It has been reported that patients with Alzheimer's disease (AD) exhibit an overproduction of interleukin-1 (IL-1) in the cerebrospinal fluid and brain tissue. Since IL-1 appears to promote the expression of the beta-amyloid precursor protein (APP) gene, we have investigated the concentrations of serum IL-1 alpha and IL-1 beta and AD and multi-infarct dementia (MID) in order to evaluate whether IL-1 acts as a peripheral activating factor on cerebrovascular endothelial cells stimulating APP production. Serum IL-1 alpha levels did not differ significantly between healthy elderly subjects (110.7 +/- 23.3 pg/ml), early-onset AD (EOAD; 112.5 +/- 23.3 pg/ml), late-onset AD (LOAD; 89.2 +/- 17.6 pg/ml) or MID (116.8 +/- 50.4 pg/ml) patients. Serum IL-1 beta levels were also similar in controls (223.7 +/- 55.7 pg/ml), EOAD (223.1 +/- 79.5 pg/ml), LOAD (212.5 +/- 58.9 pg/ml) and MID (199.4 +/- 29.0 pg/ml). In LOAD a negative correlation between mental performance (MMS score), IL-1 alpha (r = -0.7728; p less than 0.0715) and IL-1 beta (r = -0.9214; p less than 0.0011) was observed. These results indicate that serum IL-1 levels are not altered in AD and MID; therefore, it is unlikely that blood-borne IL-1 influences APP production in the central nervous system (CNS). In conclusion, the neuroimmune dysfunction present in AD seems to be mainly concentrated in the CNS, with only minor immune alterations at the peripheral level.