients with Alzheimer's disease and other age-related dementias

Serum antibodies against a series of antigens, including an organ-specific central nervous system (CNS) antigen and the neurotransmitter serotonin, were investigated in 22 patients with Alzheimer's Disease (n=15) and other age-related dementias (n=7) by indirect immunofluorescence assay and enzyme-linked immunosorbent assay. Patients with dementia showed an increase of antibody-positive sera against nuclear antigen, gastric parietal cells, CNS antigen, gangliosides (Gm1), laminin, and keratin. Alzheimer's Disease patients alone exhibited antibodies against CNS antigen. However, the results do not show sufficient specificity and sensitivity for use as a diagnostic indicator.

Serum anti-brain endothelium antibodies and cognitive assessment in patients with Binswanger's encephalopathy

The pathogenic mechanism underlying the vascular changes in Binswanger's encephalopathy (BE) is unknown. To test whether alterations of the humoral immunity may lead to endothelium damage, we analyzed serum levels of anti-brain endothelium antibodies (ABEA) (IgG and IgM) in 16 BE patients, 19 subjects with ischemic vascular disease without mental deterioration and 18 normal healthy subjects. ABEA IgM were found elevated in 1/16 (6%) BE patients and in 4/19 (21%) patients with cerebrovascular diseases; an increase in ABEA IgG was found in 6/16 (38%) BE patients and in 7/19 (37%) cerebrovascular patients. Association with anti-cardiolipin antibodies (IgG and/or IgM) was found in 50% of BE patients with elevated ABEA and only 10% of those with no increase, whereas high titres of anti-neurofilament antibodies (1:10,000) were detected in 40% and 71% respectively. In BE, ABEA IgG but not IgM showed a trend, although not significant, towards a correlation with the duration of the disease (rs = 0.47; p = 0.07) and significantly correlated with the cognitive function as assessed by the Mini mental state (MMS) score (rs = 0.56; p = 0.02). Higher mean values of the MMS score were found in BE patients with elevated ABEA than in those without (p = 0.04). This difference was not due to language disorders neither to an association with stroke risk factors or anti-neurofilament antibodies. However, there were no significant differences in MMS scores between cerebrovascular patients with ABEA and those without. A "neuro-protective" role is hypothesized for the ABEA in the development of dementia in BE.

Developmental dyslexia and animal studies: at the interface between cognition and neurology

Recent findings in autopsy studies, neuroimaging, and neurophysiology indicate that dyslexia is accompanied by fundamental changes in brain anatomy and physiology, involving several anatomical and physiological stages in the processing stream, which can be attributed to anomalous prenatal and immediately postnatal brain development. Epidemiological evidence in dyslexic families led to the discovery of animal models with immune disease, comparable anatomical changes and learning disorders, which have added needed detail about mechanisms of injury and plasticity to indicate that substantial changes in neural networks concerned with perception and cognition are present. It is suggested that the disorder of language, which is the cardinal finding in dyslexic subjects, results from early perceptual anomalies that interfere with the establishment of normal cognitive-linguistic structures, coupled with primarily disordered cognitive processing associated with developmental anomalies of cortical structure and brain asymmetry. This notion is supported by electrophysiological data and by findings of anatomical involvement in subcortical structures close to the input as well as cortical structures involved in language and other cognitive functions. It is not possible at present to determine where the initial insult lies, whether near the input or in high-order cortex, or at both sites simultaneously.

Anti-brain antibodies in the sera of rheumatoid arthritis patients: relation to disease activity and psychological status

Auto-antibodies reactive with brain are known to occur in various immunological disorders. Their significance with respect to disease activity, neurological manifestations, or psychological status is, however, not known. In previous studies it was found that there were antibodies reactive with brain in the sera of patients with rheumatoid arthritis (RA). The present study sought to confirm and extend our previous findings and determine the significance of these antibodies with respect to disease activity. It also investigated a possible connection between psychological function in RA and these auto-antibodies. Sera drawn from 14 RA patients, at bi-weekly intervals over 3 months, showed the presence of antibodies against transmembrane proteins from murine brain. These antibodies correlated positively with rheumatoid factor and joint swelling. There was a trend toward a correlation between depression and daily mood scores and the number of antibodies reactive with brain. In addition, a correlation between cognitive coping styles in RA patients and auto-antibodies was found. There was also evidence for a sub-population of pathogenic antibodies.

