Albumin and immunoglobulin in plasma and cerebrospinal fluid, and blood-cerebrospinal fluid barrier function in patients with dementia of Alzheimer type and multi-infarct dementia.

Plasma and cerebrospinal fluid (CSF) from 20 patients with Alzheimer's dementia or senile dementia of Alzheimer type (AD/SDAT), 23 with multi-infarct dementia (MID) and 16 controls were assayed for their content of immunoglobulins (Ig) and albumin (Alb). The concentrations of IgG and Alb were used to analyze the blood-CSF barrier function in the respective group. MID patients had significantly (P less than 0.001) elevated plasma IgG levels compared to controls and AD/SDAT patients. CSF concentration of Alb was significantly higher in MID (P less than 0.01) and AD/SDAT (P less than 0.05) patients compared to the controls. Concentration of CSF IgG was significantly (P less than 0.05) lower in AD/SDAT patients compared to the MID patients; no significant differences were found when CSF concentrations of IgG of demented patients were compared to controls. These findings may indicate a blood-CSF barrier dysfunction especially in cases with MID with significantly (P less than 0.001) elevated values of transudation. Also these findings indicate a non-specific and/or specific binding of IgG in CNS tissue and/or vessel walls in both forms of dementia on the basis of low IgG ratios compared to proportionally higher Alb ratios. There were no signs of local synthesis of IgG in CNS in either group of demented patients.