A study of beta protein precursor using antiserum against a synthetic peptide (1-28).

We studied the presence of the beta protein precursor by immunocytochemistry and Western blot analysis using antiserum against a synthetic beta peptide (1-28). The brains of 4 patients with dementia of the Alzheimer type (DAT) were examined immunocytochemically. Frozen and formic acid pretreated paraffin sections were best for beta protein immunostaining. Both the senile plaque amyloid and cerebrovascular amyloid were immunostained with 28K1. In addition to primitive and typical plaques, amorphous granular or fibrous deposits of amyloid were observed in high numbers in various areas of the DAT brains. However, the beta protein precursor, which was suggested to be present in neuronal cells by in situ hybridization, was not stained. Neurofibrillary tangles were not stained, either. Sera and cerebrospinal fluid (CSF) from 6 patients with DAT were examined using Western blot analysis. A 52-kD band was detected with 28K1 in DAT patients as well as in normal controls. Further investigation revealed the 52-kD band to be the heavy chain of IgG. The staining pattern using the beta protein immunostain was quite different from the IgG immunostain. In this study there was no detection of the beta protein precursor, with the use of immunocytochemistry and Western blot analysis. Thus, further investigations are necessary using the antiserum against other residues of the beta protein precursor or using specimens without IgG.