Almost 2% of the population of western industrialized countries are affected by Alzheimer's disease (AD). Nevertheless the pathogenetic process leading to this neurodegenerative disease is widely unknown. Thus, we focus on novel pathophysiological aspects of AD. We hypothesize that AD patients reveal increased levels of peripheral blood mononuclear cells (PBMCs) expressing proinflammatory (COX-2, TNF-alpha, CD40), proapoptotic (PARP-1), adhesion-relevant (CD38) or AD associated (C99, BACE1, Presenilin-1) proteins as well as elevated proinflammatory biochemical plasma parameters. Therefore, PBMCs of AD patients and age-matched control subjects were studied by two color fluorescence-activated cell sorter (FACS) analysis. Furthermore, concentration of plasma oxidized low-density lipoprotein (oxLDL) and TNF-alpha were measured by enzyme-linked immunosorbent assay (ELISA). We found a significantly increased percentage of TNF-alpha, COX-2, PARP-1, CD38, C99 or presenilin-1 positive PBMCs in AD patients compared with healthy subjects. FACS analyses revealed that the percentage of C99 or presenilin-1 positive PBMCs, which also express TNF-alpha, COX-2, PARP-1 or CD38 is also increased in AD patients. Additionally, AD patients had significantly increased plasma oxLDL and TNF-alpha levels. Furthermore, we found positive correlations between plasma oxLDL or TNF-alpha concentrations and the percentage of TNFalpha+, COX-2+ or PARP-1+, as well as PS-1+, C99+ or BACE+ PBMCs. Our findings suggest that immunocytological investigations, based on immunophenotyping of AD relevant proteins combined with measurement of proinflammatory, proapoptotic and adhesion-relevant proteins in PBMCs may provide more insight into the pathophysiology of AD.