Brain reactive monoclonal auto-antibodies: production and characterization

To determine the role of auto-antibodies in the pathogenesis of neuropsychiatric manifestations of systemic lupus erythematosus (NP-SLE), it will be necessary to characterize the diversity of auto-antibodies that exist. This can be done by producing a library of monoclonal, brain-reactive auto-antibodies. From such a library the antigens to which the antibodies bind, and whether there are any interesting relations between these antigens, can be determined. Behavioral effects can also be investigated. Toward these ends, brain-reactive monoclonal auto-antibodies (BRMA) were produced. The production and characterization of two monoclonal antibodies is presented in this study.

The organization of radial glial fibers in spontaneous neocortical ectopias of newborn New Zealand black mice

Forty percent of New Zealand Black (NZB) mice, a strain that develops severe autoimmune disease, have ectopic collections of neurons in layer I of the neocortex. This strain is used as a model for similar anomalies seen in the dyslexic brain. In the present study we immunohistochemically stained radical glial fibers and their anchoring processes (which form the glial external limiting membrane) in the region of ectopias in NZB mice. The organization of glial fibers was abnormal in and around the ectopic region. Radial glial fibers underlying the ectopia were denser than in the surrounding cortex, and within the ectopia there was a disorganized matrix of glial fibers. Most glial fibers, however, did not enter the ectopia, but instead curved towards the edge of the ectopia and attached there. The glial limiting membrane was breached in the area of the ectopia, indicating that an insult to this membrane may have allowed neurons to migrate into layer I and the overlying subarachnoid space. This finding along with the results of the accompanying paper on puncture wounds of the cortex of newborn rodents supports the view that rupture of the external limiting glial membrane is responsible for the inappropriate migration of neurons into the molecular layer.

Detection of brain-reactive autoantibodies in the sera of autoimmune mice using ELISA

There are considerable problems with developing an assay to detect the often small quantities of autoantibodies which react against antigens in a heterogeneous and complex mixture from a source such as brain. An indirect enzyme-linked immunosorbent assay (ELISA) has been developed which can detect naturally occurring autoantibodies in serum that are reactive with integral brain membrane antigens. Sera were collected from autoimmune BXSB and NZB mice and non-autoimmune C57BL/6 mice at various ages and were assayed for the presence of brain-reactive autoantibodies (BRAAs). It is shown that this technique provides a highly sensitive, specific, and rapid assay for detecting BRAAs in serum. It shows that integral membrane antigens from whole brain can be isolated and used to detect and quantitate antibodies in the sera of autoimmune and non-autoimmune mice. The data also confirm studies, using different techniques, showing higher levels of autoantibodies to brain in autoimmune as compared to non-autoimmune mice. There are numerous potential applications for this ELISA, such as in rapidly screening large numbers of samples of biological fluids, tracking autoimmune disease progression over time, detecting small quantities of antibody against brain antigens, and as an assay system for investigating the role of BRAAs in the pathogenesis of immune mediated CNS disease.

Monoclonal antibodies to the heavy neurofilament subunit (NF-H) of Torpedo cholinergic neurons

Previous studies from our laboratory suggest that Alzheimer's disease sera contain a repertoire of antibodies to the heavy neurofilament subunit (NF-H) and that a subpopulation of these antibodies bind specifically to epitopes highly enriched in NF-H isolated from the purely cholinergic electromotor neurons of Torpedo. In the present study, we prepared and characterized monoclonal antibodies (MAbs) that bind to epitopes specifically enriched in Torpedo cholinergic neurons. This was performed by a differential enzyme-linked immunosorbent assay (ELISA) in which MAbs were selected that bind to epitopes much more abundant in the NF-H protein of Torpedo cholinergic neurons than in NF-H from the chemically heterogeneous Torpedo spinal cord. This yielded four MAbs, three of which (TC4, TC8, and TC21) were found to be specific to NF-H and one (TC15) that reacts with both NF-H and the medium-size neurofilament subunit NF-M. Dephosphorylation abolishes the binding of MAbs TC4 and TC15 to Torpedo cholinergic NF-H, partially reduces that of MAb TC21 and has no effect on the binding of MAb TC8. This suggests that the antigenic sites specific to Torpedo cholinergic NF-H contain phosphorylated as well as non phosphorylated epitopes. All the MAbs cross-react with rat brain NF-H.

