To clarify the role of apolipoprotein E (apoE) in the pathophysiology of Alzheimer's disease (AD), we used an RT-PCR method to investigate apoE and glial fibrillary acidic protein (GFAP) mRNA expression in the brain. ApoE mRNA was significantly more abundant in AD (0.379 +/- 0.191, mean +/- SD) than in control (0.125 +/- 0.073, p < 0.05) brain tissue, but in AD it was decreased in relation to the apoE-epsilon 4 gene dosage. The GFAP mRNA content also was greater in AD (5.96 +/- 2.94) than in control (3.80 +/- 2.78) tissue, and in AD showed an increase relative to the apoE-epsilon 4 gene dosage. AD patients who had long survival times showed high expression of apoE and low expression of GFAP. These results suggest that apoE suppresses the progression of AD, including gliosis, in the brain.