Immune manipulations and brain-reactive antibody formation in aging mice

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.

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.

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.

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.

Age differences in acquisition and retention of one-way avoidance learning in C57BL/6NNia and autoimmune mice

Acquisition and 48-h retention of a step-up active avoidance response were studied in separate age groups of C57BL/6NNia mice (aged 1.5, 3.5, 6, 12, or 26 months) and five strains of genetically autoimmune mice differing in life span. The C57BL/6NNia mice showed no change in ability to acquire the avoidance response between 1.5 and 3.5 months, but showed a steady decline in that ability thereafter. Mouse strains with early-onset autoimmune disorder (NZB/B1NJ, MRL/MpJ-lpr, and BXSB/MpJ) showed declines in acquisition capability between 1.5 and 3.5 months of age, whereas mouse strains with mild, late-onset autoimmune disorder (MRL/MpJ- + and NZBWF1/J) showed stable or improved acquisition during that period. Both the C57BL/6NNia and NZB/B1NJ mice showed age-dependent declines in 48-h retention performance by 12 months of age. These findings suggested that while 48-h retention performance deficits were most related to chronological age, avoidance acquisition deficits were related to development of autoimmunity.