Oligoclonal immunoglobulin bands in cerebrospinal fluid of patients with Alzheimer's disease and vascular dementia

We examined serum and cerebrospinal fluid (CSF) of 16 patients with Alzheimer's disease (AD), 28 patients with vascular dementia (VD), their age-matched controls and multiple sclerosis (MS) patients in order to evaluate the humoral immune response within the central nervous system both quantitatively and qualitatively. Intra-blood-brain barrier (BBB) protein synthesis was calculated by CSF IgG index. The presence of oligoclonal banding (OCB) was investigated with agarose isoelectric focusing (IEF) followed by immunoblotting with antihuman IgG. No patient with AD and only 4 patients with VD had slightly elevated IgG indexes, and no statistically significant differences in the indexes were found between the two groups. No bands were found in the CSF of AD patients but 3 VD patients had OCB in both serum and CSF. One VD patient had bands in serum but no bands in CSF. No kappa or lambda free light chains were found in those demented patients with demonstrable bands in the CSF and serum. No OCB were found in control sera and CSF. For comparison, the majority of patients with MS had OCB in CSF. Thus, no consistent increase of intrathecal protein synthesis was found in patients with AD and VD. Methodological differences explain at least part of the conflicting results published earlier.