Immune Reactions in Aging Brain and Senile Dementia

[Premature immunosenescence: a pathogenetic factor in Alzheimer's disease?]

While the familial form of Alzheimer's disease (AD) is known to be entirely inherited, the etiopathogenesis of the most common late-onset form of Alzheimer's disease still remains unresolved. Among various factors, aging seems to be one of the most prominent risk factors. Moreover, a large body of evidence points to the contribution of immunological alterations in AD. The involvement of inflammatory factors in the etiopathology has been widely discussed. Moreover, an impairment of certain immune responses in AD has been observed. Presumably, premature immunosenescence may lead to inadequate immune reactions. Against this background, the development of different immunotherapeutic strategies seems to be a promising challenge for future research.

Peripheral blood lymphocyte subset distribution and function in patients with Alzheimer's disease and other dementias

BACKGROUND

Until recently, new data on immune aspects of Alzheimer's disease (AD) have suggested that some facets of AD pathogenesis may be immune related. However, the effects of dementia itself on immune function have not been considered.

AIM

To compare the distribution of peripheral blood lymphocyte subsets and their function in patients with AD and other dementias.

METHODS

Peripheral blood lymphocyte numbers, T cell subset distribution, proliferative responses to mitogens and suppressor cell assay were studied in a well characterised group of patients with AD, and compared to patients with other forms of dementia. Age and sex matched elderly controls were screened to exclude dementia, and young controls were medical, paramedical and laboratory staff. Analysis of variance (ANOVA) and student's test were used for statistical analysis.

RESULTS

The CD8+ lymphocyte population was reduced in AD and in other forms of dementia, when compared with non-demented elderly and young controls. Concanavalin A induced lymphocyte transformation was reduced in all dementia groups and in elderly compared with young controls. The changes in T cell numbers and function were not specific for Alzheimer's disease, but were found also in other forms of dementia.