Serum markers of monocyte/macrophage activation in patients with Alzheimer's disease and other types of dementia

OBJECTIVES: Recently an increase in serum neopterin has been described in patients with Alzheimer's disease (AD) that would be associated with an increased cell-mediated immune response. We have studied the serum levels of several monocyte/macrophage activation markers in patients with AD and other types of dementia. DESIGN AND METHODS: Serum neopterin concentration, and the chitotriosidase (ChT), angiotensin-converting enzyme (ACE) and adenosine deaminase (ADA) activities were determined in 30 patients with AD, in 19 patients with other types of dementia, and in 24 nonaffected controls. RESULTS: Neopterin concentration was significantly higher in the subgroup of AD patients with a global deterioration scale higher than in the other patients with AD, patients with other types of dementia and in the control group (p < 0.005). However, the activities of ChT, ACE and ADA, despite having a significant correlation with neopterin, did not present any statistically significant differences among the groups studied. CONCLUSION: In the most advanced clinical stages of AD, as well as an increased immune activation, an impaired formation of tetrahydrobiopterin from dehydroneopterin triphosphate would contribute to an increase in the serum concentration of neopterin. However, the large overlap between the groups, limits the possible clinical value of serum neopterin in AD patients.