Anti-neuronal antibodies similar to those found in Alzheimer's disease induce memory dysfunction in rats

Although the etiology and pathogenesis of the cholinergic degeneration in Alzheimer's disease are not known, several reports implicate immunological mechanisms. Recently we have shown that sera of Alzheimer's disease patients contain antibodies which bind specifically to the heavy molecular weight neurofilament protein of Torpedo cholinergic neurons. In the present study we investigated the possibility that such antibodies play a role in neuronal degeneration by examining the behavioral and cellular effects of immunizing rats with the heavy neurofilament protein of Torpedo cholinergic neurons. The immunized rats developed antibodies which were specific to the heavy neurofilament protein of Torpedo cholinergic neurons and which cross-reacted with rat brain neurofilaments. Immunohistochemical studies revealed the accumulation of antibodies in the perikarya and neurites of neurons in the septum and hippocampus of the cholinergic neurofilament immunized rats and in white matter tracts in their forebrains. No such staining was seen in adjuvant immunized control rats. Behavioral tests revealed that rats immunized with the heavy cholinergic neurofilament protein performed significantly worse than controls in a T-maze alternation test and that their performance deteriorated profoundly after the introduction of a 20-s delay in the paradigm, indicating a deficit in short term memory. In contrast, both groups performed similarly in a T-maze discrimination test, indicating that long term reference memory was not affected by immunization with the heavy cholinergic neurofilament protein. Further experiments revealed that the rats immunized with the heavy cholinergic neurofilament protein were also deficient in a reversal of choice paradigm in a position discrimination test.(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise does not modify spatial memory, brain autoimmunity, or antibody response in aged F-344 rats

Old F-344 rats were given endurance training over a 10-week period on a motorized treadmill. This treatment resulted in substantial heart-to-body weight ratio increases, indicative of effective training. To determine whether endurance training might alter some of the known immune system and cognitive changes observed during aging, exercised old rats were compared to nonexercised old and young controls on three variables: in vivo antigen-specific immune activity, brain-reactive antibody formation, and spatial memory. The exercise training did not influence any of these measures in the old rats. Both groups of old rats showed poorer antibody response to a specific antigen, more brain-reactive antibody formation, and poorer spatial memory than the young controls. There was, however, a significant relationship between brain-reactive antibody formation and spatial memory performance, regardless of training condition.

Brain specific autoantibodies in murine models of systemic lupus erythematosus

Autoantibodies which bind to integral membrane proteins of brain were tested for their ability to bind to cross-reactive antigens on non-neural tissue. Both brain specific autoantibodies and antibodies which bind to cross-reactive antigens were found. There were two types of brain reactive autoantibodies which could not be adsorbed by non-neural tissue. One type was adsorbable by crude cell membrane preparations of brain. The second type was reactive against integral membrane proteins of brain, but not adsorbable by any of the crude membrane preparations tested. Autoantibodies of the first type reacted against integral membrane proteins with apparent molecular weights of 75, 70, 62, 50, 27, 24 and 20 kDa, as determined by gel electrophoresis and immunoblotting. As in previous studies, a diversity of brain reactive autoantibodies were found. The greatest numbers and strongest banding patterns were seen in the autoimmune strains of mice. The non-autoimmune strain displayed these autoantibodies at much lower levels. These results are the first to find brain specific autoantibodies, from autoimmune mice, against integral brain membrane antigens. The data support the idea that there is a sub-population of brain reactive autoantibodies which are involved in the pathogenesis of neuropsychiatric manifestations in immunologic disorders, particularly systemic lupus erythematosus.

