An immunologic assessment of brain-associated IgG in senile cerebral amyloidosis

Frontal and occipital lobes were taken within four hours of death from four senile patients (77-94 years) and frozen at -70 degrees C. After thawing at room temperature, gray and white matter were separated and subjected to sequential elution at pH 7.4 and pH 2.5. The eluates were processed for isoelectric focusing on 2.5% polyacrylamide gels and stained with silver nitrate; immunoblotting was done on agarose gels and stained by immunoperoxidase for IgG and light chains. Quantitation of the amount of IgG present in neutral and acidic eluates was performed by immunonephelometry and ELISA. Only the neutral eluates contained significant amounts of IgG, which were usually polyclonal. These data indicate that IgG associated with senile cerebral amyloid are not bound to any brain or vascular component and the data do not support the occurrence of an intraparenchymal immune response.