Neopterin levels and immune activation in the blood of children with Down's syndrome

Patients with AD often show altered levels of some immune molecules in their peripheral blood which correlate with cognitive impairment. Downs' syndrome (DS) subjects are at high risk of developing Alzheimer's disease (AD). Here we studied immune molecules, such as interleukin-6 (IL-6), C reactive protein (CRP) and neopterin, in the blood of non demented children with DS to investigate whether altered peripheral immune phenotype could be present in this subjects without dementia, many years before the presentation of clinical signs of cognitive deterioration. Plasma levels of neopterin and IL-6 were measured by commercially available ELISA kits, whereas plasma CRP concentration was evaluated by nephelometric immunoassay technique. We studied a group of 40 patients with DS, 20 healthy controls and 100 patients with AD. Plasma levels of IL-6 and CRP were significantly higher in DS than in control children. The increase of IL-6 and CRP from DS children was similar to that found in elderly patients with clinical AD. In the present research we have also studied blood levels of neopterin which were in the normal range either in DS or control. Increased or normal levels of this metabolite have been found in the blood of AD patients. However, increased blood neopterin was likely to be only elevated in patients with advanced clinical stage of AD. Peripheral altered immune phenotype in healthy young subjects with DS might be an early sign of CNS alterations leading many years later to cognitive deterioration and dementia.