Animal models of age-related dementia: neurobehavioral dysfunctions in autoimmune mice

The development of strategies for treatment of Alzheimer's disease and other age-associated dementias is an important goal of research in the neurosciences. It is suggested that advances in understanding of the etiology of those disorders would provide the most obvious avenues to development of preventative treatments. Research findings from both clinical investigations and studies of animal models are presented which suggest a neuroimmunologic component in age-associated dementia. Clinical studies suggest an association between dementia and brain-reactive autoantibodies in subsets of patients with Alzheimer's disease. Studies of mice suggest that: 1) when compared with normal genotypes, mutant mice with accelerated autoimmunity show learning and memory impairments at earlier chronological ages; 2) the learning and memory deficits of autoimmune and normal mice are qualitatively similar; 3) the behavioral deficits of normal aged and autoimmune mice are sensitive to similar pharmacologic interventions. Overall, these findings suggest that intervention strategies targeting the immune system might be useful in the treatment or prevention of aging-associated dementia. Autoimmune mice would be useful as models for the development and testing of such immune-based interventions.

Flumazenil improves active avoidance performance in aging NZB/BlNJ and C57BL/6NNia mice

C57BL/6NNia and autoimmune NZB/BlNJ mice aged 12-14 months were tested for acquisition and retention of an active avoidance response following vehicle or flumazenil (40 mg/kg), a benzodiazepine antagonist. Acquisition and retention performance was improved in flumazenil-treated mice when compared with vehicle-treated mice, although the degree of improvement varied with the level of performance in vehicle-treated mice of each strain. The NZB/BlNJ mice, which generally performed more poorly than the C57BL/6NNia mice, showed the greater improvements following flumazenil. These results suggest that antagonism of benzodiazepine receptors leads to improved learning and/or memory performance in mice with spontaneous age-associated deficits.

Cholinergic modulation of aged-like retention deficits in young autoimmune mice

Separate age groups of autoimmune NZB/BINJ and non-autoimmune C57BL/BNNia mice were compared for habituation of locomotor activity and its retention over four separate testing sessions spaced at 24-hr intervals. A decline in locomotion (distance in cm) or in the time spent in the center zone as a function of sessions was taken to indicate retention for habituation to stimuli within the test apparatus. The time spent in the center zone decreased as a function of sessions in young and mature C57BL/6NNia mice but failed to show reliable between-session decreases in old (24-26-months) C57BL/6NNia mice. When compared with the old C57BL/6NNia mice, young NZB/BINJ mice showed similar impairments. Habituation of locomotion was present in all age groups of C57BL/6NNia mice, but absent in NZB/BINJ mice regardless of age. The retention impairments of 2-4 month old NZB/BINJ mice were attenuated when i.p. injections of 0.04-0.16 mg physostigmine/kg were given just following each habituation session. The effectiveness of physostigmine was substantially reduced when injections were delayed by 20 min or longer following each habituation session. The time-dependent reversal of the aged-like retention deficits by the cholinesterase inhibitor, physostigmine, suggests that cholinergic modulation of memory storage processes may be impaired in NZB/BINJ mice.

Autoimmunity and age-associated cognitive decline

It is suggested that the immune system may play a role in the etiology of age-associated cognitive decline and/or Alzheimer's disease. The relationship between brain-reactive antibodies (BRA) and age-associated cognitive dysfunction is reviewed and discussed. A parallel relationship between BRA increases with age and decline of avoidance learning capacity is described in mouse models. Transfer of immunity from old to young mice was found to accelerate both age-related formation of brain-reactive antibodies and age-related decline of avoidance learning capacity. Short-lived mouse genotypes with accelerated autoimmunity were found to show accelerated age-related declines in their ability to acquire an avoidance response when compared with nonautoimmune mice. Overall, these findings suggest that the immune system could be an important target for development of intervention strategies aimed at extending the intellectually competent period of life. Mice in which autoimmunity is accelerated may be useful as models for the development of such interventions.