Since the BBB seems to be compromised in AD patients, we also sought to detect antibodies against BBB components such as S100B, AQP4, claudin-5, and GFAP in their blood, and to determine if they were immunoreactive with monoclonal AβP-42 antibody, as this could contribute to BBB breakdown and AD neuropathology. This evidence concerns the gene AQP4 and Alzheimer disease.