P1–265: Lymphocyte subset patterns in Alzheimer's disease (AD) patients

Although AD is considered a degenerative disorder, changes involving main functions of the immune system have been observed. To investigate the signs of inflammatory processes in AD, peripheral blood mononuclear cells from a total of 84 AD patients were immunophenotyped by means of double–color flow cytometric analysis, and the results were compared with those for age–matched healthy controls. The cell subsets quantified included total T cells (CD3), B cells (HLA–DR), NK cells (CD56), CD4 and CD8 T cells, cytotoxic (CD28) and suppressor precursor (CD28) CD8 T cells, CD45RA and CD45RO T cells (CD4 and CD8), and CD7 T cells. Analysis of AD patients' peripheral blood revealed essentially normal levels of total T, B and NK cells. In agreement with results obtained by other groups, it was found that AD patients had an increased CD4/CD8 ratio, due to both a decrease in CD8 T cells and to an increase of CD4 T cells. AD patients were found to have a significantly decreased level of suppressor precursor (CD28) CD8 T cells and normal levels of cytotoxic (CD28) CD8 T cells compared with that of controls. These data indicate that AD patients do not have a general decrease in CD8 T cells but that they have a specific decrease in the suppressor precursor subset only and normal levels of cytotoxic CD8 T cells. AD patients also had a significant increase in memory (CD45RO) T cells and displayed a trend towards a decrease in naı̈ve (CD45RA) T cells in the peripheral blood. The observed dysfunction in immune peripheral cell subpopulations point to a reduction of suppressor cell function in AD patients.